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1.
大别山超高压变质带中“脉状”榴辉岩的锆石U-Pb年龄 总被引：2，自引：2，他引：0
榴辉岩广泛分布于大别山超高压变质带中,出露规模大小不等,成因类型复杂,围岩类型多样,不仅产于基性、超基性岩中,还产于片麻岩、大理岩、石英硬玉岩、变质花岗岩中。对大别山超高压变质带出露的两处"脉状"榴辉岩进行锆石U Pb年龄测定,分别获得上交点年龄(858±25)Ma和(845±150)Ma,下交点年龄(249±20)Ma和(237±13)Ma,表明其原岩形成时代为新元古代,印支期发生过高压—超高压变质作用,与大别山超高压变质带中其他类型的榴辉岩年龄基本一致。 相似文献
2.
沿中央造山带存在一条巨大的超高压变质带,其西起阿尔金-祁连,往东经秦岭,延至大别苏鲁,全长超过4000 km.柴北缘片麻岩中含柯石英锆石的SIMS离子探针原位微区U-Pb定年获得超高压变质年龄452±1 3.8 Ma,锆石的退变质年龄419±6.7 Ma.SHRIMP U-Pb定年获得秦岭含金刚石片麻岩中锆石的下交点年龄502±45 Ma,上交点年龄1545±100Ma,认为前者代表超高压变质年龄,后者为原岩岩浆锆石年龄;获得榴辉岩锆石的上交点年龄1381±82 Ma和下交点493±170 Ma,认为上交点代表榴辉岩原岩年龄,下交点代表超高压变质年龄;获得江苏东海县青龙山榴辉岩含柯石英等超高压矿物锆石的年龄为441±9 Ma,449±9 Ma,和442±9Ma,平均444±9 Ma,核部含斜长石+磷灰石锆石年龄为761±13 Ma,认为前者代表超高压变质年龄,后者代表榴辉岩原岩结晶年龄.认为中国中部沿中央造山带中存在两期超高压变质作用,第一期为加里东期,第二期为印支期,两期超高压变质事件在时空分布方面是不同的,加里东期超高压变质事件由西部阿尔金-柴北缘延至东部大别-苏鲁,印支期超高压变质事件没有在大别以西发现.认为中央造山带应是一个多期活动的造山带,较早形成罗德尼亚大陆的格林威尔造山运动可能留下了10亿年左右的构造岩浆事件记录,如中央造山带中大量10亿年左右的花岗岩及基性超基性岩类;罗德尼亚大陆之后第一次裂解作用可能发生在8亿年左右;其后早古生代加里东期的洋盆裂开,蛇绿岩和超高压变质岩石的大量出现是一次十分强烈的板块构造事件,从东到西,沿中央造山带均有分布;加里东期造山事件之后印支期沿该造山带又有一次大的板块裂解和俯冲碰撞作用,表现在勉略蛇绿岩洋壳及大别-苏鲁印支期超高压变质带的存在.中央造山带保留和记录了多期裂解、会聚事件,通过对其解剖,不仅可以认识中国大地构造格局和演化,并由此理解全球的大陆漂移、一系列大裂解和大会聚等重大地质事件. 相似文献
3.
安徽碧溪岭岩体的锆石U-Pb年龄为2774±24Ma。它显示大别山的含柯石英榴辉岩可能形成于晚太古代。榴辉岩多硅白云母的Ar-Ar等时线年龄(662±13Ma)也同样限定其退变质作用的上界年龄在寒武纪。同位素年代学结果与该类榴辉岩严格产出在由大别群组成的太古宙地块中的地质特征一致。我们相信,大别山含柯石英榴辉岩变质地区可能是一个晚太古代的超高压变质带。大别山地区在中生代三叠纪时期处于南秦岭构造带的东延部分。大别群以及赋存其中的含柯石英榴辉岩共同遭受晚期的区域动力变质事件。作者分别测得斜长片麻岩白云母Ar-Ar等时线年龄为192.6±3.8Ma,榴辉岩中低角闪岩相普通角闪石Ar-Ar坪年龄230.7±4.6Ma。它们代表大别群片麻岩和榴辉岩两种原始变质岩的印支期改造年龄。 相似文献
4.
胶东地块东部变质岩锆石U-Pb定年和氧同位素研究 总被引：18，自引：10，他引：18
对胶东地块东部高压-超高压变质岩作了系统的锆石U-Ph定年和矿物氧同位素分析,结果对这些变质岩的原岩性质提供了制约。研究得到:(1)区域花岗片麻岩及岩浆锆石普遍不同程度地亏损~(18)O,3个片庥岩样品中岩浆核锆石U-Pb年龄分别为723±36Ma、738±17Ma和744±63Ma,低δ~(18)O值(-0.42～4.14‰)岩浆核锆石说明其原岩为新元古代低δ~(18)O值岩浆岩,石英-石榴石氧同位素温度及少量印支期变质锆石的出现,指示片麻岩与榴辉岩曾经共同经历了印支期超高压变质作用;(2)花岗片麻岩中的榴辉岩原岩年龄有两种,一种是新元古代,其U-Ph年龄为806±79Ma。另一种是古元古代晚期,其 U-Pb年龄为1838±41Ma。这2个榴辉岩的超高压变质年龄分别为229±3Ma和242±21Ma。多数榴辉岩中的变质增生或变质重结晶锆石也具有低δ~(18)O值特征(0.22～3.4‰),指示在榴辉宕相变质作用之前,这些榴辉岩原岩为低δ~(18)O值蚀变岩或低δ~(18)O值基性岩浆岩;(3)大理岩中榴辉岩变质增生锆石δ~(18)O值高达15.9‰,U-Pb年龄为229±4Ma,指示在榴辉岩相变质作用之前,榴辉岩原岩与大理岩一样具有高δ~(18)O值;(4)斜长角闪岩的原岩U-Pb年龄为1719±18Ma,与同时期榴辉岩原岩一起构成扬子板块北缘新元古代岩浆侵位时的裂谷肩部围岩,在三叠纪大陆碰撞时同样受到变质改造。 相似文献
5.
大别山北部榴辉岩和英云闪长质片麻岩锆石U-Pb年龄及多期变质增生 总被引：50，自引：3，他引：47
大别山北部榴辉岩及英云闪长质片麻岩的锆石U-Pb年龄分析表明：北部榴辉岩相峰期变质时代为226～230Ma左右;北部塔儿河一带英云闪长质片麻岩经历过印支期变质事件;大别山北部与南部超高压岩石中一致的（226～230Ma）高压或超高压变质年龄表明,北部镁铁-超镁铁质岩带中部分岩石也曾作为扬子俯冲陆壳的一部分,在印支期发生过高压或超高压变质作用;本区锆石发生过两期变质增生事件,一是印支期高压或超高压变质,另一期是燕山期热变质事件;榴辉岩及英云闪长质片麻岩的原岩形成时代为晚元古代;锆石U-Pb年龄可用多期变质增生模型来解释。 相似文献
6.
大别山碧溪岭深色榴辉岩和片麻状花岗质岩石SHRIMP分析：晋宁期？… 总被引：64，自引：15，他引：49
本文报道大别山安徽省岳西县碧溪岭深色榴辉岩和片麻状花岗质岩石的锆石SHRIMP分析结果.深色榴辉岩的原岩为基性凝灰岩,锆石在岩石中主要产于石英、石榴子石和绿辉石内,为高压-超高压变质作用的产物,内部主体形成年龄约为757±7 Ma,代表高压-超高压榴辉岩相变质事件的时代;经受了后期流体改造的锆石边部年龄为223±3 Ma.在片麻状花岗质岩石中,发育韵律环带结构的深熔锆石形成于约727±15 Ma,受后期流体改造的锆石边部年龄为219±3 Ma.综合野外地质关系、区域地质背景和锆石的岩相学特征,笔者提出了碧溪岭榴辉岩相岩石高压-超高压变质作用发生于晋宁期,印支期仅代表一次后期流体改造事件的观点. 相似文献
7.
柴北缘鱼卡河榴辉岩围岩的变质时代及其地质意义 总被引：17，自引：1，他引：16
利用阴极发光和LA-ICP-MS原位分析方法,对柴北缘鱼卡河超高压榴辉岩的直接围岩——石榴石白云母角闪钠长片麻岩和含蓝晶石的石榴石云母片岩进行了详细的锆石微量元素和U-Th-Pb同位素分析。结果表明,石榴石白云母角闪钠长片麻岩中的锆石主体呈浑圆状形态,内部结构以扇状和冷杉树状为主,稀土总量和重稀土含量均较低,重稀土富集程度低,具明显正Eu异常,Th/U比值均小于0.1,指示其形成在与石榴石平衡共生而不含斜长石的变质条件下。而含蓝晶石的石榴石云母片岩中的锆石显示明显的核-边结构,核部显示碎屑锆石特征,边部为与石榴石共生的变质新生锆石。LA-ICP-MS原位定年获得两种围岩的峰期变质年龄分别为(431±3)Ma和(432±19)Ma。这两组年龄在误差范围内一致,而且与已获得的紧邻的两类超高压榴辉岩的变质年龄((436±3)Ma和(431±4)Ma)以及带内指示大陆深俯冲作用时代的都兰含柯石英副片麻岩锆石的柯石英微区年龄(424~432Ma)完全一致。参考这两类岩石与超高压榴辉岩的野外产状关系、含蓝晶石的石榴石云母片岩的原岩特征以及榴辉岩中超过变质年龄达300Ma的原岩残核的存在,共同表明,柴北缘鱼卡河超高压变质地体是典型的大陆深俯冲碰撞作用的产物,本区大陆深俯冲发生的时代为430~435Ma的早古生代。 相似文献
8.
青藏高原北缘早古生代板块构造演化和大陆深俯冲 总被引：16，自引：3，他引：16
青藏高原北缘北祁连山和柴达木盆地北缘分别发育有2类不同的高压和超高压变质带.北祁连山为典型的环太平洋型俯冲带,榴辉岩锆石的SHRIMP年龄为464 Ma±5 Ma.而柴北缘为典型的大陆俯冲型变质带,片麻岩锆石中的柯石英证明柴北缘是一超高压变质带.石榴橄榄岩中的超硅石榴子石和橄榄石中的钛铁矿等出溶反映其形成深度大于200 km.柴北缘榴辉岩的原岩具有MORB和OIB的特征,并与北祁连山榴辉岩的年龄相同,代表早古生代祁连洋俯冲变质的时代.而含柯石英片麻岩的锆石和石榴橄榄岩超高压变质年龄均为423 Ma,代表大陆地壳深俯冲发生的时间.北祁连山和柴北缘很可能是一个俯冲带从大洋俯冲到大陆碰撞的不同阶段的产物. 相似文献
9.
山东省日照市官山闪长玢岩锆石SHRIMP年龄:印支期岩浆热事件及其对超高压变质岩折返历史的限定 总被引：4，自引：0，他引：4
对苏鲁超高压变质带日照官山地区侵入于榴辉岩中的原生块状闪长玢岩进行了锆石SHRIMP年龄分析。结果显示,数据点构成的不一致线与一致线上交点年龄为(876±62)Ma,下交点年龄为(201±20)Ma。上交点年龄为残余锆石年龄,下交点年龄大致代表了闪长玢岩的形成时代。苏鲁超高压变质带中存在较广泛的印支期岩浆热事件。假定超高压变质作用发生于228Ma,推算出闪长玢岩侵位前超高压变质岩的折返速率大致为3.63mm/a,闪长玢岩侵位后超高压变质岩的折返(剥蚀)速率大致为0.03mm/a。 相似文献
10.
大别山东部含柯石英榴辉岩锆石U—Pb测年—多期超高压变质作用证据 总被引：6，自引：0，他引：6
大别造山带东段南，北大别两类不同产关的柯石英榴辉岩同位素地质年代学对比研究表明：１．石马辉岩超高压变质事件发生于４７１±２Ｍａ前，并受到海西期热事件；（２）碧溪岭与超镁铁质岩共生的榴辉岩是晚元古代北大别古岛岛弧超高压变质作用的产物，镁铁－超镁铁质堆晶岩系可能形成于９１±５６Ｍａ；（３）大别地区东部加里东期和印支期超高夺变质带并置，反映了造山带形成多期“开”“合”的复杂演化史。 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.
15.
Muriel Rocher Stéphane Baize Stéphane Jaillet Edward Marc Cushing Yannick Lozac&#x;h Francis Lemeille 《Comptes Rendus Geoscience》2003,335(8):701-708
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
16.
正20141520 Bo Ying(Key Laboratory of Metallogeny and Mineral Assessment,MLR,Beijing 100037,China);Liu Chenglin Saline Spring Hydrochemical Characteristics and Indicators for Potassium Exploration in Southwestern and Northern Tarim Basin,Xinjiang(Acta Geoscientica Sinica,ISSN1006-3021,CN11-3474/P,34(5),2013,p.594-602,5 illus.,3 tables,28 refs.) 相似文献
17.
正20141243Chen Ge(Hangzhou Research Institute of Petroleum Geology,PetroChina,Hangzhou 310023,China);Si Chunsong Study on Sedimentary Numerical Simulation Method of Fan Delta Sand Body(Journal of Geology, 相似文献
18.
正20142599Chen Sanming(Guangxi Key Laboratory of Concealed Deposits Exploration,Guilin University of Technology,Guilin541004,China);He Yuzhou Block Model and Reserves Estimation of Panzhihua Iron Deposit Based on 3D Geological Modeling(Journal of Guilin University of Technology,ISSN1674-9057,CN45-1375/N,33(4),2013,p.610-615,9illus.,1table,15refs.) 相似文献
19.
正20140594 Bai Daoyuan(Hunan Institute of Geology Survey,Changsha 410016,China);Zhong Xiang Faults in the Jingzhou Basin and Their Tectonic Settings(Geotectonica et Metallogenia,ISSN1001-1552,CN44-1595/P,37(2),2013,p.173-183,6illus.,59refs.)Key words:basin evolution,tectonic setting,South China In the Upper Paleozoic and Jurassic se- 相似文献
20.
正20141912Cao Hui(State Key Laboratory for Continental Tectonics and Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)Gravitational Collapse and Folding during Orogenesis:A Comparative Study of FIA Trends and Fold Axial Plane Traces(Geology in China,ISSN1000-3657,CN11-1167/P,40(6),2013,p.1818-1828,9illus.,35refs.,with 相似文献