Zircon U-Pb and Hf isotopic constraints on the genesis of a post-kinematic S-type Variscan tin granite : the Logrosán cupola (Central Iberian Zone)

The Variscan Orogeny produced widespread granites along the European Variscan belt. In relation to crustal thickening, post-collisional multiple Sn-bearing highly fractionated S-type leucogranites were emplaced. The Logrosán granite represents one of those granitic bodies and is the focus of this study. The Logrosán granite is located in the Central Extremadura Batholith, within the Central Iberian Zone (CIZ) and was emplaced during post kinematic stages of the Variscan Orogeny at ca. 308 Ma, as determined by combined U-Pb ID-TIMS and LA-ICPMS geochronology. The granitic body intruded the metasedimentary Schist Greywacke Complex (SGC) of Neoproterozoic age. A moderately evolved medium- to coarse-grained two mica leucogranite (Main Unit) and several highly evolved aplitic or microporphyritic units (Evolved Units) have been distinguished based on their petrography and whole rock geochemistry. Initial ⁸⁷Sr/⁸⁶Sr ratios vary from 0.7125 to 0.7286, whereas initial εNd shows a restricted range from -4.3 to -4.0 and εHf(t) ranges from +5.7 to -10.5 for Variscan-age zircons. Inherited zircons exhibit mostly Neoproterozoic ages and juvenile Hf-isotope composition (εHf up to +14.7) analogous to zircons from the SGC metasediments. The available geological, geochronological, geochemical and isotopic data allow us to propose partial melting of heterogeneous Neoproterozoic metasediments, similar to the outcropping SGC materials for the genesis of the Logrosán granite.20 page(s