冈底斯带门巴区晚白垩世花岗岩年代学、地球化学及构造背景  

Dating and geochemistry of the Late Cretaceous granitoids near Menba area in Gangdise Belt and their tectonic setting

作　　者：刘建兵 那晓红 张忠 王立明 

机构地区：[1]宁夏回族自治区地质调查院,银川750021 [2]黑龙江省地球物理勘察院,哈尔滨150036 [3]内蒙古第十地质矿产勘查开发院,内蒙古赤峰024005

出　　处：《世界地质》2012年第4期638-647,共10页World Geology

基　　金：国土资源部地质调查项目(200213000013)

摘　　要：门巴区晚白垩世花岗岩主要分布于冈底斯中段的扎雪、金达和桑巴附近,由黑云母钾长花岗岩、钾长花岗岩和二云母钾长花岗岩及花岗闪长岩等组成。其中花岗闪长岩SHRIMP锆石U-Pb年龄为68.8±1.6 Ma;钾长花岗岩黑云母K-Ar年龄为78.2±1.2 Ma和81.5±1.4 Ma;黑云母钾长花岗岩和二云母钾长花岗岩的黑云母K-Ar分别为90.8±1.81 Ma和91.2±1.8 Ma。岩石学和地球化学分析结果表明,S型和低Sr低Yb特征的黑云母钾长花岗岩和二云母钾长花岗岩形成于拉萨地块与羌塘地块碰撞造山过程中的地壳加厚背景;S型和总体低Sr、高Yb特征的钾长花岗岩形成于造山带晚期阶段的伸展背景;I型花岗闪长岩应是新特提斯洋俯冲作用的结果,形成于岛弧构造环境。The Late Cretaceous granitoids expose near by Sangba,Jianduo and Zaxue areas in the middle Gangdise tectonic belt.The main rock types include granodiorite,granitite,moyite and binary granite.The SHRIMP U-Pb dating on zircon from granodiorite（tw566） is 68.8±1.6 Ma.The K-Ar datings on biotite from the moyite are 78.2±1.2 Ma and 81.5±1.4 Ma.The K-Ar dating on biotite from the granitite and the binary granite are 90.8±1.8 Ma and 91.2±1.8 Ma.Research on petrology and lithogeochemistry shows the granitite and two-mica granite as the S-type granites with low Sr and low Y,resulted from the crustal thickening owing to the collision between Lasha terrane and Qiangtang terrane.The moyite is the S-type granite with low Sr and high Y,which formed in the relaxational environment after the post-collision.The granodiorite in the ＂I＂ type formed in the island-arc environment and resulted from the subduction of the Neotethys.

关 键 词：晚白垩世花岗岩 地球化学特征 年代学 构造背景 冈底斯带门巴区 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]