南天山榆树沟麻粒岩相构造岩研究   总被引：11，自引：4，他引：7  

王居里  王润三 《岩石学报》1999,15(4):539-547

榆树沟麻粒岩相构造岩宏观上呈糜棱岩带和糜棱岩化带产出,发育强烈流变叶理;微观上主要造岩矿物发育各种塑性变形显微构造。变形过程中同种造岩矿物的动态重结晶新晶与塑变残斑（残晶） 之间化学成分变化不明显, 表明在变形期间水活度低,以位错蠕变为主。该构造岩形成于深地壳麻粒岩相变质的晚期阶段,是地体在早期阶段于下地壳底部－上地幔顶部发生高压麻粒岩相变质作用后因构造抬升进入深地壳麻粒岩相环境下发生退变质和强烈韧性剪切变形的产物, 其形成后经历了快速的构造折返过程。  相似文献   

烟台北部古元古代芝罘群变形变质作用及演化          下载免费PDF全文

薛志忠  冯利彬  刘玉潭 《山东国土资源》2001,17(3):44-51

在分析烟台北部芝罘群主要变质岩类的变质矿物共生组合、变质相系及构造岩等特征的基础上,对该群变形、变质作用及演化特征进行了探讨.认为该区芝罘群曾经历1期韧性变形作用和4期变质作用(古元古代高角闪岩相、中元古代早期低角闪岩相、中元古代晚期高绿片岩相及新元古代低绿片岩相变质作用).  相似文献   

桐柏地区高压变质地体在地壳中的抬升机制   总被引：9，自引：7，他引：2  

崔建军  胡健民  刘晓春 《岩石学报》2009,25(9):2165-2176

桐柏杂岩位于秦岭与大别造山带之间,南北两侧为NWW-SEE向延伸的含榴辉岩高压变质地体,其构造就位过程及其与高压变质地体的构造关系为地质学家们所关注.本文研究表明,所谓的桐柏杂岩实际上是一个早白垩世花岗质片麻岩杂岩体,其内包裹一定数量的三叠纪中高级变质岩石.桐柏杂岩南北两条边界韧性剪切带具有相反的运动学指向,分别为大型右行和左行韧性剪切带,其形成时代为131Ma.这两条韧性剪切带中的剪切面理分别朝SSW和NNE向倾斜,韧性剪切带及杂岩体内部发育的拉伸线理均稳定地朝SEE方向缓倾伏.而在杂岩体的东端发育低角度近南北向韧性剪切变形带,其糜棱面理朝SEE方向低角度缓倾斜,矿物拉伸线理也朝SEE方向低角度缓倾伏,运动学标志指示东侧地质体朝295°～310°的方向逆冲.因此,桐柏杂岩实际上被一个顺造山带的韧性剪切带所围限,这个韧性剪切带及杂岩体内部韧性变形运动学指示了一个早白垩世由东向西的低角度抬升过程,而这一过程直接导致了含榴辉岩高压变质地体沿着造山带的方向从地壳深部抬升到近地表.这一研究结果对理解和认识桐柏-大别-苏鲁地区高压一超高压变质地体的晚期抬升过程具有重要意义.  相似文献   

榴辉岩韧性剪切变形中的流体作用及地球化学效应     

高利娥  曾令森  胡明月  陈晶  贾泽荣 《岩石学报》2011,27(4):1095-1115

韧性剪切带是在较高温条件下机械与化学作用高度耦合的系统。韧性剪切带普遍含有一种或多种流体,流体是韧性剪切变形高度局域化和剪切变形组构形成的主要影响因素。在强应变岩石中,可利用变形矿物的元素地球化学的变化特征来反演参与变形的流体的地球化学性质。苏鲁-大别超高压变质带中,多数榴辉岩经历了强烈的韧性剪切应变和流体作用,形成高度局域化、尺度不等的韧性剪切变形带,为研究在高压-超高压条件下,参与流体的性质,应变和流体相互作用提供了重要机会。样品DH-2G是一强烈剪切榴辉岩,由石榴石、绿辉石、金红石,及少量的多硅白云母、黝帘石、角闪石、斜长石、石英、锆石和磷灰石组成。在不同应变域,矿物的粒度变化明显。在类变斑晶域,石榴石粒度比剪切条带中的小2~4倍。在以下讨论中,与细粒石榴石(石榴石-I)共生的绿辉石称为绿辉石-I,与粗粒石榴石(石榴石-II)共生的绿辉石称为绿辉石-II。电子探针和原位LA-ICP-MS测试结果表明:(1)除Ni外,两类石榴石没有显著区别;(2)两类绿辉石在主量元素上也没有明显的差异,但微量元素特征,尤其是稀土元素上,存在明显的变化。与绿辉石-I相比,绿辉石-II具有以下特征:(1)轻稀土明显降低,达25~40倍左右;(2)重稀土明显富集,升高5~10倍;(3)Ni、Zn、Co、Sc、Ba、Zr、Y、Rb、Hf和HREE明显升高,而 V、Sr、U、Th、Pb和LREE明显降低;和(4)微弱的正Eu异常, Eu/Eu^*=1.04~1.45,绿辉石-I基本上没有Eu异常。并且,剪切带域金红石的Nb/Ta比值从核部(<19.0)到边部(>20.0)显著增加。岩相学、元素和温压估计研究表明:在剪切过程中不存在外来流体,流体是由无水矿物(绿辉石、石榴石、金红石等)在超高压榴辉岩折返减压过程中通过压力降低出溶结构羟基或分子水,释放出流体,流体富含V、Sr、U、Th、Pb、Zr、Nb和LREE等微量元素。这些流体显著影响深俯冲地壳的流变学性质,是迁移活动元素(LILE和LREE)及保守元素(HFSE等)的重要载体,对超高压岩片的快速折返发挥关键作用。  相似文献   

Regional flow perturbation folding within an exhumation channel: A case study from the Cycladic Blueschists     

《Journal of Structural Geology》2014

Kilometre-scale cylindrical folds and associated parasitic folds that trend at small angles to the transport lineation are analysed along a 100-km-long transport-normal segment of the Cycladic Blueschists in an attempt to reconstruct the 3D structural architecture within an exhumation channel. Reversals in the polarity of both fold vergence and the hinge/lineation obliquity occur in a flow-normal direction, defining transport-parallel culmination and depression surfaces that root downwards onto an underlying detachment. Fold patterns generated around culmination and depression surfaces support models of flow-perturbation folding where folds initiate at small angles or sub-parallel to transport in response to wrench-dominated differential shearing. Successive culmination and depression surfaces are separated from one another by along strike distances of ∼20 km, although atypical fold geometries developed in the flanks of major culmination and depressions follow their own patterns, revealing that smaller perturbations occur within the larger scheme. Major culminations are interpreted to reflect regions of surging flow marked by increased velocity during exhumation, whilst the opposite is true for depressions. This behaviour implies that on a regional scale, differential shear varies laterally in an irregular-sinusoidal manner defining areas of relative high and relative low displacement within the exhumation channel.  相似文献   

构造控金与动力成金     

宫同伦 《地球科学与环境学报》1993,(4)

本文在构造控制金矿床理论的基础上,进一步提出了断裂构造控制金矿床的思想,主张是断裂构造控金,而非褶皱构造控金;是脆性断裂带控金,而非韧性剪切带控金。文中阐述了动力作用为何能形成金矿床和如何形成金矿床,同时强调了动力作用可使原有的各类金矿体富化,形成富矿体。  相似文献   

Glacitectonic deformation in the Chuos Formation of northern Namibia: implications for Neoproterozoic ice dynamics     

Marie E. Busfield  Daniel P. Le Heron 《Proceedings of the Geologists' Association. Geologists' Association》2013

The Chuos Formation is a diamictite-dominated succession of Cryogenian age, variously interpreted as the product of glaciomarine deposition, glacially related mass movement, or rift-related sediment remobilisation in a non-glacial environment. These interpretations have wide ranging implications for the extent of ice cover during the supposedly pan-global Neoproterozoic icehouse. In the Otavi Mountainland, northern Namibia, detailed analysis of soft-sediment deformation structures on the macro- and micro-scale support glacitectonic derivation in response to overriding ice from the south/south-east. Overall, the upward increase in strain intensity, predominance of ductile deformation features (e.g. asymmetric folds, rotational turbates and necking structures, clast boudinage, unistrial plasmic fabrics) and pervasive glacitectonic lamination support subglacial deformation under high and sustained porewater pressures. In contrast, soft-sediment structures indicative of mass movements, including flow noses, tile structures, and basal shear zones, are not present. The close association of subglacial deformation, abundant ice-rafted debris and ice-contact fan deposits indicate subaqueous deposition in an ice-proximal setting, subject to secondary subglacial deformation during oscillation of the ice margin. These structures thus reveal evidence of dynamic grounded ice sheets in the Neoproterozoic, demonstrating their key palaeoclimatic significance within ancient sedimentary successions.  相似文献   

Progressive extensional shear structures in a detachment contact in the Western Sierra Nevada (Betic Cordilleras,Spain)     

Jesús Galindo-Zaldivar  Francisco Gonzalez-Lodeiro  Antonio Jabaloy 《Geodinamica Acta》2013,26(1):73-85

Abstract

The present contact caused by the superposition of the Alpujarride complex over that of the Nevado-Filabride in the western area of Sierra Nevada and Sierra de Filábres corresponds to a detachment. The deformation in the footwall associated with this contact, produced mylonitic fabrics with a significant stretching-lineation, over which brittle structures are superimposed. The deformation in the hanging wall associated with this contact is, on the other hand, essentially brittle. These deformations are subsequent to a series of syn-to post-metamorphic structures related to thrust phases.

The micro- and meso-structures indicate that the hanging wall has moved towards the west-south-west.

Other brittle structures, which began during the same extensional regime, are superimposed on the detachment and have continued to develop up to the present time. These structures were produced in an extensional regime with a non-coaxial deformation component and suggest the possibility of a tectonic evolution similar to that described for core complexes in the USA.  相似文献   

新疆萨尔托海石英菱镁岩中发育的韧性剪切带及其对金矿的控制   总被引：3，自引：2，他引：1  

邱添  朱永峰 《岩石学报》2012,28(7):2250-2256

萨尔托海金矿产在达拉布特蛇绿混杂岩带中。本文首次在该金矿区厘定出韧性剪切带,糜棱岩或者糜棱岩化石英菱镁岩中构成糜棱面理的矿物(铬云母、石英)形成于韧性剪切变形过程中,而切割糜棱面理的方解石-石英-黄铜矿-白云母脉代表脆性变形阶段的流体活动。根据矿物组合相互切割关系,识别出三期构造变形:早期NE向韧性变形(形成铬云母-石英组合)之后,发生了应力方向显著不同的破裂,形成NNW向分布的方解石-石英-黄铜矿-白云母脉;再晚期,应力方向又恢复到NE向,发育了浅层次的脆性构造破坏,形成了白云母-石英细脉。韧性剪切变形向脆性变形转换期间形成了石英-碳酸盐脉,其中往往含硫化物和自然金,此阶段是萨尔托海金矿的主要成矿时期。韧性剪切带控制着萨尔托海地区的金矿分布,成矿作用主要受沿剪切带迁移流体的控制,穿切糜棱面理的方解石-石英-黄铜矿-白云母脉是主要的找矿标志。韧性剪切带对金矿的显著控制表明,韧脆性转换期间形成的含硫化物石英碳酸盐脉以及相伴生的热液蚀变使金富集成矿,矿体一般赋存在断裂构造复杂的膨胀部位。萨尔托海金矿的成因与蛇绿岩的形成和演化没有关系。对韧性剪切带的系统研究是在该地区取得找矿勘探突破的关键。  相似文献   

辽东半岛中生代韧性剪切带特征及其地质意义     

屈奋雄 《国土资源》1992,(1)

辽东半岛韧性剪切带可分为两种类型,一类为低角度逆冲推覆型,多为北东—南西向或北北东—南南西走向,大致分布于辽东半岛东南边缘;另一类为高角度近水平剪切滑动型,多分布于半岛内部的a线理及运动学特征指示这些剪切带的总体应力场这由南东东向北西西推覆、挤压。剪切带的形成时间大多在中生代末期。辽东半岛金矿大多与这次韧性剪切活动有关,由剪切活动产生的一些韧-脆性的变形带很可能即是环太平洋成矿作用的容矿构造。  相似文献