Abstract

JAPAS, María Silvia; URBINA, Nilda Esther  and  SRUOGA, Patricia. Structural control on Neogene volcanism and related ore deposits at Cañada Honda district, San Luis province. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.4, pp.494-506. ISSN 0004-4822.

Located at the transitional southern end (33° S) of  the Pampean flat-slab, the Tertiary volcanic belt records the eastward migration of  the Andean volcanic arc due to the flattening of  the Nazca Plate in Mio-Pliocene times. The tertiary volcanic belt encompasses several very important metallogenetic districts in the San Luis Pampean Ranges. Volcanic rocks and associated ore-deposits crop out  following  a NW-WNW  trending belt  at La Carolina, Cañada Honda  - Cerros Largos, Cerros del Rosario  and El Morro volcanic fields. The available geochronological data indicate that the volcanic activity began early at the western end of the belt and ended ~ 10 Ma later at its eastern border. Cañada Honda district represents the oldest and longest-lived volcanic field of  the tertiary volcanic belt. It records eruptive events and related hydrothermal alteration from 12-13 Ma to 7.3 Ma, including lavas and volcaniclastic products. Preliminary structural analysis shows that previous structures have strongly controlled, either directly or indirectly, the emplacement of  volcanic rocks and related mineral deposits. Kinematic and strain fabric analyses allow to recognize two volcano-tectonic associations. One of  these associations would be related to dextral reactivations of  structures parallel to basement foliation. On the other hand, the main one would be  linked with the generation of two volcano-tectonic depressions which are aligned  in a NW-WNW direction. Their dominant structures trend NW-WNW and reveal sinistral-normal motions, both at local and Tertiary volcanic belt scales.

Keywords : Pampean flat-slab; Pampean Ranges; Tertiary volcanic belt; Ore-deposits; Structural control.

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