西藏折无地区晚白垩世二云母花岗岩地球化学及构造环境

The geochemistry and tectonic settings of two-mica granite in Zhewu area,Tibet

西藏南木林县折无地区晚白垩世二云母花岗岩KAr年龄为93.4Ma,侵入到石炭系砂岩中。二云母花岗岩中SiO2、Al2O3和K2O质量分数高,A/CNK值大于1.11,并且标准矿物计算的刚玉质量分数均大于2.6%。Rb和Th的富集程度较强,K、Ba、Ta、Nb、Ce均有不同程度的富集,Hf、Zr、Sm、Y、Yb相对亏损。轻稀土相对富集,重稀土亏损,具有明显的负铕异常,属于同碰撞花岗岩类。该区晚白垩世的二云母花岗岩是产生在陆-陆碰撞环境下的过铝质花岗岩。

The KAr age of two-mica granite in Zhewu town of Nanmulin county,Tibet is 93.4 Ma, and the granite intruded into Carboniferous sandstone. The content of SiO(2),Al(2)O(3) and K(2)O in the two-mica granite is very high, A/CNK is higher than 1.11, and the content of corundum exceeds 2.6% through CIPW standard mineral calculating. On one hand Rb and Th are much richer than others in the two-mica granite, and K(2)O,Ba,Ta,Nb and Ce are also rich, on the other hand, Hf,Zr,Sm,Y and Yb are relatively lower. LREE is relatively rich, HREE is relatively lower and Eu have clearly negative abnormity. Judged from the figure of the cause of granite coming into being, the two-mica granite belongs to syn-collision granites. It is clear that the granites are the peraluminous granites, which were produced under the condition of the continentcontinent collision.