Phanerozoic cooling history of Archean/Paleoproterozoic basement in the southern Espinhaco Range, southeastern Brazil, through apatite fission-track analysis

Apatite fission track thermochronology of basement rocks from the southern Espinhaco Range and Quadrilatero Ferrifero in southeastern Brazil unravels the tectonic history of this portion of the Brazilian Shield. The study area encompasses an Archean and Paleoproterozoic granitoid-gneiss basement, in the southern border of the Sao Francisco Craton, and an Archean to Paleo-Mesoproterozoic sedimentary cover. Apatite fission track ages (AFT) vary from 187 +/- 18 to 91.8 +/- 7.3 Ma and horizontal confined track lengths vary from 9.62 +/- 1.81 mu m to 12.85 +/- 1.35 mu m. Thermal history modeling shows an accelerated cooling episode starting in the Upper Devonian to Early Permian. After this event, quiescence lasted from 115 to 170 Ma. Apatite samples lack evidence of far-field effects from rifting and opening of the South Atlantic Ocean, and also evidence from alkaline and basaltic magmatism emplacement during Mesozoic-Cenozoic. The AFT thermochronometer remained undisturbed during Transminas mafic dyke swarm intrusion. Finally, the last cooling event in the Espinhaco Range-Quadrilatero Ferrifero basement records ascension to surface temperatures due to epeirogeny after new configurations of the Nazca, South American and African plates. A climatic origin for the ascension is supported by accentuated erosion rates, even though a weathering-prone phase is registered in weathering profiles.