Estimativas de tensão diferencial durante milonitização ao longo da zona de cisalhamento Pernambuco Leste (Província Borborema, nordeste do Brasil)

Autores

DOI:

https://doi.org/10.22456/1807-9806.108834

Palavras-chave:

Microestruturas, Mecanismos de Deformação, Zona de Cisalhamento, Província Borborema, Recristalização Dinâmica, Metamorfismo

Resumo

As condições de tensão diferencial ao longo da zona de cisalhamento Pernambuco Leste (ZCPE) foram avaliadas com base na relação piezométrica entre tamanho de grão recristalizado (d) e grau de recristalização dinâmica de agregados recristalizados de quartzo. As bandas miloníticas ricas em quartzo ocorrem tanto no domínio Caruaru quanto no Gravatá, individualizados ao longo da extensão lateral da ZCPE. O domínio Caruaru é constituído por milonitos grossos compostos por agregados recristalizados de quartzo (~50 µm) imersos em uma matriz fina de feldspato recristalizado. No domínio Gravatá, há a presença de ultramilonitos com bandas recristalizadas descontínuas ricas em quartzo (~47 µm) intercaladas com bandas máficas. As estimativas de tensão diferencial calculadas por piezometria em seis amostras de ambos os domínios são de: i) 30 MPa (d = 50 μm), 48 MPa (d = 27 μm) e 18 MPa (d = 94 μm) para os milonitos do domínio Caruaru, e ii) 20 MPa (d = 82 μm), 35 MPa (d = 40 μm) e 45 MPa (d = 30 μm) no domínio Gravatá. Os incrementos observados nos valores calculados de tensão diferencial estão associados a partição heterogênea da deformação entre os processos de recristalização dinâmica e mecanismos de fragmentação mecânica e/ou dissolução-precipitação, observados em grãos de quartzo e feldspato, respectivamente. A combinação dos processos rúpteis e dúcteis refletem o caráter reológico transicional da zona de cisalhamento Pernambuco típico de estruturas exumadas em níveis crustais intermediários a rasos.

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Publicado

2021-09-30

Como Citar

Silva, R. F., & Viegas, G. (2021). Estimativas de tensão diferencial durante milonitização ao longo da zona de cisalhamento Pernambuco Leste (Província Borborema, nordeste do Brasil). Pesquisas Em Geociências, 48(3). https://doi.org/10.22456/1807-9806.108834