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ABSTRACT

"FRAMBOIDAL" CHALCOCITE FROM WHITE PINE, MICHIGAN

BY

Nancy Alyanak

Chalcocite with nuclei occurs throughout the mineralized zone
at White Pine, Michigan. They are more abundant in the well-laminated,
black, fine-grained lithologies than in the massive lithologies. The
nuclei are similar to the framboidal texture commonly observed in
pyrite associated with sediments. The chalcocite nuclei can only be
observed after the polished section has been etched and stained with
a weak hydrochloric acid and potassium ferrocyanide solution--a stain
very sensitive to low concentrations of iron.

The scanning electron microsc0pe shows that microcysts at
least as small as .2 microns are found in each nucleus. Microcrysts
within a well-defined circular or elliptical nucleus are densely
packed, with a few scattered microcrysts in the surrounding grain.
However, the microcrysts are less densely packed where the nucleus
occupies the entire grain. All gradations between the dispersed and
densely packed microcrysts are found.

In polished section these nuclei are either circular, ellip-

tical or conform to the shape of the grain, with a median circular

Nancy Alyanak

diameter of four microns and a median elliptical long axis of eight
microns. It is concluded that the framboidal cores are biaxial pro-
late ellipsoids. Using Wicksell's method, the size frequency distri—
bution for the minor axis of the framboids was calculated and then
compared to known size frequency distributions of framboidal pyrite.
Two origins are possible for the framboidal chalcocite:

(1) replacement of framboidal pyrite, and (2) formation of primary
framboidal chalcocite. To evaluate the first alternative the pyrite
zone and the fringe zone were examined for framboids like those in

the chalcocite. None were found, supporting the second model.

"FRAMBOIDAL" CHALCOCITE FROM WHITE PINE, MICHIGAN

By

Nancy Alyanak

A THESIS

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

MASTER OF SCIENCE

Department of Geology

1973

ACKNOWLEDGMENTS

I extend my appreciation and thanks to the following people:

Dr. T. A. Vogel, Mr. V. E. Shull, Dr. H. B. Stonehouse, and

Dr. R. L. Anstey.

ii

TABLE OF CONTENTS

Page
LIST OF FIGURES . . . . . . . . . . . . . . . iv
INTRODUCTION . . . . . . . . . . . . . . . . 1
GEOLOGIC SETTING . . . . . . . . . . . . . . . 3
METHOD OF OBSERVATION . . . . . . . . . . . . . S
SHAPE AND STRUCTURE . . . . . . . . . . . . . . 6
COMPARISON WITH OTHER FRAMBOIDS . . . . . . . . . . 8
SIZE FREQUENCY DISTRIBUTION . . . . . . . . . . . 10
LITHOLOGIC DISTRIBUTION . . . . . . . . . . . . . 12
COMPOSITION . . . . . . . . . . . . . . . . . l3
ORIGIN OF FRAMBOIDS . . . . . . . . . . . . . . 15
DISCUSSION . . . . . . . . . . . . . . . . . 17
CONCLUSION . . . . . . . . . . . . . . . . . 20
REFERENCES . . . . . . . . . . . . . . . . . 21

iii

Figure

10a.

10b.

10c.

10d.

LIST OF FIGURES

Lithologic column at White Pine .

Oval and circular framboidal cores in stained
grains under reflected light (1 cm = 10 u)

SEM photos of two cores (1 cm = 10 u)
Detail of cores in Fig. 3 (1 cm = .5 u) . . .

Especially high relief in core. Compare to
those in Fig. 3 (1 cm = 2 u) . . . . . .

Framboidal core plucked out during
preparation (1 cm = l u) . . . . . . .

Core that occupies most of its grain (microprobe
photO) O O O O O O O O O O O O 0

Core that almost occupies its grain (microprobe
photO) O O O O O O O O O O O 0

Size frequency distribution of chalcocite
framboidal cores . . . . . . . . .

Microprobe traverse of elliptical framboidal
core for Fe, K, and C (counts per second
are given) . . . . . . . . . . . .

Microprobe traverse of circular framboidal
core shown in Fig. 2 for Fe . . . . .

Microprobe traverse of circular framboidal
core for Fe . . . . . . . . . .

Microprobe traverse of circular framboidal

core for Fe, C, and K (counts per second
are given) . . . . . . . . . . . .

iv

Page

23

24
25

26

27

27

28

29

30

31

32

33

34

Figure

lOe. MicrOprobe traverse of framboidal core shown in
Fig. 8 for Fe and C (counts per second are
given)

11. Euhedral microcrysts in pyrite framboid
(1 cm = 1 u) . . . . . . .

12. Wedge shaped microcrysts in pyrite framboid
(1 cm = l u) . . . . .

Page

35

36

36

INTRODUCTION

Nuclei in chalcocite grains from White Pine, Michigan occur
throughout the ore body and can be observed in polished section after
etching and staining with hydrochloric acid and potassium ferro-
cyanide. Detailed examination with the scanning electron microscope
showed that these cores are framboids and are similar to pyrite fram—
boids which have been found in black shales from Precambrian to
recent. Although pyrite is by far the most common mineral that is
framboidal, other sulfides and oxides have been found with this
texture.

By definition, a framboid is an aggomeration of small grains,
called microcrysts, into a sphere or ellipsoid (Love 6 Amstutz,
1966). The chalcocite would fit this definition and as described
below the size distribution of the chalcocite framboids is similar to
those found in pyrite.

Once the framboidal nature of the chalcocite has been estab-
lished, their origin is important in understanding the origin of the
mineralization at White Pine. Although this texture can be produced
inorganically in pyrite (Berner, 1969), many workers interpret it as
an indication of sulfate reducing bacteria. Recent studies on the

requirements of biogenic sulfides (Trudinger, 1972) describe an

environment compatible with that represented by the Nonesuch Shale.
Sulfide fractionation studies (Burnie, 1972) also support a biogenic
origin for the Nonesuch sulfides. Any theories on the origin of the
chalcocite must be compatible with the formation of framboids.

Two origins for the framboidal chalcocite must be considered:
either they represent replaced pyrite framboids or they are primary
chalcocite. In this paper the occurrence and distribution of the
framboidal chalcocite is documented and then the nature of the
chalcocite is compared with the pyrite immediately above the mineral-

ized zone.

GEOLOGIC SETTING

The ore body at White Pine Mine, Ontonagon Co. Michigan is
a classic example of a strata bound ore deposit. The mineralized zone
lies at the base of the Upper Keweenawan Nonesuch Shale, an organic
rich series of sandstone, siltstone, and shale about 600 feet thick
at White Pine. The Copper Harbor Formation, 2300 to 5500 feet of
conglomerate and red sandstone, underlies the Nonesuch. The Middle
Keweenawan Portage Lake Lava Series underlies the Copper Harbor and
is well known for native copper deposits 20 to 80 miles to the
northeast. The top of the Nonesuch grades into the overlying Freda
Sandstone, 500 feet of siltstone and shale.

The mineralization occurs in a 25 foot zone within the Lower
Nonesuch and Upper Copper Harbor. The lithologic units in this zone
have been informally named the Lower Sandstone, the Parting Shale,
the Upper Sandstone, and the Upper Shale. Each of these four have
been subdivided into subunits. The subunit terminolOgy shown in
Figure 1 will be used in this paper.

The highest percent copper (about 3) mineralization occurs
in Domino, Thinly, and Upper transition. Both Domino and Thinly
are thinly laminated black shale and siltstones rich in organic

material. The Upper Transition grades into Thinly and also contains

shale beds. Copper mineralization of l to 2 percent is found in

Dark Gray Massize and UZV. Both of these subunits are gray, massively
bedded siltstones. Most of the copper is in finely dispersed grains
of chalcocite. A little native copper also occurs at the base of

the mineralized zone.

The Nonesuch Shale is located on the axis of the Iron River
syncline, which trends NE-SW on the south flank of the Lake Superior
basin. Dips in the syncline are low to the south but steep on the
north side where the syncline meets the Porcupine Mt. uplift. Along
the western margin of the mine the White Pine fault strikes NW and
dips steeply to the NE. The displacement to the NE of the mine is
much greater (3000 to 5000 miles) than to the SE (240 ft.). Many
other faults are known in the area.

The mineralization in the Lower Nonesuch at White Pine has
been thoroughly discussed by Ensign and others (1968), White and

Wright (1954, 1966), and Brown (1971).

METHOD OF OBSERVATION

The framboidal centers in the chalcocite are only visible
after the polished section has been stained with a solution of 250 ml.
water, 2 ml. concentrated hydrochloric acid, and .1 ml. saturated
potassium ferrocyanide solution. The thin section is immersed in
the stain for 20 seconds, then rinsed with distilled water and
allowed to air dry. This stain is sensitive to low concentrations of
iron (Feigl, 1958). The relative concentration of iron in chalcocite
can be told by the color of the stain. This color ranges from
yellow at the lowest (about .5%) through purple (about .8%), deep to
light blue (about 1.5%) to light green (about 2%) at the highest
concentration recorded. Most chalcocite stains shades of blue. Not
all chalcocite contains enough iron to react with the stain.

Under a reflected light microscope the framboidal cores
usually appear as circles and ovals of beige surrounded by blue
stained chalcocite (Figure 2). Not all stained chalcocite grains
have cores in cross section. This either could be an effect of a
random section, or not all stained grains have cores. Unstained

grains never have cores.

SHAPE AND STRUCTURE

The framboids can best be observed with the scanning electron
microscope. The framboids were first located with the ore micro—
sc0pe on a polished and stained section. Photographs show that the
cores are spheres or ellipsoids filled with smaller microcrysts at
least as small as .2 micron (Figure 3). In some framboids the micro-
crysts appear to be small platelets while in others they appear to be
more equidimentional. However between framboids the size of these
microcrysts varies, and in the samples studied ranged from smaller
than .1 microns to .5 microns. At 20,000 magnification the micro-
crysts appear to be a mixture of small euhedral grains and platelets
(Figure 4). It is not possible with this resolution to determine the
size of the possible smaller microcrysts.

In some chalcocite grains the framboidal core is in higher
relief than in others (Figure 5). This is probably due to differing
hardness of the core and different responses of the framboid to the
etching. Occasionally a framboid is plucked out in the preparation
of the thin section (Figure 6).

Microcrysts in cores with well defined circular or elliptical
cross section are densely packed. In these well defined cores, the
cross Sectional shape of the framboid is independent of the shape of

the grain (Figure 3). These well defined cores are made up of

ll!!!“ It'll

densely packed microcrysts and the rim surrounding these cores con-
tain dispersed microcrysts. The number of microcrysts, from the edge
of the core to the edge of the grain appear to decrease exponentially
(Figure 5). In some grains the core entirely occupies the grain--
that is, there is no rim surrounding the framboids (Figure 7).

The shapes of the cores are variable with most being circular
or elliptical, while some approximate the shape of the grain in which
they occur. All gradations exist between a grain with a well defined
core and a grain with a core that completely fills the grain
(Figure 8).

The circular or elliptical shape of the cores on polished
section indicates that the framboids are probably ellipsoids in three
dimensions. In a sample of 350 core sections there are too many
(50%) circular sections for the true shape to be a triaxial ellipsoid.
In the same sample the apparent long axis of the ellipse is longer
than the apparent short axis. From this data it is concluded that

the framboids are biaxial prolate ellipsoids.

COMPARISON WITH OTHER FRAMBOIDS

By definition, a framboid is a sphere or ellipsoid made up of
microcrysts. The scanning electron microscope photographs show that
the well defined oval and circular sections of cores have this fram-
boidal structure, but the dispersed cores do not. They are made up
of microcrysts, but are not Spheres or ellipsoids. Framboidal cores
have rarely been observed in the literature (Rust, 1935). Thus the
behavior of the microcrysts during the growth of the surrounding
grain can only be surmised, Since one can see microcrysts breaking
away from the well defined, definitely framboidal cores, it seems
reasonable to assume that the now di5persed cores were once proper
ellipsoidal framboids.

Framboids have been observed with transmitted light micro-
scope after separation from unconsolidated sediments (Love, 1967),
in polished section with reflected light, and in thin section by
reflected and transmitted light (Lougheed, 1973). Of these methods,
the polished section with reflected light is the only possible one
for the chalcocite cores. The microcrysts in the cores are too small
for clear resolution under a light microsc0pe and comparison with
other framboids is made on the SEM photography and the size dis-

tribution, to be discussed later.

Some workers have found ordered packing of microcrysts in

the pyrite framboids. No order is apparent in these photographs.

SIZE FREQUENCY DISTRIBUTION

The cores are of various sizes with discrete circular cores
rarely having a diameter greater than 23 microns. In the elliptical
cores the short axis is rarely longer than 23 microns and the long
axis 26 microns. In cases where the core approximated the shape of
the grain, the limit of size is the size of the grain. These cores
are up to 100 microns long. The size distribution of these was not
attempted, since all size distribution methods require an assumed
shape.

Because of the number of circular sections encountered, the
shape of the discrete framboids can be assumed to be a biaxial pro-
late ellipsoid and therefore a relatively easy method for the size
frequency distribution of the minor axis can be used. This method
was developed by Wicksell (1925) for Spheres and later extended by
him to Special cases of ellipsoids (1926). It is the only method
that does not assume constant axial ratios or a given eccentricity
(Underwood, 1970).

Wicksell requires the following assumptions: (1) Prolate
ellipsoid of revolution, (2) Unimodal distribution, (3) Random
distribution in Space, (4) Random orientation of axes, (S) Orientation

independent of size, (6) eccentricity independent of size.

10

11

The shape of the size frequency distribution obtained using
this method is easily comparable to that measured directly by other
workers for spherical pyrite framboid (Love, 1967) (Figure 9). This
size frequency distribution of the chalcocite cores falls easily into
the known size distribution of pyrite framboids, further evidence that

the cores are actually framboids.

LITHOLOGIC DISTRIBUTION

Although framboidal chalcocite grains are found throughout
the mineralized zone, they are not equally abundant in all lithologies.
Detailed studies of samples from a vertical column (Longwall) show
that the framboidal chalcocite grains are most common in the finer
grained laminated 1ithologies--Lower Transition-Domino, Upper
Transition-Thinly and TOp Zone. The massive, less well laminated,
ore bearing lithologies contain fewer framboidal grains.

There is no stratigraphic or lithologic correlation with the
two core types. Well defined cores and diSpersed cores can be found

adjacent.

12

COMPOSITION

The framboidal cores were originally observed because of the
difference in response between core and the surrounding grain to the
iron sensitive stain. From the color of the stain it was not apparent
whether the core contained more or less iron than in the matrix.
MicrOprobe traces on five selected cores were made to determine rela-
tive concentration of iron. The slides were prepared by polishing,
staining, and coating with carbon.

The difference in amount of iron between rim and core varies
among grains from a core 2.4 times more iron rich to cores with a very
slight increase of iron (Figures 10a, 10b, 10c, 10d, 10e). Cores
with well defined circular and elliptical shapes (a, b, c, d) and
dispersed cores (e) show increasing iron.

Although the microprobe traces show increasing iron, this may
not be the actual case. The higher iron content in the core may be
due to more iron absorbed to the very high surface area of the micro-
crysts. Furthermore most of the framboids stand above the plane of
the section (i.e., high relief) and are closer to the detectors. This
would result in higher count rates. For these reasons it is not
possible to determine if the core contains more or less iron than the

surrounding grain, only that a difference exists.

13

14

In order to avoid this possible stain-composition interaction
two other stains were tried: an a-a' dipyridyl stain (Feigl, 1958)
and an ammonium dichromate stain (Einaudi, 1970). Neither were sensi-
tive enough to detect framboids. The time consuming procedure of
hunting through unstained grains under the microprobe was also
attempted unsuccessfully. Carbon concentration was also found to
be greater in the core than in the rim. Three microprobe traces were
made for carbon (Figures 10a, 10d, 10e). This increase could also
be due to high surface area and high relief of the cores since all
of the sections were carbon coated.

Potassium was also found to be more concentrated in the core
than in the rim (Figures 10a, 10d). Although potassium is in the
stain, it is not active in the color Prussian blue. However, the
possibility that potassium increases due to preparation does exist.

It is interesting to note that the sulfate reducing bacteria
thought to be reSponsible for framboids require trace amounts of Fe,

K, and C (Postgate, 1965).

ORIGIN OF FRAMBOIDS

Whatever the origin prOposed for chalcocite grains, either
replaced pyrite or primary, the formation of framboids must be in-
cluded. Most workers believe that framboidal texture indicates the
activity of sulfate reducing bacteria (Berner, 1970). The bacteria
reduces the sulfate to sulfide, which forms H25 and combines with
metals. In the case of pyrite formation, a variety of FeS compounds
form with pyrite as the final product (Berner, 1970).

Pyrite framboids have been produced inorganically by Berner

(1969) by bubbling H S gas through NaOH solutions, then adding

2
FeSO47H20 to the resulting NaHS solution. In natural environments
the bacteria would supply the gas.

The idea of primary chalcocite has been criticized in the
past by Davidson (1962) and by Boothe and Mercer (1963) on grounds of
copper toxicity to bacteria. However, Temple and LeRoux (1964) have
shown that fatal copper concentration depends on the rate of H28 pro-
duction. If a bacteria colony can produce enough H25 to precipitate
the copper before it is toxic to the bacteria, then primary chalcocite
framboids can develop.

If the framboids are biogenic then the Nonesuch sediments

must meet the requirements of bacterial growth. Trudinger and others

(1972) and Temple (1964) state that the requirements of bacteria are

15

16

an anerobic, reducing condition with a slight acid to slight alkaline
pH and a supply of organic material. The environment of deposition
of the Nonesuch Shale is compatible with the sediment type one would
expect to find bacteria in.

Further evidence for an organic origin for the sulfate at
White Pine is given by a sulfur isotope study conducted by Burnie
et a1. (1972) which indicates that the sulfur isotopes are produced

by biogenic activity.

DISCUSSION

The origin of the chalcocite in White Pine has long been
debated. Authors have used it as an example of a syngenetic deposit
and as an epigenetic deposit. Recent work has favored the epigenetic
model (Brown, 1971; White, 1971). These conclusions were based on an
irregular mineral fringe zone that cut lithologic units at a shallow
angle and on zoning at the fringe (Brown, 1971). Ore bearing solutions
were thought to have come from the Copper Harbor Conglomerate below.
Recent work by Vogel and Ehrlich (personal communication) has shown
that the fringe cutting is no more irregular than a given depositional
unit.

One way to test the replacement model is to look at the pyrite
zone above the mineralized zone. If the chalcocite has replaced the
pyrite, then since the detailed framboidal structure is preserved,
all details of the pyrite morphology should be preserved. Pyrite from
the unmineralized zone, only centimeters above the chalcocite, was
studied. Nine samples scattered throughout the mine area were used.

There are indeed framboids in the pyrite. Two types were
found during examination of the pyrite and fringe zone. The first is
made up of euhedral microcrysts of pyrite much larger (3 to 4 microns)

than the microcrysts in the chalcocite framboids (less than .2

17

18

micron) (Figure 11). These pyrite framboids are also larger than the
chalcocite framboids. These framboids fit the definition of framboid
but are not similar to chalcocite framboids in the mineralized zone.

The second type of pyrite framboid is much smaller, 3 to 4
microns in diameter (Figure 12). The microcrysts are various irregular
shapes and sizes from 1.25 to 1 micron across. The outermost micro-
crysts are wedge shaped and fit together closely. Both microcryst
and framboid are much smaller in this type than in the previous type.
Although these also fit the definition of framboid, they are not
similar to the chalcocite framboids.

Since both of these pyrite framboid types are made of micro-
crysts considerably larger than the chalcocite microcrysts, the possi-
bility exists that the chalcocite microcrysts resulted from dispersion
of pyrite type microcrysts during nucleation of the chalcocite grain.
The pyrite microcrysts were examined for possible internal structure
using the same methods as those used on the chalcocite cores. No
internal structures were found, indicating that the chalcocite did not
form from pyrite microcrysts.

Along with framboids, lenses of euhedral grains, often
triangular in cross section, are found in the pyrite zone. These
lenses are much larger than the framboids, up to 3 or 4 mm. in length,
although smaller irregular groups of euhedral grains, about the same
size as the framboid are also found and may be due to random section-
ing of the larger lenses. It is possible that the framboid is also a

chance of circular section of these irregularly shaped clouds, since

19

irregular groups of euhedral grains are much more common than
circular groups.

Detailed comparisons of the pyrite framboids and the chalcocite
framboids were made. The two types of framboids observed in pyrite
were not found in the chalcocite grains. Furthermore, the euhedral
grains, so abundant in the pyrite are virtually absent in the
mineralized zone.

The fringe itself (measured in millimeters) is a texturally
very complicated zone with replacement of pyrite by bornite and
digenite (Brown, 1971). However, this is only millimeters thick and

is obviously the interface between two geochemical environments.

CONCLUSION

Two origins are possible for these framboids--primary deposi-
tion and secondary replacement of pyrite. If the chalcocite fram-
boids are replaced pyrite, similar pyrite framboids should be present
above the mineralized zone. Alternately, euhedral clusters and fram-
boids like those of pyrite above the mineralized zone should also be
found in chalcocite within the mineralized zone. Nothing of either
case is apparent, supporting a primary origin for the framboidal

chalcocite.

20

REFERENCES

REFERENCES

Berner, R. A., 1969, The Syntheses of Framboidal Pyrite: Econ. Geol.,
v. 64, p. 383-384.

Berner, R. A., 1970, Sedimentary Pyrite Formation: Am. Jour. Sci.,
v. 268, p. 1-23.

Booth, G. H., 1963, Resistance to Copper of Some Oxidizing and
Reducing Bacteria: Nature, v. 99, p. 622.

Brown, A. C., 1971, Zoning in the White Pine Copper Deposit,
Ontonagon, Michigan: Econ. Geol., v. 66, p. 543-573.

Burnie, S. W., Schwartz, H. P., and Crocket, J. H., 1972, A Sulfur
Isotopic Study of the White Pine Mine, Michigan: Econ. Geol.,
v. 67, p. 895-914.

Davidson, C. F., 1962, The Origin of Some Strata-Bound Sulfide Ore
Deposits: Econ. Geol., v. 57, p. 265-274.

Einaudi, M. T., 1970, An Iron Sensitive Stain for Iron Rich
Sphalerite: Am. Miner., v. 55, p. 1048-1051.

Ensign, C. 0., Jr., White, W. 5., Wright, J. C., Patrick, J. L.,
Leone, R. J., Hathaway, D. J., Trammell, J. W., Fritts,
J. J., and Wright, T. L., 1968. Copper Deposits in the
Nonesuch Shale, White Pine, Michigan in Ore Deposits of the
United States 1933-1967, ed. J. D. R1356: Am. Inst. Mine.
Metal. and Petr. Eng., Inc., p. 460-488.

Feigl, F., 1958, Spot Tests in Inorganic Analysis: Elsevier, New
York, 600 pp.

Lougheed, M. S. and Mancuso, J. J., 1973, Hemetite Framboids in the
Negaunee Iron Formation, Michigan: Evidence for their
Biogenic Origin: Econ. Geol., v. 68, p. 202-209.

Love, L. C., 1967, Early Diagenetic Iron Sulphide in Recent Sediments
of the Wash (England): Sedimentology, v. 9, p. 327-352.

21

22

Love, L. G. and Amstutz, G. C., 1966, Review of Microscopic Pyrite:
Fortschr. Mineral., v. 43, p. 273-309.

Postgate, J. R., 1965, Recent Advances in the Study of Sulfate
Reducing Bacteria: Bact. Review, v. 29, p. 425-441.

Rickard, D. T., 1970, The Origin of Framboids: Lithos, v. 3,
p. 269-293.

Rust, G. W., 1935, Colloidal Primary COpper Ores at Cornwall Mines,
South-eastern Missouri: J. Geol., v. 43, p. 398-426.

Temple, K. L., 1964, Syngeneses of Sulfide Ores: An Evaluation of
Biochemical ASpects: Econ. Geol., v. 59, p. 1473-1491.

Temple, K. L., and LeRoux, N. W., 1964, Syngenesis of Sulfide Ores:
Sulfate-Reducing Bacteria and COpper Toxicity: Econ.
Geol., v. 59, p. 271-278.

Trudinger, P. A., Lambert, I. B., and Skyring, G. W., 1972, Biogenic
Sulfide Ores: A Feasibility Study: Econ. Geol. v. 67,
p. 1114-1127.

Underwood, E. E., 1970, Quantitative Stereology: Addison-Wesley,
Reading, Mass., 274 p.

Wicksell, S. D., 1925, The Corpuscle Problem. A Mathematical Study
of a Biometric Problem: Biometrika, v. 17, p. 84-99.

Wicksell, S. D., 1926, The Corpuscle Problem. Second Memoir. Case
of Ellipsoidal Corpuscles: Biometrika, v. 18, p. 151-172.

White, W. S., 1971, A Paleohydrologic Model for Mineralization of
the White Pine COpper Deposit, Northern Michigan: Econ.
6801. V0 66’ p. 1'13.

White, W. S., and Wright, J. C., 1954, The White Pine Copper Deposit
Ontonagon County, Michigan: Econ. Geol., v. 49, p. 675-726.

White, W. S., and Wright, J. C., 1966, Sulfide Mineral Zoning in the
Basal Nonesuch Shale, Northern Michigan: Econ. Geol.,
v. 61, p. 1171-1190.

23

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   
 

 

 

 

 

 

 

 

 

l LBS. COPPER TON
Siltstone, Gray 5 I I I I
WIDELY shale. blk, widely 20 40 60 80
laminated
E: :t47
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3% ‘F46 -‘
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U.Z.V. Massive bedded
a:
w _-‘W—-_-————-
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Q siltstone, Red-brn.
to gray, massive
3 BRN. bedded w/limy
USV. . 6.. 1.9-99 nodules --—‘I-
b - o a - o O o ° ° G
—-————-—d
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I j ' - ' j ' ‘ . Shale, blk, thinly
III—"LY - - . - - z. ' . _- ' -. - Laminated; sandstone
4);.“ L__ . .- _- ' - :5 .' less than 50$
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m . " gray, fine to med.,
0 (D to coarse grained
w/conglomeratic
ll. (I UP. ,. . . .- - . , . . . o lenses. Occ shale
I DJ 5.5. .° . . , ‘. o ‘_ - o - '9' , member, occ. cross
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TOP-‘32, HSiltstone, gray} shalq g
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#IO BED ' ‘. . ' f ' . artings less than 50% b
a ‘ . o .. . . .

/COPPER .1 .' ', '--:"'.
HARBOR FM. ' ' 33533.20”;
vent SCALEI'82 Ft

 

 

 

 

Fig. 1. Lithologic column at White Pine.

24

 

 

Fig. 2. Oval and circular framboidal cores in stained
grains under reflected light (1 cm = 10 u).

25

 

.4- —

Circular core

 

Oval core

Fig. 3. SEM photos of two cores (1 cm 10 u).

 

Oval core

 

Edge of circular core in upper left (note
microcrysts in matrix).

Fig. 4. Detail of cores in Fig. 3 (1 cm = .5 u).

 

Fig. 5. ESpecially high relief in core. Compare
to those in Fig. 3 (1 cm = 2 u).

 

Fig. 6. Framboidal core plucked out during
preparation (1 cm = l u).

 

(1 cm = 10 u)

 

Detail of above (1 cm = S u).

Fig. 7. Core that occupies most of its grain
(microprobe photo).

 

(1 cm = 10 u).

 

Detail of above (1 cm = 5 u).

Fig. 8. Core that almost occupies its grain (microprobe
photo).

FREQUENCY

40!—

30T-

20!—

 

Fig. 9.

 

30

 

 

 

 

2.3

SHORT AXIS IN MICRONS

Size frequency distribution of chalcocite framboidal cores.

31

 

IoooFe
200K .
I
200 C
: = : + : J. : : a
..g/‘——
—FBAMBOID—l

(a)

Fig. 10a. Microprobe traverse of elliptical framboidal core
for Fe, K, and C (counts per second are given).

32

 

 

'FRAMBOID-

Fig. 10b. Microprobe traverse of circular framboidal core
shown in Fig. 2 for Fe.

33

   

Fe

H?-

l
I

l
I

l l
j I

-FRAMBOID—| (C)

Fig. 10c. Microprobe traverse of circular framboidal
core for Fe.

w-

34

500»!-

 

 

w

L _L l l l
T I

-FRAMBOID—

1-

Fig. 10d. Microprobe traverse of circular framboidal

core for Fe, C, and K (counts per second are given).

 

 

3S

 

 

 

 

 

 

500 F9
200 C
% 'r i % ; : : :
f-ICLL(-'
FRAMBOID I ( )
Fig. lOe. Microprobe traverse of framboidal core shown in

Fig. 8 for Fe and C (counts per second are given).

36 “

 

Fig. 11. Euhedral microcrysts in pyrite
framboid (1 cm = 1 u).

 

Fig. 12. Wedge shaped microcrysts in pyrite
framboid (1 cm = l u).

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