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Michigan State
University

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This is to certify that the
thesis entitled
THE MICHIGAMME INTRUSION, A CASE STUDY OF THE IMPORTANCE OF
REMANENT MAGNETIZATION IN MAGNETIC INTERPRETATIONS ,
MARQUETTE COUNTY, MICHIGAN.

presented by

Wesley M. Phillips

has been accepted towards fulfillment
of the requirements for

_M.S___deyee in _GEQLQGX___

Q Zifly I /
Major professor I

 

Date 8/2/79

 

0-7639

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RETURNING LIBRARY MATERIALS:

\. :- . Place in book return to remove
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THE MICHIGAMME INTRUSION, A CASE STUDY OF THE IMPORTANCE OF
REMANENT MAGNETIZATION IN MAGNETIC INTERPRETATIONS,

MARQUETTE COUNTY, MICHIGAN

By

Wesley M. Phillips

A THESIS

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

MASTER OF SCIENCE

Department of Geology

1979

ABSTRACT
THE MICHIGAMME INTRUSION, A CASE STUDY OF THE IMPORTANCE OF
REMANENT MAGNETIZATION IN MAGNETIC INTERPRETATIONS,
MARQUETTE COUNTY, MICHIGAN
By

Wesley M. Phillips

A computerized magnetic modeling study of the Michigamme In-
trusion is performed to demonstrate the importance of natural remanent
magnetization (NRM) in magnetic interpretations, and to exhibit the
ease with which NRM can be considered with the aid of a computer
program. The structure of the intrusion is magnetically modeled by
comparing the observed vertical magnetic anomaly of the intrusion to
vertical magnetic anomalies generated by computer models of the in-
trusion. Analysis of the magnetic properties of the body show the
intrusion to possess a predominately large reverse-remanent magneti-
zation component. Computer models show that the observed magnetic
anomaly of the intrusion is easily modeled, given the geophysical and
geologic parameters determined in the study, as a stock steeply dipping
to the north. It is also shown that approximate models considering
NRM can be made without a detailed field analysis of the body by using

paleopole orientations as an approximation of the NRM orientation.

ACKNOWLEDGMENTS

My sincere thanks go:

to Tom Vogel without whom this study would never have been
completed. Thank you for your patience and understanding.

to my committee, Dr. H. Bennett, Dr. F. W. Cambray, Dr. J. Wilband
for their assistance. Special thanks to John for his help with the
computer.

to Dr. R. Vandervoo of the University of Michigan for the use of
his paleomagnetic laboratory and equipment. Special thanks to Doyle
Watts for his assistance with the equipment.

to Paul Tipler and Bob Williamson of Oakland University for their
cherished friendship and stimulation in the sciences.

to Mark Schoomaker and Tim Stanton for their help with the field
work. Also special thanks to Mark for his invaluable assistance with
the computer programming.

to the Chateau for providing a home from which things such as this
can be done without one going off the deep end; and to my friends, one
and all.

to my family for their love and understanding.

ii

TABLE OF CONTENTS

LIST OF TABLES O O O O O O O O O O O 0

LIST OF FIGURES O O O O O O O O O O 0

INTRODUCTION 0 O O O O O O O O O O O 0

Location and Topography . . . . .
General Geology and Geophysics .
Field and Laboratory Methods . .

MAGNETIC PROPERTIES . . . . . . . . .

Orientation of the Characteristic

Remanent Magnetization . . . .
Remanent Magnetization Intensity
Susceptibility . . . . . . . . .
Koenigsberger Ratio (Q-Ratio) . .
Summary . . . . . . . . . . . . .

MAGNETIC MODELING . . . . . . . . . .

Theoretical Model
Computer MOdel o o o o o o o o o
Approximations . . . . . . . . .

MICHIGAMME STOCK . . . . . . . . . . .

Computer Models of the Michigamme
Discussion of Results . . . . . .

CONCLUSIONS 0 O O O O O O O O O O O O

APPENDICES O O O O O O O O O O O O O O

A. Whole Rock Analyses, and Trace and Rare-Earth

Element Concentrations (PPM)

B. Corrected Vertical Magnetic Intensity Data

C. The Remanent Magnetization Orientation and Intensity
NRM, Thermally Cleaned, and A.C.

for Each Sample:
CleaDEdooooooooooo

iii

Page

vi

CDUIN

14

14
26
26
28
28
31
31
34
34
38

39
48

49

51

52

54

65

D.

E.

Computer Model Listing .

Surface II Commands . .

BIBLIOGRAPHY O O O O O O O 0

iv

LIST OF TABLES
Table Page

1. Average Remanent Magnetization Orientation for each
SampleSite........................ 22

2. Lower Keweenawan Paleomagnetic Poles . . . . . . . . . . . 25

3. Average Remanent Magnetization Intensity, Susceptibility
and Q-Ratio for eaCh sample Site 0 o o o o o o o o o o o o 27

4. Geologic and Geophysical Parameter Values Used in
computer MOdels I & II 0 O O O O O O O O O O O O O O O O O 40

LIST OF FIGURES

Figure Page
10 Location and Topographic map 0 o c o o o o o c o o o o o o 3

2. Structural Geologic map of the Lake Michigamme area
(Klasner, 1978) C O O C O O O I O O O O O O O O O O O O O O 6

3. Total intensity, Aeromagnetic map of the study area
(Case and Gait, 1965) O C O C O O O O O O O O O O O O O O O 9

4. Vertical magnetic intensity contour map
(General StUdy area) 0 O O O O O O I I O O O O O O O O O O 10

5. Vertical magnetic intensity contour map
(Detailed map) 0 O O O O O O O O O I O O O O O O O O O O 0 ll

6. Magnetic survey grid . . . . . . . . . . . . . . . . . . . 12
7. Zijderfeld diagrams, sample sites (A, B, C, F) . . . . . . 16
8. Zijderfeld diagrams, sample sites (D, E, 1A, 2A, 3A) . . . 18
9. Thermal and A.C. Demagnetization curves . . . . . . . . . . 20
10. Remanent magnetization declination & inclination

stereo plots: A) NRM, B) Thermal cleaned,

C) A.C. CleaHEd o o o o o o o o o o c o o c o o o o o o o c 24
11. Total magnetization axis . . . . . . . . . . . . . . . . . 29
12. Computer model: A) Coordinate system, B) Parameters . . . 33
130 Prism mOdel for dipping CYlinderS o o o o o o o o o o o o o 35
14. Model I. For a cylinder dipping 70 degrees in the:

A) North direction, B) East direction, C) South

direCtion, and D) weSt dirECtion c o o o c o o o o o o o o 42

15. Model I. For a cylinder dipping in the N20°E
direction: E) 70° dip, F) 50° dip, and G) 30° dip . . . . 43

16. Model II. For a cylinder dipping 70 degrees in the:

A) North direction, B) East direction, C) South
direction, and D) West direction . . . . . . . . . . . . . . 44

vi

Figure

17.

18.

Page

MOdel II. For a cylinder dipping in the N20°E
direction: E) 90° dip, F) 70° dip, C) 50° dip, and
H) 30° dip O O I O O C I O O O O O O O I O O O O O O O O O 45

Model I & II Profiles.
A) Model I Profiles: For a cylinder dipping in the
N20°E direction 70°, 50°, and 30°.
B) Model II Profiles: For a cylinder dipping in the
N20°C direction 90°, 70°, 50°, and 30° . . . . . . . . . 46

vii

INTRODUCTION

The purpose of this study is to present a magnetic modeling study
of the Michigamme Intrusion to show the importance of natural remanent
magnetization (NRM) in magnetic interpretations; and to exhibit the ease
with which NRM can be considered with the aid of a computer program.
The structure of the Michigamme Intrusion will be magnetically modeled
by comparing the observed vertical magnetic anomaly of the intrusion to
vertical magnetic anomalies generated by computer models of the intru-
sion. The Michigamme Intrusion was selected for this study because of
its structure (Stock) and its observable reverse-remanent magnetization
component.

In the interpretation of magnetic anomalies the importance of NRM
is gradually being accepted. Early theoretical investigators (Zietz and
Brooks, 1951; Sutton and Mumme, 1957; Hood, 1963; Zietz and Andreasen,
1967) indicated that NRM is a significant factor that should be
considered in aeromagnetic interpretations. Girdler and Peter (1960)
and Torres (1976) showed that some magnetic anomalies cannot be
explained by induced magnetization alone and that a large reverse
remanent magnetization must be assumed to explain the anomaly under
investigation. Other studies have confirmed the importance of NRM in
magnetic modeling through interpretation techniques which included
direct measurements of the intensity and orientation of the NRM

component in the body being studied (Green, 1960; Watkins, 1961; Book,

1962; Hayes and Scharon, 1963; Dubois and Carey, 1964, Strangeway, 1965;

Park, 1968).

Most magnetic interpretations do not consider NRM, even though the
influence of NRM on magnetic anomalies has been shown. It is the
contention of the author that NRM is neglected in magnetic modeling for
two simple, but presently unfounded, reasons:

1) The intensity and orientation of the NRM component are not easily
available (Green, 1960; Watkins, 1961; Book, 1962; Hayes and
Scharon, 1963; Dubois and Carey, 1964; Strangeway, 1965; Park, 1968)
or as in some cases not physically obtainable (Girdler, 1960;
Torres, 1976).

2) Until recently, computer automated interpretation techniques using
induced magnetization (Henderson, 1960; Whitehill, 1973) have not

been revised to consider NRM (Shanabrook, 1978).

Location and Topography

 

The study area is located (Figure 1) in the Upper Peninsula of
Michigan approximately one mile west of Champion just off of highway 41.
The survey area is contained within sections 25, 26, 35, and 36 of T48N,
R30W of the Michigamme and Champion quadrangles, Marquette County.

The intrusion lies on the east shore of Lake Michigamme within
sections 35 and 36. The exposure is approximately 1000 feet in diameter
and is outlined by a gently sloping, 100 feet topographic high. Outcrop
exposures are distributed randomly across the topographic high, but are

mostly found intact along the slopes.

Figure 1. Location and Topographic Map.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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General Geology and Geophysics

 

The Michigamme Intrusion is magnetically associated with a swarm of
East- West trending dikes. Because the dikes cut structural features of
Middle and Lower Precambrian age and are fresh in character, they are
considered to be Keweenawan in age (Bodwell, 1972; WOod, 1972). They
are classified lower Keweenawan because they are reversely polarized.

It is proposed that they were emplaced 1.1 b.y. ago during a period of
continental rifting (Chase and Gilmer, 1973).

As shown in Figure 2, the Michigamme intrusion is circular and is
located at the Western end of the Marquette Synclinorium where the
tightly folded trough begins to open into a broad basin. It transects a
series of deformed Middle Precambrian metasediments which belong to the
Menominee and Baraga Groups of the Marquette Range Supergroup, (See
Cannon and Gairs (1970) revised stratigraphic nomenclature). Gravity
profiles indicate depths to basement ranging from a maximum of 2,438 m
in the East trough near Humbolt to a maximum of 1,097 m West of Lake
Michigamme in the West trough, with the depths becoming shallower toward
each end of the trough (Klasner and Cannon, 1974). Deformation in the
trough is attributed to the Penokean Orogony (Cannon, 1973), which
ocurred 1.85 - 1.95 b.y. ago (VanSchmus, 1970).

Klasner (1972) describes the body as petrographically fresh and
zoned containing a mafic pyroxene-rich interior and a plagioclase-rich
border phase. Petrographic and chemical analysis of three samples from
separate sites within the interior of the body by Morris (1978), show
the intrusion to be a diabase (See Appendix A).

The Total Field, Aeromagnetic map of the general study area reveals
a system of intense irregular shaped positive magnetic anomalies and a

series of moderate East-West trending positive and negative magnetic

Figure 2. Structural Geologic map of the Lake Michigamme Area
(Klasner, 1978).

 

 

               

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anomalies (Case and Gair, 1965). The intense positive magnetic
anomalies outline the pattern described by the synclinorium and are due
to the Negaunee Iron Formation and are also due to the iron-formations
contained in the Michigamme Formation. The moderate East-West trending
positive magnetic anomalies are due to the metadiabases, while the
negative East-West trending magnetic anomalies are associated with
reversely polarized Keweenawan Diabases.

The Keweenawan Diabase Stock under investigation is located between
East-West striking iron-formations which dip toward the stock (Figure
2). The negative magnetic anomaly associated with the stock may be
partially masked by the intense positive magnetic anomalies due to the
surrounding iron-formations (Figure 3).

To study the magnetic anomaly of the stock more closely, a ground
magnetic survey was conducted. Figure 4 is a general magnetic map of
the area which includes part of the anomalies produced by the nearby
iron-formations. Figure 5 is a more detailed magnetic map of the

anomaly produced by the stock.

Field and Laboratory Methods

 

The ground magnetic survey was conducted using a Scintrex Flux-Gate
Magnetometer (Model MF-2-100). Magnetic readings were adjusted to base
stations which were reread approximately every 2 hours to correct for
diurnal variations, instrument drift, and temperature effects on the
instrument. The adjusted data is listed in Appendix B.

The survey grid was laid out by the pace and compass method with
north- south, east-west trending traverses set 600 feet apart (Figure
6). Depending on the amount of detail desired, station spacing within

the traverses were varied from 50 feet to 400 feet.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 6.

13

Oriented blocks were collected from nine sample sites (Figure 1).
Samples were reoriented in the lab and cores 2.54 cm in diameter were
drilled for analysis. Susceptibilities of each sample were measured
with a Minnetech Magnetic Susceptibility Bridge (Model MS-3). Four to
six cores from each block were later analyzed at the University of
Michigan's Paleomagnetic Laboratory. Stepwise thermal and a.c.
demagnetizations were performed to remove the soft components of the
natural remanent magnetization (NRM), and to determine the general
character and stability of the remanent magnetization. A.C.
demagnetization was performed with a Schonstedt A.C. Demagnetizer (Model
GSD—l). During demagnetization the orientation and intensity of the
remanent magnetization were measured, between steps, with a Shonstedt
Spinner Magnetometer (Model SSM-l).
The computer program SHALOCI developed by Shanabrook (1978), with
additions by the author to approximate dipping bodies, was used to model
the Michigamme Stock. A complete listing and description of the program
is given in Appendix A of Shanabrook (1978).

The computer program SURFACE II was used to contour all the

computer modeled anomalies and the field anomalies (Sampson, 1978).

MAGNETIC PROPERTIES

Before the computer modeling process was begun, the magnetic
properties of the body were analyzed in detail. As mentioned
previously, cores from oriented blocks were analyzed to determine: 1)
The stability and types of remanent magnetizations present, 2) The
orientation and intensity of the characteristic remanent magnetization,
3) The susceptibility, and 4) The koenigsberger ratio (Q value) of the
remanent intensity to induced intensity. Thermal and a.c.
demagnetizations show the body to possess a variety of magnetic
stabilities and magnetizations, with the characteristic remanent

magnetization reversed and more intense then the induced magnetization.

Orientation of the Characteristic Remanent Magnetization

 

The methods of progressive thermal and a.c.'demagnetization were
used to determine the character and types of magnetizations present in
the samples and to clean the samples of weak secondary magnetizations.
In effect this was done to sort out unreliable data, and to determine
the orientation and intensity of the characteristic remanent
magnetization.

Zijderfeld (1967), developed a method of representing progressive
demagnetization to identify the direction and intensity of the various
magnetizations possessed by a sample. This information is displayed

through orthogonal projections (Generally onto the NS and EW planes) of

14

15

the curve described by the endpoint of the magnetization vector as it
undergoes changes during progressive demagnetizations. Through this
method secondary magnetizations were eliminated and the orientation and
intensity of the characteristic remanent magnetization were determined.

Representative Zijderfeld diagrams of each sample site are shown in
Figures 7 and 8. The orientations and intensities, determined by this
method, for each sample are listed in Appendix C. The average
orientation for each sample site are listed in Table 1.

Thermal and a.c. demagnetization curves, shown in Figure 9, provide
a quick overview of the types of magnetizations present at each sample
site. Sample sites (C, D&E, 1A, 2A, and 3A) exhibit stable and hard
magnetizations, all of which have similar characteristic remanent
magnetization directions. Sample sites (AAB, F, G) possess unstable
soft magnetizations, which are due to a viscous secondary magnetization.
These samples possess high Q values (See Table 3) and exhibit random
orientations that deviate from the orientations found in the more stable
samples; for this reason these samples were not used in determining the
intensity and orientation of the characteristic remanent magnetization.
It is assumed that the high Q values are due to lightning strikes which
have altered the remanent magnetization (Strangeway, 1965).

Sample sites (D&E) exhibit unique demagnetization curves that
indicate a self-reversal process taking place. The intensity of the
remanent magnetization initially increases during demagnetization rather
than decreases. The same phenomenon is found in paleomagnetic studies
of the Lower Keweenawan Baraga Dikes (Graham, 1953; Vincenz and Yaskawa,
1968). Both authors believe this phenomenon to be an example of a
self-reversal process, see (Nagata, 1955; Neel, 1955; Blackett, 1956).

Graham (1953) attributed the reverse remanent magnetization to a

16

Figure 7. Zijderfeld Diagrams, Sample Sites (A, B, C, F).

 

 

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18

Figure 8. Zijderfeld Diagrams, Sample Sites (D, E, 1A, 2A, 3A).

 

 

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Figure 9. Thermal and A.C. Demagnetization Curves.

22

 

 

 

 

Table 1. Average Remanent Magnetization Orientation for Each Sample
Site.
Ave. NRM Ave. Remanent Mag. Ave. Remanent Mag.

Sample Orientation Orientation Orientation

Site (Not Cleaned) (Thermal Clean) (A.C. Cleaned)
Dec. Inc. Dec. Inc. Dec. Inc.

A* 135.8 -3l.0 151.1 -26.6 117.0 -30.3
B* 80.5 -40.0 81.2 -39.7 102.7 —42.0

C 64.1 -43.0 62.6 -37.5 66.9 -42.0

D 56.0 -52.0 72.8 -62.9 ---- -----

E 32.0 -57.0 74.4 -56.9 ---- ----
F* 149.0 -28.0 148.8 -24.0 178.8 -23.1

0* 72.6 -54.5 Random Random

1A 54.9 -42.0 52.2 -38.9 58.2 -47.6
2A 138.0 -69.0 130.8 -67.4 149.9 -66.9
3A 82.7 -62.0 98.9 -68.5 ---- ----
Average 82.5 -46.8 74.5 -51.4 77.9 -52.1

Characteristic Remanent Magnetization Orientation
(Average of the thermally and A.C. cleaned sites)

Declination = 76.2
Inclination = -51.8

* Eliminated from determining the Characteristic Orientation

23

self-reversal process of magnetostatic interaction. Vincenz and Yaskawa
(1968) considered it more probable that a small antiparallel component
of magnetization was formed by a self-reversal process during a reversed
geomagnetic field in the Lower Keweenawan. It is believed by the author
that a similar process, as described by Vincenz and Yaskawa (1968), has
taken place at sample site (D&E). The orientation of the remanent
magnetization for sample sites (D&E) were thus included in computing the
average orientation of the characteristic remanent magnetization for the
body; however the intensities were not included in computing the average
remanent magnetization intensity of the body.

A characteristic remanent magnetization orientation of Declination
= 76.2 and Inclination = -51.8 was calculated from the thermal and a.c.
cleaned data collected at sample sites (C, D&E, 1A, 2A, 3A). Although
thermal and a.c. cleaning had various effects on the pole directions, at
the individual sample level (Appendix C), cleaning only slightly
enhanced the clustering of the average poles of each site (Figure 10).
As shown in Table 1, the average thermal pole and average a.c. pole are
similar, with both poles diviating little from the NRM pole. The final
characteristic pole was determined by averaging the thermal pole and the
a.c. pole.

The paleopole position for this characteristic remanent
magnetization direction was determined using the method described by
McElhinney (1973). Comparison with paleopoles from other Lower
Keweenawan Formations (Table 2), shows the pole to be slightly
different. When plotted onto the apparent polar wandering track
determined by Irving and McGlynn (1976) and age of 1.19 bybp is
suggested; compared to an age of 1.13 bybp suggested for other lower

Keweenawan Poles. This indicates that the east-west trending reversely

24

 

<//N

Figure 10. Remanent magnetization declination & inclination stereo
plots: A) NRM, B) Thermal cleaned, C) A.C. cleaned.

‘~~4—e”/' kt

25

 

 

Table 2. Lower Keweenawan Paleomagnetic Poles.
Area
Source Cleaning Pole Position Dec. Inc. k
Logan Sills/
Palmer (1970) A.C. 141.7W, 48.4N 109.0 -71.2 53
Osler Group/
Palmer (1970) 156.7W, 48.9N 117.5 -64.5 24
Grand Portage/
Palmer (1970) 159.8W, 47.0N 116.4 -62.9 30.5
Grand Portage/
Books (1968) 163.0W, 44.5N 117.0 -59.2
Duluth Gabbro/
Beck (1970) A.C. 156.5W, 42.5N 91.0 -65.5 44.2
Baraga Dikes/
Graham (1953) 99.5w, 45.0N
Michigamme Stock/
This Study (1979) 146.2W, 14.7N 76.2 -51.8

 

26

polarized dikes were emplaced before the Keweenawan Lavas and Logan
Sills. The ages are also in near agreement with the date of 1.14 bybp

given by Chase and Gilmer (1976) for the beginning of rifting.

The Remanent Magnetization Intensity

 

The resultant measurements of the remanent magnetization intensity,
at each sample site (Table 3), show the intensity to vary significantly
across the body. The average site intensities vary from a moderate 10.8
x 10‘5 emu/cm3 to some unusually high intensities as strong as
8,252. x 10‘5 emu/cm3. Remanent intensities of this magnitude are
not typical but have also been observed in the Lower Keweenawan, Baraga
County, diabase dikes (Vincenz, 1968). As mentioned previously these
atypical intensities are assumed to be alteration due to lightning
strikes. For this reason the unusually high intensities, samples (A, B,
& F), were eliminated from approximations of the bodies average remanent
magnetization intensity. Also eliminated were samples (D&E), which
exhibit alternations in intensity due to a partial self-reversal
mechanism.

The remanent magnetization intensities of the remaining sample
sites (C, G, 1A, 2A, 3A) still vary significantly, ranging from 53.9 x
10'”5 emu/cm3 to 652.0 x 10"5 emu/cm3, with an average intensty of 322.8
x 10'5 emu/cm3. Due to the the large variation in the intensities, the
average intensity of 322.8 x 10'5 emu/cm3 is used as an initial

approximation of the body's remanent magnetization.

Susceptibility

 

The magnetic susceptibility measurements are consistantly weak,

ranging from 4.0 x 10’5 emu/cm3 to 30.0 x 10’5 emu/cm3, (Table 3).

Table

27

3. Average Remanent Magnetization Intensity, Susceptibility, and

Q-Ratio for Each Sample Site.

 

 

 

Sample JR JRC k 31
Site (x 10’5) (x 10'5) (x 10‘5) 10-5) Q
1 -- -- 8.0 --- ---
2 -- --- 4.0 --- ---
A* 1062.0 767.0 14.0 7.7 99.6
B* 5952.0 4731.0 30.0 16.5 286.7
C 674.0 652.0 9.0 5.0 130.4
D* 10.8 13.4 --- --- ---
E* 18.1 23.2 14.0 7.7 3.0
F* 8252.0 8293.0 15.0 8.3 999.2
C 195.0 195.0 10.0 5.5 35.5
1A 348.0 368.0 9.0 5.0 73.6
2A 353.0 345.0 10.0 5.5 62.7
3A 56.4 53.9 4.0 2.2 24.5
Ave. 325.3 322.8 8.4 4.62 65.3
Ave. Q = JR/JI 69.9 (Range 25 - 130)
JR Natural Remanent Magnetization Intensity
JRC Remanent Magnetizatiton Intensity (Cleaned)
k Susceptibility
JI Induced Magnetization (JI - kHe)
Q Koenigsberger Ratio (JR/J1)

*Eliminated

28

These remarkably low susceptibilities are similar to those found in
Keweenawan acidic intrusives and sediments, and in Precambrian
metadiabases and greenstones (Hinze, O'Hara, Secor, and Trow, 1966).
Induced magnetic anomalies due to such low susceptibilities are

extremely weak.

Koenigsberger Ratio (Q-Ratio)

 

If the induced and remanent components of magnetization are
comparable in intensity, then the Q-ratio (remanent intensity to induced
intensity) can be an important tool in magnetic modeling. By holding Q
constant and equally increasing or decreasing the remanent and induced
components of magnetization, as shown in Figure 11, first order modeling
can be done along one specific magnetization axis. In this study the
extremely low induced component of magnetization (4.6 x 10‘5
emu/cm3) is negligible compared to the unusually high remanent
magnetization (322.8 x 10"5 emu/cm3). The Q-ratio is very high
indicating that the remanent magnetization is dominating the induced
magnetization (Table 3). In this case, magnetic modeling is completely

dependent on the remanent magnetization.

Summary

The Michigamme Intrusion is ideal for a case magnetic modeling
study considering remanent magnetization. The characteristic remanent
magnetization orientation is reversed and the remanent magnetization
intensity is much larger then the induced magnetization, as indicated by
the high Q-ratios. Although variations have been measured in the

magnetic properties of the intrusion it is assumed that these variations

29

   
 

Resultant Axis of
Magnetization

Figure 11. Total magnetization axis.

30

have been sufficiently filtered out to approximate a magnetic

homogeneous body with the following properties;

1) Characteristic remanent magnetization orientation
Inclination -51.8

Declination 76.2

2) Remanent magnetization intensity
Ave. 322.8 x 10'5 emu/cm3

Range 53.9 x 10'5 emu/cm3 - 652.0 x 10’5 emu/cm3

3) Susceptibility

k = 8.4 x 10"5 emu/cm3

4) Q-Ratio
Ave. 690 9

Range 25 - 130

MAGNETIC MODELING

The theoretical framework for this study is based upon the magnetic
modeling of vertical prism-shaped bodies with arbitrary polarization
(Bhattacharryya, 1964). Computer modeling of vertical prism-shaped
bodies with arbitrary induced polarization was demonstrated by Whitehill
(1973). Shanabrook (1978) expanded Whitehill's computer method to more
accurately describe arbitrary polarization as the vector addition of an
induced magnetization component and a remanent magnetization component.
The modeling program (Shaloci) developed by Shanabrook (1978), with an
addition by the author to approximate dipping bodies is used to model

the Michigamme Stock.

Theoretical Model

 

The magnetic field H(x,y,z) at a point P(x,y,z) exterior to a
vertical shaped-prism, described in Figure 12, is: (Bhattacharryya,
(1964).

The total magnetic intensity of a vertical prism (T).

 

T = Ip [LHx(x,y,z) + MHy(x:Y:z) + NHz(x9Y9z)]

u1 v1 w1

N r+v -1 uv
HX(X:Y°Z) = II) 3 1°8(—"r-v) + Mlog(r+w> + Ltan m1 /uo /vo /wo
l l 1
N r+u -1 uv u V W
Hy(xa}'9z) = 1p [-2- 108(;:) + Llog(r+w) = Mtan m} / uo/ Vo/ W0
M r+u L r+v -1 uv U1 V1 W1
Hz(x,y,z) a Ip 'E'log(;:;) + Elog(;:;) - Ntan.;;] /uo /Vo /Wo

31

32

Where: Ip = intensity of magnetization of the prism.
>
(L,M,N) = direction consines Ip

r = (u2 + v2 = w2)

U0 = X0 ‘X U1: X1 ‘X
V0=yo‘y V1=yl'y
W0 = 20 - Z W1 = 21‘ Z

>

When: Ip is due to an induced polarization
>
I

= the magnetic susceptibility of the prism

e = the earth's magnetic field

>
When: Ip is due to an induced magnetization component and a
remanent magnetization component.

> > >
Ip = k'Fe + JR

Where: JR = remanent magnetization of the prism.

JR = (Jy + Jy + Jz) = ( J cosI cosD + J cosI sinD + J sinI)

J = intensity of natural remanent magnetization
I = inclination of the remanent magnetization
D = declination of the remanent magnetization

The vertical magnetic field intensity of a vertical prism (Hz)
used in this study:

 

M r+u L r+v -1 uv u1 v1 w1
Hz(X.Y.Z) = Ip [’2‘ 1080;?) +§Log(';) - NTan (Ry-)1 /no /VO /We

>
Where: I = k'

33

A)

 

 

 

 

 

 

 

 

8:1(x1.'1. 1})

 

PARAMETERS
PRISM LOCATION
Coordinate Grid Size Cordinate of each Prism
Columnsly) 20 Points “rum“ (kph)
Rowslx) 20

Unit One 250 feet

PRISM MAGNETIC PROPERTIES

Induced Component Remanent Component
latitude Declination
longitude Inclination
Susceptibility Intensity

Figure 12. Computer model: A) Coordinate system, B) Parameters.

34

Computer Model

 

The program Shaloci, see Appendix A of Shanabrook (1978), is used
to calculate the vertical magnetic field generated by a series of
vertical prism-shaped bodies, defined by the parameters shown in Figure
12.

A separate input program for Shaloci was developed by the author to
arrange a system of prisms to approximate a dipping cylinder, (See
Appendix D). A series of 15 rows of stacked prisms, each row containing
9 prisms inscribed in a circle, are used to define a cylinder (Figure
12a, b). Given any dip and dip direction the rows of prisms are moved
an appropriate amount to describe the desired dipping cylinder. Due to
a 50 prism input limitation into Shaloci, the stacked prisms are divided
into 3 vertical levels each containing 45 prisms. Each level is run
through Shaloci separately and the outputs are combined.

The vertical magnetic field output generated by each model is
displayed at 400 positions on a 20x20 matrix over the model, Figure 13.
The resultant magnetic intensities are then contoured by the program

SURFACE II, (See Appendix E for the program commands).

Approximations

 

By being aware of approximations made in a computer model the error
spread produced can be controlled. The reduction of error is a cost
factor for the user, errors in a computer model can vertually be
eliminated if enough computer memory and time are reserved for compiling
the model. Approximations encountered in this study are listed below:

1) Approximation of a dipping cylinder using an assortment of

vertical prisms.

35

Figure 13. Prism Model for Dipping Cylinders.

36

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A) l n 1 1 n 1 a L 1 1 14 a l a
V I U j I fl T r v fl iii. v .fi J
x .. Map View
4..
up Ly
_ Azimuth
‘ r=_1 /
dr
db =
q-
l 1 I l l n A L A 1 pl 1 j n 1
I I t f U U I r T T I I r v r I
Y
B) Profile Y
T VB
levelone Plunge
1000T-
leveltno
1.
2000 jb %F—
3000'“ levelthree
l L
4ooo~1~ l—_.__I i

 

Feet V

 

 

37

2) The number of data points (Grid Size) that the magnetic

intensity of the anomaly are calculated for over the body.

3) The grid size, type of search pattern, and weighting factor

used when regriding the data for contouring.

All of these approximations can be made more efficient by increasing the
amount of data put into the model and by requiring more data to be
calculated for the output.

It is believed by the author that an appropriate balance between
cost and efficiency has been achieved for this study. It is noted here
that a certain amount of flexibility is reserved for the final

interpretations of the models.

MICHIGAMME STOCK

The Michigamme intrusion was selected to show the importance of
remanent magnetization in magnetic interpretations, and to exhibit how
easily these interpretations can be performed with a computer, for the
following reasons:

1) The intrusion was believed to possess a reverse-remanent
magnetization component, which could be confirmed by analyzing
samples exposed at the surface.

2) The geometric structure of a stock can easily be modeled by a
computer.

Analysis of the magnetic properties of the stock (Chapter 2) have
shown that the remanent magnetization is completely dominant, as
indicated by the unusually intense remanent magnetization and extremely
weak susceptibility (Table 3). It has also been shown that the remanent
magnetization is reversed (Table 2). Since the body is dominated by an
unusually high remanent magnetization and the field is not parallel to
the earth's present field, it is not possible to mistakenly model the
anomaly using the susceptibility method. It is concluded that there is
a unique anomaly for this structure that is totally dependent upon the
intensity and orientation of the remanent magnetization.

Sufficient evidence indicates that the body is a stock (Klasner,
1973) however it is not known in what direction the stock is dipping.
Using the remanent magnetization intensity and orientation determined in

Chapter 2, modeling of the stock was performed to decern which way the

38

39

body dips. To demonstrate how this modeling can be performed easily by
a computer, the magnetic anomalies due to various dipping stock
directions were determined by the computer method previously outlined
(Chapter 3). To determine the most appropriate model of the intrusion
the computer modeled anomalies were compared to the ground magnetic
survey anomaly of the Michigamme Stock (Figure 5).

TWO sets of models for the different dipping stocks were performed
using the remanent magnetization orientation expected for a Lower
Keweenawan Formation (Table 3) and the remanent magnetization
orientation measured (Table 1). Because the measured remanent
magnetization orientation varied from the orientation expected for a
Lower Keweenawan Formation, both sets of models were performed to test
the best possible fit for the observed ground magnetic survey anomaly
for the Michigamme Stock (Figure 5).

The geologic and geophysical parameters used for the models are

outlined in Table 4.

Computer Models of the Michigamme Stock

 

Mbdels of vertical stocks with varying remanent magnetic
intensities were first done to determine the best approximation for the
remanent magnetization intensity of the Michigamme Stock. This was done
by comparing the maximum and minimum amplitudes of the model anomalies
to the amplitudes of the observed anomaly (Figure 5), until the best
match was found. A remanent intensity of 150. x 10"5 emu/cm3,
well within the range of intensities measured for the intrusion (Table
3), was found to be the best approximation for the remanent
magnetization intensity of the Michigamme Stock. This intensity is used

for the following models.

40

Table 4. Geologic and Geophysical Parameter Values Used in Computer

Models I & II.

 

 

 

Geology

Geometry (Stock)
Diameter 1000'
Depth. to Bottom 4000'
Dip (7) 67.0°

Geophysics

 

(Induced Magentization Component)
Orientation (determined from Earth's magnetic Field)

mtitUde 4605
Longitude 88.0
Intensity
Susceptibility k = 8.4 x 10"5 emu/cm3
(Remanent Magnetization Component)
Model I
Orientation
Inclination I = -65.0
Declination D = 100.0
Model II
Orientation
Inclination I = -51.8
Declination D = 76.2
Intensity (Jr)
Magnitude
Range 53.9 - 652.0 x 10-5
Ave. 322.8 x 10'5 emu/cm3

Best Fit Value. 150.0 x 10‘5 emu/cm3

Klasner

Topo. Map

This Study

From Lower
Keweenawan
Paleopole.

This Study

This Study

 

41

Comparisons of the computer model anomalies to the observed anomaly
of the Michigamme Stock (Figure 5) are based on the following criteria:

1) The spatial orientation of the maximum amplitude to the minimum

amplitude.

2) Visual comparison of the maximum and minimum amplitudes of the

anomalies.

3) Visual comparison of profile curves through the maximum and

minimum amplitudes.

The first set of models (Model I), using the remanent magnetization
orientation expected for the Lower Keweenawan Formation, are shown in
Figures 14 & 15. Model I A, B, C and D (Figure 14) respectively
represent a stock dipping 70 degrees to the north, east, south, and
west. Comparison of the spatial orientation of the maximum and minimum
amplitude show Model IA, of a stock dipping to the north, to be the only
model that spatially fits the observed anomaly for the Michigamme Stock
(Figure 5). However comparison of the maximum and minimum amplitudes
show the maximum amplitude to be less then needed for a good fit. Model
I E, F, and G (Figure 15) respectively represent a stock dipping N20E,
70, 50, and 30 degrees. By decreasing the amount of dip toward the
north a better match of the maximum amplitude is observed. Profile
comparisons (Figure 18A) also show a better curve fit for a stock gently
dipping to the north.

The second set of Models (Model II), using the remanent
magnetization measured in this study (Table 1), are shown in Figures 16
& 17. Model II A, B, C, and D (Figure 16) respectively represent a
stock dipping 70 degrees to the north, east, south, and west.

Comparison of the spatial orientation of the maximum and minimum

amplitudes show Models II A, B, and D, of a stock dipping to the north,

42

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IX Y II ¢//,
r- ,7," '
r P
' . / a)" 1
a?
r 1

L
1 4
f
T 25
I o-—-<
[ r ‘\
E DID ”79 r . 1 1 . 1 i i i i n .l" 2.4 A * ‘ J L
P)" c‘T—fi———v r w 1 r '.v 1 1'
i 4 r
r ‘ "
I ,5: °\;

4 b I 7 7 , I -4 ‘

J ‘ 4
F 1 p I 1;: ' 1
r f o ‘
only“ snipe iii 47 1 L A t
Figure 14. Model I. For a cylinder dipping 70 degrees in the: A) North

direction, B) East direction, C) South direction, and D)
West direction.

43

 

 

 

 

 

 

 

 

 

 

 

 

90

mm a
w:

b

D

bbbbbbbbbb

 

 

E)

Model I. For a cylinder dipping in the NZOE direction:

Figure 15.

70 dip, F) 50 dip, and G) 30 dip.

44

 

 

 

f T Y—Vfir ff fi fir 1 I' Y 1 V f 7V ‘T u
l

‘f—fi—Tfi—fifiY v Y Yfi’Y‘T f Tj V V

 

 

 

 

 

 

 

 

 

fl Y—T ff f I;

 

 

. ,_f ft f ..... 0" . s—r
II II
+c . l
i
O
, j 29
$9 50 JFY o " Os. ‘
1*— 0. I ‘3 l A\ e I
‘ f 4A\ ‘ ‘3 if, ,fi 4
Wm 4““ .
‘h -( IN
I '. 30¢) a: ’ ‘0 0 ‘
22:“ w --...,.¢.~ "' “Le "<3 ~ 1
x V V‘-
"\\r ‘0 V 4
001 1 I so ‘
so 05-
se '25 25 j
I I ‘ ’ a l
"'1”?! . . A .i L L H Li ext ."3 I"! 1 L nail. ti ”if/N

 

 

 

 

 

 

l
|

Figure 16. Model II. For a cylinder dipping 70 degrees in the: A)
North direction, B) East direction, C) South direction, and
D) west direction.

45

 

 

 

 

 

 

 

 

 

 

 

   

rfi' VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
PIE hIf
r * r
l» 4 P fag I
l 4
s 4 1
F q ‘0 fl 4
x
l < /\ a
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Q] m 4 IE ‘(r‘ \. I 1
N i \ - "’
l . I ék ‘ £T“jb ? ‘
b 4 7 P O 0‘; f 4
_ .n' Cd" 7
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It}... 19L L \ AL A 0: %+ 4 L A + 1L J. g
as '\\ II // \ J
F 4 > 4
\fl
' .50 Q 1 ’ g? 3 1:7 ‘
> 1 .
. 4 P 4
> 4 b 4
r 1 L 4
b i b :3 <
r l r 4
L :3 1 > o/‘A
{ b 4
4 b 4
L .
a.“ ‘ ‘ i
1 p 1
25 I
+ 35
i
> t 4 b 4
0'? Ly“ LLLLLLLLLLLLLLLL o? “A A A A A A Li L A g A A A A A 4

 

 

 

 

 

 

Figure 17. Model II. For a cylinder dipping in the N208 direction: E)
90 dip, F) 70 dip, G) 50 dip, and H) 30 dip.

 

46

Figure 18. Model I & II Profiles.
A) Model I Profiles: For a cylinder dipping in the
' N20°E direction 70°, 50°, and 30°.
B) Model II Profiles: For a cylinder dipping in the
N20°E direction 90°, 70°, 50° and 30°.

60C)fi['
ADO-e

2004~

 

47

 

—200~~

-400«_

-600 —n—

-800 ul—

‘IOOOHP

 

4200J-
CIIIIS

booT
400~~

200—-

  

\\ Observed

   

\ .Io-ah
\

IIII

 
 

1000
l

 

MODEL"

IEII

 

-200dr
-400JP

-bOO--

I

-800%

-IOOO~-

 

~I200‘b
CIIIIS

   

Observed
Inonah

 

IIII

  

1000
1

 

lIII

48

east, and west, to all spatially match the observed anomaly for the
Michigamme Stock (Figure 5). In this set of models a better comparison
of maximum and minimum amplitudes is observed; with the closest match for
a stock dipping to the north. Models II E, F, G, and H (Figure 17)
respectively represent a stock dipping N20E, 90, 70, 50, and 30 degrees.
The best match of maximum and minimum amplitudes is observed for the
vertical stock. However, profile comparisons (Figure 183) show a better

curve fit for a gently dipping stock.

Discussion of Results

 

The best set of models for the Michigamme intrusion are observed for
those models using the remanent magnetization orientation measured
in the study (Table 3). the spatial orientation of the maximum and
minimum amplitudes and the match of the amplitude magnetudes indicate
that Mbdel II E (Figure 17E), for a vertical stock, to be the best match
to the observed anomaly for the Michigamme Intrusion (Figure 5).
Variations observed in the profile shapes (Figure 18) are assumed to be
due to an incorrect initial aproximation that the Michigamme Intrusion is
a perfect cylindrical stock. Approximations encountered in the computer
modeling require flexibility in the final interpretation, as discussed in
Chapter 3. It is more appropriate to interpret the intrusion as being a
stock that is vertical or steeply dipping in the northern direction.
This is in agreement with the predictions of Klasner (1973), as seen in
the cross section view shown in Figure 1.

Even though the best models were achieved using the remanent
magnetization orientation measured in the study, first hand
approximations using the expected remanent magnetization orientation for

the Lower Keweenawan would have sufficed to initially model the stock.

CONCLUSION

It has been shown in this study that remanent magnetization can be
a significant factor in the total magnetization of a body, and that

magnetic modeling of these bodies can be performed easily with a

computer. In the case of the Michigamme Intrusion it was found that the

remanent magnetization was completely dominant over the induced
‘magnetization, and that the remanent field was reversed compared to the

In this particular case it is not possible to
The

earth' 8 present field.

rnistakenly model the body using the susceptibility method alone.
nuagnetic anomaly associated with the Michigamme Intrusion is completely
title to a remanent magnetization, which was easily modeled using the
computer method outlined in Chapter 2.

It was also shown that a detailed study of the bodies magnetic
properties is not completely necessary to model the body, if enough
geologic and geophysical information is available for the study area.
111 time case of the Michigamme Intrusion, magnetic modeling could have

been done to decern the structure of the body even if the body were

buried, for the following reasons.

1) The spatial orientation of the maximum and minimum amplitudes
for the magnetic anomaly deviate from the orientation expected
at that latitude and logitude; thus indicating a remanent
magnetization component.

2) TPhe magnitude of the minimum negative amplitude is larger then

the maximum positive amplitude, indicating a large

reverse-remanent magnetizat ion intensity.

49

50

3) The observed anomaly is magnetically associated with east-west
trending reversely polarized dikes of Lower-Keweenawan age, for
which paleopole information is available.

4) The susceptibilities for various rock types in the area are
available.

With the information above, magnetic modeling can be performed until the
best combination of remanent magnetization and susceptibility is found.
If the susceptibility is known, as in this case, modeling of the body
was shown to be sufficient by adjusting the remanent magnetization
intensity and using the remanent magnetization orientation expected for
a Lower Keweenawan Formation.

Although it may not be necessary to perform a detailed field study
of the body in question, it is always desirable to obtain the maximum
amount of hard data possible to create the best model for the given

situation.

APPENDICES

51

APPENDIX A

Whole Rock Analyses, and Trace and Rare-Earth
Element Concentrations (PPM)

52

53

.AmnV mango:

.mvumvamum weaved sows momhama< 80 0am mum

.ooaoomouoaHm hamlx an voafiauouma «UH

 

 

 

 

 

00.0 m.HN m0. mq.H mH.N 0m.0 0e m.m~ 00 we 0 n0 OHH 0 ONNH Amy «:24
00.0 m.- 00. qm.m Hq.m «5.5 we 0.0m Nm me 0 mm HNH 0 mama A0000 NIMmN
0m.m 0.HN 0m. Hm.fi mm.~ 0N.m we 0.q~ mm me 0 mm 0~H 0 Nmmfi A0000 Human
Nam mod :4 0% am 50 mo ma Huo 00 a: :0 cm . Ho fiz .oz
madamm
.Amev macaumuuaooaoo uaoaoam :uumMIoumm 0cm mommy
00.00 0H. «N. m0.~ qu.~ ~<.H 0m.m H0.m 00.0 eq.HH em.m 00.0H 00.00 Amv NazA
mm.00H NH. mm. mm.~ mm.m Hm.H mm.m mm.0 0m.m ~n.0~ m0.~ Nq.mH Hm.Hm A0000 NiMmN
Hm.mm 00. on. N0.N 00.N m0.~ mm.m HH.N 0m.m 00.~H 0m.~ mm.mH mm.~m A0000 fiixmw
Hence on: moma mesa Hog owe ommz emu ow: owe momma momaa Noam .oz
madamm

 

momhama< xoom oHozz

APPENDIX B

Corrected Vertical Magnetic Intensity Data

54

55

 

 

0.0mm“ 0.00?0 0.000m won 00 0.hm0? 0.mmu0 0.0000 0H0 0m
0.0mNN 0.0000 0.000M «on on 0.0%h 0.mmom 0.0000 000 am
0.DNMN 0.0000 0.00m? mfim mm 0.0M? 0.mmhm 0.0000 moo N
0.00NH 0.00?0 0.00m? ?fiw hm 0.m0N 0.mmmm 0.0000 300 mm
0.000“ 0.00N0 0.00m? Mum 0m 0.0M” 0.mmmm 0.0000 000 N
0.0mn 0.0000 0.00m? Nfim mm 0.h? 0.mmHm 0.0000 moo mm
0.0m? 0.00mm 0.00m? «Hm ?m 0.0a! 0.mmO? 0.0000 ?00 ?N
0.00N 0.000m 0.00m? 0am mm 0.?0! 0.mmh? 0.0000 moo mm
0.0? 0.00?m 0.00m? 00m mm 0.0H 0.mmw? 0.0000 N00 mm
0.0”! 0.00Nm 0.00m? mom Hm 0.0mm: 0.0m?? 0.0000 «00 ”N
0.00“! 0.mm&? 0.00m? mom on 0.0mfii 0.mmm? 0.00?m 0am 0m
0.0m“! 0.00m? 0.00m? 00m 0? 0.00! 0.mmm? 0.00?m 000 0H
0.00mi 0.000? 0.00m? mom m? 0.0m: 0.600? 0.00?m 000 ma
0.00“! 0.00m? 0.00m? ?0m .N? 0.00 0.mmam 0.00?m mom he
0.0mm! 0.mmM? 0.00m? mom 0? 0.0mH 0.000m 0.00?m 000 0e
0.0ami 0.00m? 0.00m? Now m? 0.00% 0.mmmm 0.00?m mom m”
0.0mm: 0.000? 0.00m? How ?? 0.0K? 0.mmam 0.00?@ 70m 0s
0.000M 0.mmm0 0.0000 NH: M? 0.mmm 0.mm0m 0.00?m mom mfi
0.00m“ 0.mmm0 0.0000 Ha: N? 0.000m 0.mmq0 0.000m mom NH
0.0mm 0.mm00 0.0000 0H0 H? 0.mmufl 0.m0m0 0.00?m H00 Hg
0.0mm 0.mmmm 0.0000 000 0? 0.00am 0.00?0 0.000? 0H0 0H
0.0mm 0.mm0m 0.0000 000 am 0.mmmfl 0.mmfi0 0.00m? 000 &
0.00fi 0.mM?m 0.0000 Roz mm 0.0AA 0.mmem 0.000? 00¢ m
0.00 0.mmmm 0.0000 000 mm 0.0a? 0.mmhm 0.000? A00 A
0.0 0.000m 0.0000 mom 0m 0.0mm 0.0000 0.000? 00¢ 0
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0.000: 0.000¢ 0.000¢ 00N 000 0.0001 0.000¢ 0.000¢ 00> 00¢
0.000: 0.000¢ 0.000¢ 000 .000 0.000: 0.000¢ 0.000¢ 00> 00¢
0.000: 0.000¢ 0.000¢ 000 000 0.000: 0.000¢ 0.000¢ 00> 00¢
0.000: 0.000¢ 0.000¢ 000 000 0.0c0: 0.000¢ 0.000¢ 00> 00¢
0.0000: 0.0000 0.000¢ «00 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 00N «00 0.00 0.000¢ 0.0000 00> 00¢
0.000: 0.0000 0.000¢ 000 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 000 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.0000 0¢> 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.0000 0¢> 000 0.¢00: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.0000 00> 000 0.000: 0.000¢ 0.0000 ¢0> 00¢
0.000: 0.000¢ 0.0000 00> 000 0.000: 0.000¢ 0.0000 00> 000
0.0001 0.000¢ 0.0000 00> 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.0000 00> 000 0.¢00: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.0000 o¢> 000 0.0001 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 00> 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 00> 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 00> 000 0.000: 0.000¢ 0.0000 00> 00¢
0.000: 0.000¢ 0.000¢ 00> 000 0.000: 0.000¢ 0.0000 00> 00¢

u u x Jfimgfid a“ 0 u x 000.0. :1

 

 

 

 

 

.0000 00>h=0

000ma0u:0 00000005 0000uu0> 00000uuoo

64

 

 

0.000! 0.0000 o.oo¢¢ «00 000

o.m¢0l 0.0000 0.0000 000 000 0.000! 0.0000 0.00?? «00 000
0.000! 0.0000 0.0000 000 000 0.000! 0.0000 0.00?? «c0 000
0.000! 0.0000 0.0000 000 000 0.000! 0.000¢ 0.00?? «00 ¢mm
o.¢omi 0.0000 0.000¢ mm0 000 0.000! 0.000¢ 0.00?? €00 000
o.¢m0i 0.0000 0.000¢ mN0 000 0.000: 0.000¢ 0.00?? €00 000
0.0001 0.0000 0.000¢ m00 000 0.000! 0.000¢ 0.00¢¢ «00 000
0.000! 0.000¢ 0.000¢ m00 000 o.¢mml 0.000¢ 0.00?? «00 000
0.000! 0.000¢ 0.000¢ m0o 000 o.¢¢01 0.000¢ o.oo¢¢ «mo 0¢w
0.0001 0.000¢ 0.000? 000 000 0.000! 0.00?? 0.00?? «00 m¢m
0.00m: 0.000¢ 0.000¢ mho ¢0m 0.00mi 0.000¢ 0.00?? «00 0¢m
0.000! 0.000¢ 0.000¢ m0o 000 0.000! 0.000¢ 0.00¢¢ «no 0¢m
0.00m! 0.000¢ 0.000¢ mmo 000 0.000! 0.000? o.oo¢¢ «co mcm
0.000! 0.000¢ 0.000¢ mco 000 0.000! 0.000¢ o.oo¢¢ «no ¢¢0
0.000! 0.00¢¢ 0.000¢ mmo 000 0.000! 0.000¢ 0.00?? cmo 000
0.000! 0.00?? 0.000¢ mmo 000 0.000i 0.000¢ 0.00?? «00 New
0.000! 0.000¢ 0.000¢ m0o 000 0.000? 0.0000 0.0000 0m) 0¢m
n > u 0:... ‘. ~ » u ‘02... flu

 

 

 

 

 

.muuv 0o>u=m

0u0mcoua0 00006003 0mo0uuo> wouuouuoo

APPENDIX C

The Remanent Magnetization Orientation and Intensity for Each
Sample: NRM, Thermally Cleaned, and A.C. Cleaned.

65

66

m80\saw mIoH x m.nq zufiwcwucH vmcmmao wwmuw><

 

 

 

 

 

o.~e- “.mofi n.am- ~.Hw m.mm o.oq- m.ow mwmum><
-- -- -- o.~q H.qq- ~.~m N.aq w.~q- o.mw onm
-- -- -- ~.He ~.qq- a.qo m.nq m.oq- q.q- Amvm
-- -- -- m.oo m.~q- m.qn m.oo N.m- m.mo Aqvm
-- -- -- «.mq ~.~q- o.m~ m.mm m.mm- o.m~ Amvm
-- -- -- «.mn o.qm- m.Hm m.mm ~.oq- a.ao fi~vm
e.Hm o.~e- n.~ofi -- -- -- o.qw n.~q- o.ou Aden
mau\sam mIoH x .ucH .uma mao\=am mIoH x .ocH .uwa mao\:am mIoH x .ocH .oma maaamm
muamcwucH muamcwucH muwmcwuaH
Aemcmmau .o.<v Acmcmmflu afifimauwnev Azmzv
m mufim mamamm
mEU\sam mlofi x on. u mufimcmucH vmcmwao wmmum><
m.om- o.NHH o.om- H.HmH oo.~ o.Hm- w.mm~ mmmum><
-- -- -- -- ~.mfi- ~.am~ -- n.q- ~.qq~ on<
-- -- -- hm.q m.eo m.oo~ em. m.-- «.mmfi Amv<
-- -- -- ow.m m.m- m.mm~ an. N.~o- o.a- Aev<
-- -- -u aq.c H.0N- o.omH no. o.n- H.5mfi Amv<
mm.~fi o.ow- n.0nfi -- -- -- ow.“ n.n- H.an Amv<
o~.o~ o.-- H.q¢H -- -- -- cm.~ N.w- m.e- A~v<
mao\sam mIOH x .UGH .uwo mEU\:am mloH x .ocH .umn maU\sam mloH x .ocH .owQ quamm
hufimcmuaH mufiwawuaH huawamucH
Aumammfiu .o.<v Aemammao mHHmaumnev Azmzv

 

a 5 £3.

67

 

 

 

 

 

em.mfi m.~o- m.- Hm.o~ «.mm- H.6m mwmum><
III III III an.q~ «.moI ~.nm mm.o~ w.nql o.mm Amvn
-- -- -- Ha.HH ~.am- N.Ho mN.~H m.oq- w.wm Aden
mEU\sam mIoH x .ucH .umo mao\sam mIoH N .ocH .uma mao\=aw mica x .oaH .umo mHQEMm
mufimcmuaH mufimawuaH mufimawuaH
Aemammfio .o.<v Auuamoao maamaumnev Azmzv
a mufim oaaamm
mao\:am mIoH x mm.o u xufimcwucH wmcwwau mwmum><
o.~q| o.oo m.nmI o.~o «5.0 o.qu ~.qo mwmuw><
-- -- -- mm.q o.eq- n.qm o~.q H.mq- m.mm ono
-- -- -- om.m ~.me- H.5m ec.m n.~m- H.~o Amvo
-- -- -- mm.m H.am- «.mo oo.q H.5q- w.~c Aqvu
-- -- -- qw.o~ ~.qm- ~.qo o~.HN o.mm- o.~o Amvo
III III III mm.m H.o~I m.¢e ~¢.m m.wmI 0.50 Amvo
No.fi o.~q- o.oo -- -- -- qw.~ n.0q- a.we Afivo
mEU\sam mica x .05H .own mao\=Em mIoH x .oaH .uwQ mEU\DBw mIoH x .oaH .owa quamm
muwwamucH mufiwcwucH mufiwamuaH
Awmawmao .u.<v Avwamwau haamaumnhv Azmzv

 

o mufim «Haamm

68

mao\:aw mIoH x m.mw u zufimnmucH wwcmwau wwmum><

 

 

 

 

 

H.m- m.wHH o.q- m.qu m.~w o.mm- o.qu mmmum><

-- -- -- m.~ q.-- m.ooH w. H c.9q- o.qu Have

-- -- -- o.ow m.mq- N.emH «. em n.5q- o.me qum

-- -- -- n.5m H.¢H- «.meH H .m: ~.¢H- ¢.HqH Amen

-- -- -- n.0eH m.oH- «.mnH m. NNH “.0H- ~.mmH Hmvm

m.ww H.m- w.wnH -- -- -- m.mm o.om- w.omH Hva
Eo\sam Ca x .ucH .owa EU\:Em IoH x .oaH .umo ao\:am ION x .uaH .umo wfiaamm

m m- m m m m
hufimawucH mufimcmucH hufiwcwuaH
HumcmmHu .o.<v HumammHo HHHmaumsav Hzxzv

m muHm wHaamm
~.mm m.om- q.qn oH.Hw c.~m- o.~m mmmuo><

-- -- -- -- -- -- -- o.H- n.mo Hovm

-- -- -- Hm.o~ H.Hm- m.~n oH.NH o.m¢- ~.om Hmvm

-- -- -- o~.q~ m.we- a.H~ w~.mH w.oe- “.mH qum

-- -- -- Hm.Hm m.mm- m.mm -.¢m ~.mq- o.ow Hmvm

-- -- -- N.mH m.wm- m.Ho mH.NH ~.Hm- m.HH HNVm

-- -- -- m.qH -- -- ma.HH H.m~n H.H Hva
mEU\:Em mIoH x .ucH .own mau\saw mIoH x .ocH .qu mao\sam mIoH x .ocH .uoa mHaamm

mufimcwuaH AufiwcwucH mufiwcmucH
Avwcwmao .o.<v Awwcmeo xaamaumnHv Azmzv

 

m muHm oHaamm

69

 

 

 

 

 

mEU\sam mIoH x mo.m u xufiwcwucH vwcmmau mwmum><
o.Hq- ~.wm a.wm- N.~m o.~q- m.qm mmmum><
In- III III wm.q “.mmn m.on mm.q o.omI «.0n AeV<H
III -II III oo.m N.enn o.mq om.~ «.nmI «.me Amv¢H
-- -- -- om.m ¢.mm- m.~m wm.m n.Hm- w.mm HNV<H
Hm.m c.5q- ~.wm -- -- -- m~.m ~.om- H.am HHV<H
EU\DBQ IOH N .UGH ouwQ SUE-.80 IOH N oUGH .03 EU\DBm O.— N .UGH gown wHQEMm
m m m m m m-
hufiwcwucH hufiwcmucH zufimamuaH
Hemameo .u.<v HemammHo aHHmsumnev Hzmzv
«H muHm oHaamm
ma.H m.qm- ©.~n owmum><
mm.m N.wo- m.m~m Hove
Hm.H m.nn m.m~ Amvu
we. m.mmI o.mm~ Aevu
um.m «.mI 0.5m Amvu
em. N.oI w.wn Amvo
aoccmm aoeamm aoucmm aoecmm Hm.N m.Hm- ¢.HwH HHvu
mEU\:Em MIOH x .ucH .omo mao\=aw mloH x .03H .umn mEU\=Em mIoH x .UGH .qu mHQSMm
mufimcwucH mufimcmuaH mufimawuaH
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m.mm m.mo- m.mm m.~o- “.mm mmwum><

-- -- -- q.~e m.wn- o.oa H.0n m.oo- a.cw Anv<m

-- -- -- q.~e o.Ho- o.om a.~m H.0m- n.0m qu<m

-- -- -- o.aH -- -- m.eq -- -- Hmv<m

-- -- -- H.Hq n.5m- o.H~ m.~q 5.0m- m.on Haven

-- -- -- 0.55 m.qo- H.m~H o.mm m.~o- ~.qHH HHV<m
mEU\=aw mIoH x .oaH .omo mao\=am mIOH N .oaH .own mao\saw nlo~ x .ocH .owa maaamm

muamcmucH AufimcwuaH %ufiwawuaH
HemcmmHo .o.<v HemammHo HHHmaumspv Hzmzv
«m muHm mHaamm
Mm mao\:am mIoH x mq.mu mufimcwucH vmcmmau mwmum><

m.ce- m.meH «.50- w.omH o.mo- o.mmH mwmum><

-- -- -- -- -- -- 0H.q o.qm- m.ooH HQV<N

-- -- -- Nq.e m.mo- H.wm m~.q N.mo- m.mm Hmv<m

-- -- -- «a.H H.Heu o.~mH No.~ o.wmu o.mmH qu<~

-- -- -- Nq.m m.wH- m.moH He.m «.mH- «.mmH Hmv<~

-- -- -- o~.q H.HNn m.HmH 0H.e m.o- o.qu H~V<~

HH.m m.oo- m.meH -- -- -- mH.m m.mo- H.HmH HHV<N
Eu Bum IoH x .ocH .own So saw IOH x .ocH .owo so new IoH x .ocH .umn mamamm

m H m m H m m \ m
muwwawucH hufimawuaH muwmsmuaH
HumammHu .o.<v HemcmmHu mHHmaumsev Hzmzv

 

«N muHm mHaamm

APPENDIX D

Computer Model Listing

71

72

SCOOPFMT

100=PHILLIPS,PN606213 ,RGl,CM120000,JC1500.
110=ATTACH,TAPE88,LEVELONE,Pw=MAC.
120=ATTACH,PREFIX,BINPREFIX,PW=MAG
130=ATTACH,ONE,SHALOCI,PW-MAG.

140=PREPIX.

150=REwIND,TAPE99.

l60=ONE,TAPE99.
170=CATALOG,TAPE7,WESIO,PW=MAG,ID=WES,RP=30.
180=REWIND,TAPE7.

190=COPY,TAPE7,0UT.

200=DISPOSE,OUT,PR.

 

200,000001=*EOROO
220=00. 70.

230=*EOR.

PREFIX

100a PROGRAM PREFIX (INPUT,TAPE77=INPUT,TAPE88,TAPE99,OUTPUT=TAPE99)
110a DIMENSION X(2,45),Y(2,45),Z(2,45),EXTRA(13),OPTIONS(5),PROP(4,46)
120= DATA RADCONV/57.2957995/

130= READ(77,1) AZIMUTH,DIP

140= READ(88,2) (EXTRA(I),I=1,3)

150= READ(88,3) IRow,ICOL,EXTRA(4)

160= N=1

17o=3o CONTINUE

180= READ(88,15) FLAG,(PROP(I,N),I=1,4)

190= IF(FLAG,EQ.8HEND DATA)GO TO 20

200= READ(88,5) (X(I,N),Y(I,N),Z(I,N),I=1,2)
210= N=N+1

220= GO TO 30

230=20 CONTINUE

240= READ(88,6) (OPTIONS(I),I=1,5)

260= DIP=DIP/RADCONV

270= AZIMUTH=AZ IMUTH/RADCONV

275a N=N-1

280= D0 100 I=1,N

300= RHO=2(1,I)/TAN(DIP)

310= X(l,I)=COS(AZIMUTH)*RHO+X(1,1)

315= X(2,I)-COS(AZIMUTH)*RHO+X(2,I)

320= Y(1,I)=SIN(AZIMUTH)*RHO+Y(1,1)

325a Y(2,I)=SIN(AZIMUTH)*RHO+Y(2,I)

330=100 CONTINUE

340= WRITE(99,2) (EXTRA(I),I=1,3)

350a WRITE(99,3) IRow,ICOL,EXTRA(4)

360: D0 200 J=1,N

370= WRITE(99,4) (PROP(I,J),I=I,4)

73

380=200 WRITE(99,S) (X(I,J),Y(I,J),Z(I,J),I=1,2)
390I WRITE(99,10)

4OO= WRITE(99,6) (OPTIONS(I),I=1,5)
410a WRITE(99.7) TITLE

420=1 FORMAT(F4.0,F3.0)

430=2 FORMAT(3F5.1)

44O=3 FORMAT(212,F5.3)

450-4 FORMAT(10X,4F13.1)

460=5 FORMAT(6FS.2)

470=6 FORMAT(511)

480=7 FORMAT(8A10)

49O=15 FORMAT(A10,4F13.1)
500=10 FORMAT(8HEND DATA)

5103 STOP
520= END
LEVELONE

10= 1.0 84.00 46.5

20=20201.0

10008 100.0 296.0 322.8
1100=8.7508.750.050012.2512.25.5000

1110= 100.0 296.0 322.8
1200=9.2508.325.050011.758.750.5000

1210- 100.0 296.0 322.8
1300=12.259.250.050012.6211.75.5000

1310* 100.0 296.0 322.8
1400=9.25012.25.050011.7512.62.5000

1410= 100.0 296.0 322.8
1500=8.3259.250.05008.75011.75.5000

1510= 100.0 296.0 322.8
1600=10.008.000.050011.008.325.5000

1610= 100.0 296.0 322.8
l700=12.6310.00.050013.0011.00.5000

1710= 100.0 296.0 322.8
1800=10.0012.63.050011.0013.00.5000

18108 100.0 296.0 322.8
1900=8.00010.00.05008.32511.00.5000

2000= 100.0 296.0 322.8
2010=8.7508.750.500012.2512.251.000

20203' 100.0 296.0 322.8
2030=9.2508.325.500011.758.7501.000

2040= 100.0 296.0 322.8
2050=12.259.250.500012.6211.751.000

2060= 100.0 296.0 322.8
2070=9.25012.25.500011.7512.621.000

2080= 100.0 296.0 322.8

2090=8.3259.250.50008.75011.751.000
2100- 100.0 296.0 322.8

74

2110=10.008.000.500011.008.3251.000
2120= 100.0 296.0
2130=12.6310.00.500013.0011.001.000
2140= 100.0 296.0
2150810.0012.63.500011.0013.001.000
2160= 100.0 296.0
2170=8.00010.00.50008.32511.001.000
3000= 100.0 296.0
3010=8.7508.7501.00012.2512.251.500
3020= 100.0 296.0
3030=9.2508.3251.00011.758.7501.500
3040= 100.0 296.0
3050=12.259.2501.00012.6211.751.500
3060= 100.0 296.0
3070=9.25012.251.00011.7512.621.500
3080= 100.0 296.0
3090=8.3259.2501.0008.75011.751.500
3100= 100.0 296.0
3110=10.008.0001.00011.008.3251.500
3120= 100.0 296.0
3130=12.6310.001.00013.0011.001.500
3140= 100.0 296.0
3150=10.0012.63l.00011.0013.001.500
3160= 100.0 296.0
3170=8.00010.001.0008.32511.001.500
4000= 100.0 296.0
4010=8.7508.7501.50012.2512.252.000
4020= 100.0 296.0
4030=9.2508.3251.50011.758.7502.000
4040= 100.0 296.0
4050=12.259.2501.50012.6211.752.000
4060= 100.0 296.0
4070=9.25012.251.50011.7512.622.000
4080= 100.0 296.0
4090=8.3259.2501.5008.75011.752.000
4100= 100.0 296.0
4110=10.008.0001.50011.008.3252.000
4120= 100.0 296.0
4130=12.6310.001.50013.0011.002.000
4140= 100.0 296.0
4150=10.0012.631.50011.0013.002.000
4160= 100.0 296.0
4170=8.00010.001.5008.32511.002.000
5000= 100.0 296.0
5010=8.7508.7502.00012.2512.252.500
5020= 100.0 296.0
5030=9.2508.3252.00011.758.7502.500
50403 100.0 296.0
5050=12.259.2502.00012.6211.752.500
5060= 100.0 296.0
507089.25012.252.00011.7512.622.500
5080= 100.0 296.0
509088.3259.2502.0008.75011.752.500

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

322.8

8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4

8.4

7S

5100= 100.0 296.0
5110=10.008.0002.00011.008.3252.500
5120= 100.0 296.0
Sl30=12.6310.002.00013.0011.002.500
5140= 100.0 296.0
5150=10.0012.632.00011.0013.002.500
5160= 100.0 296.0

5170=8.00010.002.0008.32511.002.500
5200=END DATA

5210= 2

5220=SCOOPS MODEL.

322.8

322.8

322.8

322.8

8.4

8.4

8.4

8.4

APPENDIX E

Surface II Commands

76

77

Computer Model Contour Maps, Figures 14-17.

100=*JOBCARD*, CMIOOOOO, TSOO,RGZ,JC1500.
110=ATTACH,TAPE 10,WESSO,PW=MAG.

llS-ATTACH,TAPE 11,LEVEL1,PW=MAG.

117-REwIND,TAPE 11.

120=REWIND TAPE 10.

130=ATTACH,SURFACE,BNOVSURF.

140=3URPACE.

140,000001=*E0R00

160=IDXY 400,10,3,2,3,1,,,,,"(2x,P10,2,2x,P10.2,2x,P10.2)"
170=GRID 0,39,39,2,4,1,0
180=OCTANT l,l,1.4,1.8,4
190=CONT

195=LEVE 11,31,"(F7.1,1X,I1)"
200-CINT 2,,,,,.20,0,6,,
210=SIZC 1,11,11

220-BOX 1,0,1,0,1,o,0,1,0.20
230=DEVICE 4, ”PHILLIPS"
240=PERFORM

250=STOP

,11.25

Vertical Magnetic Intensity Contour Map (General Study Area), Figure 4

100=*JOBCARD*,CMIOOOOO,T500,RGl,JC3000.
110=ATTACH,TAPE 10,WESDATA3.

120=ATTACH,TAPE 11,WESDATA8.

130=REwIND TAPE 10,TAPE 11.

140=ATTACH,SURFACE,BNOVSURP.

150=SURFACE

160=*EOR

170=IDXY 573,10,4,2,3,4,,,,,'(A3,1X,F6.1,1X,F6.1,1X,F8.l)'
180=GRID 1,200,200,1,2,1,0

190=OCTANT 1,1,837,1800,4,11.25

200=CONT

210=LEVE 11,20,'(F7.1,1X,I1)'

220=CINT 2,,,,,0.075,0,4

230=SIZC 0,500,500

240=Box 600,2,600,2,0,0,0,2,0.1

250=BXEX

260=DEVICE 5,'PHILLIPS'

270=PERFORM

280=STOP

78

Vertical Magnetic Intensity Contour Map (Detailed Map), Figure 5.

100=*JOBCARD*,CM100000,TSOO,RGl,JC3000.
110=ATTACH,TAPE 10,wESDATA5.

120=REWIND TAPE 10.
130=ATTACH,SURFACE,BNOVSURF.
140=SURFACE.

150=*EOR

l60=IDXY 288,10,4,2,3,4,,,,,'(A3,1x,F6.1,1x,F6.1,1x,F8.1)'
170=GRID 1,25,25,1,2,1,0

180=OCTANT 1,1,700,1500,4,11.25
190=MLEVEL

200=CONT

210=CINT 0,0,100,0.1,0.05,0,4,5
220=SISC 0,500,500

230=BOX 600,2,500,2,0,2400,2400,2,0.1
240=BXEX

250=DEVICE 4,'PHILLIPS'

260=PERFORM

270=STOP

BIBLIOGRAPHY

79

BIBLIOGRAPHY

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