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1.
根据P波走时反演重建的三维速度图像,研究东秦岭造山带莫霍面的展布性态结果表明,在华北板块南缘潼关-登封-阜阳-线、商丹主缝合带北侧卢氏-奕川-方城-信阳-线和扬子板块北缘佛坪-陨西-武当山-枣阳-线莫霍面沿着造山带走向呈带状隆起而介于这三条带间,莫霍面均不同程度地下陷因此,东秦岭造山带在岩石圈缩短方向上莫霍面的展布目前仍然存在着很大的非均一性结合造山带地质、岩石地球化学和同位素年代学综合分析,认为造成莫霍面这一展布格局,主要与该碰撞造山带在不同演化时期各岩石构造单元中发生不同性态的岩石圈-软流圈和壳-幔间物质与能量的相互作用方式不一所造成的大陆动力学过程不同有关加上碰撞期后造山带深部岩石圈均衡在不同岩石构造单元中的差异,形成了东秦岭造山带目前莫霍面的展布。 相似文献
2.
扬子板块东北缘中元古代的大地构造划分 总被引：1，自引：0，他引：1
扬子板块东北缘存在四条主要的中元古代变质带,自南向北依次为江南变质带、沿江变质带、云台一张八岭变质带和连云港一泗阳变质带。它们分别为中元古代的古弧后盆地、火山岛弧、裂谷及弧前盆地,扬子板块东北缘中元古代为活动大陆边缘构造体系。苏（北）胶（南）变质造山带应解体,其中一部分属扬子大陆边缘体系。 相似文献
3.
Pacific-type orogeny revisited: Miyashiro-type orogeny proposed 总被引：30，自引：0，他引：30
Abstract The concept of Pacific-type orogeny is revised, based on an assessment of geologic data collected from the Japanese Islands during the past 25 years. The formation of a passive continental margin after the birth of the Pacific Ocean at 600 Ma was followed by the initiation of oceanic plate subduction at 450 Ma. Since then, four episodes of Pacific-type orogeny have occurred to create an orogenic belt 400 km wide that gradually grew both oceanward and downward. The orogenic belt consists mainly of an accretionary complex tectonically interlayered with thin (<2 km thick), subhorizontal, high-P/T regional metamorphic belts. Both the accretionary complex and the high-P/T rocks were intruded by granitoids ～100 million years after the formation of the accretionary complex. The intrusion of calc-alkaline (CA) plutons was synchronous with the exhumation of high-P/T schist belts. Ages from microfossils and K-Ar analysis suggest that the orogenic climax happened at a time of mid-oceanic ridge subduction. The orogenic climax was characterized by the formation of major subhorizontal orogenic structures, the exhumation of high-P/T schist belts by wedge extrusion and subsequent domed uplift, and the intrusion-extrusion of CA magma dominantly produced by slab melting. The orogenic climax ended soon after ridge subduction, and thereafter a new Pacific-type orogeny began. A single Pacific-type orogenic cycle may correspond to the interaction of the Asian continental margin with one major Pacific oceanic plate. Ophiolites in Japan occur as accreted material and are not of island-arc but of plume origin. They presumably formed after the birth of the southern Pacific superplume at 600 Ma, and did not modify the cordilleran-type orogeny in a major way. Microplates, fore-arc slivers, intra-oceanic arc collisions and the opening of back-arc basins clearly contributed to cordilleran orogenesis. However, they were of secondary importance and served only to modify pre-existing major orogenic components. The most important cause of cordilleran-type orogeny is the subduction of a mid-oceanic ridge, by which the volume of continental crust increases through the transfer of granitic melt from the subducting oceanic crust to an orogenic welt. Accretionary complexes are composed mainly of recycled granitic sediments with minor amounts of oceanic material, which indicate that the accretion of oceanic material, including huge oceanic plateaus, was not significant for orogenic growth. Instead, the formation and intrusion of granitoids are the keys to continental growth, which is the most important process in Pacific-type orogeny. Collision-type orogeny does not increase the volume of continental crust. The name ‘Miyashiro-type orogeny’ is proposed for this revised concept of Pacific-type or cordilleran-type orogeny, in order to commemorate Professor A. Miyashiro's many contributions to a better understanding of orogenesis. 相似文献
4.
Seismic tomography beneath the orogenic belts and adjacent basins of northwestern China 总被引：2，自引：0，他引：2
Three-dimensional velocity images of the crust and upper mantle beneath orogenic belts and adjacent basins of the northwestern
continent of China are reconstructed by seismic tomography, based on arrival data of P wave recorded in seismic networks in
Xinjiang, Qinghai, Gansu of China and Kyrgyzstan. The velocity images of upper crust demonstrate the tectonic framework on
the ground surface. High velocities are observed beneath orogenic belts, and low velocities are observed in the basins and
depressions that are obviously related to unconsolidated sediments. The velocity image in mid-crust maintains the above features,
and in addition low velocities appear in some earthquake regions and a low velocity boundary separates the western Tianshan
Mts. from eastern Tianshan Mts. The orogenic belts and the northern Tibetan plateau have a Moho depth over 50 km, whereas
the depths of the Moho in basins and depressions are smaller than 50 km. The velocity images of upper mantle clearly reveal
the colliding relationship and location of deep boundaries of the continental blocks in northwestern China, indicating a weakness
of the upper mantle structure of orogenic belts. The top depth of upper mantle asthenosphere varies from place to place. It
seems shallower under the northern Tibetan plateau, Altay and Qilian Mts., and deeper under the Tarim and Tianshan regions.
Hot mantle probably rose to the bottom of some orogenic belts along tectonic boundaries when continental blocks collided to
each other. Therefore their dynamic features are closely correlated to the formation and evolution of orogenic belts in northwestern
China. 相似文献
5.
以中国大陆西北地区地震层析成像的结果为基础，通过分析大陆块体内部岩石层和软流层的深部形态，提出西部造山带与相邻块体之间几种可能的碰撞类型：天山与塔里木之间存在地块的嵌入拼合、俯冲、岩石层拆离下沉以及层间插入等多种构造样式；青藏高原与北部地质单元之间存在十分清晰的深部边界，反映出上地幔物质向北扩展的痕迹；推测青藏高原的岩石层在向北运动的过程中由于受到塔里木刚性块体的阻滞发生弯曲甚至折断，但是祁连山以北较浅的软流层相当于一个开放边界，使高原的上地幔物质得以进一步向北迁移.大陆碰撞不仅造成中国西部造山带岩石层结构的变动，而且导致软流层中一部分熔融的岩浆体沿着碰撞边界上涌到岩石层底部，它们对青藏高原以及西部造山带的形成演化起到重要的作用. 相似文献
6.
Abstract The Southern Uralides are a collisional orogen generated in the Late Devonian–Early Carboniferous by the collision of the Magnitogorsk island arc (MA) generated in the Early to Middle Devonian by intra‐oceanic convergence opposite to the continental margin, and the continental margin of the East European craton. A suture zone of the arc to the continental margin, the Main Uralian Fault (MUF), is marked by ophiolites and exhumed high‐pressure–low‐temperature metamorphic rocks of continental origin. The pre‐orogenic events of the Southern Urals and their geodynamic setting are traced by means of fluid‐immobile incompatible trace elements (rare earth elements and high field strength elements) and Sr–Nd–Pb isotope geochemistry of the MA suites, in particular the protoarc suite with boninites and probably ankaramites, and the mature arc comprised of island arc tholeiitic (IAT) suites, transitional IAT to calc‐alkaline (CA), and CA suites. The MA volcanics result in genetically distinct magmatic source components. In particular, depleted normal‐mid‐oceanic ridge basalt‐type mantle sources with various enrichments in a slab‐derived aqueous fluid component are evident. The enriched component is not involved in significant amounts, as testified by the rather radiogenic Nd isotopes and unradiogenic Pb isotopes. Further information on the pre‐orogenic events is provided by the Mindyak Massif metagabbros derived from diverse gabbroic protoliths that were affected by oceanic rodingitization, and subsequently by a high‐temperature (HT) metamorphism related to the development of a metamorphic sole. The HT metamorphism has the same age as the protoarc volcanism, and constrains the initiation of subduction at approximately 410 Ma. Consequently, the maximum timespan between initial intra‐oceanic convergence and final collision is approximately 31 my, a duration consistent with that of present‐day ongoing collisions in the western Pacific. The characteristics of early volcanism and the traces of a metamorphic sole provide useful criteria to attribute most MUF ophiolites to the Tethyan type with a complex pre‐orogenic evolution. 相似文献
7.
Modern collisional orogens represent the natural laboratory for the study of metallogeny in continental collision zones. The Pyrenees, Alps, Zagros and Himalaya are all associated with Neo-Tethyan subduction and represent the youngest collisional orogens on Earth. Here, we compare these four orogens in terms of their composition, architecture, tectonic evolution, and metallogenic systems. The four orogens can be divided into simple and composite types. Simple orogens are represented by the Pyrenees and the Alps, and are characterized by narrow linear shapes in plain view and symmetric structures in cross-section, are free of arc magmatism, and are associated with the Mississippi Valley Valley-type Pb-Zn and orogenic gold deposits. The mineral deposits that form in these simple collisional orogens are generally related to processes that occur in the middle and upper crust. In contrast, composite orogens, as exemplified by the Zagros-Iranian and Himalayan-Tibetan Plateaus, are associated with broad orogenic plateaus in plain view and asymmetrical structures in cross-section, record extensive arc magmatism in continental margins, and are associated with a variety of deposit types including carbonatite-related rare earth element (REE), porphyry Cu-Mo, orogenic Au, Mississippi Valley type Pb-Zn, and detachment-fault-related polymetallic deposits. Although the subduction of Neo-Tethys oceanic crust occurred before the creation of simple collisional orogens in the Pyrenees and the Alps, these areas do not show the record of continental arc magmatism. In contrast, the composite collisional orogens are associated with the development of huge continental margin arcs prior to continental subduction, and the subduction was followed by reactivation of the subduction-modified arc lithospheric material, generating the ore-forming systems in these regions. 相似文献
8.
Sedimentary geochemistry of the Cambrian-Ordovician cherts: Implication on archipelagic ocean of North Qilian orogenic belt 总被引：4，自引：0，他引：4
The Caledonian North Qilian orogenic belt lies between the North China plate and the Qaidam mi-croplates, and resulted from the collision among the Qaidam microplate, mid-Qilian block and the North China plate. The orogen initiated from the rifting of the Late Proterozoic Rodinia, and then it experi-enced stages of Cambrian rift basin and Ordovician archipelagic oceanic basin, and foreland basin during Silurian to Early-Middle Devonian. The average ratios of Al/(Al Fe Mn), Al/(Al Fe), δ Ce, Lan/Ybn and Lan/Cen from cherts of Cambrian Heicigou Formation are 0.797, 0.627, 1.114, 0.994 and 1.034 re-spectively. In the NAS standardized REE distribution pattern, the cherts from Xiangqianshan is slightly HREE enriched, and the cherts from Ganluci and Shiqingdong are plane. All of these features indicated that Cambrian cherts of the Heicigou Formation originated from a continental margin rift background. On the contrary, the average ratios of Al/(Al Fe Mn), Al/(Al Fe), δ Ce, Lan/Ybn, Lan/Cen of the Ordovician chert from Dakecha, Cuijiadun, Shihuigou, Laohushan, Heicigou, Maomaoshan, Bianmagou, Da-chadaban, Baiquanmen, Jiugequan and Angzanggou, are respectively 0.72, 0.58, 0.99, 1.09 and 0.96 respectively. Their NAS standardized REE distribution patterns of most Ordovician cherts are plane mode or slightly HREE enriched. The REE distribution pattern of few samples of cherts are slightly LREE enriched. Characteristics of sedimentary geochemistry and tectonic evolution demonstrated that the Cambrian-Ordovician cherts, associated with rift, oceanic, island arc and back-arc volcanic rocks, was not formed in a typical abyssal oceanic basin or mid-oceanic ridge. On the contrary, they formed in a deepwater basin of continental margin or a archipelagic ocean tectonic setting. Several Early Paleo-zoic ophiolite belts in North Qilian and adjacent periphery Qaidam microplate imply that an archipelagic ocean during Ordovician existed in the east of Pro-Tethys. 相似文献
9.
天山造山带作为世界上陆内最大的造山带之一,现今地震活动频繁,造山运动强烈,是开展陆内造山和内陆地震活动研究的天然试验场.本文利用整个天山造山带地区国内及国际台网的108个地震台站连续三年的背景噪声资料,提取了8~50 s周期的瑞利面波相速度频散曲线,并构建了整个天山造山带地区的二维瑞利面波相速度与方位各向异性分布图像.结果表明：浅部结构与地表的地质构造单元具有较大的相关性.低波速异常主要分布于沉积层厚度较大的盆地地区,而高波速异常主要分布于构造活动比较活跃的山脉地区.东天山地区中下地壳存在比较弱的低波速异常,而塔里木盆地和准噶尔盆地汇聚边缘的上地幔区域则表现为明显的高波速异常,各向异性快波方向呈现近NS向的特征,暗示着塔里木盆地和准噶尔盆地的岩石圈已经俯冲至东天山的下方.中天山地区的中下地壳至上地幔区域均呈现为明显的低波速异常,且各向异性快波方向变化比较复杂,表明中天山地区的整个岩石圈结构已经弱化,热物质上涌可能对介质的方位各向异性有一定的影响.西天山及帕米尔高原的上地幔区域存在低波速异常,各向异性表现为NW-SE方向,可能与欧亚板块的大陆岩石圈南向俯冲有关.塔里木盆地内部存在相对弱的低波速异常,推测塔里木盆地可能已经受到上涌的地幔热物质的侵蚀和破坏. 相似文献
10.
Compositional study of minerals within the Qinlingliang granite, Southwestern Shaanxi Province and discussions on the related problems 总被引：6，自引：0，他引：6
The Qinlingliang granite massif, Southwestern Shaanxi Province, China was reported as a rapakivi intrusion. However, its mineralogical and petrological study and detailed comparison with the Shachang rapakivi bodies in Miyun County, Beijing show that it obviously contrasts with typical rapakivi in petrographical characteristics, mineralogical assemblages, compositions of feldspar and mafic minerals, and species and contents of accessory minerals. Hence it is argued to be one of the quartz monzonite intrusions common in continental orogenic belts instead of rapakivi. Comprehensive discussions make several problems more clear, namely the Qinlingliang massif formed in a compressional tectonic background instead of an extensional setting; it intruded at the beginning of the full-scale collision between the Yangtze and North China plates other than the post-orogenic stage; the Qinling belt was an Indosinian-Yanshannian continental collision orogen. 相似文献
11.
DONG Ze-yi TANG Ji CHEN Xiao-bin WANG Li-feng WANG Ji-jun MENG Bu-zai BAI Yun 《地震地质》2016,38(1):107-120
Magnetotelluric data are collected along a NW-SE trending and about 900km long profile within northeastern boundary areas of the North China craton(NCC). This profile extends from the Hegenshan belt within the Central Asian orogenic belt(CAOB), across the Baolidao arc, Solonker-Linxi suture zone, Ondor Sum accretion complex, Bainaimiao arc, Inner Mongolia paleo-uplift, Yanshan belt, and ends on the Liaohe depression of the NCC. Impedance tensor decomposition methods are used to study the dimensionality and geo-electric strike of MT data of the region. Two-dimension (2D) analysis is appropriate for this profile. The 2-D subsurface electrical resistivity structure along profile is obtained using the non-linear conjugate gradient (NLCG) algorithm. The electrical resistivity structure is characterized by lateral segmentation, and divided into high resistive, low resistive, and high resistive areas; The lateral variation of electrical resistivity is significant within the CAOB, but it is smooth in the NCC; The extensive high conductive body(HRB)is observed in the mid-low crust beneath the Solonker-Linxi suture zone and Inner Mongolia paleo-uplift, respectively; The low resistivity could be due to the partial melts and crustal flows. Based on our electrical resistivity structure and other geological, geophysical observations, we speculate that (1)the final suturing of the Siberian craton to the NCC could be along the areas between Xilinhot Fault and Xar Moron Fault; (2)the relatively thick high resistive body beneath the Yanshan belt may serve as a tectonic barrier separating the on-craton and off-craton regions into different upper mantle convection system, and lower the effect of tectonic evolution of CAOB on the destruction to NCC. 相似文献
12.
Yukio Isozaki 《Island Arc》2019,28(3)
The current state of knowledge on the early Paleozoic evolution of Japan is reviewed. Although early Paleozoic Japan marked the foundation of long‐lasting subduction‐related orogenic growth throughout the Phanerozoic, details of this have not been fully revealed. Nevertheless, U‐Pb dating of zircons both in Paleozoic granitoids and sandstones is revealing several new aspects of early Paleozoic Japan. The timing of the major tectonic change, from a passive continental margin setting (Stage I) to an active one (Stage II), was constrained to the Cambrian by identifying the oldest arc granitoid, high‐P/T blueschist, and terrigenous clastics of arc‐related basins. Ages of recycled zircons in granitoids and sandstones provided critical information on the homeland of Japan, i.e. the continental margin along which proto‐Japan began to grow. The early Paleozoic continental margin that hosted the development of an arc‐trench system in proto‐Japan had cratonic basement composed mostly of Proterozoic crust with a minor Archean component. The predominant occurrence of Neoproterozoic zircons in Paleozoic rocks, as xenocrysts in arc granitoids and also as detrital grains in terrigenous clastics, indicates that the relevant continental block was a part of South China, probably forming a northeastern segment of Greater South China (GSC) together with the Khanka/Jiamsi/Bureya mega‐block in Far East Asia. GSC was probably twice as large as the present conterminous South China on mainland Asia. Paleozoic Japan formed a segment of a mature arc‐trench system along the Pacific side of GSC, where the N–S‐trending Pacific‐rim orogenic belt (Nipponides) developed with an almost perpendicular relationship with the E–W‐trending Central Asian orogenic belt. The faunal characteristics of the Permian marine fauna in Japan, both with the Tethyan and Boreal elements, can be better explained than before in good accordance with the relative position of GSC with respect to the North China block during the late Paleozoic. 相似文献
13.
ZHANG Guowei Dong Yunpeng Lai Shaocong GUO anlin Meng Qingren Liu Shaofeng CHENG Shunyou Yao Anping ZHANG Zongqing PEI Xianzhi Li Sanzhong 《中国科学D辑(英文版)》2004,47(4)
The Mianlue tectonic zone (Mianlue zone), an ancient suture zone in addition to theShangdan suture in the Qinling-Dabie orogenic belt, marks an important tectonic division geo-logically separating north from south and connecting east with west in China continent. To de-termine present structural geometry and kinematics in the Mianlue tectonic zone and to recon-struct the formation and evolution history involving plate subduction and collision in theQinling-Dabie orogenic belt, through a multidisciplinary study, are significant for exploring themountain-building orogenesis of the central orogenic system and the entire process of the majorChinese continental amalgamation during the Indosinian. 相似文献
14.
Regional metamorphic belts of the Japanese Islands 总被引：1，自引：0，他引：1
Abstract An overview of the regional metamorphic belts of Japan is given in the context of the tectonic evolution of the Japanese Islands. The Japanese Islands were situated on an active margin of the Eurasian continent or its constituent landmass before their assembly during the Phanerozoic. The Japanese Islands are composed mainly of metamorphosed and unmetamorphosed accretionary complexes, granitoids and their effusive equivalents that were formed by the Cordilleran-type orogeny. The metamorphic belts are regarded essentially as a deep-seated portion of an accretionary complex. In spite of continuous subduction of oceanic plates beneath the continents, these orogenic rocks were formed quite episodically, as evidenced by discontinuous matrix ages of the accretionary complexes and a striking concentration of isotopic ages of the granitoids. A systematic along-arc age shift of Cretaceous large-scaled granitic magmatism and regional metamorphism suggests a tectonic control such as ridge subduction, which triggered the episodic orogeny. A tectonic model based on the paired metamorphic belts, combined with the non-steady tectonic control, works well to explain this magmatism and metamorphism in a single arc-trench system as a continental margin process. However, the juxtapositional process of the paired metamorphic belts is still a problem. Two possible cases, namely transcurrent displacement and back-arc overthrusting are discussed. 相似文献
15.
西伯利亚板块与华北克拉通碰撞导致古亚洲洋闭合,形成了幅员辽阔的中亚造山带,该带内记录了丰富的板块碰撞信息,揭示深部缝合边界对于研究洋-陆俯冲到陆-陆碰撞的深部动力学过程具有重要的科学意义.本文对查干敖包—化德410km大地电磁测深(MT)剖面数据进行反演,获得二维电性结构,为研究西伯利亚板块与华北克拉通碰撞带深部构造形迹、碰撞边界问题提供地电结构的依据.结合人工反射地震及地质资料获得以下认识:(1)西伯利亚板块与华北克拉通碰撞带地壳存在多组"U"型低阻异常,多对应弧型、倾斜或"鳄鱼嘴"状反射界面.莫霍面存在两处错断现象,并与深部电性梯度带对应.岩石圈地幔除白乃庙岛弧呈低阻块体外,均为高阻块体,这些电性结构特征反映了南北汇聚所形成的构造形迹.(2)碰撞带可分为二连—贺根山和索伦—西拉木伦河两个不同时期的汇聚体系,晚泥盆世—晚石炭世早期形成的二连—贺根山汇聚体系由二连—贺根山增生杂岩带、宝力岛弧地体及断裂带组成,深部缝合边界位于二连浩特.而晚二叠—早三叠的索伦—西拉木伦河汇聚体系由二道井子增生杂岩带和温都尔庙增生杂岩带及断裂带组成,深部缝合边界位于苏尼特右旗.(3)在锡林浩特地区软流圈内部存在高阻异常,可能为俯冲消失的洋壳或碰撞造山后拆离的岩石圈残片. 相似文献
16.
Based on deep geophysical detections, we have reconstructed the crustal structure from the eastern margin of the Tibetan Plateau to the Jiangnan-Xuefeng orogenic belt. The results suggest that the Yangtze Block was overthrusted by crustal materials in its NW direction from the eastern Tibetan Plateau but in its SE direction from the Jiangnan orogen. These overthrusting effects control the crustal structure from the western Sichuan to the western area of the Jiangnan orogen-Xuefeng orogenic belt. The eastward extruded materials from the eastern Tibetan Plateau were blocked by the rigid basement in the Sichuan Basin, where upper-middle crust was overthrusted whereas the lower crust was underthrusted beneath the Sichuan Basin. The underthrusted unit was absorbed by crustal folding, shortening and thickening in the Yangtze Block, forming the Xiongpo and Longquan Mountains tectonic belts and resulting in the NW-directed thrusting of the Pujiang-Chengdu-Deyang fault, and the western hillsiden fault in the Longquan Mountain. These results provide resolution to the controversy where the eastward extrusion material from the Qinghai-Tibet Plateau had gone. Overall, that Yangtze Block was subjected to thrusting of the crustal materials from the orogenic belts over its both sides. This finding has implications for the study of the intracontinental orogenic mechanism in South China, the reconstruction of tectonic evolutionary history and the kinematics processes during the lateral extrusion of the Tibet Plateau. 相似文献
17.
Terrane analysis and accretion in North-East Asia 总被引：2，自引：0，他引：2
Abstract A terrane map of North-East Asia at 1:5 000 000 scale has been compiled. The map shows terranes of different types and ages accreted to the North-Asian craton in the Mesozoic–Cenozoic, sub-and superterranes, together with post-amalgamation and post-accretion assemblages. The great Kolyma-Omolon superterrane adjoins the north-east craton margin. It is composed of large angular terranes of continental affinity: craton fragments and fragments of the passive continental margin of Siberia, and island arc, oceanic and turbidite terranes that are unconformably overlain by shallow marine Middle-Upper Jurassic deposits. The superterrane resulted from a long subduction of the Paleo-Pacific oceanic crust beneath the Alazeya arc. Its south-west boundary is defined by the Late Jurassic Uyandina-Yasachnaya marginal volcanic arc which was brought about by subduction of the oceanic crust that separated the superterrane from Siberia. According to paleomagnetic evidence the width of the basin is estimated to be 1500–2000 km. Accretion of the superterrane to Siberia is dated to the late Late Jurassic-Neocomian. The north-east superterrane boundary is defined by the Lyakhov-South Anyui suture which extends across southern Chukotka up to Alaska. Collision of the superterrane with the Chukotka shelf terrane is dated to the middle of the Cretaceous. The Okhotsk-Chukotka belt, composed of Albian-Late Cretaceous undeformed continental volcan-ites, defines the Cretaceous margin of North Asia. Terranes eastward of the belt are mainly of oceanic affinity: island arc upon oceanic crust, accretion wedge and turbidite terranes, as well as cratonic terranes and fragments of magmatic arcs on the continental crust and metamorphic terranes of unclear origin and age. The time of their accretion is constrained by post-accretionary volcanic belts that extend parallel to the Okhotsk-Chukotka belt but are displaced to the east: the Maastrichtian-Miocene Kamchatka-Koryak belt and the Eocene-Quaternary Central Kamchatka belt which mark active margins of the continent of corresponding ages. 相似文献
18.
ZHANG Chengli GAO Shan ZHANG Guowei GUO Anlin YUAN Honglin LIU Xiaoming & WANG Jianqi . The key Laboratory of Continental Dynamics Ministry of Education Department of Geology Northwest University Xian China . State Key Laboratory for Mineral Deposits Research Nanjing University Nanjing China . Department of Geochemistry China University of Geosciences Wuhan China 《中国科学D辑(英文版)》2004,47(4)
Since the 1980s, one of the important progresses in the study of the Qinling orogenic belt is marked by findings of numerous ophiolite zones[1—4]. On the basis of the former orogenic models of the Paleozoic colli-sional orogeny[1,5,6] and the Mesozoic collision[7—9], another orogenic evolution model from the Paleozoic subduction-collision along the Shangdan suture to the Mesozoic final collision orogeny along the Mianle suture[3,10], including the relicts of the Jining orogeny, has been pr… 相似文献
19.
《中国科学D辑(英文版)》2004,(4)
The Mianle tectonic zone, defined as a series of fault zones consisting mainly of south-verging thrusts and nappes, represents the south boundary of the Qinling-Dabie orogenic belt. The north side of the eastern end of the Mianle tectonic zone adjoins the exposure of the Dabieshan UHP rocks. Further to east, the zone was offset by the Tanlu faults and moved to eastern Shandong Province. While to its west, across the Qinghai-Tibetan Plateau, the zone was dislocated by the Altun fault, and… 相似文献
20.
The Chiang Khong segment of the Chiang Khong–Lampang–Tak Volcanic Belt is composed of three broadly meridional sub‐belts of mafic to felsic volcanic, volcaniclastic, and associated intrusive rocks. Associated sedimentary rocks are largely non‐marine red beds and conglomerates. Three representative Chiang Khong lavas have Late Triassic (223–220 Ma) laser ablation inductively coupled mass‐spectroscopy U–Pb zircon ages. Felsic‐dominated sequences in the Chiang Khong Western and Central Sub‐belts are high‐K calc–alkaline rocks that range from basaltic to dominant felsic lavas with rare mafic dykes. The Western Sub‐belt lavas have slightly lower high field strength element contents at all fractionation levels than equivalent rocks from the Central Sub‐belt. In contrast, the Eastern Sub‐belt is dominated by mafic lavas and dykes with compositions transitional between E‐mid‐oceanic ridge basalt and back‐arc basin basalts. The Eastern Sub‐belt rocks have higher FeO* and TiO2 and less light rare earth element enrichment than basalts in the high‐K sequences. Basaltic and doleritic dykes in the Western and Central sub‐belts match the composition of the Eastern Sub‐belt lavas and dykes. A recent geochemical study of the Chiang Khong rocks concluded that they were erupted in a continental margin volcanic arc setting. However, based on the dominance of felsic lavas and the mainly non‐marine associated sediments, we propose an alternative origin, in a post‐collisional extensional setting. A major late Middle to early Late Triassic collisional orogenic event is well documented in northern Thailand and Yunnan. We believe that the paucity of radiometric dates for arc‐like lavas in the Chiang Khong–Lampang–Tak Volcanic Belt that precede this orogenic event, coupled with the geochemistry of the Chiang Khong rocks, and strong compositional analogies with other post‐collisional magmatic suites, are features that are more typical of volcanic belts formed in a rapidly evolving post‐collisional, basin‐and range‐type extensional setting. 相似文献