湘东茶陵地区老山坳剪切带特征及其与湘东钨矿的关系  

Geological characteristics of the Laoshan'ao shear zone and its relationship with the Xiangdong tungsten deposit,Chaling,eastern Hunan Province

作　　者：宋超[1] 卫巍[1] 侯泉林[1] 刘庆[1] 张宏远[2] 伍式崇 朱浩峰[3] 李晖[3] 

机构地区：[1]中国科学院计算地球动力学重点实验室,中国科学院大学地球科学学院,北京100049 [2]中国地质大学地球科学与资源学院,北京100083 [3]湖南省地质矿产勘查开发局四一六队,株洲412007

出　　处：《岩石学报》2016年第5期1571-1580,共10页Acta Petrologica Sinica

基　　金：国土资源部公益项目(201211024-04);国家自然科学基金项目(41502215)联合资助

摘　　要：湘东茶陵地区老山坳剪切带及其与湘东钨矿的关系是长期以来备受关注且颇具争议的问题。其争议主要表现为:(1)老山坳剪切带(断层)的性质(逆断层、正断层,还是走滑断层)及其发育机理;(2)老山坳剪切带对湘东钨矿的成矿是促进作用还是破坏作用。本文对老山坳剪切带以及湘东钨矿进行了系统地观察和测量,采用宏观、微观构造研究和矿脉统计相结合的方法进行了综合分析。结果表明,老山坳剪切带的活动主要分为两期:早期主要表现为向SE方向的伸展拆离作用,且可能与晚侏罗世八团岩体侵位密切相关,形成了透入性的强烈脆、韧性变形,特别是在糜棱岩中,由于高压流体的作用造成了一系列同期节理(R和R’节理)发育,为石英脉型钨锡矿床的形成提供了条件;后期,大致在晚白垩世及之后老山坳剪切带表现为向NW方向的逆冲作用,致使上盘(主动盘)的钨锡矿脉被推至浅部。因此,我们认为晚侏罗世八团岩体的侵位作用与老山坳剪切带的伸展拆离作用共同控制了湘东钨矿的形成。韧性剪切带中,由于高压流体作用引起局部应变速率增加,同时降低岩石强度而发生脆性破裂(如T节理,R和R’节理),而且按照破裂准则发生和扩展,该过程为成矿元素析出成矿提供了条件,这可能是剪切带成矿的重要方式之一。The characteristics of the Laoshan＇ao shear zone and its relationship with the Xiangdong tungsten deposit are longstanding controversial issues. The disputes exist as follows：（ 1） whether the Laoshan＇ao shear zone is a thrust fault,a normal fault or a strike-slip fault and what is its development mechanism;（ 2） what is the relationship between the Laoshan＇ao shear zone and the mineralization of the Xiangdong tungsten deposit,it is promoting or damaging？ In order to answer these two questions,systematical macro and micro-structures analyses were conducted along the Laoshan＇ao shear zone and the Xiangdong tungsten deposit in this study.Two stage events are defined on the base of these structural observations： the first extensional detachment with a top-to-the-SE shearing coeval with the emplacement of the Batuan granitic pluton during the Late Jurassic,forming the extensive and pervasive brittle and ductile deformation. In the shear zone,the development of a serials of R and R＇joints,which are facilitated by the activities of highpressure fluid,provide the accommodation for the quartz vein type tungsten deposit; and then in the Late Cretaceous or later,the Laoshan＇ao shear zone is featured by the NW-thrusting motion,resulting in exhumation of the hanging wall with its the ore veins to the shallow depth. We suggest that the emplacement of the Batuan pluton in the Late Jurassic and the development of the Laoshan＇ao shear zone jointly facilitated the formation of the Xiangdong tungsten deposit. This study provide us a vivid example of structure controlled ore forming process in which the high-pressure fluid caused increasing local strain and reducing rock strength lead to the development of serials of brittle fractures（ e. g. T joint,R and R＇joints） in the shear zone,there factures finally provides the accomodation for the ore-fluid precipitation and mineralization.

关 键 词：湘东钨矿 老山坳剪切带 八团岩体 成矿作用 晚中生代 

分 类 号：P618.51[天文地球—矿床学]