煎茶岭韧性剪切带的厘定及其地质意义  

Determination of the Ductile Shear Zones in Jianchaling and Their Geological Significance

作　　者：聂江涛[1] 魏刚锋[1] 姜修道[1] 李赛赛[1] 任金彬[1] 任华[1] 

机构地区：[1]长安大学地球科学与资源学院,西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《大地构造与成矿学》2010年第1期1-19,共19页Geotectonica et Metallogenia

基　　金：中国与亚洲重大地质问题对比研究项目(项目编号:1212010611807)

摘　　要：通过野外地质调查、室内(超)显微构造观测和构造岩石组构分析等方法厘定了煎茶岭地区北西西向和北东向两条韧性剪切带,前者出露于研究区的北部,后者出露于研究区的南部,两者交汇于煎茶岭,无论沿走向还是顺倾向均呈舒缓波状。韧性剪切带内发育糜棱岩系列、构造片岩、荚片构造、S-C面理、旋转碎斑系、A型褶皱、亚颗粒、位错弓弯、位错列、位错网等宏观和(超)显微构造特征,结合构造岩中石英光轴优选方位型式等证明两韧性剪切带呈共轭产出,至少经历了三期活动:中元古代晚期,北西西向脆韧性剪切带为压扭性右行剪切,北东向脆韧性剪切带为压扭性左行剪切,σ1≈282°∠24°,古应力值约59.1MPa;加里东期,前者为张扭性右行剪切,后者为张扭性左行剪切,σ1≈344°∠78°,古应力值约86.5MPa,超基性岩体以岩墙扩展式侵入到韧性剪切带内,预测北东向韧性剪切带深部还存在一定规模的超基性岩体,是今后寻找与超基性岩有关矿产的重要靶区;海西期,随着脆性程度进一步增加,北西西向韧脆性剪切带经历了压扭性左行剪切,北东向韧脆性剪切带经历了压扭性右行剪切,σ1≈120°∠20°,古应力值约116.3MPa,花岗斑岩体以气球膨胀式侵位。韧性剪切带对金镍矿有重要控制作用。Based on the methods of field geological survey,ultramicrostructural and microstructural observation in a laboratory and petrofabric analysis of tectonites,two ductile shear zones trending in NWW and NE in the Jianchaling area are determined.The former occur in the northern part of the study area while the latter in the southern area and they intersect each other in Jianchaling with a gentle wave-like shape in both strikes and dips.The macroscopical,ultramicrostructural and microstructural characteristics of the ductile shear zones,such as mylonite series,tectonic schist,schist beanpod-like structure,S-C foliation,rotation broken spot series,A-type folds,subparticles,dislocation bowing-out,dislocation array,dislocation net and the preferred orientation form of quartz c-axisect in the tectonites,prove that the two ductile shear zones are of conjugation,and experienced at least three periods.Namely,In the late Mesoproterozoic,the NWW brittle-ductile shear zone underwent dextral compresso-shearing while the NE sinistral compresso-shearing σ1≈282°∠24°,the paleostress is estimated at about 59.1MPa.In the Caledonian period,the former underwent dextral tension-shearing while the latter sinistral tension-shearing σ1≈344°∠78°,the paleostress is estimated at about 86.5MPa.The ultrabasic plutons intruded into the ductile shear zones by the form of dyke expansion.It is deduced that there exist a fairly large scale of ultrabasic pluton in the depths in the NE ductile shear zone,which is the essential metallogenic target area related to the ultrabasic rocks.And in the Hercynian period,with the further increase in the degree of brittleness,the NWW ductile-brittle shear zone underwent sinistral compresso-shearing while the NE dextral compresso-shearing σ1≈120°∠20°,the paleostress is estimated at about 116.3MPa.The granite porphyry was emplaced by the form of balloon expansion.The ductile shear zones play a very important role in controlling gold and nickel mineralizations in the study area.

关 键 词：北西西向韧性剪切带 北东向韧性剪切带 厘定 地质意义 煎茶岭 

分 类 号：P542[天文地球—构造地质学] P545[天文地球—地质学]