Geochronology and decoupling controls of Sn-(Ta-Li) and W-(Sn) mineralization in the Iberian Variscan Massif, Spain and Portugal

Abstract

Sn-W mineralization in the Iberian Variscan Massif (corresponding with the western zone of the Iberian Peninsula, in Spain and Portugal) occurs closely related to metaluminous to peraluminous granitoids of Variscan age. The deposits are grouped into two main styles of mineralization; Sn-(Ta-Li) and W-(Sn) deposits. Within this work we present a first attempt to correlate timing of W-Sn mineralization and plutonic events at a regional scale. We report new ⁴⁰Ar/³⁹Ar dates of muscovite related to the quartz-muscovite alteration of eleven deposits, molybdenite Re-Os dates from six deposits and two new zircon U-Pb dates of granitoids genetically related to the mineralization. The dates obtained support the relationship between W-Sn mineralization with specific, but not uniquely just one, granite suites. The dominant S-type peraluminous Variscan granitic suites in Iberia, the S₁-type dated at ca. 330–311 Ma and the S₂-type at ca. 314–296 Ma, are related to both, Sn-(Ta-Li) and W-(Sn) mineralization. A subgroup of deposits of the W-(Sn) group, generally enriched only in W but not in Sn is associated with the youngest but volumetrically less abundant I-type (ca. 303–280 Ma) metaluminous magmatism. The relationship of both the Sn-rich and W-(Sn)-rich deposits with the highly peraluminous S-type granites suggest that the ultimate source of the melts is not related to the decoupling between Sn and W. Therefore, the causes of W and Sn separation may be related to late-stage magmatic and magmatic-hydrothermal processes.