Magmatism in the Asunción-Sapucai-Villarrica Graben (Eastern Paraguay) Revisited: Petrological, Geophysical, Geochemical, and Geodynamic Inferences

The Asunci´on-Sapucai-Villarrica graben (ASV) in Eastern Paraguay at the westernmost part of the Paran´a Basin was the site\udof intense magmatic activity in Mesozoic and Tertiary times. Geological, petrological, mineralogical, and geochemical results\udindicate that the following magmatic events are dominant in the area: (1) tholeiitic basalt and basaltic andesites, flows and sills\udof low- and high-titanium types; (2) K-alkaline magmatism, where two suites are distinguished, that is, basanite to phonolite and\udalkali basalt to trachyte and their intrusive analogues; (3) ankaratrite to phonolite with strong Na-alkaline affinity, where mantle\udxenoliths in ultramafic rocks are high- and low-potassium suites, respectively.Thestructural and geophysical data show extensional\udcharacteristics for ASV. On the whole, the geochemical features imply different mantle sources, consistently with Sr-Nd isotopes\udthat are Rb-Nd enriched and depleted for the potassic and sodic rocks, respectively. Nd model ages suggest that some notional\uddistinct “metasomatic events”may have occurred during Paleoproterozoic to Neoproterozoic times as precursor to the alkaline and\udtholeiiticmagmas. It seems, therefore, that the genesis of the ASVmagmatism is dominated by a lithosphericmantle, characterized\udby small-scale heterogeneityFAPESP - 08/38807-4, 10/50887-