国家科技基础条件平台
  • 你好,请
  • 登录
    • logotext
    Geological age of the JEHOL group in western liaoning,northeastern china [查看] GanLi、H.HIRANO、S.IWASAKI、S.TANAKA、K.AIDA
    Geodynamic significance of the A-type granites in the Sawuer region in west Junggar, Xinjiang Rock geochemistry and SHRIMP zircon age evidence [查看] ZHOUTaofa、YUANFeng、TANLugui、FANYu、YUEShucang
    Sawuer region is located in west Junggar, Jimunai County of Altay district and Hefeng County of Tacheng district, Xinjiang. The region is along the north margin of Kazakstan-Junggar plate. The intrusions (mainly acid) are widespread. Qiaqihai and Kuoyitasi intrusions are important in the region, with the characteristics of A-type granite. Fu rther investigations indicate that they belong to A2-type granite that formed in extension tectonic setting of post collision. The REE chon-drite-normalized patterns of the intrusions show LREE enrichment and theδEu values are lower. The Nd, Sr, Pb isotope compositions of the intrusions indicate a mantle source, while the low δ18O values resulted from the isotope exchange between intrusion and meteoric water. According to SHRIMP U-Pb age analysis results, the crystallization age of Qiaqihai intrusion is 290.7±9.3 Ma (1σ), and that of Kuoyitasi intrusion is 297.9 ± 4.6 Ma (1σ), corresponding to the beginning of early Permian. The A2-type granites indicate that the region was in the extension period of the post- collisional stage at the beginning of early Permian in the Sawuer region. The A-type granites in the Sawuer region in west Junggar discovered from this work is analogous to the A-type granites found in east Junggar of the Ulungur alkali granites belt. The c onfirmation of post-collisional A-type granites of early Permian in the Sawuer region provides new evidence for the regional vertical continental crust growth in early Per-mian. The former proposed Ulungur alkali granites belt can extend from east Ulungur through west Ulungur and to Zhaisang in Kazakstan westwards.
    Finding of Neoproterozoic (~775 Ma) magmatism recorded in metamorphic complexes from the North Qilian orogen Evidence from SHRIMP zircon U-Pb dating [查看] Chien-YuanTseng、Houng-YiYang、WANYusheng、LIUDunyi、Da-JenWen、Tzung-ChiLin、Kuo-AnTung
    SHRIMP U-Pb dating was carried out on zircons from the Niuxinshan gneissic granite and the Leigongshan gneissic tonalite in the North Qilian orogen, NW China. The results yield weighted aver-aged 206Pb/238U ages of 776±10 Ma and 774±23 Ma respectively. Igneous morphology, oscillatory zonings, and relatively high Th/U ratios for these zircons suggest magmatic origin. These ages are interpreted as timing of magma emplacement and thus repre-senting a Neoproterozoic (~775 Ma) magmatic event in the North Qilian area. It is suggested that this magmatism is probably related to breakup of the supercontinent Rodinia. This finding, together with the similar ages of 750 to 800 Ma reported for neighboring terranes of South-central Qilian and North Qaidam, is of significance to understanding of the Rodinia evolution in West China.
    Detrital Zircon of 4100 Ma in Quartzite in Burang,Tibet [查看] DUOJi、WENChunqi、FANXiaoping、GUOJianci1、NIZhiyao、LIXiaowen、SHIYuruoandWENQuan
    A detrital zircon aged 4.1 Ga is discovered by the SHRIMP U-Pb method in a quartzite in Burang County, western Tibet. This is presently the oldest single-grain detrit al zircon in China. The Th-U ratios of the two testing points of the >4.0 Ga zircon are between 0.76 and 0.86, indicating their magmatic origin. This discovery ha s offered an important age for inve stigating the geological evolution of the Qinghai-Tibet Plateau.
    Bashikaogong-Shimierbulake granitic complex, north Altun, NW China Geochemistry and zircon SHRIMP ages [查看] WUCailai、YAOSunzhi、ZENGLingsen、YANGJingsui、JosephL.Wooden、CHENSongyong1&FrankK.Mazdab
    The Bashikaogong-Shimierbulake granitoid complex is about 30 km long and 2 ―6 km wide, with an area of 140 km2, located at the north margin of the Bashikaogong Basin in the north Altun terrain. It intruded into schist, metapelite and metatuff of Precambrian ages. This granitoid complex consists of darkish quartz diorite, grey granite, pink granite and pegmatite. Geochemically, the quartz diorite has I-type granite affinity and belongs to Calc-alkaline sereies, and the other gran-ites have S-type affinity and to high-K calc-alkaline series. Zircon SHRIMP U-Pb dating shows that the quartz diorite has a bigger age than those of other granites, which is 4 81.6±5.6 Ma for quartz diorite, 437.0±3.0 Ma―433.1±3.4 Ma for grey granite and 443±11 Ma―434.6±1.6 Ma for pink granite, re-spectively. Combined with regional geology, we think that the quartz diorite formed in tectonic envi-ronment related to oceanic crust subduc tion and the granites in post-collision.
    滇川西部金沙江石炭纪蛇绿岩SHRIMP测年：古特提斯洋壳演化的同位素年代学制约 [查看] 简平、刘敦一、孙晓猛
    应用SHRIMP方法对滇西北2个花岗质岩基——白马雪山和鲁甸花岗岩进行同位素地质年代学研究。研究表明，白马雪山花岗闪长岩的侵位年龄为239±6Ma，鲁甸黑云母二长花岗岩为214±6Ma。这一研究为解决金沙江地区的碰撞造山事件的时代问题提供了同位素地质年代学依据.
    北京十三陵长城系常州沟组碎屑锆石SHRIM年龄：华北克拉通盖层物源区及最大沉积年龄的限定 [查看] 万渝生、张巧大、宋天锐
    华北克拉通中元古代长城系盖层广泛分布，其沉积时代和物质来源对于华北克拉通前寒武纪地壳演化研究具有重要意义。本文报道了北京十三陵地区华北克拉通长城系盖层碎屑沉积岩碎屑锆石年龄分布模式。样品为长城系下部常州沟组含长石石英砂岩（CHc-2）和石英砂岩（CHc-9）。碎屑锆石年龄主要分布在2.35~2.60Ga之间，靠上部层位（CHc-9）还有一定数量1.9~1.8Ga和2.1~2.3Ga碎屑锆石存在。研究表明，碎屑沉积物来自以约2.5Ga陆壳物质为主的华北克拉通物源区，1.9~1.8Ga为华北克拉通古元古代哥伦比亚超大陆陆-陆碰撞构造热事件响应的年龄，长城系盖层最大沉积年龄小于1.8Ga。
    蛇绿岩及蛇绿岩中浅色岩的SHRIMPU-Pb测年 [查看] 简平、刘敦一、张旗、张福勤、石玉若、施光海、张履桥、陶华
    文中简要评述了蛇绿岩的层状辉长岩,斜长岩和斜长花岗岩，以橄榄岩为主岩的花岗岩和蛇绿岩中的埃达克岩的锆石SHRIMP U-Pb年龄的地质意义。层状辉长岩（或堆晶层状辉长岩）通常起源于洋脊下的岩浆房，因而它的形成年龄代表洋壳形成的时代。斜长岩与层状辉长岩的时代相近或略晚。斜长花岗岩年龄的解释极其依赖锆石组成和地球化学证据。橄榄岩为主岩的花岗岩，可能记录蛇绿岩的侵位时代。蛇绿岩中的埃达克岩是消减洋壳在深部的部分熔融的产物。文中发表了新疆扎河坝蛇绿岩SHRIMP定年的中间成果，并简略地介绍了滇川西部金沙江和内蒙古图林凯等地的研究实例。根据层状辉长岩的测定结果，扎河坝蛇绿岩形成于（489±4）Ma，金沙江蛇绿岩形成于（328±8）Ma。内蒙古图林凯蛇绿岩中埃达克岩形成于（467±13）Ma~（429±7）Ma。块状辉长岩、斜长花岗岩和橄榄岩为主岩的花岗质岩石记录了蛇绿岩的复杂演化。新疆扎河坝蛇绿岩中的块状辉长岩中存在多组锆石年龄值。较老的一组为468~511Ma，与层状辉长岩和斜长岩相似，记录了蛇绿岩或洋壳的形成时代，但是，岩石中的大部分锆石年龄为396~419，加权平均年龄为（406±4）Ma，可能反映了一次部分熔融事件。滇川西部金沙江蛇绿岩中的斜长花岗岩的形成年龄为约300~285Ma，晚于层状辉长岩和斜长岩。这些岩石具高REE高总量，LREE富集，Sr初始值高，并含来自陆壳的继承锆石，说明在岩浆的形成过程中有陆壳的参加，因此，它们可能与洋壳俯冲消减有关。变质橄榄岩中的花岗岩脉的年龄（263±6）Ma，与呈岩株侵人蛇绿岩的花岗闪长岩的年龄一致。这一年龄远晚于层状辉长岩、斜长岩和斜长花岗岩，但早于区域上大量存在的印支期花岗岩，可能记录了蛇绿岩的侵位时代。
    中央碰撞造山带中两期超高压变质作用来自含柯石英锆石的定年证据 [查看] 杨经绥、刘福来、吴才来、万渝生、张建新、史仁灯、陈松永
    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，延至大别一苏鲁，全长超过4000km。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±13.8Ma，锆石的退变质年龄419±6.7Ma。SHRIMP U-Pb定年获得秦岭含金刚石片麻岩中锆石的下交点502±45Ma，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±82Ma和下交点493±170Ma，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±9Ma，449±9Ma，和442±9Ma，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一苏鲁，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一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。
    中国内蒙古锡林郭勒杂岩SHRIMP锆石U-Pb年代学及意义 [查看] 施光海、刘敦一、张福勤、简平、苗来成、石玉若、陶华
    锡林郭勒杂岩是中亚造山带内出露面积较大的强变形变质地质体，其形成时代与性质存在较大认识上的分歧。对锡林浩特东南锡林郭勒杂岩定名处黑云斜长片麻岩进行了岩相分析和SHRIMP锆石U-Pb年代学研究，其形成年龄下限由杂岩中碎屑岩浆锆石SHRIMP U-Pb年龄限定为437±3Ma，其形成上限由侵入于杂岩内的石榴石花岗岩SHRIMP锆石U-Pb年龄限定为316±3Ma.这表明该杂岩的沉积成岩年龄晚于奥陶纪-早志留纪，因此不是前寒武纪古老地质体。结合实际野外观察和室内岩石特征分析，该杂岩可能是一套经历强变形与变质作用的古生代弧前浊积岩建造。杂岩中碎屑锆石还给出分散的前寒武纪年龄，最老可达3.1Ga，这些锆石既可能来源于华北基底，也可能来源于南蒙微大陆，抑或暗示该区存在600-800Ma或更古老（3.1Ga）块体，表明其碎屑来源的复杂性。
    © BJSHRIMP 2013 - bjshrimp.cn