Artículos de revistas
Magmatism in the Asunción-Sapucaí-Villarica Graben (Eastern Paraguay) revisited: petrological, geophysical, geochemical, and geodynamic inferences
Fecha
2013Registro en:
Journal of Geological Research, New York, v. 2013, p. ID590835/1-ID590835/22, 2013
1687-8833
10.1155/2013/590835
Autor
Comin-Chiaramonti, Piero
De Min, Angelo
Cundari, Aldo
Girardi, Vicente Antonio Vitorio
Ernesto, Marcia
Gomes, Celso de Barros
Ricomini, Claudio
Institución
Resumen
The Asunci´on-Sapucai-Villarrica graben (ASV) in Eastern Paraguay at the westernmost part of the Paran´a Basin was the site
of intense magmatic activity in Mesozoic and Tertiary times. Geological, petrological, mineralogical, and geochemical results
indicate that the following magmatic events are dominant in the area: (1) tholeiitic basalt and basaltic andesites, flows and sills
of low- and high-titanium types; (2) K-alkaline magmatism, where two suites are distinguished, that is, basanite to phonolite and
alkali basalt to trachyte and their intrusive analogues; (3) ankaratrite to phonolite with strong Na-alkaline affinity, where mantle
xenoliths in ultramafic rocks are high- and low-potassium suites, respectively.Thestructural and geophysical data show extensional
characteristics for ASV. On the whole, the geochemical features imply different mantle sources, consistently with Sr-Nd isotopes
that are Rb-Nd enriched and depleted for the potassic and sodic rocks, respectively. Nd model ages suggest that some notional
distinct “metasomatic events”may have occurred during Paleoproterozoic to Neoproterozoic times as precursor to the alkaline and
tholeiiticmagmas. It seems, therefore, that the genesis of the ASVmagmatism is dominated by a lithosphericmantle, characterized
by small-scale heterogeneity