共查询到19条相似文献，搜索用时 234 毫秒
1.
2.
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
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
3.
云蒙山变质核杂岩抬升过程中伸展拆离和岩浆底辟联合作用的证据 总被引：3，自引：0，他引：3
北京地区云蒙山变质核杂岩在白垩纪阶段抬升的早期,伴随着沿四合堂剪切带由北向南的拆离滑脱和大型花岗闪长岩的垂向侵位,晚期变形发生在花岗闪长岩岩基周边及其邻近围岩中,形成云蒙山剪切带,并伴随大量同构造的花岗岩和伟晶岩岩脉灌入。剪切带中所有的岩脉都随时间发生了不同程度的变形,较老的岩脉形成紧闭的圆柱状褶皱,枢纽与剪切带的线理和面理接近平行。岩脉与剪切带中L-S组构的平行化作用主要是由于这种转动的结果。岩脉的成分和长英指数随它们的变形程度发生变化,说明持续的岩浆分异作用与韧性剪切变形是同时发生的。云蒙山剪切带由岩浆底辟引起的上盘岩石重力所驱动,并不断得到同构造侵位岩脉的补充,起到存储和不断改造侵位岩脉的作用。早期伸展体制下形成的四合堂剪切带局部遭受云蒙山剪切带的改造或复合。该地区的岩石、构造和同构造岩脉的变形几何学和运动学证据表明,太古宙结晶基底的抬升是下部岩浆底辟与上部地壳伸展拆离共同作用的结果。 相似文献
4.
北京地区云蒙山变质核杂岩在白垩纪阶段抬升的早期,伴随着沿四合堂剪切带由北向南的拆离滑脱和大型花岗闪长岩的垂向侵位,晚期变形发生在花岗闪长岩岩基周边及其邻近围岩中,形成云蒙山剪切带,并伴随大量同构造的花岗岩和伟晶岩岩脉灌入。剪切带中所有的岩脉都随时间发生了不同程度的变形,较老的岩脉形成紧闭的圆柱状褶皱,枢纽与剪切带的线理和面理接近平行。岩脉与剪切带中L-S组构的平行化作用主要是由于这种转动的结果。岩脉的成分和长英指数随它们的变形程度发生变化,说明持续的岩浆分异作用与韧性剪切变形是同时发生的。云蒙山剪切带由岩浆底辟引起的上盘岩石重力所驱动,并不断得到同构造侵位岩脉的补充,起到存储和不断改造侵位岩脉的作用。早期伸展体制下形成的四合堂剪切带局部遭受云蒙山剪切带的改造或复合。该地区的岩石、构造和同构造岩脉的变形几何学和运动学证据表明,太古宙结晶基底的抬升是下部岩浆底辟与上部地壳伸展拆离共同作用的结果。 相似文献
5.
八卦庙金矿床的控矿构造为脆-韧性剪切带,其变形从早至晚经历了变形分解阶段、构造挤出阶段与倾竖褶皱阶段。在变形分解阶段,剪切带内形成线性强变形带与透镜状弱变形域,并在强变形带中发育一系列"顺层"石英脉,且递进剪切为一系列A型褶曲;在构造挤出阶段,剪切带产状由缓变陡,构造体制逐渐由非共轴剪切转变为近共轴挤压,形成挤出构造控制的构造蚀变岩型成矿构造;在倾竖褶皱阶段,剪切带叠加了顺层非共轴右行剪切,形成八卦庙倾竖褶皱,并在挤出构造体中形成一组NE向剪裂控制的构造脉型成矿构造。挤出构造主要包括:剪切带边部呈叠瓦状分布的内倾弧形逆冲断层系;剪切带内条带状构造大理岩与构造千枚岩间的滑动构造;构造千枚岩带中发育一系列呈倒水滴状、平面上呈不对称"鱼状"的挤出构造体;挤出构造体中含炭泥砾-角砾岩脉。蚀变岩型金矿体发育于挤出构造体中,其空间排布规律及挤出构造结构完全受控于构造挤出时的动力学机制。单个蚀变岩型金矿体向西侧伏,侧伏角约65°;而南、中、北矿带则整体向东侧伏,侧伏角约25°。 相似文献
6.
7.
8.
湖北银洞沟银金矿构造特征及构造控矿作用 总被引：3，自引：0，他引：3
武当地区位于华北板块和扬子板块的接合部位,属作岭造山带。武当群组成一系列大型韧－脆性剪切带巨型推覆体,银洞沟推覆岩席是其中之一。该区早期构造样式为伸展作用及其伴生的韧性或韧－脆性面型剪切,晚期为推覆线性剪切。根据面埋,线理,褶皱、剪切带等研究成果,作者总结了银洞沟地区构造性质,成矿作用及模式。 相似文献
9.
辽吉朝褶皱带古元古宙岩浆核杂岩及其大地构造意义 总被引：4，自引：1，他引：3
通过对辽吉朝古元古代褶皱带的构造演化分析,尤其对褶皱带南带内发育的典型构造组合及相应出现的岩浆活动、变质作用和为形作用的系统构造分析,提出岩浆核杂岩是古元古代褶皱带早期演化过程中形成的主要构造型式。岩浆核杂岩主要由3种成分、性质、特点及变质演化不同的构造单元构成,即核部岩浆杂岩、外部的滑覆体壳有其间的幔部顺层韧性剪切带。岩浆核杂岩的构造分析,揭示出它们形成于褶皱带早期阶段演化的伸展作用过程中。 相似文献
10.
鄂西北竹山银洞沟银金矿床构造控矿特征 总被引：4，自引：0，他引：4
银洞沟银金矿床位于扬子地台北缘武当推覆体西部,产于武当群变火山岩组与变沉积岩组间的顺层型韧性剪切带中,与构造变形密切相关。晋宁期的伸展作用产生了顺层型韧性剪切带,韧性变形变质作用促使原岩中银金等贵金属、多金属元素活化迁移,随剪切变形变质热液在强应变带中沉淀,形成初始矿源层。印支期的陆陆碰撞作用,促成不同层次面型剪切带岩石褶皱、韧脆性推覆,成矿元素从初始矿源层中再次活化、运移,随着沿褶皱轴面劈理发育的烟灰色糜棱岩化石英脉的形成,沉淀富集于石英脉中,形成银金矿床。脆性变形的叠加,使含矿石英脉产生扭动,促使成矿元素的局部富集,形成透镜状或板状矿体。成矿元素的垂直分带是由构造环境的变化导致成矿元素的叠生作用而形成的。多硅白云母及白云母年龄的测定表明该矿床的成矿期为印支期。 相似文献
11.
12.
按照韧性剪切带的发育程度，将区内划分为迁西群分布区的弱变形域和遵化群分布区的强变形带。根据各种形变特征，认为迁西群及遵化群分别存在三次及两次叠加褶皱，其中迁西期形成的为轴面南倾的东西向线状同斜褶皱；遵化期第一幕为北东向摆动的紧密线形倒转褶皱。由于边界条件的限制，叠加在迁西群上的褶皱，轴向转为近南北向。迁西期褶皱因属同斜而具简单层状体特征，故每个单体的叠加背向形并非三斜对称，主要部分也并非穹盆构造，而为ｗ形蛇形弯曲，不存在原生的穹隆或卵形群构造；遵化期第二幕表现为舒缓的东西向叠加褶皱。区内的主要构造样式为包括迁西群在内的由叠加褶皱及两组共轭韧性剪切带共同作用所形成的迂西－曹在卵形隆起区；遵化群的弧形褶皱群被密云－喜峰口－王厂左行平移韧性断裂带带动形成的宽城－遵化帚状构造亚区以及由遵化群形成的青龙王厂－迁安重熔片麻岩穹隆亚区。 相似文献
13.
Minor folds formed synchronous with ductile deformation in high strain zones can preserve a record of the scale and kinematics of heterogeneous flow. Using structures associated with WNW-directed Caledonian thrusting in N Scotland, we show that localised perturbations in flow resulted in the generation of predominantly cylindrical minor folds with hinges lying at low angles to the transport direction. These define a series of larger-scale fold culminations (reflecting ‘surging flow’) or depressions (reflecting ‘slackening flow’) that are bisected by transport-parallel culmination and depression surfaces. The fold patterns suggest a dominance of layer-normal differential shearing due to gradients in shear strain normal to transport. Culmination surfaces are marked by along-strike reversals in the polarity of structural facing and vergence of minor folds which, contrary to classic fold patterns, define reverse asymmetric relationships. Culmination surfaces separate folding in to clockwise (Z folds) and anticlockwise (S folds) domains relative to the transport lineation. The dip of fold axial planes systematically increases as their strike becomes sub-parallel to transport resulting in a 3D statistical fanning arrangement centred about the transport direction. Thus, mean S- and Z-fold axial planes intersect precisely parallel to the transport lineation and potentially provide a means of determining transport directions in cases where lineations are poorly preserved. Culminations display convergent fold patterns with fold hinges becoming sub-parallel to transport towards the culmination surface and underlying detachment, whilst axial planes define overall concave up listric geometries which are bisected by the culmination surface. Thus, around culminations and depressions there are ordered, scale-independent relationships between transport direction, shear sense, fold facing, vergence and hinge/axial plane orientations. The techniques described here can be applied and used predictively within any kinematically coherent system of ductile flow. 相似文献
14.
The Dabie and Sulu orogens between the North China and the Yangtze cratons were left-laterally offset about 4(H) km along the NE-striking Tan-Lu Fault Zone. The fault zone terminates abruptly at the southeastern corner of the Dabie Orogen, suggesting unique origin of the fault zone which remains controversial. Structures in the Zhangbaling Croup and Feidong Complex in the Zhangbaling Uplift formed in a flat-lying ductile detachment zone with a shear sense of top to the SSW. Whereas, the Tan-Lu shear zone in the l.ujiang area exhibits as a sinistral ductile shear zone. Thus, the Tan-Lu Fault Zone in the east of the Dabie Orogen experienced two phases of deformation. The first phase deformation exhibits as sinistral ductile shear belts, the sinistral ductile shear zone was then involved in the NK-SW trending tightly folds and thrusts deformation. The Susong Complex and Zhangbaling Group in the Dabie Orogens exhibit as exhumation structures. According previous muscovite 4'Ar/,>Ar ages and deformation of syn-collisional folds and thrusts, we propose an indentation-induced continent-Tearing model for the initialization the Tan-Lu Fault Zone. 相似文献
15.
晓天-磨子潭剪切带的早白垩世活动及其对北大别穹隆演化的制约 总被引：1，自引：0，他引：1
晓天-磨子潭剪切带是大别造山带内北大别杂岩带与北淮阳浅变质岩带的地表分界线,其构造演化特征可以为北大别穹窿的形成演化提供重要制约.本次由此韧性剪切带内4个未变形岩体的锆石样品进行LA-ICP MS U-Pb年龄测定得知,该韧性剪切带形成于早白垩世130～120 Ma期间,为后造山伸展断层.构造分析表明,这条剪切带形成于北大别穹窿深处,为一条平缓韧性拆离剪切带.其形成指示北大别单元在早白垩世初的造山带重力垮塌中发生了深部地壳物质的韧性侧向流动,而该剪切带则是地壳物质韧性侧向流动的上部运动边界.在随后的大规模岩浆上升与浮力增加中,该剪切带与北大别穹窿一起发生隆升而变陡,并随着不均匀隆升而使剪切带出现现今的几何学特征.晓天-磨子潭剪切带的演化显示北大别穹窿是由大别造山带晚造山伸展过程中形成的变质核杂岩组成的. 相似文献
16.
The Klondike Schist that forms the basement rocks for the famous Klondike placer goldfield was emplaced as km-scale thrust
slices in Early Jurassic time, along with some thin (10 to 30 m-scale) slices of greenstone and ultramafic rocks. Permian
metamorphic fabrics in the schists were deformed during thrust emplacement by structures formed as the rocks passed through
the brittle–ductile transition. Early-formed thrust-related structures were almost-pervasive recumbent folds that affected
both the schist and greenstone/ultramafic slices and imposed a spaced cleavage with minor recrystallisation of micas. These
structures gave way to shallow-dipping phacoidal cleavage near (within <100 m of) thrust structures. Thrust-related structures
have been overprinted locally by well-defined steeply dipping reverse fault-fold zones, and associated upright folding on
regional (km) to mesoscopic (m) scales. The fold-fault zones occur as two orthogonal sets of structures oriented NW to N and
NE to E. Some of these steeply dipping fault zones have been reactivated by Late Cretaceous normal faulting. Orogenic (mesothermal)
gold-bearing veins were emplaced in local sites of extension during or after formation of the compressional fault-fold zones
and before normal fault reactivation. Over 400 veins (m to cm-scale) observed in this study imply a general NW strike for
mineralised structures (W to N), but with a broad scatter of orientations. Vein emplacement was controlled principally by
fold axial surfaces of kink folds of the fault-fold generation. However, some other local extension sites have opened along
preexisting structures to host veins locally, including metamorphic foliation and spaced cleavage planes. In addition, irregular
extensional fractures with no obvious structural control host some veins. The Klondike mineralised veins formed as swarms
with broad regional structural control, but represent relatively diffuse mineralised zones, with numerous scattered small
veins, compared to most orogenic vein systems. These diffuse vein swarms appear to be sufficient sources for the rich and
geographically localised placer gold deposits that formed in overlying gravels during erosion of the Klondike Schist basement. 相似文献
17.
内蒙古哈达门沟金矿构造演化及成矿控矿构造特征 总被引：1，自引：0，他引：1
哈达门沟金矿是内蒙古迄今最大的金矿床,具有超大型金矿床规模。金的成矿作用对岩性没有明确的选择性,而主要是受褶皱断裂构造的控制。成矿流体主要来自深源,在有利的构造扩容带中聚积成矿。研究表明,该区的构造变形从早到晚,力学性质往往从塑性到脆性,构造规模从小到大,构造类型则是褶皱与剪切带同时形成,或相间发育。该区主要经历了4个期次的强烈褶皱剪切作用,并形成了主要的成矿控矿构造。第一期构造变形时岩石的流变性较强,褶皱幅度较小,一般多表现为小规模的塑性流变褶皱,并产生了小规模韧性剪切带;第二期(主期)褶皱以乌拉山主峰为主的东西向区域规模的复式背、向斜(形),并在主期褶皱的倒转翼发育了一系列与褶皱同向延伸的脆韧性剪切带,它们构成了区域性构造薄弱带;第三期为横跨叠加褶皱,使近东西向褶皱发生了南北向蛇形弯曲,伴随该期褶皱作用形成了低绿片岩相韧脆性剪切带,为深源成矿流体的贯入与集聚成矿提供了很好的赋存空间,是主要的成矿控矿构造;第四期构造变形则以区域性隆升作用为主,使早期褶皱发生横弯褶皱的同时,还将深部形成的金矿体抬升至浅部。文中在成矿控矿构造研究的基础上,探讨了矿床成矿规律,提出了找矿远景。 相似文献
18.
In the high‐grade (granulite facies) metamorphic rocks at Broken Hill the foliation is deformed by two groups of folds. Group 1 folds have an axial‐plane schistosity and a sillimanite lineation parallel to their fold axes; the foliation has been transposed into the plane of the schistosity by these folds. Group 2 folds deform the schistosity and distort the sillimanite lineation so that it now lies in a plane. Both groups of folds are developed as large folds. The retrograde schist zones are zones in which new fold structures have formed. These structures deform Group 1 and Group 2 folds and are associated with the formation of a new schistosity and strain‐slip cleavage. The interface between ore and gneiss is folded about Group 1 axial planes but about axes different from those in the foliation in the gneiss. On the basis of this, the orebody could not have been parallel to the foliation prior to the first recognizable structural and metamorphic events at Broken Hill. The orebody has been deformed by Group 2 and later structures. 相似文献
19.
太行山南段自立庄韧性剪切带变形特征 总被引：1，自引：0，他引：1
太行山南段临城自立庄地区古元古界甘陶河群中低级变质岩中发育一条左行逆冲型韧性剪切带。自立庄韧性剪切带出露长约10 km,宽约1 km,走向NNE,往西缓倾,在EW方向上由若干条强变形带与其间的弱变形域或岩块组成,平面上呈现平行式的组合特征。该韧性剪切带内发育糜棱岩、拉伸线理和皱纹线理、不对称褶皱、石香肠构造和构造透镜体、S-C面理和旋转碎斑等宏观和微观构造。S-C面理、旋转碎斑、不对称褶皱等宏微观变形特征一致表明自立庄韧性剪切带上盘由西往东逆冲的运动学性质。在对韧性剪切带宏观、微观构造特征研究基础上,结合区域资料,认为自立庄韧性剪切带的形成与华北克拉通古元古代末期西部陆块与东部陆块的EW向碰撞拼合有关,是18.5 Ga吕梁运动的产物。自立庄韧性剪切带的厘定为太行山南段古元古代构造演化提供了基础资料。 相似文献