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中国38亿年古陆壳锆石的成因矿物学研究 总被引：1，自引：0，他引：1
本文从锆石晶体形态，环带及晶体从核部于边缘的成分演化等特点，论述了中国最老（３８亿年）两个锆石样品的岩浆成因属性，并发现它们的母岩在成因上存在差异，鞍山花岗靡棱岩是地幔或地幔来源为主的花岗质岩石，而冀东铬云母夕线石英岩中锆石的母岩则属壳源或壳幔混合型花风岩石，这些差别表明３８亿年华北石陆壳岩石类型具有多样性。 相似文献
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锆石成因矿物学与锆石微区定年综述 总被引：54，自引：0，他引：54
锆石是岩浆岩、变质岩和石英脉型金矿床中的一种常见副矿物,对锆石成因类型的准确判断是正确理解锆石U-Pb年龄意义的关键.本文中笔者对不同成因类型锆石的判别标志及年龄意义进行系统的总结,并认为将锆石的阴极发光图像(CL)、背散射电子图像(BSE)、痕量元素组成及矿物包裹体特征的研究相结合是进行锆石成因鉴定的有效方法.近年来同位素质谱技术的发展使得人们对同一锆石颗粒内部不同成因类型的锆石晶域进行原位年龄测定成为可能.通过微区原位定年技术,能够给出有关寄主岩石的地质演化历史等重要信息,这可以为地质过程的精细年代学格架的建立提供有效的证据.来自不同类型岩石中的锆石可能经历了Pb的扩散丢失作用、晶格损伤导致的蜕晶化作用以及变质重结晶作用.这些过程对锆石计时的准确性和有效性带来了不同程度的影响.为了对测定锆石年龄的地质意义进行合理解释,在进行锆石U-Pb定年前,必需对锆石进行成因矿物学和矿物内部结构的深入研究,特别是阴极发光和背散射电子成像研究,通过内部结构特征确定锆石的成因类型和形成环境.笔者认为,组成单一的岩浆锆石是理想的U-Pb定年对象,变质重结晶锆石域常是重结晶锆石和继承晶质锆石的混合区,容易给出混合年龄,只有变质增生锆石和完全变质重结晶锆石才能给出准确的变质时代,而从继承锆石中鉴别出的热液锆石可以获得可靠的流体活动时间. 相似文献
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云南鸡街超基性碱性岩锆石类型及其年龄值意义 总被引：6，自引：3，他引：3
对云南禄丰鸡街超基性碱性岩(霞辉岩)岩石化学、辉石成分、锆石成因类型及其年龄值的意义等进行研究,文章最后对复合型锆石成因进行了论述,并建议将岩浆复合型锆石中的老核称为残留锆石,变质复合型锆石中的老核称为继承锆石。 相似文献
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冀东地区都山花岗岩基的成因探讨 总被引：1，自引：0，他引：1
以对冀东地区都山花岗岩基进行详细的野外地质调查，分析测试都山花岗岩的岩石化学成分及微量元素成分，测定都山花岗岩不同成因锆石的Ｕ－Ｐｂ年龄及对锆石进行群型分析为据，认为都山花岗岩基的源岩为晚太古代岩石，岩基的主体形成于元古代，在中生代经受了强烈的改造，并形成了部分新生岩浆。 相似文献
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近十年来对锆石研究已从早期的U-Pb放射性同位素定年和锆石同位素分析,发展到大量研究锆石的微量元素。锆石微量元素不仅可以作为锆石Ti温度计估算岩浆温度,也可以用来识别锆石及其母岩的岩石类型和成因,区分岩浆熔体或者流体控制的岩浆作用、变质作用、成矿作用等深部作用过程。文中在归纳总结岩浆锆石、变质锆石、热液锆石、碎屑锆石等不同类型锆石的微量元素成分基础上,以青藏高原碰撞后超钾质岩石中产出的锆石为例,系统介绍了超钾质岩石中各类锆石的结构、年龄和微量元素特征,并应用于解释超钾质岩石成因、岩浆源区成分、岩浆演化和上部地壳物质的混染、下地壳加厚和高原隆升之间的关系。 相似文献
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秦岭富水杂岩的变辉长岩中斜锆石与锆石U-Pb同位素年龄的差异及其地质意义 总被引：4，自引：0，他引：4
秦岭富水杂岩体的一些变辉长岩含有粒度较大，U、Pb含量较高的斜锆石和锆石，是U-Pb同位素测年的极好矿物。本文对秦岭富水杂岩的中粗粒角闪黑云辉长岩中的斜错石和错石分别进行了SHRIMP法和TIMS法U-Pb同位素年龄测定，获得斜锆石和锆石的U-Pb同位素年龄分别为501.4±1.2 Ma和480.0±3.4 Ma，二者相差约20 Ma；对该岩石中的斜锆石和锆石的关系及锆石的成因进行了初步研究，认为斜锆石的U-Pb同位素年龄应可解释为秦岭富水杂岩中基性岩石的形成时代，而锆石的成因比较复杂，对其U-Pb同位素年龄地质意义的合理解释需作进一步的研究。 相似文献
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《吉林大学学报(地球科学版)》2015,(Z1)
地球古老矿物和岩石是记录其早期形成和演化的最重要载体,但是由于板块运动、地表风化等后期地质作用的改造,地球上残存的古老岩石非常稀有,目前已知出露有古老岩石的地区仅有四处。位于华北克拉通东部的辽宁鞍山是古老岩石产地之一,出露有始太古代花岗质岩石。自1992年Liu等(1992)在该地区的石英岩中发现3.8 Ga的碎屑锆石以来,鞍山地区就引起了学者们的广泛关注。万渝生等(2009)随后在奥长花岗质岩石中找到了3.8 Ga的锆石,并认为该岩石就是3.8 Ga的岩石。但是,Wu等(2008)却认为这些3.8 Ga的锆石很可能是捕获锆石,因而鞍山地区并不存在3.8 Ga的岩石。产生争议的原因并不是3.8 Ga锆石的年龄值,而是这些锆石的成因,到底是捕获锆石,还是岩浆原位结晶的锆石。因为前人均使用破碎岩石分选锆石的方法进行研究,使得锆石产状信息丢失,从而无从判断其成因。为了解决这一问题,我们对鞍山地区的始太古代花岗质岩石样品开展了岩石学和原位锆石学工作。两块样品分别来自辽宁鞍山锅底山(C209)和深沟寺(F03),均为花岗片麻岩中的暗色奥长花岗质包体,其矿物组分别为Ab(30%~40%),Qz(50%~30%),Bi(15%),Ep(约13%),Kfs(约2%),副矿物Zrn(0.1%),Ap(0.1%)等。从11张岩石薄片中的411个锆石颗粒中,选取了19颗锆石进行了纳米离子探针微量元素图像扫描及U-Pb定年的测定。锆石常产于矿物颗粒间,少量单独产于石英或长石内,形态多数浑圆,常发育破裂,少量锆石含有包体,包体成分主要是斜长石、磷灰石和石英等。另外,锆石颗粒内部普遍发育蜕晶化作用,微量元素分析结果显示这些区域U、Y含量异常高,拉曼光谱显示该处已经完全蜕变为玻璃质。大多数锆石的U-Pb定年结果不谐和,谐和年龄通常位于U含量较低的区域,其年龄变化范围也比较大,为(3 269.3±59.6)Ma~(3 704.6±77.0)Ma。其中,F03-5-10锆石(3.5 Ga)具有清晰的岩浆韵律环带,说明该岩石的年龄至少不老于3.5 Ga。同时,由于锆石形态浑圆,推测可能是捕获锆石,则该岩石的年龄很可能是(3269.3±59.6)Ma左右。由于分析点较少,仍需要进一步工作验证这一结论。 相似文献
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对超基性—基性岩中锆石成因及其来源的解释直接关系到岩石成岩时代的准确厘定。江南造山带西段（包括桂北、黔东和湘西地区）的新元古代变质地层中分布有大量的超基性—基性火山岩和侵入岩,过去的研究认为它们都形成于新元古代,是四堡造山阶段和造山后裂谷阶段的产物。对前人近年发表相关岩石的锆石U- Pb测年数据的分析,结合笔者等对该地区多件基性岩中锆石的LA- ICP- MS测年结果,发现部分超基性—基性岩中普遍存在少量古生代,甚至中、新生代的年轻锆石。通过锆石形态及阴极发光特征分析,认为这些年轻锆石并不能一概用后期热液改造或挑样过程中混入来解释。本文抛砖引玉,旨在引起国内同行对超基性—基性岩真实成岩年龄解释的探讨。如果以往对这些超基性—基性岩中锆石成因及成岩时代的解释存在问题,将区域上多期岩浆热事件混为一谈,那么对江南造山带西段的构造演化历史需要重新解读。 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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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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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
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正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level 相似文献
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正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7), 相似文献
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正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci- 相似文献
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正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli- 相似文献
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正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.) 相似文献
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正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861 相似文献