Proveniência do sistema fluviolacustre pós-ordoviciano da Formação Diamantino: preenchimento sedimentar e rota de sedimentos

Abstract

The Diamantino Formation encompasses a fluviolacustrine system founded in the central region of Brazil, in the southeastern part of Mato Grosso state. Initially, its evolution was linked to the Alto Paraguai Group within the Paraguai Belt, in the context of a foreland basin. However, the discovery of skolithos ichnofacies at the base of the Alto Paraguai Group proposed a Phanerozoic tectono-stratigraphic scenario for the Raizama, Sepotuba, and Diamantino formations. This new interpretation led to repositioning the Diamantino Formation from the Cambrian to the Ordovician, although the paleogeography associated with this change has not been extensively discussed. Previous studies suggested that the metasediments from the Paraguai-Brasília Belts and the Goiás Magmatic Arc were the main source areas for this sedimentation, supported by paleocurrent data indicating sediment migration from southeast to northwest. During the Ordovician, extensive subsidence zones in West Gondwana related to the Oclóic orogeny enabled the establishment of the first sedimentary systems of the Paraná Basin over the cores of the Paraguai, Brasília, and Ribeira Belts. In this scenario, the presence of these deposits may suggest the coexistence of sediment pathways from the Central Brazil units and the Diamantino Formation, offering new insights into the paleogeography of this portion of West Gondwana. Additionally, it is noteworthy that during the Cambrian, no deposits of the Paraná Basin were observed, whereas in the Ordovician, the presence of these deposits suggests the possibility of coexistence or even the transformation of these systems into source areas for the Diamantino Formation. In this dissertation, we investigated the sediment provenance of the Diamantino Formation to compare and reassess the characterization of sedimentary fill and sediment pathways used in this sedimentation. Five stratigraphic profiles, seventeen sedimentary petrography analyses, nine heavy mineral analysys, five Samarium-Neodymium samples, and two Uranium-Lead samples in detrital zircon were studied. Petrographic data indicate that the rocks of the Diamantino Formation are composed of metasiliciclastic lithoquartzose sand. The transparent heavy mineral assemblage consists mostly of ultra-stable heavy minerals (zircon, tourmaline, and rutile, averaging 94.5% of the ZTR index). The presence of metasiliciclastic sand and an ultra-stable heavy mineral assemblage suggest that the Diamantino Formation has a polycyclic history. The basal deposits of the Diamantino Formation consist of sediments deposited in a lacustrine environment. Nd provenance ages and detrital zircon families are restricted to 1.63 Ga and Mesoproterozoic and Paleoproterozoic ages, respectively. The top deposits consist of fine sandstones and mudstones deposited in a fluviodeltaic environment. Nd provenance ages of the samples vary around 1.3 Ga and show a rich contribution of families from the Neoproterozoic-Cambrian interval. To analyze the detrital zircon signatures of the Diamantino Formation, 221 ages from the unit's zircons were compared with 5748 ages from the Brasília and Paraguai orogens and units from the Ordovician-Cretaceous of the Paraná viii Basin. The application of multidimensional scaling on Nd provenance ages and detrital zircon in comparison with potential source areas suggests that Diamantino sedimentation presents a complex sediment exchange during the expansion of the lacustrine basin. The high Q/F ratio, absence of a ferromagnesian assemblage, and scarcity of Riacian ages in detrital zircon populations weaken the hypothesis of direct influence from the Brasília Belt and Goiás Magmatic Arc. The presence of detrital ages from the Cambrian-Ordovician boundary (528-485 Ma) demonstrates a series of potential protosourcers that are not in cratonic areas of West Gondwana and represent significant source areas for the Ivaí River Group in the Paraná Basin. The multiproxy analysis suggests that the main sediment pathway for the Diamantino Formation had a source area mixture of sediments from the Paraguai Belt, Araras-Alto Paraguai Basin, and the northern Paraná Basin. In this sense, the data published in this dissertation suggest a genetic or erosive connection with the mid-Paleozoic deposits of the Central Brazil region.