布谷马西钾盐矿区卜育矿段盐系地层沉积旋回划分     

栾元滇  田宁  刘东义  岳伟佳  王宏伟 《化工矿产地质》2020,42(3):225-230

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贵州漾头陡山沱组与留茶坡组界线凝灰岩的锆石U-Pb年龄及其地质意义          下载免费PDF全文

陈灿  冯庆来  甘正勤 《地球科学》2020,45(3):880-891

前寒武纪-寒武纪过渡时期是地质历史上最重要的转折期之一，对这一时期不同沉积相地层建立精确的对比标志，是理解寒武纪动物大爆发等一系列重大地质问题的关键.对贵州漾头剖面陡山沱组顶部和留茶坡组底部的两层凝灰岩中的锆石进行了LA-ICP-MS U-Pb年代学研究，分别获得了554.2±3.3 Ma和550.6±3.3 Ma的加权平均年龄，证明华南扬子地台深水相区留茶坡组开始沉积的时间约为550 Ma.扬子地台在埃迪卡拉纪-寒武纪过渡时期存在明显的台-盆沉积相分异，表明扬子地台在这一时期进入拉张的构造背景；因此，留茶坡组底部550.6±3.3 Ma的绝对年龄代表了扬子地台进入伸展构造背景和强烈海底热液活动开始的时间.另外，凝灰岩锆石微量元素特征显示，两层凝灰岩的源岩均属于花岗岩类，形成的大地构造背景属于岛弧环境或造山环境.   相似文献   

干热河谷优势灌木细根、粗根与叶片养分(C、N、P)含量及化学计量比     

刘颖  贺静雯  余杭  林勇明  王道杰 《山地学报》2020,38(5)

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Ab　Initio　Prediction　of　^29Si-NMR　Chemical　Shifts     

CHUShidong LIYingxia SONGNi GUANHuashi 《青岛海洋大学学报(英文版)》2002,1(1):63-65

The ability of several ab initio models to predict experimental 29Si-NMR chemical shift is examined. The shielding values of trimethylsilyl chloride (A), t-butyldimethylsilyl chloride (B) and allyltrimethylsilane (C) are calculated by GIAO, CSGT and IGAIM methods, using HF/6-31G^*, B3LYP/6-31G^* , HF/6-311 G^**, B3LYP/6-311 G^** and MPWlPW91/6-311 G^** models respectively. The 29Si chemical shifts calculated by GIAO method using HF/6-311 G^** model are highly in agreement with those obtained experimentally. All of the models above reproduce the trends of chemical shifts in all cases studied, suggesting that the models are of practical value.  相似文献   

金的矿化与深部岩浆作用的空—时关系及岩石化学标志     

К.  ИВ 田书文 《国外前寒武纪地质》1992,(2):73-82

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银盘恒星运动学和化学丰度与银河系结构     

侯金良  陈力  常瑞香  孙振娜 《天文研究与技术》2004,1(1):16-27

大样本的银盘恒星的运动学数据和元素丰度特征是研究银河系结构及演化，尤其是银盘形成和演化的2个重要探针。本文首先介绍了银河系的总体结构特征，然后较详细的综述了以上2个探针的重要性。对我国LAMOST项目在研究银河系结构方面，尤其是银盘的形成和演化方面的能力作了合理的分析。  相似文献   

台湾地层检讨(续)     

张丽旭 《地质论评》1948,13(Z3):291-310

所谓‘大寮层’者,以页岩与砂岩之交互层为主,厚约350公尺,在其上部,砂岩发育较佳,而在山下部则反是。砂岩往住带石灰质并含有化石,尤其在上部有富含Ditrupa sp之灰质的砂岩发现,所谓Ditrupa化石带是也。此外尚有下列之化石发现:  相似文献   

元古代海水稳定同位素组成发生过大的变化？     

Burd.  JW 李靠社 《国外地质与勘测》1992,(1):24-27

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印度阿萨姆——若开盆地东北部受海水影响的渐新世煤的化学特性评述     

《国外煤田地质》1997,(1):20-20

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The Geologic Time Scale and the Italian stratigraphic record     

DomenicoRio IsabellaPremoliSilva LucaCapraro 《《幕》》2003,26(3):259-263

The construction of the Geologic Time Scale (GTS) is a titanic scientific challenge that has been under way for two centuries and will require much dedicated effort in the future. Italy preserves a paramount stratigraphic record of Mesozoic and Cenozoic marine sediments that have been significant in the development of the modern GTS. The Italian stratigraphic record has been histori-cally important in introducing and defining the standard Chronostratigraphic Units (CUs) of the Neogene and Quaternary. Pelagic successions from Northern Apen-nines and Southern Alps have been used in the seventies for integrating the late Cretaceous-Paleogene Geomag-netic Polarity Time Scale (GPTS) with planktonic microfossil biostratieraohv and standard CUs. This was a major contribution to the construction of a new gener-ation of GTS based on integrated magnetobiochronol-ogy. The middle Miocene to early Pleistocene marinerecord from Sicily and southern Italy has been funda-mental for establishing the recently developed Astro-nomical Time Scale (ATS). In prospect, there are many potentials still to be exploited in the Italian marine stratigraphic record for implementing the GTS by defin-ing GSSPs of various CUs, improving magneto-biochronology and extending downwards the ATS.  相似文献