Correlation of Finite Strain from Both Reduction Bodies and Preferred Orientation of Mica in Slate from Wales

Abstract

Research Article| May 01, 1975 Correlation of Finite Strain from Both Reduction Bodies and Preferred Orientation of Mica in Slate from Wales TERRY E. TULLIS; TERRY E. TULLIS 1Department of Geology and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 900243Present address: Department of Geological Sciences, Brown University, Providence, Rhode Island 02912. Search for other works by this author on: GSW Google Scholar DENNIS S. WOOD DENNIS S. WOOD 2Department of Geology, University of Illinois, Urbana, Illinois 61801 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1975) 86 (5): 632–638. https://doi.org/10.1130/0016-7606(1975)86<632:COFSFB>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation TERRY E. TULLIS, DENNIS S. WOOD; Correlation of Finite Strain from Both Reduction Bodies and Preferred Orientation of Mica in Slate from Wales. GSA Bulletin 1975;; 86 (5): 632–638. doi: https://doi.org/10.1130/0016-7606(1975)86<632:COFSFB>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Finite strain measurements obtained from formerly spherical natural strain indicators in slate are compared to the degree of preferred orientation of mica, as revealed by x-ray pole figure goniometry. The pole figures obtained for (002) are all elongated point maxima normal to the slaty cleavage; the short axes of these elongate maxima trend toward the direction of the linear "grain" in the plane of cleavage. The deformation ellipsoid has its shortest axis precisely perpendicular to the cleavage and its longest axis parallel to the linear grain in the cleavage. The geometric relations are consistent with the model proposed by March (1932) that assumes passive rotation of tabular markers and thereby allows strains to be predicted from observed preferred orientations and vice versa. The measured deformation ellipsoids reveal a compressional strain across the plane of cleavage of 63 percent, 66 percent, and 68 percent. The corresponding concentrations of poles to (002) predicted by the March model from these strains are 20.6, 25.6, and 31.6 times uniform, respectively, whereas pole concentrations of 16.3, 17.9, and 18.3 times uniform were actually measured. Hence the measured strains are more than adequate to account for the formation of the observed preferred orientations by a mechanism of rotation. This and other studies suggest that quantitative preferred orientation studies may enable both the magnitudes and directions of the principal finite strains to be estimated in deformed micaceous rocks that do not contain independent indicators of strain. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.