The effects of quartz recrystallization and reaction on weak phase interconnection,strain localization and evolution of microstructure |
| |
| Institution: | 1. Departamento de Geologia, Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, s/n, Ouro Preto CEP: 35400-000, MG, Brazil;2. Department of Geological Sciences, Brown University, Providence, RI 02912, USA;1. Géosciences Environnement Toulouse (GET) – UMR 5563, Université de Toulouse, CNRS, IRD, OMP, 14 Avenue E. Belin, F-31400 Toulouse, France;2. Departament de Geologia, Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Barcelona, Spain;3. SGC, Volcanological and Seismological Observatory of Manizales, Avenida 12 de Octubre 15-47, Manizales, Colombia;1. Department for Geodynamics and Sedimentology, University of Vienna, Austria;2. Computational Geology Laboratory, Polish Geological Institute – National Research Institute, Wroc?aw, Poland;3. Physics of Geological Processes, University of Oslo, Norway;1. Department of Earth Sciences and Environmental and Resources Engineering, Graduate School of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8050, Japan;2. Department of Earth Sciences, Faculty of Education and Integrated Arts and Sciences, Waseda University, Shinjuku, Tokyo 169-8050, Japan;1. Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA;2. ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia;3. Department of Geological Sciences, University of Nevada, Reno, NV 89557, USA;4. Department of Earth Science, University of Bergen, 5007 Bergen, Norway;1. Departamento de Geología, Universidad de Salamanca, Pza. de los Caídos s/n, 37008 Salamanca, Spain;2. Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA;3. Los Alamos Neutron Science Center, Los Alamos National Laboratory, NM 87545, USA |
| |
| Abstract: | We conducted axial compression and general shear experiments, at T = 900 °C and P = 1.5 GPa, on samples of banded iron formation (BIF) and synthetic aggregates of quartz, hematite and magnetite to investigate how dynamic recrystallization of quartz promotes strain localization, and the role of weak second phases (oxides) on the rheology and microstructural evolution of the aggregates. Experiments showed strain localization into oxide rich layers, and that the oxide content and oxide distribution are key factors for the strength of the aggregate. Only 2–10 wt.% hematite leads to pronounced weakening and increasing hematite content above ～10% has only a minor additional effect. Where oxide grains are dispersed, the initial strength contrast with quartz induces stress concentrations at their tips, promoting high stress recrystallization-accommodated dislocation creep of quartz. Fine recrystallized quartz reacts with oxide, forming trails of fine reaction product (ferrosilite/fayalite) leading to the interconnection/percolation of a weaker matrix. The strength contrast between the quartz framework and these fine-grained trails promotes strain localization into micro-shear zones, inducing drastic strain weakening. Thus dynamic recrystallization of quartz promotes syn-deformational reactions leading to a microstructurally-controlled evolution of phase strength contrast. It results in a rheologic transition from load-bearing framework to a matrix-controlled rheology, with transition from S–C′ to S–C fabric with increasing strain. |
| |
| Keywords: | Quartz rich aggregates Load-bearing framework Matrix-controlled rheology Weak phase interconnection Experimental deformation Shear zone development |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
