Multistage Deformation in the Northeastern Segment of the Jiangshao Fault (Suture) Belt: Constraints for the Relationship between the Yangtze Plate and the Cathaysia Old Land

Multistage deformation events have occurred in the northeastern Jiangshao Fault （Suture） Belt. The earliest two are ductile deformation events. The first is the ca. 820 Ma top-to-the-northwest ductile thrusting, which directly resulted from the collision between the Cathaysia Old Land and the Chencai Arc （？） during the Late Neoproterozoic, and the Jiangnan Orogenic Belt that formed as the ocean closed between the Yangtze Plate and the jointed Cathaysia Old Land and the Chencai Arc due to continuous compression. The second is the ductile left-lateral strike-slipping that occurred in the latest Early Paleozoic. Since the Jinning period, all deformation events represent the reactivation or inversion of intraplate structures due to the collisions between the North China and Yangtze plates during the Triassic and between the Philippine Sea and Eurasian plates during the Cenozoic. In the Triassic, brittle right-lateral strike-slipping and subsequent top-to-the south thrusting occurred along the whole northeastern Jiangshao Fault Zone because of the collision between the North China and Yangtze plates. In the Late Mesozoic, regional extension took place across southeastern China. In the Cenozoic, the collision between the Philippine Sea and Eurasian plates resulted in brittle thrusts along the whole Jiangnan Old land in the Miocene. The Jiangshao Fault Belt is a weak zone in the crust with long history, and its reactivation is one of important characteristics of the deformation in South China; however, late-stage deformation events did not occur beyond the Jiangnan Old Land and most of them are parallel to the strike of the Old Land, which is similar to the Cenozoic deformation in Central Asia. In addition, the Jiangnan old Land is not a collisional boundary between the Yangtze Plate and Cathaysia Old Land in the Triassic.

Tectonic implication of geomorphometric analyses along the Saravan Fault: evidence of a difference in tectonic movements between the Sistan Suture Zone and Makran Mountain Belt

In this paper, remote sensing techniques,as well as field studies, have been used to investigate the geomorphological processes and landscape evolution along the Saravan Fault, SE Iran to highlight how topographic features were influenced by active tectonics. Quantitative geomorphic analysis was carried out using mountain-front sinuosity(Smf),valley floor width-valley height ratio(Vf), drainage basin asymmetry factor(Af), Hypsometric integral(Hi), drainage basin shape index(Bs), mean axial slope of channel(MASC), standard deviation of topography(STD) and index of active tectonic(Iat).Remote sensing techniques, as well as field studies revealed that the Saravan Fault have three parts trending N-S, NW-SE, and E-W. Obtained results show that basins with high Iat index are located at where the strike of the Saravan Faults changes and where several strike-slip faults are crossed the Saravan fault.

Location of Triassic Tectonic Suture Between Collided Sino-Korean and Yangtze Cratons in Dabie-Sulu Region, China

The regional extent and spatial distribution of ultrahigh pressure metamorphic(UHPM) and high pressure metamorphic (HPM) rocks, and the geometrical relationships of various petrotectonic units in the Dabie-Sulu region indicate that the Triassic collisional suture line between the Sino-Korean and Yangtze cratons is situated at the northern margin of the Dabie massif, that is,along the Balifan-Mozitan-Xiaotian fault in the Dabie region, and possibly is linked to the Wulian-Yantai fault in the Sulu region to tbe east. The suture line has been strongly modified duriug and subsequent to UHPM aud HPM events.

Testing final closure time of the Paleo-Asian Ocean along the Solonker suture by a transition of compressional and extensional setting

The giant Central Asian Orogenic Belt is an extensive accretionary orogen,of which the Solonker suture,as a major regional suture,coincides closely with an early Permian paleobiogeographical boundary.This suture is considered to mark the location of the final closure of the Paleo-Asian Ocean between the North China Craton and the Mongolian Terrane.Although the closure time of the Paleo-Asian Ocean along the Solonker suture has generally been regarded as Late Permian-Early Triassic,uncertainty remains because of a lack of typical collisionrelated features(e.g.,high-grade regional metamorphism and well-developed fold-thrust structures)and a scarcity of outcrops.The present study reports Early Permian foliated gabbros and dikes(288-275 Ma)and Middle-Late Permian undeformed layered gabbros,strongly peraluminous granites,and I-type granites(265-254 Ma)in the Xinhure area along the northern margin of the North China Craton.The Early Permian foliated intrusions have a subduction-related geochemical signature and were derived from partial melting of lithospheric mantle modified by subduction-related melts or fluids at the active margin of the North China Craton.In contrast,the Late Permian undeformed layered gabbros and strongly peraluminous granites were derived from partial melting of lithospheric mantle and middle-upper crust,respectively,triggered by asthenospheric upwelling.Therefore,a transition from an end-compressional to an extensional environment according to a transition from collision termination to postcollision of the North China Craton and Mongolian Terrane may have occurred between 275 Ma and 262 Ma.This time span can be considered as the final closure time of the Paleo-Asian Ocean along the Solonker suture.

Location of the Suture Zone between the South and North China Blocks in Eastern Dabie Orogen

The Dabie Mountains are a collisional orogen between the South and North China blocks. The rock assemblages, isotopic dating and tectonic relationship of the tectonic-petrologic units in the eastern Dabie orogen indicate that the orogen is mainly composed of the different-grades metamorphic basement with minor low-grade metamorphic cover. No ophiolitic mélange and the Paleozoic volcanic-intrusive rock associated with the southern margin of the North China block were found there, suggesting that they belong to the northern margin of the South China block. The boundary between the tectonic-petrologic units is generally an extensional shear zone developed in the exhumation process of the ultrahigh pressure metamorphic rocks. In the northern part of the Dabie Mountains, the extensional-thrust and nappe structure represent the products of extensional tectonism. That is, there is no key tectonic boundary to indicate the occurrence of the suture zone there. Therefore, neither the Shuihou-Wuhe shear zone, nor the Mozitan-Xiaotian fault, is the suture zone between the South and North China blocks. The zone is believed to be at the front area of the Xinyang-Shucheng fault, covered by the Mesozoic-Cenozoic deposits within the Hefei basin.

Formation of South Tianshan suture and its geological significance

South Tianshan–Solonker suture,is the largest and southernmost suture within the Central Asian orogenic belt(CAOB).It records the ultimate collision between Tarim–North China cratons and Siberia craton,and is commonly interpreted as marking the eventual closure of Paleo-Asian Ocean.South Tianshan suture belongs to the western segment of the suture zone,and its evolutionary features are important for defining the formation age of the South Tianshan–Solonker suture.In this paper,the authors review the geochronological,geochemical,petrographic,and paleontological evidence within South Tianshan suture to delineate its formation era and closure characteristics,and thus further revealing the ultimate evolutionary pattern of the western segment of Paleo-Asian Ocean.This suture records strong plate collision before Late Carboniferous,forming a series of high-pressure metamorphic rocks,characterized by the presence of blue schist,eclogite and mica schist.In Permian,the whole area was under a relatively stable post-orogenic setting,with the formation of bimodal volcanic rocks,post-collisional granites,and terrestrial molasses.Sedimentary facies gradually changed from marine to either lacustrine or fluvial during this period.An Early Permian granite dike crosscuts the HP metamorphic belt,and the HP metamorphic rocks also underwent retrograde metamorphism at this time,indicating the formation of the South Tianshan suture was earlier than Permian.Hence,the western section of Paleo-Asian Ocean closed during Late Carboniferous,and Tarim Craton moved northward to collide with Kazakhstan–Yili Block,leading to the formation of the South Tianshan suture.

Structural Geology and Chronology of Shear Zones along the Shangdan Suture in Qinling Orogenic Belt,China:Implications for Late Mesozoic Intra-Continental Deformation of East Asia

The Shangdan suture zone(SDZ)in the Qinling orogenic belt(QOB)is a key to understanding the East Asia tectonic evolution.The SDZ gives information about convergent processes between the North China Block(NCB)and South China Block(SCB).In the Late Mesozoic,several shear zones evolved along the SDZ boundary that helps us comprehend the collisional deformation between the NCB and SCB,which was neglected in previous studies.These shear zones play an essential role in the tectonic evolution of the East Asia continents.This study focuses on the deformation and geochronology of two shear zones distributed along the SDZ,identified in the Shaliangzi and Maanqiao areas.The shear sense indicators and kinematic vorticity numbers(0.54–0.90)suggest these shear zones have sinistral shear and sub-simple shear deformation kinematics.The quartz’s dynamic recrystallization and c-axis fabric analysis in the Maanqiao shear zone(MSZ)revealed that the MSZ experienced deformation under green-schist facies conditions at∼400–500℃.The Shaliangzi shear zone deformed under amphibolite facies at∼500–700℃.The^(40)Ar/^(39)Ar(muscovite-biotite)dating of samples provided a plateau age of 121–123 Ma.Together with previously published data,our results concluded that QOB was dominated by compressional tectonics during the Late Early Cretaceous.Moreover,we suggested that the Siberian Block moved back to the south and Lhasa-Qiantang-Indochina Block to the north,which promoted intra-continental compressional tectonics.

印支造山带:Song Chay构造带

印支运动是二十世纪初法国地质学家根据越南北部晚三叠世大规模角度不整合所提出。越南北部的Song Chay构造带作为印支造山带概念的提出地,记录了大量经典的印支造山相关的信息,是理解印支造山带构造演化的关键地区。本文在课题组对Song Chay地区十多年研究基础上,结合前人研究成果,系统厘定了Song Chay构造带的几何空间格架、运动学特征及其演化过程。详细的野外地质考察表明,Song Chay构造带从SW向NE依次可以划分成:新生代的大象山单元、代表缝合带的Song Chay蛇绿混杂岩单元,以及越南东北部褶皱冲断系统。其中蛇绿混杂岩单元和褶皱冲断系统中发育NE-SW向矿物拉伸线理,并具有顶部向NE方向的剪切变形特征,指示了Song Chay洋壳向SW的俯冲以及向NE的逆冲过程。精确的年代学工作表明,Song Chay蛇绿混杂岩中斜长花岗岩的结晶年龄为356.4±2.9Ma,表明至少在早石炭世Song Chay洋就已经形成了成熟的大洋地壳。褶皱冲断带内部的低温年代学数据约束了顶部向NE的剪切变形年龄在250~245Ma之间,表明为华南和印支板块碰撞时间。另外,Song Chay蛇绿混杂岩基质中碎屑锆石物源研究表明,Song Chay蛇绿混杂岩基质中碎屑锆石主要是来自于俯冲的华南板块,只有很少一部分来自印支板块,因此推测Song Chay洋可能为一个十分有限的小洋盆。构造几何学、运动学以及碎屑锆石物源研究表明,在Song Chay构造带内的“滇-琼缝合带”两侧构造特征可对比,并未因“滇琼洋”的闭合而造成差异。因此,我们认为“滇-琼缝合带”并不能代表一个大洋。根据我们及前人的构造学、岩石学、年代学工作,建立了一个初步的Song Chay洋从晚石炭世至中三叠世的构造演化模型:(1)310~270Ma,Song Chay洋开始向SW俯冲到印支板块之下,此时岩浆弧并不发育,蛇绿混杂岩物源主要为华南板块;(2)270~250Ma,Song Chay洋继续俯冲,此时弧岩浆岩大量发育,蛇绿混杂岩同时接受弧岩浆岩及华南板块碎屑物质;(3)250~245Ma,Song Chay洋闭合,华南板块与印支板块碰撞;(4)245~230Ma,印支造山带进入碰撞后伸展阶段。

北澜沧江花岗岩地球化学特征及其构造意义

藏东地区广泛发育古特提斯花岗岩,如与金沙江缝合带相关的江达—维西花岗岩带和与甘孜—理塘缝合带相关的义敦花岗岩带。但是与龙木错—双湖(碧土)古特提斯主缝合带相关的北澜沧江花岗岩带并没有得到普遍认可。本文选取北澜沧江花岗岩带南端的碧罗雪山花岗岩展开研究,揭示其岩石学、年代学和地球化学特征,并进一步揭示其构造意义。岩石样品中锆石具有明显的岩浆岩振荡环带,年龄数据聚集在在217±1 Ma左右,ε_(Hf)(t)均值为-13.5,ε_(Nd)(t)值为-12.0,Sr-Nd-Hf同位素二阶段模式年龄均在2.0 Ga左右;岩石显微观察及地化特征表明岩石为花岗岩类,样品的岩浆来自具有古老地壳重熔成因的中上地壳酸性岩,构造判别图显示岩石为陆陆碰撞阶段花岗岩特征,这与主特提斯洋向东俯冲于兰坪—思茅地块之下以及随后发生陆陆碰撞的构造演化模型相契合。岩石地化特征和其构造位置支持碧罗雪山花岗岩带是北澜沧江花岗岩带的南端。由此,藏东地区存在一条长达700 km的花岗岩带,该花岗岩带从类乌齐、昌都吉塘、左贡东大山、芒康盐井、德钦梅里雪山延伸到维西碧罗雪山。碧罗雪山花岗岩的岩石年代学、地球化学数据为龙木措—双湖缝合带与昌宁—孟连缝合带的对接提供了详细的证据。

Study on thermal infrared remote sensing of Yarlung Zangbo River and Bangong Co-Nujiang River suture belt in Qinghai-Tibet Plateau

The area change of heat abnormity is not in accordance with conclusions of former thermal infrared remote sensing studies of the Qinghai-Tibet Plateau, which were that the temperature of Yarlung Zangbo River suture belt of the southern Plateau is high and the northern temperature is low. The study result in this paper shows that the highest temperature is found in the Bangong Co-Nujiang River suture belt, the Yarlung Zangbo River suture belt temperature is the second highest, and the northern Tibet temperature is the lowest. The study demonstration area was the suture belt areas of the Yarlung Zangbo River and the Bangong Co-Nujiang River in the Qinghai-Tibet Plateau, where the land temperature of the Qinghai-Tibet Plateau and the bore temperature of field land surface were measured and the emissivity of land surface was calculated. In addition, the authors explore the mechanism of the relationship between thermal infrared remote sensing and constructing thermodynamics and reach four new conclusions about the thermodynamics of the Tibet Plateau.

西秦岭南缘勉略构造带主要地质特征

西秦岭勉略构造带现今呈近东西—北西西向展布,是以自北而南多层次叠瓦状逆冲推覆构造为骨架的向南突出的巨型复合断裂弧形构造带。该带原为西秦岭微板块与扬子板块之间的古缝合带,发育有俯冲和碰撞两期变形构造,以主造山碰撞晚期的自北向南的逆冲推覆构造为显著特征。初步确定发育OIB以及N-MORB和E-MORB型玄武岩,代表了洋盆发育的物质记录。根据已有的年代学和古生物化石研究结果,认为于泥盆纪晚期—早石炭世(D3—C1)沿勉略带发育有以蛇绿岩、洋岛玄武岩为代表的有限洋盆。在勉略带扩张打开形成有限洋盆与消减俯冲过程中,南侧发育有被动陆缘盆地沉积体系,北侧发育有深水裂陷盆地和活动陆缘盆地沉积体系。进而确定勉略带是一条重要的东古特提斯北侧分支洋盆俯冲消减碰撞缝合带和中国大陆印支期完成其主体拼合的主要结合带之一。

秦岭勉县-略阳地区的构造混杂岩及其意义

秦岭造山带勉县长坝和略阳横现河地区发现的混杂岩均由不同性质的构造岩块和基质组成 ,混杂岩基质为受到不同变质作用的泥质岩或砂岩 ,属泥沙质混杂岩 ;构造岩块包括原地岩块和外来岩块两种基本类型 ,岩块大小不一 ,成分和形态复杂 ,在混杂岩中分布无序。两地区混杂岩普遍受到不同程度的褶皱变形和剪切作用 ,并且与两侧岩层以剪切带接触。综合研究表明长坝、横现河混杂岩明显区别于沉积成因的滑塌堆积 ,具典型构造混杂岩的性质特点 。

初论昆祁秦缝合系

中央造山带范围内的诸多新元古代晚期-早古生代蛇绿岩带可视为一个系统——昆祁秦缝合系。大致可分西、中、东3段。西段包括库地-苏巴什和麻扎-康西瓦2条缝合带及西昆中微地块;中段包括阿尔金、北祁连、柴达木北缘、祁漫塔格-乌妥及东昆仑南缘5条缝合带和中-南祁连、柴达木、阿牙克库木及玛沁4个较大的微地块及诸多较小的微地块;东段为商丹缝合带和勉略缝合带及其所夹持的秦中-大别微地块。昆祁秦缝合系是Rodinia超大陆经历了早-中震旦世（约780～600Ma）初期裂解阶段,晚震旦世-奥陶纪（约600～440Ma）昆祁秦多岛洋阶段,晚奥陶世-早志留纪（约440～400Ma）昆祁秦多岛洋闭合阶段形成的一个包含若干条缝合带和若干个微地块的体系,是中央造山带的基础。

西秦岭—东昆仑及邻近地区地壳结构——深地震宽角反射/折射剖面结果

在青藏高原东北缘，穿过阿尼玛卿缝合带东端完成了一条637km的近南北向深地震宽角反射，折射剖面．获得的地壳结构剖面表明，该地区Moho界面埋深48～51km，北浅南深，横向变化不大，而地壳内部构造在不同的地质构造块体差异明显．在下地壳内出现的两组能量较强的P3、P4波组，反映了研究区下地壳的反射性质和多层结构特征．阿坝弧形断裂以南和阿尼玛卿缝合带附近壳内界面变形强烈，壳内低速异常结构明显，特别是在缝合带下方20km以下的中下地壳异常的低速结构可以解释为存在延伸至中下地壳的破碎带构造特征．在剖面南段反映西秦岭褶皱带至松甘块体相应的地震记录出现复杂、强烈的中下地壳反射和相对较弱的Moho反射震相是该地区地壳结构的明显特征．

大巴山西段高川地体的构造变形特征及其意义

勉略缝合带是华北与华南大陆于印支期完成拼合的主要拼接带,在中国大陆的形成与演化中占据重要地位。但是,勉略带的东、西延伸至今没有确定的结论,尤其陕西省勉县以东到湖北随州一带,还没有找到确凿的缝合带的证据。已发表的文章多认为勉略带在勉县以东到达宁陕县两河口之后向南转折,沿着高川岩片的位置顺大巴山弧形构造带向东延伸到湖北随州一带。本文的研究表明,高川岩片是一个独立于大巴山构造带的外来地质体,称之为高川地体。高川地体是一个由近南北向右行走滑断层与轴向近南北向的走滑剪切褶皱构造组成的右行走滑构造系统,是大巴山冲断推覆构造向南推覆过程中从原勉略缝合带中挤过来的一片,仅仅是被挟持在大巴山冲断-推覆构造带与大巴山前陆构造带之间的地壳浅层地质体。因此,高川地体现在的位置不能代表勉略带向东的延伸,大巴山弧形构造带也不是中国南北大陆最终碰撞拼贴的位置。

秦岭商丹断裂带的构造样式与变形分析

商丹断裂带作为扬子板块与华北板块的缝合带,在秦岭造山带中占据重要的地位。对其进行精细的构造研究,是了解扬子板块与华北板块相互作用过程的关键。研究工作在商丹断裂带东段展开,对该带进行了详细的野外观察、显微构造观察、糜棱岩化过程中温度的估算、有限应变测量、差异应力的计算以及糜棱岩化过程中运动学涡度的计算。变形温压条件指示糜棱岩形成于中-高绿片岩相到低角闪岩相变质条件。差异应力计算结果指示商丹带具备大型构造动力特征。涡度分析表明该断裂带的变形以纯剪切作用占据主导作用,但包含有简单剪切的分量,从而证明了扬子板块与华北板块之间具有以碰撞挤压为主的斜向汇聚方式。

南秦岭构造带内早古生代碱基性岩浆活动:古特提斯洋裂解的证据

位于南秦岭构造带南缘的勉略（勉县—略阳）洋是东古特提斯洋的北侧分支洋盆,在勉县—略阳地区发育有典型的蛇绿岩组合.然而,由于中三叠世晚期开始的碰撞造山作用以及之后陆内变形作用的改造,对于勉略洋盆在构造带东段的裂解和演化过程并不清晰.本文对发育于东南秦岭构造带内的基性岩墙群进行了岩石学、岩石地球化学、同位素年代学等方面的研究.结果表明,基性岩脉以辉长岩、辉绿岩等基性岩为主,其SiO2含量为41.89％～49.75％,属基性—超基性岩类,并具有富钠、高钛的碱性岩特征.岩石的稀土、微量元素和Sr—Nd同位素特征与板内洋岛玄武岩（OIB）特征一致,岩浆源于具有地壳混染的板内洋岛玄武岩型地幔源区.该类基性岩脉顺层侵入到早古生代早期地层中,通过基性岩脉中的锆石SHRIMP测年获得岩脉顺层侵位的时代为晚志留世早期（约422 Ma）.这种岩浆作用很可能与古特提斯洋初始裂解有关,并导致南秦岭构造带内地壳伸展、基性岩浆侵位,该过程与南秦岭构造带北缘的商丹（商南—丹凤）原特提斯洋的消减和陆内俯冲可能相关.

秦岭-大别造山带中几条重要构造带的特征及其意义

目的研究秦岭—大别造山带内几条重要构造带的构造变形特征,以探讨其动力学过程。方法通过该造山带中各构造带的几何学、运动学特征研究,分析板块构造体系向陆内构造体系转换和大陆动力学体系演化等地质过程。结果①洛栾构造带是二郎坪弧后盆地与华北板块南缘的陆内构造拼合带,形成于365 Ma±,挤压方向为240→60°;②商丹断裂带在260 Ma±形成,挤压方向为220→40,°以压扁作用为主,正花状构造,显示出板块碰撞带的构造特征;③襄广断裂带是扬子板块在220 Ma±,由185→5°方向与大别造山带斜向汇聚的结果;④殷马断裂带为一条右行平移的韧性剪切带;⑤武穴构造对接带是大别造山带南缘与扬子板块北缘的构造复合带,是在140 Ma±扬子板块总体由S→N挤压所致;⑥宜鲁构造带是东秦岭造山带北界,为S→N逆冲的叠瓦状推覆构造,上地壳缩短率为52%;⑦郯庐断裂带是秦岭—大别造山带东端的一条多期活动的剪切带。结论秦岭—大别造山带经历了不同构造体制转换、板块构造系统发展、板块构造体系向陆内构造体系转换以及大陆动力学体系发展演化等地质过程;显示出古生代以来逆时针"转动挤压"到"三面围限"的动力学过程。

西昆仑山北部早古生代构造－岩浆带的发现

１９８７年以来，先后做了４条横穿昆仑山的综合路线地质调查。它们是：中－巴公路沿线；新－藏公路沿线；于田县普鲁村－苏巴什－硫磺达坂路线；青海茫崖镇－祁曼塔格路线。在西昆仑山北部的调查区内，都有钙－碱性的深成岩体出露。通过对这些岩体系统地做Ｕ－Ｐｂ、Ａｒ－Ａｒ及Ｒｂ－Ｓｒ定年研究，发现它们具有早古生代年龄（３８４—４８０Ｍａ），延伸上千公里，形成于活动大陆边缘或碰撞后的构造环境，常与属于蛇绿岩套的组分相伴生。这充分说明在青藏高原内部存在一条新发现的缝合带。

内蒙古锡林浩特—东乌旗剖面壳幔电性结构研究

为研究二连一东乌旗贺根山一带成矿构造环境,提供矿产资源勘查、预测、评价的地质背景依据,跨贺根山和锡林浩特板块缝合带一线布设了26个超宽频带长周期大地电磁测深点,点距3～6 km,剖面长度100 km,在对获取的资料采用Robust变换、互参考处理的基础上,定性分析了视电阻率和相位曲线、二维偏离度、电性主轴,并采用二维共轭梯度反演技术,解剖了沿剖面120 km深度的地壳、上地幔电性结构特征.反演结果表明,沿剖面以贺根山和锡林浩特缝合带为界分为壳幔结构差异较大的四大构造单元:锡林浩特缝合带南壳内高导层埋深约在25km,存在深达90 km的高阻块体;贺根山缝合带北壳内高导层埋深约15 km,莫霍面埋深约在50 km;两缝合带之间没发现壳内高导层,地壳表现为相对完整的高阻体;贺根山缝合带为两条岩石圈断裂控制,宽度约1 5 km,分布有串珠状局部南倾的高导体和上地幔局部隆起,下地壳底界约在25 km,上地幔高导层深度约在55 km,古亚洲洋壳向南俯冲迹象明显;锡林浩特缝合带盖层下宽度约6 km,与壳内高导层连通.缝合带位置均具备壳、幔源物质向上运移的通道,其控制的次级断裂构造系统具备成矿流体聚集、运移、沉淀成矿的有利条件,具备良好的成矿远景.