松潘-甘孜地块丹巴二叠纪玄武岩的主、微量元素和Sr-Nd同位素研究：岩石成因与构造意义

松潘-甘孜地块的丹巴二叠纪玄武岩（大石包组）具有较高的TiO2含量（〉2％）和高的Ti／Y比值（平均519），显示LREE富集、HREE亏损的右倾型稀土配分型式（（La／Yb）N=4．2～13．6），εNd（t）=-0．33～2．70，具有洋岛玄武岩（OIB）地球化学特征，形成于大陆板内环境。其源区来自原始地幔始于石榴子石稳定区的低程度部分熔融，岩浆上升过程中有来自地壳物质的加入，因而其不相容元素比值如Zr／Nb（4．41～13．09）、La／Nb（1．03～1．80）和Th／La（0．08～0．18）等，以及初始的87^Sr/86^Sr比值（0．706008～0．707257）均表现出不同程度的富集特征，岩浆演化早期经历了以辉石、橄榄石为主的分离结晶作用。该套玄武岩的元素-同位素地球化学特征和源区性质类似于峨眉山溢流玄武岩的高钛（HT）系列，因此认为其是峨眉山地幔柱活动的产物，属于峨眉山大火成岩省（ELIP）的一部分。松潘-甘孜地块和扬子西缘晚古生代以前地层的可比性以及峨眉山溢流玄武岩的分布特征显示，松潘-甘孜洋盆伴随着扬子克拉通的裂解而打开，并且可能都与峨眉山地幔柱有关，是地幔柱活动的浅部地质响应。

U-Pb, Rb-Sr isotopic chronology of Jinning granites in the Songpan-Ganze Orogenic Belt and its tectonic significances

A series of Jinning granites are located in the eastern margin of the main part of the Songpan-Ganze Orogenic Belt. The research is focused on Gezong and Donggu granites in the Danba area. From the viewpoint of isotopic chronology, geochemistry and tectonic geology, their formation ages, origins and geneses of source materials, and the influences of Himalayan tectonic thermal events are discussed- It is suggested that they were the products of Jinning tectono-magmatism. The source materials were the poorly matured volcano-sedimentary rocks formed in the middle-late period of the middld-Proterozoic. They represent in fact the basement of the old Yangtze Block. The late Proterozoic erogenic belt of the entire western margin of the Yangtze Block, including the Danba area, should be the key part of the old Yangtze Block.