气候变化领域集成服务门户(CCPortal): Microscopic anatomy of a "hot-on-cold" shear zone: Insights from quartzites of the Main Central Thrust in the Alaknanda region (Garhwal Himalaya)

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DOI	10.1130/B31797.1
	Microscopic anatomy of a "hot-on-cold" shear zone: Insights from quartzites of the Main Central Thrust in the Alaknanda region (Garhwal Himalaya)
	Hunter N.J.R.; Weinberg R.F.; Wilson C.J.L.; Luzin V.; Misra S.
发表日期	2018
ISSN	167606
起始页码	1519
结束页码	1539
卷号	130 期号:2021-09-10
英文摘要	Microstructures inside exhumed crustal shear zones provide a window into the mechanics of Earth's interior. However, difficulties remain in quantifying their physical properties due to the numerous macro-, meso-, and grain-scale factors controlling their development and modification. The complex interplay between these factors has meant that inconsistencies remain between the knowledge derived from controlled laboratory deformation experiments and that from empirical observations in nature. We present a quantitative toolbox for identifying variations in the deformation characteristics of shear zones, using the microstructure and crystallographic preferred orientation (CPO) of quartz. The Main Central Thrust in the Alaknanda Valley (NW Himalaya) is an archetypal major ductile thrust zone that contains abundant quartzites and quartz-mica schists that permit microstructural characterization across gradients in strain and temperature. Using a combination of detailed microstructural analysis and neutron diffraction, we show that quartzites across the Main Central Thrust sequence are characterized by: (1) systematic increases in grain lobateness and coarseness, indicating the transition from subgrain rotation (SGR) to dominant grain boundary migration (GBM) dynamic recrystallization; (2) a concomitant shift in CPO from oblique (top-to-the-SSW) girdles to a strong single y maximum, indicating increasing activity of prismatic slip; and (3) high CPO intensities coinciding with the switch to GBM and prismatic slip activity. Our analyses suggest the Main Central Thrust may be characterized as an ~3-km-wide zone of dominantly non-coaxial deformation coinciding with a sharp change in peak metamorphic temperatures, from ~450 °C in the footwall to 750-800 °C in the hanging wall. We suggest that the observed systematic microstructural and CPO transitions may typify the deformational behavior of quartz in the Main Central Thrust across the wider Himalaya. © 2018 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/185096
作者单位	School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia; Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234, Australia; Department of Earth Sciences, Indian Institute of Technology Kanpur, Uttar Pradesh, 208016, India
推荐引用方式 GB/T 7714	Hunter N.J.R.,Weinberg R.F.,Wilson C.J.L.,et al. Microscopic anatomy of a "hot-on-cold" shear zone: Insights from quartzites of the Main Central Thrust in the Alaknanda region (Garhwal Himalaya)[J],2018,130(2021-09-10).
APA	Hunter N.J.R.,Weinberg R.F.,Wilson C.J.L.,Luzin V.,&Misra S..(2018).Microscopic anatomy of a "hot-on-cold" shear zone: Insights from quartzites of the Main Central Thrust in the Alaknanda region (Garhwal Himalaya).Bulletin of the Geological Society of America,130(2021-09-10).
MLA	Hunter N.J.R.,et al."Microscopic anatomy of a "hot-on-cold" shear zone: Insights from quartzites of the Main Central Thrust in the Alaknanda region (Garhwal Himalaya)".Bulletin of the Geological Society of America 130.2021-09-10(2018).