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1.
喜马拉雅造山带是地球上海拔最高、规模最大的陆陆板块俯冲碰撞带在这条长达2 500 km的板块边界上,近年来多次发生破坏性地震,造成大规模的滑坡、房屋倒塌等次生灾害,给人民生命和财产安全造成严重的威胁。分别选取尼泊尔喜马拉雅、喜马拉雅东构造结和喜马拉雅西构造结地区近期发生的3个地震震群作为研究实例,基于中国科学院青藏高原研究所在研究区架设的区域流动地震台站记录的波形资料,对地震的震源位置和震源机制解进行计算。结果表明,在尼泊尔喜马拉雅地区,主喜马拉雅逆冲断裂是大地震的主要发震构造;东构造结地区的地震以逆冲和走滑型为主,表明印度板块向北东方向的逆冲推覆和青藏高原向东南逃逸的侧向挤出是该地区的主要构造背景;西构造结地区中深源地震多发,揭示了高角度大陆深俯冲的几何形态。 相似文献
2.
中国大陆构造及动力学若干问题的认识 总被引：17，自引：2，他引：15
中国(东亚)大陆受特提斯、古亚洲和太平洋构造体系的制约,具有复杂的地体构架和特殊的岩石圈结构。本文从地学前沿——大陆动力学的视野出发,围绕中国大陆构造及动力学四个方面的研究,总结已有的进展并提出新的思考:①中国大陆板块下的构造和整个地幔运动的构架:地震层析资料揭示西太平洋板片向西俯冲到东亚大陆之下,其倾角逐渐减小,最后近水平地插进400～600km深度的地幔过渡带中,成为箕状几何形态的超深俯冲板片。印度岩石圈板片超深俯冲至青藏高原之下～800km的深度,在喜马拉雅西构造结部位发生双向不对称深俯冲,印度岩石圈板片向东俯冲至东构造结东侧之下300～500km的深度。②中国大陆变质基底的再活化:中国大陆的大部分陆块未受显生宙以来构造、变质和岩浆事件的改造与激活,在冈瓦纳大陆北缘的印度陆块和阿拉伯陆块北缘还发育有形成于泛非期(530～470Ma)的造山带,其影响范围至高喜马拉雅、拉萨地体和三江地区。新生代的变质活化普遍出现在喜马拉雅、南迦巴瓦、拉萨地体和三江-缅甸地区,最新的变质年龄仅2～1Ma(南迦巴瓦)。③中国主要高压-超高压变质带的大地构造背景及深俯冲-折返机制:中国及邻区含榴辉岩的高压-超高压(HP/UHP)变质带有洋壳(深)俯冲和陆壳(深)俯冲之分。青藏高原中,大部分洋壳俯冲形成的高压/超高压变质带与原-古特提斯洋盆中诸多微陆块之间的小洋盆的汇聚碰撞有关,陆壳深俯冲作用有两种机制,它们分别是大陆块之间剪式碰撞和撕裂式岩石圈舌形板片的深俯冲。④中国大陆造山带的深部物质可经3类机制挤出,即深部地壳物质"牙膏式"挤出、侧向挤出和"挤压转换式"挤出。 相似文献
3.
亚洲东部存在一个巨大的三角形地震构造区域,大体上,喜马拉雅山脉、帕米尔—天山—阿尔泰山—贝加尔和东经105°线是它的3个边界,主要覆盖中国和蒙古国西部众多高原、山脉及山间盆地。三角区内现今构造活动和地震广泛强烈,地壳破碎,显示不均匀的块体边界和块内变形;区外基本上是稳定的刚性陆块,地震很少,变形较弱,处于整体缓慢运动之中。这个宽阔的板内变形区起源于印度、菲律宾海—西太平洋和欧亚三大板块之间的动力作用以及深部地幔流的影响。向北快速运动的印度次大陆已近水平地插入到西藏板块下,沿喜马拉雅弧产生多种运动和变形,并向亚洲内部远距离地扩散。沿东经95°～100°,向北的地壳运动向东和东南方向偏转,阻截了喜马拉雅弧东端的北向运动;而在喜马拉雅弧西端,帕米尔继续向北挤进中亚,受天山—阿尔泰山—贝加尔一线西北側稳定地壳的限制,扩散的变形被中国、蒙古、俄罗斯边境地区一系列EW向和NW向的老断层吸收并在它们的西端终止。菲律宾海—西太平洋向欧亚大陆的消减-俯冲导致沿海沟-岛弧的漫长而狭窄的地震带,但对亚洲大陆的水平挤压较小,未能阻挡亚洲大陆东部向东移动。其部分原因可能是俯冲板片受到来自欧亚大陆下的ES向地幔流的推挤,这个ES向地幔流与来自印度下面的N向地幔流在西藏中部汇合并向东偏转,在大尺度上与GPS观测到的地表移动图像一致。 相似文献
4.
5.
青藏高原东缘旋转变形机制的数值模拟 总被引：1，自引：0，他引：1
在印度板块与欧亚板块的碰撞作用下,青藏高原受到华南块体、鄂尔多斯块体等不同程度的阻挡,引起高原的整体隆升。青藏高原东南缘发生物质向南"逃逸",青藏高原东缘现今的地壳运动表现为围绕青藏高原东构造结发生顺时针的旋转。针对青藏高原东缘的旋转变形特征,基于以大型活动断裂为界的块体构造模型,利用粘弹性接触单元有限元模拟,分析了控制青藏高原东缘旋转变形的动力学环境,模拟的GPS速度与实测GPS速度能够较好的地吻合,构造应力场分布特征和活动断层的性质也能够较大程度地吻合,模拟过程采用的边界及其代表的动力学环境表明,青藏高原东缘整体受控于印度板块的持续碰撞和稳定的华南板块的阻挡,在下地壳的拖曳和重力作用下,青藏高原物质从南部边界"逃逸"。在"逃逸"过程中,受印度板块斜向俯冲作用的影响,沿实皆断裂缅甸板块对巽他板块的剪切拉升作用是形成围绕喜马拉雅东构造结的旋转运动和地壳变形的重要因素,也是青藏高原东南缘旋转活动构造体系的主要影响因素之一。 相似文献
6.
大陆岩石圈深俯冲作用是地球科学领域的前沿热点,榴辉岩的折返机制是板块构造及动力学的关键科学问题。全球著名的大陆造山带中榴辉岩的p-T轨迹呈现差异性折返特征,为了揭示榴辉岩的折返机制,本文结合变质岩石学和地球物理学研究,选取3个典型大陆造山带——中生代—新生代的阿尔卑斯造山带、中生代的苏鲁—大别造山带和新生代的喜马拉雅造山带中的榴辉岩进行阐述。在阿尔卑斯造山带地区,地球物理研究结果发现,欧洲板块的俯冲造成了Adria地区下方的岩石圈存在明显厚度差异。同时,阿尔卑斯造山带Doria Maria和Pohorje地区以及Pohorje地区内部,榴辉岩折返历史也不尽相同,原因可能是亚德里亚大洋岩石圈断离后不同期次的逆冲推覆作用使其差异性斜向挤出。苏鲁—大别造山带中榴辉岩的快速折返,原因可能是华南板块与华北板块碰撞后岩石圈的拆沉或断离作用。在喜马拉雅造山带,西构造结和中喜马拉雅榴辉岩的折返存在差异性。在西构造结,那让和卡甘榴辉岩呈现不同的p-T轨迹和折返速率,变质岩石学和地球物理研究结果都表明它们的差异性折返很可能与印度-欧亚大陆碰撞过程中的构造挤压作用以及印度大陆岩石圈的断离作用有关。喜马拉雅造山带是年轻的正在进行造山活动的造山带,相较于古老的苏鲁-大别造山带,它更适合变质岩石学和地球物理学的综合研究。因此西构造结高压/超高压榴辉岩的折返机制——构造挤压和俯冲板块断离可应用于全球造山带。 相似文献
7.
东喜马拉雅构造结快速隆升时间以及雅鲁藏布江和伊洛瓦底江是否曾经相连已经争论了超过半个世纪. 采用锆石U-Pb年代学等方法,对缅甸中央盆地新生代地层的“源?汇”路径开展研究. 缅甸中央盆地始新统发育大量铬尖晶石、各坳陷的锆石年龄谱各不相同,表明该时期沉积物以盆地周边隆起为主要物源,不存在统一的源区;渐新世之后,源自区域变质岩的重矿物组合比例逐渐增加,盆地各坳陷碎屑锆石年龄谱特征趋于一致,均以40~ 70 Ma的主峰以及80~110 Ma次峰为特征,表明沉积物源区进入抹谷变质带,伊洛瓦底江雏形已经形成;由于缅甸中央盆地渐新统至下中新统完全没有喜马拉雅造山带信息,认为该时期雅鲁藏布江?伊洛瓦底江并未相连. 晚中新世?更新世,喜马拉雅造山带特征组合十字石和蓝晶石以及110~130 Ma年龄峰的出现,表明伊洛瓦底江已经侵蚀到东喜马拉雅构造结,达到现今流域规模. 因此,东喜马拉雅构造结快速隆升的时间大约在晚中新世. 相似文献
8.
Tethyan and Indian subduction viewed from the Himalayan high- to ultrahigh-pressure metamorphic rocks 总被引：13，自引：0，他引：13
The Himalayan range is one of the best documented continent-collisional belts and provides a natural laboratory for studying subduction processes. High-pressure and ultrahigh-pressure rocks with origins in a variety of protoliths occur in various settings: accretionary wedge, oceanic subduction zone, subducted continental margin and continental collisional zone. Ages and locations of these high-pressure and ultrahigh-pressure rocks along the Himalayan belt allow us to evaluate the evolution of this major convergent zone.
(1) Cretaceous (80–100 Ma) blueschists and possibly amphibolites in the Indus Tsangpo Suture zone represent an accretionary wedge developed during the northward subduction of the Tethys Ocean beneath the Asian margin. Their exhumation occurred during the subduction of the Tethys prior to the collision between the Indian and Asian continents.
(2) Eclogitic rocks with unknown age are reported at one location in the Indus Tsangpo Suture zone, east of the Nanga Parbat syntaxis. They may represent subducted Tethyan oceanic lithosphere.
(3) Ultrahigh-pressure rocks on both sides of the western syntaxis (Kaghan and Tso Morari massifs) formed during the early stage of subduction/exhumation of the Indian northern margin at the time of the Paleocene–Eocene boundary.
(4) Granulitized eclogites in the Lesser Himalaya Sequence in southern Tibet formed during the Paleogene underthrusting of the Indian margin beneath southern Tibet, and were exhumed in the Miocene.
These metamorphic rocks provide important constraints on the geometry and evolution of the India–Asia convergent zone during the closure of the Tethys Ocean. The timing of the ultrahigh-pressure metamorphism in the Tso Morari massif indicates that the initial contact between the Indian and Asian continents likely occurred in the western syntaxis at 57 ± 1 Ma. West of the western syntaxis, the Higher Himalayan Crystallines were thinned. Rocks equivalent to the Lesser Himalayan Sequence are present north of the Main Central Thrust. Moreover, the pressure metamorphism in the Kaghan massif in the western part of the syntaxis took place later, 7 m.y. after the metamorphism in the eastern part, suggesting that the geometry of the initial contact between the Indian and Asian continents was not linear. The northern edge of the Indian continent in the western part was 300 to 350 km farther south than the area east of the Nanga Parbat syntaxis. Such “en baionnette” geometry is probably produced by north-trending transform faults that initially formed during the Late Paleozoic to Cretaceous Gondwana rifting. Farther east in the southern Tibet, the collision occurred before 50.6 ± 0.2 Ma. Finally, high-pressure to ultrahigh-pressure rocks in the western Himalaya formed and exhumed in steep subduction compared to what is now shown in tomographic images and seismologic data. 相似文献
9.
试论江南造山带西南段构造演化--以黔东及邻区为例 总被引：9，自引：2，他引：9
江南造山带西南段，黔东及邻区，位于扬子陆块与华南陆块的过渡区，发育中、新元古代至新生代地层和多种类型的岩浆岩、变质岩，存在多期次构造运动，可划分出洋陆转换阶段的武陵构造旋回期、加里东构造旋回期和板内活动阶段的海西一燕山构造旋回期、喜马拉雅构造旋回期。具有从洋陆转换阶段的B型俯冲造山向板内活动阶段的A型俯冲造山演化、从活动型地壳向稳定型地壳的演化历程，是一个由不同时期、不同性质的造山作用构成的复合造山带，反映出扬子陆块向东南增生及江南造山带向东南迁移的演化历史。 相似文献
10.
Post-collisional crustal extension setting and VHMS mineralization in the Jinshajiang orogenic belt, southwestern China 总被引：2，自引：0，他引：2
Hou Zengqian Wang Liquan Khin Zaw Mo Xuanxue Wang Mingjie Li Dingmou Pan Guitang 《Ore Geology Reviews》2003,22(3-4):177-199
The Jinshajiang orogenic belt (JOB) of southwestern China, located along the eastern margin of the Himalayan–Tibetan orogen, includes a collage of continental blocks joined by Paleozoic ophiolitic sutures and Permian volcanic arcs. Three major tectonic stages are recognized based on the volcanic–sedimentary sequence and geochemistry of volcanic rocks in the belt. Westward subduction of the Paleozoic Jinshajiang oceanic plate at the end of Permian resulted in the formation of the Chubarong–Dongzhulin intra-oceanic arc and Jamda–Weixi volcanic arc on the eastern margin of the Changdu continental block. Collision between the volcanic arcs and the Yangtze continent block during Early–Middle Triassic caused the closing of the Jinshajiang oceanic basin and the eruption of high-Si and -Al potassic rhyolitic rocks along the Permian volcanic arc. Slab breakoff or mountain-root delamination under this orogenic belt led to post-collisional crustal extension at the end of the Triassic, forming a series of rift basins on this continental margin arc. Significant potential for VHMS deposits occurs in the submarine volcanic districts of the JOB. Mesozoic VHMS deposits occur in the post-collisional extension environment and cluster in the Late Triassic rift basins. 相似文献
11.
Structural and Chronological Evidence for the India-Eurasia Collision of the Early Paleocene in the Eastern Himalayan Syntaxis, Namjagbarwa 总被引：3，自引：0，他引：3
ZHANG Jinjiang JI Jianqing Department of Geology Peking University Beijing ZHONG Dalai SANG Haiqing HE Shundong Institute of Geology Geophysics Chinese Academy of Sciences Beijing 《《地质学报》英文版》2002,76(4):446-454
The eastern Himalayan syntaxis in Namjagbarwa is a high-grade metamorphic terrain formed by the India-Eurasia collision and northward indentation of the Indian continent into Asia. Right- and left-lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug-Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left-lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar-Ar chronological study shows that the age of the early deformation in the Dongjug-Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India-Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis. 相似文献
12.
H. N. Srivastava B. K. Bansal Mithila Verma 《Journal of the Geological Society of India》2013,82(1):15-22
The largest earthquake (Mw 8.4 to 8.6) in Himalaya reported so far occurred in Assam syntaxial bend in 1950. However, some recent studies have suggested for earthquake of magnitude Mw 9 or more in the Himalayan region. In this paper, we present a detailed analysis of seismological data extending back to 1200 AD, and show that earthquake in Himalayan region may not be expected to be as large as those of subduction zones. Also, there appears to be a lateral variation in the earthquake magnitude, being lesser in the western syntaxial bend when compared close to the eastern syntaxial bend. This is attributed to the difference in the plate boundary scenario; dominance of strike-slip and thrusting along the western syntaxis as against thrusting and remnant subduction along the eastern syntaxis. 相似文献
13.
中国喜马拉雅构造运动的陆内变形特征与油气矿藏富集 总被引：12，自引：0，他引：12
在前人研究的基础上,结合近年来在油气勘探中不断积累的地质资料和地质认识,提出了中国喜马拉雅构造运动的陆内变形特征及其分布规律受控于小型克拉通板块拼贴的基底结构和印/欧碰撞与太平洋板块俯冲所主导的双重控制因素;喜马拉雅构造运动的发育特征主要表现为三种动力学机制:青藏高原隆升、盆地与造山带体制和东部拉张活动。喜马拉雅构造运动的大地构造格局及其构造变形分布规律集中体现为4个构造域:青藏高原隆升区、环青藏高原盆山体系、稳定区和环西太平洋裂谷活动区。我国沉积盆地在喜马拉雅构造运动中的构造特征分为三种类型:(1)东部渤海湾、松辽等盆地受拉张构造环境控制的裂谷沉降;(2)中部四川、鄂尔多斯等盆地受青藏高原的向东推挤、盆缘冲断、盆内抬升剥蚀;(3)西部的塔里木、准噶尔、柴达木等盆地受青藏高原的向北推挤、冲断挠曲沉降,表现为克拉通单边或双边的压缩挠曲沉降与克拉通内部的冲断隆升沉降等多种盆山耦合形式。喜马拉雅构造运动控制着中国油气晚期定位与富集成藏,主要体现在:盆地的沉积与成藏,形成新生界自生自储的含油气盆地和油气藏;圈闭形成与油气运聚成藏;早期油气藏的调整和再分配;油气藏的破坏。 相似文献
14.
CARBONATITES FROM THE EASTERN HIMALAYAN SYNTAXIS: PETROLOGY AND TECTONIC IMPLICATIONS 总被引：1，自引：1，他引：0
Most carbonatites occur in relatively stable, intra\|plate areas but some are found to occur in near to plate margins and may be linked with plate separation (Woolley, 1989). Although many carbonatites have been discovered to occur in the orogenic belts in recent years, most of these rocks are related to post\|orogenic magmatism, that is, the rocks occur in the specially extensional setting. Therefore it is unusual that such magmatic rocks occur in the typical convergent environment. Here we report carbonatites and associated ultramafic and mafic rocks in the core of the eastern Himalayan syntaxis. The eastern Himalayan syntaxis consists of three tectonic units: the Gangdise, the Yarlung Zangbo, and the Himalayan units, each of which is bounded by faults (Liu & Zhong, 1997). The Himalayan unit, the northernmost exposed part of the Indian plate, is divided into two complexes, the amphibolite facies complex in the south and the granulite facies complex in the north. The granulite facies complex in the Himalayan unit have been argued to experience high\|pressure metamorphism and represent materials buried to upper\|mantle depths (Liu & Zhong, 1997). The carbonatites and associated ultramafic and mafic rocks only occur in the granulite facies rocks and are divided into two belts: northern and southern belts.The northern belt extends at least 30km, and is about 20km in width. The southern belt extends several kilometers, and is 3km or so in width. Each belt consists mainly of differently compositional dykes, extending parallel to gneissosity of granulite facies gneiss. Carbonatitic agglomerates are observed in the northern belt. From the center of carbonatite dykes to country rocks, five types of rock are observed: the center parts of carbonatites, the rim parts of carbonatites, ultramafic and mafic rocks, altered rocks and country rocks. The gneissosity of country rock was deformed by intrusion of dykes. 相似文献
15.
区域变质作用与中国大陆地壳的形成与演化 总被引：8，自引：4，他引：4
在编制1∶500万中国变质地质图的基础上,本文总结了中国主要变质带的演化以及各变质带与中国大陆地壳形成演化之间的内在联系。虽然在华北和华南克拉通都有古太古代到中太古代的变质年代记录,但是由于后期改造其变质作用的特点及与区域构造背景的联系已难以追索。新太古代末-古元古代初期的变质作用在华北克拉通表现最明显,这期变质作用紧随大规模的TTG岩浆作用,普遍具有逆时针的P-T演化轨迹,反映了地幔柱主导的岩浆-变质事件特点。古元古代晚期的变质事件在华北、华南、塔里木克拉通都有强烈反映。这期变质作用以形成具有顺时针P-T演化轨迹的高压麻粒岩为特点,与形成Columbia超大陆的一些造山带的特点类似,但是这三个不同克拉通在与Columbia聚合的时间和空间方位上存在差异。华南克拉通是相对年轻的克拉通,是沿新元古代江南造山带扬子和华夏地块拼合的产物。新元古代江南造山带的火山岩形成时代和变质作用程度从北东向南西迁移,反映了造山过程逐渐迁移和剪刀式闭合的特点。形成华南克拉通后,在其东南缘又先后经历了加里东期和印支期的变质改造,并且由北西向南东变质带从加里东期转变为印支期,但是这两期变质作用的构造背景尚不很清楚。中国南北大陆的聚合首先从西昆仑-阿尔金-北祁连-北秦岭-桐柏开始,所反映的变质作用是早古生代的蓝片岩相和榴辉岩相变质岩相伴产出,表明经历了从洋壳俯冲到陆陆碰撞的演化过程。中国东部的南北大陆到印支期才最终汇聚,相应的变质作用以南部出现高压蓝片岩相、北部出现超高压的榴辉岩相变质带为特点,表明南方大陆向北方大陆的俯冲。超高压带内普遍含有柯石英,意味着大规模的陆壳深俯冲。华北克拉通和塔里木克拉通以北的中亚造山带内存在多条从早古生代到晚古生代的变质带和多条蓝片岩相变质带,表明这是一个由多阶段、多条变质带组成的造山区。但是其变质作用的空间和时间演化还有待进一步深入。青藏高原变质带具有北老南新的空间分布特点,最北部的印支期龙木错-双湖-澜沧江变质带反映了原特提斯和古特提斯洋的碰撞拼合过程,北部的燕山期班公湖-怒江变质带和中部的喜马拉雅早期雅鲁藏布江变质带反映了新特提斯洋的两次碰撞拼合过程,南部喜马拉雅晚期的高喜马拉雅变质带反映了印度板块向北俯冲导致的高原快速隆升过程。 相似文献
16.
We present a review of major gold mineralization events in China and a summary of metallogenic provinces, deposit types, metallogenic epochs and tectonic settings. Over 200 investigated gold deposits are grouped into 16 Au-metallogenic provinces within five tectonic units such as the Central Asian orogenic belt comprising provinces of Northeast China and Tianshan-Altay; North China Craton comprising the northern margin, Jiaodong, and Xiaoqinling; the Qinling-Qilian-Kunlun orogenic belt consisting of the West Qingling, North Qilian, and East Kunlun; the Tibet and Sanjiang orogenic belts consisting of Lhasa, Garzê-Litang, Ailaoshan, and Daduhe-Jinpingshan; and the South China block comprising Youjiang basin, Jiangnan orogenic belt, Middle and Lower Yangtze River, and SE coast. The gold deposits are classified as orogenic, Jiaodong-, porphyry–skarn, Carlin-like, and epithermal-types, among which the first three types are dominant.The orogenic gold deposits formed in various tectonic settings related to oceanic subduction and subsequent crustal extension in the Qinling-Qilian-Kunlun, Tianshan-Altay, northern margin of North China Craton, and Xiaoqinling, and related to the Eocene–Miocene continental collision in the Tibet and Sanjiang orogenic belts. The tectonic periods such as from slab subduction to block amalgamation, from continental soft to hard collision, from intracontinental compression to shearing or extension, are important for the formation of the orogenic gold deposits. The orogenic gold deposits are the products of metamorphic fluids released during regional metamorphism associated with oceanic subduction or continental collision, or related to magma emplacement and associated hydrothermal activity during lithospheric extension after ocean closure. The Jiaodong-type, clustered around Jiaodong, Xiaoqinling, and the northern margin of the North China Craton, is characterized by the involvement of mantle-derived fluids and a temporal link to the remote subduction of the Pacific oceanic plate concomitant with the episodic destruction of North China Craton. The Carlin-like gold metallogenesis is related to the activity of connate fluid, metamorphic fluid, and meteoric water in different degrees in the Youjiang basin and West Qinling; the former Au province is temporally related to the remote subduction of the Tethyan oceanic plate and the later formed in a syn-collision setting. Porphyry–skarn Au deposits are distributed in the Tianshan-Altay, the Middle and Lower Yangtze River region, and Tibet and Sanjiang orogenic belts in both subduction and continental collision settings. The magma for the porphyry–skarn Au deposits commonly formed by melting of a thickened juvenile crust. The epithermal Au deposits, dominated by the low-sulfidation type, plus a few high-sulfidation ones, were produced during the Carboniferous oceaic plate subduction in Tianshan-Altay, during Early Cretaceous and Quaternary oceanic plate subduction in SEt coast of South China Block, and during the Pliocene continental collision in Tibet. The available data of different isotopic systems, especially fluid D–O isotopes and carbonate C–O systems, reveal that the isotopic compositions are largely overlapping for different genetic types and different for the same genetic type in different Au belts. The isotopic compositions are thus not good indicators of various genetic types of gold deposit, perhaps due to overprinting of post-ore alteration or the complex evolution of the fluids.Although gold metallogeny in China was initiated in Cambrian and lasted until Cenozoic, it is mainly concentrated in four main periods. The first is Carboniferous when the Central Asian orogenic belt formed by welding of micro-continental blocks and arcs in Tianshan-Altay, generating a series of porphyry–epithermal–orogenic deposits. The second period is from Triassic to Early Jurassic when the current tectonic mainframe of China started to take shape. In central and southern China, the North China Craton, South China Block and Simao block were amalgamated after the closure of Paleo-Tethys Ocean in Triassic, forming orogenic and Carlin-like gold deposits. The third period is Early Cretaceous when the subduction of the Pacific oceanic plate to the east and that of Neo-Tethyan oceanic plate to the west were taking place. The subduction in eastern China produced the Jiaodong-type deposits in the North China Craton, the skarn-type deposits in the northern margin (Middle to lower reaches of Yangtze River) and the epithermal-type deposits in the southeastern margin in the South China Block. The subduction in western China produced the Carlin-like gold deposits in the Youjiang basin and orogenic ones in the Garzê-Litang orogenic belt. The Cenozoic is the last major phase, during which southwestern China experienced continental collision, generating orogenic and porphyry–skarn gold deposits in the Tibetan and Sanjiang orogenic belts. Due to the spatial overlap of the second and third periods in a single gold province, the Xiaoqinling, West Qinling, and northern margin of the North China Craton have two or more episodes of gold metallogeny. 相似文献
17.
喜马拉雅东构造结是全球构造活动最强烈、地质环境最复杂、地质灾害最频发的地区之一, 工程规划建设面临板块构造带的构造错断、深埋工程灾变、松动山体失稳、流域性地质灾害链等灾难性地质安全风险。如何在活动构造带内选择相对稳定与安全的场址, 实现工程规划建设与运营的地质安全风险最小化, 是当前工程地质领域的重要课题。文章系统梳理了东构造结地区重大地质安全问题, 发现传统的工程选址理论已无法满足喜马拉雅东构造结工程选址的要求, 工程选址面临地质演化过程与工程区地质建造不清、构造活动性与强震灾害风险突出、深部构造应力场与灾变研究薄弱、超高位超远程地质灾害链形势严峻等重大地质安全挑战。为此, 文章从"区域地质演化与工程地质问题" "活动断裂及工程安全风险" "复杂地应力场及工程灾变风险" "流域性地质灾害链工程风险" "东构造结工程选址理论方法"共5个方面提出工程选址主要研究方向, 为完善工程选址风险评价与防控方法提供思路。 相似文献
18.
喜马拉雅造山带东构造结拉布拉多期和格林威尔期造山作用的记录 总被引：6，自引：6，他引：0
位于喜马拉雅东构造结西北部的南迦巴瓦复合体,是构造应力最强、隆升和剥蚀最快、新生代变质和深熔作用最强的地区。为厘定该地区早期的变质岩浆作用,本文对南迦巴瓦复合体北部的花岗片麻岩和混合岩进行了岩石学和年代学研究。花岗片麻岩原岩为富钾的偏铝质花岗岩,具有岩浆弧花岗岩的成分特征。花岗片麻岩中的锆石具有岩浆锆石的环带结构,记录了487.9±1.6Ma的一期构造岩浆事件;混合岩的锆石具有明显的核-边结构,核部和边部的不协和线交点年龄分别为1559±13Ma、1154±12Ma。对比印度大陆东部的西隆高原、东高止造山带,发现三者都经历了拉布拉多期、格林威尔期以及泛非期的造山作用。因此,我们认为喜马拉雅东构造结与这两个地区密切相关,可能是他们向北的延伸,这三者可能组成统一的印度大陆东部造山带,一起经历了哥伦比亚超大陆、Rodinia和冈瓦纳超大陆的聚合与裂解过程。 相似文献
19.
印度-亚洲板块碰撞导致喜马拉雅山脉的崛起、青藏高原的生长、两倍于正常地壳厚度的巨厚陆壳体,以及大量青藏高原腹地的物质沿着大型走滑断裂朝东、东南、西的方向逃逸。印度-亚洲碰撞如何造成板块汇聚边界由挤压到走滑的构造转换对认识大陆岩石圈的变形机制具有重要意义。本文通过总结喜马拉雅造山带及青藏东南缘~55Ma以来的构造、变质、岩浆记录,发现高喜马拉雅的挤出起始于始新世加厚的喜马拉雅造山带中—下地壳的部分熔融,受控于渐新世以来同期发育的向南逆冲和平行造山带的韧性伸展,并建立了高喜马拉雅"三维挤出"构造模式。晚始新世以来,羌塘地块和拉萨地块的物质通过"岩石圈横弯褶皱和壳内解耦"的运动学机制,围绕东构造结发生顺时针旋转并向青藏高原东南缘逃逸。结合东南亚板块重建的资料,我们认为:印度-亚洲的"陆-陆碰撞"到印度洋板块-亚洲东南大陆的"洋-陆俯冲"的转换是导致从印度-亚洲主碰撞带的挤压到青藏东南缘走滑转换的根本原因。 相似文献
20.
桐柏-大别山是从志留至三叠纪连续发展演化的碰撞型造山带,以大规模推覆-滑脱构 为特征,推覆距离可达140km。造山带可分为超叠陆壳、混杂岩片及俯冲陆壳三个构造单元。地层对比、同位素年龄及变形分析可追溯其演化史:晚元古代泛中国板块解体;志留纪末期,古特提斯洋壳俯冲消减;石炭纪时,扬子与华北板块碰撞,陆间俯冲开始,华北板块推覆到扬子板块北缘之上;三叠纪末,形成前陆褶冲带;侏罗-白垩纪以来,造山带收缩隆起,伴随岩浆活动,大型走滑断裂及断陷盆地。 相似文献