Paleovolcanology, geochemistry, and zircon U-Pb-Hf isotopes of the volcano-sedimentary sequences from the Ediacaran Campo Alegre-Corupa Basin, southern Brazil: Linking volcanism and tectonics during Western Gondwana consolidation

The Campo Alegre-Corupa Basin (CACB) records a well-documented sequence of volcano-sedimentary episodes associated with specific periods of crustal extension during the late-convergent to post-collisional tectonic stages of the consolidation of Western Gondwana. Two main volcano-sedimentary stages were detailed through stratigraphic and lithofaciological studies, combined with whole-rock geo-chemistry and zircon U-Pb-Hf analysis, resulting in a more complete understanding of the tectono-magmatic cycles and volcanological evolution of the CACB. During the Basin Stage (605-590 Ma), regional collisional tectonics was responsible for initiating the basin as a syn-orogenic rift, during which the sed-imentary cycle progressed from alluvial fans at the northern limit of the basin to braided rivers and into a lake to the south. U-Pb geochronology and Lu-Hf isotope signatures of detrital zircon revealed that the sediments were mainly derived from the Paleoproterozoic basement of the Luis Alves Terrane, which constitutes the direct basement of the CACB, with contributions from the nearby Pien Magmatic Arc and possibly from the Curitiba Terrane to the North. The sedimentary strata were progressively covered by transitional to mildly alkaline OIB-like basalts, occurring mostly as lava flows with structural aspects suggestive of subaqueous to subaerial environments, interbedded with trachydacites and surge-like pyroclastic deposits. Large volumes of widespread and densely-welded to rheomorphic ignimbrite sheets within the CACB attest to a second infilling period corresponding to the Caldera Stage (583-577 Ma). This stage was inaugurated by the outpouring of trachytic and very subordinated IAB-like basaltic lava flows at-583 Ma. The caldera eruption seems to have been initiated by the production of pumiceous fallouts during an early Plinian-like period of decompression of shallow magma chambers at-580 Ma, during which the rift-related structural framework of the Basin Stage probably controlled the collapse of a graben-like caldera. Compositional and isotopic signatures suggest lithospheric mantle sources for the magmas from both volcanic stages and support a connection between basic-intermediate and silicic rocks from both bimodal associations. They also suggest a cogenetic nature between the silicic rocks from the Caldera Stage and the A-type granitoids from the nearby plutonic Graciosa Province.(c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. (AU)