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3., LIBRAR Y
Michigan State

University

This is to certify that the
thesis entitled

Trace Eiement Distribution in the Native
Copper from the Centennial Number 3 Mine,
Houghton County, Michigan

presented by

Michaei Lee Price

has been accepted towards fulfillment
of the requirements for

Master's Geoiogy

degree in

MAMM »

\ Major professor

 

 

Date 11/16/77

0-7639

 

 

 

 

TRACE ELEMENT DISTRIBUTION
IN THE NATIVE COPPER FROM THE CENTENNIAL
NUMBER 3 MINE. HOUGHTON COUNTY, MICHIGAN

By

Michael Lee Price

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geology

1977

ABSTRACT
TRACE ELEMENT DISTRIBUTION

IN THE NATIVE COPPER FROM THE CENTENNIAL
NUMBER 3 MINE, HOUGHTON COUNTY, MICHIGAN

By

Michael Lee Price

Thirty-three samples were collected within the Calumet and Hecla
Conglomerate in the Centennial #3 Mine.

Atomic absorption, neutron activation analysis and flame emission spec-
trometry were used and of the nineteen elements examined; Mg, Fe, Mn, Ca,
Na, Zn, K and As were the only elements detected. The electron microprobe
was used to determine the distribution of Ag, Fe, and Mg in native copper
grains. Scans across several copper grains show that there is no zoning
of at least Ag, Fe and Mg in the copper grains.

Sampling size and distribution hindered the reliability of the first
two types of elemental trend comparisons: comparison of the different
elemental concentrations for each level and trend surface maps for pos-
sible regional trends. The third type of trend examined was the com-
parison of elemental and mineralogical trends within one permeable channel,
which has the greatest concentration of copper, has the highest concen-

tration of trace elements in the native copper.

ACKNOWLEDGEMENTS

The author is deeply indebted to the Homestake Mining Company for
allowing this study to be done. Particular thanks goes to Ray Wilcox
and Ross Grunwald, geologist at Homestake.

Without the help and encouragement of the following people, the study
would not have been possible. Special thanks to:

Dr. John T. Wilband, thesis committee chairman, for his advice and assis-
tance with the manuscript and guidance throughout the study.

Dr. Thomas A. Vogel and Dr. James Wm. Trow, committee members, for all
their advice.

Dr. A. Timnick for his assistance with the electrolysis.

Mr. V. E. Shull for his assistance with the microprobe.

Mrs. Ellen Lynam and Mrs. Virginia Wharton for typing this manuscript.

Mr. Art Douglas for drafting of the figures.

ii

ABSTRACT

Thirty-three samples were collected along and updip within the
Calumet and Hecla Conglomerate in the Centennial #3 Mine, Houghton
County, Michigan. The intent of this study was to examine trace elements
from native copper samples to determine if they could be used to monitor
changes of the ore solution.

The trace elements redistribution in the Portage Lake Lava Series
is ultimately related to the metamorphic process it has undergone. The
following elements - Fe, Mg, Na, Mn, Sr, K, Ba, Ca, Ni, As, Sb, Ti, Cs, Zn,
Pb, Cd, Bi, Cr, and Co - were in the system before metamorphism and were
selected to determine possible redistribution within the system. Atomic
absorption, neutron activation analysis and flame emission spectrometry
were used and of the above elements; Mg, Fe, Mn, Ca, Na, Zn, K, and As
were the only elements detected. The electron microprobe was used to
determine the distribution of Ag, Fe, and Hg in native copper grains for
samples from the first, thirty-third and thirty-fourth levels. Semi-
quantitative analysis indicate Ag is the most enriched and Mg the least
enriched. These results are in agreement with quantitative atomic absorp-
tion data for Fe and Mg. Scans across several copper grains show that
there is no zoning of at least Ag, Fe, and Mg in the copper grains.

Three different types of elemental trends were examined. Sample
size and distribution was one of the major factors in determining possible
trends. Sampling size and distribution hindered the reliability of the
first two types of trend comparisons: comparison of the different elemental
concentrations for each level and trend surface maps for possible

regional trends. The third type of trend examined was the comparison of

elemental and mineralogical trends within one permeable channel. This
third trend comparison shows a pattern where the center of the permeable
channel, which has the greatest concentration of copper, has the highest
concentration of trace elements in the native copper.

This work is in agreement with Jolly (1974) for the mobilization
of Zn and the immobility of Ni during the metamorphic process the Lava

Series underwent.

 

 

 

 

Table of Contents

Introduction
Purpose
Previous Work
General Geology
Geology of the Centennial Number 3 Mine
Origin of Copper in Lava Series
Petrology and Alteration
Sampling and Analytical Procedures
Sample Locations
Analytical Work
Statistical Methods
Description of Elemental Trends
Summary Conclusion
Bibliography
Appendix A - Sample Descriptions and Locations
Appendix B — Equipment Setup and Correlation Coefficients for

Working Cure Data

\l-b-h

to

11
13
22
22
22
29
31
61
63
66

106

Table

01

List of Tables

Keweenawan Stratigraphic Column on Keweenaw Peninsula

Calculation of Bulk Comparison of the Altered Basalts
and Comparison with Relatively Unaltered Basalts

Minor Elements in the Lava Series

Elemental Abundance (PPM) for Each Sample

Statistical Summary of Table 4

Pearson Correlation Between Single Variables

Pearson Correlation Between Grouped Variables
Averages of Each Element for Each Drift Level (PPM)
Relative Ranking of Element Abundance for Each Sample

Percent Minerals in Each Sample

vi

20
21
26
28
30
30
32
58
59

 

 

 

Figure

10
11
12
13
14
15
l6
17
l8
19
20

Location Map

List of Figures

Horizontal Plan Showing the Centennial Number 3 Mine

Photomicrograph of "Patchy Hematite" in Plagioclase

Phenocrysts

Photomicrograph of Bleached Pebble

Photomicrograph of Type I Halo Around Edges of

Hematite Grain

Longitudinal Section in Plane of Calumet Conglomerate
Lode Showing Centennial Number 3-6 Mine Workings

Trend Map - MG
Contour Map of
Residual Map -
Trend Map - Fe
Contour Map of
Residual Map -
Trend Map - Mn
Contour Map of
Residual Map -
Trend Map - Ca
Contour Map of
Residual Map -
Trend Map - Na

Contour Map of

Original Data

MG

Original Data

Fe

Original Data

Mn

Original Data
Ca

Original Data

vii

MG

Fe

Mn

Ca

Na

10

15
l6

T7

23
33
34
35
36
37
38
39
4o
41
42
43
44
45
46

L;

V

I|,'J

Figure
2l
22
23
24
25
26
27
28
29
3O
3l
32
33

34

35
36

37

38
39

List of Figures (Cont'd.)

Residual Map - Na

Trend Map - Zn

Contour Map of Original Data - Zn
Residual Map - Zn

Trend Map - K

Contour Map of Original Data - K
Residual Map - K

Trend Map — As

Contour Map of Original Data - As
Residual Map - As

Photomicrograph of Silver Copper Intergrowth
Photomicrograph of Trap Rock

Photomicrograph of Calcite Being Replaced by
Epidote and Dendritic Copper Included in the Calcite

Photomicrograph of Secondary Overgrowth
on a Plagioclase Phenocryst

Photomicrograph of Clinozoisite

Photomicrograph of Quartz Feldspar Porphyry Pebble,
Epidote and Copper

Photomicrograph of Partial Recrystallization of
Quartz Phenocryst

Photomicrograph of Pennenite

Photomicrograph of a Pebble Being Replaced by Epidote

viii

47
48
49
50
51
52
53
54
55
55
68
75

85

86
88

91

97
99
102

O
A.

r

I”)

INTRODUCTION

 

The Centennial #3 Mine, previously owned and operated by the
Calumet and Hecla Mining Company, was in operation for nearly a
century (Fig. 1). The mine was closed in 1968, due to labor disputes,
and most of the mine except the #3 shaft and workings were allowed to
fill with water.

The ore is contained in the Calumet and Hecla Conglomerate which
averages over ten feet in thickness in the Calumet area. Rather rec-
ently, Weege and Pollock (1972) discovered that the conglomerate in the
Centennial #3 Mine consists of two lithologically distinct bodies, a
main channel and a tributary. Both bodies carry native copper, but
the extent of mineralization in the Centennial workings remains to be
determined. One of the reasons for closing the mine was an outdated
mining-ore processing system. Homestake Copper Company and American
Copper and Nickel Company hold a lease on the mineral rights to the pro-
perty, they dewatered the old workings, and have sunk an exploratory
shaft. The geological aspects of the deposits, along with other fac-
tors, are being reviewed. In past practice, close estimation of ore
grades in the mine was not possible due to grade variability. Standard
methods such as drilling defy correct ore grade estimation since a hole
may miss a high grade pocket and encounter a barren zone within inches
of the high grade zone. This investigation is in part an extension of
the work now actively being carried out by Homestake geologists in their
on going investigation of “ore controls".

Of the many investigations on the distribution and mechanism of

deposition of native copper in the Keweenaw Peninsula few have been

 

 

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devoted to the deposition of copper within the conglomerate horizon.

The reason why some conglomerates serve as copper "getters" has only

been conjectured. Since pebbles, and even cobble sized fragments are
replaced by native copper in some areas, or the matrix is totally replaced
by native copper, these ore rich zones fit an unspecified criteria for
copper deposition. Other zones, although barren of copper, are clearly
altered or bleached. It is not clear whether the same solution that de-
posited the replacing copper was responsible for the wall rock alteration
because altered zones are not always associated with native copper nor

is native copper always associated with an apparent alteration other

than replacement.

In general, the interflow conglomerates within the lava pile do not
form outcrop ridges. Where they form outcrop ridges they are invariably
nonmineralized. It can be tacitly assumed that local postdepositional
changes rendered the conglomerate impermeable to the epigenetic copper
bearing solutions. This fact has led some to conclude that the ore channels
must be controlled by the permeability of the host which is a function of
granularity and ultimately of the environment of deposition. Stated other-
wise, lithologic variations within the conglomerate serve as barriers or
channel ways for the upward migrating ore solution.

In general, the foregoing paragraphs aptly apply to the Calumet
and Hecla Conglomerate. Specifically, several alteration patterns, some
of which are clearly related to native copper mineralization, have been
delimited. One such easily recognizable pattern occurs in even-grained
sand where a central zone of epidotization is replaced by a native copper
replacement zone which in turn is succeeded by a calcite rich cement zone.
A common feature of this type of alteration is the pervasive bleaching

which imparts a salmon pink color to the edges (with differing degrees

of penetration) of the originally dark purple or maroon felsite pebbles.
In some localities the direction of solution migration can be recognized
by the fact that only the leading edges of rounded pebbles are bleached

to form an incomplete, cuspate rind around the borders.

PURPOSE

The purpose of this study is to examine trace elements from native
copper samples along and updip in the Centennial #3 Mine to determine if
they can be used to monitor changes of the ore solution. This assumes
that trace elements present in the native copper represent "residual
characteristics" of the solution from which the copper crystallized.
These "residual characteristics" will be compared to the alteration pat-
terns, lithologic variations and other variables which were observed at
the selected sample sites.

The model presently favored by mine geologists for controlling ore
deposition is related to permeability of conglomerate horizons, which is
in part controlled by the presence of stream channels within the conglo-
merate. Most samples have been collected within such a channel system,
the geometry of which is discussed in a following section.

The trace element redistribution in the Portage Lake Lava Series
is ultimately related to the metamorphic process it has undergone. The
following elements - Fe, Mg, Zn, Na, Mn, Sr, K, Ba, Ca, Ni, As, Sb, Ti,
Cr, Pb, Cd, Bi, Co and Cs - were in the system before metamorphism and

were selected to determine possible redistribution within the system.

PREVIOUS WORK
This area has been extensively studied since mining began in 1845.

The most comprehensive work on the Michigan copper deposits is by Butler

\ .
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f .

and Burbank (1929). In their publication nearly 500 references are cited;
since that time some 250 articles concerning the Keweenaw deposits have
been published (White, 1968).

Butler and Burbank's USGS Professional Paper 144 summarizes all of
the work done on the area up to that time. It includes the geology of
the area, production records of the various mines, and a study of the
ore deposits themselves.

In 1929, T.M. Broderick wrote on the zoning of the deposits of the
district. His work dealt mainly with the arsenic content of the copper
minerals that are found in the mines in the north-eastern end of the
range. In 1935, Broderick wrote on the vertical differentiation of some
flows and suggested that a horizontal study of a flow over a long dis-
tance be made to look for possible differences along strike (p. 557).

Stoiber and Davidson (1959) completed a study on mineral zoning in
the Lava Series in which they concluded that native copper is spatially
associated with the outer margins of the regional quartz zone beyond the
limits of pumpellytization (p. 1457).

Jolly and Smith (1972) have chemically characterized a basal de-
hydrated zone and a hydration zone associated with the appearance of
epidote. They note that rocks in the chlorite and pumpellyite met-
adomains formed sinks for fluids. Jolly (1973) believes that fluids
evolved by dehydration contained up to 1780 ppm Cu. He proposed that
metamorphic hydration of volcanic piles could be used as an indicator of
mineralization. Jolly (1974) did a study on the behavior of Cu, Zn and
Ni during prehnite-pumpellyite rank metamorphism in the Lava Series in
which he concluded that both copper and zinc were mobilized during
prehnite-pumpellyite facies metamorphism, and nickel was not appreciably

affected by the metamorphic process except where there was dilution by

void-filling secondary minerals. Livnat (1976) has demonstrated from
oxygen isotopes data that the basalt in the copper country underwent
some hydration and extensive exchange with low-temperature meteroric
waters prior to mineralization. He then concluded, in agreement with
Jolly, that the water responsible for mineralization is non-magmatic.

Weege and Pollock (1972) describe the geology at the Centennial #3
Mine and they discovered that the conglomerate consists of two lith-
ologically distinct bodies, a main channel and a tributary.

J. M. Bell (1974) described the petrology of the conglomerate and

its bearing on in situ leaching.

GENERAL GEOLOGY

 

The Michigan native copper district lies wholly within the Portage
Lake Lava Series which is a northeast trending, northwest dipping series
of 9,000 to 15,000 feet of numerous altered basalt flows and interflow
conglomerates of middle Keweenawan age (Table 1). These rocks outcrop
at least 160 miles in length and near Calumet are in the order of 10,000
feet thick. The lavas emanating from the center of the basin are typical
olivine tholeiite flood basalts (Jolly and Smith, 1972), in which over
200 individual flows have been counted. During intervals in which there
was no igneous activity, conglomerates were deposited from a south-
easterly source area (Hamblin and Horner, 1961). The interflow con-
glomerates are principally comprised of felsitic material, with some
amygdaloidal basaltic material. This rock sequence dips between 25 to
70 degrees north toward the axis of the Lake Superior basin, which was
formed at the same time as the extrusion of the Keweenawan lavas (White,
1960).

To the west of the exposed Portage Lake Lava Series are the Upper
Keweenawan rocks. Directly overlying the Portage Lake Lava Series is the
Copper Harbor Conglomerate. It thickens from 350 feet in the southwest
to 6,000 feet in the northeast. Recent work has shown that overlying
this unit is the Unnamed Formation. a series of mafic flows intercalated
with felsite flows (White, et. al, 1969). Above the Unnamed Formation
is the Nonesuch Shale, which contains the chalcocite ore at the White
Pine Mine. The uppermost member of this sequence is the Freda Sandstone.
Recent workers now assign the rocks of the Nonesuch Shale and the Freda
Sandstone to the Oronto group and consider them to be Upper Keweenawan

(White, 1972). To the east of the Portage Lake Lava Series and in fault

7.

Upper Precambrian

Table 1. Keweenawan stratigraphic column on Keweenaw Peninsula
(after Sprioff and Slaughter, 1961).

 

 

Freda

 

Nonesuch

 

Outer Conglomerate
Copper Harbor Lake Shore Traps
Great (Eagle River) Conglomerate

Upper Keweenawan

 

Hancock Conglomerate (No. 17)
Ashbed Lode
Pewabic West Conglomerate (No. 16)
Pewabic Lode
Portage The Greenstone Flow
Allouez Conglomerate (No. 15)
Houghton Conglomerate (No. 14)
Iroquois Amygdaloid
Calumet & Hecla Conglomerate (No.13)
Lake Calumet Amygdaloid
Osceola Amygdaloid
Kingston Conglomerate (No. 12)
Kearsarge Flow
National Sandstone
Lava olverine Sandstone (No. 9)

ld Colony Sandstone

cales Creek Flow

ratiot Flow

Isle Royal Lode
Series ohemia Conglomerate (No. 8)
Copper City Flow
t. Louis Conglomerate (No. 6)
Lac La Belle Conglomerate
Baltic Lode
Baltic Conglomerate (No. 3)

 

Middle Keweenaw

 

 

------------ Keweenaw Fault - - - - - - - - - - - - - - - -

 

9

contact is the Jacobsville Sandstone, which is also considered Upper Kew-
eenawan.

Minor intrusive rocks occur within the Michigan copper district.
These intrusives are mostly small rhyolite bodies, though there is one

mafic intrusive exposed in the area (White, 1968).

GEOLOGY OF THE CENTENNIAL NUMBER 3 MINE

Figure 2 is a horizontal plan showing the Centennial #3 Mine and a
portion of the old Calumet and Hecla workings. The heavy dashed line del-
ineates between the main channel and the tributary channels. The major
areas of copper mineralization, ore shoot A and B, are shown. Ore shoot A
is contained within the tributary channel, and ore shoot B occurs within
the main channel. The five foot thickness contour can be seen in the
diagram, and this is the approximate thickness of the tributary channel.
Regarding the form of the Calumet and Hecla Conglomerate, Weege and
Pollock (1972, p. 631) states:

“The Calumet and Hecla Conglomerate can be traced for

over 40 miles. For most of this length it is very thin,

ranging from an inch or less to a few feet in thickness, but

in the Calumet area it abruptly thickens and averages over 10

feet in thickness. The bed tends to consist of a group of

subparallel thicker and thinner lenticular streaks or chan-

nels that generally trend north. The bed as a whole also

tends to thicken with depth."

The tributary channel conglomerate at the Centennial #3 Mine trends
generally down dip until it nears the main channel conglomerate where
the trend turns more to the north (Weege and Pollock, 1972).

Quartz feldspar porphyry is the major type pebble in the Centen-

nial #3 Mine whereas the main channel conglomerate contains felsite

 

 

 

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Figure 2 (from Weege and Pollock, 1972)

11

and granophyric pebbles as well as quartz feldspar porphyry. Weege
and Pollock (1972 P. 632) state:

"The pebbles as a whole are larger and better rounded than
those of the Centennial No. 3-6 mine. These differences suggest
that the pebbles at the Centennial No. 3-6 were derived from a
relatively small source area of quartz feldspar porphyry that was
close to the site of deposition, and the pebbles of the main channel
conglomerate were, on the average, transported for a greater dis-
tance from a geologically more diverse source terrane."

A fractured amygdalodial flow top underlies the conglomerates.
Bell (1974 P. 10) states:

"This fractured portion of the flow t0p may be a meter or more
thick, and its fractures are filled by a shaley appearing material
composed of calcite and detrital hematite, ..... This shaley appear-
ing material also forms a thin layer (1 to 3 cm. thick) between the
fractured flow top and the conglomerate. In some places, the frag-
mented flow top has been erroded away and just the thin layer of
calcite and detrital hematite occurs. Due to the abundance of
hematite in the footwall, the color of the footwall is a grayish
red."

ORIGIN OF COPPER IN LAVA SERIES

 

There are two general hypotheses regarding the origin of the native
copper deposits. One relates the copper to hydrothermal solutions emanat-
ing from a magmatic source (Butler and Burbank, 1929: Broderick, 1929, 1935,
1946). The other, relates the deposits to processes that took place dur-
ing the diagenetic and metamorphic alteration of the lava pile (Jolly,
1972, 1974). One point to be brought out here is that the conglomerates
constitute a very small portion of the Portage Lake Lava Series, and the
chemical system under which the conglomerates became altered must have
been controlled to a large extent by the chemistry of the lavas.

Jolly (1974) proposes a model where the native copper has been leached
from dehydrated rocks in the lower part of the lava pile during metamorphic
dehydration and precipitated in hydrated rocks near the upper part as a
result of supersaturation of residual fluids. Jolly and Smith (1972) have

recognized three metamorphic zones, or metadomains: (1) the upper meta-

12

-domain characterized by the occurence of chlorite; (2) an intermediate
zone with an abundance of pumpellyite: (3) the lower zone with epidote.
The basalts show both a vertical and horizontal gradation from an albite
basalt to unaltered flow.

Metamorphic alteration took place largely in the more permeable
areas of the lava pile, such as the flow tops, breccias, scoriaceous
amygdaloids, conglomerates, and along faults and joints. In the less
permeable areas, and in thick flows, little metamorphic alteration is
present. Jolly compared the water content in the rocks and found that
the unaltered basalt has a water content intermediate between that of
the epidote and the prehnite-pumpellyite regions. He concludes that
the epidote region dehydrated and acted as the fluid source, while the
prehnite-pumpellyite domains hydrated and acted as solution sinks. Fur-
thermore, Jolly observed that there was less copper in the epidote met-
adomains (20 ppm Cu), and more in the unaltered basalts (70 ppm Cu). This
suggests that during hydration, the epidote metadomain lost 50 ppm Cu.

Jolly incorporates these observations to form his model to account
for the emplacement of native copper. The lava pile was dehydrated at
depth and as the fluid moved up dip, it became progressively enriched
in copper. The P02 in the zone of dehydration increased sufficiently
to oxidize the magnetite to hematite. In this process electrons are given
off and conducted by the metamorphic fluid to the zone of hydration,
where copper was reduced and deposited. The implication of the hypo-
thesis is that all native copper deposits occur in the zone of hydration.

Jolly along with the above observations found that zinc was leached
out of all metadomains in the lava pile and, presumably because 52 was
unavailable and reduction to Zn° was impossible, flushed out of the

rocks completely. The presence of Ago in close association with native

13

-c0pper (Stoiber and Davidson, 1959; White, 1968) and As0 alloyed with
Cu0 (Drier, 1954) suggests that both of these elements reacted to the
metamorphic environment in the same manner as copper. Jolly also ob-

served that nickel remained largely immobilized during the metamorphic

event.

PETROLOGY AND ALTERATION

 

Three different types of pebbles are present in the conglomerate:
felsite, granophyric and quartz feldspar porphyry. Felsite pebbles con-
sist of a very dense, fine-grained aggregate of quartz and feldspar. The
color of these pebbles are quite varied, but they are usually darker then
the granophyric and quartz feldspar porphyry. 0f the three pebble types,
felsite pebbles are the least bleached. The felsite pebbles in many
instances are fractured, and the fractures are filled with copper.

The felsite pebbles ranged from 0.5 to 4 mm. in size. Granophyric peb-
bles, are mostly small laths of feldspar with irregular intergrowth
patches of quartz. The intensity of the rimming is less than the quartz
feldspar porphyry pebbles but greater than the felsite pebbles. Bell
(1974, p. 16) states: "Of all of the pebble types, only the granophyre
pebbles tend to break around the rim, rather than through the pebbles“. The
granphyric pebbles ranged from 0.5 to 4 mm. in size. The quartz feldspar
porphyry has an equigranular groundmass of quartz and feldspar. Ground—
mass grains are small, and somewhat elongated grains. Feldspar pheno-
crysts are less abundant and more fractured than the quartz phenocrysts.
The feldspar phenocrysts at deeper levels in the mine are partially or

completely replaced by epidote. The feldspar phenocrysts also show

l4

“patchy" hematite, partial replacement of different zones in the feldspar
phenocrysts by hematite (Fig. 3). The tributary samples have quartz
feldspar porphyry pebbles ranging up to 20 mm. in size, and the main
channel has quartz feldspar porphyry pebbles at least 40 mm. in size.
Bleaching of the pebbles is due to the removal of hematite as the
rock pigment (Fig. 4). Previous workers have noted that bleaching is
spacially related to the occurrence of copper in the Calumet and Hecla
Conglomerate. In some localities the direction of solution migration
can be recognized by the fact that only the leading edges of rounded peb-
les are bleached to form an incomplete cuspate rind around the borders.
Primary minerals in the conglomerate matrix include detrital quartz,
feldspars and hematite; secondary minerals include copper, calcite, epi-
dote and chlorite. Samples were mainly taken from the bleached zones in
the conglomerate. In this zone quartz shows secondary overgrowth around
its edges, and ranges from 0.1 to 3.0 mm. in size. The detrital feldspar
grains show faint albite twinning and have a composition range of An34 to
An37. The feldspar grains in places are being replaced by calcite and
epidote. The feldspar grain size ranges from 0.1 to 3.5 mm. Detrital
hematite grains are scattered throughout the matrix and are less than
0.1 mm. in size. Grains of hematite included in the pebbles are gen-
erally larger than the grains in the matrix, ranging up to 0.4 mm. in
size. The larger hematite grains in the pebbles are broken up and
have halos around the edges. These halos are of two types: (1) there
is a depletion of hematite in the immediate area around the hematite
grain, and then a dark zone that grades away from the lighter zone (Fig. 5;
(2) there is a dark zone immediately around the edge of the hematite
grain that grades away from the grain. These two types of halos are

related to different stages in the breakup of the hematite grain. Type I

 

Figure 3 - Photomicrograph of "patchy" hematite
in plagioclase phenocrysts. Dendritic
inclusions of copper are dark areas in
phenocrysts, Transmitted light, 50 X.

l6

 

Figure 4 - Photomicrograph of bleached pebble,
Transmitted light, 50 X .

 

-Figure 5 - Photomicrograph of Type 1 halo
around edges of hematite grain,
Reflected and Transmitted light,
50 X.

18

is believed to be an early stage where there is little change, and Type 11
represents a later stage where the grain has broken up and the hematite
from the grain is being dispersed away from the hematite grain. Calcite
cement is interstitial to the pebbles and detrital grains and also
replaces feldspar grains. Epidote occurs throughout the conglomerate,
but is far more abundant at lower levels of the mine. Epidote occurs
primarily in the matrix as an alteration of the calcite. The epidote
occurs as rims surrounding and embaying calcite, or as a complete re-
placement of calcite. Some of the detrital feldspar grains have their
centers replaced by epidote. Epidote has partially to completely re-
placed some of the pebbles. In the model proposed by Jolly the epidote
is related to increasing metamorphic conditions in the zone of dehydra-
tion.

Most of the copper occurs in the conglomerate matrix. In polished
sections some of the pebbles show disseminated copper within them. The
felsite and granophyric pebbles have more disseminated copper within than
does the quartz feldspar porphyry pebbles. Copper may be found in feld-
spar phenocrysts of the quartz feldspar porphyry pebbles, dissemenated
within the phenocrysts, or along twinning planes. The pattern of copper
mineralization is related to the bedding of the conglomerate. On under-
ground surfaces the copper appears to follow the bedding, and to be re-
lated to coarser beds. The fine-grained beds may have a high porosity,
but its permeability will be less than that of a coarse grained bed.
Therefore, at a given fluid pressure, the more permeable bed will allow
a greater volume of fluid to flow through the bed. If copper is carried
and deposited from a moving solution, the greatest amount of copper
should be found associated with the more permeable beds.

Alteration of the basalt was a major factor in determining the

19

chemistry of the solutions introduced into the conglomerates in the

model proposed by Jolly. The bulk composition of the altered and re-
latively unaltered basalts are listed in Table 2. It may be seen that
the two are similar. This chemical evidence suggests that the lavas
underwent localized redistribution of their chemical components within
flow tops during their metamorphic readjustment. The alteration affects
all primary minerals - olivine, clinopyroxene, and plagioclase - as well
as groundmass constituents. Cornwall (1957, p. 213) has done a study of
the minor elements in the lava series, and his results are in Table 3.
Butler and Burbank (1929, p. 55) list 65 of the major minerals in the
lava series. The twenty elements examined in this study are only part

of the many minor elements in the system that can substitute into the
native c0pper structure. The major controling factor in the substitution
of the trace elements is the type of substitution - mutual substitution,
coupled substitution or interstitial accommodation. The atomic radius of
copper is 1.28 A and the copper structure has two types of interstices in
its face-centered cubic lattice- octahedron and tetrahedron. The octa-

hedron sites are larger than the tetrahedron sites and are 1.055 A.

20

 

 

 

 

 

 

Table 2
Calculation of bulk composition of the altered basalts and ison
‘with relatively unaltered basalts (Jelly, 1972, P. 299)
Number of l 2 3 4 5 6 7
analyses
11 14 5 5 10
SiOz 47-7 48-8 43-1 43-1 43-1 50-7 49-9
T102 1-49 1-49 1-19 1-00 1-09 1-50 1-57
A1203 15-1 14-6 15-4 17-5 16-5 15-8 15°9
Fe0* 10°93 10°43 9°05 10°73 9°63 10°93 11°39
55k) 0°19 0°17 0°14 0°18 0°16 0°18 0°20
.MgO 7°93 7°91 4°84 2°50 3°67 7°60 8°29
CaO 8°25 6°46 17°29 19°67 18°48 9°06 8°62
N320 3°22 4°14 0°70 0°65 0°67 3°75 3°38
K20 0°55 0°21 0°16 0°10 0°13 0°20 0°57
P205 0°18 0°19 0°15 0°17 0°16 0°20 0°18
H20 3°67 4°01 5°13 1°63 3°38
C02 0°16 0°14 0°37 1°07 0°72
Vblume per cent 84°6 15°4
Specific gravity 2°85 3°31 3°25 3°28
Weight per cent 82-6 17°4

 

 

 

 

 

 

 

 

* Tbtal Fe calculated as EeO.

l . Average unaltered olivine tholeiite fran pumpellyite and epidote

zones .

2 . Average olivine tholeiite with albitized feldspars fran pumpellyite
and epidote zones.

3. Average pumpellyite metadomain.

4. Average epidote'metadcuedrn

5. Average metadanain (from 0015. 3 and 4).

6 . Bulk ccmposition of altered lavas frcm pumpellyite and epidote zones
recalculated less volatiles: derived by adding appropriate weight
percentages of 0013. 2 and 5.

7. Average unmetamorphosed olivine tholeiite (col. 1) recalculated less
volatiles.

.88...— « .5350 5.23 :83 9.36596 05
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21

 

 

 

 

 

 

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.8.E.R8.§I§§Ifl§§g
noun—F

~SAMPLING AND ANALYTICAL PROCEDURES

 

Sample Locations

 

Sample locations were predetermined by the mine geologist, because
of prior knowledge of the distribution of the copper in the mine and
also the accessability of the different drifts. Figure 6 is a long-
itudinal section in plane of Calumet Conglomerate lode showing Cent-
ennial #3 mine workings and sample locations. The horizontal lines are
the drifts and the vertical lines are the shafts. The irregular lines
are the stoped out areas. The heavy dash line shows the approximate
boundary between main channel (Ore Shoot B) and tributary channels (Ore
Shoot A) in the Centennial #3 Mine.

To minimize the variables the samples were taken mainly from the
salmon bleached regions of the conglomerate. Samples 6 and 13 are
taken from the hanging wall and there are a few samples where the whole
conglomerate had been epidotized, so the samples were taken roughly from
the center of the conglomerate. Descriptions of the sample locations

along with polished section descriptions are in Appendix A.

Analytical Work

 

The gross mineralogy of the specimens was studies with a binocular
petrographic microscope using forty to four hundred power magnification.
The opaque grains in the specimens were studied in polish section
by using reflected light and sixty power magnification. Description of

the polished sections are in Appendix A.
Copper was extracted from samples and cleaned with concentrated
nitric acid. Then 1.000 g. of copper was put into 100 ml. flasks.

Twenty ml. of concentrated nitric acid was added to the flask to dissolve

22

23

 

 

 

 

36
ORE SHOOT A

 

 

1r4zde' LongHudinal secfion in plane of

:44 Calumet Conglomerate lode showing
Centennial No.3-'6 mine workings
Calumet, Michigan

048

 

lOOO fl

_Figure 6

24

the copper and then the flask is filled up to the fiducial mark with double
quartz distilled water. Some samples did not have 1.000 g. of copper,

so relative proportions of nitric acid and water were used. When nec-
essary the solutions were diluted to bring elemental concentrations into
the working curve portion for the instrument used.

Standards were made for Fe, Mg, Zn, Na, Mn, Sr, K, Ba, Ca, Ni, As, Sb,
Ti, Cr, Pb, Cd, Bi, Co, and Ca using the following materials Fe metal,
MgO, ZnO, Na2C03, Mn304, SrCO3, K2CO3, BaC03, CaC03, N10, A5203, Sb metal,
TiOg, K2Cr207, Pb (N03)2, CaO, Bi203, Co metal, and CSZSO4 respectively.
This material was obtained from SPEX Industries, Inc. and the purity of
each sample ranged from 5-95 to 6-95. A stock solution of 500 ppm was
made first and then depending on the linearity and sensitivity of the
atomic absorption unit the samples were diluted to the range from 0.5 to
10 ppm.

A Sargent—Slomin Electrolytic Analyzer was used to remove copper and
silver from solution by electroplating on platinum electrodes. Both
copper and silver have large activities when neutron activated, and cause
serious matrix effects on atomic absorption. The current was set at one
amp. and the voltage was stable at 2.5-3.0 volts. The electrodes were
lowered further into the beaker to determine if any copper ions were left
in the solution . If no copper plates out on the cathode after 15 minutes
then the operation was considered complete. Average time for each sample
to run to completion was ten hours.

The atomic absorption analysis was performed on a Perkin-Elmer 303
Spectrophotometer using single and multi-element hollow cathode tubes
(Ca, Mg, Fe, Ba, Cd, Na, Mn, Zn, Cr, Pb, and Ni). All elements were
analyzed using a four inch single slot burner head requiring an acety-

lene flow of eight pounds and an air flow of thirty pounds. The elect-

25

ronics of the instrument were allowed to stablize for a half hour before
each run.

Neutron activation analysis was used to test for Sb, Ti, Sr, Bi, C5,
C0, and As. The source of the neutrons produced was from MSU's Triga
Mark I nuclear reactor. Irradiation of a two hour duration at a flux of
about 1 X 1012 n/cm"2 sec. was used. The samples were counted twenty-four
hours after they were pulled.

Flame emission spectrometry was used on a model 21 Coleman Instrument
to determine K.

Of the elements analyzed; Mg, Fe, Mn, Ca, Na, Zn, K and As were the
only elements detected with the above equipment. Table 4 gives the ppm
for each sample. Table 5 give the mean, range, standard deviation and
coefficient of variation for each element. The set up for each element,
for the particular equipment used, and the working curve data and cor-
relations are presented in Appendix B.

The electron microprobe was used to determine the distribution of
the elements in the native copper. Probe traces across copper grains
for Ag, Fe and Mg were run for samples from the first, thirty-third and
thirty-fourth levels of the mine. Two probe traces, in different parts
of the copper grain, were run for each sample. Semi-quantitative analysis
indicate silver is the most enriched and Mg the least enriched of those
elements analyzed in the copper grains. These results are in agreement
with quantitative atomic absorption data for Fe and Mg. Scans across
several copper grains shows that there is no zoning of at least Ag, Fe,

and Mg in the copper grains.

Sample #

1-17
1—18
9-1
9-2
17-3
17-5
17-7
27-19
27-20
33-8
33-9
33-10
33-11

33-12

33-13*

34-14
35-15
35-21
35-22
35-23
35-24
35-25

35-26

Table 4

Elemental abundance (p.p¢m.) for eadh sample

Mg
1.250

0.060
0.260
0.710
0.001
0.008
0.005
0.392
0.120
0.430
0.001
0.180
0.028
0.125
1.580
0.035
0.023
0.099
0.270
1.070
0.040
0.170

0.060

Fe
3.496
0.197
0.167
2.396
0.013
0.028
0.104
0.130
0.148
0.522
0.073
0.306
0.010
0.211
3.662
0.069
0.154
0.229
0.549
1.858
0.122
0.284

0.079

Mn
0.053
0.001
0.067
0.031
0.001
0.001
0.006
0.019
0.017
0.026
0.018
0.001
0.023
0.006
0.127
0.019
0.019
0.023
0.001
0.058
0.027
0.025

0.001

Ca
0.752

0.556

17.630

1.400
0.257
1.886
0.442
0.511
2.360
2.694
7.979
0.674
4.314
0.752
0.001
5.478
0.163
5.837
0.495
2.083
3.538

11.351

1.031

Na
0.895
0.201
0.441
0.564
0.073
0.064
0.588
0.129
0.181
0.387
0.197
0.105
0.123
0.060
0.242
0.056
0.091
0.263
0.229
0.333
0.078
0.200

0.065

Zn
0.031
0.014
0.078
0.033
0.019
0.028
0.031
0.016
0.019
0.036
0.021
0.012
0.025
0.027
0.058
0.019
0.035
0.029
0.047
0.042
0.019
0.022

0.028

K
1.645
0.766
0.450
1.645
0.005
0.287
0.296
0.116
0.125
0.595
0.125
0.227
0.048
0.116
0.227
0.039
0.082
0.125
0.279
0.373
0.056
0.390

0.014

As
0.197
0.097
0.233
0.264
0.070
0.049
0.080
0.128
0.117
0.200
0.042
0.169
0.099
0.151
0.509
0.093
0.210
0.248
0.089
0.097
0.040
0.138

0.061

Sample #

35-27
35-28
35-29
35-30
35-31
35-32

35-33

50-16**

 

 

Table 4 (cont'd.)

27

Elemental abundance (p.p.m.) for each sample

Mg
0.018
0.140
0.210
0.150
0.023
0.051
0.037
0.009

Fe
0.094
0.212
0.254
0.021
0.637
0.079
0.081
0.057

Mn
0.016
0.001
0.037
0.021
0.023
0.016
0.001

0.027

Ca
0.136
0.665
6.328
5.465
0.098
0.206
0.303
3.060

Na
0.201
0.284
0.272
0.079
0.193
0.457
0.167
0.103

*‘I'rap rock (not used in trend determinaticm) .

**Not used in trends because of distance from other sample sites.

Zn
0.033
0.040
0.020
0.022
0.027
0.073
0.017
0.015

K
0.108
0.407
0.296
0.125
0.193
0.338
0.206
0.091

As
0.062
0.071
0.201
0.006
0.059
0.172
0.196
0.065

variable

Fe

Mn

Na

N

Cases

29
29
29
29
29
29
29

29

Mean

.2057
.4318
.0192
2.9443
.2406
.0298
.3268

.1272

28

Table 5

Range (ppm)
1.250—0.001
3.496-0.010
0.067-0.001
17.630-0.098
0.895—0.056
0.078-0.012
1.645-0.005
0.264-0.006

Statistical Summary of Table 4

Std. Dev.
.3086
.7920
.0175

3.9825
.1953
.0153
.4058

.0689

Coeff. of var.
150.0
183.4

91.1
135.3
81.2
51.3
124.1

54.2

STATISTICAL METHODS

 

The data were reduced by SPSS (Nie et al, 1975) subprogram Pearson
to produce Pearson correlation coefficients. Table 6 shows the cor-
relation between single variables and Table 7 shows correlations with
grouped data. Fe, Mg, Na, and K are the elements that show the highest
correlations between one another. For this reason Fe and Mg were grouped
and Na and K were grouped to determine if there were any interelemental
relationships not detectable in the single element correlations. There
is no significant differences in the two types of correlations except
for a slight increase or decrease in a few of the element correlations.
Overall the alkali and FeMg shows a slightly higher correlation then the
group did as individual elements. Mn shows a higher than normal cor-
relation with Mg, Fe, Ca, and Na. This trend follows through in the
grouped data also.

Trend surface maps of the data were produced from a modified com-
puter program originally written by Miesch and Connor (1968). The basic
technique consists of solving a set of simultaneous equations by Gaussian
elimination of coefficients of the regression equation at a preselected
level of confidence and using the results obtained at each stage of the
elimination as stepwise test criteria (Meyers, 1974; Efroymson, 1960).
Trend equations from stepwise regression are considerably more effi-
cient than conventional polynomial equations in that they may account
for large proportions of the total sum of squares with considerably
fewer terms (Miesch and Connor, 1968, p. 1). The trend equations are
used to print the trend surface maps. Quintic equations were used at
the 10% significant level for the arithmetic transformation of the trace

element data. The sums of squares accounted for by the trend surfaces

29

30

Table 6

Pearson Correlation Between Single variables

K
0.7252
0.8514
0.3867

-0.0536

0.7941
0.1707
1.000

*****

Mg Fe Mn Ca Na Zn
Mg 1.000 0.9145 0.6410 -0.0428 0.6627 0.1760
Fe ***** 1.000 0.5356 -0.1508 0.7312 0.1152
Mn ***** ***** 1.000 0.5605 0.5136 0.4084
Ca ***** ***** ****** 1.000 0.0355 0.2773
Na ***** ***** ****** ***** 1.000 0.4519
Zn ***** ***** ****** ***** ***** 1.000
K ***** ***** ****** ***** ***** *****
.AS ***** ***** ****** ***** ***** *****
Table 7
Pearson.Correlation Between Grouped variables
FeMg .Alkali Ca Zn Mn
FEMg 1.000 0.8347 -0.1227 0.1346 0.5752
.Alkali ***** 1.000 -0.0258 0.2748 0.4487
Ca ***** ***** 1.000 0.2773 0.5605
Zn ***** ***** ***** 1.000 0.4084
Mn ***** ***** ***** ***** 1.000
AS ***** ***** ***** ***** *****

As
0.3565
0.4889
0.2214
0.2819
0.3924
1.000

As
0.3443
0.3526
0.3924
0.2214
0.4640
0.2819
0.4674
1.000

31

for each element are Mg, 65.14%; Fe, 84.515%; Mn, 63.210%; Ca 65.810%
Na 83.234%; Zn, 55.114%; K, 91.301% and As, 51.349%.
The intervals on the maps showing the trend-surface, original data
and residuals are represented by the alphanumeric characters, "C" (highest),
"B", "A", "$" (reference contour), "1", “2", "3“ (lowest), and the six

intervening blanks.

DESCRIPTION OF ELEMENTAL TRENDS

Three different types of trends were examined. Comparison of the
different elemental concentrations for each level were examined to det-
ermine if there is a zonation with depth. Element averages for each
drift are listed in Table 8. Statistical tests to determine the signifi-
cance of each average was not done because the sample size is to small
to get any meaningful results. There are crude patterns for Mg, Fe, Mn,
Na and K where the upper levels have a greater elemental amount then the
lower levels. Ca shows the reverse, where the lower levels have a greater
amount. Zn and As have a much more irregular pattern. These types of
patterns are due to the sampling pattern and not to the distribution of
the elements in the copper. The patterns will be further explained in the
following paragraphs.

Trend surface maps were examined for possible regional trends in
the mine (Fig. 7-Fig 30). As would be expected from the Pearson correla-
tions; Mg, Fe, Na and K show similar patterns. All four elements show
bull's eyes in the direction of the main channel conglomerate (right side
of the map) and increasing values updip. Unfortunately, the sampling
pattern is probably the major factor controlling the trend surface. All

of the trend maps have somewhat of a bull's eye in the right side of the

Level Pop.
1 2
9 2
l7 3
27 2
33 4
34 l
35 14
50 1

Averages of Each Elanent for Each Drift level (pgn)

Mg.
0.655
0.485
0.005
0.256
0.153
0.035
0.160
0.009

Fe
1.847
1.282
0.048
0.139
0.224
0.069
0.316

0.057

32

Table 8

Mn
0.027
0.049
0.003
0.018
0.015
0.019
0.018

0.027

Ca
0.654
9.515
0.862
1.436
3.283
5.478
2.533
3.060

Na
0.548
0.503
0.242
0.155
0.174
0.056
0.205
0.103

Zn
0.023
0.056
0.026
0.018
0.024
0.019
0.031
0.015

K
1.201
1.048
0.196
0.121
0.222
0.039
0.213
0.091

AS
0.147
0.249
0.066
0.123
0.142
0.093
0.123
0.065

33

FIGURE 7

TREND HAP - CENTFLNIAL HG IRENE REFERENCE CCNTCU? =' .EBZQ
XHI XMA ' = .0010 YHAX = 59-250

A = .0010 X = 61.7150 YHIL

 

   
    

Mai-Autumn“ .

uuuuuwuu

 

 

 

34

FHRRE 8
CONTOUR PAP 0F CRIGINAL DATA - MG - ‘

11111111111
111111111

     
   
    
     
   
 
 

   

 

532335333’

333335335533535.

  

3

333

33333

333333

111111111111 33333333

11111111111111111 . 3333333333

11111111111111111 .3333333333333

11111111111111 333333333333333

111 11111111 2 3333333 .333. . ~3333333333333333

r _L-11111 22 333333333333 33333333. 333333333333333333

222. 111 2? 333333333333333333333333333333333333333333333333333333

222 .1 222 3333333333333333333333333333333333333333333333333333333

222 o -222222 33333333333333333333333333333333333333333333333333333
2222 222222222 3333 333333333333333333333333333333333333333333333.

3222222222222222 33333333333333333333333333333333333333333333

’ 2222222 222222, 33333333333333333333333333333333333333333333333

3333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333333333333.
3333333333333333333333333333333333333333333
33333333333333333333333333333333333333333
33333333333333333333333333333333333333333
$33333333333333333333333333333333333333333
33333333333333333333333333333333333333333

  
 
   
  
   
 

222222222222222222
2222222222222222222
22222222222 7222-
2222222222 222

    
  
 
   
 
    

2222222222 222 22 33333333333333333333333333333333333333333
222222222222 222222 2222 $333333333333333333333333333333333333333333'
222222222222222222222222 22 3333333333333333333333333333333333333333333
222222222222222222222222 22 3333333 33333333333333333333333333333333333
222222222222222222222222 22 333333333333333333333333333333333333
22222222222222222222222’ 333333333333333333333333333333333333'

2222222222222222222222
2222222222222 22

‘333333333333333333333333333333333333
3333333333333333333333333333333333333
3333333333333333333333333333333333333
3333333333333333333333333333333333333
3333333333333333333333333333333333333
i33333333333333333333333333333333333333
.3333 3 333333333333333333333333333333333333333
[3L 33333 3 3333333333333333333333333333333333333333

 

 

REFERENCE CCNTOUR = .6237 CCNTOUQ INTEQVAL = .0675

35

runmz 9
RESIDUAL ”4‘- MG

 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
    
  
  
 
 
  
  

i"""""' ..... --------------------------.--- ...... -------------------------

11111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
511111111111111111111111111111111111111111111111111111111111111111111111111111
011111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
1111111111111111111111111 1111111111111111111111111111111111111111111111111111
11111111111111111111111 11111111111111111111111111111111111111111111111111
11111111111111111111111 11 11111111111111 1111111111111111111111111111111
11111111111111111111111 111111111111111111111111111111111111111111111111111

111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111 11111111111111111111111111

  
  

 

1111111111111111111111111
1111111111111111111111111111 11111111111111111111111111
11111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111111111111
111111111111 1111111111111111111111111111111111111
1111111111CIi:;:>111111111111111111111111111111111
11111111111111 1111111111111111111111111111111111
111111111111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111111111
1 11111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111
11111111111111111‘ 111111111111111111111111
11111111111111111 1111111111111111
1111111111 111111 1 11111111111111111

 
 
 
 
  
  
 
 
 
 
 
     
  

1111111111111111111111
11111111111111111 1111 QE1 22

111111111111111111111111111

 

REFERENCE CCNTCUQ = .1655 CONTOUR INTERVAL = .0508

36

FIGURE 10
TREND HAP ' CENTENNIAL FF TRFNC REFERENCE CCNTCUR = 1.8M05
xnlN = 0031: Xan = 61.715: THIN 3 05010 YMAX 3 590250

      
     
   

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3‘2 22

 

. ‘22 22222” 33
72222 33
3 3.
3. 33
3 33
333 - 33
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211

 

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37

FIGURE 11
COBYOUQ rap 0? CRIGINAL DATA - PE

    

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q ,
Ho Item?“ 00090

0 16‘!) no On J. 0'.

.00 It. cl.

’22222222222222222222222222
2222222222222222

   
  
 
  

3

333

33333
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33333333
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3333333333333

3333333 333333333333333
3333333333. 33333333333 33333333333333333
33333333333333333333333333333333 333333333333333333
3333333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333333333333333333333
33333333333333333333333333333333333333 33333333333333333'
333333333333 333333333333333333333333333333333333333333333333

‘l
333333733333313333333“3“3“‘333333‘3333333‘333333 333333333
3

333333333333333333333333333333333333333333333333333333333333
3333333333333333333333333333333333333333333333333333333333333
1111111313133~~3311131311331112333131111 11113111111311331313 33333333333313333
33333333333333333333333333333333333333333333333333333333333333333333333333333
"333333333333333333333333333333333‘333” 3333333333333333333333333333333333333

11111111111111111
1111111111111
11111111

  

 

33333333333333333
333333333333333
333333333333333
333311111333333

1‘

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233333111311113111511111 13133331333313}313313333333133333333323333333333323333
:33333333333113113111111 11331313133312133333331313133333333333333333333333333
111311131333222333331333 11131333331331:13333333333133:31333323333333333232313
:33333333333333333313333 31333333333333:33333333333333333333333333333333333333
333333233333233331333313 3333322331333333133333:333313331333333331333333223333
331333133313111131313111 111332233332233223:3313333133331333313333333133223333
3333333333313131 1331133133333333321333331531331333333313313333333333

3333333333333333333333333333333333333333333333333333
‘333333333333333333333333333333333333333333333333333
333333333333333333333333333333333333333333333333333
333333333333333333333333333333333333333333333333333
333333333333333333333333333333333333333333333333333
333333333333333333333333333333333333333333333333333
333 3333333333333 3333333333333333333333333333333333

L-..--------- --------- ......... --------..----.---- -‘.------ ....... --------

1331133311

 
   

 

REFERENCE CCNTOUR = 1.7511 CONTOUQ INTERVAL = .Zkhu

38

FIGURE 12
RESIDUAL PAP-FE

11111111111111111111111111111111111111111111111111111111111111111111111111111
.11111111111111111111111111111111111111111111111111111111111111111111111111111
'11111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
v11111111111111111111111111111111111111111111111111111111111111111111111111111
-11111111111111111111111111111111111111111111111111111111111111111111111111111

11111111111111111111111111111111111111111111111111111111111111111111111111111
v11111111111111111111111111111111111111111111111111111111111111111111111111111
-11111111111111111111111111111111111111111111111111111111111111111111111111111
'11111111111111111111111111111111111111111111111111111111111111111111111111111
v11111111111111111111111111111111111111111111111111111111111111111111111111111
I11111111111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111111111111
-11111111111111111111111111111111111111111111111111111111111111111111111111111
-11111111111111111111111111111111111111111111111111111111111111111111111111111
v111111111111111111111111 111111111111111111111111111111111111111111111111111
.1111111111111111111111 11111111111111111111111111111111111111111111111111

11111111111111111111 1 11111111111111111111111111111111111111111111111
.11111111111111111111 11111111111111111111111111111111111111111111111
~111111111111111111111 11111111111111111111111111111111111111111111111111
.1111111111111111111111 111111111111111111111111111111111111111111111111111
.11111111111111111111111111111111111111111111111111111111111111111111111111111

11111111111111111111111111111111111111111111111111111111111111111111111111111

11111111111111111111111111111111111111111111111111111111111111111111111111111
l11111111111111111111111111111111111111111111111111111111111111111111111111111
»11111111111111111111111111111111111111111111111111111111111111111111111111111
v11111111111111111111111111111111111111111111111111111111111111111111111111111
-11111111111111111111111111111111111111111111111111111111111111111111111111111

11111111111111111111111111111111111111111111111111111111111111111111111111111
'11111111111111:1111111:11111111111111111:1111111111111111111111111111111:1111

  
  
     
    
 

111111111111111111 1111111111111111111111111111111111111111111111111111111
I11111111111111 111 1111111 111' 1111111111111111111111111111111‘ 1111
.1111111111111111111 n1111111 1111111111111111111111111111111111111111111
111111111111111111111 1111111111111111111111111111111111111111111111111111
11111111111 1111113-1111111111111111111111111111111111111111111111111111

1 . 1111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111

1 1111111111111111111111111111111111111111111111111

1111111 C) 1 111111111111111111111111111111111111111111111111

111111111 1 111111111111111111111111111111111111111111111111
1111111111 111111111111111111111111111111111111111111111

  
  

1111111111111
1111111111

1111111111111111111111111111111111111111111 1
1111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111

REFERENCE CCNTCUR = .2797 CCNTOLE IBTERVLL = .1111

39

FIGURE 13
TPENO HfiP - CEBTENNIAL “N TRENC QEFERENCE CONTOUR = .0360
XMIB = .611" XHfiX = 61.7150 YHIN 3 .0010 YHAX = 59.250

 

13333333333333
33333333333

NNthxmfi)
mra l’fl I‘J rlnl
NNI‘JNYUN

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rl

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1 N
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40

FIGURE 14
CCKTOUR PAF OF CRIGINAL DATA-MN

      
  

 

11'

~111 111
8 1111

.1111111- 11111
-111111111 111111
.111111111111 1111111 11111111,
1,111111111111111 11111111111111 111111111
111111111 11111111111111 1111111111111
1 -1111111111111=
222 2222222 111111111 11111111111111-

22 2222222222222 111111111111 111111111111111

2 2222 111111111111111111111 1111

0 22 22222222222222 11111111111111 1111111
r222 222 v222222222(:3222 1111111111
'22 22222 2222222222222222 111111111111:
r22 -22222222 2222222222222222 11111111111111
'2222 222222222222 2222222222222222 1111111111111111

'2222222222222222222 22222222222222 111111111111111
'222222222222222222222 22222222222 1111111111 1 ‘
222222222222222222222 2222 111111 222 .
222222222 22222222222 2 22 "2' 2222222.
222222222222 2222222222222222222.

  
     
   

 

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2222222222222222222222222-
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222222222 2 22222222222222222222222222-
22 2222222222222322222222222222222222222222
2 222222222222222222222222222222222.
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2 222222222222222222222222-

2 2 22222222222222222222222-

4J 22222 2222222222222222222222-

11 1111 22222 2222222222222222222222-

.11111111111111f1111111 2222 2222222222222222222222

v11111111111111111 11111 222 (;::) 2222222222222222222 222
'11111 111111 111 ' ,2 1 2222222222222222
.1 11111 2222 2222222222

        

1111 1 11
1111 ' Jfi\ 1 222' 1E3\

REFEREKCE CCNTCU? = .3333 CCBTCUF IBTERVfiL = .OIAE

41

FIGURE 15
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REFFPENCE CCNTOUR = .3020 CCNTCU; IhTERVAL = o0(37

41

FIGURE 15
RESIDUAL V5F"NN

    
 
   

      
  

   
 
   

       

   

  

  

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REFFPENCE CCNTOUR = .3020 CCNTCU; IhTERVAL = .0(37

 

42

FIGURE 16
TRFNU HAP - CENTENNIAL CA TPEND PEFERENCE CCNTCUR = 9oh118
XHIK = .0317 XHAY = 61.7150 YflIN = .0010 YHAX = 59.250

 

    
 
 
 
 
  

 

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333333333333 33333333333333
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3h--- 0------

43

FIGMEII?
COBTOUR HAP 0p ORIGINAL UATA-CA

  
       

 
 
 
 
 
 
 
  
 
 
  
  
 
  
  
  
   
  
   
 

  
  

  
 
   
       
   

   
    
 
   

  

---------- O ..... C CO- OOOOOOOOOOOOOOOOOOO O CCCCCCCCCCCC o ...... -C-OOOOOOCCO1
5333333333 222222222 11111111111111111
3333333333 222222222 1111111111111111
13333333 ~ 222222222 111111111111111

22222222 11111111111111
3 2222222 11111111111111
333 22222222 11111111111111
33333 2222222 11111111111111
3333333 222222 1111111111111
333333333 2222222 111111111111111
33333333333 22222222 111111111111111
3333333333333 22222222 111111111111111
333333333333333333333 22222222 1111111111111111
33333333333333333333 222222222 111111111111111111
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REFERENCE CCNTGUR = Soébh8 CCNTCU: INTERVAL = 1.1816

44

FIGURE 18
RESIDUAL PAF-CA

r ............................................... ----- ..... --------- ..... ------1

    
  

 

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1131113131113333 3 2633‘ [GL

REFERENCE CCNTCUR = -.1961 CCNIOUR INTERVAL = .555h

  
   
 

 

  
    
   

 

 

 

 

  
  
 

 

 

 

 

   

310023 19
IRFND HAP - CENTENNIAL NA rqruc REFERENCE ccnroue = .«002
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46

FIGURE 20
CCBTOUR MAP 0‘ CFXGINAL DATA- NA

     
  

 

 

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47

FIGURE 21
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PEFFQENCE CCNTOUR = .321) CChTCUF INTERVAL = .3261

48

FIGURE 22
TREND HAP - CERTFKNIAL 2N TRENC REFE°ENCE CONTCUR = .0h81
XHIN = .0013 XHAX = 61.7150 YPIN = .0010 YHAX = 59.250

   
    
 
   
   
   
   
   
 
     
       
     
     
     
     
      
    
 
   
 
     
  
   

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49

FIGURE 23
COATOUR HfiF OF CRIGINAL DATA-v28

22 11111111111 133311111315153315153
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2222 11111111111 1131313111111135
1111111111 331553553313113

    

   
     
      
     
     

  

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22 2222222222222222222

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REFFRENCE CCNTOUR = .GHSQ CCNTOUF INTERVAL = .0195

anmx 24
RESIDUAL PAF-ZN

- -------------- ............. ---------- ......... -----------------------------1

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51

FIGURE 25
TREND MAP ‘ CERTENHIAL K TREND REFEFENCE CCNTOUF = .9029
MI 010 XH A)? = 61.7150 YNIN= .2013 YHAX : 59.250

 

 

 

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52

FIGURE 26
CCNTOUR MAP OF ORIGINAL UATI- K

 

  

     
 
     
      

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53

annu:27
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54

FIGURE 28

TPEND HAP - CEhTF‘
XHIN

LIAL ‘S tqu '
91“ x"‘ = 61.7150

REFERENCE CCNTCU
WI}. = .0 1

YHAX

'150g
: 59.250

     

 

     

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FIGURE 30
RE 5 IDUAL HAP-AS

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REFERENCE ccurond a' .0199 ccnrcuc Ianaan = .0113

 

 

57

maps and a half circle at the top of the maps. The main things these

maps can show are the relative amounts of each element in different areas
of the mine. A closer sampling pattern is needed to determine any smaller
scale fluctuations or patterns in the trends of the different elements.

The third type of trend examined was the comparasion of elemental and
mineralogical trends within one permeable channel. Sample 8, 9, and 10
were compared to determine if there was any type of zonation perpendi-
cular to the channel direction. Table 9 shows relative rankings for all
elements for each sample, sample 8 has a larger amount of each element
then either 9 or 10, except for the element Ca. In decreasing order,
for the amount of Ca in each sample. are 9, 8 and 10. Data in Table 10
can be used to determine a possible explanation for a larger amount of
Ca in 9 then in the other two. This table shows percentage of each min-
eral for each sample determined from polished sections. Sample 9 has 37%
Ca bearing minerals whereas 8 luas 32% and 10 only has 20%. This difference
in mineral abundance could be part of the reason why 9 has more Ca in the
copper then either 8 or 10. In order to determine if there was any trend
present parallel to a channel direction, Sample 8 was compared to 20 and 19
which fall along the channel "strike". The trend indicates that updip from
Sample 8, elemental abundance in the copper decreases. This apparent
trend continues up to the 17 level except for a possible discrepancy in
the Zn values. Another possible trend within Samples 17 (channel center)
and 18 (channel margin) on the first level show that the center of a per-
meable channel (Sample 17), where there is more visible copper, has a
higher concentration of each element then do the margins of the channel.
Variations of the elemental trends are due to the mineralogy or possibly

to the sample sites.

58

Table 9

Relative Ranking of Element Abundance for Each Sample

Sample # Mg Fe Mn Ca Na Zn K As
1-17 2 2 4 17* l 10* 1* 8
l-18 17 14 17* 20 13* 22 2 17*
9-1 8 15 2 1 5 1 4 4
9-2 4 3 6 15 3 9* 1* 2

17-3 28* 29 17* 25 26 18* 24 23
17-5 26 27 17* 14 28 12* 10 28
17-7 27 20 16* 23 2 10* 9* 21
27-19 6 18 12* 21 19 20 16* 14
27-20 15 17 14 12 17 18* 15* 15
33-8 5 7 8 ll 6 7 3 7
33-9 28* 24 13 3 15 16 15* 19
33-10 10 8 17* 18 21 23 12* 11
33-11 22 30 10* 8 20 14 21 16
33-12 14 13 16* 17* 29 13 16* 12
33-13 1 l 1 30 11 3 12* 1
34-14 21 25 12* 6 3O 18* 22 18
35-15 23* 16 12* 27 23 8 19 5
35-21 16 ll 10* 5 10 11 15* 3
35-22 7 6 17* 22 12 4 11 20
35—23 3 4 3 13 7 5 7 17*
35-24 19 19 7* 9 25 18* 20 29
35-25 11 9 9 2 14 15* 6 13
35-26 17 23* 17* 16 27 12* 23 26
35—27 24 21 15* 28 13* 9* 17 25
35-28 13 12 17* 19 8 6 5 22
35-29 9 10 5 4 9 l7 9* 6
35-30 12 28 11 7 24 15* 15* 30
35-31 23* 5 10 29 16 13 14 27
35-32 18 23* 15* 26 4 2 8 10
35-33 20 22 17* 24 18 19 13 9
50-16 25 26 7* 10 22 21 18 24

*Mbre than one sample at this element abundance.

59

Table 10

Percent Minerals in Each Sample

Sample # Epidote Plagioclase Quartz Calcite Copper Henatite

1-17 2 5 15 10 10 5
1-18 1 10 15 3 5 5
9-1 1 10 15 5 l 3
9-2 5 10 10 3 5 4
17-3 5 5 5 5 0 5
17-5 5 5 10 3 5 2
17-7 no polished section
27-19 15 10 10 5 7 5
27-20 13 3 10 3 3 3
33-8 15 2 10 15 7 2
33-9 25 2 10 10 3 1
33-10 10 7 15 3 3 5
33-11 12 l 2 11 8 3
33-12 5 5 5 5 5 1
33-13 Trap rock
34-14 5 2 3 2 5 5
35-15 20 0 0 0 25 0
35-21 no polished section
35-22 15 5 10 5 5 3
35-23 10 2 5 15 5
35-24 no polished section
35-25 25 0 5 O 5 1
35-26 20 5 5 2 5 3
35-27 25 0 3 O 15 1
35-28* 20 0 2 5 15 1
35-29* 5 5 10 5 5 5
35-30 12 10 10 8 6 4
35-31 10 5 10 2 5 3
35-32 no polished section
35-33 3 3 3 2 5 2

50-16 no polished section

*Chlorite is present in sample 28 and 29, five and one percent
respectively.

60

,Comparison of the different elemental concentrations for each level
show crude patterns as you go downdip. The copper grade was low in the
upper levels of the mine and the samples were mainly taken from the center
of the permeable channels, where there was the largest concentration of
copper. The copper grade increases downdip in the mine and a larger
number of samples was collected because of the availability of the native
copper. This larger number of samples allowed for a greater divergence
of the sample sites from the center of the permeable channels. The largest
concentration of trace elements in the copper is in the center of the
permeable channels. With this divergence of the sample sites away from
the center of the permeable channels the average concentrations of each
trace element for each level would depend on the sample sites and how
many samples are averaged. Thus. the first trend comparisons have trends
caused by the sample locations and number of samples. the second trends
are over too large an area to show the small fluctuations and the third
trend comparisons start to show a pattern with the copper, permeable

channels and trace elements in the copper.

SUMMARY AND CONCLUSION

 

Thirty-three samples were collected along and updip within the
Calumet and Hecla Conglomerate in the Centennial #3 Mine, Houghton County,
Michigan. The intent of this study was to examine trace elements from
native copper samples to determine if they could be used to monitor
changes of the ore solution.

Sampling size and distribution was one of the major factors in det-
ermining possible trends. Sampling size and distribution hindered the
reliability of the first two types of trend comparisons: comparison of the
different elemental concentrations for each level and trend surface maps
for possible regional trends. The third type of trend examined was the
comparison of elemental and mineralogical trends within one permeable
channel. This third trend comparison shows a pattern where the center
of the permeable channel,which has the greatest concentration of copper,
has the highest concentration of trace elements in the native copper.

In using this third type of trend comparison, the size and location
of the permeable channels are needed if the channels are small and irreg-
ular in shape. Possible overlaping of the elemental trends for per-
meable channels could occur if the sample sites are not determined to
which channel they belong. There is also the problem where the main
channel and tributary channel branch off. The solution movement
through this area was quite irregular, and the elemental distribution is
also irregular.

Elemental distribution in native copper grains was determined using
the electron microprobe. There was no zonation of Ag, Fe or Mg in the
native copper grains.

Jolly (1974) did a study on the behavior of Cu, Zn and Ni during

61

62

prehnite-pumpellyite rank metamorphism in the Lava Series in which he
concluded that both copper and zinc were mobilized during prehnite-
pumpellyite facies metamorphism, and nickel was not appreciably affect-
ed by the metamorphic process except where there was dilution by void-
filling secondary minerals. This work by the author is in agreement
with Jolly for the mobilization of Zn and the immobility of Ni during
the metamorphic process.

The twenty elements examined in this study are only part of the
many elements in the system. Other elements that have been associated
with the conglomerates are Mo, w, Zr, F, P, and Cl. Powellite
(Ca(Mo,W)0) has been reported from the Isle Royale mine, and a few well-
formed crystals have been found in the Calumet and Hecla conglomerate.
Zircon(ZrSi0) occurs as primary minerals of the felsites and apatite
(Ca(P0)F)or (Ca(P0)Cl) occurs sparingly in the felsite pebbles of the
conglomerates and in the lava series.

The data presented in this investigation were from ore samples
associated with the so-called salmon bleaching alteration. It is
not clear whether bleaching and copper deposition was contemporaneous.
It is clear, however, that the trace element content of the copper is
related to enclosing rock (i.e., higher Fe and Mg in a basalt host
relative to a conglomerate host) but variations of the trace element
content within the conglomerate does not vary significantly in fine
flake copper or more massive clusters. Stated otherwise, no empirical
trace element trend is apparent which would indicate greater copper con-

tent within the conglomerate.

BIBLICBRAPHY

 

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Broderick, T.M., et a1., 1946, Recent contributions to the geology of the
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, 1935, Differentiation in lavas of the Michigan Keweenawan:
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Butler, B.S. and Burbank, W.S., et a1., 1929, The copper deposits of
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Hamblin, W.K. and Homer, W.J., 1961, Sources of the Keweenawan conglom-
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Heinrich, E. Wm. , 1965, Microscopic identification of minerals: McGraw—
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Howarth, R.J. , 1967, Trend surface fitting to random data — an experi-
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Jolly, W.T. , 1974, Behavior of Cu, Zn and Ni during prehnite-pumpellyite
rank metamorphisn of the Keweenawan basalts, northern Michigan:
Econ. Geol., V. 69, p. 1118—1125.

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, 1972, Degradation and metamorphic differentiation of the
Keweenawan tholeiitic lavas of northern Michigan, U.S.A.: Jour.
Petrology, v. 13, no. 2, p. 272—309.

 

Livnat, A., Rye, R.G. and Kelly, W.C., 1976, Stable-isotope and fluid
inclusion studies of the Keweenawan copper district, northern
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Mason, B. and Berry, L.G., 1968, Elments of mineralogy: W.H. Freeman
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Peters, D.G., Hayes, J.M. and Hieftje, G.M., 1974, Chemical separations
and measure'tents-theory and practice of analytical chemistry:
Sanders Golden Series, 772 p.

Silverman, M.S. , 1975, Structural geology and interpretation of trace
element distribution in soils overlying a fault zone in the north-
ern Shenandoah Valley, Jefferson County, West Virginia: unpub.
Master's thesis, University of Toledo, 202 p.

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Stanton, R.L. , 1972, Ore Petrology: PbGraw-Hill Book Co., 713 p.

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Portage Lake Lava Series, Michigan copper district: Econ. Geol. ,
v. 54, no. 7, p. 1250-1277, no. 8, p. 1444-1460.

Timperley, M.H., Brooks, R.R. and Peterson, P.J., 1972, Trend analysis
as an aid to the comparison and interpretation of biogeochenical
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Weege, R.J. and Pollock, J.P., 1972, The geology of two mines in the
native OOpper district of Michigan: Econ. Geol., v. 67, p. 622-633.

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, 1968, The native OOpper deposits of northern Michigan: in
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, 1960, The Keweenawan lavas of Lake Superior, an example of
flood basalts: Am. J. Sci., 258A, p. 367-374.

 

 

APPENDIX A
SAMPLE DESCRIPTIONS AND LOCATIONS

66

The samples are labeled with drift level first and the second number
is the sample number shown in Figure 6. The percentages are visual est-

imates and the epidote refers to epidote group minerals.

- 1-17 (TAK) -

Sample 17 is from the first level and is 308 feet north of Number 6
shaft. The conglomerate at this point is eight feet thick and the sample
is taken 4 feet above the footwall.

Epidote comprises 2% of the section and is less than 0.01 mm. in size.
Epidote is interstitial to the pebbles and large detrital grains, and also
replaces calcite. The detrital grains of feldspars have albite twinning
and have a composition of approximately An37 . The feldspar comprises 5%
of the section and are in the range from 0.5 to 2mm. in size. The grains
are corroded around the edges and have dissemenated hematite throughout
most of the grains. There are detrital grains of quartz and also secondary
quartz interstitial to the other grains and pebbles. The detrital grains
are less than 2mm. and are subrounded. There is approximately 15% quartz
in the section. Calcite shows good twinning and fills in between the
pebbles and detrital grains. Calcite has partially replaced some feldspar
grains. Calcite comprises 10% of the section. Copper is irregularly shap-
ed blebs interstitial to the grains and pebbles. There is approximately
10% in the section. There is earthy hematite dissemenated throughout
slide, but there is also some steel gray hematite grains that are less
then 0.2 mm. and are mainly scattered throughout the matrix. There is
3% of these steel gray grains in the section. The major type pebbles'
are the quartz feldspar porphyry. There is more bleaching around the
rims of the quartz feldspar porphyry then around the granophyre or fel-

site pebble. The pebble size averages 4 mm, with the quartz feldspar

67

porphyry on the average a little larger then the other two types. The
felsite pebbles have many small fractures in them that are filled with
copper. There is 25% quartz feldspar porphyry and approximately 3% fel-

site and grenoplyric.

- 1-18 - TAX

Sample 18 is from the first level and is 600 feet north of Number 6
shaft. The conglomerate at this point is 8 feet thick and the sample is
taken 4 feet above the footwall.

Epidote comprises 1% of the rock and is less than 0.02 mm. in size.
Epidote is interstitial to the pebble and large detrital grains. Hematite
masks the appearance of some of the epidote grains. The detrital grains
of feldspars have albite twinning and have a composition of approximately

An35. The size range is from 0.5 to 3.5 mm., and they comprise 10% of

the section. The grains are corroded around the edges and have dissemen-
ated hematite throughout most of the grains. There are detrital grains
of quartz and also secondary quartz interstitial to the other grains and
pebbles. Some of the larger quartz grains have a secondary overgrowth
around the edges. The size range is from 0.5 to 2.5 mm. and there is
approximately 15% in the section. Undulatory extinction is shown very
well with the detrital grains of quartz. There is less than 3% calcite
in the section. The crystals are small and are interstitial to the
pebbles and detrital grains. This is the only section where copper

and silver were found intergrown (Fig. 31). The silver surrounds the
copper and the blebs are rather large, up to 2 mm. There is approximately
5% copper in the section with silver only present around a few of the
blebs of copper. Steel gray grains of hematite are present in this sec-

tion and are less than 0.2 mm. in size. They are scattered throughout the

68

 

Figure 31 — Photomicrograph of copper - silver intergrowth
(half-breed). Reflected and transmitted light,
crossed nicols 50X.

69

matrix and make up approximately 3% of the section. Quartz feldspar por-
phyry makes up 40% of the section with granophyre and felsite making

up 15% and 5% respectively. The pebbles are subrounded and there is no
apparent bleaching of any of the pebbles. The average size of the peb-
'bles are 4 mm. and the quartz phenocrysts in the quartz feldspar porphyry
are larger and more abundant than the feldspar phenocrysts. The feld-
spar phenocrysts have a composition of An35. The main difference be-

tween sample 17 and 18 is the amount of copper. Sample 17 has a larger

amount of copper. There is also a smaller matrix in Sample 18.

.9.1.

Sample 1 is from the ninth level and is 65 feet north of Number 3 shaft.
The conglomerate at this point is 10 feet thick and the sample is taken
7 feet above the footwall.

There is less than 1% epidote in the section. The grains that are
present are replacing calcite. The detrital grains of feldspars have
albite twinning and have a composition of approximately An35. The grains
are corroded around the edges and have dissemenated hematite mainly
around the edges of the grains. The size range is 0.5 to 2 mm. and there
is 10% in the section. The detrital quartz grains are less than 1.5 mm.
and comprise 15% of the section. The grains are subrounded. Calcite
fills in fractures in the pebbles and in places it replaces feldspar
grains. It comprised 5% of the section. Copper comprises 1% of
the section and it mainly fills in fractures in the pebbles. There is
approximately 3% steel gray grains of hematite in the section and they
are 0.2 mm. in size. The section contains all quartz feldspar porphyry
pebbles with the pebbles ranging up to 15 mm. The quartz phenocrysts

are from 0.25 - 2 mm. and the feldspar phenocrysts range up to 3 mm.

70
The feldspar phenocrysts have a composition of An36. There is very

little bleaching of the pebbles.

-9-2-

Sample 2 is from the ninth level and is 2,000 feet north of Number 3
shaft. The conglomerate at this point is 7 feet thick and the sample is
taken 4 feet above the footwall.

Epidote comprised 5% of the section and the size range is from 0.1
to 0.3 mm. Epidote is replacing both the feldspar and calcite grains.
Epidote also replaces parts of pebbles. The detrital grains of feld-

spar have albite twinning and have a composition of approximately An35.

The average size of the grains is 0.5 mm. with the largest being 1 mm.
The grains are corroded around the edges and have dissemenated hematite
throughout most of the grains. The detrital grains of quartz are sub-
rounded and are less then 1.25 mm. in size. Detrital quartz comprises
10 % of the section. Secondary quartz is interstitial to pebbles and
grains but epidote and hematite mask the identification. Calcite

fills in between grains and pebbles. It comprises 3% of the section,
and in places is replacing feldspar grain and being replaced by epidote
itself. Copper comprises 5% of the section and it is interstitial to
pebbles and grains. The steel gray grains are 0.1 mm. in size. The
grains are in the matrix as well as the pebbles. When the grains are in
the pebbles they are broken up and have a band of hematite that de-
creases as you move away from the grain. The steel gray grains com-
prise 3% of the section. The quartz feldspar porphyry show good
bleaching rims. Figure 5 is a quartz feldspar porphyry pebble that
shows part of a bleached rim. The bleaching rim can go into some of

the pebbles 2 mm. The quartz feldspar porphyry comprise 20% of the

71

section and are 5.5 mm. in size. The granophyre pebbles range in size
from 0.5 to 5.5 mm. and comprise 20% of the section. There is a slight
bleaching rim on the granophyre pebbles. There are few felsite pebbles
and they average 1.2 mm. in size. The quartz phenocrysts are 2 mm. in
size and the feldspar phenocrysts are 0.5 mm. with a composition of An34.

There is no difference in the pebble size, type or composition bet-
ween Sample 1 or 2. The matrix of the two is also similar. The only
difference is the copper abundance and bleaching. In 9-2 there are
different layers where bleaching has taken place and where it has not.
Where the rock has not been bleached the pebble edges near the bleached
area are slightly bleached. The majority of Sample 1 is a reddish

brown color.

- 17-3 -

Sample 3 is from the seventeenth level and is 1,650 feet north of
Number 3 shaft. The conglomerate is 9 feet thick at this point and
the sample is taken 4 feet above the footwall.

There is 5% epidote in the section and in places it is replacing
calcite. Hematite masks the small grains of epidote, 0.02 mm. The
detrital grains of feldspars have faint albite twinning. Calcite is re-
placing parts of the grains and there is a large amount of hematite
throughout the grains, which masks the identification. The edges are
corroded and the feldspars comprise 5% of the section. Detrital grains
of quartz are subrounded and average 0.5 mm. in size. There is an over-
growth on most of the larger grains. Quartz comprises 5% of the section.
Calcite makes up 5% of the section and it is replacing feldspar grains
and being replaced by epidote. There are only traces of copper found

in the section. The steel gray grains of hematite are in the matrix

72

as well as the pebbles. The grains in the pebbles are larger 0.5 mm.
compared to 0.15 mm., and are broken up. There is a dark halo around
the edges of the broken up grains. The steel gray grains comprise 5%
of the section. The major pebble type is quartz feldspar porphyry. It
comprises 60% of the section and has slight bleaching rims. The size
range is 1.5 to 7 mm. The quartz phenocrysts range from 0.25 to 3 mm.
and the feldspar phenocrysts are less then 0.5 mm., with a composition
of An34. The other pebble type is felsite, which are more rounded than
the quartz feldspar porphyry and are less then 3 mm. in size. There is

no bleaching rim on these pebbles.

- 17-4 -

Sample four is from the 17 level and is 1,600 feet north of Number 3
shaft. The conglomerate is 9 feet thick and the sample is taken four feet
above the footwall.

Epidote comprises 5% of the section and it is hard to see individual
grains of epidote because hematite is dissemenated throughout them. Epi-
dote is replacing calcite and in places it is also replacing parts of
pebbles. The detrital grains of feldspars have a lot of hematite in
them and there is a faint albite twinning present. The edges of the
grains are corroded and they are 0.5 mm. in size. The detrital grains
of quartz are subrounded, have very few fractures and are less then 2 mm.
in size. There is secondary growth around some of the larger grains and
quartz comprises 10% of the section. The calcite is interstitial to the
grains and pebbles and comprises 3% of the section. The twinning is not
as distinct as in the previous sections. The copper is in the form of

dendritic crystals. It comprises 5% of the section and the dendritic

73

nature is consistent throughout. Copper fills in the fractures in some
of the felsite pebbles. The steel gray grains comprise 2% of the sec-
tion and they have a dark halo around the edges. There is very slight
bleaching of the quartz feldspar porphyry. The quartz feldspar porphyry
range in size from 0.5 to 5 mm., the felsite from 0.5 to 4 mm. and the
granophyre from 0.5 to 3 mm. The quartz feldspar porphyry make up

40% of the section and the felsite and granophyre each make up 10%.

The quartz phenocrysts are subrounded and are less than 2.5 mm. The
feldspar phenocrysts are less then 1.2 mm. and there are only a couple

phenocrysts.

- 17-5 -

Sample 5 is from the seventeenth level and is 1,470 feet north of
Number 3 shaft. The conglomerate is 7 feet thick and the sample is
taken 3 feet above the footwall.

Epidote comprises 5% of the section. In places it is replacing
the center of feldspar grains and it also replaces the majority
of the matrix. Hematite masks the appearance of the epidote. The det-
rital grains of feldspars have albite twinning and are less then 0.5 mm.
in size. The composition of the feldspars is An33 and they comprise 3%
of the section. The edges of the grains are corroded and hematite is
dissemenated evenly throughout them. The detrital grains of quartz
are subangular and there is a large variety of sizes ranging up to
2 mm. There is a secondary overgrowth on some of the larger grains and
quartz comprise 15% of the section. Calcite is similar to all other
sections but smaller in size because of the size of the matrix. It
comprises 2% of the section. Copper comprises 5% of the section and

forms irregular shaped blebs in the matrix. Some of the felsite pebbles

74

are fractured and copper fills in the fractures. The steel gray grains
of hematite are interstitial and in the pebbles. The grains in the
pebbles are broken up and have a dark halo around the edges. The grains
in the matrix and pebbles are both less than 1 mm. in size. The steel
gray grain comprise 3% of the section. All three types of pebbles are
present with quartz feldspar porphyry making up 30%, granophyre 20% and
felsite 15% of the section. There is a slight bleaching rim on the
quartz feldspar porphyry and granophyre pebbles. but it is more prom-
inent on the quartz feldspar porphyry. The felsite pebbles are not
bleached. There are very few feldspar phenocrysts. They are broken

up and show faint albite twinning. The average size is 1 mm. but a few
get up to 5 mm. The quartz phenocrysts are subrounded and range from

2 to 3 mm. in size.

- 17-6 -

Sample 6 is from the seventeenth level and is 1520 feet north of
Number 3 shaft. The sample is from the hanging wall.

There is less than 1% epidote in the section and where it is seen
it is replacing feldspar grain. The detrital grains of feldspar have
albite twinning and are being replaced by epidote and calcite. The
grains are more fractured and corroded then in other sections. The
grains are less than 1 mm. and comprise 15% of the section. Detrital
grains are subrounded and less then 1 mm. in size. There is not very
much secondary quartz in section and quartz comprises 20% of the section.
Calcite is replacing feldspar grains and is distributed evenly throughout
the section interstitial to pebbles and grains. It comprises 10% of
the section. There is only 2% copper in section and it is interstitial

to the grains and irregular in shape. There is a large amount of steel

75

gray grains of hematite, 10%, and they are less than 0.2 mm. in size.

Most grains are subrounded but a few are broken up and have dark halos
around them. There are four types of pebbles. The felsite pebbles are
the main type and comprise 25% of the section. They are subrounded and
have fractures that are filled in with copper. They are less than 1.5 mm.
in size. There is no apparent bleaching of any of the pebbles. The

next most abundant pebble type is the quartz feldspar porphyry which
comprise 5% of the section. The pebbles are less than 3 mm. in size

and the quartz and feldspar phenocrysts are less then 0.5 mm. in size.
Granophyre pebbles are subrounded, less then 2 mm. in size and comprise

5% of the section. There is one pebble that is trap rock. It has ophitic
texture of plagioclase laths and hematite surrounding them (Fig. 32).
There is calcite filling in some of the fractures in the feldspars.

The feldSpar grains are less than 0.5 mm., but a few range up to 2 mm.

There is a faint albite twinning on some of the grains.

- 17-7 -

Sample 7 is from the seventeenth level and is 769 feet north of
Number 3 shaft. The base of the conglomerate is not exposed but the con-
glomerate is at least 10 feet thick. The sample was taken 6 feet below
the hangwall. The massive characteristics of the wall rock did not
permit a hand sample to be collected. Small pieces of copper were
broken out of the matrix of the conglomerate.

The main difference between 3, 4, and 5 is the size of the pebbles
and matrix. Five has much larger pebbles and matrix along with more
copper and bleaching. Three is the least bleached of the three and four
has the smallest pebbles. Sample 6 is a piece of trap rock that also

has part of a conglomerate with it. There is a graduation from massive

76

 

Figure 32 - Photomicrograph of trap rock with ophitic
texture. Hematite is interstitial to feld-
spar laths. Transmitted light, uncrossed
nicols, 50 X.

77

trap rock to fragmented, with the fragmented having a deeper hematite
color. There are blebs of copper in the trap rock but as you move into
fragmented region there is an increase in copper. There is a band of

hematite at the junction between fragmented and massive trap rock.

- 27-19 -

.Sample 19 is from the twenty-seventh level and is right at the
Number 6 shaft. The only contact that is seen is the footwall contact
and the sample is 5 feet above this.

Epidote comprises 15% of the section and is less than 0.2 mm. in size.
It is replacing feldspar grains as well as calcite. Hematite masks the
appearance of grains the epidote is replacing. There are two different
sizes of detrital grains of feldspars. The larger ones range up to
0.75 mm. and the smaller ones are 0.1 to 0.05 mm. There is a faint
albite twinning and hematite is dissemenated through most of the grains.
The larger grains are rounded and the smaller ones are euhedral. There
is a "patchy" hematite in some of the grains where parts of the feld-
spar have hematite and other parts have none. There are two different
sizes of quartz grains, 1 mm. and 0.1 to 0.05 mm. The grains are sub-
rounded and comprise 10% of the section. Calcite is replacing feldspar
grains and epidote is replacing the calcite. It comprises 5% of the
section. Copper blebs are inside the granophyre as well as the felsite
pebbles. There is much more copper inside the pebbles than outside of
them. Copper comprise 7% of the section. The steel gray grains of
hematite are in the matrix as well as in the pebbles. The grains in
the matrix are 0.1 mm. and the ones in the pebbles are 0.5 mm. and are
broken up. There is no apparent bleaching of the pebbles. The quartz

feldspar porphyry range up to 5 mm. and the quartz phenocrysts range

- 27

78

up to 1 mm. and the feldspar phenocrysts up to 0.5 mm. There is a
faint albite twinning in the feldspar phenocrysts. The quartz feldspar
porphyry are rounded and comprise 25% of the section. The felsite and
granophyre pebbles are rounded, range from 1 to 2 mm. in size and each

comprise 10% of the section.

-20 -

Sample 20 is from the 27 level and is 350 feet south of number 6
shaft. The conglomerate is 9 feet thick and the sample is taken 4 feet
above the footwall.

The epidote in this section is just like in 19, where the epidote
is interstitial to the grains and pebbles and is evenly distributed
throughout the section. Epidote comprises 13% of the section. The
detrital grains of feldspar have "patchy" hematite and faint albite
twinning. Calcite and epidote replace the feldspar grains. The comp-
osition of the feldspar grains is An35 and the grains are less than 0.5
mm. The edges of the grains are extensively corroded and comprise 3%
of the section. The detrital quartz grains are subrounded and have corroded
edges. There is some secondary overgrowth on the larger grains and the
grain size is 1 mm. The quartz are not fractured and they comprise 10% of
the section. The calcite comprises 3% of the section and it is replacing
feldspars and being replaced by epidote. The calcite is mainly interstitial
to the grains and pebbles but it fills in fractures in a few quartz fel-
dspar porphyry. The copper comprise 3% of the section and it is found
as irregularly shaped blebs in the pebbles. The steel gray grains of
hematite are scattered randomly through the section and average 0.1 mm.

in size with a few ranging up to 0.7 mm. The grains are unaffected by

79

the epidote in the matrix. There is a halo around the grains that are in
the pebbles. There is less hematite immediately around the edges. The
steel gray grains comprise 3% of the section. The quartz feldspar por-
phyry pebbles are subrounded and less than 7.5 mm. a few range up to

14 mm. There is a slight bleaching around the edge. The quartz phen-
ocrysts are rounded and are 1.5 mm. in size. The feldspar phenocrysts
are fractured and have "patchy" hematite. The phenocrysts range up to
1.5 mm. The feldSpars comprise 35% of the section. The felsite pebbles
are subrounded and range up to 3 mm. There are fractures in the felsite
pebbles that are filled in with copper. There is a slight bleaching
around the edges of these pebbles and they comprise 20% of the section.
The granophyre pebbles are less than 2 mm. and show no bleaching. They
are rounded and comprise 15% of the section.

Both samples have graded bedding, but in 19 there is an errosioned
surface and then another graded bedding sequence on top of that. Epid-
otization is extensive in 20 whereas there is only one pebble in 19 that
was replaced. Copper is abundant in the bleached areas in both samples,
but there is a larger matrix in 20 and the copper blebs are larger.

Both samples have red rock areas but in 19 the pebbles are larger and
the color of the pebbles are darker. Overall the pebbles are smaller in

20, where the upper range is 1 cm. and in 19 it is up to 4.2 cm.

- 33-8 - DA
Sample 8 is from the thirty-third level and is 2165 feet north of
Number 3 shaft. The conglomerate is 6 feet thick and the sample is taken
1.5 feet above the footwall.

Epidotization is quite extensive, where it is replacing the majority

80

of the matrix. It surrounds the larger detrital grains of quartz and
feldspars. It comprises 15% of the section. In places it is replacing
calcite and hematite masks the appearance of the epidote in the matrix.
The larger detrital grains are only partially corroded around the edges.
Albite twinning is present and the composition is An35. There is
"patchy“ hematite in the feldspar grains. Calcite and epidote have re-
placed the smaller grains. The size range is from 0.15 to 0.6 mm. and
the feldspar grains comprise 2% of the section. The detrital grains of

quartz are subrounded and the larger grains have secondary overgrowth.

The grains range up to 2 mm. and comprise 10% of the section. There are
fractures in the rock that are filled with calcite. There is one vein
that is 3.5 mm. wide and extends across the section. There are islands
of epidote, feldspar and copper in this vein also. 0n the edges of this
vein and around most of the other calcite is epidote. Epodote is replacing
the calcite in places. Calcite comprises 15% of the section. Copper in
this section is mainly interstitial to the grains and pebbles. There are
a few blebs in a quartz feldspar porphyry pebble. Copper is irregularly
shaped and comprise 7% of all section. There is less than 2% steel gray
grains of hematite in the section. The size range is from 0.2 to 1 mm.
The smaller grains are subrounded and are not broken up, whereas the
larger ones are broken up and have a halo around them. The quartz
feldspar porphyry show bleaching rims up to 1 mm. into the pebbles.

The pebbles range up to 10 mm. with 2 mm. quartz phenocrysts. The
feldspar phenocrysts have albite twinning and have "patchy" hematite.

The composition is An35 and they are less then 1.5 mm. The granophyre
pebbles are round, 3 mm. in size, show no bleaching and comprise 10% of
the section. The felsite pebbles are subrounded, 2 mm. in size, show no

bleaching and comprise 5% of the section.

81

- 33-9 -

Sample 9 is from the thirty-third level and is 2170 feet north of
Number 3 shaft. The conglomerate is 6 feet thick and the sample is taken
1.5 feet above the footwall.

Epidotization is extensive. The smaller pebbles have been completely
epidotized, the epidote has partially replaced the calcite and feldspar
grains. In places there is epidote that has dissemenated hematite through-
out and other crystals of epidote are completely clear of the hematite.
Epidote comprises 25% of the section. The detrital grains of feldspar
are corroded around the edges and there is a faint albite twinning. The
feldspar comprise 2% of the section and are less than 0.5 mm. in size.

The detrital quartz grains are subrounded and range up to 1 mm. in size.
There is secondary overgrowth on some of the larger grains and the quartz
comprises 10% of the section. Calcite is interstitial to the pebbles and
grains. Epidote is replacing parts of the calcite. Calcite comprises 10%
of the section. Copper is small blebs, less than 0.1 mm., in the different
pebbles. It comprises 3% of the section. The steel gray grains of hematite
are in the matrix and some are in the pebbles. The larger grains are in the
pebbles and are broken up. The average size is 0.1 mm. and the grains com-
prise 1% of the section. The pebbles have lost most of their hematite and
are much lighter in color than in the other sections. The quartz feldspar
porphyry are 4 mm. with quartz phenocrysts ranging up to 1 mm. The felds-
par phenocryst, now replaced with epidote and calcite, were 0.5 mm. in

size. The felsite pebbles are rounded and less than 1 mm. in size. The

quartz feldspar porphyry comprises 30% of the section and the felsite 5%.

- 33-10 -
Sample 10 is from the thirty-third level and is 1555 feet north of

82

Number 3 shaft. The conglomerate is 10 feet thick and the sample is taken
5 feet above the footwall.

Epidotization is not as dominant as in 9, but it still fills in a
good percentage of the matrix. It is replacing calcite and feldspars.
Epidote comprise 10% of the section. Half of the epidote crystals are
euhedral and clear of hematite and the other half are masked by the dis-
semenated hematite in them. The detrital grains of feldspar have faint
albite twinning and a composition of An34. Most of the grains are less

than 0.3 mm. but a few range up to 0.7 mm. "Patchy" hematite is in the

larger grains and the feldspar comprise 7% of the section. The detrital
grains of quartz are less than 1 mm., subrounded with corroded edges and
no fractures. There is secondary overgrowth on some of the larger grains.
The quartz comprises 15% of the section. Calcite is broken up and inter-
stitial to the pebbles and grains. In places it replaces feldspar grains
and it comprises 3% of the section. The c0pper is irregularly shaped
blebs and comprise 3% of the section. Some of the copper fills in
fractures on the edges of some pebbles. There are steel gray grains

of hematite in the matrix and pebbles. The grains in the pebbles range
up to 2 mm. and are usually broken up. There is a halo around the grains
where there is less hematite in the pebbles. The smaller steel gray grains
in the pebbles are unaffected. The grains in the matrix are less than
0.25 mm. The steel gray grains comprise 5% of the section. There is
slight bleaching of the quartz feldspar porphyry pebble. The pebbles
range up to 6 mm. The feldspar phenocrysts have "patchy" hematite,

are fractured, epidote replacement, copper fills in the fractures, and
have faint albite twinning. The composition of the phenocrysts are An37.
There are a few rounded nonbleached felsite pebbles that are less then

2 mm. in size. The quartz feldspar porphyry comprise 45% of the section

83

and the felsite 5%.

- 33-11 -

Sample 11 is from the thirty-third level and is 610 feet north of
Number 3 shaft. The conglomerate is 8 feet thick and the sample is taken
5 feet above the footwall.

Epidotization is extensive. Epidote has replaced most of the smaller
grains in the matrix and surrounds the larger grains and pebbles. Epidote
also replaces calcite. Hematite masks some of the epidote but there are
some euhedral crystals of epidote intruding into some detrital grain
boundaries or pebble edges. The epidote comprises 12% of the section. The
detrital grains of feldspar make up less than 1% of the section and are
less than 0.2 mm. in size. There is albite twinning on some grains and the
edges are corroded. The detrital grains of quartz are 1.1 mm. and comprise
3% of the section. The quartz grains are not fractured and there is
secondary overgrowth on some of the larger grains. Calcite crystals
are quite large and are corroded around the edges by epidote. Calcite
comprise 11% of the section. There is 2% copper, and it is irregularly
shaped blebs as inclusions in the pebbles. The steel gray grains of
hematite comprise 3% of the section and are scattered throughout the
matrix and some larger grains are included in a few pebbles. Most of
the hematite has been removed from the pebbles. The pebbles are sub-
rounded. The quartz feldspar porphyry pebbles are 7 mm. and comprise
35% of the section. The granophyre pebbles are more rounded and less
than 2.5 mm. They comprise 5% of the section. The felsite pebbles
are less than 2.5 mm. and comprise 15% of the section. The quartz
phenocrysts are less than 2.5 mm. Epidote replaces most of the feld-

spar phenocrysts.

84

- 33-12 -

Sample 12 is from the thirty-third level and is 795 feet south of
Number 3 shaft. The hanging wall is not visible and the sample is 5
feet above the footwall.

Epidote is replacing feldspar phenocrysts. In places the epidote
is surrounding calcite and intrudes in the fractures. The epidote com-
prises 5% of the section. The detrital grains of feldspars have albite
twinning and some have patchy hematite (Fig. 4). There is also dendritic
copper associated with the feldspar grains. The grains are less than
0.75 mm. and comprise 5% of the section. The larger detrital grains of
quartz show secondary overgrowth. The grains are subrounded and have
corroded edges. The grains are less than 0.9 mm. and comprise 5% of the
section. Calcite is being replaced by epidote and in places dendritic
copper is included in the calcite (Fig. 33). Copper forms good dendritic
patterns. Copper is interstitial to the grains and pebbles, and is also
included in the pebbles and some grains. Copper comprises 5% of the
section. There is less than 1% steel gray grains of hematite in the
section. There is albitization present in the section. Figure 34 shows
a feldspar phenocryst that is at the edge of a pebble. There is an
overgrowth present and hematite separates the two parts of the crystals.
The albite twinning is not continuous from one side of the crystal to
the other. The albitized phenocrysts is 2.5 mm. in size. The quartz
feldspar porphyry is less than 5 mm. and comprises 50% of the section.
The quartz phenocrysts are round and less then 2 mm. in size. There is
a 60/40 ratio of quartz to feldspar phenocrysts. The felsite pebbles

are rounded, less than 2 mm. in size and comprise 20% of the section.

85

 

Figure 33 - Photomicrograph of dendritic copper in calcite.
Reflected and transmitted light, crossed nicols

86

 

Figure 34 - Photomicrograph of secondary overgrowth on
feldspar phenocryst. Hematite interface.
Transmitted light, crossed nicols 50 X.

87

--33-13 -

Sample 13 is from the thirty-third level and is 600 feet south of the
Number 3 shaft. This is a sample from the hanging wall. There is a ophitic
texture where pyroxene and laths of plagioclase are interlocked. The
chlorite masses are larger (0.5 mm.) than the laths of plagioclase and
fractured irregularly shaped pyroxene (0.15 mm.). There is only one
bleb of copper present, which is probably in the fracture which the section
cuts. There is 35% chlorite, 10% hematite, 35% plagioclase, and 15% pyr-
oxene. The hanging wall has many fractures that are filled with copper.
There are also slicken slides present on some of the fractured surfaces.
The rock is a massive greenish black color. There are microfractures

in hand samples that contain copper.

- 33—14 -

Sample 14 is from the thirty-fourth level and is 580 feet south of
Number 3 shaft. The hanging wall is not visible and the sample is taken
5 feet above footwall.

The epidote in this section is masked by hematite and the only thing
that can be seen is the epidote color. There is possibly some Clinozoisite
included in one of the pebbles (Fig. 35). It has high relief and long
fiborous crystals clustered in a group. The epidote comprises 5% of the
section. There are small detrital grains of feldspars that are partially
replaced by epidote and have albite twinning. The composition is An34 and
the grains are less then 0.3 mm. The feldspar grains comprise 2% of the
section. There are many small grains of quartz in the matrix, with the
larger ones ranging up to 0.4 mm. There is secondary overgrowth on some

of the larger grains and the quartz grains comprise 3% of the section.

88

 

Figure 35 - Photomicrograph of Clinozoisite.
Transmitted light, crossed nicols 50 X.

89

Calcite is not abundant, less than 2%, and it fills in small spaces in the
matrix. It also fills in a few fractures in some pebbles. There are little
blebs of copper scattered throughout the slide but the majority is contained
in the pebbles. The capper comprise 5% of the section. There are steel gray
grains of hematite in the matrix which are less than 0.15 mm. in size.

The grains in the pebbles are larger, 1.2 mm., and broken up. There is a
dark halo around the edges of these broken up grains. The steel gray grains
comprise 5% of the section. The quartz feldspar phenocrysts are subrounded
and are at less then 6 mm. in size. Bleaching is not very extensive and is only
on the very edges of the pebbles. Quartz feldspar porphyry comprises 60%

of the section and felsite pebbles make up 10%. The quartz phenocrysts
range up to 2 mm. and the feldspar phenocrysts range up to 2.2 mm. and

have "patchy" hematite. There are two different color zones in the rock.
There is a bleaching zone where most of the pebbles have been completely
bleached and there is a zone where none have been bleached. A few of the
red pebbles that are near the bleached zone have their edges, that are
toward the bleached zone, bleached. Copper is present mainly inter-

stitial to the pebbles in the bleached area.

- 35-15 —

Sample 15 is from the thirty-fifth level and is 120 feet south of
Number 3 shaft. The conglomerate is 8.5 feet thick and the sample is taken
3.5 feet above the footwall.

Epidization is quite extensive. Epidote has replaced some pebbles
and the hematite remains and masks the appearance of the epidote. Epidote
comprises 20% of the section. There is very little matrix and very few
detrital grains. There are a few remnnants of grains in the epidote

clusters. There is no apparent calcite in this section. Copper is dis-

9O

tributed throughout the section, interstitial to the pebbles as well as
blebs included in the pebbles. Copper comprise 25% of the section. Most
of the earthy hematite has been removed from the pebbles and there was
only one steel gray grain of hematite found in a pebble. The quartz
feldspar porphyry are subrounded and less than 5 mm. in size. Figure 36
shows relationship of quartz feldspar porphyry pebble, epidote and copper.
The quartz phenocrysts are less then 1.2 mm. and the feldspar phenocrysts
have been replaced by epidote. The quartz feldspar porphyry comprise 40%
of the section and the felsite pebbles make up 10%. The felsite pebbles
are less than 2.5 and have more hematite in them compared to the quartz

feldspar porphyry.

- 35-21 -
Sample 21 is from the thirty-fifth level and is 1810 feet north of
Number 3 shaft. The conglomerate is 2.8 feet thick and the sample is taken
1.8 feet above the footwall. (No polished section was prepared for the
sample). The sample is not bleached and calcite fills in between the
pebbles. Copper is not abundant, less than 1%.. The pebble size is 5 mm.

and there is very little matrix.

- 35-22 -
Sample 22 is from the thirty-fifth level and is 1775 feet north of
Number 3 shaft. The conglomerite is 4.4 feet thick and the sample is
taken 2 feet above the footwall.
Epidote is present throughout but it has not replaced everything as it
did in 15. There are a few pebbles that have been completely replaced.
Epidote comprises 15% of the section. The detrital grains of feldspars

have a faint albite twinning and epidote partially replaces the grains.

91

 

Figure 36 - Photomicrograph of copper, epidote and felsite
pebble. Reflected and transmitted light, cross-
nicols 50 X.

92

There is "patchy" hematite and the grains range up to 1 mm. The com-
position is An33 and the grains comprise 5% of the section. The quartz
grains are subrounded, have corroded edges, are less than 2.5 mm. and

show secondary overgrowth on the larger grains. Majority of grains are

less than 0.5 mm. and they comprise 10% of the section. Calcite is scattered
irregularly throughout section. It is in clusters and epidote is usually
surrounding and intruding the calcite. Calcite comprises 5% of the section.
There is copper both interstitial to and as blebs in the pebbles. The cop-
per is evenly distributed through section and it comprise 5% of the section.
The steel gray grains of hematite are mainly in one large pebble. They
range up to 0.1 mm. and comprise 3% of the section. Figure 6 shows a steel
gray grain of hematite that is in a pebble. The grain shows a halo

around the edges where the hematite has been removed from the pebbles.

The quartz feldspar porphyry pebbles are subrounded with a few quartz or
feldspar phenocrysts. The quartz phenocrysts are less than 1 mm. and the
feldspar phenocryst are less than 0.5 mm. The quartz feldspar porphyry
pebbles are 5 mm. in size and show bleaching rims. The quartz feldspar
porphyry comprises 35% of the section. The felsite and granophyre pebbles
show slight bleaching and are both less than 2 mm. in size. The felsite

granophyric pebbles each comprise 7% of the section.

- 35-23 -
Sample 23 is from the thirty-fifth level and is 1740 feet north of
Number 3 shaft. The conglomerate is 5 feet thick and the sample is taken
2 feet above the footwall.
Clinozoisite, just like in Sample 14 (Fig. 35), is present in a pebble.
There are only 4 pebbles that have been completely epiditized. There is

very little matrix in this sample. Epidote comprise 10% of the section.

93

The detrital grains of feldspars have faint albite twinning and are less
than 3 mm. in size. The composition is An35 and the grains comprise 2%

of the section. The quartz grains are subrounded and have corroded edges.
They are less than 3 mm. in size and comprise 5% of the section. There

is a large amount of calcite interstitial to the pebbles and grains.
Calcite comprises 15% of the section. Copper is mainly in a few pebbles

as irregularly shaped blebs. Copper in one pebble is just around the mar-
gins as if it is included in a secondary growth. Copper comprises 5%

of the section. There are steel gray grains of hematite in the matrix

and in the pebbles. The grains in the pebbles have a dark halo around
their edges. The steel gray grains comprise 5% of the section. The quartz
feldspar porphyry are subrounded and range up to 6 mm. The quartz phen-
ocrysts are less than 1.2 mm. and there is very few feldspar phenocrysts
because they have been replaced by epidote. The quartz feldspar porphyry
comprise 40% of the section. The felsite pebbles are rounded and are less
than 2.2 mm. They comprise 15% of the section. In dealing with the quartz
feldspar porphyry there are different types. Some have a larger grain

size for a groundmass and the ones with the larger grains are also more

altered and have a dirty appearance.

- 35-24 -
Sample 24 is from the thirty-fifth level and is 1705 feet north of
Number 3 shaft. The conglomerate is 5.4 feet thick and the sample is taken
2 feet above the footwall. (No polished section was prepared for the
sample). There are two different sizes of pebbles. One group averages
1.5 cm. and the others are less than 0.5 cm. Epidote replaces the mat-
rix but it has not greatly affected the pebbles. Bleaching is around

the edges of a few pebbles and there is 10% copper in the sample.

94

— 35-25 -

Sample 25 is from the thirty-fifth level and is 1670 north of
Number 3 shaft. The conglomerate is 7.3 feet thick and the same is
2 feet above the footwall.

Epidization is extensive and epidote replaces parts and in some
cases all of the pebbles. The epidote comprises 25% of the section. The
detrital grains of feldspar have been totally replaced by epidote. The
detrital grains of quartz are subrounded and have corroded edges. There
is a secondary overgrowth on the larger quartz grains. The grains range up to
2.5 mm. and comprise 5% of the section. Calcite was not detected in the
section. The copper is scattered throughout the pebbles as small blebs,
less than 0.2 mm. There is no preferred pebble type for the copper, and
the copper comprises 5% of the section. The steel gray grains are less
than 0.05 mm. and comprise 1% of the section. The pebbles are irregular
in shape with no bleaching. The quartz feldspar porphyry pebbles have
few feldspar phenocrysts and the quartz phenocrysts range up to 2 mm.
The quartz feldspar porphyry pebbles have the least amount of copper and
epidote whereas the granophyre pebbles have the most of each. The felsite
pebbles contain some copper and comprise 10% of the section. The quartz
feldspar porphyry pebbles comprise 10% of the section and the granophyric
40%. In some of the pebbles, the outside margin contains copper and has a
granophyric type texture whereas the center has a felsitic texture. There

are also different size granophyric textures.

- 35-26 -
Sample 26 is from the thirty-fifth level and is 1635 feet north of
Number 3 shaft. The conglomerate is 6.5 feet thick and the sample is taken

4 feet above the footwall.

95

The epidote has completly replaced a few of the pebbles but the
majority of the epidote is scattered through the matrix. There are clusters
of epidote grains that have little hematite and are euhedral. The epidote
comprises 20% of the section. The feldspar grains are being replaced by
epidote and they are extensively corroded at the edges. There is a faint
albite twinning and the composition is An . The grains range up to 1 mm.
in size and comprise 5% of the section. The quartz grains are subrounded
and have corroded edges. The grains are less than 2 mm., but a few range
up to 3.5 mm. The larger grains have secondary overgrowth on them. The
quartz grains comprise 5% of the section. Calcite is interstitial to the
pebbles and grains. It is extensively fractured and comprise 2% of the
section. Copper is mainly as blebs interstitial to the grains and pebbles.
The copper comprises 5% of the section. The steel gray grains of hematite
are scattered throughout the matrix and are also present in the pebbles.
Most grains are less than 0.1 mm. but a few range up to 2 mm. The larger
grains are broken up around the edges. The grains comprise 3% of the section.
There is one large quartz feldspar porphyry pebble which is at least
10 mm. in size with quartz and feldspar phenocrysts ranging up to 2 mm. The
feldspar phenocrysts have a albite twinning and a composition of An35.
There is a large bleaching rim on this pebble, 2 mm. One of the feldspar
phenocrysts is being altered from the center outward. The quartz feld-
spar porphyry pebbles comprise 45% of the section and they all show some
degree of bleaching. The average size of the quartz feldspar porphyry
is 3 mm. Hematite masks the other smaller pebbles, 2 mm. and they all are

subrounded and show a slight bleaching.

- 35-27 -
Sample 27 is from the thirty-fifth level and is 1600 feet north of

96

Number 3 shaft. The conglomerate is 6.5 feet thick and the sample is
taken 5.5 feet above the footwall.

Epidization is extensive and recrystalization of the pebbles and detrital
grains is present. There are secondary euhedral crystals that are inclu-
sions or just intruding the edges of grains and pebbles. There was no
detrital feldspars found in the section. The detrital quartz grains are
subrounded and less than 1 mm. in size. There is secondary overgrowth
on the quartz grains and they comprise 3% of the section. Copper is inter-
stitial to the grains and pebbles. In places it forms the whole matrix
between the pebbles. Copper comprises 15% of the section. There is very
little hematite left in the pebbles. Steel gray grains of hematite are
scattered throughout the section and under reflected light are related
mainly with the copper. The grains comprise 1% of the section. Some of
the pebbles are greater than 20 mm. but the majority average 2 mm. In
looking at the large quartz feldspar porphyry pebbles there are remnants
of feldspar phenocrysts that are being replaced either by epidote or
copper. Albite twinning is still present on a few of the phenocrysts.
There is recrystallization of the groundmass in the pebbles and the quartz
grains are larger than in other sections. The quartz phenocrysts have
a halo around them (Fig. 37). The recrystallizing quartz phenocrysts
range up to 5 mm. and the groundmass up to 0.5 mm. The quartz feldspar

porphyry comprise 45% of the section.

- 35-28-
Sample 28 is from the thirty-fifth level and is 1565 feet north of
Number 3 shaft. The conglomerate is 7.5 feet thick and the sample is
taken 1.5 feet above the footwall.

In comparing this with Sample 27 there is a less degree of epidization

97

 

Figure 37 - Photomicrograph of recrystallizing quartz
phenocryst. Transmitted light, crossed
nicols 50 X.

98

but it is still completely through the section. There are more remnants

of feldspar. Phenocrysts and recrystallization of the groundmass of the
pebbles similar to 27. There are no halos around the quartz grains and

the epidote comprise 20% of the section. There are no detrital feldspar
grains in the matrix. There are subrounded quartz grains that are less than
1 mm. They comprise 2% of the section. Calcite is present throughout the
section and the calcite is replacing the feldspar phenocrysts. Calcite is
present in the matrix and also in the pebbles. Calcite comprises 5% of

the section. There are a few crystals of chlorite. They show the char-

 

acteristic "Berlin Blue" of penninite, (Fig. 38). The chlorite comprises
5% of the section. Copper is quite dominant interstitial to the grains
where in places it replaces the whole matrix. It is also included in
pebbles as small blebs. Copper comprises 15% of the section. There

is very little hematite left in the pebbles. There is less than 1%

steel gray grains of hematite. They are scattered throughout the matrix
and are less than 0.05 mm. in size. The only type of pebble present is

the quartz feldspar porphyry. The pebbles are usually less than 2.5 mm.
but a few range up to 4 mm. The quartz phenocrysts are 2 mm. and rounded.
The feldspar phenocrysts have faint albite twinning and are less than 1 mm.

in size. The composition of the phenocrysts are An37, ’

- 35-29 -
Sample 29 is from the thirty-fifth level and is 1530 feet north of
Number 3 shaft. The conglomerate is 6.2 feet thick and the sample is taken
2.5 feet above the footwall.
There is very little epidote, less than 5% in the section. There are
a couple of pebbles that are partially replaced by epidote, but epidote

is mainly in the matrix masked by hematite sometimes and replacing calcite

99

 

Figure 38 - Photomicrograph of penninite, epidote and quartz
grains. Transmitted light, crossed nocols 50 X.

100

in other places. The detrital feldspar is mainly 0.3 mm., but a few range
up to 1 mm. Albite twinning is present and "patchy" hematite is present
in a few grains. The composition of the feldspars are An35. The feld-
spars comprise 5% of the section. The quartz grains are subrounded, range
up to 2 mm. and have secondary overgrowth on most of the larger grains. The
quartz comprises 10% of the section. The calcite is found interstitial

to the grains and pebbles. In places epidote replaces the calcite and it
comprises 5% of the section. Chlorite is fiborous and "Berlin Blue". It
comprises less than 1% of the section. Copper is interstitial to the
pebbles and grains. Copper comprises 5% of the section. The steel gray
grains of hematite range up to 2 mm. and are in the matrix and pebbles.
The grains in the pebbles are broken up and have dark halos around them.
The steel gray grains comprise 5% of the section. The pebbles all show
slight bleaching. Quartz feldspar porphyry range up to 8 mm. in size
while the granophyric and felsite pebbles range up to 3 mm. There are
very few quartz or feldspar phenocrysts. They range up to 0.5 mm. and

the feldspar phenocrysts are being replaced by epidote. Each pebble

type makes up 20% of the section.

- 35—30 -

Sample 30 is from the thirty-fifth level and is 1495 feet north of
Number 3. The conglomerate is 7 feet thick and the sample is taken 5 feet
above the footwall.

Epidization is minor, and there are only a few pebbles that have
been completely replaced. Epidote is mainly interstitial to the pebble
and grains. It comprises 13% of the section. The detrital grains of
quartz range up to 0.6 mm. in size and the larger grains have secondary

overgrowth on them. The quartz comprise 10% of the section. Calcite is

101

interstitial to pebbles and grains. It is being replaced by epidote

and calcite comprises 8% of the section. Copper is included in pebbles
as little blebs less than 0.1 mm. in size. The copper comprises 6%

of the section. The larger steel gray grains of hematite (0.5 mm.)

are in the pebbles and the smaller grains (0.1 mm.) are scattered through-
out the matrix. The grains in the pebbles are broken up and have dark
halos around them. The grains comprise 4% of the section. There is a
slight bleaching of the pebbles. The main type of pebble is the quartz
feldspar porphyry. It is less than 4 mm. and the quartz phenocrysts are
subrounded and 2 mm. in size. The feldspar pheoncrysts show albite twin-
ning and some "patchy" hematite. The quartz feldspar porphyry comprise
40% of the section. The felsite and granophyric pebbles are less than
1.5 mm. in size and both together comprise 10% of the section. Figure

39 shows a pebble that is being replaced by epidote. The matrix is not

being replaced and there is a hematite interface between the two areas.

- 35-31 -

Sample 31 is from the thirty-fifth level and is 1460 feet north of
Number 3 shaft. The conglomerate is 5 feet thick and the sample is taken
2 feet above the footwall.

Epidote is interstitial to the pebbles and replaces a few pebbles.
Epidote comprises 10% of the section. The detrital grains of feldspar
have, faint albite twinning and a composition of An35. There is "patchy"
hematite in the larger grains (1 mm.) and the feldspar grains comprise
5% of the section. The detrital grains of quartz range up to 2.5 mm. and
the larger ones have a secondary overgrowth. The quartz comprise 10%

of the section. Calcite is broken up and is interstitial to the pebbles

102

 

Figure 39 - Photomicrograph of epidotized pebbles, and
matrix. Interface of hematite. Transmitted
light, crossed nicols 50 X.

103

of grains. Epidote replaces calcite and the calcite comprises 2% of the
section. The copper is interstitial to the pebbles and grains. It fills
in fractures in the felsite pebbles. The copper comprises 5% of the
section. There are steel gray grains of hematite in the matrix and in

a few pebbles. When the grains are in the pebbles they are broken up

and have a dark halo around the edges of the steel gray grain. The

steel gray grains comprise 3% of the section. The quartz feldspar
porphyry show slight recrystallization. The groundmass is enlarged

and there are slight halos starting to form around the quartz. The
pebbles range up to 4 mm. in size and the quartz phenocrysts are rounded
and less then 1.5 mm. in size. The feldspar phenocrysts have faint albite
twinning and are less than 1.2 mm. The felsite pebbles are subrounded
and less than 3 mm. in size. There are fractures in them that are filled

in with copper. The felsite pebbles comprise 10% of the section.

- 35-32 -
Sample 32 is from the thirty-fifth level and is 1425 feet north of
Number 3 shaft. The conglomerate is 6.3 feet thick and the sample is taken
from 1.5 feet above the footwall. The massive characteristics of the wall
rock did not permit a hand sample to be collected. Small pieces of copper

were broken out of the matrix of the conglomerate.

- 35-33 -
Sample 34 is from the thirty-fifth level and is 100 feet north of
Number 3 shaft. The hanging wall is not visible and the sample is 2 feet
above the footwall.
Epidote is not abundant. There are no pebbles replaced by epidote

and the epidote is scattered randomly throughout the matrix. The epidote

 

104

comprises 3% of the section. The detrital grains of feldspar have albite
twinning with secondary overgrowth on some of the grains. The composition

is An35, with a size range up to 2 mm. The feldspars comprise less than

3% of the section. The quartz is subrounded, fractured and less then

0.5 mm. in size. The quartz grains comprise 3% of the section. Calcite is
interstitial to the pebbles and grains. It comprises less than 2% of

the section. Copper is interstitial to pebbles and grians. Copper
comprises 5% of the section. The steel gray grains of hematite are

less than 0.2 mm. The grains are in the matrix as well as the pebbles.

The grains in the pebbles have dark halos around their edges. The steel
gray grains comprise 2% of the section. The quartz feldspar porphyry
pebbles have slightly bleached rims. The pebbles range up to 15 mm. The
feldspar phenocrysts are less than 2.5 mm., have faint albite twinning

and have a composition of An35. There is "patchy" hematite in a few of

the larger feldspar phenocrysts. The quartz grains are rounded and less
than 2 mm. in size. The quartz feldspar porphyry comprise 70% of the
section. There are a few granophyric and felsite pebbles. They are less
than 1 mm. in size.

Samples 15, 25 and 27 have almost completely been epidotized. Sample
25 has the smallest grain and pebble size, while 27 has the larger grain
and pebble size of the three samples. Copper is prominent in samples
34, 31, 28, 15 and 27. Excluding the epidotized samples, in order of
greatest bleaching are 34, 26, 28, 30, 24, 31, 22, 23, 29, and 21. In

hand sample calcite is visible only in Samples 31,30 and 22.

- 50-16 -
Sample 16 is from the fiftieth level and is 395 feet north of Number 6

105

shaft. The conglomerate is 5 feet thick and the sample is taken 2.5
feet above the footwall. The sample has a large amount of epidote and
the epidote is a lighter olive green compared to other samples from the
mine. The pebbles range up to 10 cm. in size and bleaching is not

extensive.

‘ APPENDIX B
EQUIPMENT SETUP AND CORRELATION
COEFFICIENTS FOR WORKING CURE DATA

Fe

Ca

Na

Zn

MR Scale
1 1
1 5
2 5
2 l
2 2
2 5
1 2
2 5

106

ATOMIC.ABSORPTION UNIT

WL Range 'mA Slit Sensitivity

286.4
247.7
279

209.7
209.7
209.7
292.8

213.3

NEUTRON.ACTIVATION

Gain 8, Ch.# 512, 200 sec., Merory display 100K, Display gain

UV

UV

VIS

VIS

VIS

16
30
3O
15
15
15

8

15

4

3

0.007
0.12
0.055
0.08
0.08
0.08
0.015

0.018

ug/ml
ug/ml
ug/ml
ug/ml
ug/ml
ug/ml
ug/ml
ug/ml

Linearity

o . 5ug/m1

3 ug/ml
7 ug/ml
7 ug/ml

7 ug/md

1 ug/ml

5x, Holder in 5 front (approximately one inch away from GeLi

detector), and correlation coefficient is 0.99997.

FLAME EMISSION SPECTROMETRY

The correlation coefficient is 0.99398.

CC
0.99980
0.99835
0.99890
0.99486
0.99799
0.99847
0.99936

0.99980