| 1 | Geochemistry and petrogenesis of Jurassic high Sr/low Y granitoids in eastern China: Constrains on crustal thickness显示文摘The Jurassic high Sr/low Y granitoids in eastern China are characterized by high Sr/Y (27-166) and La/Yb (14-66) ratios, low abundance in Y (6-21μg/g) and Yb (0.5-2.0μg/g), comparable with those of adakites defined by Defant et al. Thus, they were recently considered as adakitic rocks by some researchers. Compared with the typical adakites in circum-Pacific margins, however, these high Sr/low Y granitoids have higher K2O (-3.5%) but lower A12O3 (-16.0%) as well as lower Mg#(-38) and δSrN (-1.23) values. Furthermore, they show relatively flat HREE patterns with Y/Yb values of -10 close to the chondritic value. These geochemical characteristics indicate a residue mineral assemblage of hornblende, garnet and plagioclase for these high Sr/low Y granitoids melt. Thus, they were generated by partial melting at 9-13 kbar (30-45 km in depth), similar to the Archaean high-Al TTG rather than the modern adakites. Generation of these high Sr/low Y granitoids cannot be considered as evidence for a thickened | Ge, XY Li, XH Chen, ZG Li, WP | 2002 | Chinese Science Bulletin2002，47，11： | 51 |
您所在的机构暂未开通此部分的功能，请联系管理员