Abstract

MUZIO, Rossana et al. MESOZOIC MAGMATISM IN EAST URUGUAY: PETROLOGICAL CONSTRAINTS RELATED TO THE SIERRA SAN MIGUEL REGION. Earth Sci. Res. J. [online]. 2009, vol.13, n.1, pp.16-29. ISSN 1794-6190.

This work presents new results of a detailed geological and structural investigation focusing the easternmost Uruguayan Mesozoic magmatic occurrences related to the south Atlantic opening. Lithological descriptions, their stratigraphic relationships and complimentary lithochemical characterizations carried out in the San Miguel region (East Uruguay) are presented. Three volcanic/sub-volcanic units have been recognized. The fel-sic volcanic association is composed by rhyolitic - dacitic flows, mainly with porphyritic textures and sub-alkaline nature and related pyroclastic rocks. The felsic sub-volcanic association is characterized by granophyres of about 25 km2 of exposed area, cross- cut by mafic and felsic dykes. Finally, a mafic association has been identified characterized by dykes and a small intrusion of gabbroic composition. All these units are Mesozoic in age (130- 127 Ma) and according to their chemical nature they correspond to sub-alkaline to weak peralkaline magmas.

Keywords : petrography; geochemistry; Mesozoic; Uruguay.

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