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981.
鲕粒作为碳酸盐岩中非常重要的指相颗粒,其研究主要集中在成因上面,而成岩作用研究较少。北京西山地区下苇甸剖面寒武系张夏组发育大套鲕粒灰岩,通过对该剖面野外实测、薄片观察、XRD测试等手段,结合有机碳、热解等地化参数,对鲕粒的硅化机制及其硅质来源做了系统的研究。结果表明,鲕粒溶蚀再沉淀或者新生变形作用造成鲕粒边缘有机质富集,有机质演化释放的有机酸是硅质沉淀的主要因素,硅质来源主要为陆源输入和黏土矿物的转化。由于有机质主要富集在鲕粒边缘,形成有机质膜,从而造成硅质的沉淀主要沿鲕粒边缘发生,形成鲕粒边缘特有的硅化套,这种结果也从侧面反映了微生物在原始鲕粒形成中发挥了重要作用。 相似文献
982.
Yue‐Heng Yang Fu‐Yuan Wu Qiu‐Li Li Yamirka Rojas‐Agramonte Jin‐Hui Yang Yang Li Qian Ma Lie‐Wen Xie Chao Huang Hong‐Rui Fan Zi‐Fu Zhao Cheng Xu 《Geostandards and Geoanalytical Research》2019,43(4):543-565
Bastnäsite is the end member of a large group of carbonate–fluoride minerals with the common formula (REE) CO3F·CaCO3. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier‐crystallised minerals, in situ analysis is considered the most suitable method to measure its U‐Th‐Pb and Sr‐Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi‐collector) inductively coupled plasma‐mass spectrometry of forty‐six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in‐house bastnäsite reference material (K‐9) demonstrated that precise and accurate U‐Th‐Pb ages could be obtained after common Pb correction. Moreover, the Th‐Pb age with its high precision is preferable to the U‐Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research. 相似文献
983.
Jin Li Suo‐han Tang Xiang‐kun Zhu Zhi‐hong Li Shi‐Zhen Li Bin Yan Yue Wang Jian Sun Yao Shi Aiguo Dong Nick S. Belshaw Xingchao Zhang Sheng‐ao Liu Ji‐hua Liu Deli Wang Shao‐yong Jiang KeJun Hou Anthony S. Cohen 《Geostandards and Geoanalytical Research》2019,43(1):163-175
Iron, Cu and Zn stable isotope systems are applied in constraining a variety of geochemical and environmental processes. Secondary reference materials have been developed by the Institute of Geology, Chinese Academy of Geological Sciences (CAGS), in collaboration with other participating laboratories, comprising three solutions (CAGS‐Fe, CAGS‐Cu and CAGS‐Zn) and one basalt (CAGS‐Basalt). These materials exhibit sufficient homogeneity and stability for application in Fe, Cu and Zn isotopic ratio determinations. Reference values were determined by inter‐laboratory analytical comparisons involving up to eight participating laboratories employing MC‐ICP‐MS techniques, based on the unweighted means of submitted results. Isotopic compositions are reported in per mil notation, based on reference materials IRMM‐014 for Fe, NIST SRM 976 for Cu and IRMM‐3702 for Zn. Respective reference values of CAGS‐Fe, CAGS‐Cu and CAGS‐Zn solutions are as follows: δ56Fe = 0.83 ± 0.07 and δ57Fe = 1.20 ± 0.13, δ65Cu = 0.57 ± 0.06, and δ66Zn = ?0.79 ± 0.12 and δ68Zn = ?1.65 ± 0.24, respectively. Those of CAGS‐Basalt are δ56Fe = 0.15 ± 0.07, δ57Fe = 0.22 ± 0.10, δ65Cu = 0.12 ± 0.08, δ66Zn = 0.17 ± 0.13, and δ68Zn = 0.34 ± 0.26 (2s). 相似文献
984.
Acta Geotechnica - Parameter identification using Bayesian approach with Markov Chain Monte Carlo (MCMC) has been verified only for certain conventional simple constitutive models up to now. This... 相似文献
985.
986.
987.
我国西北地区21世纪季节气候变化情景分析 总被引:36,自引:2,他引:34
使用各国政府间气候变化专门委员会(IPCC)数据分发中心提供的7个全球海气耦合气候系统模式(CCC、CCSR、CSIRO、DKRZ、GFDL、HADL、NCAR)的模拟结果,对我国西北地区未来21世纪考虑温室气体增加(GG)和温室气体与硫化物气溶胶共同影响(GS)时,冬夏季的气候变化情景进行了分析.模式集成结果分析表明,我国西北地区的变暖趋势与全球、东亚和中国一致,但变暖幅度明显高于全球、东亚和中国.对未来100年各个季节线性倾向的分析表明,西北地区GG和GS时都是冬季变暖最大,可高达5~8℃/100a,且整个西北地区中新疆地区为最大变暖区.21世纪由于人类活动,西北地区最低温度和最高温度都将明显升高,其线性趋势可达4~6℃/100 a.由于全球气候模式对区域尺度的模拟存在较大的不确定性,未来需要作更多的深入研究. 相似文献
988.
利用空间分析和数理统计等方法探究了1984—2016年中国高尔夫球场数量时空演变、影响因素和扩散模式。结果表明:1)球场数量变化经历了低速增长期、稳定增长期、加速增长期和紧缩期;2)球场空间分布范围经历了扩张期和收缩期,向北、向西扩散较为明显;3)目前球场主要分布在经济发展水平较高且外向型经济突出的长三角、珠三角和环渤海地区;4)人均GDP、人口规模、区域开放程度、交通优势度、气候类型和土地资源稀缺性与球场空间分布均呈显著正相关,其中交通优势度相关系数最大;5)高尔夫球场空间扩散模式兼具接触性扩散和等级性扩散。 相似文献
989.
High‐T and low‐P metamorphism in the Xilingol Complex of central Inner Mongolia,China: An indicator of extension in a previous orogeny 下载免费PDF全文
The Xilingol Complex comprises biotite gneisses and amphibolite interlayers with extensive migmatization. Four representative samples were documented and found to record either two or three metamorphic stages. Phase modelling using thermocalc suggests that the observed assemblages represent the final stages that underwent cooling from temperature peaks, and are consistent with a fluid‐absent solidus in P–T pseudosections. Their P–T conditions are further constrained to be 5–6 kbar/680–725°C and 4–5 kbar/650–680°C for two garnet‐bearing gneiss samples, 4–5 kbar/660–730°C for a cordierite‐bearing gneiss sample, and 4–5 kbar/680–710°C for an amphibolite sample based on mineral composition isopleths, involving measured Mg content in biotite, anorthite in plagioclase, grossular and pyrope in garnet and Ti content in amphibole. The peak temperature conditions recovered are 760–790°C or >760°C at 5–6 kbar based on the composition isopleths of plagioclase, biotite, garnet and especially the comparison of melt contents between the calculated and observed. A pre‐peak heating process with slight decompression can be suggested for some samples on the basis of the core–rim increase in the plagioclase anorthite, and the stability of ilmenite. Zircon U–Pb dating using the LA‐ICP‐MS method provides systemic constraints on the metamorphic ages of the Xilingol Complex to be 348–305 Ma, interpreted to represent the post‐peak cooling stages. Moreover, metagabbroic dykes that intruded into the Xilingol Complex yield 317 ± 3 Ma from magmatic zircon, and are considered to have played a significant role for heat advection triggering the high‐T and low‐P metamorphism. Thus, the clockwise P–T paths involving pre‐peak heating, peak and post‐peak cooling recovered for the Xilingol Complex are consistent with an extensional setting in the Carboniferous that developed on a previous orogen in response to addition of mantle‐derived materials probably together with upwelling of the asthenospheric mantle. 相似文献
990.
Liu Zhankun Chen Jin Mao Xiancheng Tang Lei Yu Shuyan Deng Hao Wang Jinli Liu Yuqiao Li Shoulei Bayless Richard C. 《Natural Resources Research》2021,30(6):3987-4007
Natural Resources Research - The Xiadian orogenic deposit with?~?100 t of gold resources, located in the Jiaodong Peninsula, Eastern China, shows an economically attractive gold... 相似文献