High heat flow in southern Tibet

Abstract

Heat flow measurements have been attempted in two freshwater lakes at altitudes of 4.5 and 5.0 km, south of the Yarlung–Zangbo suture zone in southern Tibet. Probe penetration in the lake sediments was deep enough in the case of eight measurements (5.5–7.2 m) to give reliable temperature gradients. Corrections for seasonal temperature variations, topographic and refraction effects have been applied to the data. In a north–south profile trending perpendicular to the Yarlung–Zangbo suture zone, heat flow is approximately constant at 146 mWm−2 over a distance of 30 km and drops to a value of 91 mW m−2 in <25 km. The high heat flow and the sharp spatial variation both suggest the existence of a heat anomaly located at relatively shallow depths (no greater than 25 km) in the Tibetan crust, probably due to the recent emplacement of plutonic bodies.