内蒙赤峰地区若干主干断裂带的构造热年代学   总被引：17，自引：7，他引：17  

刘伟杨进辉  李潮峰 《岩石学报》2003,19(4):717-728

黑里河-宋三家和西拉木仑近东西向断裂的宏观和显微组构特征均指示了右行走滑剪切；小城子-八里罕北北东向断裂显示了平面上的左行剪切和剖面上的正断式剪切。根据断裂糜棱岩中长石残斑与韧性基质在粒径上的显著差异，采用逐级破碎、逐级分选的方法，逐次剔除长石残斑。从细粒韧性基质中分选出钾长石、斜长石和黑云母，进行糜棱岩矿物内部Rb—Sr等时线定年和单颗粒黑云母的激光熔化^40Ar／^39Ar定年。定年结果显示，糜棱岩化促进了手标本尺度上的同位素均一化，造成了原岩同位素时钟的重置。定年结果表明，黑里河-宋三家断裂变形的年龄为232Ma；西拉木仑断裂右行挤压走滑的年龄为165Ma。蒙古古生代岩浆弧与华北地块北缘的碰撞拼贴，以及华北-蒙古联合地块与西伯利亚板块的碰撞拼贴的远程效应。导致了上述2期变形。小城子-八里罕断裂的左行和正断式剪切的年龄介于127～117Ma，与喀喇沁核杂岩的快速隆升时期相同。壳-幔隆升促进了中下地壳的韧性化和拆离，导致了北北东向断裂的左行和正断式剪切。  相似文献   

后坪-大洛韧性剪切带初步研究   总被引：1，自引：0，他引：1  

黄家龙  林亨才 《福建地质》2003,22(4):213-220

位于政和-大埔断裂带中北段的后坪-大洛韧性剪切带，规模较大，由一系列北北东向平行状、网结状的糜棱岩带组成。是由加里东期和印支期四套运动学性质各不相同的韧性剪切系统构成，是不同期次、不同形变叠加变形的产物，是造山带中浅层位复杂构造运动的产物。  相似文献   

The~(40)Ar/~(39)Ar geochronology constraint and geological significance of mylonites in Shangyi-Chicheng fault belt on the north of North China Craton     

胡玲  宋鸿林  颜丹平  胡道功 《中国科学D辑(英文版)》2003,46(11)

The Shangyi-Chicheng fault belt extending along the south boundary of the Inner Mongolia axis on the north of the North China Craton was formed in the Middle Proterozoic. This fault has special geological significance1) in the evolution of the North China…  相似文献   

Multiple generations of pseudotachylyte in the brittle to ductile regimes, Qinling–Dabie Shan ultrahigh-pressure metamorphic complex, central China     

Aiming Lin  Zhiming Sun  Zhenyu Yang 《Island Arc》2003,12(4):423-435

Abstract Pseudotachylytes are present along the Dahezhen shear zone in the Qinling–Dabie Shan collisional orogenic belt, central China. Two types of pseudotachylyte vein are documented in the shear zone: cataclasite‐related pseudotachylyte (C‐Pt) and mylonite‐related pseudotachylyte (M‐Pt). M‐Pt is associated with mylonite‐development and is overprinted by C‐Pt. All of the quartz and most of the feldspar porphyroclasts within the M‐Pt are plastically deformed, but not in the C‐Pt. Dynamically recrystallized fine‐grained quartz and feldspar bands are oriented subparallel to the mylonite and M‐Pt foliation, and partially surround the porphyroclasts. Our results suggest that the M‐Pt formed cyclically in the ductile region at estimated conditions of 400–650°C and 400–800 MPa due to propagation of seismic fracturing associated with the thrusting‐related rapid exhumation of the ultrahigh‐pressure metamorphic complex in the brittle regime down to a greater depth than the base of the seismogenic zone. The M‐Pt and mylonite formed in the Dahezhen shear zone at estimated conditions of 400–650°C and 400–800 MPa. The coexistence of C‐Pt and M‐Pt in the same shear zone suggests that repeated seismic slips occurred in both the brittle and ductile portions of the crust during the thrusting‐related rapid exhumation of the ultrahigh‐pressure metamorphic complex.  相似文献   

High Temperature Mylonitization of Quartzofeldspathic Gneisses: Example from the Schirmacher Hills, East Antarctica     

Santanu Bose  Sudipta Sengupta 《Gondwana Research》2003,6(4):805-816

In the Schirmacher Hills, most of the ductile shearing took place under high to medium grade amphibolite facies metamorphism. The microstructure of the mylonites shows characteristic features of high temperature deformation and thus gives us an idea of deformation mechanisms of the constituent minerals at great crustal depth. The variation in microstructure of the sheared rock is partly due to heterogeneity of the intensity of strain from domain to domain, producing protomylonites, orthomylonites and ultramylonites. However, a large part of the microstructural variation has resulted from syn- to post-tectonic recrystallization and grain growth of constituent minerals. Both quartz and feldspar have deformed by crystal plastic processes with dominant grain boundary migration. The present aspect ratio of the feldspar grains is a result of various degrees of dynamic recrystallization along the grain boundary. The ratio varies between 1.5 and 2. Presence of exsolution lamellae in perthites and formation of myrmekite at the strained grains of K-feldspar suggest diffusion assisted dislocation creep. These mylonites are characterized by the presence of weakly strained or unstrained long quartz ribbons. The development of quartz ribbons with the absence of significant strain suggests grain recovery and grain growth during high temperature mylonitization. The growth of quartz ribbons took place by coalescing neighbouring grains both along and across the ribbon length. At the ultramylonite stage the fine-grained matrix of quartz and feldspar mostly accommodates the bulk strain.  相似文献   

新疆东天山红山金矿成矿时代研究   总被引：4，自引：1，他引：4       下载免费PDF全文

陈文张彦  赵海滨  韩丹  王成玉 《中国地质》2006,33(3):632-640

红山金矿区位于秋格明塔什—黄山韧性剪切带东段北缘,矿床成因研究表明,红山金矿的形成严格受该韧性剪切带控制,属于与韧性剪切带有关的糜棱岩型、超糜棱岩型矿床。花岗质糜棱岩中角闪石276.3Ma的Ar-Ar坪年龄给出了红山金矿床成矿事件的时代上限。金矿石样品中绢云母246.9Ma和246.5Ma的Ar-Ar坪年龄记录了金矿床主成矿期的时代。糜棱岩中新生白云母246.5Ma的Ar-Ar坪年龄,在误差范围内和金矿石样品中绢云母的Ar-Ar坪年龄完全一致,不仅为红山金矿床的剪切带型成因提供了进一步的佐证,也对金成矿时代给予了进一步的限定。  相似文献   

黑龙江省老柞山金矿田韧性剪切带与金成矿的关系     

李广慧  韩丽  张明海 《地质与勘探》1999,35(2):14-16

从韧性剪切带的地质产状,含金性出发,探讨了韧性剪切带与金矿之间的关系,认为,老柞山金矿的韧性剪切带形成了金矿之前,韧性剪切变形作用不仅促进了Ａｕ元素的初始活化和富集,形成了矿源层,而且还为后期构造岩浆活动的叠加提供了有利空间,金矿床肥叠加于韧性切带之上的脆性断裂控制,属于韧性剪切带金矿。  相似文献   

下庄矿田气热高温铀成矿特征及年龄研究   总被引：9，自引：3，他引：6  

徐达忠  刘林清  胡宝群 《铀矿地质》1999,15(5):266-270,278

本文报道了在下庄矿田花岗岩体接触带附近的剪切构造糜棱岩带中,存在受深色蚀变岩制约的气热高温型铀成矿,它是下庄矿田发生于晚侏罗世的一次重要铀成矿作用。文中指出了韧性剪切带及气热交代蚀变岩是铀成矿的共同控制因素,同时划分了４种气热高温矿石组合类型,对各组合电子探针分析的化学成分作了较详细介绍。文章还披露了作者所测的３个矿石晶质铀矿Ｕ－Ｐｂ同位素年龄（为１６５—１４６Ｍａ）,表明属晚侏罗世成矿。此外,对以往所划分的成矿期次提出了修改的商榷意见。  相似文献   

金厂峪 韧性剪切带对金矿形成的控制     

刘正宏 《吉林地质》1990,9(3):42-49

金厂峪韧性剪切带具有多期多阶段长期演化历史,可以划分为两期变形。早期变形是塑性变形,主要形成各种类型糜棱岩,是等化学变形。晚期变肜作用是韧脆性变形,主要形成片糜岩,是非等化学变形。在晚期变形过程中SiO_2和金等成矿元素从围岩中所出,然后迁移至低压空间沉淀成矿,表明成矿作用和晚期韧性变形作用是同时发生的。  相似文献   

阿尔金断裂剪切过程中定向生长锆石的发现及其意义—来自于显微构造和锆石内部矿物包裹体的证据   总被引：1，自引：0，他引：1  

李海兵  杨经绥等 《地质通报》2002,21(6):298-303

阿尔金断裂带中段出露一套走滑过程中形成的花岗质和角闪质糜棱岩。从糜棱岩中分选出3种类型的锆石:岩浆成因的长柱状锆石、柱状锆石和变质成因的次浑圆状锆石。这3种锆石的显微结构和构造特征以及它们内部的矿物包裹体均有所区别。其中长柱状锆石在岩石中定向排列,晶体长轴方向与拉伸线理方向一致,并且内部的所有矿物包裹体的长轴方向均与锆石的长轴方向平行,即与拉伸线理方向平行;拉曼研究表明包裹体矿物具熔融相特征;阴极发光图像中反映出这种锆石具有相对均一的内部结构。因此,该长柱状锆石是在韧性剪切过程中部分熔融环境下快速定向生长的,不仅代表了走滑剪切过程中的剪切应变方向,而且其生长年龄代表了走滑剪切的时代。  相似文献