Radioactive heat-producing element abundance in the crust of continental China estimated from terrestrial heat flow and the helium isotopic composition of underground fluids
WANG Yang1,2 (1. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China; 2. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China)
Based on the law of conservation of energy and heat flow data in continental China, the upper limit of heat production for the crust beneath continental China is determined as 1.3μWm-3. Then, using the data of the heat flow and helium isotopic composition of underground fluids, the heat productions of various tectonic units in the crust of continental China are estimated to be in the range of 0.58-1.12μWm-3 with a median of 0.85μWm-3, and the corresponding U, Th and K abundances are in the ranges of 0.83-1.76μg/g, 3.16-6.69μg/g and 1.0%-2.12% respectively. These data indicate that the abundances of the radioactive elements U, Th and K in continental crust of China are notably higher than those in the Archean crust, suggesting that the components of continental crust of China are highly evolved. In addition, the crustal composition of continental China exhibits significant lateral heterogeneity. The crust beneath eastern China is enriched in highly incompatible elements such as U, Th and K relative to that beneath western China, and the crust beneath fold belts is enriched in U, Th and K relative to that beneath cratonic areas. It is inferred on the basis of a positive correlation between the SiO2 content and heat production of continental crust that the crust beneath eastern China and fold belts are more felsic than beneath western China and cratons. This regional variation is consistent with the results of inference from the seismic wave velocity data in China. According to the fact that the seismic wave velocity and heat production range of the crust of continental China are lower than the global average values, combined with a comparison with the global crustal composition models published by previous studies, it is deduced that the abundances of highly incompatible elements such as U, Th and K in continental crust are overestimated in the average composition models of global continent crust constructed by Rudnick and Fountain (1995), Rudnick and Gao (2003), Weaver and Tarney (1984), Shaw et al. (1986) and Wedepohl (1995).
【Fund】： 国土资源部科技发展计划“中国岩石圈三维结构”(200010101);; 国家自然科学基金项目(40376013 40104003);; 中国博士后科学基金资助。
【CateGory Index】： P314.2
【CateGory Index】： P314.2