Quantifying partial melt fraction in the crust beneath the Central Andes and the Tibetan plateau

An interdisciplinary approach is used to quantify partial melt fractions and to infer the origin and distribution (melt structure) of melts located in the crust beneath the Central Andes and the Tibetan plateau. In these areas field observations of Low Velocity: Zones (LVZ) and High Conductivity Zones (HCZ), which are commonly attributed to partial melting, are used to quantify melt fractions. Additional information is obtained from nu (p)/nu (S) ratios, seismic attenuation data, and heat flew density and gravity anomalies. These data accompanied bq thermal modelling suggest that melts of mainly crustal origin are interconnected through dykes and veins. Experimental results and model calculations indicate that the minimum fraction of melt necessary; to describe the LVZs and HCZs in the Central Andes and the Tibetan plateau is approximately 20 vol.%, and the melt has a non-ideal interconnectivity. (C) 2001 Elsevier Science Ltd. All rights reserved.