三道溜河地区太古宙岩浆－构造事件   总被引：3，自引：0，他引：3  

刘大瞻  刘跃文 《吉林地质》1994,(3)

三道溜河地区处于中朝准地台北东缘，北西起自著名的夹皮沟金矿，南东至四道砬子河，太古宇出露广泛。笔者在此进行１：５万区调时，共发现了六次岩浆－构造事件，由老至新依次为：７８７角闪辉石岩、岭东片麻岩、大朝阳沟斜长角闪岩、三道溜河ＴＴＧ岩组、唐胡店沟二长花岗岩、五道砬子河变辉长辉绿岩（发生在元古宙早期，在时空上与太古宇关系密切）。上述事件，表现为基性岩类与酸性岩类交替出现。基性岩事件依次为超基性岩－基性岩－偏碱性基性岩，稀土元素总量由高至低，微量元素Ｂａ、Ｍｎ、Ｚｒ递增，Ｐｂ、Ｚｎ递减。酸性岩事件依次为中酸性岩－酸性岩－偏碱性酸性岩，稀土元素的Ｌａ／Ｌｕ、ΣＣｅ／ΣＹ由低到高，总量变化不大，微量元素Ｃｏ、Ｃｒ、Ｎｉ、Ｃｕ递减。本区的构造运动与岩浆侵入活动相辅相成，古穹窿构造及北西向韧性剪切带控制了Ａｕ、Ａｇ、Ｃｕ等矿产的展布。  相似文献   

苏北榴辉岩的稀土元素地球化学及其成因讨论   总被引：13，自引：0，他引：13  

谭绪荣  赵云龙 《地质论评》1995,41(5):401-408

江苏北部的榴辉岩出露于东海群变质岩系中，榴辉岩的产状是：１）呈似层状或透镜状产于东海群片麻岩中；２）呈不规则团块状产于超镁铁岩中，或与超镁铁岩伴生。全岩分析表明，前者相当橄榄拉斑玄琥岩或石英拉斑玄武岩，后者相当橄榄玄武岩或橄榄拉斑玄武岩。  相似文献   

冀东早太古岩石Sm-Nd同位素年龄测定   总被引：6，自引：0，他引：6       下载免费PDF全文

乔广生  王凯怡  郭起凤  张桂存 《地质科学》1987,(1):86-92

曹庄表壳斜长角闪岩和变沉积物形成的片麻岩的Sm-Nd全岩等时线资料分别得到3495±19Ma和3561±15Ma的Sm-Nd等时线年龄。该年龄被解释为是曹庄表壳岩形成的年龄。  相似文献   

应用~(40)Ar/~(39)Ar定年技术研究清原花岗岩-绿岩地体的形成时代   总被引：8，自引：1，他引：8  

王松山  胡世玲  翟明国  桑海清  裘冀 《岩石学报》1987,3(4)

辽宁清原绿岩地层自下而上分为榆树底组、红透山组和南天门组。小莱河铁矿区榆树底组斜长角闪岩岩石化学性质和稀土元素分布曲线表明,该岩石的原岩属太古代亏损型(DAT)拉斑玄武岩。此斜长角闪岩中的角闪石的两个~(40)Ar/~(39)Ar年龄谱给出该岩石的变质作用发生在29.9亿年。清原绿岩地层形成时代可能在30亿年或稍早一些。全球范围绿岩地层的年龄是35—19亿年,峰值是27亿年.清原绿岩地层的早期形成年龄则大于全球绿岩的峰值年龄。  相似文献   

Deformation and metamorphism in the Bard area of the Sesia Lanzo Zone, Western Alps, during subduction and uplift   总被引：2，自引：0，他引：2  

P. F. WILLIAMS  R. COMPAGNONI 《Journal of Metamorphic Geology》1983,1(2):117-140

The structure, microstructure and petrology of a small area close to the village of Bard in Val d'Aosta (Italy) has been studied in detail. The area lies across the contact between the Gneiss Minuti (GM) and the Eclogitic Micaschist (EMS) Complexes of the Lower element of the Sesia portion of the Sesia-Lanzo Zone (Western Alps). Both complexes have undergone high-pressure metamorphism, but the metamorphic assemblages indicate a sudden increase in pressure in going across the contact from the GM to the EMS. Therefore, we interpret the contact as a thrust dividing the lower element of the Sesia into two sub-elements. This interpretation is supported by structural evidence.
The early Alpine (90-70 Ma) metamorphic history is best preserved in the EMS and is one of increasing pressure associated with thrusting. The maximum P/T recorded in the EMS is >1500 MPa (>15kbar) and 550°C and in the GM is < 1500-1300 MPa (< 15-13 kbar) and 500-550°C. We suggest that the rocks were probably in an active Benioff zone during this time.
From then on the histories of the GM and EMS are the same. Deformation continued and the thrust and thrust slices were folded during decreasing pressure. We interpret the first postthrusting deformation in terms of uplift associated with continued shortening of the crust and underplating after the Benioff zone had become inactive and a new Benioff zone had developed further to the north-west.
A still later deformation and the Lepontine metamorphism (38 Ma) are related to continued uplift. Much of this deformation is characterized by structures indicative of vertical shortening and lateral spreading as the mountains rose above the general level of the surface.  相似文献   

Principal stages in evolution of Precambrian organic world: Communication 1. Archean and Early Proterozoic     

V. N. Sergeev  M. A. Semikhatov  M. A. Fedonkin  A. F. Veis  N. G. Vorob’eva 《Stratigraphy and Geological Correlation》2007,15(2):141-160

Expounded in this work are the results of critical consideration of published and original data on biologic nature and appearance chronology of different groups of Archean and Lower Proterozoic (3.5–1.65 Ga) paleontological remains known from geological record. Conclusions are substantiated by morphological analysis of structurally preserved microfossils, their facies distribution, and by inferable genesis and principal evolutionary trends of Archean stromatolites. A special attention is paid to variations of organic and carbonate carbon isotope composition in sedimentary successions with paleontological remains and to recent information about discovered, most ancient biomarkers of large groups of organic world. As a result of this approach, a detailed model of Precambrian organic world evolution is suggested.  相似文献   

Subduction of Continental Crust in the Early Palaeozoic North Qaidam Ultrahigh-Pressure Metamorphic Belt, NW China:Evidence from the Discovery of Coesite in the Belt   总被引：3，自引：0，他引：3  

YANG Jingsui  XU Zhiqin  SONG Shuguang  ZHANG Jianxin  WU Cailai  SHI Rendeng  LI Haibing  Maurice BRUNEL  Paul TAPPONNIER Institute of Geology  Chinese Academy of Geological Science  Baiwanzhuang Rd.  Beijing  China Department of Earth Sciences  University of Montpellier II  Montpellier  France Institut de Physique du Globe  Paris Cedex  France 《《地质学报》英文版》2002,76(1):63-68

Coesite was discovered as inclusions in zircon separates from pelitic gneiss associated with a large eclogite body in the North Qaidam ultrahigh-pressure (UHP) terrane. Some graphite inclusions were also found. This finding suggested the occurrence of in-situ UHP metamorphism and that the terrane was most likely recrystallized at pressures below the diamond stability field. It supported other previous indirect UHP evidence, such as polycrystalline quartz inclusions in eclogitic garnet, quartz lamellae in omphacite and P-T estimates for both eclogite and garnet peridotite. The U-Pb and Sm-Nd ages of the North Qaidam eclogite indicated that subduction of continental crust occurred in the Early Palaeozoic, which probably recorded a collision between the Sino-Korean and Yangtze plates.  相似文献   

胶南榴辉岩矿物氧同位素平衡及其Sm-Nd年代学制约   总被引：2，自引：4，他引：2  

郑永飞  王峥嵘  李曙光  李龙 《地球化学》2001,30(1):66-78

对苏鲁地体中的胶南榴辉岩进行了矿物氧同位素分析，并与同一手标本矿物的Sm-Nd内部等时线定年和Nd-Sr同位素分布进行了对比。研究表明，石榴子石与绿辉石之间的氧同位素平衡与否能够对矿物Sm-Nd同位素体系的平衡状况和内部等时线定年结果的有效性给予直接制约。合理的石榴子石＋绿辉石Sm-Nd内部等时线年龄产于两矿物之间达到并在峰变质条件下保持氧同位素平衡的样品中，而两矿物之间处于氧同位素不平衡的样品不能给出正确的Sm-Nd内部等时线年龄。同一矿物在手标本尺度出现显著的O-Nd-Sr同位素不均一性，据此对这些元素在石榴子石和绿辉石中的扩散速率顺序进行了估计，不仅得到了与实验扩散系数相吻合的结果，而且由此估计出在峰变质条件下达到矿物内部同位素均一化所需要的时间应大于10Ma。  相似文献   

大别山碧溪岭地区超高压变质岩构造分析   总被引：7，自引：1，他引：7  

索书田  钟增球等 《地学前缘》2001,8(2):385-394

大比例尺 (1∶10 0 0 0 )构造制图及构造分析表明 ,碧溪岭地区超高压变质岩石含有丰富的构造演化历史记录。同碰撞或挤压组构只保留于榴辉岩及其它超高压变质岩透镜体内部 ,表现为高角度网络状超高压剪切带与弱应变透镜体域规律组合格式。前者由面理或糜棱岩化榴辉岩组成 ,后者由块状榴辉岩及石榴橄榄岩组成。碰撞期后伸展构造表现为区域性的假单斜状 ,内部呈低缓角度的网络状强应变带及所环绕的透镜状弱应变域组合格式 ,强应变带的岩石为由榴辉岩退变成的角闪岩相高压片麻岩及部分熔融形成的含榴花岗岩 ,透镜状弱应变域的岩石为弱角闪相改造的榴辉岩及石榴橄榄岩。不同尺度上同碰撞或挤压组构及碰撞期后伸展组构所显示的这种残斑基质流变学结构样式 ,虽然与先期原岩成分、结构、流变学的不均一性有关 ,但主要是多期递进应变分解作用的结果 ,支持榴辉岩“原地”成因模式。依据构造学证据和可利用的岩石学及同位素年代学资料 ,分析了超高压变质岩石的形成及折返过程 ,指出碧溪岭地区超高压变质岩石是在 2 45～ 2 10Ma形成的 ,碰撞期后伸展作用主要发生在 2 0 0～ 170Ma。在超高压变质岩石向地壳表层折返过程中 ,张扭作用可能有重要功能 ,不支持碧溪岭地区遭受过多期超高压变质作用的推论。  相似文献   

柴达木盆地北缘都兰地区榴辉岩中透长石＋石英包裹体：超高压变质作用的证据   总被引：30，自引：4，他引：30       下载免费PDF全文

宋述光  杨经绥 《地质学报》2001,75(2):180-185

近年来在祁连地体与紫达木地块之间大柴旦－－都兰北一线确定出一条榴辉岩带。在此带东端北部地区野马滩一带榴辉岩中，我们发现产在石榴子石内部由透长石和多晶石英（柯石英假像）构成的包裹体。包裹体在内部结构特征及周围的状裂纹反映早期超高压变质相特征，据此，推测柴达木盆地北缘榴辉岩带可能是一形成深度超过80km的超高压变质带。  相似文献