内蒙古维拉斯托矿区花岗岩类地球化学特征及其构造意义

维拉斯托铜多金属矿床是近年来在大兴安岭发现的大型银铜多金属矿床，为了深入讨论维拉斯托矿区花岗岩类的大地构造环境及其形成的动力学背景，通过系统观察和分析，讨论了维拉斯托矿区钻孔内出露的黑云母花岗岩、黑云母二长花岗岩以及石英闪长岩的岩石学及地球化学特征。黑云母花岗岩及黑云母二长花岗岩具高硅特征，A/NCK平均值为1.07，里特曼指数小于3.3，属于钙碱性系列；稀土总量较高，轻重稀土元素分馏强烈，中等Eu负异常；(⁸⁷Sr/⁸⁶Sr)t值为0.705 93~0.710 75，ε_Nd(t)值为-4.45~-0.63，具有高分异I型花岗岩特征。石英闪长岩的SiO2含量中等，准铝质，高镁(3.12%~7.58%)，高Cr、Ni；稀土总量较低，轻重稀土元素分馏不明显，弱Eu负异常；(⁸⁷Sr/⁸⁶Sr)t值0.705 05~0.707 68，ε_Nd(t)值在-0.88 ~1.04，具有赞岐岩的元素组成特点。黑云母花岗岩及黑云母二长花岗岩主要来源于年轻陆壳的部分熔融，上侵过程经历较强烈的分异作用；石英闪长岩来源于俯冲流体/熔体或残余洋壳部分熔融对岩石圈地幔改造后的产物，岩浆演化后期并未经历强烈的地壳混染及分异作用。综合研究认为：维拉斯托矿区花岗岩类侵位于晚石炭世，形成于后碰撞环境。兴蒙造山带内大量出露晚石炭世-早二叠世的钙碱性高分异I型花岗岩及A型花岗岩，同时大量沉积学及地层古生物的证据均显示兴蒙造山带该时期已经进入陆内演化阶段。

Geochemistry of Granitoid Rocks of Weilasituo Deposit,Inner Mongolia and Its Tectonic Significance

Weilasituo Cu polymetal deposit is located in the west of middle-southern metallogenic belts in Great Xing’an Mountains of Inner Mongolia. In order to constrain the forming tectonic setting of the deposit, this paper analyses the major and trace elements and Sr-Nd-Pb isotopic compositions of the granitoid rocks. The granitoid rocks are composed of granites, monzonitic granites and diorites, and these granitoid rocks are calc-alkali rocks. The granites and monzonitic granites are rich in SiO₂, and characterized by high REE, middle negative Eu, relatively lower partition of HREE, strongly enriched in LILE, and depleted in HFSE. The (⁸⁷Sr/⁸⁶Sr)t (0.705 93-0.710 75) and ε_Nd(t) (-4.45--0.63) values suggest that the rocks are highly fractionated I-type granites. The primary magma for granitic rocks could be mainly derived from partial melting of the deep crust, which may be related to Xilingele complex. The diorites are rich in Mg，Cr，Ni, slightly negative Eu, with geochemical features of analogous to sanukite. The results indicated that the magma was derived from enriched mantle metasomatized by slab-derived fluids or melts. By combining with comprehensively analyses of the tectonic settings, we suggest that the Weilasituo granitoid rocks were formed in a post-collisional tectonics