Dating recurrent shear zone activity and the transition from ductile to brittle deformation: White mica geochronology applied to the Neoproterozoic Dom Feliciano Belt in South Brazil

Autor(es)

Hueck, Mathias ^{[1, 2]} ; Wemmer, Klaus ^[2] ; Basei, Miguel A. S. ^[1] ; Philipp, Ruy P. ^[3] ; Oriolo, Sebastian ^[4] ; Heidelbach, Florian ^[5] ; Oyhantcabal, Pedro ^[6] ; Siegesmund, Siegfried ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

^[2] Georg August Univ Gottingen, Geosci Ctr, Gottingen - Germany

^[3] Univ Fed Rio Grande do Sul, Inst Geociencias, Porto Alegre, RS - Brazil

^[4] Univ Buenos Aires, CONICET, Inst Geociencias Basicas Aplicadas & Ambientales, Buenos Aires, DF - Argentina

^[5] Univ Bayreuth, Bayer Geoinst, Bayreuth - Germany

^[6] Univ Republica, Inst Ciencias Geol, Montevideo - Uruguay

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF STRUCTURAL GEOLOGY; v. 141, DEC 2020.
• Citações Web of Science: 0

Resumo

Argon geochronology of white mica has a good potential of recording recurrent dynamic recrystallization in shear zones in the transition from ductile to brittle deformation, as temperature ranges for mineral crystallization and isotopic closure of different grain-size fractions overlap between ca. 275-425 degrees C. This study presents over 40 K-Ar ages of coarse-grained muscovite and multiple clay-sized white mica fractions extracted from mylonites and fault gouges in southernmost Brazil, complemented by detailed structural and XRD characterization. The widespread obtained ages are best explained in the context of recurrent deformation under retrograde conditions during progressive strain localization and transition from low-grade ductile deformation into brittle faulting. The onset of the Ibare Shear Zone is constrained in the Tonian, followed by reactivation during the Ediacaran evolution of the adjacent Dom Feliciano Belt, which records a remarkable long-term history of recurrent deformation for over 100 Myr. New data extends the geochronological constraints of the Dorsal do Cangucu Shear Zone into low-temperature conditions, estimating the onset of brittle activity at 525-470 Ma by dating early fault gouges formed shortly after final syn-kinematic white mica crystallization in the hosting mylonites. Dating of recurrent faulting events during the Paleo-Mesozoic complement the regional sedimentary and thermochronological record. (AU)

• Processo FAPESP: 15/03737-0 - O Cráton Rio de la Plata e o Gondwana Ocidental
• Beneficiário: Miguel Angelo Stipp Basei
• Modalidade de apoio: Auxílio à Pesquisa - Temático