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1.
鄂尔多斯盆地西南缘下-中侏罗统碎屑锆石U-Pb年代学及其地质意义 总被引：1，自引：0，他引：1
改造盆地主要发育时期原始沉积边界的厘定具有重要的油气地质和区域构造意义。物源分析是厘定盆地原始沉积边界的重要内容和有效手段。对鄂尔多斯盆地西南缘邻区下-中侏罗统砂岩碎屑锆石LA-ICP-MS U-Pb年龄谱的研究,为厘定盆地西南沉积边界提供了新的依据。盆地西南缘六盘山地区上流水和炭山剖面的下-中侏罗统延安组砂岩碎屑锆石年龄谱较为相似,而与靖远地区红会四矿剖面同期地层的碎屑锆石年龄谱相差较大。将这三区碎屑锆石的年龄谱与周邻构造单元结晶岩体的年龄对比表明,早-中侏罗世期间靖远地区沉积物来源于西南侧的祁连造山带,而六盘山地区沉积物来源于西北侧阿拉善地块和北侧的华北克拉通北缘。对物源、地层厚度、岩性、煤层特征等差异的综合研究认为,这两个地区在早-中侏罗世期间属不同沉积域,鄂尔多斯盆地的西南沉积边界为海原断裂带。 相似文献
2.
《地学前缘(英文版)》2019,10(6):2287-2300
The Sulu orogenic belt (SOB) separates the North and South China blocks in East Asia and formed during Triassic continent-continent collision. However, late Mesozoic post-collisional exhumation is poorly understood due to lack of surface evidence for Paleo-Pacific subduction and associated effects. This paper interprets the tectonic history of the SOB using detrital zircon age data from Early Cretaceous sedimentary units along with previously published geochronologic and geochemical data to reconstruct sedimentological and tectonic history. Detrital zircon age distributions obtained from sedimentary units include a 2.0 Ga subpopulation that appears only in turbidite units to the southeast. This sediment probably derived from the Yangtze Block. Terrestrial facies from the Jiao-Lai basin to the northwest appear to derive from the North China Block. Geochronologic and geochemical data indicate that Early Cretaceous, post-collisional volcanism was compositionally bimodal (mafic-felsic) with associated intrusive activity that peaked at 120 Ma. Seismic images of northerly regions of the study area indicate this occurred in an extensional setting. Sedimentary facies and field structural analyses revealed an unconformity interpreted to reflect rapid uplift with NW–SE compression to the south. Given observed sinistral movement along the Tan-Lu fault, we interpret northwest and southeast regions of the SOB as experiencing transtensional and transpressional tectonics, respectively, driven by continuous subduction of the Paleo-Pacific Plate. Intrusion of the Late Yanshannian granitoids marked the final formational stage of this unique tectonic setting. 相似文献
3.
Paleoproterozoic orogens of the North Australian Craton are related to the assembly of the Columbia Supercontinent. The roles of the distinct orogens in the Paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure. The age and isotopic systematics of detrital zircon grains hosted in Paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton, in terms of paleogeography and tectonic setting. The oldest (Early Paleoproterozoic) metasedimentary units are characterised by detrital zircon ages peaking at ca. 2500 Ma. The zircon εHf values show large variations in the different orogens and range from −18 to +6. The overlaying youngest turbiditic units show minor accumulation of Archean detritus. Units from apparently different metasedimentary sequences have a major detrital zircon age population at ca. 1865 Ma, and a relatively restricted range of zircon εHf values between −7.3 and +2.6. The isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment, probably due to horst-graben architecture of the early Paleoproterozoic basin. The youngest turbiditic units blanketed this early horst-graben architecture and in part have a local provenance. Potential detritus sources include South Australian Craton, Dharwar Craton and Aravalli-Lesser Himalayan terrains in India, South China, and Madagascar (Africa). This finding indicates that these regions might have been connected before the Columbia Supercontinent was formed. The ubiquitous ca. 2500 Ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called Kernorland. In addition, the data do not support a proximity of the North Australian Craton with the North China Block, Western Laurentia (North America), and Kaapvaal Craton (Africa) during Columbia amalgamation. 相似文献
4.
以西秦岭舒家坝地区泥盆纪舒家坝群碎屑岩为研究对象,进行碎屑锆石LA-ICP-MS U-Pb年龄研究,探讨其形成时代、物源组成和构造背景。所测样品最小锆石年龄组的年龄加权平均值为413Ma,代表了舒家坝群的沉积下限,结合前人研究的古生物资料将其形成时代限定为中泥盆世。所获碎屑锆石年龄可划分为4个谱段：震旦纪—古生代年龄谱段619～409Ma,峰值为445Ma;新元古代年龄谱段930～735Ma,峰值为849Ma;中元古代年龄谱段1760～1033Ma;新太古代—古元古代年龄谱段3095～2478Ma。综合研究认为,舒家坝群的物源具多元性,包括西秦岭北缘构造带、北祁连造山带东段和华北板块基底,其中北祁连造山带东段和西秦岭北缘构造带是舒家坝群沉积的主要物源区,且后者占主导地位。结合区域地质资料,根据其物源组成特征判断,舒家坝群形成于陆—陆或弧—陆碰撞后由挤压转换为伸展环境的局部裂陷盆地。 相似文献
5.
《Comptes Rendus Geoscience》2018,350(6):255-266
The Oued Togba and Sebkha Gezmayet units of the Adrar Souttouf Massif in the southern Moroccan Sahara are thought to represent tectonic fragments that may have an affinity to the Avalonian and Meguma terranes of eastern North America. Here we study siliciclastic rocks of the Sebkha Gezmayet unit with respect to their detrital zircon spectra. Beside the commonly used U–Th–Pb ages, several aspects of zircon morphology (length, width, roundness, surficial indicators of sedimentary transport, morphotype) are described. The detrital zircon age spectrum of the Sebkha Gezmayet unit resembles that of the already dated underlying igneous rocks. Occurrences of Early Devonian zircon ages are at odds with the magmatic history of the West African Craton but are common in the Avalonian and Meguma terranes, which were affected by the Appalachian orogenies. The scarcity of Mesoproterozoic detrital zircon grains corroborates the previously suggested Meguma terrane affinity of this part of the Adrar Souttouf Massif. Combining zircon morphology and isotopic data, we propose first assumptions on the sedimentary environments of the Sebkha Gezmayet unit during different periods of the Palaeozoic. 相似文献
6.
朝鲜半岛及华北上元古界-古生界沉积序列与碎屑锆石年代学记录及其构造属性分析 总被引：2，自引：2，他引：0
通过地层结构、沉积序列与碎屑锆石年代学记录等三方面的成因分析和区域对比,本文进一步探究了中-朝地块新元古代-古生代的构造属性及演化信息。研究指出,朝鲜半岛平南盆地、太白山盆地以及华北地块内部,其地层结构-沉积相序主要以寒武-奥陶系内陆架碳酸盐岩沉积、志留-泥盆系缺失、中上石炭统-二叠系海陆交互相含煤沉积为特征,并具有可对比的1.85Ga、2.5Ga以及1.15Ga、1.6Ga等碎屑锆石年龄峰值。而在临津江带、沃川带以及华北东南缘,则以泥盆-石炭系泥岩/片岩、中基性火山岩及火山碎屑岩、碳酸盐岩(透镜体)混杂发育为特征,总体显示外陆架沉积环境,且具有可对比的与地层时代接近的最小碎屑锆石年龄,这也是对沉积期较强构造-岩浆活动的反映。综合地层结构、相序、碎屑锆石年龄组成以及聚煤记录,提出朝鲜半岛与华北应属于统一的一级构造单元,即"中-朝板块";但朝鲜半岛西南部及华北东南缘毗邻板块边缘,因此其地层-沉积记录与板内存在差异,简单的一致性模式并不适用。 相似文献
7.
《International Geology Review》2012,54(18):2291-2312
ABSTRACTAs 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. 相似文献
8.
华北克拉通北缘化德群中碎屑锆石的LA-ICP-MS U-Pb年龄及其构造意义 总被引：20，自引：14，他引：6
化德群出露地区位于华北克拉通北缘中部,紧邻中亚造山带南缘,呈近东西向展布。在它的西边是早-中元古代的白云鄂博裂谷和渣尔泰—狼山裂谷,东南面是由长城系、蓟县系和青白口系组成的早-新元古代的燕辽裂陷槽,南边分布着1.9~1.8Ga麻粒岩相变质的丰镇群（孔兹岩系）,北边出露有代表中亚造山带的古生代岩石。化德群由一套浅变质和未变质的沉积岩组成,无火山岩夹层。地层序列包含多个沉积旋回,每个旋回自下而上为含砾砂岩、砂岩、碳酸盐岩和泥质岩。岩石组合反映了从河流—滨海—浅海相的沉积环境。化德群的地层序列可以和白云鄂博群及渣尔泰群相对比。本文对化德群四个变质砂岩样品中的碎屑锆石进行了LA-ICP-MS U-Pb年龄测定,年龄主要集中在1800±50Ma和1850±50Ma,另外还有~2500Ma和~2000Ma的次要峰值。化德群底部变质含砾云母长石石英砂岩中碎屑锆石的最小谐和年龄是1758±7Ma,限定了化德群沉积时代的下限。碎屑锆石的CL图像显示,1800±50Ma和1850±50Ma的锆石主要是变质成因,少量岩浆成因,说明化德群的源区主要是古元古代的变质岩,少量岩浆岩。~2500Ma和~2000Ma的碎屑锆石代表了更为古老的源区。碎屑锆石的U-Pb年龄限制了化德群的沉积时代为古元古代晚期—中元古代,年龄峰值对应华北克拉通的重要构造热事件,而无与中亚造山带地质事件相关的年龄信息。沉积组合特征表明化德群属于稳定的浅水—半深水沉积盆地。化德盆地、渣尔泰—狼山盆地和白云鄂博盆地共同构成华北克拉通北缘的被动陆缘裂谷系,该裂谷系的形成可能与燕辽及熊耳裂陷槽的打开是同时期的。因此,华北克拉通的北界应该置于化德群出露区域以北。基于锆石特征的详细分析及对比,我们认为化德群以南的孔兹岩系可能是化德群的主要源区。 相似文献
9.
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。 相似文献
10.
哀牢山古特提斯洋的打开时限及其缝合带的具体位置对理解哀牢山古特提斯洋构造演化具有非常重要的意义。本文采用碎屑锆石年代学方法,分析了哀牢山构造带及其两侧不同时期沉积物源的特征及其变化,解译了其物源差别所指示的哀牢山古特提斯洋盆打开时限以及缝合带的构造位置。碎屑锆石年代学显示,哀牢山构造带两侧上志留统碎屑锆石都记录一个~450 Ma的最年轻的峰值和一个格林威尔期造山事件的年龄群(1100~800 Ma),以及一个2600~2400 Ma的次峰;不同于上志留统,构造带东侧下泥盆统碎屑锆石并未出现年轻的~450 Ma峰值年龄信息,西侧U-Pb年龄分布模式与上志留统一致,记录~450 Ma峰值年龄信息,而且构造带两侧下泥盆统碎屑锆石的2600~2400 Ma的峰值明显要强于上志留统。区域上发表的碎屑锆石年代学资料,也揭示相同的年龄峰值。因此,综合区域上的其他地质资料,我们认为哀牢山古特提斯洋盆的打开时限应该在晚志留世-早泥盆世,哀牢山断裂带代表了哀牢山洋盆闭合的位置。 相似文献
11.
北山地区红柳园组沉积时代、沉积环境及源区构造背景分析 总被引：1，自引：0，他引：1
北山地区位于华北板块、塔里木板块和哈萨克斯坦板块交汇带,晚古生代构造演化倍受关注且久有争议,该地区晚古生代地层的研究对探讨大地构造演化具有重要意义。利用同位素定年、沉积相分析、粒度分析和碎屑成分统计分析方法对北山地区早石炭世红柳园组进行研究。在下部火山岩中获得LA-ICP-MS锆石U-Pb年龄为359.9±1.4 Ma,参考区域古生物资料,其形成时代应为早石炭世早期。红柳园组上部碎屑岩中发育大量浊流沉积构造和典型鲍马序列,其中砂岩成熟度较低,并且粒度分析结果显示具有浊流沉积的粒度特征,这些证据共同指示红柳园组为近物源浊流沉积。此外通过碎屑组分统计和Qt-F-L、Qm-F-Lt以及Qp-Lv-Ls图解对沉积构造背景进行了探讨,发现研究区红柳园组物源主要来自火山弧,表明其形成的构造环境应为与岛弧邻近的沉积盆地。 相似文献
12.
The Mongol–Okhotsk Belt, a major structural element of East Asia, is probably the youngest orogenic segment within the Central Asian Orogenic Belt. However, the timing of final closure of the Mongol–Okhotsk Ocean remains unresolved. Here, we present detrital zircon U–Pb–Hf isotopic data and whole-rock geochemical data (major and trace elements and Sm-Nd isotopes) for the metasedimentary rocks from the Un'ya–Bom Terrane, Dzhagdy Terrane, and the eastern part of the Tukuringra Terrane. Our new zircon U-Pb ages suggest that all sedimentary formations along the Dzhagdy Transect are early Mesozoic in age, rather than Paleozoic as previously thought. The detrital zircons from the metasedimentary rocks in the Un'ya–Bom Terrane, the Dzhagdy Terrane, and the eastern part of the Tukuringra Terrane yielded the youngest concordant ages of 194 ± 4, 193 ± 2, and 171 ± 2 Ma, respectively. Moreover, we note that the so-called sedimentary formations of these terranes are not single sedimentary sequences as previously suggested, but a set of an olistostrome or tectonic mélanges composed of rocks of different ages and origins. These sedimentary formations are probably relics of the Mongol–Okhotsk remnant basin that formed in the “gaps” between the southern margin of the North Asian Craton and the Amur Block during their collision. The absence of detrital zircons younger than 171 Ma in the sedimentary rocks of the Mongol–Okhotsk basin implies that the final closure of this basin could have taken place at the boundary of the Early and Middle Jurassic as a result of the collision or the development of the Mongol–Okhotsk orogenic belt in this region. After that, the Mongol–Okhotsk Belt underwent intense deformation related to within-plate strike-slip faulting, which could be attributed to the late Mesozoic rotation of the North Asian Craton relative to the continental massifs of East Asia. 相似文献
13.
从前人的研究来看,十里墩组缺少限定其形成时代的标准化石,这导致其沉积时限尚有诸多争议,并且对于该套地层物源的相关研究甚少.以西秦岭临潭地区十里墩组上段碎屑岩为研究对象,进行LA-ICP-MS锆石U-Pb年代学研究,探讨其形成时代及物源.结果表明:十里墩组上部层位的2个样品中最小锆石年龄组加权平均年龄为265.7±6.5 Ma,即十里墩组上段沉积时代应不老于265.7±6.5 Ma,综合古生物化石信息将其形成年代厘定为中晚二叠世.所获得碎屑锆石年龄可划分为4组:①显生宙年龄组,265~467 Ma;②新元古代年龄组,564~996 Ma,该组有小段峰值,峰值年龄为955 Ma;③中元古代年龄组,1 099~1 539 Ma;④古元古代-太古代年龄组,1 622~3 153 Ma,该组年龄又可细分为古元古代中晚期年龄段:1 622~2 194 Ma,峰值为1 902 Ma;古元古代早期-太古代年龄段:2 343~3 153 Ma,峰值为2 516 Ma.综合研究认为,十里墩组上段的物源具多元性,包括华北板块南缘、祁连造山带东段以及西秦岭北缘构造带,且华北板块南缘古老基底为其主要物源.据沉积相、岩相古地理以及区域构造演化分析认为,十里墩组上段沉积于扬子板块俯冲伴随勉略洋收敛所形成的弧后盆地北缘斜坡地带. 相似文献
14.
内蒙古苏尼特左旗地区位于兴蒙造山带中段,是研究古生代俯冲-增生造山作用和地壳生长的关键地区。在苏尼特左旗南部,晚泥盆-早石炭世色日巴彦敖包组角度不整合在早古生代增生楔之上,已有研究对于其沉积环境、盆地属性及区域构造意义一直存在较大分歧。本文对色日巴彦敖包组敖木根呼都格剖面和阿拉塔特剖面碎屑岩和火山岩夹层开展锆石UPb测年及Hf同位素分析,并进行了沉积相分析进一步查明了地层层序、时代及物源特征,并对沉积环境和盆地属性进行了探讨。研究表明,敖木根呼都格剖面色日巴彦敖包组底部含砾粗砂岩最小谐和碎屑锆石年龄为391±5Ma,中下部凝灰质砂岩最小谐和碎屑锆石年龄为338.2±4.3Ma,凝灰岩锆石年龄为336±2Ma、333±3.5Ma,结合古生物化石,表明底部形成于晚泥盆世,中上部地层形成于早石炭世晚期。阿拉塔特剖面中上部安山质火山碎屑岩最小谐和碎屑锆石年龄加权平均值为320.4±6.2Ma,表明其形成于晚石炭世。碎屑锆石年龄谱及Hf同位素组成表明底部及中部砂岩碎屑物主要来自近源的早古生代白音宝力道和二连东乌旗地区弧岩浆岩,少量来自北侧南蒙古弧。结合沉积相分析,推测苏尼特左旗南部色日巴彦敖包组下部为一套形成于弧陆碰撞后被动陆缘滨浅海相沉积建造,中上部为形成于弧前盆地的一套杂砂岩夹火山岩建造。以上资料表明,该区从早石炭世开始转为活动陆缘背景,暗示古亚洲洋中东段在晚古生代仍未封闭。 相似文献
15.
宝音图隆起的构造归属仍然存在争议,有学者认为是兴蒙造山带中的微陆块,也有观点认为是华北克拉通的一部分.作为宝音图隆起的重要组成部分,探究宝音图岩群的形成时代、构造归属是解决这一问题的重要途径.通过对宝音图岩群3件石英岩样品进行锆石U-Pb同位素测试,在一岩组（石英岩和石英片岩岩组）、二岩组（石英岩岩组）、三岩组（片岩岩组）中分别获得较可靠的碎屑锆石最小谐和年龄为1 284 Ma、1 319 Ma、1 395 Ma,代表各岩组的沉积上限.结合侵入宝音图岩群中的变质基性脉岩的锆石U-Pb年龄为895.5±6.8 Ma,将研究区宝音图岩群一-三岩组的沉积时代大致限定在895.5~1 284.0 Ma之间,位于中元古代晚期至新元古代早期;可以和相邻区域大致形成于同一时期的阿拉善地区阿拉善群、白云鄂博地区白云鄂博群上亚群、化德-康保地区化德群上亚群对比.斜长角闪岩地球化学特征反映其形成于大陆边缘裂谷环境,可能为Rodinia超大陆裂解在本区的响应.宝音图岩群与邻区同时代沉积建造的碎屑锆石年龄谱较为相似,其主要峰值反映的地质事件与华北克拉通所经历的主要构造-热事件可以较好对应,说明宝音图岩群的物源来自于华北克拉通,为华北克拉通边缘的沉积.宝音图隆起应当为华北的一部分. 相似文献
16.
Inkisi组是刚果盆地西南缘最古老的沉积地层之一,岩性主要为一套紫红色、红褐色细粒、细中粒长石砂岩、杂砂岩。通过对安哥拉东北部Inkisi组长石砂岩开展碎屑锆石测年、岩石地球化学研究,探讨其沉积时代、物质来源、沉积环境和大地构造背景,为研究刚果盆地演化提供科学依据。结果表明,碎屑锆石206Pb/238U年龄主要集中于3个年龄峰值区间2350~1900 Ma、1150~850 Ma、850~500 Ma,最年轻的锆石峰值年龄为531±9 Ma,据此,笔者等认为Inkisi组的沉积时代上限应厘定为早寒武世。Inkisi组砂岩地球化学特征显示,物源具有长英质物源近源搬运特征,沉积时期的水体为陆相开阔的淡水环境。通过碎屑锆石年龄谱特征、主微量元素物源判别及构造判别图解,本文认为,West Congo构造带为安哥拉东北部地区Inkisi组主要物源区,Lufilian构造带、Angola 地盾等是其次要物质来源,物源区构造环境主要为活动大陆边缘和被动大陆边缘构造环境背景。 相似文献
17.
18.
Inkisi组是刚果盆地西南缘最古老的沉积地层之一,岩性主要为一套紫红色、红褐色细粒、细中粒长石砂岩、杂砂岩。通过对安哥拉东北部Inkisi组长石砂岩开展碎屑锆石测年、岩石地球化学研究,探讨其沉积时代、物质来源、沉积环境和大地构造背景,为研究刚果盆地演化提供科学依据。结果表明,碎屑锆石206Pb/238U年龄主要集中于3个年龄峰值区间2350~1900 Ma、1150~850 Ma、850~500 Ma,最年轻的锆石峰值年龄为531±9 Ma,据此,本文认为Inkisi组的沉积时代上限应厘定为早寒武世。Inkisi组砂岩地球化学特征显示,物源具有长英质物源近源搬运特征,沉积时期的水体为陆相开阔的淡水环境。通过碎屑锆石年龄谱特征、主微量元素物源判别及构造判别图解,本文认为,West Congo构造带为安哥拉东北部地区Inkisi组主要物源区,Lufilian构造带、Angola 地盾等是其次要物质来源,物源区构造环境主要为活动大陆边缘和被动大陆边缘构造环境背景。 相似文献
19.
《地学前缘(英文版)》2020,11(5):1495-1509
The Qinling-Qilian connection zone(QQCZ) is a key area to reveal the relationship and to make a link of the North Qinling and the North Qilian orogens,China.Here we present U-Pb dating data of detrital zircons from four sedimentary/metasedimentary rocks in the QQCZ and the southwestern North China Block(NCB) and detailed regional structural data.Three episodes of fold deformation(D_1,D_2 and D3) are distinguished in the QQCZ,with the former two occurred during the early Paleozoic.The D_1 deformation is mainly characterized by regionally penetrative schistosity and some residual rootless intrafolial folds due to the intensive superpositions by the subsequent D_2 and D3 deformations.The D_2 deformation characterized by tight folds,associated axial plane foliations and crenulation lineations indicates a stress field characterized by NNE-SSW-directed compression,which may be induced by the collision between the NCB and the southern blocks.The D3 deformation which might occur during the Mesozoic is marked by upright open folds and kink bands.The similarity of the detrital zircon age spectra of the Huluhe Group in the North Qilian Orogen and the Erlangping Group in the North Qinling Orogen suggests that the two groups have similar provenance,which may indicate that the North Qilian Orogen corresponded to the North Qinling Orogen in a regional tectonic framework.In addition,the remarkable age peak at～435 Ma of the detrital zircon age spectrum of the Duanjiaxia Formation in the southwestern NCB indicates that this formation obtained the provenance of the North Qilian and North Qinling orogens,which may be generated by the collage of the southwestern NCB and the QQCZ during the Late Ordovician-Early Silurian.Based on structural,detrital zircon and metamorphic data,we suggest that the North Qilian and North Qinling orogens underwent similar evolution during the early Paleozoic due to the closure of the North Qilian and the Kuanping oceans which located at the northern boundary of the Proto-Tethys Ocean. 相似文献
20.
三叠系沉积物广泛覆盖青藏高原东北缘,其中松潘—甘孜地区三叠系的沉积物得到了较系统的研究,但是青藏高原北缘的祁连山三叠系盆地的研究却较为缺乏。为了丰富相关研究和揭示区域构造演化的特点,通过古水流方向统计、砂岩中碎屑矿物统计和碎屑锆石U-Pb测年等方法对祁连山三叠纪盆地物源进行系统研究。结果表明,祁连山三叠系盆地的古流向主要有南东向、正南向、南西向,物源来自岩浆弧和大规模褶皱造山作用的混合区。祁连山三叠系砂岩中的碎屑锆石的年龄谱主要峰值集中在250~290 Ma、360~460 Ma、1 600~2 000 Ma和2 200~2 600 Ma这4个年龄段。通过对比分析华北板块、华南板块中和秦祁昆中央造山带中岩浆锆石年龄谱特征可知:1 600~2 000 Ma和2 200~2 600 Ma年龄段的锆石来自华北板块,360~460 Ma年龄段的锆石来自北祁连造山带,250~290 Ma年龄段的锆石来自东昆仑的火山岛弧。此外,600~1 000 Ma年龄段锆石很少,这些锆石来自扬子板块,表明在三叠纪扬子克拉通和华北克拉通发生碰撞形成了秦岭造山带,阻断了来自扬子克拉通的物源。 相似文献