内蒙古阿尔山绿水碱长花岗岩锆石U——Pb 年龄、地球化学特征及构造意义

绿水碱长花岗岩锆石的LA--ICP--MS U--Pb 同位素测试结果为139. 4 ± 1. 6 Ma，表明其形成于早白垩世。地球化学特征显示绿水碱长花岗岩属于弱过铝质高钾钙碱性A2 型花岗岩，具高硅、高碱和低CaO、Fe2O3、MgO 和P2O5 特征; 轻稀土元素( LＲEE) 富集，重稀土元素( HＲEE) 相对亏损，铕具有明显的负异常; 高场强元素Zr、Hf 和大离子亲石元素Ｒb、Th、U 及K 相对富集，Ba、Nb、Ta、 Sr 和P 具明显的亏损。结合区域地质资料，认为这些碱长花岗岩的形成可能与古太平洋板块俯冲导致的加厚岩石圈拆沉后伸展环境有关。

Zircon U-Pb ages and geochemical characteristics of Lvshui alkali feldspar granites in Arshan,Inner Mongolia and their tectonic implications

Zircon U-Pb dating by LA-ICP-MS technique indicated that the Lvshui alkali feldspar granite formed in Early Cretaceous （ 139.4 ± 1.6 Ma）. The geochemistrical characteristics showed that these granites belonged to peraluminous high-k calc-alkaline A2-type granite. The alkali feldspar granites were high in silicon and alkalis, and low in CaO, Fe203 , MgO and P205. The rocks were obiviously riched in LREE, HFSEs （Zr and Hf） and LILEs （Rb, U, Th, and K） , and deplted in HREE, Ba, Nb, Ta, Sr, and P with significantly negative Eu anomaly. Combined with the regional geological data, the authors propose that the formation of Early Cretaceous alkali feldspar granitic rocks were related to a post-orogenic extensional environment induced by the delamination of lithosphere arose from subduction of the Paleo-Pacific p/ate.