Temperature constraints on microfabric patterns in quartzofeldsphatic mylonites, Ribeira belt (SE Brazil)

Autor(es)

Cavalcante, Carolina ^[1] ; Lagoeiro, Leonardo ^[1] ; Fossen, Haakon ^{[1, 2]} ; Egydio-Silva, Marcos ^[3] ; Morales, Luiz F. G. ^[4] ; Ferreira, Filippe ^[5] ; Conte, Thailli ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Parana, Dept Geol, Ave Cel Francisco Heraclito dos Santos 100, BR-81531980 Curitiba, Parana - Brazil

^[2] Univ Bergen, Museum Nat Hist, Dept Earth Sci, Allegaten 41, N-5007 Bergen - Norway

^[3] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil

^[4] Swiss Fed Inst Technol, Sci Ctr Opt & Electron Microscopy, Auguste Piccard Hof 1, CH-8093 Zurich - Switzerland

^[5] Univ Bayreuth, Bayer Geoinst BGI, Univ Str 30, D-95947 Bayreuth - Germany

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF STRUCTURAL GEOLOGY; v. 115, p. 243-262, OCT 2018.
• Citações Web of Science: 4

Resumo

Based on samples from the major high-temperature Tres Rios-Alem Parafba-Padua transpressive shear zone in the Ribeira orogenic belt, Brazil, we discuss the applicability of TitaniQ geothermometry to constrain peak temperature conditions during high-temperature mylonitization of quartzofeldspatic rocks, and explore the microfabrics formed at these conditions. We discuss various aspects of the TitaniQ method and conclude that deformation occurred at temperatures ranging from 612 to 740 +/- 20 degrees C in the studied segment of the shear zone. This high-temperature deformation resulted in relatively large grain size, quartz ribbons and abundant intracrystalline deformation. However, the CPO fabrics are weak, and microstructures suggest that quartz deformation was accommodated by dynamic recrystallization involving grain boundary migration with subsequent grain growth, and later some subgrain rotation during exhumation. We relate the weak fabrics to diffusion processes during or immediately after dynamic recrystallization and dislocation creep, and to the effect of competing slip systems during deformation. In terms of rheology, evidence for Dauphine twinning in our samples suggest strain softening during mylonitization, and we suggest that such twinning may add to the rheologically weak nature of quartzo-feldspatic portions of hot middle to lower crust. (AU)

• Processo FAPESP: 13/19061-0 - Evolução reológica da crosta continental: microestruturas e mecanismos de deformação na zona de cisalhamento Além Paraíba-Pádua (Faixa Araçuaí-Ribeira)
• Beneficiário: Geane Carolina Gonçalves Cavalcante
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 14/10146-5 - Evolução reológica da crosta continental: microestruturas e mecanismos de deformação na zona de cisalhamento além Paraíba-Pádua (Faixa Ribeira)
• Beneficiário: Geane Carolina Gonçalves Cavalcante
• Linha de fomento: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado