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1.
北祁连山西段中元古代蛇绿岩的发现及其地质意义 总被引：5，自引：0，他引：5
北祁连山西段中元古代蛇绿岩的发现及其地质意义张招崇（中国地质科学院地质研究所,北京１０００３７）毛景文杨建民左国朝吴茂炳（中国地质科学院矿床地质研究所,北京１０００３７）（甘肃省地矿局地质科学研究所,兰州７３００００）关键词中元古代蛇绿岩北祁连山西段... 相似文献
2.
北祁连山西段螯油沟蛇绿岩SHRIMP分析结果及其地质意义 总被引：8，自引：4，他引：8
本文通过对北祁连山西段熬油蛇绿岩中辉绿岩岩墙的锆石SHRIMP法年龄 的测定，确定出熬油的沟蛇绿岩形成于中元古代早期（约1777Ma)，这是迄今为止我国发现的最古老的蛇绿岩。该年龄测定的结果还暗示了本区在1466Ma和507Ma各有一次地质事件，前者可能代表了中元古代早期的洋盆闭合的下限年龄，后者代表一次加里东期区域变质事件，并且本区可能还存在未出露的新太古结晶基底（2561Ma)。 相似文献
3.
新疆中天山南缘库米什地区蛇绿岩的锆石U-Pb同位素定年:早古生代洋盆的证据 总被引：13，自引：7，他引：6
新疆中天山南缘库米什地区的榆树沟和铜花山蛇绿混杂岩包括地幔橄榄岩,辉石岩、辉长岩、斜长岩等堆晶岩,辉绿岩墙和基性熔岩,以及上部的硅质岩等。岩石地球化学研究表明,蛇绿岩的岩石类型来自MORB型和SSZ型两种构造背景。蛇绿岩及有关岩石的锆石U-Pb同位素年代学的研究表明,与中天山南缘洋盆扩张和闭合有关的事件至少可以分为4期: (1)奥陶纪-志留纪的洋盆形成事件,证据来自蛇绿岩斜长花岗岩和斜长岩,两者的年龄分别为435.1±2.8Ma、439.3±1.8Ma;(2)志留纪的岛弧岩浆作用,获得岛弧火山岩英安岩年龄422.1±2.6Ma 和花岗闪长岩年龄423.1±1.8Ma;(3)泥盆纪的剪切变形和糜棱岩化变质作用,由于板块斜向俯冲和碰撞作用,产生大规模的走滑作用和与之伴生的由剪切作用形成的糜棱岩,糜棱岩的形成年龄为402.8±1Ma,为早泥盆世;(4)俯冲碰撞后的造山带伸展阶段的岩浆作用,在俯冲碰撞作用之后发生与垂直主受力面张裂作用伴生岩浆作用,获得石英正长斑岩294.8±1.2Ma年龄,即晚石炭世。 此外,认为榆树沟蛇绿岩北部出露的麻粒岩是一个很特殊的构造岩块,岩石的锆石中普遍存在500~1800Ma的老核,表明其原岩很复杂,不属于蛇绿岩的组合 。 相似文献
4.
北祁连西段熬油沟辉长岩的锆石SHRIMP U-Pb年龄及地质意义 总被引：8，自引：2，他引：8
从北祁连熬油沟辉长岩中选出的锆石的外部形态、内部结构单一。SHRIMP测年共测定8个点,每个点的Th/U值都非常高,大都在0.8以上。8个点的206Pb/238U表面年龄在误差范围内完全一致,加权平均值为503.7Ma±6.4Ma,这一结果与前人在同一地点采集的辉绿岩墙样品的锆石SHRIMP U-Pb测年结果有较大的差异。结合研究区内已有的研究成果认为:①熬油沟地区的辉长辉绿岩形成于早古生代,并不是中元古代早期。②辉长岩中的锆石成因单一,其测试年龄结果的地质意义明确;而同源岩浆侵入体的辉绿岩往往容易从围岩中捕获大量锆石,使得锆石成因复杂,年龄测试结果复杂。因此,与辉绿岩相比,辉长岩锆石SHRIMP U-Pb年代学研究可以获得更为可靠的、地质意义明确的年龄信息。 相似文献
5.
《地学前缘(英文版)》2020,11(6):2017-2029
The newly discovered early Paleozoic Delenuoer ophiolite, in the western margin of the Central Qilian Shan, is composed of serpentinized peridotite, cumulate gabbro, diabase, massive basalt, and pillow basalt. This study presents geochronological and geochemical data for the cumulate gabbro and basalt. LA–ICP–MS U–Pb dating of zircons from the cumulate gabbro yielded a magmatic crystallization age of 472 ± 4 Ma. The basalts have normal mid-ocean ridge basalt (N-MORB) compositions and a narrow range of εNd(t) values (+4.5 to +5.3), which indicates they were derived from a depleted mantle source. On the basis of regional geological constraints, it is proposed that the Delenuoer ophiolite is a westward extension of the South Ophiolite Belt (Yushigou–Youhulugou–Donggou–Dongcaohe Ophiolite Belt) in the North Qilian Shan. The Delenuoer ophiolite, along with the Gulangxia–Delenuoer fault, defines the westernmost part of the tectonic boundary between the North and Central Qilian Shan. This ophiolite may have formed during southward subduction of the Qilian Ocean slab during the early Paleozoic. 相似文献
6.
班- 怒带东段丁青蛇绿岩中镁铁质岩石年代学及构造背景 总被引：1，自引：0，他引：1
丁青蛇绿岩位于班公湖-怒江缝合带东段,分为东、西两个蛇绿岩体,丁青西蛇绿岩体缺乏基性岩年代学研究。对丁青西地质填图显示,蛇绿岩主要由方辉橄榄岩、纯橄榄岩、辉绿岩、玄武岩及辉长岩组成。其中玄武岩、辉长岩及辉绿岩出露在宗白区域,玄武岩和辉绿岩与下侏罗统沉积岩呈构造接触,辉长岩呈岩脉侵入到下侏罗统沉积岩中。岩石地球化学研究表明,玄武岩和辉长岩同属于碱性基性岩石,其中玄武岩具有典型洋岛玄武岩的稀土和微量元素特征,可能形成于与地幔柱有关的洋岛环境。在玄武质凝灰岩中挑选出的锆石测年,获得U-Pb年龄为198.7±3.8Ma,属早侏罗世。辉长岩的稀土和微量元素含量低于典型洋岛玄武岩,但其REE和微量元素具有OIB的特征,与典型OIB相比,辉长岩的HREE发生了一定程度富集。辉长岩锆石的U-Pb年龄为164.3±2.6Ma,认为辉长岩在形成过程中受到了软流圈地幔和岩石圈下部LVZ中富集熔体的共同作用,其形成于大陆边缘裂谷环境;辉绿岩成分属于拉斑系列岩石,其REE和微量元素曲线显示辉绿岩同时具有N-MORB和E-MORB的特征。辉绿岩锆石U-Pb年龄为114.2±1.3Ma,其形成晚于玄武岩。结合区域地质,认为辉绿岩形成于受地幔柱影响的弧后扩张脊环境。本研究提供了丁青西蛇绿岩新的年代学和岩石学证据,为探讨丁青蛇绿岩的形成和演化历史提供了新的证据。 相似文献
7.
XIA Linqi LI Xiangmin XU Xueyi XIA Zuchun MA Zhongping WANG Lishe Xi''an Institute of Geology Mineral Resources China Geological Survey Xi''an Shaanxi 《《地质学报》英文版》2005,79(2):174-192
The Bayan Gol ophiolite fragment is a portion of the North Tianshan Early Carboniferous ophiolite belt. This ophiolite belt represents a geological record of an Early Carboniferous “Red Sea type” ocean basin that was developed on the northern margin of the Tianshan Carboniferous-Permian rift system in northwestern China. The late Early Carboniferous Bayan Gol ophiolite suite was emplaced in an Early Carboniferous rift volcanosedimentary succession of shallow-marine to continental facies (Volcanics Unit). Ophiolitic rocks in the Bayan Gol area comprise ultramafic rocks, gabbros with associated plagiogranite veins, diorite, diabase, pillow basalts and massive lavas. The Early Carboniferous tiffing and the opening process of the North Tianshan ocean basin produced mafic magmas in composition of tholeiite and minor amounts of evolved magmas. Compositions of trace elements and Nd, Sr and Pb isotopes reveal the presence of two distinct mantle sources: (1) the Early Carboniferous rift mafic lavas from the Volcanics Unit were generated by a relatively low degree of partial melting of an asthenospheric OIB-type intraplate source; (2)younger (late Early Carboniferous, -324.8 Ma ago) mafic lavas from the Ophiolite Unit were formed in a relatively depleted MORB-like mantle source, located in the uppermost asthenosphere and then gradually mixed with melts from the asthenospheric OIB-like mantle. A slight interaction between asthenosphere-derived magmas and lithospheric mantle took place during ascent to the surface. Subsequently, the most depleted mafic lavas of the ophiolite assemblage were contaminated by upper-crustal components (seawater or carbonate crust). 相似文献
8.
The eastern margin of the Qaidam Basin lies in the key tectonic location connecting the Qinling, Qilian and East Kunlun orogens. The paper presents an investigation and analysis of the geologic structures of the area and LA-ICP MS zircon U-Pb dating of Paleozoic and Mesozoic magmatisms of granitoids in the basement of the eastern Qaidam Basin on the basis of 16 granitoid samples collected from the South Qilian Mountains, the Qaidam Basin basement and the East Kunlun Mountains. According to the results in this paper, the basement of the basin, from the northern margin of the Qaidam Basin to the East Kunlun Mountains, has experienced at least three periods of intrusive activities of granitoids since the Early Paleozoic, i.e. the magmatisms occurring in the Late Cambrian (493.1±4.9 Ma), the Silurian (422.9±8.0 Ma-420.4±4.6 Ma) and the Late Permian-Middle Triassic (257.8±4.0 Ma-228.8±1.5 Ma), respectively. Among them, the Late Permian - Middle Triassic granitoids form the main components of the basement of the basin. The statistics of dated zircons in this paper shows the intrusive magmatic activities in the basement of the basin have three peak ages of 244 Ma (main), 418 Ma, and 493 Ma respectively. The dating results reveal that the Early Paleozoic magmatism of granitoids mainly occurred on the northern margin of the Qaidam Basin and the southern margin of the Qilian Mountains, with only weak indications in the East Kunlun Mountains. However, the distribution of Permo-Triassic (P-T) granitoids occupied across the whole basement of the eastern Qaidam Basin from the southern margin of the Qilian Mountains to the East Kunlun Mountains. An integrated analysis of the age distribution of P-T granitoids in the Qaidam Basin and its surrounding mountains shows that the earliest P-T magmatism (293.6-270 Ma) occurred in the northwestern part of the basin and expanded eastwards and southwards, resulting in the P-T intrusive magmatism that ran through the whole basin basement. As the Cenozoic basement thrust system developed in the eastern Qaidam Basin, the nearly N-S-trending shortening and deformation in the basement of the basin tended to intensify from west to east, which went contrary to the distribution trend of N-S-trending shortening and deformation in the Cenozoic cover of the basin, reflecting that there was a transformation of shortening and thickening of Cenozoic crust between the eastern and western parts of the Qaidam Basin, i.e., the crustal shortening of eastern Qaidam was dominated by the basement deformation (triggered at the middle and lower crust), whereas that of western Qaidam was mainly by folding and thrusting of the sedimentary cover (the upper crust). 相似文献
9.
北祁连山中段早中奥陶世蛇绿岩中席状岩墙杂岩的发现及其地质意义 总被引：7，自引：0，他引：7
作为蛇绿岩套重要组成部分之一的席状岩墙杂岩(Sheeted dyke complex)近来在北祁连山中段肃南县大岔大坂北坡的早中奥陶世蛇绿岩中被发现。这一发现对于祁连山早古生代蛇绿岩来说尚属首次,而且对于研究蛇绿岩的发展演化及探讨奥陶纪时洋底扩张都有重要意义。席状岩墙杂岩由一系列具单向冷凝边的辉绿岩墙组成,以一墙挨一墙的形式产出,岩墙间无任何填充物。席状岩墙杂岩在矿物组合上,常量元素、稀土元素及痕量元素地球化学特征和配分模式,甚至金属硫化物矿化作用方面都有类似之处。这些证据表明席状岩墙杂岩是连通其下岩浆房与其上枕状熔岩的通道。席状岩墙的单向冷凝边为岩浆上升方式和扩张洋脊的存在提供了令人信服的证据。根据Zr/Y—Zr关系图式,得出该区洋脊的扩张速率大约为2cm/a。 相似文献
10.
北祁连东段红土堡基性火山岩锆石LA -IC P-MS U-Pb年代学及其地质意义 总被引：10，自引：0，他引：10
为精确限定红土堡基性火山岩的形成时代，结合阴极发光分析，分别对北祁连东段红土堡枕状玄武岩和辉绿岩墙进行了LA - ICP - MS 单颗粒锆石微区U - Pb 同位素测年。红土堡枕状玄武岩获得（443.4 ±1.7 ）Ma 和（1 782 ±34 ）Ma 两组年龄值；同时，获得红土堡基性火山岩中辉绿岩墙的年龄为（385.7 ±7.9 ）Ma，并含有（1 697 ±6 ） ～（2 692 ±4 ）Ma 的捕晶锆石年龄信息。认为红土堡基性火山岩的形成时代为晚奥陶世，与其北的陈家河中酸性火山岩的形成时代大体一致，推断红土堡基性火山岩的原始岩浆不同程度遭受了陇山岩群的混染。这一新资料，对进一步研究北祁连造山带东段大地构造格局、构造演化以及北秦岭—北祁连衔接关系具有重要意义。 相似文献
11.
对青藏高原西北部班公湖缝合带开展了路线剖面地质调查,在北面日土蛇绿岩带上采得2处镁铁质岩墙(辉长岩和辉绿岩),岩石地球化学分析表明这两处镁铁质岩墙具有平缓的球粒陨石标准化稀土元素分布型式,显示出洋中脊玄武岩特征,说明它们形成于洋中脊环境,其锆石U-PbLAICPMS年龄测定结果分别为(181.9±2.6)Ma(MSWD=11.5)和(184.4±4.4)Ma(MSWD=2.2),表明班公湖中特提斯洋是在早侏罗世晚期打开的。另外,在狮泉河—改则蛇绿岩带上采得橄榄辉绿岩,岩石以K2O(质量分数为1.49%～1.56%)、Al2O3(质量分数为14.76%～15.21%)含量高,Fe2O3/FeO比值高(1.73～2.49),富集大离子不相容元素(Rb、Ba、Th、Sr)和轻稀土元素(LREE)为特点,在基性岩构造环境判别图上显示出洋岛玄武岩的亲合性。该样品给出的(176.2±9.0)Ma(MSWD=3.1)的锆石U-PbLAICPMS年龄说明,班公湖中特提斯洋从早侏罗世晚期打开,经过近10Ma的扩张至中侏罗世早期已变成一个成热的洋盆。 相似文献
12.
班公湖?怒江结合带西段班公湖地区蛇绿岩组合较为完整,由超镁铁质岩、镁铁质堆晶岩、辉绿岩脉、铁镁质熔岩、放射虫硅质岩等组成。这套蛇绿岩所代表的洋盆打开时间一直争论不休。该蛇绿岩中MOR型辉长岩的LA-ICP-MS锆石U-Pb定年显示,18个测点的~(206)Pb/~(238)U加权平均年龄为231.5±2.6 Ma,代表了辉长岩的结晶年龄。地球化学分析表明辉长岩SiO_2含量在46.12%~47.85%之间,TiO_2(1.52%~1.71%),具低的K_2O(0.19%~0.25%)、Al_2O_3(12.97%~13.51%)和Fe_2O_3/FeO比值(0.19~0.24);微量元素蛛网图与洋中脊玄武岩类似,Zr、Nb、Ta、Hf丰度与N-MORB相当或略高,相对富集Ba、Pb、Sr等大离子亲石元素,无Ta-Nb负异常,在基性岩构造环境判别图上显示出洋脊玄武岩的亲合性;REE配分曲线具有平缓型特点,介于E-MORB与N-MORB之间;各种地球化学特征与洋脊玄武岩类似,表明该辉长岩是在班公湖洋盆扩张阶段形成的。结合前人研究成果,本文认为班公湖中特提斯洋盆初始打开时间至少为中三叠世。 相似文献
13.
A cold Early Palaeozoic subduction zone in the North Qilian Mountains, NW China: petrological and U-Pb geochronological constraints 总被引：17，自引：1，他引：17
The north Qilian high‐pressure (HP)/low‐temperature (LT) metamorphic belt is composed mainly of blueschists, eclogites and greenschist facies rocks. It formed within an Early Palaeozoic accretionary wedge associated with the subduction of the oceanic crust and is considered to be one of the best preserved HP/LT metamorphic belts in China. Here we report new lawsonite‐bearing eclogites and eclogitic rocks enclosed within epidote blueschists in the North Qilian Mountains. Five samples contain unaltered lawsonite coexisting with omphacite and phengite as inclusions in garnet, indicating eclogite facies garnet growth and lawsonite pseudomorphs were observed in garnet from an additional 11 eclogites and eclogitic rocks. Peak pressure conditions estimated from lawsonite omphacite‐phengite‐garnet assemblages were 2.1–2.4 GPa at temperatures of 420–510 °C, in or near the stability field of lawsonite eclogite, and implying formation under an apparent geothermal gradient of 6–8 °C km?1, consistent with metamorphism in a cold subduction zone. SHRIMP U‐Pb dating of zircon from two lawsonite‐bearing eclogitic metabasites yields ages of 489 ± 7 Ma and 477 ± 16 Ma, respectively. CL images and mineral inclusions in zircon grains indicate that these ages reflect an eclogite facies metamorphism. An age of 502 ± 16 Ma is recorded in igneous cores of zircon grains from one lawsonite pseudomorph‐bearing eclogite, which is in agreement with the formation age of Early Ordovician for some ophiolite sequences in the North Qilian Mountains, and may be associated with a period of oceanic crust formation. The petrological and chronological data demonstrate the existence of a cold Early Palaeozoic subduction zone in the North Qilian Mountains. 相似文献
14.
查涌蛇绿岩为甘孜-理塘缝合带在青藏高原北羌塘盆地治多地区的北延部分,由基性堆晶岩、辉绿岩墙群、基性喷出岩及沉积成因的硅质岩组成,缺乏地幔橄榄岩。受后期构造强烈破坏,岩石变质变形较强,多呈被肢解的构造岩块、岩片产出。堆晶岩包括蚀变橄榄辉石岩、辉长岩,蚀变橄榄辉石岩具有低SiO2、TiO2、P2O5含量及高MgO含量的特征,Rb、Th、Cr等元素呈强富集型,Sr、Nb、Y等元素具亏损型;辉长岩低SiO2及K2O含量,高MgO、TiO2及Al2O3含量;辉绿岩墙以Rb、Ba、Th等元素的明显富集和Y、Yb的轻微亏损为特征,微量元素蛛网图曲线与洋中脊玄武岩类似;玄武岩具高TiO2含量、低K2O含量,属低钾拉斑玄武岩系列,轻重稀土元素分馏程度明显,具有轻稀土富集型,铕不显异常,玄武岩REE模式呈近平坦型曲线,与大洋玄武岩特征相似。由上述蛇绿岩地球化学特征及结合区域地质、构造环境等特征,推测查涌蛇绿岩产于洋盆环境。 相似文献
15.
祁连山蛇绿岩带和原特提斯洋演化 总被引：2，自引：1，他引：1
位于阿拉善地块和柴达木地块之间的祁连造山带记录原特提斯洋扩张、俯冲、闭合、大陆边缘增生和碰撞造山的完整过程。从南向北,祁连造山带发育有三条平行排列、不同类型的蛇绿岩带:(1)南部南祁连洋底高原-洋中脊-弧后蛇绿岩混杂带;(2)中部托勒山洋中脊型蛇绿岩带;(3)北部走廊南山SSZ型蛇绿岩带。南部南祁连蛇绿混杂岩带以拉脊山-永靖蛇绿岩为代表,为典型的洋底高原型蛇绿岩,是大洋板内地幔柱活动的产物,形成年龄为525～500Ma;中部托勒山蛇绿岩带沿熬油沟-玉石沟-冰沟-永登一线分布,为大洋中脊型蛇绿岩,蛇绿岩形成年龄为550～495Ma;北部蛇绿岩带包括弧前和弧后两种类型,弧前蛇绿岩以大岔大阪蛇绿岩为代表,形成时代为517～487Ma,反映初始俯冲/弧前扩张到弧后盆地的过程;弧后蛇绿岩以九个泉-老虎山蛇绿岩为代表,为典型的SSZ型蛇绿岩,是弧后扩张的产物,形成时代为奥陶纪(490～445Ma)。三个蛇绿岩带分别代表了新元古代-早古生代祁连洋演化历史不同环境的产物,对了解秦祁昆构造带原特提斯洋的构造演化过程有重要意义。蛇绿岩及弧火山岩的时空分布特征限定了原特提斯洋的俯冲极性为向北消减俯冲。 相似文献
16.
The Zedong ophiolite is the largest ophiolite massif east of Dazhuqu in the Yarlung Zangbo Suture Zone in the southern Tibetan Plateau. However, its age, geodynamic setting and relationship to the Xigaze ophiolite remain controversial. New zircon U–Pb ages, whole-rock geochemical and Nd–Pb isotopic data from ophiolitic units provide constraints on the geodynamic and tectonic evolution of the Zedong ophiolite. U–Pb zircon geochronology of dolerite lavas and late gabbro–diabase dikes yield weighted mean ages of 153.9 ± 2.5 Ma and 149.2 ± 5.1 Ma, respectively. Strong positive εNd(t) and positive Δ7/4Pb and Δ8/4Pb values indicate derivation from a highly depleted mantle source with an isotopic composition similar to that of the Indian MORB-type mantle. The geochemistry of ophiolitic lavas and early dikes are analogous to typical island arc tholeiites whereas late dikes are similar to boninites. The geochemistry of these rock types suggests multi-stage partial melting of the mantle and gradually enhanced subduction influences to the mantle source through time. Combined with the MORB-like 162.9 ± 2.8 Ma Luobusha ophiolitic lavas, we suggest that the Luobusha lavas, Zedong lavas and early dikes originated in an infant proto-arc setting whereas late dikes in the Zedong ophiolite originated in a forearc setting. Together, they represent a Neo-Tethyan subduction initiation sequence. The Late Jurassic intra-oceanic proto-arc to forearc setting of the Zedong ophiolite contrasts with the continental margin forearc setting for the Xigaze ophiolite, which suggests a laterally complex geodynamic setting for ophiolites along the Yarlung Zangbo Suture Zone. 相似文献
17.
CHAN Lung Sang 《《地质学报》英文版》2019,93(Z2):9-9
Many ophiolite complexes like those of Oman and New Caledonia represent fragments of ancient oceanic crust and upper mantle generated at supra‐subduction zone environments and have been obducted onto the adjacent rifted continental margin together with the accretionary complexes and intra‐oceanic arcs. The Lajishan ophiolite complexes in the Qilian orogenic belt along the NE edge of the Tibet‐Qinghai Plateau are one of several ophiolites situated to the south of the Central Qilian block. Our geological mapping and petrological investigations suggest that the Lajishankou ophiolite complex consists of serpentinite, wehrlite, pyroxenite, gabbro, dolerite, and pillow and massive basalts that occur in a series of elongate fault‐bounded slices. An accretionary complex composed mainly of basalt, radiolarian chert, sandstone, mudstone, and mélange lies structurally beneath the ophiolite complex. The Lajishankou ophiolite complex and accretionary complex were emplaced onto the Qingshipo Formation of the Central Qilian block which shows features typical of turbidites deposited in a deep‐water environment of passive continental margin. Our geochemical and geochronological studies indicate that the mafic rocks in the Lajishankou ophiolite complex can be categorized into three distinct groups: massive island arc tholeiites, 509 Ma back‐arc dolerite dykes, and 491 Ma pillow basaltic and dolerite slices that are of seamount origin in a back‐arc basin. The ophiolite and accretionary complex constitute a Cambrian‐early Ordovician trench‐arc system within the South Qilian belt during the early Paleozoic southward subduction of the South Qilian Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. 相似文献
18.
贺根山蛇绿岩（套）中发育有气孔杏仁状玄武岩,为蛇绿岩套的组成部分。通过对其锆石U-Pb测年,其加权平均年龄为395.9 Ma±3.0 Ma,结合区域地质背景,认为贺根山蛇绿岩（套）形成时代为中泥盆世—早石炭世。玄武岩为亚碱性系列,具有LREE亏损、类似N-MORB的稀土配分模式,同时具备大洋玄武岩和岛弧玄武岩特征,认为贺根山蛇绿岩（套）应形成于弧后盆地;通过与现代典型Mariana洋内弧后盆地和Okinawa陆缘弧后盆地的玄武岩以及同属中亚造山带的新疆库尔提洋内弧后盆地蛇绿岩对比,发现贺根山玄武岩同Mariana玄武岩和库尔提蛇绿岩更加类似,由此认为贺根山蛇绿岩（套）很可能形成于洋内弧后盆地环境,而非大陆边缘弧后盆地环境。 相似文献
19.
Late Palaeozoic tectonic setting of the southern Alxa Block,NW China: constrained by age and composition of diabase 总被引：3，自引：0，他引：3
Yiping Zhang Xuanhua Chen Yannan Wang Heng Zhao Fengjun Nie 《International Geology Review》2017,59(8):1028-1046
The ages of diabase outcropping on the southern Alxa Block and in related tectonic setting are not well constrained, but are important for exploring the tectonic evolution of the southern Alxa Block. The ages of the zircons from the diabase intruding the Middle–Late Cambrian Xiangshan Group were measured using sensitive high-resolution ion microprobe II (SHRIMPII) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and the weighted mean ages of 276.8 ± 7.9 Ma and 276.2 ± 9.7 Ma were obtained, respectively. The major elements in the diabase indicate that it may belong to the tholeiitic series. With specific features of the rare earth elements (REEs) and trace elements, potentially affected by the continental crust based on the observed strong positive Pb anomaly, the diabase was produced in an intra-plate extension environment. Similar diabase/basalts were also found along the southern margin of the Alxa Block. Combined with sedimentary, palaeo-current, mafic, and felsic rocks in the southern Alxa Block, a back-arc extension environment potentially occurred in the southern Alxa Block during the Early–Middle Permian that resulted from the convergence between the North China Block (NCB) and the Yangtze Block. 相似文献
20.
中国西部柴北缘—阿尔金的超高压变质榴辉岩及其原岩性质探讨 总被引：45，自引：5，他引：45
中国西部祁连山柴北缘地区和南阿尔金地区存在一条被阿尔金断裂错开 4 0 0km ,但构造上相连的早古生代超高压变质带。通过对柴北缘地区大柴旦、锡铁山、都兰和南阿尔金地区且末一带榴辉岩的岩石地球化学研究 ,发现榴辉岩原岩主要由玄武岩和苦橄岩两类岩石组成 ,进一步分为高Ti型 (w(TiO2 ) =2 %～ 5 % ) ,中Ti型 (1%～ 2 % )和低Ti型 (<1% ) 3种类型 ,识别出榴辉岩的原岩类型有洋脊玄武岩、岛弧拉斑玄武岩和洋岛玄武岩类等产在不同环境的岩石类型。榴辉岩的Nd同位素组成与现代洋脊玄武岩类相似 ,ε(Nd ,0 )主要为正值 ,少量为轻微负值 ,表明榴辉岩的原岩曾是海底玄武岩 ,并且经过了消减俯冲作用 ,混入了部分的地壳物质。榴辉岩的超高压变质年龄为 5 0 0～ 4 4 0Ma,原岩年龄分别为 80 0～ 75 0Ma和～ 10 0 0Ma。研究表明 ,柴北缘滩涧山群中存在两套时代不同的基性超基性岩 ,一套为产在绿梁山的新元古代时期形成的蛇绿岩组合 ,新获得的年龄值为 (76 8±39)Ma(Rb Sr)和 (780± 2 2 )Ma(Sm Nd) ,另一套主要为产在赛什腾山的晚寒武世岛弧火山岩 ,形成时代约在 5 15～ 4 86Ma。榴辉岩的岩石化学成分和Nd同位素组成 ,以及 80 0～ 75 0Ma的原岩时代与其中的新元古代基性岩类可以对比。初步认为它们是同一套岩石? 相似文献