辽西地区中生代岩石圈结构与演化的有限元模拟

利用大型通用有限元分析软件ANSYS简单模拟辽西地区中生代末期岩石圈动力学演化过程。为了与现今实际地质观测一致,我们分两步模拟了辽西中生代岩石圈的动力学演化。第一阶段,中国东部显著的地幔上升热柱导致本研究区壳-幔边界上升,岩石圈减薄,同时伴有少量断层发育;第二阶段,地幔热柱上涌活动逐渐减弱,地表产生沉降。这一地质模型可重塑与现代观测一致的裂谷沉降、裂谷侧翼地形、壳-幔边界隆升。研究结果表明：ANSYS软件及有限元方法在岩石圈动力学数值模拟领域是一个非常有效的分析工具,具有非常广阔的应用前景。今后将建立与实际情况更吻合的岩石圈结构模型,真正动态地实现辽西中生代盆地区岩石圈结构的演化过程模拟。     

燕山东段下辽河地区中新生代盆山构造演化

笔者通过分析燕山东段-下辽河地区的前中生代构造背景和中新生代盆山构造演化认为,该区中新生代的构造演化过程是在前中生代华北克拉通岩石图基础上发育起来的克拉通内(陆内或板内)盆山构造与挤压构造的交替演化过程,经历了早-中三叠世、晚三叠世-早侏罗世、中-晚侏罗世、白垩纪、新生代5个盆山构造演化阶段和中三叠世末、早侏罗世末、晚侏罗世末和白垩纪末、老第三纪末5期挤压作用。每次挤压作用都使得早期盆地萎缩或消亡,造成早期盆地反转。中-晚侏罗世、白垩纪和新生代三个阶段的伸展作用形成中-晚侏罗世断陷盆地、白垩纪断陷盆地和新生代裂谷盆地。在这一构造演化过程中,挤压作用和伸展作用交替出现,挤压构造和伸展构造间互发育。      

中国硒矿资源概述

硒在地球上含量很低，难以形成独立的经济矿床，常作为伴生矿产出。硒矿石不仅广泛用于化工、冶金、建材、电子、医药等工业部门，而且是人体不可缺少的微量元素，享有“生命的奇效元素”之美称。中国硒矿资源丰富，可划分为岩浆、斑岩、矽卡岩、热液型伴生矿床、沉积型独立矿床及硒矿泉水等不同类型。在不同时期的滨海相碳质建造、矽卡岩型矿床及构造蚀变岩中，具有良好的找矿前景。     

中、上扬子北部盆-山系统演化与动力学机制

中国南方中生代经历了中国大陆最终主体拼合的陆缘及其之后的陆内构造演化。晚古生代末期,在秦岭—大别山微板块与扬子板块之间存在向西张口的洋盆,即勉略古洋盆。中三叠世末期开始,扬子板块相对于华北板块发生自南东向北西的斜向俯冲碰撞作用,扬子北缘晚三叠世至中侏罗世发育陆缘前陆褶皱逆冲带与前陆盆地系统。晚侏罗世至早白垩世,中国东部的大地构造背景发生了重要的构造转变,中、上扬子地区处于三面围限会聚的大地构造背景。在这种大地构造格局下,中、上扬子地区晚侏罗世至早白垩世发育陆内联合、复合构造与具前渊沉降的克拉通内盆地系统。自中侏罗世末期开始,扬子北缘前陆带与雪峰山—幕阜山褶皱逆冲带经历了自东向西的会聚变形过程及盆地的自东向西的迁移过程和收缩过程。扬子北缘相对华北板块的斜向俯冲导致在中扬子北缘的深俯冲及超高压变质岩的形成。俯冲之后以郯庐断裂—襄广断裂围限的大别山超高压变质地块在晚侏罗世向南强逆冲,致使扬子北缘晚三叠世至中侏罗世前陆盆地被掩覆和改造。     

俄罗斯东部地区油气资源远景分析

俄罗斯东部地区油气资源十分丰富,而且远景储量巨大。其石油储量远景区主要圈定在东西伯利亚地区晚元古代-早古生代陆源碎屑岩-碳酸盐岩含油气盆地,远东地区中-新生代大陆架硅质岩含油气盆地和远东滨海坳陷中古新世-始新世杂砂岩含油气建造等。而且,远东地区含油气盆地的形成时代自西向东逐渐变年轻,具体由侏罗纪、白垩纪过渡为新生代。俄罗斯东部地区中-新生代煤层气盆地广布,其中最主要的煤层气盆地为勒拿河流域盆地和南雅库特盆地。煤层气的成因及分布特征主要受控于盆地的基本地质特征,即上覆、下伏地层层系和褶皱断裂构造、变质作用等。俄罗斯远东地区萨哈林大陆架、鄂霍茨克海以及白令海阿列乌特深水海盆中蕴藏大量的天然气水合物资源。天然气水合物中的甲烷一般被认为来自深部油气层,但也有专家认为它可能来自大陆架以外的深海海域。     

The Bothnian Sea ice stream: early Holocene retreat dynamics of the south‐central Fennoscandian Ice Sheet

The Gulf of Bothnia hosted a variety of palaeo‐glaciodynamic environments throughout the growth and decay of the last Fennoscandian Ice Sheet, from the main ice‐sheet divide to a major corridor of marine‐ and lacustrine‐based deglaciation. Ice streaming through the Bothnian and Baltic basins has been widely assumed, and the damming and drainage of the huge proglacial Baltic Ice Lake has been implicated in major regional and hemispheric climate changes. However, the dynamics of palaeo‐ice flow and retreat in this large marine sector have until now been inferred only indirectly, from terrestrial, peripheral evidence. Recent acquisition of high‐resolution multibeam bathymetry opens these basins up, for the first time, to direct investigation of their glacial footprint and palaeo‐ice sheet behaviour. Here we report on a rich glacial landform record: in particular, a palaeo‐ice stream pathway, abundant traces of high subglacial meltwater volumes, and widespread basal crevasse squeeze ridges. The Bothnian Sea ice stream is a narrow flow corridor that was directed southward through the basin to a terminal zone in the south‐central Bothnian Sea. It was activated after initial margin retreat across the Åland sill and into the Bothnian basin, and the exclusive association of the ice‐stream pathway with crevasse squeeze ridges leads us to interpret a short‐lived stream event, under high extension, followed by rapid crevasse‐triggered break‐up. We link this event with a c. 150‐year ice‐rafted debris signal in peripheral varved records, at c. 10.67 cal. ka BP. Furthermore, the extensive glacifluvial system throughout the Bothnian Sea calls for considerable input of surface meltwater. We interpret strongly atmospherically driven retreat of this marine‐based ice‐sheet sector.     

Sedimentary basins of Yemen: their tectonic development and lithostratigraphic cover

This paper describes the updated stratigraphy, structural framework and evolution, and hydrocarbon prospectivity of the Paleozoic, Mesozoic and Cenozoic basins of Yemen, depicted also on regional stratigraphic charts. The Paleozoic basins include (1) the Rub’ Al-Khali basin (southern flanks), bounded to the south by the Hadramawt arch (oriented approximately W–E) towards which the Paleozoic and Mesozoic sediments pinch out; (2) the San’a basin, encompassing Paleozoic through Upper Jurassic sediments; and (3) the southern offshore Suqatra (island) basin filled with Permo-Triassic sediments correlatable with that of the Karoo rift in Africa. The Mesozoic rift basins formed due to the breakup of Gondwana and separation of India/Madagascar from Africa–Arabia during the Late Jurassic/Early Cretaceous. The five Mesozoic sedimentary rift basins reflect in their orientation an inheritance from deep-seated, reactivated NW–SE trending Infracambrian Najd fault system. These basins formed sequentially from west to east–southeast, sub-parallel with rift orientations—NNW–SSE for the Siham-Ad-Dali’ basin in the west, NW–SE for the Sab’atayn and Balhaf basins and WNW–ESE for the Say’un-Masilah basin in the centre, and almost E–W for the Jiza’–Qamar basin located in the east of Yemen. The Sab’atayn and Say’un–Masilah basins are the only ones producing oil and gas so far. Petroleum reservoirs in both basins have been charged from Upper Jurassic Madbi shale. The main reservoirs in the Sab’atayn basin include sandstone units in the Sab’atayn Formation (Tithonian), the turbiditic sandstones of the Lam Member (Tithonian) and the Proterozoic fractured basement (upthrown fault block), while the main reservoirs in the Say’un–Masilah basin are sandstones of the Qishn Clastics Member (Hauterivian/Barremian) and the Ghayl Member (Berriasian/Valanginian), and Proterozoic fractured basement. The Cenozoic rift basins are related to the separation of Arabia from Africa by the opening of the Red Sea to the west and the Gulf of Aden to the south of Yemen during the Oligocene-Recent. These basins are filled with up to 3,000 m of sediments showing both lateral and vertical facies changes. The Cenozoic rift basins along the Gulf of Aden include the Mukalla–Sayhut, the Hawrah–Ahwar and the Aden–Abyan basins (all trending ENE–WSW), and have both offshore and onshore sectors as extensional faulting and regional subsidence affected the southern margin of Yemen episodically. Seafloor spreading in the Gulf of Aden dates back to the Early Miocene. Many of the offshore wells drilled in the Mukalla–Sayhut basin have encountered oil shows in the Cretaceous through Neogene layers. Sub-commercial discovery was identified in Sharmah-1 well in the fractured Middle Eocene limestone of the Habshiyah Formation. The Tihamah basin along the NNW–SSE trending Red Sea commenced in Late Oligocene, with oceanic crust formation in the earliest Pliocene. The Late Miocene stratigraphy of the Red Sea offshore Yemen is dominated by salt deformation. Oil and gas seeps are found in the Tihamah basin including the As-Salif peninsula and the onshore Tihamah plain; and oil and gas shows encountered in several onshore and offshore wells indicate the presence of proven source rocks in this basin.     

从中国东部地貌演变,看中-新生代成矿成藏作用

中国地势可分为4个阶梯(青藏高原、中部高地、东部平原和海域大陆架),地势分布的特点与热岩石圈厚度的变化基本一致,其成因与印度板块和太平洋板块对欧亚板块的俯冲有关。东部地貌的变化,常依据中酸性岩浆岩分布、区域构造演化、地层沉积和剥蚀、黏土矿物组成、古环境和古气候变化及海水Sr同位素资料来推测。根据埋深不同的4种埃达克岩的时空分布,推断在晚侏罗世—早白垩世,中国东部地区经历了高原萌生期、高原成熟期、高原垮塌期和高原残留期的演化过程。尤其是华北高原成熟-垮塌期与区内断陷盆地的形成及大规模成矿作用密切相关,以渤海湾盆地和胶东金矿集中区为例进行了剖析,并通过地震层析成像资料予以证实;华北克拉通岩石圈的减薄及破坏,由岩石圈拆沉和热侵蚀作用所致,与高原成熟-垮塌期的岩浆活动和成矿期相吻合,埃达克岩的形成也是太平洋板块与地幔上隆热幔柱相互作用的结果。这种认识为深部找矿找藏工作提供了成矿学的理论基础。     

Low-sulfide PGE and nickel sulfide metallogeny of Paleoproterozoic riftogenesis of the Fennoscandian Shield

By the end of the Archean, the period of active volcanism, plutonism, accretion, and cratonization had been completed by the construction of stable continental plates. Afterward, cratons were subject to intense extension owing to mainly mantle diapirism and ascent of asthenospheric flows, which gave rise to the formation of ensialic intracratonic basins, whereas other linear troughs were expressed in the formation of continental rifts. Zones of continental rifting are characterized by a wide spectrum of mineral resources (Cu, Ni, PGE, Co, Ti, V, etc.) related to igneous complexes. This paper is focused on metallogeny of nickel-sulfide and PGE mineralization in the Fennoscandian Shield. The results of metallogenic analysis of Paleoproterozoic riftogenesis, along with the account of previous achievements, have shown that the aforementioned mineralization is related to three consecutive plume-tectonic pulses of mantle activization, which are expressed in (i) upwelling of the subcontinental mantle enriched in LREE, (ii) intrusion of mafic and ultramafic melts derived from enriched and depleted Archean mantle sources, and (iii) formation of low-sulfide Pt–Pd and Pt-bearing Cu–Ni sulfide deposits.     

Late Permian–Middle Jurassic lithospheric thinning in Peru and Bolivia, and its bearing on Andean-age tectonics

Integrated studies and revisions of sedimentary basins and associated magmatism in Peru and Bolivia (8–22°S) show that this part of western Gondwana underwent rifting during the Late Permian–Middle Jurassic interval. Rifting started in central Peru in the Late Permian and propagated southwards into Bolivia until the Liassic/Dogger, along an axis that coincides with the present Eastern Cordillera. Southwest of this region, lithospheric thinning developed in the Early Jurassic and culminated in the Middle Jurassic, producing considerable subsidence in the Arequipa basin of southern Peru. This 110-Ma-long interval of lithospheric thinning ended 160 Ma with the onset of Malm–earliest Cretaceous partial rift inversion in the Eastern Cordillera area.The lithospheric heterogeneities inherited from these processes are likely to have largely influenced the distribution and features of younger compressional and/or transpressional deformations. In particular, the Altiplano plateau corresponds to a paleotectonic domain of “normal” lithospheric thickness that was bounded by two elongated areas underlain by thinned lithosphere. The high Eastern Cordillera of Peru and Bolivia results from Late Oligocene–Neogene intense inversion of the easternmost thinned area.     

南沙海区及其周缘中-新生代岩浆活动及构造意义

通过对南沙海区及其周缘地区中-新生代以来4个主要地质时期即燕山期、喜山早期、喜山晚期一幕和二幕各种类型岩浆岩的发育特征(包括时空分布、地球化学及构造环境)的综合分析,重构了研究区中-新生代岩浆活动的演化历程:燕山期(侏罗纪到白垩纪)在南沙西面和西南面陆区以中酸性岩浆活动为主,代表中生代东亚陆缘火山岩带的南段。同时在南沙与加里曼丹之间广泛发育的是基性-超基性岩,是在俯冲过程中折返到浅部的古南海洋壳碎片。喜山早期(古新世至始新世)岩浆活动微弱。喜山晚期一幕(晚渐新世至中中新世)在加里曼丹—卡加延一带岩浆活动相对重新活跃,西段主要有英安岩、花岗闪长岩、安山岩、闪长岩等,东段主要为玄武安山岩,但规模较小,似乎不足以构成与古南海俯冲伴生的火山岩带。喜山晚期二幕(晚中新世至第四纪)岩浆活动出现高峰,为大规模的中基性火山喷发,与燕山期及喜山早期截然不同,在中南半岛南部和加里曼丹岛中-北部尤为广泛,可能是该区出现上涌的地幔热团的指示。     

Formation and upwelling of mantle diapirs through the cratonic lithosphere: Numerical thermomechanical modeling

This paper reports the results of the numerical modeling of gravitationally instable processes in the lithospheric mantle of ancient cratons. The gravitational instability is considered as a result of melting at the lithosphere base owing to its local heating by anomalous mantle. Modeling was based on a finite element method in 2D formulation and took into account the geological structure and thermomechanical parameters of the lithosphere of the Siberian platform. Numerical results revealed the main tendencies in the mantle diapirisim of the mafic and ultramafic magma ascending through the “cold” high-viscosity lithosphere. It was shown that the shape of diapiric magmatic bodies is controlled by realistic visco-elastic-plastic rheology of lithosphere. The ascent of diapir in lithosphere was modeled for diverse regimes differing in duration, temperature field, and upwelling depth. It was concluded that the ascent of melt through lithosphere to the crust-mantle boundary is mainly controlled by rheology, and conditions of oscillatory diapirism with recurrent magma replenishments were modeled. Modeling results may shed light on some features related to the trap magmatism of the Siberian igneous province. The duration and rate of magma upwelling as well as the parameters of periodical magma upwelling were estimated and attempt was made to explain the high-velocity seismic anomalies that were recorded in the subcrustal regions of the Siberian platform.     

The Avalon Zone: A Pan-African terrane in the Appalachian Orogen of Canada

The Precambrian sequences of the Avalon Zone in Canada (southeastern margin of the Appalachian Orogen) are interpreted as a Pan-African orogenic belt incorporated into the Appalachian Orogen during Palaeozoic times as its southeastern margin. The Precambrian evolution of the Avalon Zone was genetically unrelated to subsequent Palaeozoic evolution. The Avalon Zone shows marked similarities in age, tectonic history, and facies development to the Pan-African belts adjacent to the West African Craton. Precambrian evolution of the zone began with circa 800 Ma rifting of a sialic gneissic basement and deposition of a Middle Proterozoic(?) carbonate-clastic cover sequence. Early crustal rifting was associated with localized partial melting and metamorphism. Limited crustal separation led to the restricted development of circa 760 Ma oceanic volcanics. Continued rifting and subsequent closure of these narrow ocean basins led to the eruption of widespread subaerial volcanic suites, block faulting, granite plutonism, and local, late Proterozoic sedimentary basin formation. Precambrian evolution of the zone terminated with the Avalonian Orogeny (circa 650-600 Ma), a deformational event, the affects of which are most evident locally along the northwestern margin of the zone. The controlling features of the Proterozoic evolution of the Avalon Zone are a series of linear intracratonic troughs and small ocean basins that formed during thinning and separation of the crust by ductile spreading, rupture, and delamination (cf. Martin and Porada 1977). The variation in degree of crustal separation led to subsequent variation in orogenesis during late Proterozoic compression. The zone marks the original westward limit of Pan-African activity and displays no apparent genetic link with the Appalachian Orogen in Canada until Devonian times.     

扬子北缘黄陵地区晚中生代盆地演化及其构造意义

扬子北缘黄陵地区古构造应力场于晚中生代经历发生了重大转变,是扬子板块与华北板块在三叠纪碰撞造山之后陆内构造变形的体现。由黄陵背斜周缘晚中生代盆地充填记录所反映出这一变革的起始时间为中侏罗世晚期。早侏罗世-中侏罗世早期,盆地内沉积了以桐竹园组为代表的河流-湖泊相岩层,由沉积碎屑成分和古水流统计所得出的物源区为北部的秦岭地区,黄陵背斜上部可能也接受了碎屑沉积;中侏罗世晚期-晚侏罗世,沉积中心发生了改变,表现为仅仅在黄陵背斜西侧的秭归盆地内有所保存,沉积环境以曲流河到辫状河流和三角洲为主,物源区则局限于黄陵背斜;早白垩世初期,周坪盆地和宜昌盆地为沉积中心,近缘冲积扇和辫状河流体系占据主体,物源区依然为黄陵地区,两盆地在黄陵背斜南缘可能相连,黄陵背斜上部的原下侏罗统被剥蚀;早白垩世晚期-晚白垩世,远安盆地逐渐发育,盆地西缘为冲积扇-辫状河流体系,中、 东部则以曲流河-湖泊沉积环境为主体,并间有干旱沙漠环境。原型盆地再造结果显示,早侏罗世-中侏罗世早期盆地展布具有近东西向特点,古地貌总体呈现出北部为山脉、 南部为盆地的格局;中侏罗世晚期以来,盆地呈近南北向,黄陵背斜逐渐形成山脉,盆地位于其东西两侧。两期盆地沉积特征反映了扬子北缘古构造应力场由近南北向转变为近东西向的过程。     

中国东部深部构造特征及其与矿集区关系

文中以地震层析原始数据为基础,结合大地电磁测深和热流值数据,对老资料重新开发,编制了中国东部岩石圈厚度图、大地热流值图、岩石圈构造与矿集区关系图等,在此基础上对中国东部上地幔岩石圈-软流圈构造及其变异进行了初步研究,认为:(1)中生代燕山期较大型深部构造(如软流圈上涌体)的地震层析影象可存留至今,运用大地热流值及其相应浅表岩浆岩、矿集区等特征差异可以将中、新生代深部构造加以区分;(2)中国东部深部构造总特征:上地幔岩石圈-软流圈构造起伏变化,岩石圈西厚东薄,软流圈上涌发育且形式各异。大体可分为华南(构造线呈NWW)、华北(构造线近SN)、东北(构造线呈NNE)三大块,其基本特征各异。整个中国东部深部构造中,软流圈上涌起主导作用;(3)中生代软流圈上涌是相应浅表燕山期花岗质岩形成的根源,并与金属矿集区密切相关,新生代软流圈上涌则是大陆裂谷、玄武岩喷发及大型油气田形成的基础;(4)岩石圈减薄的主因是软流圈上涌,中生代燕山期主要减薄于中国东部大陆内部,新生代主要减薄于偏东部沿海区域。     

南海陆缘盆地构造演化与烃源岩特征

受近南北向扩张机制控制,南海陆缘盆地或凹陷多呈NE向带状展布,总体上具有“南三北三”平行排列、外窄内宽的特点。新生代发生的4次重要区域构造运动具有穿时性,共发育3期盆地破裂不整合面,分别是早渐新世与晚渐新世之间、古近纪与新近纪之间、中中新世与晚中新世之间;由东往西,盆地破裂不整合面的时代逐渐变新。受构造运动与海平面升降影响,南海海域发育湖相、海陆过渡相和陆源海相3类烃源岩。由南北两侧向中央海盆,烃源岩类型由湖相逐渐过渡到海陆过渡相与陆源海相;从东向西,盆地主力烃源岩层位逐渐变新,由始新统-渐新统逐渐过渡到渐新统-中新统。南海海域烃源岩的分布规律与盆地破裂不整面存在密切关系:破裂不整合面形成早（早渐新世与晚渐新世之间）的盆地,主力烃源岩形成早（始新统湖相烃源岩）;反之,破裂不整合面形成晚（中中新世与晚中新世之间）的盆地,则烃源岩形成晚（渐新统-中新统海陆过渡相到陆源海相烃源岩）。     

Tectonic Characteristics and Evolution of the Taiwan Strait

The Taiwan Strait is a part of the continental-margin rift of eastern China, which can tectonically be divided into the Taiwan Strait basin, southwestern Taiwan basin and Penhu-Beigang uplift. The basins are structurally semi-graban down-faulted ones in character. The Cretaceous-Cenozoic sedimentary strata in the basins have a maximum thickness of over 10,000 m. The formation and development of the Taiwan Strait rift were not only affected by both the East China Sea basin and South China Sea basin but also closely related to the Central Range collision orogen of Taiwan. In the Cenozoic, the Taiwan Strait area experienced, under the influence of a multiple of tectonic mechanisms, three stages of evolution: poly-centre downfault-ing, down warping-faulting and foreland basin formation. The depositional centres of the basins migrated from west to east during the Tertiary, resulting in the thinning of the Palaeogene strata from west to east but that of the Neogene in the reverse direction. All this determine     

Evolution of the lithosphere in the area of the Rhine Rift System

The Rhine Rift System (RRS) forms part of the European Cenozoic Rift System (ECRIS) and transects the Variscan Orogen, Permo-Carboniferous troughs and Late Permian to Mesozoic thermal sag basins. Crustal and lithospheric thicknesses range in the RRS area between 24–36 km and 50–120 km, respectively. We discuss processes controlling the transformation of the orogenically destabilised Variscan lithosphere into an end-Mesozoic stabilised cratonic lithosphere, as well as its renewed destabilisation during the Cenozoic development of ECRIS. By end-Westphalian times, the major sutures of the Variscan Orogen were associated with 45–60 km deep crustal roots. During the Stephanian-Early Permian, regional exhumation of the Variscides was controlled by their wrench deformation, detachment of subducted lithospheric slabs, asthenospheric upwelling and thermal thinning of the mantle-lithosphere. By late Early Permian times, when asthenospheric temperatures returned to ambient levels, lithospheric thicknesses ranged between 40 km and 80 km, whilst the thickness of the crust was reduced to 28–35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle-derived melts with its basal parts. Re-equilibration of the lithosphere-asthenosphere system governed the subsidence of Late Permian-Mesozoic thermal sag basins that covered much of the RRS area. By end-Cretaceous times, lithospheric thicknesses had increased to 100–120 km. Paleocene mantle plumes caused renewed thermal weakening of the lithosphere. Starting in the late Eocene, ECRIS evolved in the Pyrenean and Alpine foreland by passive rifting under a collision-related north-directed compressional stress field. Following end-Oligocene consolidation of the Pyrenees, west- and northwest-directed stresses originating in the Alps controlled further development of ECRIS. The RRS remained active until the Present, whilst the southern branch of ECRIS aborted in the early Miocene. Extensional strain across ECRIS amounts to some 7 km. Plume-related thermal thinning of the lithosphere underlies uplift of the Rhenish Massif and Massif Central. Lithospheric folding controlled uplift of the Vosges-Black Forest Arch.     

http://www.sciencedirect.com/science/article/pii/S1674987111001095

During the Late Mesozoic Middle Jurassic-Late Cretaceous,basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a r...     

中国岩石圈的基本特征

中国及邻区岩石圈结构构造十分复杂,并具有若干明显的特点:中国大陆地壳西厚东薄、南厚北薄,青藏高原地壳平均厚度为60~65 km,最厚达80 km;东部地区一般为30~35 km,南中国海中央海盆平均只有5 km;中国大陆地壳平均厚度为476 km,大大超过全球地壳392 km的平均厚度。中国大陆及邻区岩石圈亦呈西厚东薄、南厚北薄的变化趋势,青藏高原及西北地区岩石圈平均厚度为165 km,塔里木盆地中东部、帕米尔与昌都地区岩石圈厚度可达180~200 km。大兴安岭-太行山-武陵山以东,包括边缘海为岩石圈减薄区,厚度为50~85 km。西部岩石圈、软流圈“层状结构”明显,反映了板块碰撞汇聚的动力学环境;东部岩石圈、软流圈呈“块状镶嵌结构”,岩石圈薄,软流圈厚,反映了地壳拉张、软流圈物质上涌的特点,并在东亚及西太平洋地区85~250 km深处形成一巨型低速异常体。中国东部上、下地壳及地壳、岩石圈地幔之间普遍存在“上老下新”年龄结构。