Compositional Evolution of the Variscan Intra-Orogenic Extensional Magmatism in the Valencia del Ventoso Plutonic Complex, Ossa-Morena Zone (SW Iberia): A View from Amphibole Compositional Relationships

The Ossa-Morena Zone (OMZ), SW Iberia, has numerous Lower Carboniferous compositionally zoned plutons that formed in a Variscan intra-orogenic extensional setting. This magmatism shows wide compositional variation comprising alkaline, transitional, and calc-alkaline suites. suite was produced by hybridization of alkaline magmas with felsic melts generated crustal anatexis related to the intrusion mafic middle crust. In this work, we present textural mineralogical study Valencia del Ventoso main pluton from OMZ track evolution during using constraints amphibole compositions determine P-T conditions emplacement amphibole-based thermobarometry. exhibits reverse zoning an inner facies containing dolerites, gabbros, quartz diorites, intermediate transitional outer diorites monzogranites. Magmas border crystallized under oxidizing at relatively low temperatures (range: 640–760 °C) ca. 280–300 MPa, implying near H2O-saturated conditions. These rock show evidence between mildly alkalic magmas. former is inferred occurrence antecrysts labradorite-andesine, high-Ti pargasite-hastingsite, biotite deficiency tetrahedral-site occupancy, distinctive feature dolerites. contrasts later crystallization magma andesine-oligoclase, low-Ti magnesiohornblende-edenite, full occupancy. Constraints amphibole-melt relationships antecrystic suggest magmatic component could have high- ultra-K affinity.