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石灰石矿山采场崩塌是藏东昌都地区常见的地质灾害类型, 是矿山企业安全生产和铁路工程建设面临的主要地质安全问题之一。文章采用基础地质、构造地质和灾害地质相结合的方法, 通过详实的地质灾害调查, 查明崩塌发育规律, 分析岩体结构面特征, 探讨崩塌灾害的形成机理, 并建立其破坏模式。结果表明: 藏东昌都地区上三叠统石灰石矿山采场崩塌沿区内褶冲带呈线状展布; 岩体内发育纵张节理(S1)、横张节理(S2)、"X"型共轭剪节理(S3、S4)及层间剪节理(S5)共5组与区域褶皱和对冲系断裂配套的陡倾构造结构面, 将岩体切割为破碎的块体; 研究区崩塌地质灾害是内、外动力地质作用耦合的产物。晚三叠世(T3)早期, 昌都地区陆内裂谷盆地环境沉积形成的上三叠统波里拉组(T3b)灰岩是崩塌发育的沉积建造基础; 新生代(Cz)印度-欧亚大陆碰撞引发的强烈褶皱造山运动奠定了区内构造格架, 是崩塌发育的必要条件; 第四纪(Q)以来的强烈新构造运动和晚更新世(Q3)以来的湿-热气候频繁交替、充沛降雨、现代人类活动等做为内和外动力的耦合作用是崩塌灾害的主要诱发因素。研究区内崩塌灾害存在倾倒式、坠落式和滑移式3种破坏模式。研究成果对岩溶区崩塌灾害防治与相关铁路建设具有一定指导意义。 相似文献
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辽东地区构造上位于辽中—吉南元古宙活动带西南部,为胶辽克拉通金矿床分布比较集中的地区。金矿化作用发生于古元古宙变质沉积岩和花岗片麻岩的韧性及脆-韧性剪切带之中,剪切活动与成金事件具同时性关系。矿化剪切带分为3大系统,其中近东—西向和北东—南西向两大系统发育于辽河群分布区,其受控于岩石非均匀性,分别借助于早(吕梁)期S1(≈S0)和S2或D3剪切带而形成,剪切活动(构造事件)与成金事件主要发生于印支运动;丹东韧性剪切带及其相关构造为本区最重要的含矿系统,矿床均顺主构造线分布,并规律性地受控于其次级构造,剪切带的形成和成金事件均在燕山运动时期。本区提供了一个特殊的克拉通成矿作用格局:容矿岩石时代老,成金事件时代新。 相似文献
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琼东南盆地中东部三亚组层序构成及有利区带预测 总被引：3，自引：0，他引：3
三亚组为琼东南盆地中东部②号断裂带地区重要的勘探目的层段之一.运用地震资料并结合钻井等其他资料, 将三亚组划分为2个三级层序: S60—S52、S52—S50, 并指出这2个层序发育的背景为挠曲双陆架坡折型.其中S60—S52层序表现出断拗转换阶段的特征, S52—S50层序则为隐伏断裂控制的挠曲坡折的特征.层序内体系域的发育受上述层序地层格架的控制, 下切谷、斜坡扇等低位体在S60—S52层序内较发育, 前积楔、斜坡扇等低位体在S52—S50层序内较发育.2个层序内海侵和高位体系域均受双坡折带控制, 并可划分出滨浅海陆架、陆坡和深海-半深海等沉积体系.指出了②号断裂带三亚组内的有利勘探区带. 相似文献
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北京西山中新生代多期次变形强烈,是探讨华北板块构造演化的重要窗口.构造解析及EBSD组构分析表明,黄院奥陶系发育4个期次变形,第2期NE-SW向挤压变形为主体构造样式.第1期为顶面指向SEE的简单剪切,透入性面理S1已基本置换层理S0,伴生110°~120°缓倾拉伸线理;自北向南,第2期变形可划分为纵弯褶皱亚带和逆冲剪切亚带,褶皱倒伏趋势和剪切条带显示上盘向SW逆冲;第3期为沿面理S2发生的NNW向正断层式滑脱,第4期为近N-S向陡倾正断层系.依据卷入变形的闪长岩脉最年轻锆石U-Pb年龄峰值（~116 Ma）,结合区域地质资料,认为:（1）黄院奥陶系第1期SEE向剪切时代为早白垩世晚期;（2）第2期晚白垩世NE-SW向挤压变形形成于燕山运动晚期,可能与蒙古-鄂霍茨克洋关闭之后的陆陆汇聚相关. 相似文献
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南冈底斯岩浆岩带出露的一套早—中侏罗世火山-沉积建造经历了多期构造变形,致使这套火山-沉积层序发生了强烈的面理置换,形成了典型的构造-岩石地层。依据造山带地层划分方法将叶巴火山弧厘定为叶巴岩群,并根据内部岩性组合特征和构造变形特征将其进一步划分为邦堆岩组、叶巴岩组、甲玛岩组。运用构造解析原理划分了3期构造变形事件。第一期构造变形为脆-韧性剪切变形,剪切方式为纯剪占优的一般剪切变形,透入性面理S1普遍置换层理S0(S1∥S0),伴生倾伏向85°~100°陡倾的拉伸线理,运动学指示顶面朝西运动,存在左行和右行两个方向的剪切旋转碎斑共存的现象;EBSD实验结果显示变形的温度≤380 ℃,石英颗粒细粒化明显,重结晶方式为亚颗粒旋转重结晶;40Ar-39Ar年代学结果表明该期构造变形时代约为79 Ma,其可能代表新特提斯洋板片低角度(平板式)俯冲引起在弧后挤压背景下形成的挤出构造。第二期构造变形表现为S1面理发生纵弯褶皱变形形成的轴面劈理S2,轴面产状倾向北或南,倾角40°~70°,枢纽向西或北西西倾伏;结合区域地质演化特征,认为其可能是在晚白垩世(79~68 Ma)南北向持续的挤压应力条件下,南冈底斯弧后盆地整体向上挤出,引发上地壳缩短、加厚进而导致褶皱作用的发生。第三期主要为浅层次膝折构造和近东西向正断层,最大主压应力方向为铅直向,最小主压应力方向(伸展方向)为近南北向;结合区域构造演化特征,认为该期变形可能代表渐新世末—中新世初期(23.74~21.1 Ma),印度岩石圈或青藏高原岩石圈或两者组合的拆沉作用引起冈底斯岩基隆升(主要动力学机制)和GCT活动并共同作用导致近南北向伸展滑覆事件发生。 相似文献
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澜沧群变质变形过程的厘定有助于揭示澜沧江构造带的演化历史.通过对双江-惠民地区出露的中-低绿片岩相变质岩系与高压变质岩系的"构造-变质"双重解析,发现澜沧群变质岩系:（1）以挤压体制下的褶劈理S2为区域性面理,浅变质岩系中石英脉条带代表的面理S1与层理S0产状一致,并在第2期强烈压扁后与S2近平行;（2）构造样式与变质变形期次在研究区域内基本一致,表现为二叠纪-三叠纪两期次中深构造层次透入性变形为侏罗纪-新生代浅-表层次变形所叠加;（3）高压变质岩记录了两个期次的深层次构造变形,电气石与石榴石变斑晶具有明显的两阶段生长模式,核部（M1aD1a）可能代表了峰期榴辉岩相变质作用,边部代表折返过程中的蓝片岩相（M1bD1b）阶段.高压变质岩与浅变质岩第2期（M2D2）构造层次及变形样式一致,代表折返后的挤压拼贴过程,两者的剪切型褶劈理S2均指示上盘S向的剪切滑动.结合新生代三江地区发生的近90°块体旋转,恢复第2期为上盘指向E的逆冲剪切作用.通过对幸福变质石英砂岩白云母、小黑江多硅白云母和蓝闪石的40Ar-39Ar定年,以及对前人小黑江蓝闪石40Ar-39Ar年龄的重新解释,共厘定出澜沧群4个构造阶段:（1）高压变质岩第1期晚期（D1b）蓝片岩相变质作用（~250 Ma）;（2）第2期（M2D2）中层次挤压（215~214 Ma）;（3）浅变质岩系第3期早期（D3a）N-S向纵弯褶皱（111.9~103.7 Ma）与晚期（D3b）逆冲（~82.28 Ma）;（4）第4期近E-W向纵弯褶皱（新生代,很可能晚于59.18 Ma）. 相似文献
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中原邙山黄土地层划分的讨论 总被引：1，自引：1，他引：0
地层时代和地层划分研究一直是基础性、先导性工作,随着科学研究的深入和材料的丰富,地层划分不断被重新认识。黄土地层时代和划分主要依靠OSL、14C、古地磁和磁化率的对比。中原邙山因发育巨厚的马兰黄土而闻名中外,但地层划分却出现了不同的认识。早期对赵下峪剖面的研究认为L1层厚98 m,并发育L1SS1弱古土壤层;剖面底部出露最老地层为S10层。后来的观点把早期的L1层划分为L1、S1、L2层,剖面底部出露最老地层为S11层。通过对B/M界线进行详细的古地磁研究,剖面上部补充年代测试样品,结合已有测年结果,分析认为早期对L1的划分和对剖面最老地层的确认是正确的,但B/M界线位置划分有误;而后期的研究对B/M界线位置的划分是正确的,但把底部最老地层划分为S11是不当的,同时把马兰黄土中弱古土壤层L1SS1划分为S1也是不合适的。地层对比表明,邙山黄土发育了S0—S10黄土—古土壤序列,B/M界线位于L8下部。 相似文献
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钴矿是重要的战略性金属矿产资源之一,对其成矿作用(如构造与成矿的关系)进行深入的研究能为前期指导找矿提供理论依据。本文对中国东部吉林白山市三道沟镇三岔河村大横路Cu-Co矿开展了相关工作,包括野外构造解析、钻孔-岩芯资料分析、钻孔薄片综合矿物分析系统(TIMA)实验和区域相关岩石年代学等。构造解析显示大横路Cu-Co矿围岩变形包括层片交切、S1面理和褶劈理等构造要素。钻孔-岩芯资料分析矿区发育大量F2紧闭褶皱、逆冲断层及断层相关褶皱、倒转褶皱F2等。钻孔、探槽薄片样品TIMA实验显示含Co流体大量富集于低角度逆冲断裂、倒转褶皱韧性剪切域和断层相关褶皱转折端处。这些工作显示走向为NE的低角度逆冲断裂及断层相关褶皱对大横路Cu-Co矿的富集起到关键的控制作用。相关年代学工作,结合前人研究及大量区域地质资料表明:(1)矿区内逆冲断层及褶皱等控矿构造要素为古元古代构造事件的产物;(2)中生代构造事件对成矿作用的制约(Cu-Co矿的再富集)可能来自于白垩纪大规模的伸展作用。 相似文献
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襄樊——广济断裂西段的三里岗——三阳地区出露有构造混杂岩,以含蛇绿岩残块为特征,经历了复杂的构造变形和演化过程。不同区段的构造解析与对比表明,中生代以来该构造混杂岩带主要遭受了4期变形构造的叠加改造:1)高温塑性变形(D1),表现为蛇绿岩残块内部具网状强应变带和透镜状弱应变域相互交织的构造变形样式,强应变带形成以镁铁质糜棱岩为特征的高温韧性剪切带,显示深层次构造变形特征;2)逆冲推覆变形(D2),构造混杂岩带发育叠瓦状逆冲推覆构造和双冲构造,南界韧性剪切带是构造混杂岩带整体运移的主推覆面,发育长英质糜棱岩,形成于中等构造层次,岩石中发育镁铁质糜棱岩糜棱面理的褶皱构造,显示陆内逆冲推覆对先期高温塑性变形构造的叠加改造;3)韧脆性右行平移剪切(D3),形成构造混杂岩带内部浅层次构造变形,构造混杂岩带南侧的花山群钙质片岩揉皱变形,形成枢纽近直立的不对称褶皱,指示右行平移剪切变形;4)伸展正断层(D4),主要发育于构造混杂岩带北侧,呈NW——SE向展布,控制晚白垩世断陷盆地的形成与沉积充填。 相似文献
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河北坝上地区位于东亚季风气候边缘区,对气候变化响应敏感。丰宁黄土剖面为研究该区域长时间尺度的环境演化提供了理想材料。通过丰宁黄土剖面地球化学元素和磁化率分析,结合光释光测年结果,恢复了该地区230,ka BP以来的环境演化历史; 通过野外观察,识别出了S1古土壤之下发育的风化淋滤黄土层,探讨了S1古土壤发育时期的风化淋滤特征及其所揭示的气候变化问题。结果表明: (1)230,ka BP以来的磁化率记录可与深海氧同位素3—8阶段进行细节上的对比,表明丰宁黄土堆积区对全球气候变化有着积极的响应;(2)S1古土壤发育时期,由于受到强降水的影响,土壤中元素受到强烈淋溶从而向下迁移到L2黄土中,造成L2上部地球化学记录与磁化率的差异;(3)从S1古土壤顶部到钙结核层之间土壤属于酸性淋溶土,可能相当于现今中国北亚热带的黄棕壤,其剖面由土壤层、风化淋滤黄土层和CaCO3淀积层构成;(4)S1古土壤发育时期的温度和降水量与现今江苏泗洪和六合地区相当,表明当时研究区为亚热带气候。 相似文献
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The Horto-Baratinha (HBD) iron ore deposit is located at the eastern border of São Francisco Craton, comprising BIF-hosted high-grade bodies (>60 wt.% Fe) associated with polydeformed quartz-mica-schists, amphibole-schist of Statherian maximum deposition age, enclosed by Statherian granitoids of the Borrachudos Suite and Neoarchean gneiss. All the sequence is crosscut by undeformed dikes and sills of pegmatitic bodies probably formed during Late Ediacaran-Cambrian. The metasedimentary sequence is stratigraphically correlatable with the Orosirian-Statherian Serra da Serpentina and Serra de São José Groups that comprise the basal units of the Espinhaço Supergroup and was intensively segmented into distinct tectonic blocks. The sedimentary/diagenetic bedding of the metamorphosed BIF (itabirite) is generally transposed by an axial planar schistosity. The lamellar hematite from itabirite is the oldest iron oxide generation, which was formed during the syn-deformational stage, parallel-oriented to the rock foliation. The (keno)magnetite grains from itabirite, iron ore and pegmatite bodies developed as idioblasts that grew over the foliation formed during late and post-deformational stages. Magnetite oxidizes subsequently to martite and granular hematite. Coarse lamellar hematite crystals randomly oriented in the border of the pegmatitic bodies also formed during the post-deformational stage due to hydrothermal reaction with itabirite. The country rocks have undergone at least three stages of deformation developed during the syn-collisional and late-collisional (Ediacaran to early-Cambrian) phases of the Brasiliano Orogeny: stage 1 with the development of a pervasive foliation (S1), parallel to axial plane to tight folds and transposition of all sedimentary structures; stage 2 with folding of S1; stage 3 with refolding of S1. Both fold systems interfere with each other making up a dome and basin refolding shape. During the late-collisional (Ediacaran to early-Cambrian) and post-collisional/gravitational collapse (Cambrian) the sequence was intruded by anatectic pegmatitic bodies, which are part of the Eastern Brazilian Pegmatite Province, one of the most significant pegmatitic regions worldwide. The fluid related with these intrusions could be related with the Si leaching, crystallization of magnetite and granular hematite, and consequent formation of high-grade iron bodies. 相似文献
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山西太古代——中生代构造应力场 总被引：9，自引：0，他引：9
本文采用历史分析与力学分析相结合的原则,研究山西太古代至中生代五次主要构造运动的形变特征、主应力方向及分布规律。中太古代晚期（阜平运动）以SSW向挤压为主;晚太古代末期（五台运动）、早元古代末期（吕粱运动）和侏罗纪（燕山运动）受SE—SEE向挤压;白垩纪（四川运动）以SSW向挤压为特征。五次构造运动的最大主压应力均呈近水平方向。 相似文献
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Asghar ALI Umer HABIB Atta Ur REHMAN Noor ZADA Zain Ul ABIDIN Muhammad ISMAIL 《《地质学报》英文版》2016,90(2):440-455
Two well-developed mesoscopic folds, D_2 and D_3, which postdate the middle amphibolite metamorphism, were recognized in the western hinterland zone of Pakistan. NW–SE trending D_2 folds developed during NE–SW horizontal bulk shortening followed by NE–SW trending D_3 folds, which developed during SE–NW shortening. Micro- to mesoscopically the NW–SE trending S2 crenulation cleavage, boudins and mineral stretching lineations are overprinted by D_3. The newly established NW–SE trending micro- to mesoscopic structures in Munda termed D_2, which postdated F_1/F_2, is synchronously developed with F3 structures in the western hinterland zone of Pakistan. We interpret that D_2 and D_3 folds are counterclockwise rotated in the tectonic event that has evolved the Hazara Kashmir Syntaxis after the main phase Indian plate and Kohistan Island Arc collision. Chlorite replacement by biotite in the main matrix crenulation cleavages indicates prograde metamorphism related with D_2. The inclusion of muscovite and biotite in garnet porphyroblasts and the presence of staurolite in these rocks indicate that the Barrovian metamorphic conditions predate D_2 and D_3. We interpret that garnet, staurolite and calcite porphyroblasts grew before D_2 because the well developed S2 crenulation cleavage wraps around these porphyroblasts. 相似文献
18.
B. G. Golionko E. V. Vatrushkina V. E. Verzhbitsky K. E. Degtiarev 《Doklady Earth Sciences》2017,475(1):719-723
Detailed structural investigations were carried out in the Pevek area in order to verify the tectonic evolution of the Mesozoic thrust and fold belt in Chukotka. South-vergent F1 folds in Triassic rocks were proved to be the earliest structures formed during the first deformation stage DI. These structures were deformed by north-vergent folds F2 that were formed during the second deformation stage DII. North-vergent folds are the main structures of the Jurassic–Lower Cretaceous complex. The fold structures of the first two stages are deformed by shear folds F3 finishing the stage DII. All these structures are deformed by submeridionally trending normal faults referred to the deformation stage DIII. 相似文献
19.
《Gondwana Research》2003,6(2):215-229
Interpretation of satellite data in combination with regional field traverses, delineating the major structural features such as the Nagavali and Vamsadhara Shear Zones and associated fold patterns, provides a synoptic picture of the regional tectonic framework of the central part of the Eastern Ghats Mobile Belt. The complex geology of the study area can broadly be grouped into three distinct deformational events. D1 fabrics represented by near flat-lying gneissic foliations, paralleling the lithological banding are best preserved in low strain domains and are related to Middle to late Archaean thrusting (3000-2600 Ma). The second deformational event D2 is characterized by the development of shear zones and associated mylonitic fabrics and magmatism probably during 1450-850 Ma. The Pan-African thermal (500-550 Ma) overprint is restricted to shear zones in the form of reworking. Regionally, the central part of the Eastern Ghats Mobile Belt can be divided into five distinct structural domains based on structural geometry of folds, foliations and lineations. A three-dimensional block diagram of the Nagavali and Vamsadhara Shear Zones involving fold-thrust tectonics associated with westward thrusting is presented here. A correlation of Pan-African Shear Zones in adjacent continents wrapping around the Archaean Dharwar Craton in the reconstruction of Rodinia and East Gondwana supercontinent suggests an east-west convergence. 相似文献
20.
The Agnew supracrustal belt consists of a greenstone sequence (interlayered metabasalt, differentiated gabbroic sills, ultramafic bodies, and black volcanogenic sediment) unconformably overlain by granitoid-clast conglomerate and meta-arkose. The base of the preserved sequence is intruded by grey tonalite with a crudely concordant upper contact, and by small discordant bodies of leucogranite.An early deformation (D1) produced isoclinal folds and a regional penetrative foliation. These structures were probably gently dipping when formed. D2 produced large-scale NNW-trending upright folds, a regional foliation, and a vertical N-trending ductile fault on the west side of the belt. D2 structures indicate a combination of ENE-WSW shortening, and right-lateral shear along the ductile fault. Both D1 and D2 were accompanied by metamorphism under upper greenschist to lower amphibolite facies conditions.The interpreted sequence of tectonic events is (1) deposition of the greenstone sequence on an unknown basement; (2) intrusion of large volumes of tonalite, separating the supracrustal rocks from their basement; (3) erosion of mafic rocks and tonalite to produce the clastic sedimentary sequence; (4) the first deformation; (5) intrusion of small volumes of leucogranite; (6) the second deformation.The bulk of the granitoid rocks were emplaced before the first recognisable deformation. Thus the granitoid magma cannot have been produced by partial melting of previously downbuckled ‘greenstone belt’ rocks, nor can the large-scale upright folds (D2) be a result of forceful emplacement of the magma — two common postulates for Archaean terrains. The D2 folds are closely related to the ductile fault bounding the zone: these structures, which give the present N-trending tectonic belt its form, are the youngest features in the terrain. 相似文献