Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Aracuaui belt, eastern Brazil

Autor(es)

Cavalcante, G. C. G. ^{[1, 2, 3]} ; Vauchez, A. ^{[2, 3]} ; Merlet, C. ^{[2, 3]} ; Egydio-Silva, M. ^[1] ; Bezerra de Holanda, M. H. ^[1] ; Boyer, B. ^{[2, 3]}

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[2] CNRS, F-34095 Montpellier 05 - France

^[3] Univ Montpellier 2, F-34095 Montpellier 05 - France

• Tipo de documento: Artigo Científico
• Fonte: SOLID EARTH; v. 5, n. 2, p. 1223-1242, 2014.
• Citações Web of Science: 6

Resumo

During the Neoproterozoic orogeny, the middle crust of the Aracuai belt underwent widespread partial melting. At the regional scale, this anatectic domain is characterized by a progressive rotation of the flow direction from south to north, suggesting a 3-D deformation of the anatectic middle crust. To better determine whether melt volumes present in the anatectic middle crust of the Aracuai orogen were large enough to allow a combination of gravity-driven and convergence-driven deformation, we used the titaniumin-quartz (TitaniQ) geothermometer to estimate the crystallization temperatures of quartz grains in the anatectic rocks. When possible, we compared these estimates with thermobarometric estimates from traditional exchange geothermobarometers applied to neighboring migmatitic kinzigites. TitaniQ temperatures range from 750 to 900 degrees C, suggesting that quartz starts crystallizing at minimum temperatures of >= 800 degrees C. These results, combined with the bulk-rock chemical composition of diatexites, allows the estimation of a minimum of similar to 30% melt and a corresponding viscosity of similar to 10(9)-10(10) Pas. Such a minimum melt content and low viscosity are in agreement with interconnected melt networks observed in the field. Considering that these characteristics are homogeneous over a wide area, this supports the finding that the strength of the middle crust was severely weakened by extensive partial melting, making it prone to gravity-driven flow and lateral extrusion. (AU)

• Processo FAPESP: 10/03537-7 - Estudo sismo-tectônico do leucogranito carlos chagas e unidades adjacentes na faixa araçuaí (leste do brasil).
• Beneficiário: Geane Carolina Gonçalves Cavalcante
• Modalidade de apoio: Bolsas no Brasil - Doutorado