青藏高原北部发现印支运动的新证据——来自同构造花岗细晶岩脉的响应  

New evidence of Indosinian movement in northern Tibetan Plateau:The response of the syntectonic granite aplite vein

作　　者：白国典[1] 何凯[1] 王艳慧[1] 琚根社 杜保峰[1] 王坤 

机构地区：[1]河南省地质调查院,河南郑州450007 [2]河南省地质科学研究所,河南郑州450007

出　　处：《岩石矿物学杂志》2018年第1期87-98,共12页Acta Petrologica et Mineralogica

基　　金：中国地质调查局区域地质调查项目(12120113033018)~~

摘　　要：在青藏高原北部昆仑山口-甘德断裂与巴颜喀拉山中央断裂之间发育延伸超过100 km的呈雁列排列的花岗细晶岩脉带,这些花岗细晶岩脉走向多为北西向(118°),少量呈南北向(2°)。通过对其宏、微观特征分析研究,并结合在这两组花岗细晶岩脉中分别采获的224.7±0.64 Ma(南北向)与220.5±1.1 Ma(北西向)的锆石LA-ICP-MS U-Pb同位素年龄数据,指出这些花岗细晶岩脉是印支运动的产物,是早印支期可可西里-巴颜喀拉地块向东昆仑地块斜向俯冲过程中,岩浆沿着昆仑山口-甘德北西向冲掩断层下盘(南盘)形成的北西向与南北向两组"X"型共轭剪节理贯入形成的同构造花岗细晶岩脉。两组"X"型共轭剪节理的展布方向揭示了印支运动的主压应力方向,即NNW-SSE向;北西向雁列排列的节理反映其受右行走滑作用控制的特点;花岗细晶岩脉形成的最早时间(224.7±0.64 Ma)代表了这次俯冲走滑事件的时间,也即昆仑山口-甘德断裂的形成时间。The row echelon granite aplite veined belt extending over one hundred kilometers are developed be- tween the Kunlun Mountain Pass-Gander fault and the Bayan Haran central fault in northern Tibetan Plateau, and most of them are NW-trending, with a few being SN-trending. Based on an analysis of the macroscopic and microscopic characteristics of the row echelon granite aplite veins, as well as the LA-ICP-MS zircon U-Pb dating data for the SN-trending（224.7 ± 0.64 Ma） and NW-trending（220.5 ± 1.1 Ma） granite aplite veins, it is con- sidered that the granite aplite veins are the products of Indosinian Movement, and they were formed in the oblique subduction of the Hoh Xii -Bayan Hat terrane beneath the East Kunlun terrane in early Indosinian. The synteetonic granite aplite veins were injected along the ＂X＂ conjugate shear joints in the NW（118°） and the SN （2°） direction in the footwall （south section） of the Kunlun Mountain Pass-Gander overthrust fault. The principal compressive stress direction is revealed by the distribution direction of two groups of ＂X＂ type conjugate shear joints, which is NW（118°） to the SN（2°）. The left order row echelon joints suggest that they are controlled by dextral strike-slip. The earliest formation time of granite aplite veins（224.7 ± 0.64 Ma）represents the time of subduction and strike-slip event, which is also the formation time of the Kunlun Mountain Pass-Gander fault.

关 键 词：青藏高原北部 细晶花岗岩脉带 雁列 同构造 印支运动 

分 类 号：P588[天文地球—岩石学] I21[天文地球—地质学]