The Neoproterozoic Andrelandia group: Evolution from an intraplate continental margin to an early collisional basin south of the Sao francisco craton, Brazil

New U-Pb and Lu-Hf zircon data for the Andrelandia Group are presented and discussed with the previously published data to propose an evolutionary model. The Andrelandia Group consists of two depositional sequences that record the geotectonic evolution from Tonian to Ediacaran times. Both sequences are part of the Andrelandia Nappe System, a fold-and-thrust system, generated in the 630-600 Ma interval, during the evolution of the Neoproterozoic convergence in the interference zone between the Southern Brasilia and the Ribeira orogens, SE Brazil. The Andrelandia Group rocks record greenschist to granulite facies metamorphism related to this convergence. The lower sequence consists of paragneiss, metapelite, quartzite, metachert, calc-silicate and mafic rocks distributed in five lithofacies associations. They record shallow to deep water sedimentation coeval with mafic magmatism at the southern border of the Sao Francisco Craton. U-Pb data obtained from detrital zircon grains of deep water quartzites indicate a maximum depositional age of ca. 970 Ma. The U-Pb age peaks can be correlated to major events in the adjacent Sao Francisco paleocontinent. epsilon Hf-t isotopic signature obtained in this study shows a predominance of juvenile sources for the Mesoproterozoic and crustal reworking and juvenile additions for the Paleoproterozoic. This can be related to source rocks from the Espinhaco Supergroup and from the Mineiro Belt, respectively. We interpret our data together with previous published detrital zircon data and whole-rock epsilon Nd-t signatures to suggest that the lower sequence of the Andrelandia Group is related to a passive margin of the Sao Francisco paleocontinent with a platformal and a deep water succession with roughly similar sources, indicating likely a resedimentation process. The upper sequence of the Andrelandia Group consists of a monotonous package of biotite schist interpreted as metamorphosed plagioclase sandstones and siltstones. The upper sequence covers the lower sequence units unconformably. Deposition occurred in a relatively deep and fast subsiding basin during the early collisional stage of the southern Brasilia Orogen. Previously published U-Pb, Sm-Nd and Lu-Hf data for the upper sequence constrain likely sources in the southern Sao Francisco Craton and possibly in the early stages of the Neoproterozoic Socorro-Guaxupe arc, established at the eastern margin of the Paranapanema paleocontinent, which collided with the Sao Francisco paleocontinent during West Gondwana assembly.