Oceanic crust and mantle evidence for the evolution of Tonian-Cryogenian ophiolites, southern Brasiliano Orogen

M.M. Werler, L. A. Hartmann, G.N. Queiroga, Cris Lana, J. Pertille, C.R.L Michelin, M.V.D. Remus, Malcolm Roberts, N.P Castro, C.G Leandro, J.F Savian

Research output: Contribution to journalArticle

Abstract

Unravelling the complexity of tonian-cryogenian (950–680 Ma) evolution of ophiolites requires the search for rare mineral systems and their quantification with varied techniques. Ophiolites in the Brasiliano Orogen are widely distributed over 2,000 km along the eastern half of South America. We selected two ophiolites from different geotectonic settings of the Sul-Riograndense Shield, southern Brasiliano Orogen, to delimit the evo-lution of the oceanic phase of the orogen. The southern portion of the Bossoroca ophiolite is inserted in the S ̃ao Gabriel juvenile terrane and contains rare metasomatic tourmaline in chloritite close to serpentinite and meta-morphosed Cr-spinel. The southern Bossoroca ophiolite was intruded by Cerro da Cria and Ramada Granites and the U-Pb-Hf isotopic study of zircon from these rocks constrains the crustal evolution of the S ̃ao Gabriel juvenile terrane. Capan ́e ophiolite has similar age (793–715 Ma) as the Bossoroca ophiolite and was inserted in the Porongos fold-thrust belt with preserved Cr-spinel of mantellic composition. Integrated use of Cr-spinel mineral chemistry, B isotopes in tourmaline in the Bossoroca ophiolite and zircon U-Pb-Hf isotopes of granites associated with the southern Bossoroca ophiolite revealed several steps in the evolution of the ophiolites in the Dom Feliciano Belt. Capan ́e Cr-spinel cores have mantle-derived compositions (Mg# 0.66 – 0.69; Cr# 0.51 – 0.53), tourmaline from the Bossoroca ophiolite is dravite and has δ11B =0 to +3, and granites crystallization ages are 578 ±3.2 and 612 ±12 Ma (εHfzrn =
Original languageEnglish
Article number105979
JournalPrecambrian Research
Volume351
DOIs
Publication statusPublished - 19 Oct 2020

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