Metamorphic and geochronological constraints on the final assembly of West Gondwana: an Ediacaran-Cambrian collisional setting in the northern Araguaia Orogen, central Brazil

Metamorphic and geochronological constraints on the final assembly of West Gondwana: an Ediacaran-Cambrian collisional setting in the northern Araguaia Orogen, central Brazil

The Araguaia Orogen, located in Central Brazil, represents an Ediacaran-Cambrian collisional orogen associated with the final assembly of West Gondwana. Two contrasting tectonic models have been proposed for the evolution of this orogen, involving different histories for the Amazonian palaeocontinen...

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Bibliographic Details
Published in:International geology review Vol. 66; no. 1; pp. 31 - 53
Main Authors: de Freitas, Gabriela Bueno Fagundes, Meira, Vinícius Tieppo, Cioffi, Caue Rodrigues, Rocha, Brenda Chung, Luvizotto, George Luiz, Vervoort, Jeffrey, da Trindade, Ricardo Ivan Ferreira
Format: Journal Article
Language:English
Published: Philadelphia Taylor & Francis 02-01-2024
Taylor & Francis Ltd
Subjects:
Amazonian craton
Amphibolites
Assembly
Cambrian
Clymene ocean
Constraints
Cratons
Evolution
Garnet
Garnets
Geochronology
Gondwana
Hafnium
Lu-Hf garnet geochronology
Lutetium
Metamorphism
Orogeny
Phase diagrams
Schists
Subduction
Subduction (geology)
Tectonics
Thermodynamic models
Brazil
Gondwana
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Summary:The Araguaia Orogen, located in Central Brazil, represents an Ediacaran-Cambrian collisional orogen associated with the final assembly of West Gondwana. Two contrasting tectonic models have been proposed for the evolution of this orogen, involving different histories for the Amazonian palaeocontinent drift: (i) subduction of a large ocean and final collision of the Amazonian palaeocontinent with Gondwana between ~ 560 and 500 Ma and (ii) intracontinental orogeny after early amalgamation of the Amazonian palaeocontinent at ca. 620 Ma. Detailed tectono-metamorphic studies in this key locality for the evolution of Gondwana are also still scarce. Hence, in this study we present a detailed metamorphic investigation of two metapelite samples (schists) and one garnet amphibolite aiming to unravel the pressure-temperature-time (P-T-t) paths for the higher grade rocks exposed in this orogen. Pressure-temperature estimates based on thermodynamic modelling using isochemical phase diagrams in the MnNCKFMASHTO system for the schists constrained a single and continuous prograde metamorphic path (burial and heating) from ~ 4-6 kbar and ~ 450-500°C to ~ 7-8 kbar and ~ 580-650°C. The near-peak metamorphic conditions of the garnet amphibolite were estimated from classic geothermobarometry at 7.5 ± 0.8 kbar and 552 ± 40°C. Lutetium-hafnium garnet dating constrained an average age for the prograde metamorphism at around 537-533 Ma. These results show that the Araguaia Orogen records one single metamorphic event during the late Ediacaran-early Cambrian, and likely represents part of a collisional system developed between the Amazonian Craton and Parnaíba Block after the closure of the Clymene Ocean.
ISSN:0020-6814
1938-2839
DOI:10.1080/00206814.2023.2262695