论文部分内容阅读
为了对古亚洲洋的演化提供新的资料,对内蒙中部乌拉特中旗图古日格角闪石岩进行了角闪石电子探针分析、锆石LAICP-MS U-Pb年代学,锆石Hf同位素和岩石地球化学分析,以确定其岩石成因及其地球动力学背景.两件测年样品加权平均年龄分别为273.5±1.3Ma(MSWD=0.48)和274.4±4.3Ma(MSWD=0.041),属于早二叠世晚期.角闪石岩贫SiO_2、Na_2O、K_2O,富Al_2O_3、TFe_2O_3、MgO和CaO,Mg~#值为46.95~63.53,M/F比值为0.87~1.72;稀土元素配分曲线为右倾型,和原始地幔相比明显富集大离子亲石元素(Rb、Ba、K),而高场强元素Nb、Ta和Ti相对亏损,Th、U同样显示出相对亏损.电子探针分析结果表明角闪石岩中角闪石属于钙质角闪石,具有幔源角闪石的特点.角闪石岩中锆石的ε_(Hf)(t)值为-0.3~8.5,锆石Hf单阶段模式年龄(t_(DM1))为580~920Ma.研究表明其源区主要为亏损地幔,上涌过程中与富集岩石圈地幔发生相互作用,形成具有富集地幔特征岩浆.结合区域地质演化,认为角闪石岩形成于古亚洲洋闭合后的伸展环境,可能与俯冲板片的断离有关.
In order to provide new data for the evolution of the Paleo-Asian Ocean, an amphibole-type electronic probe analysis of the Tugujig hornblende from Wulatezhongqi, Central Inner Mongolia, zircon LAICP-MS U-Pb chronology and zircon Hf isotopic and lithogeochemical analysis to determine the origin of rocks and their geodynamic background.The weighted average ages of two samples were 273.5 ± 1.3Ma (MSWD = 0.48) and 274.4 ± 4.3Ma (MSWD = 0.041) respectively, Belonging to the late Early Permian. The amphiboles are depleted in SiO_2, Na_2O, K_2O, Al_2O_3, TFe_2O_3, MgO and CaO with the Mg ~ # value of 46.95 ~ 63.53 and the M / F ratio of 0.87 ~ 1.72. (Rb, Ba, K), whereas the high-field elements Nb, Ta and Ti are relatively depleted, while Th and U also show a relative loss. Compared with the original mantle, electron microprobe analysis The results show that hornblende belongs to calcareous hornblende, which has the characteristics of mantle source amphibole. The ε_ (Hf) (t) values of zircon in amphibole are -0.3 ~ 8.5, Hf single-stage model age (t_ (DM1)) is 580 ~ 920Ma. The study shows that the source region is mainly depleted mantle, and during the upwelling, it interacts with the enriched lithospheric mantle to form There enriched mantle magma. Geological evolution binding region that is formed on the extension Hornblendite Ancient Asian ocean environment after closure, may be related to the subducting slab from breaking.