The Zoulang Nanshan Caledonian Subduction Complex in the Northern Qilian Mountains and Its Dynamics1

Abstract The front of the Zoulang Nanshan Caledonian volcanic island arc zone in the northern Qilian Mountains is a forearc accretionary terrane, composed of multiple accretionary volcanic island arcs, flysch accretionary wedges, high - pressure metamorphosed detachment zones and remnants of ophiolites. It resulted from the northeastward subduction of the Early Palaeozoic Qilan oceanic crust beneath the Alxa block. High - pressure metamorphism, which occurred during the subduction, progressed through three stages: the initial stage of medium T - high P, the main stage of temperature decrease and pressure increase, and the lag stage of pressure decrease and temperature increase. Finally the paper presents a retrotrench subduction dynamic model indicative of northward subduction of the central Qilian block and southward accretion of the Alxa block during the period of 450-500 M a.     

The Zoulang Nanshan Caledonian Subduct ion Complex in the Northern Qilian Mountains and Its Dynamics

The front of the Zoulang Nanshan Caledonian volcanic island arc zone in the northern Qilian Mountains is a forearc accretionary terrane, composed of multiple accretionary volcanic island arcs, flysch accretionary wedges,high-pressure metamorphosed detachment zones and remnants of ophiolites. It resulted from the northeastward subduction of the Early Palaeozoic Qilan oceanic crust beneath the Alxa block. High-pressure metamorphism, which occurred during the subduction, progressed through three stages: the initial stage of medium T-high P,the main stage of temperature decrease and pressure increase, and the lag stage of pressure decrease and temperature increase. Finally the paper presents a retrotrench subduction dynamic model indicative of northward subduction of the central Qilian block and southward accretion of the Alxa block during the period of 450-500 Ma.     

The central Qiangtang Metamorphic Belt in northern Tibet is an in-situ Paleo-Tethys Ocean: Evidence from newly discovered Late Devonian radiolarians

The paleogeographic position of the North Qiangtang Block, as well as the origin of the Central Qiangtang Metamorphic Belt (CQMB) have subjected to considerable debate that hampers the understanding of the early evolution of the Paleo-Tethys Ocean. This study reports a new radiolarian fauna of a Famennian age (Late Devonian) from the ophiolitic mélange south of Gangtang Co, northern Tibet, including Callela parvispinosa Won, Entactinia foveolata Nazarov, and Plenoentactinia pinguis Won. The discovery of Devonian radiolarians in the CQMB strongly supports the model that the Longmu Co–Shuanghu suture zone represents the main branch of the Paleo-Tethys Ocean. A correlation of the Late Devonian radiolarian in Tethys realm reveals that the Longmu Co–Shuanghu suture zone was connected to the Changning–Menglian suture zone in western Yunnan, the Chiang Mai–Inthanon and Chanthaburi suture zones in Thailand, and the Bentong–Raub suture zone in Malay Peninsula. The synchronous advent of Late Devonian radiolarians suggests that the Paleo-Tethys Ocean may have opened during that time.     

On the biostratigraphy of accretionary complexes in the Far East (critical review of several papers)

Being a relatively simple geological discipline, biostratigraphy requires accuracy and sequential logic. The incorrect use of the biostratigraphic method and inaccurate interpretation of biostratigraphic data lead to a distorted understanding of regional tectonics. Frequently occurring errors are analyzed using three recently published works on biostratigraphy of accretionary complexes in the Russian Far East as an example.     

南羌塘增生过程的中-晚三叠世岩浆记录:藏北玛依岗日-角木日地区基性岩墙

古特提斯洋向北俯冲形成增生杂岩,它们向南增生构成了南羌塘增生地体,且增生期内发育的岩浆岩可以用来研究南羌塘的增生过程。在南羌塘增生杂岩带内,由北向南,发育有玛依岗日(MG)辉长岩墙、角木日(JM)辉长辉绿岩墙。锆石U-Pb测年结果显示,两者分别形成于237. 1±2. 3Ma和230. 7±1. 8Ma,为南羌塘增生期内岩浆岩。它们的岩石地球化学特征均介于OIB与E-MORB之间,富集Ti、Nb,以及LREE和LILE。Nd-Pb同位素结果显示两者均起源于富集地幔源区。Sm/YbLa/Yb图解显示,两者均起源于尖晶石-石榴石二辉橄榄岩源区,相对于JM辉长辉绿岩MG辉长岩部分熔融程度较高。两者Mg#和Ni、Cr特征表明,MG辉长岩分异程度高于JM辉长辉绿岩。Th/Nb-La/Nb图解显示,相对于JM辉长辉绿岩MG辉长岩经历了一定程度的地壳混染。综合研究认为,MG辉长岩和JM辉长辉绿岩为古特提斯洋壳俯冲过程中软流圈上涌的两次岩浆活动的产物,并受俯冲洋壳和地幔楔影响。MG辉长岩和JM辉长辉绿岩记录了南羌塘的增生过程,它们为相关研究提供了岩浆岩证据。     

Nature of accretion related to Paleo-Tethys subduction recorded in northern Thailand: Constraints from mélange kinematics and illite crystallinity

We reconstructed the accretion process related to Paleo-Tethys subduction recorded in northern Thailand, based on mélange and thrust structures, and metamorphic temperatures derived from illite crystallinity data. Mélange formation was characterized by hydrofracturing and cataclastic deformation, with mud injection under semi-lithified conditions followed by shear deformation and pressure solution. Illite crystallinity data suggest metamorphic temperatures below 250 °C during mélange formation. The combined structural and metamorphic data indicate that during mélange formation, the accretionary complex related to Paleo-Tethys subduction developed at shallow levels within an accretionary prism. Asymmetric shear fabrics in mélange indicate top-to-south shear. After correction for rotation associated with collision between the Indian and Eurasian continents, the trend of the Paleo-Tethys subduction zone is estimated to have been N80 °E. We conclude that the Paleo-Tethys was subducted northward beneath the Indochina Block from the Permian to Triassic.     

拉萨地块吉朗榴辉岩的岩石学研究及其对古特提斯洋壳俯冲折返过程的限定

拉萨地块东部松多(超)高压榴辉岩记录了古特提斯洋俯冲及折返过程。松多榴辉岩带已发现松多、新达多、白朗和吉朗4个榴辉岩出露区,它们的峰期温压条件及变质p-T轨迹的研究对揭示拉萨地块古特提斯时期的俯冲及折返过程有重要意义。松多榴辉岩带东段吉朗榴辉岩的主要矿物为石榴子石、绿辉石、多硅白云母、角闪石、金红石、绿帘石、石英以及退变形成的后成合晶结构(透辉石+角闪石+斜长石)和少量的黑云母。石榴子石具有含丰富矿物包裹体的"脏"核和极少包裹体的"净"边,具有典型的进变质成分环带特征,从核部到边部镁铝榴石组分升高,锰铝榴石和钙铝榴石组分降低。石榴子石边部发育窄的角闪石+斜长石(An=28)组成的冠状体,表明石榴子石边部发生了后期角闪岩相退变质作用。通过变质相平衡模拟计算得到石榴子石以及多硅白云母记录的峰期温压条件为563℃、2. 4 GPa。结合岩相学特征,确定吉朗榴辉岩经历了4期变质演化阶段:(1)进变质阶段以石榴子石核部及其包裹体为代表性矿物组合;(2)峰期变质阶段矿物组合为石榴子石边部、绿辉石、多硅白云母、蓝闪石、硬柱石、金红石和石英;(3)早期退变质阶段以硬柱石分解产生绿帘石为特征;(4)晚期退变质阶段以绿辉石发育后成合晶和石榴子石生长冠状体为特征。认为吉朗榴辉岩为典型的低温高压榴辉岩,经历了顺时针p-T演化轨迹,折返过程为近等温降压过程。与松多带内其他(超)高压岩石相比,吉朗榴辉岩峰期温压条件较低,其围岩为变石英岩,区别于区内其他(超)高压榴辉岩的石榴子石白云母片岩及蛇纹岩围岩。推测吉朗榴辉岩来自于俯冲带浅部,由俯冲隧道中低密度沉积物裹挟折返。     

Jurassic radiolarians and age of cherty rocks in the Povorotnyi Cape,the Taigonos Peninsula (northeast Russia)

Radiolaria-based dating of chert intercalations in basaltic sequences of ophiolitic associations, which are widespread in the west of circum-Pacific foldbelt being barren of macrofossils, is an important source of information about tectonic events and factors responsible for opening and destruction of basins floored by oceanic crust and for emplacement of relevant tectonic sheets into accretionary prisms and orogenic structures. Described in the work are the Middle (Bajocian-Callovian), Middle-Late (Callovian-Oxfordian) and Late Jurassic (Kimmeridgian-Tithonian) radiolarian assemblages. According to taxonomic composition and morphology of radiolarian tests, the first assemblage is of the North Tethyan type, while the other two are of the Boreal affinity.     

西南日本黒濑川带的解剖：晚二叠世和早侏罗世增生混杂岩的构造-地层学与浅变质作用

The Kurosegawa belt forms a relatively narrow terrane that can be traced continuously throughout southwest and central Japan. The major constituent continental fragments of the Kurosegawa belt include Early Paleozoic granitic rocks, high-grade metamor-phic rocks, Carboniferous metamorphic rocks (epi-dote-amphibolite facies), Triassic-Early Jurassic metamorphic rocks (pumpellyite-actinolite facies), serpentinites of unknown age, Silurian–Devonian volcanoclastic rocks intercalated with limestones, and Permian–Jurassic shallow marine sediments (e.g., Ichikawa et al., 1956; Maruyama et al., 1984; Faure, 1985; Yoshikura et al., 1990; Aitchison et al., 1991, 1996; Hada et al., 1992, 2001; Isozaki et al., 1992). These diverse rock suites are highly disrupted, form-ing lenticular bodies within the Late Permian accre-tionary complex (AC) which collectively are covered by younger (Cretaceous) marine to brackish water sediments (e.g., Aitchison et al., 1991; Isozaki et al., 1992). We characterize the tectono-stratigraphic ar-chitecture and low-grade metamorphism of the accre-tionary complex preserved in the Kurosegawa belt of the Kitagawa district in eastern Shikoku, Southwest Japan, in order to understand its internal structure, tectono-metamorphic evolution, and assessments of displacement of continental fragments within the complex.     

青藏高原中的古特提斯体制与增生造山作用

青藏高原古特提斯体系的特征表现为古特提斯洋盆中多条状地体的存在,多俯冲、多岛弧增生体系的形成和多地体汇聚、碰撞造山的动力学环境,其构架包括4条代表古特提斯洋壳残片的蛇绿岩或蛇绿混杂岩(昆南-阿尼玛卿蛇绿岩带、金沙江-哀牢山-松马蛇绿岩带、羌中-澜沧江-昌宁-孟连蛇绿岩带和松多蛇绿岩带)、5条火山岩浆岛弧带(布尔汗布达岛弧岩浆带、义敦火山岩浆岛弧带、江达-绿春火山岛弧带、东达山-云县火山岛弧带和左贡-临沧岛弧-碰撞岩浆带)、4个陆块或地体(松潘-甘孜地体、羌北-昌都-思茅地体、羌南-保山地体)、3条洋壳深俯冲形成的高压-超高压变质带(金沙江得荣高压变质带、龙木错-双湖高压变质带、松多高(超)压变质带),以及5条弧前增生楔或增生杂岩(西秦岭增生楔、巴颜喀拉-松潘-甘孜增生楔、金沙江增生楔、双湖-聂荣-吉塘-临沧增生楔、松多增生杂岩)。古特提斯洋盆的俯冲增生造山作用普遍存在于青藏高原古特提斯复合造山体中,构成与多条古特提斯蛇绿岩带(缝合带)相伴随的俯冲增生杂岩带(链)。古特提斯俯冲增生杂岩带包括由弧前强烈变形的沉积增生楔、以及高压变质岩、岛弧岩浆岩、蛇绿岩和外来岩块组成的混杂体,代表在洋盆俯冲过程中的活动陆缘的地壳增生。     

老挝琅勃拉邦—泰国黎府成矿带古特提斯构造-岩浆演化与金铜成矿作用

老挝琅勃拉邦—泰国黎府成矿带位于印支板块西北缘,是中南半岛重要的金铜成矿带之一。该带经历了晚古生代—中生代古特提斯构造-岩浆演化作用,成矿活动复杂,形成了斑岩-矽卡岩型金铜矿床、浅成低温热液型金银矿床以及热液脉型金矿床。然而,热液脉型金矿的成因类型仍存在争议,3类金铜矿床与区域构造演化的关系仍缺乏总结。本文通过对前人典型矿床研究资料的整理,并结合成矿流体来源、演化新证据,将带内热液脉型金矿床的成因类型归为造山型金矿。综合区域构造-岩浆-成矿作用研究资料,总结了成矿带内3类金铜矿床的时空分布规律和成矿特征,建立了与古特提斯洋俯冲-闭合及陆陆碰撞过程相关的区域金铜成矿模式,提出了晚二叠世—早三叠世俯冲期浅成低温热液型金银矿床、早中三叠世闭合期斑岩-矽卡岩型铜金矿床、晚三叠世陆陆碰撞期造山型金矿床的成矿规律。     

北祁连中段俯冲—增生杂岩／火山弧的时代探讨

北祁连中段俯冲－增生杂岩／火山弧由俯冲－增生杂岩和火山弧两个单元所组成，前者以早奥陶世具洋壳性质的蛇绿岩、蛇绿混杂岩及深海复理石为主体，夹中、晚寒武世大陆裂谷及洋陆过渡环境的火山岩及碎屑岩块。同位素年代学显示俯冲－增生杂岩的深部单元经历了４８９—４４０Ｍａ的ＨＰ／ＬＴ变质作用，而火山弧的形成时代为４９５—４６６Ｍａ，它们均形成于Ｏ１—Ｏ２期间早古生代祁连洋向北俯冲在阿拉善地块之下的俯冲作用     

西藏南羌塘晚三叠世陆缘俯冲增生造山带的褶皱-冲断与增生杂岩双层结构厘定

增生型造山带形成于活动大陆边缘,以宽阔且延伸稳定的增生杂岩为代表,在大洋板块向大陆板块发生缓慢而复杂的俯冲、碰撞过程中,大洋板块、火山岛弧、海山、大陆碎块等沿逐渐后退的海沟拼贴,仰冲板块前端发生刮削作用、底垫作用和构造剥蚀等作用,使得洋壳物质在海沟内壁增生,具体表现为增生杂岩的形成、垂向和侧向的生长,最终实现陆壳的横向生长。陆陆碰撞期间,加入俯冲通道的被动陆缘也将遭受类似的构造作用,从而形成规模较大的陆缘增生杂岩。因此,造山带增生杂岩的物质组成与结构、形成机制和演化过程对解剖洋陆转换过程中的复杂地球动力学过程具有极为关键的作用。西藏南羌塘增生杂岩是近年来通过走廊性地质填图以及多学科交叉工作得到的研究认识。然而,该增生杂岩的物质组成和结构等关键内容还未得到系统的研究,严重阻碍了对其形成机制和演化过程的理解。因此,本文以时空演化为主线,解剖杂岩物质组成和结构,结合俯冲期和同碰撞期大地构造单元,洞察南羌塘增生杂岩的形成演化过程。本次研究显示:(1)南羌塘增生杂岩具有俯冲杂岩在下、褶皱-冲断带在上的双层结构,二者间为大规模的拆离断层系统;(2)俯冲杂岩内不只含有洋板块地层单元,还含有大量的南羌塘被动陆缘物质;(3)褶皱-冲断带虽主要由被动陆缘物质变形改造而来,也含有属于洋板块地层系统的海山和洋内岛弧等物质。结合同俯冲期弧前盆地和楔顶盆地、同碰撞期晚三叠世岩浆的时空分布,高压变质岩的形成与折返时限,南羌塘增生杂岩内的双层结构应主要是陆陆碰撞过程中被动陆缘俯冲的结果,少量形成于大洋俯冲期间的俯冲反向过程中。本文提出的陆缘俯冲导致南羌塘增生杂岩双层结构的研究认识,对理解南羌塘地壳结构、中生代盆地基底形成演化具有较为重要的意义。     

昌宁-孟连杂岩带澜沧岩群的岩石学、地球化学和变质演化及其对古特提斯构造演化的启示

云南三江地区昌宁-孟连杂岩带中的澜沧岩群内出露多种类型变沉积岩,主要包括含十字蓝晶石榴云母片岩、石榴云母片岩、硬绿泥石白云母片岩和绿泥蓝闪钠长片岩等。系统的岩相学观察、矿物化学和相平衡模拟研究结果表明,不同类型的变沉积岩保存了不同的变质演化历史。含十字蓝晶石榴云母片岩记录了自中温榴辉岩相降温降压至角闪岩相的退变质过程,峰期矿物组合为石榴子石+蓝晶石+多硅白云母+硬玉,变质温压条件为600～750℃和19～30kbar。通过石榴子石的X_(Prp)和X_(Grs),和多硅白云母的Si值限定石榴云母片岩的峰期矿物组合包括石榴子石+多硅白云母+绿辉石+硬柱石+钠云母,峰期温压条件为430～475℃和17～19.5kbar。硬绿泥石白云母片岩矿物组成包括硬绿泥石+多硅白云母+钠云母,然而峰期矿物组合则以多硅白云母+钠云母+纤柱石为特征,通过多硅白云母的Si值限定峰期温压条件约为300～330℃和17～19kbar。石榴云母片岩和硬绿泥石白云母片岩较为一致地记录了从峰期硬柱石蓝片岩相升温降压至绿帘石蓝片岩相的退变质过程。绿泥蓝闪钠长片岩主要通过变质反应和成因矿物学特征大致估算其温压条件约为430～520℃和9～11kbar。岩石地球化学性质研究结果表明,这些变沉积岩的平均化学成分与大陆岛弧、活动大陆边缘和上地壳沉积物成分较为接近,其原岩主要为一套成熟度较差的泥砂质岩类和少量的中基性火山岩。该泥砂质原岩的沉积物源以中酸性岩浆岩为主,存在不同程度古老沉积物的加入。构造判别图解表明,研究区样品主要形成于大陆岛弧或活动大陆边缘的构造背景。变质作用特征和原岩地球化学属性综合分析表明,昌宁-孟连杂岩带内大面积分布的澜沧岩群均发生不同程度的俯冲-消减过程,表现出多样的变质演化P-T轨迹的特征,表明澜沧岩群经历了多期/多阶段复杂的构造演化历史。     

冷俯冲带深部的板块断裂过程——以日本中部侏罗纪燧石-碎屑岩杂岩体中的断裂带为例

近年来,深海大洋钻探已证实在洋陆俯冲带的浅部,板块边界断裂高度集中在特征性岩层中,然而对于这种断裂高度集中化现象是否发生在俯冲带深部仍然缺乏充分的认识,因此对日本中部侏罗纪燧石-碎屑岩杂岩体中一个露头宽度约50 m的断裂带进行了调查。该断裂带沿古俯冲带深部的板块边界延伸而出的逆冲断层发育,断裂带中的剪切变形集中在数层黑色有机质黏土岩中,表现为沿交织鳞片状叶理的分散剪切,剪切方向分为左行走滑和逆冲走滑,可能形成于俯冲带中的滑动分异或左行斜俯冲过程。体现滑动集中化的拆离面切割了黑色有机质黏土岩层,拆离面表现为左行滑动。利用碳物质拉曼光谱测量了拆离面上及黑色有机质黏土岩层中的碳物质。结果表明,相对于黑色有机质黏土岩,拆离面中的碳物质具有更高的成熟度,表明在左行滑动过程中产生了快速的摩擦升温。野外观测和实验结果表明,这一古断裂带记录的俯冲带深部板块边界断裂高度集中在黑色有机质黏土岩层中,发育于其中的拆离面的左行剪切可能产生于深部地震性滑动。     

Siliceous-volcanogenic complexes of western Sikhote Alin: Their stratigraphy and origin

New age and structural data are reported for the siliceous-volcanogenic complexes developed in the lower reaches of the Ussuri River. These complexes, which were previously treated as one stratigraphic unit, are subdivided into the Snarsky tectonostratigraphic complex (end of the Middle Jurassic-Middle Aptian) and the basaltic sequence (supposedly, Campanian-Maastrichtian). The Snarsky Complex is made up of basic volcanics, cherts, siliceous-clayey rocks, as well as subordinate limestones, sandstones, and conglomerates. Its distinctive features are the large amounts of genetically diverse basalts, the abundance of volcanomictic and pyroclastic material in siliceous-clayey rocks, the absence of fragmental rocks typical of the continental convergent zone, and the facies heterogeneity of the deposits. The complex is considered to be the southwestern continuation of the Kiselevka-Manoma terrane. Its origin is presumably related to the tectonic piling of genetically heterogeneous assemblages. The basaltic sequence includes basalts, basaltic andesites, their tuffs, and tuff conglomerates. The tuff conglomerates contain numerous fragments of granites and garnet-bearing felsic volcanics. The sequence was formed on the crystalline paleocontinental basement in the Late Cretaceous.     

川南大村区块五峰—龙马溪组页岩气成藏条件及勘探前景

近年来,深海大洋钻探已证实在洋陆俯冲带的浅部,板块边界断裂高度集中在特征性岩层中,然而对于这种断裂高度集中化现象是否发生在俯冲带深部仍然缺乏充分的认识,因此对日本中部侏罗纪燧石-碎屑岩杂岩体中一个露头宽度约50 m的断裂带进行了调查。该断裂带沿古俯冲带深部的板块边界延伸而出的逆冲断层发育,断裂带中的剪切变形集中在数层黑色有机质黏土岩中,表现为沿交织鳞片状叶理的分散剪切,剪切方向分为左行走滑和逆冲走滑,可能形成于俯冲带中的滑动分异或左行斜俯冲过程。体现滑动集中化的拆离面切割了黑色有机质黏土岩层,拆离面表现为左行滑动。利用碳物质拉曼光谱测量了拆离面上及黑色有机质黏土岩层中的碳物质。结果表明,相对于黑色有机质黏土岩,拆离面中的碳物质具有更高的成熟度,表明在左行滑动过程中产生了快速的摩擦升温。野外观测和实验结果表明,这一古断裂带记录的俯冲带深部板块边界断裂高度集中在黑色有机质黏土岩层中,发育于其中的拆离面的左行剪切可能产生于深部地震性滑动。     

俯冲增生杂岩带变形特征、成因机制及与后期变形的区别

俯冲增生杂岩带是造山带重要的组成单元,它记录了从俯冲到碰撞以及碰撞后陆内的演化历史,具有重要的研究价值。由于增生楔形成过程复杂,而后期的碰撞以及陆内变形又会强烈改造俯冲期的变形,因此如何区分增生杂岩中俯冲期间和碰撞阶段的变形就非常重要,但明确的区分两者又是非常困难的工作。我国几乎所有地区发育的俯冲-增生杂岩都经历了后期强烈的改造,因而正确合理地筛分俯冲阶段和碰撞阶段的变形,在我国的造山带研究中日益突出。本文在详细介绍俯冲期间相关变形及其机制的基础上,从不同构造要素的分布、发育特征、形成环境、成因机制等方面综合对比了俯冲阶段和碰撞阶段以及之后构造变形的异同,提出了区别不同阶段变形的主要原则。相比碰撞阶段变形,俯冲阶段的变形主要集中在俯冲隧道中,以简单剪切或一般剪切为主(逆冲断层多见),底板垫托以及双冲构造是变形的重要特征,变形呈弥散性,断层和面理以及褶皱等具有优势的构造极性,但缺少区域尺度的大型褶皱;纯剪变形少见,主要发育在俯冲隧道上方的增生楔中。流体作用以及水岩反应强烈,直接控制变形行为,发育有从显微尺度到区域尺度的变形分解现象。而碰撞阶段主要是在陆上环境进行,主要变形集中在接触带以及大型断裂/剪切带附近。断层和面理的构造极性不明显,增生楔整体变形,出现区域尺度的大型褶皱;流体作用虽有,但不如俯冲阶段明显和强烈,以逆冲和走滑断层多见。然而很多指标和依据并不是某种环境下唯一的,因此在实际工作中需要综合各方面信息和要素进行判断,合理区分不同阶段的变形。     

老挝-越南长山成矿带古特提斯构造岩浆演化与成矿作用

老挝-越南长山成矿带位于特提斯构造成矿域东南段,发育大量古特提斯旋回岩浆岩和铜-金-铁-锡等多金属矿床,是研究东特提斯构造岩浆演化与成矿作用的天然实验室。本文系统梳理了长山成矿带的成岩成矿时代、矿床组合和岩石地球化学研究成果,揭示了长山成矿带古特提斯时期的岩浆岩时空格架,构建了晚石炭—中二叠世(317~264 Ma)哀牢山-马江洋的俯冲、中二叠—晚三叠世(263~235 Ma)华南地体与印支地体的碰撞以及晚三叠世(234~202 Ma)碰撞后伸展等构造演化过程。初步建立了长山成矿带各阶段的成矿模式,包括俯冲期斑岩-矽卡岩型Fe-Cu-Au和浅成低温热液型Cu-Au-Ag成矿(305~279 Ma)、碰撞期斑岩-矽卡岩型Sn和矽卡岩型Fe-Au成矿(249~236 Ma)、伸展期热液脉型Au矿化(212~204 Ma)。受限于晚三叠世晚期岩浆活动和成矿作用研究资料的缺乏,碰撞后伸展阶段的成矿作用仍有待进一步研究。     

古特提斯洋的闭合时代的古地磁分析:松潘复理石杂岩形成的构造背景

对华南地块、塔里木地块和基墨里大陆(包括保山、缅泰和羌塘地块)进行了古纬度和纬度运移量的对比分析,以确定古特提斯洋盆的闭合时代。结果表明：①保山与华南地块于晚二叠世碰撞,然后继续和华南地块、缅泰地块一起向北漂移,直到晚三叠世,并导致华南地块与华北地块碰撞和秦岭—大别造山带的形成;②羌塘地块与塔里木地块碰撞发生在晚三叠世;古特提斯洋沿着保山地块东缘和羌塘地块北缘的闭合是不同时的,东早西晚;③华南地块向北漂移,可能引起了华南地块西部和东昆仑—柴达木地块南部的古特提斯洋北岸的凹入,这为松潘—甘孜海底扇的发育提供了空间;古特提斯洋闭合引起的俯冲造成了华南地块西部大陆边缘的裂离,也共同为海底扇的发育提供了空间。包括塔里木地块、华南地块、东昆仑—柴达木地块和羌塘地块在内的几个地块的合围,导致了松潘—甘孜地块三角形的构造形状。支持以前的假设：松潘—甘孜三叠纪复理石杂岩的物源来自华北地块南缘或秦岭—大别造山带。