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991.
992.
Songtao Li Yong Xia Jianzhong Liu Zhuojun Xie Qinping Tan Yimeng Zhao Minghua Meng Lijin Tan Rong Nie Zepeng Wang Guanghong Zhou Haiyan Guo 《Acta Geochimica》2019,(4):587-609
The newly discovered Baogudi gold district is located in the southwestern Guizhou Province,China,where there are numerous Carlin-type gold deposits.To better understand the geological and geochemical characteristics of the Baogudi gold district,we carried out petrographic observations,elemental analyses,and fluid inclusion and isotopic composition studies.We also compared the results with those of typical Carlin-type gold deposits in southwestern Guizhou.Three mineralization stages,namely,the sedimentation diagenesis,hydrothermal(main-ore and late-ore substages),and supergene stages,were identified based on field and petrographic observations.The main-ore and late-ore stages correspond to Au and Sb mineralization,respectively,which are similar to typical Carlin-type mineralization.The mass transfer associated with alteration and mineralization shows that a significant amount of Au,As,Sb,Hg,Tl,Mo,and S were added to mineralized rocks during the main-ore stage.Remarkably,arsenic,Sb,and S were added to the mineralized rocks during the late-ore stage.Element migration indicates that the sulfidation process was responsible for ore formation.Four types of fluid inclusions were identified in ore-related quartz and fluorite.The main-ore stage fluids are characterized by an H2O–NaCl–CO2–CH4±N2system,with medium to low temperatures(180–260℃)and low salinity(0–9.08%NaCl equivalent).The late-ore stage fluids featured H2O–NaCl±CO2±CH4,with low temperature(120–200℃)and low salinity(0–7.48%Na Cl equivalent).The temperature,salinity,and CO2and CH4concentrations of ore-forming fluids decreased from the main-ore stage to the late-ore stage.The calculated δ^13C,d D,and δ^18O values of the ore-forming fluids range from-14.3 to-7.0%,-76 to-55.7%,and 4.5–15.0%,respectively.Late-ore-stage stibnite had δ^34S values ranging from-0.6 to 1.9%.These stable isotopic compositions indicate that the ore-forming fluids originated mainly from deep magmatic hydrothermal fluids,with minor contributions from strata.Collectively,the Baogudi metallogenic district has geological and geochemical characteristics that are typical of Carlin-type gold deposits in southwest Guizhou.It is likely that the Baogudi gold district,together with other Carlin-type gold deposits in southwestern Guizhou,was formed in response to a single widespread metallogenic event. 相似文献
993.
采用PE-TGS2热重分析仪,对三种硼酸盐进行了TG-DTG曲线的测定,调节不同称样量和灵敏度,获得硼砂和四硼酸锂的细微脱水变化。 相似文献
994.
2016年门源6.4级地震为甘—青地区孤立地震事件,且震中附近地磁台站分布均匀,分析总结此次地震前后地磁谐波振幅比变化特征。结果显示:①地震发生前后,震中附近台站地磁谐波振幅比下降—转折—恢复的异常变化过程,持续时间约1—2年;②震中距较小的台站记录显示,地震基本发生在谐波振幅比曲线转折恢复的变化后期阶段,且异常持续时间长;震中距较大的台站记录显示,地震一般发生在曲线趋势性下降—转折阶段,且异常持续时间稍短;③地震发生后,距震中较近的台站1年内YZHx(NS)和YZHy(WE)方向所有或大部分周期基本趋于恢复状态,且同步变化;距震中较远的台站1年内YZHx(NS)和YZHy(WE)方向大部分周期未达到恢复状态,且不同步变化显著。 相似文献
995.
996.
997.
Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects 总被引:2,自引:0,他引:2
Chen Fahu Fu Bojie Xia Jun Wu Duo Wu Shaohong Zhang Yili Sun Hang Liu Yu Fang Xiaomin Qin Boqiang Li Xin Zhang Tingjun Liu Baoyuan Dong Zhibao Hou Shugui Tian Lide Xu Baiqing Dong Guanghui Zheng Jingyun Yang Wei Wang Xin Li Zaijun Wang Fei Hu Zhenbo Wang Jie Liu Jianbao Chen Jianhui Huang Wei Hou Juzhi Cai Qiufang Long Hao Jiang Ming Hu Yaxian Feng Xiaoming Mo Xingguo Yang Xiaoyan Zhang Dongju Wang Xiuhong Yin Yunhe Liu Xiaochen 《中国科学:地球科学(英文版)》2019,62(11):1665-1701
The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective. 相似文献
998.
F. S. Liu Shude Mao Z. G. Deng X. Y. Xia Z. L. Wen 《Monthly notices of the Royal Astronomical Society》2009,396(4):2003-2010
We search for ongoing major dry mergers in a well-selected sample of local brightest cluster galaxies (BCGs) from the C4 cluster catalogue. 18 out of 515 early-type BCGs with redshift between 0.03 and 0.12 are found to be in major dry mergers, which are selected as pairs (or triples) with r -band magnitude difference δ m r < 1.5 and projected separation r p < 30 kpc , and showing signatures of interaction in the form of significant asymmetry in residual images. We find that the fraction of BCGs in major dry mergers increases with the richness of the clusters, consistent with the fact that richer clusters usually have more massive (or luminous) BCGs. We estimate that present-day early-type BCGs may have experienced on average ∼0.6 ( t merge /0.3 Gyr)−1 major dry mergers and through this process increases their luminosity (mass) by 15 per cent ( t merge /0.3 Gyr)−1 ( f mass /0.5) on average since z = 0.7 , where t merge is the merging time-scale and f mass is the mean mass fraction of companion galaxies added to the central ones. We also find that major dry mergers do not seem to elevate radio activities in BCGs. Our study shows that major dry mergers involving BCGs in clusters of galaxies are not rare in the local Universe, and they are an important channel for the formation and evolution of BCGs. 相似文献
999.
传统观点认为交易型展览只有商品销售、国际贸易和市场营销功能。在互联网时代,这些功能在一定程度上受到电子商务的挑战。事实上,现代展览还可能具有政治、外交、教育、娱乐和创新等功能。对国内外相关文献进行分析,发现:有关交易型展览创新功能的研究文献主要涉及营销学和经济地理学,而不是旅游学。其中,营销学学者和经济地理学学者分别将展览视为临时市场和临时集群,并从多角度进行了研究。虽然营销学学者和经济地理学学者各自特别重视展览现场的信息沟通和知识转移对企业创新的影响,但都认为国际展览比国家和区域型展览具有更高的创新价值,并且参展者之间的关系建设是信息沟通和知识转移的重要前提。20世纪以来,两大学科学者(特别是国外学者)对交易型展览创新功能的研究日益增加。这些研究集中于解释展览的创新功能和探索展览创新功能发挥的机制。对主要研究成果从营销学和经济地理学两个角度按出版时间顺序进行了回顾,根据研究者的研究对象和建议提出了未来研究的四个主要方向:(1)重视展览类型对创新类型或阶段的影响;(2)展览溢出效应对企业创新的负面效应;(3)展览与其他会展活动的协同创新机制;(4)展览对城市产业和社会创新的贡献。 相似文献
1000.
A full-length lily-type lectin(Sm LTL) was identified from turbot(Scophthalmus maximus) in this study. By searching database for protein identification and function prediction, Sm LTL were confirmed. The full-length c DNA of Sm LTL is composed of 569 bp and contains a 339 bp ORF that encodes 112 amino acid residues. The Sm LTL peptide is characterized by a specific β-prism architecture and contains three mannose binding sites in a three-fold internal repeat between amino acids 30–99; two of the repeats share the classical mannose binding domain(Qx Dx Nx Vx Y) while the third binding site was similar to other fish-specific binding motifs(Tx Tx Gx Rx V). The primary, secondary, and tertiary structures of Sm LTL were predicted and analyzed, indicating that the S m LTL protein was hydrophilic, contained 5.36% α-helices, 39.29% extended strands, 16.07% β-folds, and 39.29% random coils, and three β-folds. Quantitative realtime polymerase chain reaction(qPCR) analysis revealed that the Sm LTL mRNA was abundantly expressed in skin, gill, and intestine. Low levels of Sm LTL expression were observed in other tissues. The expression of Sm LTL in gill, skin and intestine increased at m RNA level after stimulation of V ibrio anguillarum, our results suggest that Sm LTL serve as the first line of defence against microbial infections and play a pivotal role in the innate mucosal immune system. The current study indicates that Sm LTL is a member of the lilytype lectin family and the information reported here will provide an important foundation for future research on the role of this protein. 相似文献