Full text
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| Author(s): |
Lucas Rodrigues Schiavetti
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências |
| Defense date: | 2018-08-29 |
| Examining board members: |
Vinicius Tieppo Meira;
Brenda Chung da Rocha;
Mahyra Ferreira Tedeschi
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| Advisor: | Vinicius Tieppo Meira |
| Abstract | |
Orogenic belts characterized by high geothermal gradients at intermediate crustal levels are known as "hot orogens" and their evolution is generally associated with granulite facies metamorphism, widespread partial melting and crustal flow. In the last decade an innnovative approach, known as Petrochronology, brought new constraints to the understanding of complex geological terrains and polyphase orogens. This new approach uses detailed textural control coupled with multi-mineral/system geochronology and trace-element geochemistry to constrain P-T-t paths for metamorphic and igneous rocks. In this context, the Neoproterozoic Araçuaí Orogen (SE Brazil) represent the exposition of deeper crustal levels of a hot orogen that records long-lived magmatism, intense anatexis and high-T metamorphism, during the assembly of West Gondwana in the Ediacaran-Cambrian transition. Granulite facies migmatitic paragneisses from the Nova Venécia Complex, located near the city of Colatina, Espírito Santo state, constitute the hot internal domain of the orogen. Ediacaran peraluminous anatectic rocks (Ataleia Suite) exhibit transitional contact with the paragneisses, while a cambrian gabbro-norite pluton (São Gabriel Pluton) forms a diffusive contact with restricted metamorphic aureole within the paragneisses. The relationship between the paragneisses and the gabbro-norite pluton enables temporal and tectonic constraints on the influence of the regional and contact metamorphism to the Araçuaí Orogen evolution. Metamorphic estimates indicate temperatures between ca. 700 °C and 1000 °C, and pressures between 5.5 e 6.5 kbar for the studied samples. Lu-Hf garnet ages vary from ca. 570 to 530 Ma and suggest long-living high-grade conditions in the internal domain of the Araçuaí Orogen. Additionaly, LA-ICP-MS U-Pb zircon ages varying from 545 and 510 Ma also attest for high-grade conditions prevailing in the orogenic middle crust until later stages, which may also be related with the generation/intrusion of the mafic rock. The data suggest that the internal domain records the maintenance of high-T/medium-P conditions along tens of million years within a hot orogen context (AU) | |
| FAPESP's process: | 17/00325-8 - P-T-t PATHS, AND EXHUMATION AND COOLING RATES OF HOT OROGENS - THE CASE STUDY OF NOVA VENÉCIA COMPLEX, ARAÇUAÍ OROGEN |
| Grantee: | Lucas Rodrigues Schiavetti |
| Support Opportunities: | Scholarships in Brazil - Master |