Polymetallic (Pb-Zn-Cu-Ag±Au) vein-type deposits in brittle-ductile transtensional shear zones, Eastern Sierras Pampeanas (Argentina): age constraints and significance for the Late Paleozoic tectonic evolution and metallogenesis

MAFFINI, MARÍA NATALIA; WEMMER, KLAUS; RADICE, STEFANÍA; ORIOLO, SEBASTIÁN; D'ERAMO, FERNANDO JAVIER; CONIGLIO, JORGE ENRIQUE; DEMARTIS, MANUEL; PINOTTI, LUCIO PEDRO

ORE GEOLOGY REVIEWS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 89 p. 668 - 682

0169-1368

This paperdiscusses new structural, kinematic and geochronological data from polymetallic(Pb-Zn-Cu- Ag±Au) vein-type deposits hosted in the metamorphic basement of thesouthern Sierras de Córdoba. A Carboniferous age was established for thehydrothermal event between ~329-315 Ma (Late Mississippian-Early Pennsylvanian)by the K/Ar fine-fraction dating method of sericitic alteration related tometallic ore deposition in the Las Guindas and Oro districts. The obtained agespostdate the spatially associated Devonian magmatism and overlap A-type EarlyCarboniferous magmatism defined for the Eastern Sierras Pampeanas. The presenceof non-exhumed granitic bodies at shallow depths, possibly related tomineralization, is supported by available geophysical and field evidence. Strainfabric and 3-D kinematic analyses constitute first kinematic data for theCarboniferous basement of the Southern Sierras Pampeanas and demonstrate thatmineralization was controlled by NNW- and ENE25 ndingbrittle-ductile transtensional shear zones that overprint the earlierhigh-strain deformation fabrics of the basement. Transtensional deformation hasaccommodated large amounts of strike-slip movements and subordinatedextensional components. The calculated kinematic axes indicate a coherentkinematic pattern of the mineralized systems in the two studied districts, witha maximum extension direction oriented NNE- to NE and maximum shorteningdirection oriented WNW- to NW These deformation imes, active duringmineralization, point to 30a non-compressive setting at theLate Mississippian-Early Pennsylvanian boundary. In line with other regionalevidence, we propose a distinctive Carboniferous deformational phase in theEastern Sierras Pampeanas, dominated by transtension. Thisperiod would have occurredafter the transition with the Devonian compressional/transpressional orogenicregime.