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1.
塔里木西南缘和田布雅花岗岩锆石SHRIMP U-Pb年龄及地质意义 总被引：1，自引：0，他引：1
塔里木西南缘的和田布雅花岗岩,由巨斑二长花岗岩、似环斑状二长花岗岩和细粒钾长花岗岩3种岩石类型组成,其中具似环斑状结构的花岗岩与国内外报道的环斑花岗岩在基本岩相学方面较为相似,可能属于广义的环斑花岗岩系列.根据暗色包体中含有寄主岩石的钾长石斑晶等分析,布雅花岗岩可能是岩浆混合的产物.布雅花岗岩锆石SHRIMPU-Pb定年获得(459±23)Ma年龄值(MSWD=1.3),形成时代为晚奥陶世,这为该区地质构造演化提供了基本年代约束.通过区域资料对比,铁克里克隆起带和田布雅后造山A型花岗岩与西昆仑造山带南部俯冲型花岗岩侵位时代基本一致,暗示原特提斯洋的闭合是由北向南迁移的,当原特提斯洋南部处于俯冲消减时期,北部铁克里克隆起带南部的活动大陆边缘已进入造山后演化阶段,这对于重建西昆仑造山带的构造演化具有重要意义. 相似文献
2.
对额尔古纳地块新元古代花岗岩进行了锆石LA-ICP-MS U-Pb年代学、岩石地球化学和锆石Hf同位素研究,以便对其新元古代岩浆作用历史与微陆块构造属性给予制约.所测花岗质岩石中锆石的CL图像特征和Th/U比值(0.17~1.46) 显示其为岩浆成因.测年结果并结合前人定年结果,可以判定额尔古纳地块上至少存在~929 Ma、~887 Ma、~850 Ma、~819 Ma、~792 Ma、~764 Ma和~738 Ma岩浆事件.岩石地球化学特征显示,~887 Ma花岗岩为一套后碰撞花岗岩类;而850~737 Ma花岗质岩石整体上属于A-型花岗岩,也有部分岩体(漠河、阿木尔、碧水和室韦岩体)显示I-型花岗岩特征.锆石Hf同位素特征反映这些花岗岩的源区既有中-新元古代(TDM2=884~1 563 Ma)新增生地壳物质的部分熔融,同时伴有少量古老地壳物质的混染,也有残留的古老中基性下地壳物质的部分熔融.综合研究区新元古代侵入岩的地球化学特征,同时对比新元古代全球构造热事件,认为额尔古纳地块上新元古代岩浆活动记录了Rodinia超大陆形成和演化过程中的地壳响应:927~880 Ma的岩浆作用应是Rodinia超大陆汇聚造山的产物;而850~737 Ma的岩浆作用应是对Rodinia超大陆快速裂解的记录.通过岩浆事件对比发现,额尔古纳地块与邻近的西伯利亚南缘微陆块(如中蒙古地块和图瓦地块)具有亲缘性,而与塔里木板块和华南板块至少在新元古代岩浆活动上具有一定的相似性,而明显区别于华北板块和西伯利亚板块. 相似文献
3.
报道了塔里木库鲁克塔格地区新元古代晚期花岗闪长岩和钾长花岗岩的锆石U-Pb年龄和Hf同位素组成。花岗闪长岩锆石U-Pb谐和年龄为630.1±1.3Ma,钾长花岗岩锆石U-Pb谐和年龄为630.6±1.3Ma。Hf同位素组成表明,这2种岩石主要来自古老(中)基性地壳的重熔,可能有部分地幔物质的加入。结合已有的研究表明,650~615Ma期间的岩浆活动代表了塔里木地块新元古代最晚期的岩浆活动,是Rodinia超大陆解体过程中的产物,与泛非造山事件无关。塔里木地块自新元古代中期到早寒武世,持续接受了被动大陆边缘沉积,表明在这一时期塔里木为冈瓦那大陆之外独立的大陆块体,或是位于冈瓦那大陆最边缘的稳定大陆块体。 相似文献
4.
祁连山在构造上是一条经历了多期构造旋回叠加的早古生代复合型造山带,花岗质岩浆作用研究对揭示其构造演化具有重要意义。锆石U-Pb年代学统计结果表明,祁连地区花岗质岩浆活动可以分为7个大的阶段,包括古元古代早期(2 470~2 348 Ma)、古元古代晚期(1 778~1 763 Ma)、中元古代晚期-新元古代早期(1 192~888 Ma)、新元古代中期(853~736 Ma)、中寒武世-志留纪(516~419 Ma),泥盆纪-早石炭世(418~350 Ma)以及中二叠世-晚三叠世(271~211 Ma)。其中古元古代早期发育强过铝质高钾钙碱性S型和准铝质低钾拉斑-高钾钙碱性I型花岗岩,记录了早期的陆壳增生及改造事件。古元古代晚期为准铝质-弱过铝质高钾钙碱性-钾玄质A型花岗岩,是Columbia超大陆裂解事件的产物。中元古代晚期-新元古代早期以过铝质-强过铝质钙碱性-钾玄质S型花岗岩为主,新元古代中期以准铝质-强过铝质钙碱性-高钾钙碱性A型花岗岩为主,分别对应Rodinia超大陆的汇聚和裂解事件。中寒武世-志留纪花岗岩是洋陆转换过程中的产物,约440 Ma加厚基性下地壳部分熔融形成的低Mg埃达克岩的广泛出现指示祁连地区全面进入碰撞造山阶段。泥盆纪-早石炭世花岗岩代表后碰撞伸展阶段岩浆岩组合,发育准铝质-强过铝质低钾拉斑-钾玄质等一系列花岗岩。中二叠世-晚三叠世花岗岩以准铝质-弱过铝质钙碱性-高钾钙碱性I型花岗岩为主,有少量弱过铝质高钾钙碱性A型花岗岩,是宗务隆洋俯冲消减以及碰撞后伸展过程的产物。 相似文献
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本文通过对西昆仑西段地区晚古生代—中生代花岗岩的岩石类型、形成时代和岩石地球化学资料的综合分析,探讨花岗质岩浆活动期次、岩石成因,结合区域资料,探讨构造-岩浆演化特征和碰撞造山过程。将该地区晚古生代—中生代构造-岩浆演化分为7个阶段:(1)388~324 Ma(特提斯Ⅰ、Ⅱ支洋向北俯冲消减阶段),具富钠贫钾特征的低温TTG岩石组合,形成于陆缘弧环境;(2)339~291 Ma(奥依塔格弧后盆地演化阶段),由于南部特提斯Ⅰ支洋持续往北俯冲,导致西昆仑北缘发生弧后扩展而形成弧后盆地,形成拉斑质具强烈富钠贫钾特征的低温大洋花岗岩;(3)258~241 Ma(特提斯Ⅰ支洋闭合、碰撞造山阶段),岩石中发育石榴子石和白云母,普遍具片麻状构造,属于S型花岗岩,陆壳部分熔融的产物;(4)234~210 Ma(特提斯Ⅰ后碰撞伸展阶段):岩体规模较大,为I型→A型花岗岩,伴随着地幔岩浆底侵和强烈的壳幔岩浆混合作用;(5)198~150 Ma(特提斯Ⅱ支洋向南俯冲消减阶段):类似TTG的岩石组合,形成于与洋壳俯冲有关的岩浆弧环境;(6)148~118 Ma(特提斯Ⅱ支洋闭合、碰撞造山阶段):弱片麻状二云二长花岗岩,属C型埃达克岩,为陆-陆碰撞过程中陆壳加厚发生部分熔融的产物;(7)111~75 Ma(特提斯Ⅱ后碰撞伸展阶段):发育规模较大,钾玄质系列,是古老地壳部分熔融的产物。根据各阶段花岗质岩浆活动特征和构造演化过程,初步提出了西昆仑西段晚古生代—中生代大地构造演化模式图。 相似文献
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中亚造山带东部分布有多个具有前寒武纪基底的微陆块（额尔古纳、兴安、松嫩和佳木斯地块）,其上存在大量元古宙地质记录,包括2. 5~2. 4 Ga、1. 8 Ga、1. 5~1. 4 Ga、0. 9~0. 6 Ga岩浆事件和中—新元古代沉积序列,它们是回答微陆块与Columbia和Rodinia超大陆演化联系和地球中年期演化的关键对象。额尔古纳、兴安和松嫩地块发育相似的2. 5~1. 8 Ga基底岩石且其间缺少古老的蛇绿岩,它们可能构成了一个联合陆块,其陆核至少在2. 7 Ga前已经形成,从华北克拉通北部裂解出去并在其周缘演化,2. 5 Ga和1. 8 Ga经历了洋陆俯冲作用,未参与克拉通化过程。1. 87~1. 80 Ga岩浆作用很可能是Columbia超大陆周缘俯冲带作用于古老的微陆块之下的产物;兴安地块西部和白乃庙岛弧带1. 45~1. 32 Ga A型花岗岩—流纹岩组合及其向陆缘Hf同位素持续亏损的趋势与劳伦南部Granite—Rhyolite Province和波罗的克拉通西南Fennoscandia十分相似,可能是Columbia超大陆周缘俯冲后撤伸展的产物,俯冲后撤和陆下地幔上涌共同促进了Columbia超大陆的伸展和裂解。兴安地块西部发育岩石组合、碎屑锆石年龄和Hf同位素变化与格林威尔造山有关的同碰撞和碰撞后沉积序列相似的沉积地层,而且碎屑锆石微量元素和Hf同位素随时代的系统性变化也揭示了1. 10~0. 98 Ga地壳明显加厚,伴有大量古老地壳物质重熔,0. 9~0. 8 Ga地壳持续减薄,以古老地壳再造为主,这与Rodinia超大陆聚合阶段格林威尔造山（1080~980 Ma）及随后的垮塌伸展过程基本吻合。松嫩地块东北部954 Ma正长花岗岩很可能是松嫩与佳木斯地块陆—陆碰撞后阶段沉积岩部分熔融的产物,可能代表了Rodinia超大陆碰撞聚合在中亚造山带东部的响应。超大陆周缘前进式俯冲引发佳木斯地块与松嫩—兴安—额尔古纳联合陆块在954 Ma前碰撞拼贴,同时在外缘的佳木斯地块上产生953~939 Ma中钾—高钾钙碱性基性—中性—酸性岩组合,920~880 Ma在各地块上广泛发育中酸性钙碱性岩浆作用。从850 Ma开始,后撤式俯冲导致大量高温的钙碱性酸性岩、双峰式岩浆岩组合产出于松嫩和额尔古纳地块上,直至777 Ma和697 Ma之前开始不断裂解产生古牡丹江洋和古新林洋,而且790~560 Ma期间在额尔古纳地块西北缘、松嫩地块东缘均发育被动大陆边缘沉积,记录了Rodinia超大陆的聚合、伸展—裂解过程。另外,中亚造山带东部乃至全球其他块体上大量1. 5~1. 3 Ga和1. 0~0. 7 Ga与超大陆聚合、伸展—裂解有关的“低谷期”地质记录被不断发掘出来,暗示了地球中年期并不是前人认为的构造宁静期。 相似文献
7.
新疆西昆仑早古生代侵入岩地球化学特征及地质意义 总被引：2，自引：0，他引：2
南华纪-早古生代是昆仑山地区洋-陆转换阶段,区域上沿柯岗-库地-其曼于特-带扩张形成古昆仑洋盆。大规模的俯冲消减发生在奥陶纪（481～440Ma,俯冲型侵入岩发育）,志留纪的造山作用结束了洋的演化历程。通过对西昆仑阿喀孜一带侵入岩岩石地球化学特征、LA—ICP—MS锆石U—Pb定年的研究,重塑了本区构造演化过程,将该区早古生代侵入岩细分为晚寒武世壳幔混源序列、晚奥陶世壳幔混源序列和晚志留世壳幔混源序列,从晚寒武世～晚志留世侵入岩显示以下特征：岩石铝饱和指数（A／CNK）值介于（O．86～1．23）,具有由偏基性向偏酸性演化趋势;球粒标准化REE配分曲线成近平行曲线簇,稀土总量∑REE（228．96—379．39）显著增高,而OEu（0．79→0．16）降低,表明岩浆分异增大,Eu负异常明显加深,地壳成熟度提高;微量元素显示出富集大离子亲石元素（LILE）,亏损高场强元素（HFSE）。结合侵人岩形成的大地构造环境,该期早古生代侵入岩形成于西昆仑地块北缘古昆仑洋盆的俯冲-消减-闭合,塔里木陆块与西昆仑地块陆一陆碰撞造山阶段,为研究该区古昆仑洋消减一消亡构造演化提供了最新的地质资料。 相似文献
8.
新疆塔里木南缘铁克里克地区西段出露的古元古代都维吐卫花岗岩体中大量发育辉绿岩脉, 多呈岩墙、 岩株状产出。岩石地球化学研究表明, 辉绿岩来自EMI型地幔源区, 形成于大陆板内裂解环境。辉绿岩的LA-ICP-MS 锆石U-Pb同位素年龄为408.5±7.3Ma, 属于早泥盆世。结合西昆仑造山带中一系列早古生代花岗质岩体, 推测该辉绿岩的形成表明原特提斯洋的闭合时间应早于早泥盆世, 代表了原特提斯洋构造旋回的结束, 为探讨早古生代塔里木南缘的构造演化提供了新的资料。 相似文献
9.
北阿尔金地区古元古代ca.2.0Ga岩浆-变质事件 总被引：4，自引：3，他引：1
中国有三个主要的克拉通,分别是华北、华南和塔里木,它们在显生宙经造山过程聚集到一起。塔里木克拉通位于中国的西北部,面积超过60万平方千米,其北侧为中亚造山带,南侧为西昆仑造山带和阿尔金造山带。塔里木克拉通的前寒武纪岩石主要出露在其南北两侧边缘,包括库鲁克塔格、敦煌、阿尔金、铁克里克和阿克苏地块,它们记录了塔里木克拉通早期的构造演化。北阿尔金地块的阿克塔什塔格地区位于塔里木克拉通的东南边缘。该地区最老的岩石被称为米兰群或阿克塔什塔格杂岩。主要岩石包括太古宙的TTG岩石和表壳岩,以及古元古代的片麻状花岗岩,另有少量变质基性岩呈包体状出露在强变形的长英质侵入体中。本文对该区闪长质片麻岩开展了锆石SHRIMP U-Pb定年,同时还对变质基性岩进行了锆石LA-ICP-MS U-Pb测年和地球化学分析,目的是要约束北阿尔金地区古元古代的岩浆-变质事件。闪长质片麻岩的结晶年龄为2.04～2.03Ga,它们形成于岛弧环境。地球化学分析表明,变质基性岩的原岩是拉斑玄武岩。它们有类似于E-MORB的平坦的稀土配分模式,Nb、Ta、Zr、Hf不亏损,说明它们形成于大洋板内环境。在变质基性岩中还识别出两期变质锆石,其中2.05～2.01Ga的早期锆石代表了麻粒岩相的变质作用,而1.98～1.96Ga的晚期锆石可能与角闪岩相的退变质作用有关。无论该区岩浆作用还是变质作用都与约2.0Ga发生的俯冲增生造山事件有关。 相似文献
10.
位于塔里木地块西南缘、西昆仑造山带北缘的帕什托克侵入序列由石英闪长岩-石英二长闪长岩组成,类似TTG组合,形成于中元古代晚期。本文从帕什托克侵入序列的地球化学分析出发,通过对该侵入序列两期侵入岩的主量元素和微量元素的研究,讨论了该侵入序列的成因、构造环境和与其相关的板块间地球动力学模式,认为该侵入序列为I型准铝质高钾钙碱性花岗闪长岩系列,属活动板块边缘碰撞前大陆弧花岗岩类,两期侵入岩为同源岩浆演化,母岩浆属壳幔混合源,且岩浆向酸性演化。根据岩浆演化的物理环境和构造环境,推测早古生代库地洋的完全闭合与库地洋壳向塔里木古陆块俯冲消减有关,是塔里木古陆块和柴达木古陆块在Rodinia超级大陆汇聚过程中的产物。 相似文献
11.
The West Kunlun orogenic belt(WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto-and Paleo-Tethys oceans. Previous investigations have focused on the igneous rocks and ophiolites distributed mostly along the Xinjiang-Tibet road and the China-Pakistan road, and have constructed a preliminary tectonic model for this orogenic belt. However, few studies have focused on the so-called Precambrian basement in this area. As a result, the tectonic affinity of the individual terranes of the WKOB and their detailed evolution process are uncertain. Here we report new field observations, zircon and monazite U-Pb ages of the "Precambrian basement" of the South Kunlun terrane(SKT) and the Tianshuihai terrane(TSHT), two major terranes in the WKOB. Based on new zircon U-Pb age data, the amphibolite-facies metamorphosed volcanosedimentary sequence within SKT was deposited during the late Neoproterozoic to Cambrian(600-500 Ma), and the flysch-affinity Tianshuihai Group, as the basement of the TSHT, was deposited during the late Neoproterozoic rather than Mesoproterozoic. The rock association of the volcano-sedimentary sequence within SKT suggests a large early Paleozoic accretionary wedge formed by the long-term lowangle southward subduction of the Proto-Tethys Ocean between Tarim and TSHT. The amphibolitefacies metamorphism in SKT occurred at ca. 440 Ma. This ca. 440 Ma metamorphism is genetically related to the closure of the Proto-Tethys Ocean between Tarim and the Tianshuihai terrane, which led to the assembly of Tarim to Eastern Gondwana and the final formation of the Gondwana. Since the late Paleozoic to early Mesozoic, the northward subduction of the Paleo-Tethys Ocean along the HongshihuQiaoertianshan belt produced the voluminous early Mesozoic arc-signature granites along the southern part of NKT-TSHT. The Paleo-Tethys ocean between TSHT and Karakorum closed at ca. 200 Ma, as demonstrated by the monazite age of the paragneiss in the Kangxiwa Group. Our study does not favor the existence of a Precambrian basement in SKT. 相似文献
12.
GRANITOIDS AND TETONIC EVOLUTION OF THE WEST KUNLUN OROGENIC BELT 相似文献
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Owing to the lack of early Neoproterozoic geological and geochronological data, most Rodinia supercontinent reconstruction models do not include the Amuria Block in the Central Asian Orogenic Belt (CAOB), and the Amuria Block was varying attributed to the North China, Siberian or Tarim tectonic affinities. In this study, we identified one early Neoproterozoic granitic pluton (964–947 Ma) and one early Neoproterozoic sedimentary unit (<906 Ma) in the Erguna Terrane. The samples (964–947 Ma) are I-type granitoids, and show high zircon in-situ εHf(t) (−2.1–10.0) and whole-rock εHf(t) (1.4–4.8) and high εNd(t) (−2.3 to −0.8). These granitoids are characterized by high Zr saturation temperature (TZr) (701–835 °C) and no inherited zircons, suggesting high-degree of partial melting of their source rocks. The granites were likely formed by biotite-/muscovite dehydration melting of subalkaline mafic lower crust in a continental arc setting. Detrital zircons of the sandstone sample define an age peak at 923–906 Ma. Early Neoproterozoic age data compilation from the four Amuria microcontinents (i.e., Erguna, Xing'an, Songnen and Jiamusi terranes) in NE China indicate the presence of two major magmatic flare-ups at 964–880 Ma and 850–740 Ma. Considering that early Neoproterozoic magmatic rocks are absent in the Siberian and North China cratons but widespread in the Tarim Craton, we suggested that the Erguna Terrane was part of the Tarim Craton in the Early Neoproterozoic. The Erguna Terrane may have undergone a two-staged Neoproterozoic tectonic evolutionary history: (1) early Neoproterozoic arc accretion in response to the Rodinia assembly, and (2) middle Neoproterozoic break-away from the SW Tarim Craton associated with the Rodinia breakup. 相似文献
15.
Hong-Fei Zhang Li Zhang Nigel Harris Lan-Lan Jin Honglin Yuan 《Contributions to Mineralogy and Petrology》2006,152(1):75-88
The Songpan-Garze fold belt, located in the eastern part of the Tibetan Plateau, covers a huge triangular area bounded by the Yangtze (South China), the North China and the Tibetan Plateau blocks. In the northeastern part of the Songpan-Garze fold belt, the Yanggon and Maoergai granitoids provide insights into regional tectono-magmatic events, basement nature and tectonic evolution. U–Pb zircon SHRIMP dating shows that the Yanggon and Maoergai granitoids have magmatic crystallization ages of 221 ± 3.8 Ma and 216 ± 5.7 Ma, respectively. Both the granitoids display adakitic geochemical signatures, suggesting that their magma was derived from partial melting of thickened lower crust. Pb–Sr–Nd isotopic compositions for granitoids reveal that there is an unexposed Proterozoic basement in the Songpan-Garze belt, which has an affinity with the Yangtze block. During development of the Paleo-Tethys ocean, the basement of the Songpan-Garze belt would be a peninsula approaching the Paleo-Tethys ocean from the Yangtze block. 相似文献
16.
Sulawesi has generally been interpreted as the product of convergence in the Cretaceous and Cenozoic, and high mountains in west Central Sulawesi have been considered the product of magmatism and metamorphism related to Neogene collision. New SHRIMP and LA-ICP-MS U-Pb zircon dating of metamorphic and granitoid rocks has identified protoliths and sources of melts, and indicates an important role for extension. Schists, gneisses and granitoids have inherited Proterozoic, Paleozoic, Mesozoic and Paleogene zircons. Mesoproterozoic and Triassic age populations are similar to those from the Bird’s Head region. Their protoliths included sediments and granitoids interpreted as part of an Australian-origin block. We suggest this rifted from the Australian margin of Gondwana in the Jurassic and accreted to Sundaland to form NW Sulawesi in the Late Cretaceous. Some metamorphic rocks have Cretaceous and/or Late Eocene magmatic zircons indicating metamorphism cannot be older than Late Eocene, and were not Australian-origin basement. Instead, they were metamorphosed in the Neogene after Sula Spur collision and subsequent major extension. Associated magmatism in west Central Sulawesi produced a K-rich shoshonitic (HK) suite in the Middle Miocene to Early Pliocene. A later episode of magmatism in the Late Miocene to Pliocene formed mainly shoshonitic to high-K calc-alkaline (CAK) rocks. I-type and silica-rich I-type granitoids and diorites of the CAK suite record a widespread short interval of magmatism between 8.5 and 4 Ma. Inherited zircon ages indicate the I-type CAK rocks were the product of partial melting of the HK suite. S-type CAK magmatism between c. 5 and 2.5 Ma and zircon rim ages from gneisses record contemporaneous metamorphism that accompanied extension. Despite its position in a convergent setting in Indonesia, NW Sulawesi illustrates the importance of melting and metamorphism in an extensional setting during the early stages of mountain building. 相似文献
17.
青藏高原西部甜水海地区白垩纪花岗岩类的岩石学地球化学特征及其地质意义 总被引：2，自引：0，他引：2
甜水海地区广泛分布白垩纪的中酸性侵入岩,可分为早白垩世（123Ma）、晚白垩世早期（100~93Ma）和晚白垩世晚期（79~74Ma）3期。早期侵入体零星,为正长花岗岩、二云母花岗岩及含石榴子石花岗岩,属高钾钙碱性系列,A/CNK大于1.1,K2O含量大于Na2O,负Eu异常明显,刚玉分子数大于1.1,属于典型的强过铝质S型花岗岩。晚白垩世早期花岗岩分布广泛,以英云闪长岩和花岗闪长岩为主,主要属中—高钾钙碱性系列,个别属于钾玄岩系列,A/CNK主体小于1.15,负Eu异常中等,刚玉分子数多小于1.1,主体属I型花岗岩。晚白垩世晚期花岗岩同样分布广泛,为花岗闪长岩、二长花岗岩组合,主要属于高钾钙碱性系列,个别为中钾钙碱性系列,A/CNK主体大于1.05,负Eu异常较明显,刚玉分子数多大于1.1,主体属于典型的S型花岗岩。综合分析认为,甜水海地区白垩纪中酸性侵入岩与班公湖-怒江残余洋盆消减、闭合有关,可能记录了羌塘-冈底斯带之间的同碰撞（早期）、碰撞后（晚白垩世）等构造岩浆演化过程。 相似文献