A Proterozoic basement under the northern Frontal Cordillera: A hint to Chilenia and the continuation of the accretionary prism east of the Precordillera?

ASTINI R.A.; CAWOOD, P.A.

Santiago, Chile

Congreso; XII Congreso Geológico Chileno; 2009

Universidad de Chile, Santiago y Sewrvicio Geológico y Minero de Chile

Large parts of the Late Paleozoic units in central Chile and the Frontal Cordillera in Argentina, as well as the Mesozoic succession along the main Andes, largely within the flat-slab segment, are believed to be underlain by a distinct, but poorly known, terrane named Chilenia. Recent mapping combined with U-Pb detrital zircon ages allow us to interpret basement exposed southeast of Laguna Brava, which suggests a strong link with the Gualguaraz Complex between the Precordillera and Frontal Cordillera. The absence of any lower Paleozoic detrital ages from the analysed strata makes it difficult to reconcile these data with an accretionary prism that received detritus from an eastern source. A better interpretation is to consider these rocks as a sedimentary cover of the Chilenia terrane that would yield Proterozoic ages with a youngest event being Neoporterozoic.