Abstract

LAJOINIE, María F; ETCHEVERRY, Ricardo O; LANFRANCHINI, Mabel E  and  CABANA, María C. Geología, geoquímica y génesis de diques proterozoicos del área de San Miguel, sierras septentrionales de la provincia de Buenos Aires. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.3, pp.404-415. ISSN 0004-4822.

The crystalline basement of the Sierras Septentrionales is intruded by numerous Proterozoic dikes of basic, intermediate and acid composition, which are used as a tool of correlation between different tectonomagmatic units. In the San Miguel area, the petrological and geochemical analyses allowed the interpretation of their main genetic processes, and the identification of two well-defined lithological types of dikes: Granitic and andesitic-basaltic. The first one corresponds to calc-alkaline, metaluminous granites and granodiorites, with a peraluminous tendency and with a syn-collisional to volcanic arc geochemical signature. Rare earth elements geochemical analyses performed on different granitic dikes show similarities in their composition indicating that they are genetically associated. This is the first study executed on granitic dikes in the Sierras Septentrionales, as only the presence of granitic sills hosted in gneissic rocks, near Tandil city, had been cited. The andesiticbasaltic dike is calc-alkaline-medium potassium. According to the analysis of multi-element diagrams, this body has a similar distribution pattern to the calc-alkaline dikes of the Sierras Septentrionales, whose age is ~2000 My.

Keywords : Basement; Dikes; Rare earth elements; Sierras Septentrionales.

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