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

Abstract

Apatite fission track thermochronology of basement rocks from the southern Espinhaço Range and QuadriláteroFerrífero in southeastern Brazil unravels the tectonic history of this portion of the Brazilian Shield. The studyarea encompasses an Archean and Paleoproterozoic granitoid-gneiss basement, in the southern border of the SãoFrancisco Craton, and an Archean to Paleo-Mesoproterozoic sedimentary cover. Apatitefission track ages (AFT)vary from 187 ± 18 to 91.8 ± 7.3 Ma and horizontal confined track lengths vary from 9.62 ± 1.81μmto12.85 ± 1.35μm. Thermal history modeling shows an accelerated cooling episode starting in the UpperDevonian to Early Permian. After this event, quiescence lasted from 115 to 170 Ma. Apatite samples lack evi-dence of far-field effects from rifting and opening of the South Atlantic Ocean, and also evidence from alkalineand basaltic magmatism emplacement during Mesozoic-Cenozoic. The AFT thermochronometer remained un-disturbed during Transminas mafic dyke swarm intrusion. Finally, the last cooling event in the Espinhaço Range-Quadrilátero Ferrífero basement records ascension to surface temperatures due to epeirogeny after new con-figurations of the Nazca, South American and African plates. A climatic origin for the ascension is supported byaccentuated erosion rates, even though a weathering-prone phase is registered in weathering profiles.