Dacite Genesis via both Slab Melting and Differentiation: Petrogenesis of La Yeguada Volcanic Complex, Panama

La Yeguada volcanioc complex (LYVC) is one of many major volcanoes that represent the extension of the Central American arc in western Panama and that have resulted from current oblique subduction south of Panama. There are two major phases of calc-alkaline volcanic activity at LYVC based on mapping and K-Ar radiometric dates. The first phase began at ˜ 13 Ma and ceased at ˜ 7·5 Ma. This sequence, termed the old group, consists of basalts to rhyolites with typical arc mineralogies (OL, CPX, PL, MGT, and OPX). The samples have similar radiogenic Sr and Nd values and appear to be related by fractional crystallization with assimilation and/or magma mixing involved in the differentiation. The parental basalts were probably derived from the metasomatized mantle wedge via melting induced by fluids released from the subducted lithosphere. There was an apparent period of minor volcanic activity from 7–5 to 2–5 Ma (only one documented sample from this period). The second phase (