武夷山高溪和富城花岗岩体地球化学及其与铀成矿的关系   总被引：6，自引：2，他引：6  

陈迪云  章邦桐 《岩石学报》1997,13(1):71-84

从成矿地质条件分析，武夷火山铀成矿带中的主要铀矿床的共同点是都具有花岗岩基底岩石。选择富城和高溪两花岗岩体进行地球化学研究。这两个岩体均为复式岩基，其主体岩石都形成于印支晚期（高溪：２１４．６Ｍａ；富城：２０３～２２６Ｍａ）。岩体中的长石为微斜长石；黑云母为铁云母和铁叶云母。岩石化学表现为富硅、偏碱和铝过饱和的特征。微量元素Ｃｏ、Ｎｉ、Ｃｒ、Ｓｒ、Ｂａ含量和Ｓｒ／Ｂａ比值较低，Ｒｂ、Ｎｂ、Ｐｂ、Ｚｎ的含量和Ｒｂ／Ｓｒ比值高。稀土总量较高，轻稀土富集，轻、重稀土的比值高，并有强烈的铕亏损。高溪和富城两岩体的初始锶同位素组成高（分别为０．７１２３９和０．７１９８），钕同位素组成低（－６．６２～－１２．８４），这些表明高溪岩体属改造型花岗岩。两岩体中活性铀的比例高，特别是在蚀变作用中活性铀的比例增加。铅同位素追踪研究表明，在蚀变过程中岩体中的铀发生了大量的丢失。矿石铅同位素和岩体铅同位素都位于造山带的演化线附近，且矿石铅、火山岩铅、花岗岩铅及基底变质岩铅同位素组成呈线性关系，据此认为高溪和富城花岗岩体分别是形成５７０和６７２２矿床主要铀源体之一  相似文献   

Origin of composite dikes in the Gouldsboro granite, coastal Maine   总被引：3，自引：0，他引：3  

R.A. Wiebe  R. Ulrich 《Lithos》1997,40(2-4):157-178

Composite dikes, consisting of aphyric basaltic margins and phenocryst-rich rhyolitic interiors, cut the Gouldsboro granite of coastal Maine at many localities. Limited hybridization (exchange of crystals, commingling, and mixing) occurs in most of the dikes and indicates that the two magmas were contemporaneous with emplacement of rhyolitic magma following closely in time the initial emplacement of the basaltic dike. Petrographic characteristics and geochemistry indicate that the source of the rhyolite was resident magma in the Gouldsboro granite magma chamber. The composite dikes formed when basaltic dikes ruptured the Gouldsboro magma chamber, permitting partly crystallized magma from the margin of the chamber to flow outward into the center of the basaltic dikes. Field relations of similar composite dikes in other areas (e.g., Iceland, Scotland) are consistent with this model. A second type of composite dike (silicic margins with chilled basaltic pillows) commonly cuts mafic intrusions along the Maine coast and probably formed when a granitic dike ruptured an established chamber of mafic magma, permitting resident mafic magma to collapse downward into the still Liquid granitic dike. Most composite dikes have probably formed when a magma chamber was disrupted by a dike of contrasting magma rather than by tapping a stratified magma chamber.  相似文献   

江南隆起东端伸展构造的识别及其意义   总被引：2，自引：0，他引：2  

张开均 《安徽地质》1997,(2)

通过对屯溪流塘盆地典型伸展堆叠构造几何学和运动学的解剖，以及对其它几个伸展构造实例的分析，指出伸展构造在江南隆起的存在，它们的形成主要是重力作用的产物，遍及中、新生代。这种特征构造的解剖有助于深化认识江南隆起的构造特点和演化历史。  相似文献   

吉林省桦甸地区太古宙花岗质片麻岩的侵位与变形研究     

周永胜  林强 《吉林地质》1997,16(1):33-41

根据岩石组合，分布，接触，包裹关系以及结构和构造，吉林省桦甸地区太古宙花岗质林岩为角闪英云闪长质片麻岩类和黑云母花岗闪长质片麻岩类，角闪英云闪长质片麻岩类为变形前侵入体，黑云母花岗闪长质片麻岩类为同变形侵入体，两类花岗质片麻岩的侵位是晚太古宙近东西向构造变形相伴生的岩浆活动事件。  相似文献   

川西北倒三角形断块东部区域强震带形成机制与地震活动特征     

蒋良文  王士天  李渝生  王运生 《地球科学进展》2004,(Z1)

川西北倒三角形断块东部区域地处青藏高原东部边缘地带,地跨川西北高原及其与四川盆地过渡带的高山峡谷区,属我国著名的南北向地震带的中段,因其特定的大地构造环境和强烈的现代地壳构造运动,导致其在强大的近东西向构造应力场的驱动和平卧“A”字型控震构造体系的控制下,沿两侧边界断裂向东强力楔入,于“构造急剧收口带”之西侧形成了一个近SN向地跨三大构造单元的强震带,强震沿该带有规律的往返迁移和重复发生,且地震活动强弱具有较明显的分形特征。  相似文献   

内蒙古西部甜水井地区中二叠世A型花岗岩   总被引：8，自引：0，他引：8  

贺锋  许立权  苏宏伟  李新仁 《西北地质》2004,37(3):7-14

内蒙古北山甜水井地区龙脊山—神蛇岭岩体，总体呈北西向长椭圆状，面积大于100km^2。按岩石谱系单位划分为一单元含斑细粒黑云母二长花岗岩、二单元含斑中细粒黑云母二长花岗岩和三单元中细粒花岗岩,归并为一龙脊山序列。岩石富硅碱，ALK在7．23％～8．37％．AKI小于1,A／CNK=1．01～1．07；OX较高．在0．47～0．83。相对富集大离子亲石元素、轻稀土元素，亏损Ba、Nb、Sr、Zr、Ti。稀土配分曲线呈现显著的“V”字型。副矿物组合为Mt-Ap-Zi型。由早单元到晚单元。向酸碱性增强方向演化，显示深源浅成铝质A型(A2型)花岗岩特征。各类构造环境判别图解投点．具造山后或后造山特征。同位素测年(锆石U-Pb法)为267．1Ma。反映本区中二叠世碰撞造山作用的存在。中二叠晚期已转入稳定的陆内发展环境。  相似文献   

大别山沙村中生代A型花岗岩和基性岩的源区演化关系   总被引：4，自引：5，他引：4  

谢智  郑永飞闫峻　钱卉 《岩石学报》2004,20(5):1175-1184

A型花岗岩的成因虽存在不同的认识模式,但对大别山沙村A型花岗岩的岩石化学和地球化学研究结果表明,其物质源自大陆岩石圈地幔的部分熔融,含有古老地壳信息。结合被侵入基性岩的地球化学和年代学资料,推测大别造山带中生代岩石圈地幔的地球化学性质与下扬子地幔相似。花岗岩中锆石SHRIMP法U-Pb年龄为119.0±3.2Ma,说明其岩浆侵位于早白垩世,与邻近的基性岩侵位时间相近但稍晚。在三叠纪因大陆俯冲碰撞增厚的岩石圈在早白垩世被拉张减薄,含有古老地壳成分的扬子陆下岩石圈地幔及其上覆下地壳发生部分熔融,形成了不同成分的碰撞后岩浆岩。其中部分基性岩浆分异结晶成为辉长岩,而A型花岗岩可能是同一地幔源区物质小比例部分熔融后分异结晶的产物。  相似文献   

花岗岩研究进展 ———ISMA花岗岩类分类综述   总被引：4，自引：0，他引：4       下载免费PDF全文

陈建林  郭原生  付善明 《甘肃地质》2004,13(1):67-72

本文在论述花岗岩主要分类的基础上论述了ISMA花岗岩类的基本含义,讨论了人们在以后应用和推广ISMA这类花岗岩分类方案时存在的一些问题,指出了ISMA花岗岩类本身在分类过程中存在的一些基本问题。  相似文献   

Flexural and gravity modelling of the Mérida Andes and Barinas–Apure Basin, Western Venezuela     

Luis Chacín  María I. Jcome  Carlos Izarra 《Tectonophysics》2005,405(1-4):155-167

The kinematic evolution of the Barinas–Apure Basin and the southern Mérida Andes from Lower Miocene to the Present is numerically modelled using flexural isostatic theory and geophysical and geological data. Two published regional transects are used to build up a reference section, which is then used to constrain important parameters (e.g. shortenings and sedimentary thicknesses) for the flexural modelling. To control the location of the main fault system in the flexural model earthquake information is also used. The estimated flexural elastic thickness of the South American lithosphere beneath the Barinas–Apure Basin and the Mérida Andes Range is 25 km. The value for the final total shortening is 60 km. The flexural isostatic model shows that the Andean uplift has caused the South American lithosphere subsidence and the development of the Barinas–Apure Basin.In addition, gravity modelling was used to understand deep crustal features that could not be predicted by flexural theory. Consequently, the best-fit flexural model is used to build a gravity model across the Mérida Andes and the Barinas–Apure Basin preserving the best-controlled structural features from the flexural modelling (e.g. basin wavelength and depth) and slightly changing the main bodies density values and deep crustal structures. The final gravity model is intended to be representative of the major features affecting the gravity field in the study area. The predicted morphology in the lower crustal level of the final gravity model favours the hypothesis of a present delamination or megathrust of the Maracaibo crust over the South American Shield. This process would use the Conrad discontinuity as a main detachment surface within an incipient NW dipping continental subduction.  相似文献   

Microcrack networks in granite affected by a fault zone: Visualization by confocal laser scanning microscopy     

Celia T. Onishi  Ichiko Shimizu   《Journal of Structural Geology》2005,27(12):170

Microcracks in the Cretaceous Ryoke-type granite in Japan were investigated by using deep drilling core samples collected in the Mizunami Underground Research Project of the Japan Nuclear Cycle Development Institute (JNC). The granite body suffered brittle deformation associated with Tertiary thrust movement. Based on core-scale and microscopic deformation features, the drill core from a depth of 300 to 700 m is divided into four domains, i.e. (A) undeformed granite, (B) granite intruded by cataclastic seams, (C) fractured granite in the fault damage zone, and (D) foliated cataclasite at the fault center. To characterize microcrack geometries in each domain, we employed the impregnation method using a low-viscous acrylic resin doped with fluorescent agents and captured the microcrack images by confocal laser scanning microscopy (CLSM). The CLSM image in the fault damage zone revealed anisotropic development of microcrack networks related to the fault movement. Both CLSM observation and porosity measurements reveal a drastic increase of micro-pores in the foliated cataclasite, possibly caused by fragmentation, and granulation and crack sealing in the fault zone.  相似文献