| Full text | |
| Author(s): |
Westin, Alice
;
Tedeschi, Mahyra
;
Campos Neto, Mario C.
;
Luvizotto, George L.
;
Motta, Rafael G.
;
Nobre, Augusto G.
;
Ando, Romulo A.
Total Authors: 7
|
| Document type: | Journal article |
| Source: | LITHOS; v. 490-491, p. 22-pg., 2024-12-15. |
| Abstract | |
In this contribution, we employed a petrochronological approach to investigate the tectonometamorphic evolution of Al-rich garnet-staurolite and garnet-staurolite-kyanite (biotite- and plagioclase-free) metapelites of the southernmost portion of the Neoproterozoic Brasilia orogen. We have reconstructed the first prograde to peak pressure-temperature-time (P-T-t) paths reported for metamorphic units of the area, by combining petrographic analyses, quantitative compositional mapping of major elements, phase equilibrium modeling, and EPMA Th-U-Pb monazite chemical dating. The metamorphic reactions involved in the prograde metamorphic evolution are discussed, including the effects of garnet fractionation, exhaustion of reactants, and re-equilibration reactions on the major-element composition of garnet porphyroblasts, and their influence on P-T condition estimates. Raman spectroscopy on carbonaceous material (RSCM) thermometry provided insights into the synkinematic retrograde path. A steep prograde path marked by two stages is recorded by the garnet porphyroblasts of garnet-staurolite-muscovite (+/- kyanite) schists: (i) 555-585 degrees C and 0.60-0.90 GPa; (ii) 590-635 degrees C and 1.0-1.4 GPa. Monazite crystals record the prograde to peak path from ca. 630-625 Ma to ca. 605-595 Ma. Matrix graphite crystals suggest post-peak cooling to 400-500 degrees C concurrent with the late stages of development of the main foliation. The reconstructed P-T-t paths indicate an intermediate dT/dP metamorphism, and a burial rate of similar to 0.55 km/Ma, with garnet compositional zoning suggesting that the high-pressure P-T-t path resulted from a single metamorphic event. The corresponding geothermal gradients, and in-situ ages, combined with regional evidence, suggest that peak metamorphic conditions were attained during collisional underthrusting of the continental crust related to the West Gondwana amalgamation. (AU) | |
| FAPESP's process: | 16/06952-1 - Thermochronology applied to geotectonic modeling: the case of the Southern Brasília orogen, Brazil |
| Grantee: | Alice Westin Teixeira |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |
| FAPESP's process: | 15/03737-0 - The Rio de La Plata Craton and the Western Gondwana Assembly |
| Grantee: | Miguel Angelo Stipp Basei |
| Support Opportunities: | Research Projects - Thematic Grants |