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1.
赣中变质基底Nd模式年龄初步研究及基底地壳的形成时代   总被引:3,自引:2,他引:1  
本文研究了赣东南变质基底的Nd模式年龄(TDM=1360-2124Ma,平均为1755Ma),结合变质岩的Rb-Sr,Sm-Nd等时线年龄确认赣中地区存在前寒武纪地壳基底,推测本区还有一个尚未出露的古元古-新太古代的花岗质陆壳,这个陆壳正是元古代的陆源区  相似文献   

2.
赣中变质基度Nd模式年龄初步研究及基底地壳的形成时代   总被引:1,自引:0,他引:1  
胡恭任  章邦桐 《铀矿地质》1999,15(3):137-141
本文研究了赣东南变质基底的Nd模式年龄(TDM=1360-2124Ma,平均为1755Ma),结合变质岩的Rb-Sr,Sm-Nd等时线年龄确认赣中地区存在前寒武纪地壳基底,推测本区还有一个尚未出露的古元古-新太古代的花岗质陆壳,这个陆壳正是元古代的陆源区。  相似文献   

3.
华夏地块前加里东期变质基义匠年代构造格架   总被引:2,自引:0,他引:2  
华夏地块的前加里东期变质基底大致可划分为三大构造层,主体为古元古代的条旋回的结晶基底和新元古代-早古生代的褶皱基底,局部存在裂谷环境下的中元古代变质岩石。大量的单颗粒锆石年龄和Sm-Nd同位素测年资料显示出华夏地块的古元古代岩石形成于2400 ̄2000Ma,中元古代的岩石形成于1400 ̄1000Ma。而新古代-早古生代的地层大致形成于740 ̄430Ma。中条运动是华夏地块一次重要的造壳运动,奠基了  相似文献   

4.
扬子地块东南缘沉积岩的Nd同位素研究   总被引:16,自引:1,他引:15  
周泰禧  徐祥 《沉积学报》1995,13(3):39-45
扬子地块东南缘上溪群分布区及其周边沉积岩的Nd同位素研究结果,支持存在一条苏浙皖古生代裂陷槽(或江南深断裂)的观点。上溪群以北直至长江边所分布的震旦系-古生代的盖层沉积岩,其Nd模式年龄有两组,表明物源区不同。裂陷槽以北,沉积岩的物源区为Nd模式年龄约2.0~2.1Ga的扬子物源区;以南的沉积岩表现出明显的幔源物质混染,显示出元古代岩浆活动的影响,而上溪群分布区以南直到江绍断裂附近主要表现上溪物源区的影响,华夏地块古老基底岩石则无显著贡献。  相似文献   

5.
藏北鱼鳞山超钾质火山岩为一中等规模的熔岩被, 可分为三期。前两期主要为霞石黝方白榴石响岩、霞石白榴斑岩等, 后期主要为方钠石霓石粗面岩、霓霞粗面岩等。时代为18~30 Ma。本区超钾质岩浆 Si O2 强烈不饱和、强碱性、高度富集 L R E E及 L I L E、放射成因 Sr、 Pb 及非放射成因 Nd 同位素 (86 Sr/87 Sr= 0708766~0709162, 206 Pb/204 Pb= 18882888~ 19104751, 207 Pb/204 Pb= 15642037 ~ 15828458, 208 Pb/204 Pb= 39138921 ~ 39686835 及143 Nd/144 Nd= 0512116 ~0512342),其上述特征指示岩浆源区为受到地壳物质强烈交代的富集 E M I I型地幔。藏北拉嘎拉钠质碱性橄榄玄武岩为高原面上的剥蚀残丘, 时代为60 Ma。其岩石学、 R E E、微量元素及 Sr Nd Pb 同位素指示了岩浆源区为受到洋壳俯冲物质交代的轻度富集地幔。本研究结果指示, 羌塘高原南部富集地幔的形成可能是受到印度板块俯冲的影响。  相似文献   

6.
扬子地块南缘晚古生代洋壳存在的Nd同位素证据   总被引:7,自引:0,他引:7  
总结我国扬子地块南缘新元古代—早中生代沉积岩目前已发表的Nd同位素资料发现,这些沉积岩具有随时间变化而其Nd同位素组成发生漂移的现象。在绝大多数时间里,它们具有2000Ma左右的Nd模式年龄,但在1000~700Ma的新元古代和<400Ma的晚古生代—早中生代时间段中,Nd同位素模式年龄急剧降低,反映在此时间段内,新生地幔物质已经进入沉积物的物源区。1000~700Ma期间的Nd同位素变化归因于晋宁期的碰撞造山作用而晚古生代-早中生代沉积岩的Nd同位素变异起因于海盆发育阶段洋壳的出现。即扬子地块南缘在晚古生代—早中生代期间曾经存在过洋壳,且该洋盆可能是古特提斯大洋分支的一部分。  相似文献   

7.
山东蓬莱,临朐新生代碱性玄武岩的钕,锶同位素组成   总被引:1,自引:0,他引:1  
支霞臣  张宗清 《地质论评》1994,40(6):526-533
本文报道了鲁东和鲁西新生代碱性玄武岩13个样品的Nd,Sr同位素组成,143Nd/144Nd=0.512967-0.512744,87Sr/86Sr=0.70349-0.70450。它们在地质剖面上呈现规律性变化,可能与其地幔源区同位素组成的层状分带有关。鲁西地幔源区具有较鲁东更加亏损的组份。两地地幔源区在演化中都曾发生过地幔交代(或富集)作用,根据玄武岩Nd同位素模式年龄估计地幔交代作用发生的时  相似文献   

8.
华北地台前寒武纪变质基底的Sm-Nd同位素地质信息   总被引:6,自引:0,他引:6  
华北前寒武纪变质基底的Sm-Nd同位素资料,主要来自冀东、辽东、内蒙古中部,五台-太行、河南和鲁西等地早前寒武纪以基性岩为主的表壳岩和深成酸性侵入体,也有少量副变质岩的分析结果。已搜集的华北地台前寒武纪变质基底的304个Sm-Nd分析资料表明,除同位素年龄信息外,作为壳-幔演化示踪剂,给出了岩石圈早期演化的重要信息:除已由U-pb法证实的冀东曹庄、辽东鞍山有≥3.8Ga的地壳残留外,Sm-Nd资料还暗示吕粱和登封一带存在>3.5Ga的古老地壳。在华北地台上,除>3.5Ga的早期壳-幔分离事件外,3.2~3.6Ga,2.6~3.0Ga和2.0~2.2Ga分别为三次造壳的高峰时间。来自华北不同地区的Sm-Nd资料还表明,在3.0Ga以前即存在一个规模较大的古老地壳,加之晚太古的造壳规模,太古宙地壳规模之宏大已与现代地壳相近似。除壳-幔分离的造壳事件外,华北地台早前寒武纪地壳活化再造十分强烈。活化再造形成的酸性侵入体的Sm-Nd同位素资料显示T_(DM)=2.6~2.8Ga是活化再造的最高峰时期。  相似文献   

9.
赣东北蛇绿岩的离子探针锆石U-Pb年龄及其构造意义   总被引:50,自引:0,他引:50  
离子探针锆石U-Pb年龄分析结果表明,赣东北蛇绿岩套的高度分异岩浆的结晶年龄为968±23Ma。重新计算的蛇绿岩Sm-Nd等时线年龄955±44Ma,与锆石U-Pb年龄在误差范围内一致。15个样品的εNd(T)值(T=970Ma)为+4.3-+6.7,表明蛇绿岩来源于强亏损地幔源。少数样品的Sm-Nd体系可能受到后期变质、变形或蚀变作用的影响。结合已发表的40Ar-39Ar年龄资料,可以初步确定赣东北晚元古代碰撞带发育的时限为0.97-0.80Ga。  相似文献   

10.
六合—仪征第三纪碱性玄武岩的钕—锶同位素组成   总被引:4,自引:2,他引:4  
支霞臣  张宗清 《岩石学报》1994,10(4):382-389
本文报道了六合-仪征碱性玄武岩分布区11个样品的同位素组成,143Nd/144Nd为0.512849~0.512993,87Sr/86Sr为0.70336~0.70404,类似于大洋玄武岩同位素体系中的PREMA地幔端元.玄武岩源区同位素和微量元素的解耦特征表明地幔源区演化的多阶段性。  相似文献   

11.
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.
Robert L. Linnen   《Lithos》2005,80(1-4):267-280
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   

13.
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   

14.
Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ1 roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).  相似文献   

15.
《地学前缘(英文版)》2014,(3):I0001-I0003
正1 AIM AND SCOPE GEOSCIENCE FRONTIERS(GSF) is a bi-monthly international journal that publishes in English high quality original research articles and timely reviews in interdisciplinary fields of Earth and Planetary Sciences.GSF aims to bridge innovative,provocative and challenging concepts and models related to various fields of research including petrology and geochemistry in understanding lithospheric architecture  相似文献   

16.
正1 Introduction In the present paper,MgCl2·6H2O,FeCl3·6H2O,and CeCl3·6H2O were used as raw materials in the precipitationhydrothermal method to synthesize MgF eC e hydrotalcite.The effects of the Fe:Ce molar ratio on the composition,crystal structure,and thermal stability of hydrotalcite are examined.Energy-dispersive X-ray spectroscopy(EDS),X-  相似文献   

17.
正20141430 Chen Ji(Key Laboratory of Petroleum Resources,Chinese Academy of Sciences,Lanzhou 730000,China);Shi Ji’an Sedimentary Facies and Models for the Palaeogene-Neogene Deposits on the Northern Margin of the Qaidam Basin,Qinghai Province(Sedimentary Geology and Tethyan Geology,ISSN1009-3850,CN51-1593/P,33(3),2013,p.16-26,14 illus.,16 refs.)  相似文献   

18.
SEISMIC GEOLOGY     
正20141967An Zhanghui(Lanzhou Base of Institute of Earthquake Prediction,CEA,Lanzhou 730000,China);Du Xuebin Study onthe Geo-Electric Field Variation of Sichuan Lushan MS7.0and Wenchuan MS8.0Earthquake(Chinese Journal of Geophysics,ISSN0001-5733,CN11-2074/P,56(11),  相似文献   

19.
GEOCHEMISTRY     
正20141357 Guo Tao(School of Mathematics and Science,Shijiazhuang University of Economics,Shijiazhuang 050031,China);Hu Jiawen Assessment on the New Pressure-Volume-Temperature(PVT) Data of Supercritical Water(Geological Journal of China Universities,ISSN1006-7493,CN32-1440/P,19(3),2013,p.447-455,9 illus.,3 tables,32 refs.)Key words:supercritical fluids  相似文献   

20.
正20141074Bao Xijie(Research Institute of Exploration and Development,Daqing Oilfield Company,PetroChina,Daqing 163712,China)Gather Optimal Processing and Application Effect of Prestack AVA Instantaneous Inversion  相似文献   

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