Strain partitioning in the mid-crust of a transpressional shear zone system: Insights from the Homestake and Slide Lake shear zones, central Colorado

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• 作者：P. Elizabeth Lee^a ; ¹ ; ^{liz.lee@exxonmobil.com} ; Micah J. Jessup^a ; Colin A. Shaw^b ; Gordon L. Hicks III^a ; Joseph L. Allen^c
• 关键词：Transpression ; Proterozoic ; Low-angle shear zones ; Microstructures ; Quartz fabrics
• 刊名：Journal of Structural Geology
• 出版年：2012
• 期刊代码：52_01918141
• 类别：ear
• 出版时间：June, 2012
• 卷：39
• 期：Complete
• 页码：237-252
• 文件大小：5281 K

摘要

Kinematic analysis and field mapping of the Homestake shear zone (HSZ) and Slide Lake shear zone (SLSZ) in central Colorado may provide insight into the interaction between subvertical and low-angle shear zones in the middle crust. The northeast-striking, steeply dipping HSZ comprises a 鈭?0-km-wide set of anastomosing ductile shear zones and pseudotachylyte-bearing faults. Approximately 4聽km south of the HSZ, north-northeast-striking, shallowly dipping mylonites of the SLSZ form three 1-10-m-thick splays. Oblique stretching lineations and shear sense in both shear zones record components of dip-slip (top-up-to-the-northwest and top-down-to-the-southeast) and dextral strike-slip movement during mylonite development. Quartz and feldspar deformation mechanisms and quartz [c] axis lattice preferred orientation (LPO) patterns suggest deformation temperatures ranging from 鈭?80-500聽掳C in the HSZ to 鈭?80-600聽掳C in the SLSZ. Quartz [c] axis LPOs suggest plane strain general shear across the shear system. Based on the relative timing of fabric development, compatible kinematics and similar deformation temperatures in the SLSZ and the HSZ, we propose that both shear zones formed during strain localization and partitioning within a transpressional shear zone system that involved subvertical shuffling in the mid-crust at 1.4聽Ga.