Use of Pb and Sr isotopes on the determination of lead mineralization sources from Ribeira valley - Sao Paulo and Parana states

A lead and strontium isotope study was carried out on galena, barite and calcite from Pb-Ag syngenetic stratiform (Perau type) and hydrothermal veins (Panela type) deposits from Vale do Ribeira region (Sao Paulo and Parana states). The leads from the Perau and Panelas type deposits have respectively isotope ratios (sup(206)Pb/ sup(204)Pb 16.157 to 16.505 amd 16.520 to 17.273; sup(207)Pb/ sup(204)Pb = 15.466 to 15.720 and 15.470 to 15.780 and sup(208)Pb/ sup(204)Pb = 36.370 to 36.763 and 37.043 to 38.243), that defined a Stacey and Kramers model ages mainly concentrate within 1.7-1.5Ga. A review of published Pb isotopic compositions for these deposits and considerations of new Sr isotope data and Pb results using plumbotectonics model, indicate that the Perau type mineralizations are related to the syngenetic process and the Pb are derived from upper crust with a short crustal residence time. For the Panelas type deposits the Pb and Sr isotope studies support the conclusion that the ores were emplaced during regional metamorphism and the Pb were derived from lithologically complex source which may include metasedimentary and basement rocks. (author)