RADIOACTIVE ELEMENTS OF ROCKS IN NORTH CHINA PLATFORM AND THE THERMAL STRUCTURE AND TEMPERATURE DISTRIBUTION OF THE MODERN CONTINENTAL LITHOSPHERE
CHI QING-HUA;YAN MING-CAI(Institute of Geophysical and Geochemical Exploration, MGMR Langfang 065000, China)
In a total area of 1.4 ×106 km2 in North China Platform (NCP), 12193 rock samples were systematically collected and combined into 1207 composite samples.Heat-producing elements K. Th and U were analyzed by XRF or ~ using national primary geochemical certified reference materials of rocks for data quality monitoring. Based on the contents of K. Th and U in rocks and rock composition of the crustal layers, the contents of K. Th and U in crustal layers are calculated. The heat production of rocks and the strata of various ages in NCP are studied. The thermal structure and temperature distribution of modern continental lithosphere in NCP has been established. With the one-dimensional steady-state thermal conduction model,the depth-temperature distribution curve of the current continental lithosphere in NCP is given .In this study the authors indicate that the crustal melting of the current continental lithosphere in NCP is not obvious from surface heat flow and depth-temperature curve. Compared with other great stable craton regions, there is greater crustal activity of NCP which has paraplatformal characteristics.