Petrological interpretation of the magnetotelluric data of the depth zone of the Tarim and Tien Shan junction

Electrical conductance of lower crust and mantle rocks samples from the Tarim and Tien Shan junction zone were measured in a laboratory under P-T conditions determined on the basis of thermobarometry data. The geothermic curve for the moment of xenolith delivery (K - \rlap- P)(K - \rlap{--} P) corresponding to a thermal flux of 80 mW/m² was determined. Its comparison with the present-day geothermic curve corresponding to 60 mW/m² demonstrates general cooling of the lithosphere. The Moho surface position also changed from 35–40 km (as the boundary between lherzolites and granulites) to 55–60 km, as a proper geophysical Moho discontinuity. Results of laboratory measurements of electrical conductance of upper mantle and lower crust rocks samples in correlation to geoelectric and thermal models make it possible to define lherzolite, granulite, and eclogite massifs in the depth zone of the Tarim and Tien Shan junction.