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1. IntroductionThe Paramillos de Uspallata Pb-Ag-Zn vein deposit is located in the northern part of the Cuyo rift basin developed in the Triassic (~235 Ma) linked to the collapse of Permian regional orogen and the beginning of the Gondwana supercontinent breakup (Figure 1a). The rift development is controlled by a large-scale NNE mechanical anisotropy and NW crustal-scale reactivated structures. The basin infill consists of continental sediments with locally interbedded alkaline basaltic lavas and rhyolitic tuffs and minor basaltic dykes overlying a Paleozoic volcano-sedimentary basement. The geochemistry of the basaltic magmatism suggests crustal contamination with basement Permian volcanic rocks. During the Tertiary, the Andean orogeny inverted the basin reactivating previous structures and produced arc volcanism.The Paramillos de Uspallata deposit includes thirty-three subvertical veins emplaced along dextral and oblique-normal faults with NE-trending, coincident with Permian orogeny structures, and less E-W- trending (Figure 1a). The veins are up to 2 meter thick and up to 2.5 km in length and have banded, crustiform, cockade and breccia textures. They are composed of sphalerite, galena, chalcopyrite, pyrite, marcasite, freibergite-tetrahedrite with minor boulangerite, pyrargirite and owyheeite in a siderite with minor quartz gangue. Fluid inclusions and isotopic analyses revealed that the ore fluids had low temperature, low to moderate salinityand resulted of the mixing between magmatic/metamorphic and meteoric fluids. Initially, these veins were consider as related with the Miocene Cu-porphyry deposits outcropping in the area, however, recent studies show that the Paramillos de Uspallata vein deposit is genetically linked to the extensional tectonic that followed the collapse of the Permian orogen and resulted in the rift formation and the consequent diastathermal metamorphism which would have triggered the hydrothermal system.2. MethodsTwo galena and three sphalerite samples from different veins were analyzed for lead isotopes at the Geochronological Research Centre of the University of São Paulo. Clean grains were carefullyselected and Pb concentrates were prepared following standard methods. The isotopic analyses were carried out on a multicollector micromass spectrometer.The results were compared with previous lead isotopic data from the more likely sources of lead that are the basalts host rocks of the deposit and Permian arc volcanic that conform the basement of the rift Cuyo basin.2. ResultsThe lead isotope composition of galena is slightly variable in 207Pb/204Pb and 206Pb/204Pb, and is distinctly lower than those of the host basalts, what point out the involvement of an older source for this metal. Likewise, in the plumbotectonic diagrams the vein samples plot close to the orogen defining roughly linear array with the basalts and the Permian volcanic (green dashed line, Figure 1b).Figure 1: a) Veins location (in red) and outcropping distribution of Triassic and Miocene rocks in the area. b) Thorogenic diagram showing plumbotectonic curves (black), galena and sphalerite of the Paramillos de Uspallata veins (squares) and the Permian volcanics (triangle) composition.3. ConclusionThe lead isotopic signature of the Paramillos de Uspallata Pb-Ag-Zn vein deposit suggests that the lead was sourced not only by the basaltic magmatism linked to the rifting but also by the Perminan volcanics that form the basement of the rift basin. This is consistent with the genetic model of the rift-related ore deposits in which Pb derives from a mixture of rocks with a long period of residence in the upper crust and rocks deformed during repeated orogenic cycles. In this context, crustal-scale reactivated structures would have acted as the main conduits for metals transport from the basement upward.