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1.
The Guarguardz Complex, basement of the Cordillera Frontal, included in the proposed Chilenia Terrane, consists of metasedimentary rocks deposited in clastic and carbonatic platforms. Turbiditic sequences point out to slope or external platform environments. According to geochemical data, the sedimentary protoliths derived through erosion of a mature cratonic continental basement. Volcanic and subvolcanic rocks with N and E-MORB signature were interbeded in the metasedimentary rocks during basin development. A compressional stage, starting with progressive deformation and metamorphism, followed this extensional stage. Continuing deformation led to the emplacement of slices of oceanic crust, conforming an accretionary prism during Late Devonian. The Guarguardz Complex and equivalent units in western Precordillera and also in the Chilean Coastal Cordillera share common evolutional stages, widely represented along the western Gondwana margin. These evidences imply that Chilenia is not an allochthonous terrane to Gondwana, but a portion of its Early Paleozoic margin. Regional configuration indicates that the Guarguardz Complex and equivalent units represent the accretionary prism of the Famatinian arc (Middle Ordovician-Late Devonian). 相似文献
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江南造山带北缘鄣源构造带主要地质特征 总被引：4，自引：0，他引：4
鄣源构造带现今呈北东—南西向展布的混杂新元古代早期基性岩块以韧性变形构造为显著特点,并强烈叠加印支—燕山期逆冲-走滑脆性断裂的区域性超壳断裂带.构造带历经多期构造变形,主期构造变形以晋宁期弧-陆(扬子陆块)碰撞在地壳内部层圈结构相对薄弱部位形成的向南逆冲式韧性变形为特征.鄣源构造带中的蚀变枕状—块状基性熔岩、辉长岩、辉绿岩等基性岩块在空间上紧密相伴,形成于低速扩张的陆缘小洋盆扩张脊环境,具初始洋壳基性岩特征,属皖南伏川蛇绿岩西延组成部分.鄣源构造带及其两侧广布的新元古代早期火山-沉积建造体形成于大陆边缘与板块构造体制相关的构造-沉积环境,鄣源构造带南侧为裂解海盆沉积体系,北侧属于与大陆边缘火山弧有关的盆地沉积体系,鄣源构造带内显示深海—半深海沉积特征.鄣源构造带北东、南西向延伸分别与皖南伏川蛇绿混杂岩带及景德镇-宜丰深断裂带相接,是江南造山带北缘以皖南伏川蛇绿岩为代表的新元古代早期陆缘小洋盆俯冲-碰撞拼合带的重要组成部分. 相似文献
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The Norumbega fault system in the Northern Appalachians in eastern Maine experienced complex post-Acadian ductile and brittle deformation from middle through late Paleozoic times. Well-preserved epizonal ductile shear zones in Fredericton belt metasedimentary rocks and granitic batholiths that intrude them provide valuable information on the nature, geometry, and evolution of orogen-parallel strike-slip Norumbega faulting. Metasedimentary rocks were ductilely sheared into phyllonite schistose mylonite, whereas granite into mylonite within the ductile shear zones. Ductile shearing took place at conditions of the lower greenschist facies with peak temperatures on the order of 300–350° based on comparison of plastic quartz and brittle feldspar microstructures, confirming a shallow crustal environment during faulting.Ductile shear strain was partitioned into two major shear zones in easternmost Maine—the Waite and Kellyland zones—but these zones converge toward the southwest. Megascopic, mesoscopic, and microscopic kinematic indicators confirm that fault motion in both zones was dominantly dextral strike-slip. Detailed mapping, especially in the plutonic rocks, reveals a complex ductile deformation history in the area where the Waite and Kellyland zones converge. Shear strain is broadly distributed in the rocks between Kellyland and Waite zones, and increases toward their junction. Multiple dextral high-strain zones oblique to both zones resemble megascopic synthetic c′ shear bands. Together with the Kellyland and Waite master shear zones, these define a megascopic S–C′ structure system produced in a regional-scale dextral strike-slip shear duplex that developed in the transition zone between the deeper (south-central Maine) and shallower (eastern Maine) segments of the Norumbega fault system.Granite plutons caught within the strike-slip shear duplex were intensely sheared and progressively smeared into long and narrow slivers identified by this study. The western lobe of the Deblois pluton and the Lucerne pluton have been recognized as the sources, respectively of the Third Lake Ridge and Morrison Ridge granite slivers. Restoration of both granite slivers to their presumed original positions yields approximately 25 km of dextral strike-slip displacement along only the Kellyland and synthetic ductile shear zones. 相似文献
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云南景洪南联山橄榄岩—闪长岩型岩体的特征及地质意义 总被引：2，自引：0，他引：2
岩相学和地球化学特征表明,南联山岩体是岩浆侵位的,岩石的分布显示环带构造;从中心向外依次为角闪橄榄岩、辉绿(辉长)岩和闪长岩。它们的结构和化学特征指示,这些岩石是由辉长-闪长岩质的岩浆结晶分异作用而形成的,角闪橄榄岩和部分辉绿岩为堆晶岩,其它的岩石为堆晶作用后分异而成的岩浆共结结晶作用所形成。原始岩浆的成分类似于高铝玄武岩和(或)玄武质安山岩。 相似文献
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中咀铜矿床位于扬子地台西缘江浪变质核杂岩内,围岩为一套中元古界变质火山-陆源碎屑沉积岩。原岩经过多期次变形变质作用,韧性剪切带控制了蚀变带、矿化带和矿体的分布。包括中咀铜矿在内的"里伍式"铜矿床物质具有多来源、成矿作用具有多期次、多成因的特点,其主成矿作用为燕山期中高温热液交代充填成矿,成因上属于海相沉积-改造型矿床。成矿物质主要来源于含矿岩系本身,控矿构造主要为韧性剪切带和穹窿构造。 相似文献
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贺兰山北段牛头沟金矿区围岩的原岩恢复、时代及其地质意义 总被引：4，自引：2，他引：2
牛头沟金矿区位于华北陆块鄂尔多斯地块西缘贺兰山北段之基底杂岩带,赋矿地层为一套古元古界宗别立群第二亚群(Pt1Z2)中-深程度变质岩系,主要岩石类型是黑云斜长片麻岩和变粒岩。岩石地球化学特征分析及原岩恢复说明,蚀变岩型金矿体的围岩由正、副变质岩类共同组成,其中变粒岩的原岩为沉积碎屑岩,黑云斜长片麻岩的原岩为花岗闪长质侵入岩。离子探针锆石U-Pb定年表明,表壳岩的形成时代小于2120Ma,花岗闪长岩锆石U-Pb年龄为1950±8.9Ma,辉绿岩脉的侵入与花岗闪长岩属同期。综合研究表明,矿区变质岩的原岩形成时代不是前人认为的晚太古代,而是古元古代。同时应将属于正变质岩类黑云斜长片麻岩(原岩为花岗闪长岩)从宗别立群(Pt1Z)地层中分离出来,作为侵入岩单元考虑。 相似文献
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《Journal of Structural Geology》1988,10(3):283-296
Metasomatic tremolite-rich mylonites are widespread in imbricate thrust slices of ultramafic rocks of the ophiolitic Ingalls Complex in Washington State. Protoliths for these amphibolite-facies mylonites were peridotite and serpentinite. Abundant syntectonic tremolite veins in the ultramafites record narrowly channelized flow of infiltrating fluids, whereas metasomatic mylonite zones record more pervasive flow. Fluids were probably released mainly by prograde devolatization reactions within serpentinite and mafic ophiolitic rocks that experienced earlier hydrothermal metamorphism.Olivine apparently deformed by dislocation creep in the mylonites. In the tremolite-rich rocks, locally preserved amphibole porphyroclasts deformed mainly by microfracturing. Acicular tremolites, which dominate the mylonites, form syntectonic overgrowths on porphyroclasts and probably record diffusive mass transfer which may have accompanied cataclasis. Acicular tremolites subsequently were folded and define both post-crystalline crenulations and polygonal arcs.Fluid flow, deformation and metamorphism were apparently complexly interrelated in the imbricate zone. Thrusts juxtaposed contrasting rock types that were sources and sinks for fluids, and shear zones focused fluid flow. Metamorphism probably facilitated deformation through the release of fluids during dehydration reactions. High fluid pressure may have led to hydraulic fracturing and may have controlled strain softening in the tremolitic mylonite zones as it favored microcracking and diffusive mass transfer over dislocation creep. Infiltrating metasomatic fluids probably play an important role in the evolution of shear zones in many ultramafic bodies during medium-grade metamorphism. 相似文献
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云南哀牢山地区构造岩石地层单元及其构造演化 总被引：28，自引：5，他引：28
依据新获得的同位素年代学资料和构造岩石地层单元,重新认识了云南哀牢山造山带形成与演化历史。认为:在哀牢山地区元古界深变质岩系属基底构造层;前造山期岩石组合及构造演化为扬子地块西缘被动大陆边缘志留纪深水相碎屑岩→陆缘泥盆纪被动裂谷盆地中火山-沉积岩→石炭纪哀牢山有限洋盆及蛇绿岩石组合→晚二叠世-早三叠世哀牢山洋-陆碰撞成陆及弧火山岩-陆相碎屑岩组合。燕山期主造山期及岩石组合为晚三叠世-侏罗纪前陆盆地磨拉石建造-同造山期中酸性侵入岩-燕山期脆韧性剪切带及构造岩。喜马拉雅山期陆内造山成原的岩石组合为第三-第四纪陆内山间盆地中磨拉石建造-红河韧性剪切带及构造岩-富碱侵入岩和煌斑岩。 相似文献
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鲁西地区韧性剪切带岩石磁组构分析及其构造意义 总被引：1，自引：1，他引：0
岩石磁组构分析可用来研究岩石的组构特征及构造变形。鲁西地区韧性剪切带岩石磁组构具有磁各异性度Ｐ和磁百分率各向异性值Ｈ高、磁化率量值椭球呈压扁状、磁面理发育而磁线理不发育的特点。区内韧性剪切带变形强烈,以压扁作用为主,最大主压应力方向近ＮＥ和Ｓ－Ｎ向,以右旋运动为主。韧性剪切带形成以后,区内主要经历了热蚀变和脆性变形,韧性变形很弱 相似文献
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内蒙古大青山地区金矿床类型、控矿规律及找矿方向 总被引：9，自引：0，他引：9
内蒙古呼和浩特地区主要有三种类型金矿床：构造蚀变岩型、中基性岩浆热液型和绿岩型。它们分别受控于不同地质条件：构造蚀变岩型主要受控于韧性剪切带或断裂带构造，中基性岩浆热液型主要受控于中基性幔源的埃达克岩-赞岐状岩-富Nb辉长岩，绿岩型金矿主要受二道洼群地层控制。然而，这些矿床成因复杂，往往受控于多个成矿因素，当上述两个以上成矿条件同时存在时，成矿的可能性就会增大。如绿岩型金矿主要受控于二道洼地层，但矿体主要受韧性剪切带或断裂构造的叠加部位控制。因此，在本区寻找以上三种类型的金矿床，特别注意在二道洼群地层、中基性幔源埃达克岩-赞岐状岩-富Nb辉长岩附近和韧性剪切带或断裂构造叠加部位。另外，由于与中基性岩有关的矿床还未引起足够重视，注意寻找该类型矿床就显得很有必要。 相似文献
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东天山-北山造山带中大型韧性剪切带属性及形成演化时限与过程 总被引：10，自引：5，他引：5
塔里木盆地北缘的东天山-北山造山带中发育多条近E-W走向的大型韧性剪切带,它们构成了造山带中不同地体单元的主要边界,是碰撞造山及造山后的产物。本文在野外调查基础上,通过微观/宏观构造、几何学/运动学/动力学/年代学相结合的研究、厘定了东天山北山造山带中的7条大型韧性剪切带,阐述了剪切带的延伸、规模、剪切变形特征、变形条件以及形成与演化时限。并讨论了这7条不同类型韧性剪切带的形成过程以及东天山和北山古生代造山过程中所起的重要作用。 相似文献
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雅鲁藏布江缝合带内构造岩片划分及形成——以仲巴-桑桑段为例 总被引：1，自引：2，他引：1
构造岩片作为造山带中非史密斯地层地区的填图单位有其重要的地质意义,本文将雅鲁藏布江缝合带分为6大构造岩片,其中蛇绿混杂岩岩片又分4个次级岩片,进一步阐述了缝合带内不同单元具有不同岩性和不同构造型式,是一条复杂的构造带,并发现俯冲板块一侧的不同构造单元具有自南而北,由脆性变形到低温高压变质、脆-韧性变形,超基性岩的深层次韧性变形的分布规律,大多数岩片的分布是通过多重逆冲推覆型或走滑型的断层将其从地壳深部挤出定位的。雅鲁藏布江缝合带内的构造岩片特征,反映了冈瓦那大陆北缘自三叠纪末期到第四纪经历了裂陷、扩张、多岛洋、闭合、俯冲、碰撞、褶皱、推覆造山的全过程。 相似文献
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新疆兴地断裂带前寒武纪构造—岩浆—变形作用特征及其年龄 总被引：15，自引：7，他引：8
本文分析了发生在塔里木北缘兴地断裂带的多期构造—岩浆演化特征。在此基础上,对三件前寒武纪火成岩样品进行了LA-ICP-MS锆石U-Pb定年,对兴地断裂带韧性变形构造进行了运动学分析。研究表明,兴地断裂带至少经历了4期地质构造演化; 其中,前寒武纪有两期。第一期发生在前南华纪,以强烈的挤压褶皱、韧性剪切变形和岩浆活动为特色; 第二期发生在南华纪—震旦纪,以广泛发育的双峰式火成岩、复式岩流和基性岩墙群为特征,伴随大规模冰川作用和地壳沉陷,对应Rodinia超大陆的裂解。LA-ICP-MS法锆石U-Pb年龄测定表明,辉长岩中的俘获锆石保留了3114±20Ma、2509±42Ma、1916±36Ma等多期古构造演化和岩浆活动信息,揭示研究区深部存在一个中-新太古代和古元古代的基底。双峰式火成岩测年数据证实,区内在820~800Ma(花岗岩脉,798±7Ma; 辉长辉绿岩墙,816±15Ma)发生过强烈的裂谷—岩浆活动。根据构造交切关系,兴地断裂带发生过两期前南华纪韧性变形;变形时代尚不清楚。运动学分析表明,第一期为朝北逆冲的推覆变形,第二期为右旋走滑变形。南华纪以来,区域变质和韧性变形微弱,为韧脆性变形。 相似文献
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内蒙古东五分子地区韧性剪切变质作用的特征 总被引：6，自引：0，他引：6
东五分子地区花岗-绿岩地体经受了三种类型变质作用的改造。韧性剪切带不仅控制了区域变质岩组合的分布,而且也导致其变质作用的强度出现了逆转序列。根据岩石的结构、碎斑含量及矿物成分,韧性剪切变质岩划分为三类,其共同特点是具有碎斑结构。其变形结构分为单矿物型及组合型。同一块韧性剪切变质岩由处在单变平衡的一组矿物组成。根据岩石变形及重结晶的特点,结合其产状,确定出两种不同类型韧性剪切变质带。共生矿物对的研究证明它们形成于地壳不同深度及温度、压力条件。本区的金矿化、运移、沉淀与韧性剪切变质带紧密相关。 相似文献
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柴达木盆地西北缘牛鼻子梁铜镍矿矿床特征及其发现意义 总被引：3，自引：0，他引：3
牛鼻子梁铜镍矿产于柴达木盆地西北缘古陆块上,其成矿与基性-超基性层状杂岩体有关。共发现3个岩体,其中以Ⅰ号岩体规模较大,出露面积近7km2,其余2个岩体较小。岩体岩石堆晶结构明显,具层状和纹层状构造。Ⅰ号岩体出露岩性以层状淡色辉长岩、闪长岩为主,局部夹超基性岩,代表层状杂岩体上部层序。Ⅱ、Ⅲ岩体以超基性岩石为主,代表层状杂岩体下部层序,是主要的含矿层位。通过槽、钻探验证,在Ⅱ、Ⅲ岩体已发现硫化物铜镍矿体9条,其中,一条矿体的视厚度达41.1m,Ni平均品位为0.5%,最高1.57%。其矿石矿物主要为磁黄铁矿、镍黄铁矿和黄铜矿等,属岩浆熔离改造型矿床,有后期热液叠加。该类型矿床是在柴达木地块周缘首次发现,具有重要的现实意义,其为今后在柴达木盆地周缘寻找与基性-超基性岩有关的铜镍硫化物矿床提供了依据。 相似文献
17.
Osama M. K. Kassem Said H. Abd El Rahim EL Said R. El Nashar Kaled M. AL Kahtany 《Geology of Ore Deposits》2016,58(6):499-515
The use of porphyroclasts rotating in a flowing matrix to estimate mean kinematic vorticity number (Wm) is important for quantifying the relative contributions of pure and simple shear in wall rocks alterations of shear zone at Dungash gold mine. Furthermore, it shows the relationship between the gold mineralization and deformation and also detects the orientation of rigid objects during progressive deformation. The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures which are attributed to various deformational stages of the Neoproterozoic basement rocks. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. The kinematic vorticity number for the metavolcanic and metasedimentary samples in the Dungash area range from 0.80 to 0.92, and together with the strain data suggest deviations from simple shear. It is concluded that nappe stacking occurred early during the underthrusting event probably by brittle imbrication and that ductile strain was superimposed on the nappe structure during thrusting. Furthermore, we conclude that disseminated mineralization, chloritization, carbonatization and silicification of the wall rocks are associated with fluids migrating along shearing, fracturing and foliation of the metamorphosed wall rocks. 相似文献
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19.
中天山北缘大型右旋走滑韧剪带研究 总被引：22，自引：4，他引：18
中天山北缘是一个近 EW向的大型右旋走滑韧剪带。宏、微观构造尺度的运动学研究表明 ,该带经历过至少二期韧性变形作用。第一期为从南向北的逆冲推覆韧剪变形 ,时代为中—晚志留世 ,以米什沟剖面为代表 ,对应于早古生代洋壳从北向南俯冲及稍后吐哈陆块朝中天山岛弧的碰撞事件。第二期为沿 EW方向的右旋走滑韧性变形 ,其构造形迹广泛分布于中天山北缘带各个地段 ;北天山石炭纪火山岩已卷入该期构造活动 ,走滑时代为晚石炭世—早二叠世 ,对应于晚石炭世塔里木与西伯利亚两大板块碰撞造山诱发的陆内变形、走滑剪切。走滑带中新生白云母 4 0 Ar/39Ar年龄为 ( 2 69± 5) Ma。剪切面理、拉伸线理、矿物韧剪构造、石英 C轴组构提供了构造运动学证据 ;地层不整合及同位素测年值提供了变形时间证据。二叠纪以后的构造事件也影响到中天山北缘带 ,但只有脆性变形形迹 ,无韧性剪切。最后对本区古生代构造演化进行了讨论 相似文献
20.
DEFORMATION OF THE EASTERN HIMALAYAN SYNTAXIS: EVIDENCES FROM STRUCTURES AND KINEMATICS OF ITS WESTERN BOUNDARY 总被引：4，自引：0，他引：4
DEFORMATION OF THE EASTERN HIMALAYAN SYNTAXIS: EVIDENCES FROM STRUCTURES AND KINEMATICS OF ITS WESTERN BOUNDARYtheNationalNaturalScienceFoundationofChina (grants 49732 10 0and 4980 2 0 2 0 ) 相似文献