La Carolina pull-apart in western Tertiary Volcanic Belt, pampean flat-slab (33° S), Argentina

SILVIA JAPAS; NILDA URBINA; PATRICIA SRUOGA; GALLARD MARÍA CECILIA

Heidelberg

Simposio; 22nd Colloquium on Latin American Geosciences; 2011

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Located at the transitional southern end of the Pampean flat-slab in central-western Ar­gentina (Ramos et al., 2002), the tertiary volcanic Belt (tvB) records the eastward migration of the Andean volcanic arc due to the flattening of the nazca Plate in Mio-Pliocene times. Volcanics and associated ore-deposits crop out following a ~ 80 km long, nW-WnW trending belt that from west to east includes La Carolina, Cañada Honda -Cerros Largos, Cerros del Rosario and El Morro districts. at the 10 km2 La Carolina district, volcanic activity took place between 8.2 to 6.3 Ma and it comprises andesitic, lacitic and trachytic lavas, domes and dykes, closely associated with phreatic breccias and base surge deposits (Sruoga et al., 1996 and references therein). Related to a maar-diatreme system (Sruoga et al., 1996) there are several small mineralizations of auag low-sulphidation, epithermal type (urbina et al., 1997, urbina & Sruoga 2009). Structural analysis shows that previous structures have strongly controlled the emplace­ ment of volcanic rocks and related mineral deposits at La Carolina (Japas et al., 2011). Two parallel-to-the-foliation sets of faults (n-S and nnE) bound this rhomboid-shaped volcanic district. Slip on the main n-S faults indicates dominant right-lateral motions whereas nnE faults show components of vertical slip. The presence of this gentle deflection in the foliation trend (~30º) resulted in a nnE releasing bend allowing magma emplacement. in this pull-apart structure, vol­canic domes are aligned following a nnE trend. these and previous results at Cañada Honda (Japas et al., 2010) confirm strike-slip structures controlling Tertiary volcanic emplacement at the western tvB.