A Thickness Gauge for the Lithosphere Based on Ce/Yb and Sm/Yb of Mantle–Derived Magmatic Rocks

作     者：WU Zhenhan Patrick J. BAROSH ZHANG Qichao WU Jiwen YANG Yan 

作者机构：Chinese Academy of Geological SciencesBeijing 100037China P.J.Barosh and Associates103 Aaron Ave.BristolRI02809USA Institute of Karst GeologyChinese Academy of Geological SciencesGuilin 541004China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2018年第92卷第6期

页      面：2120-2135页

核心收录：

学科分类：07[理学] 

基　　金：supported by the Ministry of Land and Resources of China under grant No.201211095 

主　　题：Ce/Yb and Sm/Yb ratios mantle–derived magmatic rock lithospheric thickness correlation analysis North China Craton 

摘      要：A new method for determining the partial melting depth of mantle-derived magma and lithospheric thickness in continental regions is derived from REE geochemistry. This effective technique uses variations in the Ce/Yb and Sm/Yb ratios found in mainly volcanic rocks in continental China. The ratios change with the depth of origin consistent with the correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios found in oceanic basalt. These ratios increase exponentially with the depth of origin, the lithospheric thickness, of a wide variety of Cenozoic volcanic basalt and Paleozoic kimberlite in the North China Craton, northeastern China continent and vicinity. This functional relationship with depth is shown in a plot of the ratios that forms a concordia curve, which is closely expressed by formulas using 8–degree polynomials. These provide a more accurate gage in measuring the lithospheric thickness than the traditional geophysical methods. When applied to volcanic rock of different ages it also reveals how the thickness has changed over time and thus, greatly aids the understanding of the tectonic history. Relations between the COcontent, mineral reactions and pressure in the upper asthenosphere beneath the base of the lithosphere appears to affect the proportions of REE in partial melts and brings about a close correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios in mantle–derived magmatic rock. This thickness gauge, for both continental and oceanic lithosphere, provides a new approach in analyzing the lithospheric thickness in different tectonic settings and geologic times.