广西栗木花岗岩岩石地球化学特征及其构造环境

摘要

Based on the facts that rocks have high silicon (SiO 2 =72.30%~75.45%),total alkali content is high [(Na2 O+K2 O)>7%,average=7.77%],aluminum is high (Al2 O 3 ≥14%,average=14.5 1%),ASI>1.1,CIPW norm mineral is corundum (C)2.43%~4.75%,total REE content is low (3.68×10 -6 ~1 6.48× 10 -6 ),LREE is slightly enriched (L/H is 1.71 ~2.81),and δEu value is low (0.01 ~0.21 ),it is verified that granites in Limu is a kind of leucogranite.Furthermore it can be named as corundum leucogranite.Mo-reover,according to europium anomaly and geochemical characters of REEs and trace elements,and on the basis of tectono-discrimination diagram,it is believed that granites in Limu is a product of partial melting of argillo arenaceous clastic rocks at Precambrian or Cambrian deep depth under the conditions of high pressure and low temperature in the post-collisional compressive tectonic environment.%根据岩石高硅(SiO 2=72.30%~75.45%),全碱含量高[(Na2 O + K2 O)>7%,平均值为7.77%)],高铝(Al2 O 3≥14%,平均值为14.51%),ASI >1.1,CIPW 标准矿物刚玉(C)2.43%~4.75%,稀土总量低(3.68×10-6~16.48×10-6),轻稀土弱富集(L/H 为1.71~2.81),δEu 值低(0.01~0.21)的特征,确定栗木花岗岩属淡色花岗岩,可进一步命名刚玉淡色花岗岩。同时根据岩石的铕异常、稀土元素和微量元素的地球化学特征,结合构造判别图解,笔者认为栗木花岗岩是在后碰撞的挤压构造环境下,前寒武系或寒武系深层位的泥砂质碎屑岩在相对高压低温的条件下经部分熔融的产物。