Constraints on the Statherian evolution of the intraplate rifting in a Paleo-Mesoproterozoic paleocontinent : new stratigraphic and geochronology record from the eastern São Francisco craton.

摘要: Abstract An integrated approach of stratigraphic analysis and U–Pb age dating reveals some information on the tectono-sedimentary evolution Statherian cover Sao Francisco craton in so-called Espinhaco basin (Atlantic shield eastern Brazil). Here, continental sedimentation patterns, such as alluvial fan, braided-plain lacustrine facies associations, with associated volcanic rocks are documented two superposed fill-successions, which defined Algodao Sapiranga Synthems grouped Botupora Supersynthem. Both studied units consist mainly conglomerates cross-bedded sandstones minor amounts mudstones, sedimentary breccias, lava beds volcaniclastic rocks, were deposited a rift – during syn-rifting phases. The Synthem represents first rifting phase. basal synsedimentary this unit by subaerial debris flows, most likely along near border fault. framework rock consists only crystalline clasts from basement no fragments rocks. Detrital zircon grains that extracted show ages older than 2.05 Ga. remainder section is dominated fluvial sandy lithofacies conglomerate lenses sandstone–mudstone heterolithic lithofacies, represent distal, waning-flood deposits environment. upper also contains hummocky cross-stratified sandstone related to storm-influenced deposition. On top succession, dated at 1775 ± 7 Ma, was interpreted final rift-phase. Representing second rift-phase, shows similar patterns Synthem. rests directly Synthem, its (which master fault) contain voluminous detrital 1741 ± 14 1766 Ma well 2.05 Ga. succession record 1740 ± 10 Ma, finalized evolution. A preliminary geochemical study Supersynthem showed these alkaline high K 2 O/Na O ratios, belong an ultrapotassic suite. low concentrations MgO wt.% suggest felsic character. unconformably covered volcano-sedimentary rift-succession EoCalymmian — Pajeu stage basin. Several Statherian-related sequences anorogenic granitoids occur dispersed block, requires regional geologic model explain extensional magmatism process time. We used last Columbia paleocontinental reconstruction constrain processes relating them far-field magmatic part silicic LIP, triggered convection-driven tectonic-plate motion western Atlantica block inside supercontinent.