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 Logrosan granite represents one of those granitic bodies and is the focus of this study. The Logrosan 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 [sup.87]Sr/[sup.86]Sr ratios vary from 0.7125 to 0.7286, whereas initial [epsilon]Nd shows a restricted range from -4.3 to -4.0 and [epsilon][Hf.sub.(t)] ranges from +5.7 to -10.5 for Variscan-age zircons. Inherited zircons exhibit mostly Neoproterozoic ages and juvenile [epsilon]f-isotope composition (sHf 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 Logrosan granite. Keywords: Sr-Nd isotopes, zircon Hf isotopes, fractionated S-type granites, tin granites, Iberian Variscan Belt La orogenia Varisca produjo una gran cantidad de granitos a lo largo del Cinturon Varisco Europeo. En relacion con el engrosamiento cortical se emplazaron tardiamente granitos de tipo-S, muy fraccionados y ricos en Sn. El presente estudio se centra en uno de esos cuerpos graniticos, el granito de Logrosan. El pluton de Logrosan forma parte del Batolito de Extremadura Central (BEC), en la Zona Centroiberica (ZCI), y se emplazo durante las etapas tardias de la orogenia Varisca, a los ca. 308 Ma, segun los datos combinados de geocronologia de U-Pb por ID-TIMS y por LA-ICPMS. El cuerpo granitico intruyo los metasedimentos del Complejo Esquisto Grauvaquico (CEG) de edad fundamentalmente Neoproterozoica. En el pluton se distinguen, de acuerdo a la petrografia y a la geoquimica de roca total, un leucogranito de dos micas de tamano de grano medio-grueso moderadam