How many sutures in the southern Central Asian Orogenic Belt：Insights from East Xinjiang-West Gansu（NW China）？   总被引：1，自引：0，他引：1  

Wenjiao Xiao  ;Chunming Han  ;Wei Liul  ;Bo Wan  ;Ji'en Zhang  ;Song  jian Ao  ;Zhiyong Zhang  ;Dongfang Song  ;Zhonghua Tian  ;Jun Luo 《地学前缘(英文版)》2014,5(4):525-536

How ophiolitic mèlanges can be defined as sutures is controversial with regard to accretionary orogenesis and continental growth.The Chinese Altay,East junggar,Tianshan,and Beishan belts of the southern Central Asian Orogenic Belt（CAOB） in Northwest China,offer a special natural laboratory to resolve this puzzle.In the Chinese Altay,the Erqis unit consists of ophiolitic melanges and coherent assemblages,forming a Paleozoic accretionary complex.At least two ophiolitic melanges（Armantai,and Kelameili） in East Junggar,characterized by imbricated ophiolitic melanges,Nb-enriched basalts,adakitic rocks and volcanic rocks,belong to a Devonian-Carboniferous intra-oceanic island arc with some Paleozoic ophiolites,superimposed by Permian arc volcanism.In the Tianshan,ophiolitic melanges like Kanggurtag,North Tianshan,and South Tianshan occur as part of some Paleozoic accretionary complexes related to amalgamation of arc terranes.In the Beishan there are also several ophiolitic melanges,including the Hongshishan,Xingxingxia-Shibangjing,Hongliuhe-Xichangjing,and Liuyuan ophiolitic units.Most ophiolitic melanges in the study area are characterized by ultramafic,mafic and other components,which are juxtaposed,or even emplaced as lenses and knockers in a matrix of some coherent units.The tectonic settings of various components are different,and some adjacent units in the same melange show contrasting different tectonic settings.The formation ages of these various components are in a wide spectrum,varying from Neoproterozoic to Permian.Therefore we cannot assume that these ophiolitic melanges always form in linear sutures as a result of the closure of specific oceans.Often the ophiolitic components formed either as the substrate of intra-oceanic arcs,or were accreted as lenses or knockers in subduction-accretion complexes.Using published age and paleogeographic constraints,we propose the presence of （1） a major early Paleozoic tectonic boundary that separates the Chinese Altay-East Junggar multiple subduction system  相似文献   

藏北商旭造山型金矿床的发现及意义   总被引：4，自引：3，他引：1  

黄瀚霄  李光明  刘波  张智林  马东  曲扎  肖万峰  刘洪 《矿床地质》2014,33(3):486-496

西藏双湖县商旭金矿床位于班公湖-怒江缝合带中段。矿体赋存于中-下侏罗统木嘎岗日群浅变质复理石中,受北西西向断裂构造控制,呈透镜体状、脉状,或者似层状产出;矿石矿物以自然金为主,矿石类型为石英脉型和蚀变岩型,围岩蚀变特征明显。该矿床主要受地层及构造因素控制,矿区的构造、围岩蚀变、矿物、地球化学异常等可作为找矿标志。野外地质调查和矿床对比研究显示,商旭金矿床在矿物共生组合、蚀变类型、构造类型等方面,与典型的造山型金矿床相似,其成因类型属于造山型金矿床。商旭金矿床的发现为班公湖-怒江成矿带金等贵金属矿产的地质找矿工作开辟了新的方向。  相似文献   

雅鲁藏布江蛇绿岩带西段达机翁地幔橄榄岩组成特征及其形成环境分析   总被引：6，自引：5，他引：1  

连东洋  杨经绥  熊发挥  刘飞  王云鹏  周文达  赵一珏 《岩石学报》2014,30(8):2164-2184

雅鲁藏布江蛇绿岩带自萨嘎以西分成南北两个亚带。对两个亚带蛇绿岩的各自特征及成因联系的研究,是探讨雅鲁藏布江西段的新特提斯洋构造演化的关键。北亚带蛇绿岩呈构造岩块产于冈底斯山前喀喇昆仑断裂带的南侧。其中,位于北亚带西北段的达机翁蛇绿岩,主要由地幔橄榄岩,玄武岩夹硅质岩组成,各单元间断层接触。对达机翁蛇绿岩的地幔橄榄岩开展的组成特征研究表明:(1)地幔橄榄岩主体为方辉橄榄岩,含少量的纯橄岩。方辉橄榄岩内产有豆荚状铬铁矿(呈豆状,块状以及浸染状),铬铁矿有一层纯橄岩的外壳;(2)达机翁方辉橄榄岩单斜辉石含量低,组成矿物以及全岩的地球化学特征均指示了这些样品经历了相对高的部分熔融作用;(3)方辉橄榄岩具有U型的球粒陨石标准化的稀土元素分配模式,Nb相对亏损,Ta,Zr和Hf具有弱的正异常,同时Sr和U具有强烈的正异常,这些特征可能与残余地幔和俯冲带熔/流体之间相互作用导致的轻稀土元素和部分微量元素的选择性富集有关。定量计算表明,达机翁地幔岩中的方辉橄榄岩来源于一个尖晶石相地幔源区的部分熔融,部分熔融程度大于25%,高于深海地幔橄榄岩的部分熔融程度(10%~22%)。这些橄榄岩形成时的氧逸度条件位于FMQ和FMQ+1之间,高于深海地幔橄榄岩(FMQ-1),与俯冲带环境的氧逸度条件一致。因此,我们认为达机翁蛇绿岩中的地幔橄榄岩形成于大洋中脊的环境,随后发生了洋内俯冲作用,位于俯冲带上部的地幔橄榄岩经历了俯冲带流/熔体的交代作用。  相似文献   

Early Permian–Late Triassic Magmatism in the Tuotuohe Region of the Qinghai–Tibet Plateau: Constraints on the Tectonic evolution of the Western Segment of the Jinshajiang Suture   总被引：1，自引：0，他引：1  

QIAN Ye  SUN Fengyue  LI Bile  LI Shijin  ZHAO Junwei 《《地质学报》英文版》2014,88(2):498-516

In this paper we present new zircon U–Pb ages, whole-rock major and trace element analyses, and zircon Hf isotopic data for magmatic rocks in the Tuotuohe region of the western segment of the Jinshajiang suture. Our aim is to constrain the Early Permian–Late Triassic tectonic evolution of the region. Zircons from the magmatic rocks of the Tuotuohe region are euhedral–subhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios(0.4–4.6), indicating a magmatic origin. The zircon U–Pb ages obtained using LA–ICP–MS are 281 ± 1 Ma, 258 ± 1 Ma, 244 ± 1 Ma, and 216 ± 1 Ma, which indicate magmatism in the Early Permian–Late Triassic. A diorite from Bashihubei(BSHN) has SiO2 = 57.18–59.97 wt%, Al2O3 = 15.70–16.53 wt%, and total alkalis(Na2O + K2O) = 4.46–6.34 wt%, typical of calc-alkaline and metaluminous series. A gabbro from Bashibadaoban(BSBDB) belongs to the alkaline series, and is poor in SiO2(45.46–54.03 wt%) but rich in Al2O3(16.19–17.39 wt%) and total alkalis(Na2O + K2O = 5.48–6.26 wt%). The BSHN diorite and the BSBDB gabbro both display an enrichment of LREEs and LILEs and depletion of HFSEs, and they have no obvious Eu anomaly; they have relatively low MgO contents(2.54–4.93 wt%), Mg# values of 43 to 52, and low Cr and Ni contents(8.07–33.6 ppm and 4.41–14.2 ppm, respectively), indicating they differentiated from primitive mantle magmas. They have low Nb/U, Ta/U, and Ce/Pb ratios(1.3–9.6, 0.2–0.8, and 0.1–18.1, respectively), and their initial Hf isotopic ratios range from +9.6 to +16.9(BSHN diorite) and +6.5 to +12.6(BSBDB gabbro), suggesting their primary magmas were derived mainly from the partial melting of a mantle wedge that had been metasomatized by subduction fluids. Taking all the new data together, we conclude that the western and eastern segment of the Jinshajiang suture regions underwent identical processes of evolution in the Early Permian–Late Triassic: oceanic crust subduction before the Early Permian, continental collision during the Early–Middle Triassic, and post-collisional extension from the Late Triassic.  相似文献   

唐古拉山侏罗系盖覆区空喀拉-温泉-澜沧江结合带鉴别标志     

张森琦 《地球科学与环境学报》2000,22(1)

结合带局部地段被与结合带演化密切伴生的各类盆地盖覆是各造山带中的一种普遍现象 ,因而初步将盖覆结合带的盆地划分为二类 :一是以边缘前陆盆地为代表的盖覆结合带而不破坏结合带的纵向盖覆性盆地 ;二是以横推断层盆地为代表的盖覆且破坏结合带的横向破坏性盆地。区内海相侏罗纪盆地实为与空喀拉温泉澜沧江结合带演化密切相关的盖覆结合带的陆内俯冲型边缘前陆盆地。深部地球物理探测资料证实了结合带在盖覆层之下仍存在 ,更说明结合带两侧板块构造建造对比明显有异 ,分属两类不同性质的大陆边缘 ,进而得出了结合带在研究区内潜伏于盖覆层之下的结论 ,从而建立了结合带存在的三方面的鉴别标志  相似文献   

西拉木伦构造带克德河砂砾岩的时代及构造意义     

郑月娟  张德军  张海华  张健  陈树旺  甄甄 《地质学报》2023,97(8):2459-2475

西拉木伦构造带北部双井地区发育一套巨厚的、成熟度低的快速堆积的粗碎屑沉积建造,为同造山磨拉石沉积,前人称其为克德河砂砾岩带并将其时代分别划为中二叠世(哲斯组)、晚二叠世(林西组)。本次工作对该套地层进行了大比例尺剖面测量,对取自剖面第下、中、上(1、25、86层)三个部分的砂岩样品进行LA-ICP-MS U-Pb年代学研究,结果显示：3个样品具有相似的主要年龄区间,依次为405-485Ma、401-463Ma、363-520Ma,其峰值年龄分别为427Ma、445Ma、440Ma,锆石数量分别占总量的48％、52.5％和38.75％;其次为大于1000Ma的年龄,锆石数量分别占30.7%、22.5%、45%,且均具有1800Ma和2500Ma左右的峰值年龄,明显具有华北板块基底年龄信息;自下而上3个测年样品最年轻峰值年龄分别为312Ma、376Ma,282Ma,最年轻的锆石年龄分别为304Ma、244Ma和245Ma。在第85层杂色复成分砾岩的灰岩砾石中发现晚石炭－早二叠世阿木山组的蜓和珊瑚化石,在41及43层发现中生代孢粉化石。综合碎屑锆石测年及生物化石研究结果,克德河砂砾岩带的时代应为中三叠世。推测西拉木伦构造带经历了一个较长的演化过程,中二叠世开始华北板块和西伯利亚板块进入碰撞造山阶段, 同造山磨拉石建造(克德河砂砾岩带)标志着中亚造山带演化的终止,华北板块和西伯利亚板块的碰撞拼合造山一直延续到中三叠世才结束。  相似文献   

西藏改则洞错地区白垩纪火山岩锆石U-Pb年代学、Hf同位素组成及对班公-怒江洋俯冲闭合的制约   总被引：1，自引：0，他引：1       下载免费PDF全文

付佳俊  丁林  许强  蔡福龙  岳雅慧  郭钰 《地质科学》2015,50(1):182-202

班公湖—怒江缝合带是青藏高原内一条重要的缝合带,其俯冲极性和闭合时限一直存在着争议,这无疑限制了我们对青藏高原演化历史的认识。本文对仲岗安山玄武岩和一套新发现的晚白垩世安山岩进行研究,获得了其锆石U-Pb年龄分别为123.75±0.92 Ma和74.23±0.76 Ma。仲岗安山玄武岩锆石的ε_(Hf)(t)值为-7.3~+4.4,具有岛弧玄武岩特征,指示班公湖—怒江洋盆在该地区仍然继续向北俯冲;晚白垩世安山岩锆石的ε_(Hf)(t)值为+3.1~+11.1,其可能是亏损地幔混熔了部分的陆壳物质而形成的,且不整合在蛇绿岩之上。结合区域资料本文认为班公湖—怒江洋盆在改则地区的闭合时限在100~75 Ma之间。  相似文献   

Zircon U-Pb Geochronology and Hf Isotopic ConstraintsOn Petrogenesis of Plagiogranite from the Cuomuqu Ophiolite, Bangong Lake Area, North Tibet     

YIN Zhengxin  YUAN Yajuan  Lü Baofeng  CAI Zhourong  ZHENG Hao  HUANG Qiangtai  XIA Bin  ZHONG Yun  XIA Zhongyu  SHI Xiaolong  GUAN Yao 《《地质学报》英文版》2015,89(2):418-440

Field observation,geochemical signatures and zircon Hf isotope data indicate that Cuomuqu ophiolite in the Bangonghu area was formed in a back-arc basin(BAB) above a suprasubduction zone(SSZ). Zircon U-Pb dating of the diabase from the Cuomuqu massif yielded an age of 164.3±1.9 Ma,thus indicating that the ophiolite complex was formed in the Middle Jurassic during back-arc extension of the mature Bangonghu-Nujiang Ocean. The zircon εHf(t) and TDMC values of the plagiogranite are similar to the εHf(t) and TDM of the diabase,respectively. The mode of occurrence of plagiogranites and their bulk-rock and Hf isotope characteristics indicate that they were derived from the mantle,associated with the surrounding gabbro and diabase,and were formed by partial melting of altered and hydrated mafic rocks under shear conditions during lateral drifting of the oceanic crust. The zircon U-Pb age of the plagiogranite is 156.4±1.4 Ma,and it is 7.9 Ma younger than the hosting diabase. In this study,zircon chronological and Hf isotopic data were tentatively analyzed to determine the genesis of plagiogranites in the Cuomuqu ophiolite complex.  相似文献   

新特提斯缝合带中段豆荚状铬铁矿成矿规律对比研究     

洪俊  姚文光  张晶  张辉善  吕鹏瑞  杨博 《地质学报》2015,89(9):1618-1628

新特提斯缝合带中的铬铁矿带是全球最重要的豆荚状铬铁矿成矿带之一,尤其是新特提斯缝合带中段,即穆斯林巴赫-科希斯坦-雅鲁藏布江一带,自东向西发育罗布莎、马拉坎德、穆斯林巴赫等若干大型铬铁矿床。本文系统总结和梳理新特提斯缝合带中段蛇绿岩的时空分布特征以及典型豆荚状铬铁矿的矿床特征、赋存规律和控矿因素。研究表明,蛇绿岩形成时代主体为中侏罗世—晚白垩世,自东向西大致呈逐渐变新的趋势,构造侵位的时代相近,为古新世—始新世;马拉坎德、瓦济里斯坦、穆斯林巴赫及贝拉铬铁矿,与罗布莎矿床相似,均属于富铬型铬铁矿,产于SSZ相关构造背景下,显示良好的岩相分带,具有良好的成矿条件;提出下一步找矿方向是针对成矿条件优越的蛇绿岩,解析层序剖面,识别纯橄岩与方辉橄榄岩的岩相分带,确定有利赋矿岩相。  相似文献   

南秦岭勉略蛇绿构造混杂带辉长辉绿岩类微量-稀土元素地球化学   总被引：2，自引：0，他引：2  

赖绍聪 《地球科学与环境学报》2005,27(3):5-9

应用元素地球化学方法．研究了勉略带中辉长辉绿岩的相关特征．结果表明．勉略蛇绿构造混杂带内的辉长岩属高铝强碱质辉长岩类，是地幔橄榄岩部分熔融的产物。辉绿岩墙群属强碱铝质基性岩类，过渡族元素蛛网图与辉长岩类几乎完全相同，其不相容元素与辉长岩类总体趋势相一致．反映了一种递进岩浆演化趋势。因此，本区辉长岩与辉绿岩墙群具同源岩浆分异演化的地球化学特征．其均为勉略蛇绿岩的重要组成端元。  相似文献