Convergence History of the Songliao and Jiamusi Blocks in the Eastern End of Central Asian Orogenic Belt: Evidence from Detrital Zircons of Late Paleozoic Sedimentary Rocks

Central Asian Orogenic Belt(CAOB) is one of the largest accretionary orogenic belts in the world. The eastern segment of CAOB is dominated by Paleozoic Paleo Asian Ocean tectonic regime, Mesozoic Paleo-Pacific tectonic regime and Mongolian-Okhotsk tectonic regime. The Songliao and Jiamusi blocks are located in the easternmost part of the CAOB and are the key region to solve the problem about overprinting processes of multiple tectonic regimes. It is generally believed that the Mudanjiang Ocean between the two blocks was finally closed in the Mesozoic, but the Paleozoic magmatism also developed along the Mudanjiang suture zone, while on both sides of the suture zone, there were comparable Paleozoic strata, indicating that the two blocks had converged during the Paleozoic, and the evolution history of the two blocks in the Late Paleozoic remains controversial. The Carboniferous-Permian terrestrial strata mainly developed in Binxian, Wuchang and Tieli on Songliao Block, Baoqing and Mishan on Jiamusi Block. Samples from the Songliao and Jiamusi blocks in the Late Carboniferous-Early Permian and Late Permian are collected for comparative analysis. The LAICP-MS zircon U-Pb dating results show that the maximum depositional age of Middle Permian Tumenling Formation and Late Permian Hongshan Formation in Songliao Block is ～260 Ma, while that of Tatouhe Formation and Carboniferous strata in Jiamusi Block are ～290 Ma and ～300 Ma, respectively, which supports the previous stratigraphic division scheme. The age peaks of ～290–300 Ma, ～400 Ma, ～500 Ma appeared in the Late Carboniferous to Early Permian strata of Jiamusi Block and the Middle Permian strata of Songliao Block. The age peak of ～500 Ma in the Middle Permian strata of Songliao Block may come from the Cambrian basement, Mashan Complex, of Jiamusi Block, while the age peaks of ～420–440 Ma in the Carboniferous strata of Jiamusi Block may come from the Silurian magmatic arc in Zhangguangcai Range in the eastern margin of Songliao Block, reflects the history that they had been potential sources of each other, indicating that they may have combined in the Paleozoic. The Hongshan Formation of Songliao Block in the Late Permian lacks the age peak of ～500 Ma, which indicate that Jiamusi Block was not the provenance of Songliao Block in the Late Permian, that is, there was a palaeogeographic isolation between the two blocks. Combined with the ～210 Ma bimodal volcanic rocks developed along the Mudanjiang suture zone reported previously, we believe that the oceanic basin between the Songliao and Jiamusi blocks should have been connected in Late Permian and reopened during Late Permian to Late Triassic.     

班公湖-怒江洋打开时间的地层古生物约束

西藏班公湖-怒江洋的打开时间是争议性较大的科学问题。班公湖-怒江洋两侧的拉萨地块和南羌塘地块的古生物地理和地层层序的对比可以约束班公湖-怒江洋的形成时间。从地层层序上来看,拉萨地块在晚古生代大冰期结束之后是一由碎屑岩到碳酸盐转变的稳定地层序列;而南羌塘地块从早二叠世晚期开始东西向存在较大的相变,西部下二叠统吞龙共巴组之上存在间断面,不整合于上二叠统吉普日阿群之下;而东部下二叠统到中二叠统都是玄武岩和灰岩组成的鲁谷组。古生物地理上,南羌塘地块晚二叠世含有典型暖水的类Palaeofusulina动物群,与拉萨地块形成显著差别;南羌塘地块中二叠世主要的Eopolydiexodina类动物群也与拉萨地块的Nankinella-Chusenella类动物群产生明显差异;再者,南羌塘地块早二叠世晚期的类、珊瑚类和腕足类都呈现明显暖水的特征,但这些动物群在拉萨至今未有报道。综合南羌塘和拉萨地块地层层序、古生物地理特征上的差异,班公湖-怒江洋至少从中二叠世(～269Ma)就已经形成一定的规模。因此,班公湖-怒江洋在中二叠世以前和冰期结束之后的时间段内打开。     

龙木错-双湖-澜沧江板块缝合带与石炭二叠纪冈瓦纳北界

1982—1983年间,作者在改则幅和日土幅1:100万区域地质调查中,发现在黑头山—冈玛错—角木日—双湖一带,存在严重解体的蛇绿岩带。后经进一步工作,获悉该带明显地控制了冈瓦纳相和特提斯相石炭、二叠系的分布,并有高压变质带的岩石出露。因此,该带为一条北西西—南东东向的板块缝合带,它应是目前国内外地质界都在寻找的冈瓦纳大陆的北界。     

青藏高原羌塘中部高压变质带的研究进展及存在问题

羌塘中部高压变质带是目前青藏高原内部延伸规模最大的高压变质带,是理解特提斯演化的关键地质记录。高压变质带主要沿龙木措-双湖-澜沧江缝合带一线出露,主要由榴辉岩、蓝片岩、石榴子石多硅白云母片岩及少量高压麻粒岩组成。其中,榴辉岩主要出露于戈木、果干加年山、冈玛错、巴青及滇西的勐库地区,主要呈透镜状产于石榴子石多硅白云母片岩中。除巴青地区的榴辉岩外,其余地区榴辉岩的峰期变质温度较低且含有硬柱石及其假象,峰期变质条件位于硬柱石榴辉岩相稳定区域,是洋壳冷俯冲的产物。虽然对于戈木地区榴辉岩锆石成因仍有争议,但已有资料显示,羌塘中部高压变质带主体变质时代集中在晚三叠世,其相关高压变质岩石的折返可能与洋盆的闭合及随后的陆-陆碰撞相关。近期研究表明,羌塘中部可能存在二叠纪低温高压变质岩,折返于大洋俯冲阶段,可能与洋岛或海山的俯冲及引发的俯冲侵蚀作用相关。此外,羌塘香桃湖地区出露早古生代的基性高压麻粒岩,是冈瓦纳大陆北缘陆块拼贴的记录。因此,对羌塘中部高压变质带进行进一步系统的研究工作,对于深入理解冈瓦纳北缘构造演化及古特提斯的俯冲与闭合过程具有重要的意义。     

MAGMATIC ACTIVITY RELATED TO LATE PALEOZOIC RIFTING IN CENTRAL QIANGTANG PLATEAU

MAGMATIC ACTIVITY RELATED TO LATE PALEOZOIC RIFTING IN CENTRAL QIANGTANG PLATEAU     

青海可可西里大地构造基本特征

在可可西里地区发现的晚古生代蛇绿混杂岩及不整合于其上的晚二叠世—早三叠世海滩亚相石英砂岩表明此区曾存在过古特提斯洋,早二叠世末古特提斯基本闭合。晚二叠世—早三叠世为相对稳定阶段。中、晚三叠世海侵,沉积了巨厚复理石。三叠纪末—早侏罗世发生了强烈的造山作用,形成造山带,可可西里地区进入陆内演化阶段。     

西藏北羌塘中部地区晚石炭世的 类动物群

北羌塘中部晚石炭世地层,尤其是晚石炭世晚期地层是否存在,长期以来缺少确凿的古生物化石证据。1∶25万区域地质调查工作对该区石炭系的研究取得了突破,建立了瓦垄山组,划分了6个 类化石带,时代为早石炭世晚期至晚石炭世晚期,但缺少Protriticites与Triticites之间的Montiparus带。针对这一问题,对瓦垄山组命名剖面北侧的剖面进行了测制,发现了丰富的Montiparus属和Triticites属的分子,从而为北羌塘中部晚石炭世晚期地层的存在提供了翔实确切的 类化石证据。     

Paleozoic Stratigraphy in the Qiangtang Region of Tibet: Relations of the Gondwana and Yangtze Continents and Ocean Closure Near the End of the Carboniferous

Paleozoic sequences are defined for the northern and southern Qiangtang by linking field observations in the Gaize Province to the known Paleozoic record in neighboring areas. The pre-Devonian Gemuri Group of earlier authors is divided and the use of that term is no longer recommended. The upper Paleozoic rock assemblages, geological structures, and biota of the southern Qiangtang are of Gondwana glacial aspect, but those of the northern Qiangtang show more resemblance to those of the ancient Tethys. The two assemblages are interpreted as representing, respectively, the northern margin of Gondwanaland and the southwestern margin of the Yangtze continent. The two continents are suggested to have begun to separate during the Early Carboniferous and to have rejoined in the earliest Permian. Throughout this cycle of events, the northern Qiangtang occupied a passive margin while the southern Qiangtang rocks show evidence of the development of an active margin. Basaltic rocks from the southern Qiangtang are indicative of rifting. The authors consider that the boundary separating Car-boniferous and Permian rocks of Gondwanaland and Eurasia in the Qiangtang is marked by a suture zone that extends from Lungmuco through Heitonshan, Lake Gangma, Chasang, and Dongshuanghu. This suture is linked to Lancangjiang to the east and extends on to Malaya. In the Qiangtang the suture zone is marked by evidence of substantial rifting and by dismembered ophiolites.     

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.     

BASIN-RANGE TRANSITION AND GENETIC TYPES OF SEQUENCE BOUNDARY OF THE QIANGTANG BASIN IN NORTHERN TIBET

BASIN-RANGE TRANSITION AND GENETIC TYPES OF SEQUENCE BOUNDARY OF THE QIANGTANG BASIN IN NORTHERN TIBET     

Palaeozoic collisional tectonics and magmatism of the Chinese Tien Shan, central Asia

The Chinese Tien Shan range is a Palaeozoic orogenic belt which contains two collision zones. The older, southern collision accreted a north-facing passive continental margin on the north side of the Tarim Block to an active continental margin on the south side of an elongate continental tract, the Central Tien Shan. Collision occurred along the Qinbulak-Qawabulak Fault (Southern Tien Shan suture). The time of the collision is poorly constrained, but was probably in in the Late Devonian-Early Carboniferous. We propose this age because of a major disconformity at this time along the north side of the Tarim Block, and because the Youshugou ophiolite is imbricated with Middle Devonian sediments. A younger, probably Late Carboniferous-Early Permian collision along the North Tien Shan Fault (Northern Tien Shan suture) accreted the northern side of the Central Tien Shan to an island arc which lay to its north, the North Tien Shan arc. This collision is bracketed by the Middle Carboniferous termination of arc magmatism and the appearance of Late Carboniferous or Early Permian elastics in a foreland basin developed over the extinct arc. Thrust sheets generated by the collision are proposed as the tectonic load responsible for the subsidence of this basin. Post-collisional, but Palaeozoic, dextral shear occurred along the northern suture zone, this was accompanied by the intrusion of basic and acidic magmas in the Central Tien Shan. Late Palaeozoic basic igneous rocks from all three lithospheric blocks represented in the Tien Shan possess chemical characteristics associated with generation in supra-subduction zone environments, even though many post-date one or both collisions. Rocks from each block also possess distinctive trace element chemistries, which supports the three-fold structural division of the orogenic belt. It is unclear whether the chemical differences represent different source characteristics, or are due to different episodes of magmatism being juxtaposed by later dextral strike-slip fault motions. Because the southern collision zone in the Tien Shan is the older of the two, the Tarim Block sensu stricto collided not with the Eurasian landmass, but with a continental block which was itself separated from Eurasia by at least one ocean. The destruction of this ocean in Late Carboniferous-Early Permian times represented the final elimination of all oceanic basins from this part of central Asia.     

青海南部治多-杂多地区石炭纪-三叠纪砂岩地球化学特征与构造背景探讨

选取青海南部治多-杂多地区石炭纪-三叠纪的砂岩、粉砂岩样品,进行主量元素地球化学分析,利用分析结果判别物源区大地构造背景,探讨北羌塘盆地的性质及演化。研究结果表明:北羌塘中段的治多-杂多地区物源区大地构造背景早石炭世为被动大陆边缘;早中二叠世为被动大陆边缘、活动大陆边缘和大陆岛弧;晚三叠世为被动大陆边缘、活动大陆边缘和大陆岛弧。结合地层学、沉积学和岩石学,治多-杂多地区的沉积盆地经历了早石炭世被动陆缘克拉通盆地-早中二叠世裂陷盆地和早中三叠世被动边缘克拉通盆地-晚三叠世弧后前陆盆地的两个演化旋回,体现了金沙江缝合带和甘孜-理塘缝合带成生发展在研究区内的沉积响应。     

中国洋板块地层分布及构造演化

以大地构造相研究为主导,以《中国沉积大地构造图(1∶2 500 000)》编图为研究平台,对洋板块地层类型进行了初步划分,简述了中国新元古代以来洋板块地层分布及其构造演化规律。本文阐述了北方的古亚洲洋的洋陆转换从西往东具穿时现象,西部主要在早、晚石炭世之间,东部主要在中、晚二叠世之间;宽坪-佛子岭混杂岩带是华北与扬子之间大洋消亡的产物;中央造山带从北部的祁连-阿尔金到南部的昆仑-秦岭,洋陆转换从北向南依次完成：西昆仑北-阿尔金-祁连-祁曼塔格为晚奥陶世末,西昆仑南-东昆仑-秦岭为早三叠世末;青藏高原中部的龙木错-双湖、班公湖-怒江、昌宁-孟连蛇绿混杂岩带一起构成了原-古特提斯大洋连续演化、分阶段增生至最终消亡的对接带,洋壳持续时代自寒武纪-早白垩世;江绍-郴州-钦防混杂岩带是扬子陆块与华夏增生造山系之间华南洋最终消亡的对接带,主碰撞期是晚奥陶世-早志留世。     

西藏羌北地区石炭纪■类动物群及其分带

西藏羌北地区石炭纪■类动物群是笔者等于2004年首次发现的,并将动物群所在层位建立了瓦垄山组,该套地层中产大量的■类化石,种属多,分布连续。经研究,自下而上建立6个■类化石带:(1)Eosta ffella mosquensis带,(2)Millerella-Eostaf fella带,(3)Pseudostaf fella-Eostaf fella带,(4)Pro-fusuliena带,(5)Fusulina-Fusulinella带,(6)Protriticites-Triticites带。该套含竹蜓类化石地层的发现,为研究羌北地区晚古生代构造活动提供了信息,也为研究该区石炭纪地层、古生物、生物古地理、区域性地层划分和对比提供了依据。     

西藏羌北地区石炭纪(竹蜓)类动物群及其分带

西藏羌北地区石炭纪(竹蜓)类动物群是笔者等于2004年首次发现的,并将动物群所在层位建立了瓦垄山组,该套地层中产大量的(竹蜓)类化石,种属多,分布连续.经研究,自下而上建立6个(竹蜓)类化石带:(1)Eostaffella mosquensis带,(2)Millerella-Eostaffella带,(3)Pseudostaffella-Eostaffella带,(4)Profusuliena带,(5)Fusulina-Fusulinella带,(6)Protriticites-Triticites带.该套含(竹蜓)类化石地层的发现,为研究羌北地区晚古生代构造活动提供了信息,也为研究该区石炭纪地层、古生物、生物古地理、区域性地层划分和对比提供了依据.     

西藏羌塘中部绒马地区石榴蓝闪片岩变质演化过程的视剖面模拟及其意义

藏北羌塘地体中部产出一变质杂岩带,因其地貌突起,将羌塘地体一分为二,故常称其为羌中隆起带。虽然在该变质杂岩带中先后识别出蓝片岩、榴辉岩等变质岩,但对该变质杂岩带演化过程的认识却存在截然不同的观点,一种观点认为该变质杂岩带是原位的古特提斯板块缝合带的标志;另一观点则针锋相对,认为该变质杂岩带系外来的、底辟上升的杂岩带,不能作为古板块缝合带的证据。在该变质杂岩带中部的绒马乡,石榴蓝闪片岩呈大小不一的岩片和/或透镜体产出于石榴石多硅白云母石英片岩内,主要由石榴石变斑晶和由蓝闪石、绿泥石、白云母、绿帘石、石英、钠长石、金红石/钛铁矿、磷灰石、黑云母等矿物构成的基质组成。石榴石变斑晶粒径达2 mm,具典型的生长环带：核部富锰,锰铝榴石分子摩尔分数可达22%,至边部,铁铝榴石和镁铝榴石分子含量显著升高,而锰铝榴石分子含量则快速下降。石榴石变斑晶内部包体发育,可再细分为两类,一类包体产出于核部,包括被解释为硬柱石假象的细粒钠云母,绿帘石所构成的细粒板状集合体和细粒富铁蓝闪石、石英及金红石等包体;另一类包体则为数量较少的自形大颗粒绿帘石包体,产出于石榴石边部,在其内部还有细粒蓝闪石、金红石与石英等包体产出。基质中的角闪石可识别出3期：核部为富铁的蓝闪石,幔部为贫铁的蓝闪石,最外部为冻蓝闪石。基质中的绿帘石和绿泥石常为自形,绿帘石内常见细粒蓝闪石、石英、金红石等包体,而绿泥石边部常有黑云母的冠状体。在PEXPLE程序计算的p T视剖面图中,石榴石核部形成的p T条件为20 GPa、470 ℃,对应硬柱石榴辉岩相,而石榴石边部形成的p T条件为17~18 GPa、530~540 ℃,对应绿帘石榴辉岩相。岩相学观察与p T视剖面模拟研究充分反映了绒马地区石榴蓝闪片岩分别经历了硬柱石榴辉岩相、绿帘石榴辉岩相和近等温快速降压的退变质等变质过程,系冷洋壳快速俯冲与折返的产物,因此,文中支持该变质杂岩带为原位古特提斯板块缝合带的观点。硬柱石转变为绿帘石时,在俯冲通道中释放了大量的流体。T O视剖面研究进一步表明这种矿物相转变只发生于高氧逸度条件下,暗示所释放的流体可能也是高氧逸度流体。该高氧逸度流体可交代上覆地幔楔,并诱发后者发生部分熔融作用形成高氧逸度岩浆,如果这一推测是合理的,则羌塘地块内部应该存在斑岩型铜金矿床。 关键词：羌塘地体; 石榴蓝闪片岩; 视剖面模拟; 富氧流体     

西藏申扎地区拉嘎组岩相/沉积相分析

通过详细测制西藏申扎县扎扛-木纠错石炭二叠系剖面,查明了拉嘎组的岩石类型、组合及沉积环境。申扎地区的拉嘎组是以暗色粉砂岩、泥岩等细碎屑岩背景下,发育若干板状、长透镜状及透镜状粗碎屑岩为特征。大部分粗碎屑岩及部分细碎屑岩的分选及磨圆很差,成熟度极低,岩性显示为杂砾岩、杂砂岩,局部地区见有花岗岩漂砾。研究认为,拉嘎组形成于冰缘解冻并后退状态下的近岸冰海沉积环境,其沉积相类型可以分为分支水道与间湾、水下冰水扇、冰碛物与冰筏、滨岸与内陆棚。鉴于其时代可能为早二叠世Sakmarian期,因此,拉嘎组可能是晚古生代冰期消融的产物。拉嘎组沉积相的识别分析对拉萨地块晚古生代的古环境和古地理有重要意义。     

中国西南特提斯构造演化—幔柱构造控制

基于对中国西南特提斯巨型造山系的时空结构和构造－岩浆事件分析研究提出．泥盆－石炭纪时期出现于昌都－思茅陆块两侧的热幔柱导致了金沙江洋和澜沧江洋成对打开，热幔柱岩浆作用沿洋脊产出苦橄玄武岩和洋岛玄武岩，并造成区域地球化学异常。二叠纪末期出现于昌都－思茅－印支中央陆块下的冷幔柱导致了两大洋向该陆块下俯冲消减，陆块两缘发育沟－弧－盆体系，构成冷幔柱的洋壳板片在２００Ｍａ时期堆积沉落，诱发板块后继俯冲，产生滞后型孤火山－岩浆岩。发育于冈瓦纳大陆北缘的德干热幔柱在株罗纪导致怒江洋和雅鲁藏布江洋相继打开，在白垩纪末期（６６Ｍａ）形成德干玄武岩省。发育于劳亚大陆南缘的峨眉热幔柱在二叠纪，导致峨眉火成岩省的形成，在早中三叠世使甘孜－理塘断裂带扩张成洋。冷幔柱的持续发生，决定了雅鲁藏布江洋和甘孜－理塘向昌都－思茅陆块方向的俯冲消减，以及来自冈瓦纳大陆和劳亚大陆陆块分别向昌都－思茅陆块南北两侧拚贴和碰撞。     

Nature and evolution of the Neo-Tethys in central Tibet: synthesis of ophiolitic petrology,geochemistry, and geochronology

In this paper, we summarize results of studies on ophiolitic mélanges of the Bangong–Nujiang suture zone (BNSZ) and the Shiquanhe–Yongzhu–Jiali ophiolitic mélange belt (SYJMB) in central Tibet, and use these insights to constrain the nature and evolution of the Neo-Tethys oceanic basin in this region. The BNSZ is characterized by late Permian–Early Cretaceous ophiolitic fragments associated with thick sequences of Middle Triassic–Middle Jurassic flysch sediments. The BNSZ peridotites are similar to residual mantle related to mid-ocean-ridge basalts (MORBs) where the mantle was subsequently modified by interactions with the melt. The mafic rocks exhibit the mixing of various components, and the end-members range from MORB-types to island-arc tholeiites and ocean island basalts. The BNSZ ophiolites probably represent the main oceanic basin of the Neo-Tethys in central Tibet. The SYJMB ophiolitic sequences date from the Late Triassic to the Early Cretaceous, and they are dismembered and in fault contact with pre-Ordovician, Permian, and Jurassic–Early Cretaceous blocks. Geochemical and stratigraphic data are consistent with an origin in a short-lived intra-oceanic back-arc basin. The Neo-Tethys Ocean in central Tibet opened in the late Permian and widened during the Triassic. Southwards subduction started in the Late Triassic in the east and propagated westwards during the Jurassic. A short-lived back-arc basin developed in the middle and western parts of the oceanic basin from the Middle Jurassic to the Early Cretaceous. After the late Early Jurassic, the middle and western parts of the oceanic basin were subducted beneath the Southern Qiangtang terrane, separating the Nierong microcontinent from the Southern Qiangtang terrane. The closing of the Neo-Tethys Basin began in the east during the Early Jurassic and ended in the west during the early Late Cretaceous.     

Depositional environment and provenance of the upper Permian–Lower Triassic Tianquanshan Formation,northern Tibet: implications for the Palaeozoic evolution of the Southern Qiangtang,Lhasa, and Himalayan terranes in the Tibetan Plateau

Abstract

This article reports the depositional environment and provenance for the Tianquanshan Formation in the Longmuco–Shuanghu–Lancangjiang suture zone, and uses these to better understand the tectonic evolution of this region. Zircons in the andesite of the Tianquanshan Formation yielded concordia ages of 246, 247, and 254 Ma, indicating that the Tianquanshan Formation formed during the late Permian–Early Triassic. The Tianquanshan Formation consists of flysch and ocean island rock assemblages, indicating that the Longmuco–Shuanghu–Lancangjiang Palaeo-Tethys Ocean continued to exist as a mature ocean in the late Permian–Early Triassic. The detrital zircons in the greywackes of the Tianquanshan Formation yielded peak ages of 470–620, 710–830, 910–1080, 1450–1660, and 2400–2650 Ma, indicating the provenance of the Tianquanshan Formation was either Indian Gondwana or terranes that have an affinity with Indian Gondwana in the Tibetan Plateau (i.e. the Southern Qiangtang, Lhasa, and Himalayan terranes). The Ordovician quartzites, Carboniferous sandstones, Carboniferous–Permian diamictites, and the Upper Permian–Lower Triassic greywackes in the Southern Qiangtang, Lhasa, and Himalayan terranes all contain detrital zircons with youngest ages of ca. 470 Ma, indicating their source areas have been in a stable tectonic environment since the Ordovician, and this inference is supported by the continuous deposition in a littoral–neritic passive margin in these regions from the Ordovician to the lower Permian. Combining the present results with regional geological data, we infer that the Southern Qiangtang, Lhasa, and Himalayan terranes were all in a stable passive continental margin along the northern part of Indian Gondwana during the long period from the Ordovician to the early Permian. At early Permian, because of the opening of the Neo-Tethys Ocean, the tectonic framework of this region underwent a marked change to a rifting and active environment.