Figure 1: Map of Southern Appalachians showing the Brevard Fault Zone and the Rosman field area in r

1
Figure 1 Map of Southern Appalachians showing
the Brevard Fault Zone and the Rosman field area
in relation to other regional tectonic features.
Modified from Hatcher (1975).
2
Figure 2 Schematic geologic Map of study area.
All sample locations are numbered. Those
included in the final filtered data set are shown
as black filled circles. White filled circles
are data points that are removed from the
filtered data set for compositional reasons.
3
Figure 3 Field photos from study area in Rosman,
North Carolina showing grain size increase with
distance from shear zone on the outcrop scale.
Finest grained rocks closest to the shear zone
(top left), and coarsest grained rocks furthest
from the shear zone (bottom center).
4
Figure 4 Photomicrographs showing grain size
increase with distance from shear zone on the
microscopic scale, all in crossed polarized
light, with sample name and distance from shear
zone noted.
5
b)
a)
Figure 5 Equal area stereonets showing foliation
(black circles) and lineation (black stars)
orientations. a) Foliation and lineations for
samples within 2200m of Brevard shear zone. b)
Foliations for samples more than 2200m from
Brevard shear zone.
6
Table 3 Summary of Ferromagnetic Composition
Analyses
Group designations are explained in the text
and caption for Figure 9
7
Table 2 Point Count Percentage Mineralogical
Composition for Selected Samples
8
a) BZ-23
Quartz
Mica
Mica
Plagioclase
Chlorite
Chlorite
b) BZ-07
Quartz
Microcline
Plagioclase
Mica
Figure 6 Sample XRD peak patterns, with
corresponding mineral label, for the two bulk
compositional classes in the Brevard Zone. a)
Composition characteristic of sites inside the
shear zone. b) Composition characteristic for
sites outside the shear zone
9
a)
b)
Figure 7 Normalized isothermal remanent
magnetization (IRM) acquisition curves for twenty
samples in the Brevard zone. a) These samples
saturate at low-field showing the presence of a
low coercivity mineral, likely magnetite because
they reach saturation before 500mT. b) These
samples reach saturation at a higher applied
field showing a higher coercivity mineral
possibly hematite. The curve marked with a dotted
line does not reach saturation before 3000 mT and
changes slope two times showing the presence of
two different ferromagnetic minerals one with a
low coercivity of about 200 mT, likely magnetite,
and one high coercivity mineral, likely hematite.
10
a)
b)
c)
Figure 8 Representative 3-axis IRM
demagnetization curves for samples from the
Brevard zone. a) Sample BZ-06 shows the complete
demagnetization of all coercivity populations by
320oC is indicative of pyrrhotite with a range of
coercivities. b) In sample BZ-15, the smooth
decay of the soft coercivity population to total
demagnetization at 580oC (the Curie Temperature)
shows the presence of magnetite. c) Sample BZ-34
shows the smooth decay of the soft coercivity
population to demagnetization at 580oC, again
indicative of magnetite. The demagnetization of
the medium and hard coercivity populations at
680oC (the Neel Temperature) shows that this
sample also contains hematite.
11
b)
a)
c)
d)
e)
Figure 9 Normalized susceptibility versus
temperature curves (-200 to 730 oC ) for each
compositional group. Arrows show heating and
cooling high temperature curves. High temperature
measurements were made in Argon gas. a) For
sample BZ-36 magnetic susceptibility increases at
-150oC showing a strong Verwey transition
indicative of pure multiple domain magnetite. The
Tc at 580o and 680oC are diagnostic of magnetite
and hematite respectively. There is a Hopkins
peak present, suggesting single domain magnetite.
b) Sample BZ-27 contains magnetite (no Verwey
transition, but Hopkins peak and decrease at
Curie Temperature of 580oC are present). Increase
in susceptibility at 320oC is indicative of
pyrrhotite. c) Sample BZ-06 contains only
pyrrhotite. d) Sample BZ-24 has a Hopkins peak
and susceptibility decrease at 580oC, but lack of
Verwey transition indicates that only small
amount present. e) Sample BZ-01 contains
pyrrhotite, magnetite, and hematite.
12
Table 1 XRD Analysis Results of Bulk Mineral
Composition
Analysis was done using the Jade 3.1 computer
program
13
Figure 10 Histogram showing bulk susceptibility
values for both groups of all sites as well as
the sites selected based on compositional and
deformation history similarities.
14
b)
a)
Figure 11 Sample stereonet plotted AMS ellipsoid
data and bootstrap confidence analysis for sample
BZ-13. a) Orientation of the 3 principle AMS
susceptibility ellipsoid axes ( -maximum axis,
- intermediate axis, and - minimum
axis). b) Bootstrap confidence analysis of AMS
ellipsoid for sample BZ-13.
15
Prolate
Oblate
Figure 12 Flinn diagram showing shape of the AMS
ellipsoid for all sites.
16
Prolate
Oblate
Figure 13 Flinn diagram showing shape of the AMS
ellipsoid for sites in the filtered data set.
17
Figure 14 Average corrected degree of anisotropy
for the AMS ellipsoid for every site as a
function of distance from the shear zone.
18
Figure 15 Average corrected degree of anisotropy
for the AMS ellipsoid for sites selected based on
compositional and deformation history
similarities as a function of distance from the
shear zone. Arrows show anisotropy trend. (Note
axial scales different from Figure 14)
19
Table 4 Sample Numbers and Distance from the
Shear Zone for all Sites in the Filtered Data Set
Distance across the shear zone is 880m.