Melting Inside the Tibetan Crust? Constraint From Electrical Conductivity of Peraluminous Granitic Melt

Abstract Magnetotelluric and seismological studies suggested the presence of partial melts in the middle to lower Himalaya‐Tibetan crust. However, the melt fractions inferred by previous work were based on presumed electrical conductivity of melts. We performed measurements on the electrical conductivity of peraluminous granitic melts with 0.16–8.4 wt % H 2 O (the expected compositions in the Tibetan crust) at 600–1,300°C and 0.5–1.0 GPa. Peraluminous melt exhibits lower electrical conductivity than peralkaline melt at dry condition, but this difference diminishes at H 2 O > 2 wt %. With our data, the observed electrical anomalies in the Tibetan crust could be explained by 2–33 vol % of peraluminous granitic melts with H 2 O > 6 wt %. Possible reasons for our inferred melt fractions being higher than seismological constraints include the following: (1) The real melts are more Na and H 2 O rich, (2) the effect of melt reducing seismic velocities was overestimated, and (3) the anomalies at some locations are due to fluids.