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Title: The effects of quartz recrystallization and reaction on weak phase interconnection, strain localization and evolution of microstructure.
Authors: Gonçalves, Cristiane Paula de Castro
Gonçalves, Leonardo Eustáquio da Silva
Hirth, Greg
Keywords: Quartz rich aggregates
Weak phase interconnection
Experimental deformation
Shear zone development
Issue Date: 2015
Citation: GONÇALVES, C. P. de C.; GONÇALVES, L.; HIRTH, G. The effects of quartz recrystallization and reaction on weak phase interconnection, strain localization and evolution of microstructure. Journal of Structural Geology, v. 71, p. 24-40, 2015. Disponível em: <>. Acesso em: 01 set. 2015.
Abstract: We conducted axial compression and general shear experiments, at T ¼ 900 _C and P ¼ 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 2e10 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 finegrained 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 SeC0 to SeC fabric with increasing strain.
ISSN: 0191-8141
metadata.dc.rights.license: O periódico Journal of Structural Geology concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 3701420779373.
Appears in Collections:DEGEO - Artigos publicados em periódicos

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