|Figure 5-7. A: Marble in which two roughly parallel prominent N-S stylolites (black arrows) intersect and in some cases truncate a series of parallel less prominent E-W stylolites (red arrows). B, C, and D: Higher-magnification views of rectangles shown in A, showing less prominent stylolites. Projections or "teeth" along these stylolites (black arrows in B, C, and D) are not perpendicular to the stylolites and instead generally point in the same direction as the teeth of the prominent stylolites (black arrows in A).
One possible interpretation of these relationships is that the less prominent stylolites formed first as the result of N-S compression and were later deformed and in some cases truncated when the more prominent stylolites formed in SW-NE compression. (Another image in this atlas demonstrates that the orientation of early-formed stylolite teeth can be altered in later deformation.) A second possible interpretation is that both sets formed simultaneously in SW-NE compression, and that the overall trend of the less prominent set was dictated by some previous feature, such as an earlier set of E-W fractures.
Image was scanned directly from sample; orientation is unkown and so "N-S" etc. are only used in reference to these images. The sample is from the Fortitude gold skarn deposit, Lander County, Nevada, U.S.A. The sample was collected and kindly donated by Dr. Lawrence D. Meinert of Washington State University.
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