伊犁盆地南缘中-下侏罗统物源分析及其对南天山造山带演化的启示

伊犁盆地南缘中-下侏罗统碎屑岩的物源特征,可为南天山造山带的演化提供重要证据。对其碎屑岩锆石U-Pb定年研究结果表明,伊犁盆地南缘坎乡下侏罗统八道湾组砂岩的碎屑锆石年龄集中在290~260 Ma,而下侏罗统三工河组的碎屑锆石年龄集中在350~290 Ma和460~390 Ma,中侏罗统西山窑组的碎屑锆石年龄集中在370~320 Ma和450~390 Ma。所有测试样品中前寒武纪的年龄记录非常少。这些特征表明,伊犁盆地南缘中生代碎屑沉积物主要来自于伊犁-中天山地块南部。测试样品中几乎不存在晚二叠世-中三叠世的碎屑锆石,与南天山造山带的岩浆岩记录一致,暗示在晚二叠世-中三叠世南天山地区并没有发生强烈的与碰撞或后碰撞相关的岩浆活动。该结果不支持塔里木克拉通与伊犁-中天山地块在晚二叠世-中三叠世碰撞的观点。结合高压-超高压变质岩的数据和地层记录,认为塔里木克拉通与伊犁-中天山地块的碰撞发生在晚石炭世。同时,样品中最年轻锆石的年龄数据从早侏罗世到中侏罗世逐渐增大,显示了揭顶沉积的特点。对伊犁盆地南部中生代的锆石年龄数据与同时代南天山地区的锆石年龄数据进行综合对比表明在早-中侏罗世发生构造沉积夷平的特征。     

Decoding Provenance and Tectonothermal Events by Detrital Zircon Fission‐Track and U‐Pb Double Dating: A Case of the Southern Ordos Basin

Multi-dating on the same detrital grains allows for determining multiple different geo-thermochronological ages simultaneously and thus could provide more details about regional tectonics. In this paper, we carried out detrital zircon fission-track and U-Pb double dating on the Permian-Middle Triassic sediments from the southern Ordos Basin to decipher the tectonic information archived in the sediments of intracratonic basins. The detrital zircon U-Pb ages and fission-track ages, together with lag time analyses, indicate that the Permian-Middle Triassic sediments in the southern Ordos Basin are characterized by multiple provenances. The crystalline basement of the North China Craton (NCC) and recycled materials from pre-Permian sediments that were ultimately sourced from the basement of the NCC are the primary provenance, while the Permian magmatites in the northern margin of NCC and Early Paleozoic crystalline rocks in Qinling Orogenic Collage act as minor provenance. In addition, the detrital zircon fission-track age peaks reveal four major tectonothermal events, including the Late Triassic-Early Jurassic post-depositional tectonothermal event and three other tectonothermal events associated with source terrains. The Late Triassic-Early Jurassic (225–179 Ma) tectonothermal event was closely related to the upwelling of deep material and energy beneath the southwestern Ordos Basin due to the coeval northward subduction of the Yangze Block and the following collision of the Yangze Block and the NCC. The Mid-Late Permian (275–263 Ma) tectonothermal event was associated with coeval denudation in the northern part of the NCC and North Qinling terrane, resulting from the subduction of the Paleo-Asian Ocean and Tethys Ocean toward the NCC. The Late Devonian-early Late Carboniferous (348±33 Ma) tectonothermal event corresponded the long-term denudation in the hinterland and periphery of the NCC because of the arc-continent collisions in the northern and southern margins of the NCC. The Late Neoproterozoic (813–565 Ma) tectonothermal event was associated with formation of the Great Unconformity within the NCC and may be causally related to the Rodinia supercontinent breakup driven by a large-scale mantle upwelling.     

贺兰山北段晚三叠世沉积物源分析

贺兰山北段晚三叠世地层分布较广泛,其物源问题是进行鄂尔多斯盆地西北部原盆边界恢复和其两侧盆地该时期面貌恢复的关键,而对此存在一定的争议。该研究以贺兰山北段的沉积-构造背景为约束,通过晚三叠世地层的砾石成分、古流向、稀土元素、锆石测年及沉积趋势等物源分析方法综合运用,指出贺兰山北段晚三叠世不存在东部物源,银川古隆起不存在;物源来自西北部的阿拉善地块和兴蒙造山带太古代-古元古代的变质岩（片麻岩和变粒岩等）和岩浆岩,部分为阿拉善地块古生代和早中三叠世的沉积岩及岩浆岩。贺兰山西北部具有近物源和快速堆积的特点。同时,贺兰山北段晚三叠世物源具有多源性,其经历了多期的构造改造,恢复物源区演化模式对周邻造山带和块体的演化具有深远意义。     

Australian provenance for Upper Permian to Cretaceous rocks forming accretionary complexes on the New Zealand sector of the Gondwanaland margin

U–Pb (SHRIMP) detrital zircon age patterns are reported for 12 samples of Permian to Cretaceous turbiditic quartzo‐feldspathic sandstone from the Torlesse and Waipapa suspect terranes of New Zealand. Their major Permian to Triassic, and minor Early Palaeozoic and Mesoproterozoic, age components indicate that most sediment was probably derived from the Carboniferous to Triassic New England Orogen in northeastern Australia. Rapid deposition of voluminous Torlesse/Waipapa turbidite fans during the Late Permian to Late Triassic appears to have been directly linked to uplift and exhumation of the magmatically active orogen during the 265–230 Ma Hunter‐Bowen event. This period of cordilleran‐type orogeny allowed transport of large volumes of quartzo‐feldspathic sediment across the convergent Gondwanaland margin. Post‐Triassic depocentres also received (recycled?) sediment from the relict orogen as well as from Jurassic and Cretaceous volcanic provinces now offshore from southern Queensland and northern New South Wales. The detailed provenance‐age fingerprints provided by the detrital zircon data are also consistent with progressive southward derivation of sediment: from northeastern Queensland during the Permian, southeastern Queensland during the Triassic, and northeastern New South Wales — Lord Howe Rise — Norfolk Ridge during the Jurassic to Cretaceous. Although the dextral sense of displacement is consistent with the tectonic regime during this period, detailed characterisation of source terranes at this scale is hindered by the scarcity of published zircon age data for igneous and sedimentary rocks in Queensland and northern New South Wales. Mesoproterozoic and Neoproterozoic age components cannot be adequately matched with likely source terranes in the Australian‐Antarctic Precambrian craton, and it is possible they originated in the Proterozoic cores of the Cathaysia and Yangtze Blocks of southeast China.     

吐哈盆地及邻区早二叠世沉积特征与构造发育的耦合关系

通过对不同露头剖面和探井资料的分析,在吐哈盆地及邻区区分出三种不同类型沉积相：（1）裂谷型海相火山喷发沉积相;（2）裂谷型陆相火山喷发沉积相;（3）造山带磨拉石相;不同沉积相特征并结合构造分析认为,早二叠世在吐哈及邻区存在二种不同类型的盆地,即前陆盆地和裂谷盆地,同时,还探讨了大陆一大陆碰撞带上两种不同类型盆地的形成机理。     

Provenance analysis of the Paleozoic sequences of the northern Gondwana margin in NW Iberia: Passive margin to Variscan collision and orocline development

The Cantabrian Zone of NW Iberia preserves a voluminous, almost continuous, sedimentary sequence that ranges from Neoproterozoic to Early Permian in age. Its tectonic setting is controversial and recent hypotheses include (i) passive margin deposition along the northern margin of Gondwana or (ii) an active continental margin or (iii) a drifting ribbon continent. In this paper we present detrital zircon U–Pb laser ablation age data from 13 samples taken in detrital rocks from the Cantabrian Zone sequence ranging from Early Silurian to Early Permian in depositional age. The obtained results, together with previously published detrital zircon ages from Ediacaran–Ordovician strata, allow a comprehensive analysis of changing provenance through time. Collectively, these data indicate that this portion of Iberia was part of the passive margin of Gondwana at least from Ordovician to Late Devonian times. Zircon populations in all samples show strong similarities with the Sahara Craton and with zircons found in Libya, suggesting that NW Iberia occupied a paleoposition close to those regions of present-day northern Africa during this time interval. Changes in provenance in the Late Devonian are attributed to the onset of the collision between Gondwana and Laurussia.Additionally, the Middle Carboniferous to Permian samples record populations consistent with the recycling of older sedimentary sequences and exhumation of the igneous rocks formed before and during the Variscan orogeny. Late-Devonian to Permian samples yield zircon populations that reflect topographic changes produced during the Variscan orogeny and development of the lithospheric scale oroclinal buckling.     

准噶尔盆地南缘侏罗系碎屑成分特征及其对构造属性、盆山格局的指示意义

砂岩碎屑成分分析是进行沉积物源岩石类型、构造属性和盆山演化分析的重要途径。准噶尔盆地南缘侏罗系物源构造属性以“再旋回造山带”、“弧造山带”和部分“岩浆弧”物源为特征,物源岩石类型主要为中酸性岩浆岩、变质岩和沉积岩,岩石成分、重矿物含量及其组合显示东、西剖面在物源上存在一定差异。天山内部侏罗系物源构造属性以“再旋回造山带”、“混合造山带”为主,物源岩石类型主要为中酸性岩浆岩和变质岩,但各剖面的岩石成分、重矿物组合特征及相对含量差异较大。综合天山内部与准噶尔盆地南缘野外剖面沉积特征、岩屑成分及钻井岩心分析表明,天山地区早、中侏罗世盆山格局以盆地沉积范围大、天山正地形较小为特征,不存在地理分割明显的天山山脉,侏罗纪盆地南缘至少存在三个物源体系(西准噶尔山、克拉麦里山和(古)天山);晚侏罗世一早白垩世早期,岩石成分成熟度偏低,砾岩等粗碎屑沉积明显增多,同时不稳定重矿物及其组合稍有增加可能与晚侏罗世天山构造格局分异、构造活动相对活跃有关,天山山脉明显隆升并造就天山南北沉积环境的巨大差异。     

新疆库车盆地晚三叠世-早侏罗世沉积碎屑矿物成分及其物源区示踪与构造意义

通过同构造沉积物质记录了解物源区剥蚀作用过程进而探索盆山构造相互关系,是大陆构造动力学研究的一个重要方面。砂岩骨架成分分析和重矿物及部分标型矿物分析方法,已被较多地用来探索新疆天山造山带与其南部库车盆地晚中生代以来的相互关系和构造演变过程,但是关于中生代较早时期库车盆地构造属性及北部造山带隆升剥蚀过程的认识仍存在较大分歧。本文运用电子探针微区成分分析方法,对库车盆地北缘中段晚三叠世和早侏罗世砂岩中具代表性的15个砂岩样品中的38颗碎屑长石和26颗碎屑白云母矿物进行了矿物化学成分分析。结果表明,长石主要来自变质岩物源区,25颗碎屑白云母均属多硅白云母,表明其源区岩石曾经历了高压变质作用。这些多硅白云母中Si原子含量显示它们比目前保留在天山造山带高压变质带蓝片岩和榴辉岩中的多硅白云母形成的压力要低,可能反映了源区高压变质岩的正常剥露顺序。这项研究结果表明,至少在晚三叠世-早侏罗世时期,库车盆地北部天山造山带中的高压变质岩已经剥露于地表并遭受剥蚀成为物源供给区。具体是中天山南缘早古生代高压变质带还是晚古生代南天山高压变质带作为重要物源区,尚需进一步的研究工作。     

Mesozoic–Cenozoic sedimentary rock records and applications for provenance of sediments and affiliation of the Simao Terrane,SW China

ABSTRACT

As the north part of Simao Terrane, Lanping Basin is located between the Sanjiang Tethys Orogen (STO) and Yangtze Block, also the junction zone between the Gondwanaland and Cathaysian old land (Pan Huaxia mainland), which includes Yangtze and Cathaysian Blocks. The aim of this study is to decipher the provenance of the sedimentary units in the Lanping Basin and affiliation of Simao Terrane by the U-Pb ages, Hf isotope of detrital zircons and whole-rock geochemistry. The whole-rock geochemistry and the mineral composition indicate that most of the Triassic–Paleocene sedimentary rocks are derived from the upper crust and exhibit recycled orogen features. The detrital zircon U-Pb ages from the North Simao Terrane are consistent with the magmatic events during Early Neoproterozoic and Permian in the Western Yangtze Block. And the detrital zircons ages from North Simao Terrane show same distribution features as the Permian–Triassic magmatic rocks, which are distributed in the Simao Terrane and along major sutures. These comparisons suggest that the clastic sediments in Lanping Basin (North Simao Terrane) are derived from Early Neoproterozoic and Permian magmatic rocks from Western Yangtze Block, Permian–Triassic magmatic rocks from Simao Terrane, along Jinshajiang, Garz-Litang and Ailaoshan Sutures. The comparison of the detrital zircon age distributions shows that Simao Terrane and Yangtze Block exhibited similarity tectonic setting in the evolution history, especially during Paleoproterozoic–Late Paleozoic. This suggests that the Simao Terrane is part of Cathaysian old land, although Simao Terrane was separated from Yangtze Block for short period during Early Paleozoic. Besides, the Hf mapping, stratigraphic succession, paleogeography and paleomagnetism in SW China support that Simao Terrane has a Cathaysian old land-affinity, rather than one involving Gondwanaland.     

Topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins,Central Asia,from the Permian to the Neogene

The modern Tianshan Mountains and their surrounding basins have mainly been shaped by the far field effects of the Cenozoic India-Asia collision. However, precollision topographic evolution of the Tianshan Mountains and its impacts on the Junggar and Turpan Basins remain unclear due to the scarcity of data. Detrital zircon U-Pb dating of 14 new and 23 published samples from Permian to Neogene strata in the northern Western Tianshan Mountains, northern and southern Bogda Mountains and Central Turpan Basin, are combined with sedimentary characteristics (lithofacies, petrofacies and paleocurrent data) to investigate the temporal and spatial changes in sediment provenances. Based on the age characteristics of the source rocks in the Tianshan Mountains, the detrital zircons are divided into three groups: pre-Carboniferous zircons, mainly from the Central Tianshan Mountains; Carboniferous to Permian zircons, mainly from the North Tianshan and Bogda Mountains; and Mesozoic zircons, mainly from syn-depositional volcanic activity. The topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins can be generally divided into six stages. (1) Positive-relief Tianshan and Bogda Mountains and a rifted marine basin formed during the Early Permian to early Middle Permian following late Carboniferous orogenesis, as evidenced by interbedded alluvial fan conglomerates and postcollisional extension-related volcanic rocks along the basin margins, by marine deposits far from the basin margins and by the predominance of Carboniferous to Permian detrital zircons. (2) Fluvial to lacustrine deposits in the modern southern Junggar and Turpan Basins are characterized by abundant pre-Carboniferous zircons and consistently northward-flowing paleocurrents, indicating the submergence of the Bogda Mountains and a contiguous Junggar-Turpan continental depression basin during the late Middle Permian to the Triassic. (3) The Bogda Mountains began to uplift in the Early Jurassic, resulting in opposing paleocurrent directions, a sudden increase in sedimentary lithic detritus and the dominance of Carboniferous to Permian detrital zircons along the southern and northern margins of this range. (4) In contrast to the uplift of the Bogda Mountains, the other parts of the Tianshan Mountains experienced gradual peneplanation from the Early Jurassic to the Middle Jurassic, as confirmed by widespread fluvial to lacustrine deposits, even inside the modern Tianshan Mountains, and by the dominance of pre-Carboniferous detrital zircons. (5) The dominance of Carboniferous to Permian zircons in the southern Junggar Basin suggests the West Tianshan Mountains were uplifted during the Late Jurassic, while the dominance of pre-Carboniferous zircons in the Central Turpan Basin indicates continuous peneplanation in the Eastern Tianshan Mountains. (6) The initial shape of the Tianshan Mountains-Junggar Basin-Turpan Basin system was constructed in the Late Jurassic but was modified in the Cenozoic by the India-Asia collision, resulting in much higher Western Tianshan and Bogda Mountains, low Eastern Tianshan Mountains and well-developed foreland basins. These Cenozoic changes were recorded by the rapid cooling of apatites, the dominance of Carboniferous to Permian zircons in the southern Junggar Basin and northern Turpan Basin, and the dominance of pre-Carboniferous zircons in the Central Turpan Basin.     

罗布泊第四纪湖盆物源与盆地构造演化特征：来自LDK01孔碎屑锆石U-Pb年龄证据

为揭示罗布泊盐湖第四系潜在物源区及凹陷阶段性演化过程,本文对罗布泊第一口钾盐科探深钻LDK01孔更新统不同深度样品进行碎屑锆石U-Pb微区定年分析。Th/U比值显示,钻孔碎屑锆石类型主要为岩浆锆石,少量为变质成因锆石。锆石年龄主要集中在209~240Ma、265~304Ma、320~385Ma、406~446Ma、705~880Ma及2376~2405Ma几个区间。综合分析潜在物源区的岩石属性和年龄构成,初步认为罗布泊地区前寒武纪年龄来自北部山前库鲁克塔格地区,加里东期碎屑锆石可能来源于阿尔金造山带和(或)南天山构造带。276Ma的峰值记录了塔里木盆地二叠纪大火成岩省事件,南天山最有可能为主导物源区。印支期和新生代碎屑锆石年龄暗示了北山地块和东天山,甚至较远的帕米尔-西昆仑山等地可能也提供了物源。凹陷周缘富钾岩体广泛出露,经风化、淋滤搬运至罗布泊,为凹陷第四纪成钾提供了有利的物质来源。塔里木盆地内部流域带来的碎屑组分是主要的物质来源,近源地区造山带岩体提供的物源有限。碎屑锆石年龄纵向变化特征显示,罗布泊北部地区在中更新世发生一次明显的构造抬升,可能是导致罗北凹地形成的重要原因。     

天山南缘石炭系-三叠系碎屑岩成分及其对物源区大地构造属性的指示

本文通过对天山南缘石炭系-三叠系碎屑岩岩石学特征和地球化学特征的分析,揭示了研究区石炭系-三叠系碎屑岩的物质组分特征及其物源区的大地构造背景.碎屑岩的岩石学、地球化学分析表明,天山南缘石炭系、三叠系砂岩成分成熟度和结构成熟度均不高,杂基含量较高,从石炭系至三叠系砂岩不稳定组分依次增加.石炭系、二叠系具有相似的稀土元素含量特征,三叠系稀土元素含量明显低于石炭系和二叠系,石炭系-三叠系轻、重稀土元素分馏程度依次减弱,La/Th、La/Y 比值依次增大,Th/U比值减小,来自再旋回的物质依次增多.综合碎屑组分、常量元素、稀土元素及微量元素特征的判别,天山南缘石炭系物源区构造背景为既有指示大陆岛孤、活动大陆边缘的证据,也有指示为被动大陆边缘,二叠系物源区示为大陆岛弧,三叠系物源区示为大陆岛弧和含有古老沉积岩的陆块.对比石炭系、二叠系及三叠系物源区的大地构造属性,石炭系物源区示有多种属性,而二叠系、三叠系则相对较为单一,这可能与中天山-伊犁地块和塔里木陆块的碰撞有关.     

Provenance of Late Triassic sediments in central Lhasa terrane,Tibet and its implication

In southern Tibet, Late Triassic sequences are especially important to understanding the assembly of the Lhasa terrane prior to Indo-Asian collision. We report new data relevant to the provenance of a Late Triassic clastic sequence from the Mailonggang Formation in the central Lhasa terrane, Tibet. Petrographic studies and detrital heavy mineral assemblages indicate a proximal orogenic provenance, including volcanic, sedimentary and some ultramafic and metamorphic rocks. In situ detrital zircon Hf and U–Pb isotope data are consistent with derivation of these rocks from nearby Triassic magmatic rocks and basement that comprise part of the newly recognized Late Permian–Triassic Sumdo–Cuoqen orogenic belt. The new data suggests correlation with the Upper Triassic Langjiexue Group which lies on the opposing (southern) side of Indus–Yarlung ophiolite. Sediments from both the Mailonggang Formation and Langjiexue Group are interpreted to represent formerly contiguous parts of a sequence deposited on the southern flanks of the Sumdo–Cuoqen belt.     

准噶尔盆地南缘中-新生界碎屑成份特征与构造期次

准噶尔盆地南缘晚侏罗世-早白垩世早期、晚白垩世及晚新生代发育的近源粗碎屑沉积显示构造活动的存在。野外剖面及镜下碎屑成份统计表明:砾岩的砾石成份、砂岩碎屑成份的物源属性主要是再旋回造山带和晚古生代的岩浆弧,但盆地南缘东段与西段的岩屑组成及物源属性存在较大的差异。其中,沉积岩岩屑在晚侏罗世—早白垩世早期、晚白垩世和晚新生代发生了相应的增加,显示盆缘沉积岩物源的隆升—剥蚀作用和构造活动的相对活跃。砂岩碎屑特征、重矿物相对含量及重矿物组合特征证明盆地南缘东、西两段的物源属性存在较大差异,特别是不稳定重矿物的增加显示晚侏罗世-早白垩世早期、晚白垩世和晚新生代为构造相对活跃的构造环境。综合中-新生界沉积碎屑特征及差异分析,准噶尔盆地南缘中-新生代盆山格局发生了3次较大的转变过程,分别对应于上述3个时期。中-新生代3次构造活动对含油气系统形成具有重要控制作用,构造活动期次与油气藏形成、调整的期次也有良好的对应关系。     

松潘-甘孜褶皱带南部上三叠统物源及构造抬升:碎屑锆石年代学和Hf同位素证据

碎屑锆石年代学不但能够限定地层沉积开始的最大时限,还能为示踪沉积物源区提供关键信息。中国西南部的松潘-甘孜褶皱带广泛出露一套巨厚的三叠纪复理石沉积,其物源区和可能存在的同期抬升与剥蚀历史并未得到很好约束。本文获得的松潘-甘孜褶皱带南部雅江地区上三叠统四套地层（由老至新分别为侏倭组、新都桥组、两河口组和雅江组）5件砂岩样品的碎屑锆石U-Pb年龄和锆石Hf同位素数据表明,最年轻锆石年龄指示侏倭组从~229Ma后开始沉积,新都桥组则从~223Ma后开始沉积。碎屑锆石年龄频谱图显示四套地层都具有中奥陶世-早泥盆世（465~398Ma）和中二叠世-晚三叠世（271~225Ma）的年龄峰。除两河口组外的其他三套地层还具有较强的古元古代（1.90~1.86Ga）和新元古代（872~712Ma）的年龄峰。锆石Hf同位素显示松潘-甘孜褶皱带南部上三叠统小于300Ma的锆石颗粒主要来自峨眉山大火成岩省和义敦岩浆弧。本文物源区示踪结果表明,华南板块和义敦地体可能为松潘-甘孜褶皱带南部地层的主要物源区。晚三叠世由于周缘地体的强烈汇聚,松潘-甘孜褶皱带在小于~18Myr的时间内经历了快速的隆升和剥蚀作用,剥蚀产生的碎屑物质被搬运至四川盆地的西缘再沉积。     

Jurassic uplift and erosion of the northeast Queensland continental margin: evidence from (U–Th)/He thermochronology combined with U–Pb detrital zircon age spectra

Abstract

The Jurassic–Cretaceous Great Artesian Basin is the most extensive, and largest volume, sedimentary feature of continental Australia. The source of its mud-dominated Cretaceous infill is attributed largely to contemporary magmatism along the continental margin to the east, but the source of its Jurassic infill, dominated by quartz sandstone, remains unconstrained. This paper investigates the question of a Jurassic sediment source for the northern part of the basin. Jurassic uplift and exhumation of the continental margin crustal sector to the east provided the primary Jurassic sediment source. (U–Th)/He data are presented for zircon and apatite from Pennsylvanian to mid Permian granitoids of the Kennedy Igneous Association distributed within the northern Tasmanides between the Townsville and Cairns regions and for coeval granites of the Urannha batholith from the Mount Carlton district (N Bowen Basin), also within the northern Tasmanides. The data from zircon indicate widespread Jurassic exhumation of a crustal tract located to the east of the northern Great Artesian Basin and largely occupied by rocks of the Tasmanides. Detrital zircon age spectra for samples of the Jurassic Hutton and Blantyre sandstones from the northeastern margin of the Great Artesian Basin show their derivation to be largely from rocks of the northern Tasmanides. In combination, the detrital age spectra and (U–Th)/He data from zircon indicate exhumation owing to uplift generating appreciable physiographic relief along the north Queensland continental margin during the Jurassic, shedding sediment westward into the Great Artesian Basin during its early development. A portion of (U–Th)/He data for zircon are consistent with late Permian–mid Triassic exhumation within the Tasmanides, attributable to the influence of the Hunter--Bowen Orogeny. Evidence of Cretaceous and Paleocene exhumation episodes is also indicated for some samples, mainly by apatite (U–Th)/He analysis, consistent with data previously published from fission track studies. Overall, new data from the present study reveal that the exhumation related to Jurassic regional uplift and the subsequent erosional reworking of the northeast Australian continental margin is critical for the evolution and development of the northern side of the Great Artesian Basin in eastern Australia. Apart from this, another two previously suggested Permian–Triassic and Cretaceous exhumation and uplift episodes along the northeast Australian continental margin are also confirmed by the dataset of this study.

1. KEY POINTS

2. U–Pb detrital zircon ages of sandstone samples from the northeastern Eromanga Basin reveal Paleozoic (480–280 Ma) and Proterozoic (1800–1400 Ma) age clusters.

3. (U–Th)/He zircon and apatite dating results of granitoids samples from Cairns, Townsville and the Mount Carlton districts are dominated by Jurassic (198–164 Ma) and Permian–Triassic (272–238 Ma) age clusters.

4. Combination of above two datasets proves the regional uplift-driving Jurassic exhumation episode in the northeast Australian continental is vital for the development of the northern Great Artesian Basin.

     

鄂尔多斯盆地塔然高勒地区直罗组砂岩源区构造背景与物源分析

目前关于鄂尔多斯盆地塔然高勒地区直罗组沉积期物源和区域沉积-构造背景等问题尚缺研究,在一定程度上制约了直罗组物源变化的整体评价.对塔然高勒地区含铀层位直罗组下段砂岩进行了岩石地球化学、碎屑锆石U-Pb测年研究.结果显示,研究区直罗组下段源区岩石类型主要为长英质沉积岩和少量中性岩浆岩;源岩构造背景为活动大陆边缘-大陆边缘弧环境.综合微量、稀土元素特征和获得的锆石U-Pb定年数据,认为塔然高勒地区直罗组的物源主要来自大青山-乌拉山等地区的孔兹岩、TTG片麻岩、麻粒岩和镁铁质-超镁铁质层状侵入岩以及阴山地区形成于华力西期-印支期-燕山期的岩浆岩,直罗组下段砂体展布特征清楚地反映了研究区及相邻铀矿床由北向南的物源供给方向;研究区直罗组下段发现的三叠纪碎屑锆石表明三叠纪时期直罗组下段沉积时印支期侵入岩已被抬升至地表提供了物源,直罗组下段上亚段的年轻物源组分比例比下亚段的大.      

Evolution of exhumation and erosion in western West Gondwanaland as recorded by detrital zircons of late Neoproterozoic and Cambrian sedimentary rocks of NW and Central Argentina

The evolution of the provenance areas for Late Neoproterozoic, Cambrian and Early Ordovician sedimentary and meta-sedimentary rocks of north central and northwest Argentina is discussed using 123 maximum ages of detrital zircons from 42 samples from this and previously published studies. Most detrital zircon ages fall into two groups: 1,200–900 Ma and 670–545 Ma. These ages are essentially identical for the non- to very low grade metamorphic late Neoproterozoic to Early Cambrian Puncoviscana Formation and the low to high grade metamorphic rocks of Eastern Sierras Pampeanas. Hence, both units are related to similar provenance areas at the same time of sedimentation. The time span from zircon crystallization in the Earth’s crust to exhumation and erosion may be very long. This is important when determining maximum ages of sedimentary rocks. Variation of zircon maxima may also be influenced by concurrent sedimentary cover of proposed provenance areas. For the late Mesoproterozoic to early Neoproterozoic zircon age group, an active mountain range of the southwest Brazilian Sunsás orogen is the most probable provenance area. The younger, late Neoproterozoic zircons are related to the continuously developing mountains of the Brasiliano orogen of southwest and south central Brazil. Young zircons, up to 514 Ma, from fossil-bearing Puncoviscana and Suncho Formation outcrops are related to late Early Cambrian volcanism contemporaneous with sedimentation. This situation continues through the Late Cambrian to the Early Ordovician, but the Sunsás orogen provenance diminishes as possible Río de la Plata craton origins become important.     

华北盆地三叠纪物源特征及其沉积—构造演化

华北盆地三叠纪沉积厚度大,分布广泛,其地层沉积特征很好地记录了周缘造山带或隆起区在该时期的构造演化过程。目前,前人已经对华北各地区三叠纪碎屑物源进行了大量研究,而对于物源区的认识仍存在分歧,对于盆缘地区沉积—构造演化过程的研究也相对较少。通过整理前人对华北各地区三叠纪碎屑物源研究的锆石年龄数据,并结合造山带构造演化过程和地层沉积特征,对华北盆地三叠纪碎屑物源及沉积—构造演化过程进行了整体研究。结果表明:华北北部三叠纪沉积物源均来自北缘的内蒙古隆起,锆石年龄和地层沉积特征记录了源区逐渐增强的岩浆活动和隆升过程。华北南部地区在该时期主要接受来自华北南缘二叠纪沉积盖层和北秦岭造山带的碎屑物质供给,华北南缘伴随着秦岭造山过程可能在中三叠世就已经逆冲隆升并遭受剥蚀,两者的协同演变共同控制着盆地南部沉积演化过程。鄂尔多斯盆地西北部碎屑物源主要来自阿拉善地块和北祁连造山带,西南部地区物源则主要来自盆地西南缘再旋回沉积盖层和北祁连造山带,分别为伸展和挤压状态下的内陆盆地沉积。早—中三叠世,华北盆地为统一的大型内陆沉积盆地,晚三叠世,盆地南、北缘发育沿褶皱逆冲带分布的陆内前陆盆地系统。     

准噶尔盆地南缘中-新生界碎屑锆石的U-Pb 年代学和沉积学记录及其反映的盆山构造演化

针对准噶尔盆地南缘(天山北麓)中生界及新生界4个砂岩样品的碎屑锆石,本文开展了LA-ICP-MS分析,解析了其U-Pb年代学、沉积物源及其构造属性等信息,探索了天山及其邻近盆地的表壳演化过程及动力学机制。研究显示,准噶尔盆地南缘上三叠统-中侏罗统碎屑锆石年龄构成总体宽泛复杂,在490～160 Ma之间出现多个谱峰:除310～260 Ma主峰外,尚有180～160 Ma、240～210 Ma、370～340 Ma、450～390 Ma和490～460 Ma等5个次峰; 上侏罗统-下白垩统碎屑锆石年龄构成相对简单,但仍然保留400～250 Ma较宽范围内的2～3个谱峰:除310～260 Ma主峰外,尚有340～315 Ma等次峰; 上白垩统-古近统,主物源碎屑锆石年龄构成趋向单一,峰值区间集中于310～260 Ma。研究说明天山与准噶尔盆地之间的构造分异活动可以分为4个阶段:中晚三叠世-中侏罗世平稳或渐弱,向准噶尔盆地输运碎屑物的天山水系较宽,可达南天山北缘; 晚侏罗世-早白垩世欧亚板块与拉萨块体碰撞的远程效应对天山古生代构造格局造成了强烈的叠加改造,天山区域整体抬升剥露加剧,并伴随主分水岭相对北移; 晚白垩世-古近纪北天山继续隆升(尽管相对变弱),并直接构成向准噶尔盆地(南缘)输运碎屑物的主水系,新近纪由于欧亚板块与印度板块碰撞引发的天山陆内强烈隆升并未明显改变这一物源输运系统。