摘要
We document new U-Pb detrital zircon LA-MC-ICP-MS data for seven metavolcanic-sedimentary successions and metasedimentary sequences and reassess additional dates of five siliciclastic samples toward their tectonic significance in the context of the Mineiro belt,Southern São Francisco Craton.This belt represents a crustal segment of the 2.47–2.00 Ga Minas Orogen,classically known by its Siderian and Rhyacian juvenile rocks with important implications in the Earth’s geodynamics.The new and compiled detrital provenance constraints unravel the long-lived magmatic and sedimentary history of the studied basins,lasting ca.230–220 Myr.The maximum depositional dates around 2.1 Ga reflect the renewed sediment budget with the subsequent metamorphic episode ca.2.0 Ga.Most of the unmixed relative probability diagrams are consistent with sourcing from the Siderian and Rhyacian arcs of the Mineiro belt,determining a detrital provenance change in time and space for the precursor basins.Alternative potential sources could be the youngest rocks of the Mantiqueira and Juiz de Fora terranes that constitute the other segments of the Minas Orogen,given the age match.The overall detrital fingerprints determine the study basins resumed mainly in Rhyacian fore-arc and/or back-arc settings,i.e.,akin to a subductionrelated system that evolved to a collisional(foreland)environment.Few samples show fingerprints of primary extensional settings,determined by major Archean detrital populations sourced from areas outside the Mineiro belt beside the Paleoproterozoic detritus.The working model considers the collage between the Mineiro belt and the ancient foreland around 2.10 Ga and eventual interaction with other crustal segments of the Minas Orogen,generating the ca.2.0 Ga metamorphism over the metasedimentary samples.The more complete isotopic repository in detrital and igneous zircon grains for the studied supracrustal successions and the associated rocks allows new insights into the Rhyacian–Orosirian dynamics of the Minas orogeny.In a broader perspective,the juvenile nature of the Mineiro belt reinforces the paradigm of uninterrupted continental growth during the Paleoproterozoic Earth.
基金
support of the Geochronological Research Center(CPGeo)of the University of São Paulo,Brazil
the São Paulo State Research Foundation–FAPESP(2004/15295-7 and 2009/53818-5)
the National Council of Technological and Scientific Development–CNPq(5092018/Edital Universal)provided partial funding of the research
the Rio de Janeiro State Research Foundation(FAPERJ)for financial support。
