HEATING GENERATION MODEL FOR THE CONTINENTAL CRUST BASED ON THE MAIN HOLE OF THE CHINESE CONTINENTAL SCIENTIFIC DRILLING PROJECT

Abstract

Systemic measurements on the concentrations of the radiogenic elements U, Th and K for the 149 core samples obtained from the main drilling hole of the Chinese Continental Scientific Drilling Project (CCSD) have been perforvaed. Combined with the previously published data at shallow depth in the same hole, a detailed vertical distribution of heat generation is provided for the uppermost 5km of the crust. Within two depth intervals, above 1650m and 1650 ~ 5000m, the heat generation increases with depth respectively. It indicates a specific pattern of heat generation distribution that is different from the normal continental crust. Based on the measurements together with the lithological layers of the crust, this paper presents a heat generation model for the crust of the Sulu ultra-high pressure metamorphic belt. In this model, the crust is 32km thick, including three layers. The upper crust (0 ~ 10km) is composed of ultra-high pressure metamorphic rocks. It is divided into several sub-layers in detail, and the heat generation varies from 0.49 μWm-3 to 1.73 μWm-3. The middle crust (10 ~ 20 km) is comprised mainly of the gneiss with a heat generation of 1.51 μWm-3. The lower crust (20 ~ 32km) is granulite with a heat generation of 0.31μWm-3. The total crust heat flow is 31 mW/m2, and only 39% comes from the upper crust, which is much lower than the normal continental crust such as the North China craton and the lower Yangtze area. It indicates that the vertical distribution of heat generation in the Sulu ultra-high pressure metamorphic belt, formed by the collision between Sino-Korea and Yangtze cratons, is different from the normal crust such as the North China and Lower Yangtze cratons.