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1.
北秦岭西段宽坪岩群斜长角闪岩锆石LA-ICP-MS测年及其地质意义 总被引：6，自引：0，他引：6
甘肃天水东岔镇一带出露的宽坪岩群位于北祁连—北秦岭—华北板块交界地带,呈残留体状分布于花岗岩之中,主体为一套低角闪岩相变质的片麻岩、片岩夹斜长角闪岩。利用西北大学大陆动力学重点实验室LA-ICP-MS(激光剥蚀等离子体质谱)方法,对其中的斜长角闪岩进行单颗粒锆石微区U-Pb同位素测定,获得1753±14Ma的上交点年龄,为古元古代晚期;并反映出415±2Ma～383±2Ma的变质年龄信息。结合前人研究成果,认为区域上宽坪岩群主体形成年龄为中元古代,而研究区的宽坪岩群形成于古元古代,受到加里东晚期和华力西早期构造—热事件的改造。推测研究区的宽坪岩群可能属于华北古老基底南缘的组成部分。 相似文献
2.
北祁连东段红土堡基性火山岩锆石LA-ICP-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
3.
本文对秦岭—祁连结合部陇山构造带内部侵入于陇山岩群中的片麻状二长花岗岩和其中的黑云斜长片麻岩包裹体进行了地球化学和独居石、锆石U-Pb年代学研究。片麻状二长花岗岩具有I型花岗岩的地球化学特征,对其进行的LA-ICP-MS独居石U-Pb测年获得年龄433.5?1.8 Ma,锆石U-Pb测年获得了三个主峰年龄（439.5 Ma、634.5 Ma和2265 Ma）和五个次级峰值年龄（568.7 Ma、1875 Ma、2112 Ma、2604 Ma和2738 Ma）。黑云斜长片麻岩的地球化学特征反映其原岩是经历过显著的结晶分异作用的中基性岩,在其中分选出了两类锆石：（1）环带清晰且经受了热液蚀变的岩浆锆石,对其U-Pb测年获得了一条很好的不一致线,不一致线的上、下交点年龄分别是2194?42 Ma和431.2?58.1 Ma;（2）CL图像整体很暗的变质锆石或热液蚀变锆石,在这类锆石中获得了峰值年龄513.1 Ma。结合区域地质资料,本文把片麻状二长花岗岩的形成时间限定为431.2-439.5 Ma,把黑云斜长片麻岩原岩的形成时间限定为2194?42 Ma。片麻状二长花岗岩与文献揭示的围岩（斜长角闪片岩）的形成时间基本一致,暗示431.2-439.5 Ma期间陇山地区大量发育中基性和酸性岩浆活动,岩浆作用具有显著的地区差异特点。北祁连洋盆和北秦岭西段洋盆向北的俯冲活动在513.1 Ma时可能影响到了本文研究区。2738 Ma、2604 Ma、2112 Ma-2265 Ma和1875 Ma等峰值年龄分别应该是华北克拉通在新太古代晚期的陆壳生长事件和古元古代早期克拉通裂解事件在研究区的反映。634.5 Ma期间研究区可能处于一种未知的特别的构造环境。总体来看,陇山构造带在前寒武纪时作为华北地块的一部分而演化,显生宙以来其构造演化过程受到秦岭造山带和北祁连造山带的显著影响。 相似文献
4.
秦岭造山带是中朝克拉通华北板块和扬子克拉通板块结合区域.其基底组成为广大地质学家所关注.笔者报道了秦岭造山带中部陕西省商南县湘河地区楼房沟古变质结晶岩片斜长角闪岩-浅粒岩和黑云二长石英片岩的SHRIMP锆石U-Pb年龄数据,讨论了其地质意义.斜长角闪岩-浅粒岩为同-岩浆连续分异变质火山岩,锆石Pb严重丢失,207Pb/206Pb年龄≥(2488±8)Ma.年龄值与已获得的Sm-Nd等时年龄值在误差范围内一致.黑云二长石英片岩为副变质岩,锆石U-Pb年龄(978±13)Ma.秦岭造山带中部老于太古宇岩片(块)的发现表明,秦岭造山带下部可能存在过太古宙结晶基底. 相似文献
5.
祁连山西段甘肃肃北地区北大河岩群片麻状斜长角闪岩的形成时代 总被引：8，自引：3，他引：5
对祁连造山带西段最古老变质岩系之一的北大河岩群的碎屑锆石SHRIMPU-Pb同位素年代学研究表明,其沉积作用发生于1400～863Ma之间,而不是前人所认为的古元古代。通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱仪)锆石微区原位U-Pb同位素测年,在甘肃省肃北蒙古族自治县党河一带北大河岩群片麻状斜长角闪岩中获得(724.4±3.7)Ma的谐和年龄,为原岩(辉长岩)的形成时代,该年龄相当于Rodinia超大陆裂解的地质记录。此外,还获得1949～1184Ma之间的捕获锆石年龄信息。该项研究对确定祁连造山带存在Rodinia超大陆裂解事件具有重要意义,并可进一步限定北大河岩群的形成时代介于1400～724Ma之间。 相似文献
6.
甘肃马衔山花岗岩杂岩体LA-ICPMS锆石U-Pb测年及其构造意义 总被引：5，自引：0，他引：5
甘肃马衔山侵入杂岩体位于祁连造山带的东部,侵入于新太古代—古元古代变质基底岩系(马衔山岩群)中,主体岩石类型为片麻状二长花岗岩,其次为侵入于片麻状二长花岗岩中的钾长花岗岩。利用LA-ICPMS(激光剥蚀等离子体质谱)测年设备,对片麻状二长花岗岩进行单颗粒锆石微区U-Pb同位素测定,获得1192±38Ma的年龄,为中元古代晚期;岩石地球化学特征显示二长花岗岩侵入体具有火山弧-同碰撞花岗岩特征。马衔山变形侵入体所代表的热—构造事件与格林威尔造山运动时代(1190～980Ma)相当,可能与Rodinia超大陆形成有一定的成因联系。这一新的资料,对研究祁连造山带元古宙大地构造格局、构造演化及中国大陆动力学具有重要意义。 相似文献
7.
作为南祁连造山带基底残块的化隆岩群,由于产出有与Cu-Ni(-PGE)矿紧密相关的基性-超基性岩而倍受关注。随着一些新元古代精细锆石同位素年代学数据的获得,化隆岩群形成于太古-古元古代的传统认识发生了动摇。通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱)锆石微区原位U-Pb同位素测年,获得青海省湟源县南日月乡一带化隆岩群条带状二云斜长片麻岩(副变质岩)最新的蚀源区年龄为891±7Ma,代表化隆岩群形成时代的下限;条带状黑云斜长角闪岩(原岩为中性火山岩)的形成年龄为884±9Ma,将化隆岩群的形成时代进一步限定为新元古代。认为化隆岩群火山-沉积作用应为Rodinia超大陆裂解的地质记录,Rodinia超大陆裂解事件及其相关的成矿作用在祁连造山带及其邻区前寒武纪占据不可低估的重要地位。 相似文献
8.
为了搞清大别山地区高压麻粒岩和高压超高压榴辉岩的关系,了解大别山地区加里东期构造-热事件的性质和特征,探索大别造山带的区域延伸和对比等,选择大别山东部惠兰山麻粒岩及安徽太湖石马榴辉岩的直接围岩——含榴斜长片麻岩进行了同位素年代学研究。惠兰山麻粒岩呈似层状夹于长英质片麻岩中,岩性为石榴角闪二辉麻粒岩,其峰变质条件t=682～880℃;P=0.9～1.29 GPa,峰变质压力与大别山西部熊店加里东期榴辉岩相当。惠兰山麻粒岩存在两类不同晶形特征和不同成因的锆石。其中长柱状锆石用~(207)Pb/~(206)Pb蒸发法给出平均年龄443±23 Ma,代表了麻粒岩相峰变质年龄;浑圆粒状锆石用同样方法给出的年龄为2300±15 Ma,可能反映麻粒岩原岩形成年龄或前期变质事件的时代。石马含榴斜长片麻岩 相似文献
9.
甘肃天水地区早古生代黄门川花岗闪长岩体LA-ICP-MS锆石U-Pb定年及构造意义 总被引：3，自引：1，他引：2
甘肃天水地区黄门川花岗闪长岩体位于北祁连造山带东端,侵位于晚奥陶世陈家河群中酸性火山岩系中,岩石学和地球化学特征表明其具有壳幔岩浆混合的特点。对黄门川花岗闪长岩体进行了LA-ICP-MS锆石U-Pb定年,结果表明该花岗闪长岩体的年龄为440.5Ma±4.4Ma,形成于早志留世。地球化学特征表明,黄门川花岗闪长岩体属于中钾钙碱性系列,具I型花岗岩的特征。构造环境判别表明其形成于安第斯型大陆边缘弧。综合区域地质背景,认为祁连造山带东端在早古生代期间发育有有限洋盆,洋盆向北俯冲消减产生大量弧岩浆岩。对进一步研究祁连与秦岭造山带构造交接部位早古生代的构造格局、演化等大陆动力学问题具有重要意义。 相似文献
10.
胶东海阳所斜长角闪岩的锆石 U-Pb 年龄——多期变质作用对锆石不一致线年龄影响的实例 总被引：6，自引：0，他引：6
胶东海阳所胶南群斜长角闪岩中的锆石有2类：（1）捕掳晶锆石，它给出2149Ma 的207Pb/206Pb 年龄，证明该区存在有早元古基底；（2）岩浆结晶锆石，它的不一致线上下交点年龄分别为1784±11Ma和448±13Ma。然而该锆石在晋宁期和印支期曾发生2次铅丢失事件，从而使其下交点年龄（448±13Ma）无地质意义。其上交点年龄指示了该锆石的最小结晶时代，它表明在18亿年时该地区曾有一次玄武质火山岩事件。 相似文献
11.
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
12.
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
13.
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
14.
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
15.
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
16.
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
17.
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
18.
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
19.
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
20.
正20141266Fan Chaoyan(Guangdong Provincial Key Laboratory of Mineral Resources and Geological Processes,Guangzhou 510275,China);Wang Zhenghai On Error Analysis and Correction Method of Measured Strata Section with Wire Projection Method(Journal of 相似文献