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西秦岭北缘早古生代天水—武山构造带位于甘肃省东部天水地区,主要由寒武纪关子镇武山蛇绿岩带、晚寒武世—早奥陶世李子园群浅变质活动陆缘沉积火山岩系、奥陶纪草滩沟群岛弧型火山沉积岩系以及加里东期岛弧型深成侵入岩体、俯冲碰撞型花岗岩体等组成。关子镇蛇绿岩中变质基性火山岩属于NMORB型玄武岩,武山蛇绿岩中变质基性火山岩属于EMORB型玄武岩,是洋脊型蛇绿岩的重要组成部分,形成时代大致在534～489Ma之间的寒武纪。李子园群火山岩主要形成于岛弧或与岛弧相关的弧前盆地构造环境,草滩沟群火山岩形成于与俯冲作用相关的岛弧环境。关子镇流水沟和百花中基性岩浆杂岩总体形成于中晚奥陶世（471～440Ma）古岛弧构造环境,同时发育加里东期俯冲型（450～456Ma）花岗岩类和碰撞型（438～400Ma）花岗岩类岩浆活动。西秦岭北缘早古生代古洋陆构造格局经历了从洋盆形成洋壳俯冲消减直至陆陆碰撞造山的板块构造演化过程。总体构造演化可划分为四个阶段：①晚寒武世古洋盆初始形成阶段;②早奥陶世洋盆初始俯冲阶段;③中晚奥陶世洋壳大规模俯冲与古岛弧发育阶段;④志留纪陆陆或陆弧碰撞造山阶段。 相似文献
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西秦岭北缘早古生代天水—武山构造带及其构造演化 总被引：5，自引：1，他引：4
西秦岭北缘早古生代天水-武山构造带位于甘肃省东部天水地区,主要由寒武纪关子镇-武山蛇绿岩带、晚寒武世-早奥陶世李子园群浅变质活动陆缘沉积-火山岩系、奥陶纪草滩沟群岛弧型火山-沉积岩系以及加里东期岛弧型深成侵入岩体、俯冲-碰撞型花岗岩体等组成.关子镇蛇绿岩中变质基性火山岩属于N-MORB型玄武岩,武山蛇绿岩中变质基性火山岩属于E-MORB型玄武岩,是洋脊型蛇绿岩的重要组成部分,形成时代大致在534～489Ma之间的寒武纪.李子园群火山岩主要形成于岛弧或与岛弧相关的弧前盆地构造环境,草滩沟群火山岩形成于与俯冲作用相关的岛弧环境.关子镇流水沟和百花中基性岩浆杂岩总体形成于中晚奥陶世(471～440Ma)古岛弧构造环境,同时发育加里东期俯冲型(450～456Ma)花岗岩类和碰撞型(438～400Ma)花岗岩类岩浆活动.西秦岭北缘早古生代古洋陆构造格局经历了从洋盆形成-洋壳俯冲消减直至陆-陆碰撞造山的板块构造演化过程.总体构造演化可划分为四个阶段:①晚寒武世古洋盆初始形成阶段;②早奥陶世洋盆初始俯冲阶段;③中晚奥陶世洋壳大规模俯冲与古岛弧发育阶段;④志留纪陆-陆或陆-弧碰撞造山阶段. 相似文献
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甘肃天水地区百花岩浆杂岩的锆石LA-ICP-MSU-Pb定年及其地质意义 总被引：6，自引：0，他引：6
摘〓要：[HT5K]利用阴极发光和LA ICP MS微区定年分析方法,对甘肃天水地区百花岩浆杂岩中的辉长岩进行了单颗粒锆石U Pb同位素分析。百花岩浆杂岩体主要由辉石岩—辉长（闪长）岩—闪长岩—石英闪长岩组成,构成较完整的同源岩浆演化序列,地球化学研究表明其形成于岛弧构造环境。对百花岩浆杂岩中辉长岩的LA ICP MS锆石U Pb同位素定年结果表明,其同位素年龄为(449.7±3.1)Ma（MSWD=1.9）,形成于晚奥陶世,表明西秦岭北带岛弧型岩浆岩的形成时代为晚奥陶世,结合区域地质资料,揭示出以西秦岭北缘关子镇蛇绿岩为代表的古洋盆的俯冲作用及产生岛弧型岩浆活动的时限为中晚奥陶世。
相似文献
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流水沟岩浆杂岩分布于西秦岭北缘天水关子镇地区,主要由变辉长岩、变辉长闪长岩和变闪长岩组成。为确定其构造属性,探讨西秦岭北缘构造演化过程,对其进行了LA-ICP-MS锆石U-Pb测年和主量、微量、稀土元素分析。结果表明,岩浆杂岩体的锆石为岩浆成因,其形成时代为548.7Ma±1.8Ma（MSWD=0.56）。流水沟岩浆杂岩具有SiO2变化范围大（52.47%～66.95%）,低TiO2,低碱,Mg#值变化范围较大的特征,主量元素在SiO2-氧化物变异图解上具有较好的线性相关性。稀土元素配分曲线总体呈近平坦型,LREE/HREE比值多数在1.14～2.60之间,轻重稀土元素分馏较弱,δEu介于0.65～1.90之间,大多数具有弱的负Eu异常;在微量元素蛛网图上,大离子亲石元素Cs、Sr、Th、U富集,Rb、K和高场强元素Nb、P、Ti、Y亏损,Ti/Y=113～253,Th/Yb=0.23～2.85,Th/Nb=0.09～1.00,Hf/Th=0.41～2.97,显示了流水沟岩浆杂岩形成于岛弧环境。流水沟岩浆杂岩可能反映在中央造山系中存在一期与＂泛非造山运动＂有关的构造热事件,为中央造山系在新元古代晚期—早古生代的构造演化提供了证据。 相似文献
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流水沟岩浆杂岩分布于西秦岭北缘天水关子镇地区,主要由变辉长岩、变辉长闪长岩和变闪长岩组成。为确定其构造属性,探讨西秦岭北缘构造演化过程,对其进行了LA-ICP-MS锆石U-Pb测年和主量、微量、稀土元素分析。结果表明,岩浆杂岩体的锆石为岩浆成因,其形成时代为548.7Ma±1.8Ma(MSWD=0.56)。流水沟岩浆杂岩具有SiO2变化范围大(52.47%～66.95%),低TiO2,低碱,Mg#值变化范围较大的特征,主量元素在SiO2-氧化物变异图解上具有较好的线性相关性。稀土元素配分曲线总体呈近平坦型,LREE/HREE比值多数在1.14～2.60之间,轻重稀土元素分馏较弱,δEu介于0.65～1.90之间,大多数具有弱的负Eu异常;在微量元素蛛网图上,大离子亲石元素Cs、Sr、Th、U富集,Rb、K和高场强元素Nb、P、Ti、Y亏损,Ti/Y=113～253,Th/Yb=0.23～2.85,Th/Nb=0.09～1.00,Hf/Th=0.41～2.97,显示了流水沟岩浆杂岩形成于岛弧环境。流水沟岩浆杂岩可能反映在中央造山系中存在一期与"泛非造山运动"有关的构造热事件,为中央造山系在新元古代晚期—早古生代的构造演化提供了证据。 相似文献
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河北承德的大庙斜长岩杂岩体是我国著名的岩体型斜长岩杂岩体,其苏长岩可分为两种类型,即早期苏长岩和晚期辉长—苏长岩。早期苏长岩已发生钠长绿帘角闪岩相变质;晚期辉长—苏长岩变质程度较弱,含有斜长石、斜方辉石和单斜辉石巨晶,主要呈岩墙、岩脉或小岩体侵入于斜长岩杂岩体中,与铁磷矿紧密相关。研究表明:晚期辉长—苏长岩主要由中性斜长石、反条纹长石、单斜辉石、斜方辉石、黑云母、磷灰石、钛磁铁矿和磁铁矿等组成,依矿物含量、成分和结构的差异可分为淡色辉长岩、单斜辉石苏长岩、斜方辉石辉长岩以及含铁磷矿对应岩石。其Ba、Sr和轻稀土富集、Eu弱负异常或无异常特征,表明晚期辉长—苏长岩岩浆不是形成斜长岩的基性岩浆,而是经斜长石分离结晶后的残余岩浆。Sr-Nd-Pb同位素地球化学特征显示晚期辉长—苏长岩可能源自EMI富集的岩石圈地幔,与岩体型斜长岩不存在同源岩浆分离结晶演化的关系。大庙地区晚期辉长—苏长岩的岩浆来源、演化和构造控制的特征对深化研究岩体型斜长岩杂岩体的成因有重要意义。 相似文献
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西秦岭北缘天水地区关子镇蛇绿岩由变质基性火山岩(斜长角闪片岩)和蛇纹岩、变辉石岩、变辉长岩等构造岩块组成.其中的变质基性火山岩具有N-MORB的地球化学特征,显示关子镇蛇绿岩是洋脊型蛇绿岩残片.对蛇绿岩中的辉长岩进行了LA-ICP-MS锆石U-Pb定年,得到206Pb/238U加权平均年龄为(499.7±1.8)Ma(MSWD=2.2),代表了辉长岩的结晶年龄,表明关子镇蛇绿岩是晚寒武世在西秦岭北缘李子园-关子镇-武山洋盆扩张过程中岩浆活动的产物,代表了东秦岭早古生代商丹古洋盆在西秦岭造山带北缘向西延伸的组成部分. 相似文献
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西秦岭关子镇蛇绿混杂岩的地球化学和锆石SHRIMP U-Pb年龄 总被引：3，自引：2，他引：3
西秦岭沿天水武山断裂带产出的关子镇蛇绿混杂岩由变玄武岩、变中-基性深成岩浆岩以及少量蛇纹岩组成。变玄武岩具有平坦或轻稀土略亏损的稀土配分型式((La/Yb)_N=0.63～1.24),且不存在Nb、Ta和Ti的负异常,表明它们形成于洋中脊环境。变中-基性深成岩浆岩包含两种类型:类型Ⅰ显示轻稀土富集((La/Yb)_N>2.2)、具有显著Nb负异常((La/Nb)_N>2.4)的特征,类似于岛弧火山岩;类型Ⅱ显示轻稀土亏损到略富集((La/Yb)_N=0.44～1.38)、无显著Nb负异常((La/Nb)_N<1.5),这些特征与上述变玄武岩类似,表明它们也是关子镇蛇绿岩的组成部分。蛇绿岩中辉长岩和闪长岩(该闪长岩属"大洋斜长花岗岩类")样品的锆石SHRIMP U-Pb年龄分别为534±9Ma和517±8Ma,这反映关子镇蛇绿岩可能为早-中寒武世古洋壳残片。由于西秦岭的天水武山断裂带是东秦岭商丹断裂带的西延并共同被认为是华北和华南陆块之间的主缝合线,上述年龄对理解该带及古秦岭洋的演化提供了重要制约。 相似文献
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红柳河-洗肠井蛇绿混杂岩带位于内蒙古北山造山带中部,呈北西西向展布,向东延伸至白云山-洗肠井蛇绿混杂岩带,向西延伸至牛圈子-红柳园蛇绿混杂岩带。在白云山地区,蛇绿混杂岩由不同类型的岩块与基质组成,基质具有分带性,南侧以砂板岩基质为主,北侧以蛇纹岩基质及绿泥钠长片岩基质为主,反映了俯冲增生杂岩的特征。其中基性熔岩大面积发育,岩性以绿泥钠长片岩及变质玄武岩为主,TAS及AFM图解显示基性熔岩具有拉斑玄武岩的特征,微量元素蛛网图中具有弱Nb-Ta负异常及弱Sr正异常,稀土元素配分曲线显示了轻重稀土基本未分馏的曲线型式,微量元素系列判别图解显示了类似于MORB-like玄武岩的地球化学特征。由此可见,白云山地区基性熔岩为MORB-like玄武岩,反映了蛇绿混杂岩形成于弧前的构造背景。此外,本次工作获得侵入基性熔岩中的斜长花岗岩锆石206Pb/238U加权平均年龄为519.8±2.1Ma,εHf（t）-t图解显示了斜长花岗岩为地幔分异的产物。微量元素蛛网图中Nb-Ta亏损、右倾的稀土配分曲线及Th/Yb-Nb/Yb图解反映了斜长花岗岩具有岛弧岩浆岩的特征。对比研究区晚寒武世岛弧钙碱性辉长岩,我们认为白云山地区早寒武世发育MORB-like玄武岩,中-晚寒武世为岛弧钙碱性辉长岩及斜长花岗岩,反映了初始俯冲-正常俯冲的岩浆作用。 相似文献
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Emily Keeble David I. Whiteside Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):99-119
Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco. 相似文献
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Gilles Serge Odin 《Comptes Rendus Geoscience》2002,334(6):409-414
Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414. 相似文献
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The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts 总被引：4，自引：0，他引：4
The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H2O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H2O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species. 相似文献
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Emmanuel Skourtsos Daniel Vachard Alexandra Zambetakis-Lekkas Rossana Martini Louisette Zaninetti 《Comptes Rendus Geoscience》2002,334(12):925-931
Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931. 相似文献
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正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.) 相似文献
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正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.) 相似文献
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正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.) 相似文献
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正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus., 相似文献
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正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an 相似文献