银河系化学元素的丰度特征和合成图像(I):星际介质中轻元素丰度的观测及其特征     

侯金良 《天文学进展》1997,(4)

给出并解释了星际介质中轻元素D，3He，4He和Li的最新观测数据．星际介质中轻元素的丰度观测结果可以用来检验标准大爆炸核合成理论，因此对这些元素的丰度研究具有重要的天体物理意义．到目前为止，轻元素丰度的观测结果基本上支持开放宇宙的观点．根据最新的观测结果，在本地星际介质中D丰度可能存在小尺度不均匀性，而对类星体吸收云的观测表明不同观测者所获得的原初D丰度结果最大差别可达一个量级．如果观测是可靠的，那么在目前的标准大爆炸核合成理论和星系化学演化模型框架下还不能解释这种结果．另外种种迹象表明太阳系丰度可能不代表45亿年前本地星际介质的丰度．  相似文献   

我国土壤中结合态硒的含量和分布规律   总被引：18，自引：3，他引：15  

侯少范  王五一 《地理研究》1990,9(4):17-25

本文提出并建立了Jackson法系统分离土壤中不同形态硒的实验程序,研究了我国几种土壤表层(0—20cm)中硒的结合形态及其地理分布规律,并对植物可利用性作了评价。  相似文献   

河流相油气储层的井震结合相控随机建模约束方法   总被引：14，自引：4，他引：10  

于兴河  李胜利  赵舒  陈建阳  侯国伟 《地学前缘》2008,15(4):33-41

河流相油气储层的研究传统上多是只依据井点资料,先在井上进行沉积相的划分,而后进行剖面相的分析,最后再结合平面沉积参数等值线图编制平面相图,这样往往会造成"见砂画河,吾跟勘探走"的局面,这种平面相图在井间可能存在着较大的误差。然而,平面相图的正确与否直接影响着储层建模中相控的结果。为此作者提出了一种井震结合进行沉积相图编制的新方法,即"以河找砂,指导勘探行"的思路,并在此基础上进行分层次地相控约束随机建模。同时提出相控建模的三个基本的约束条件,即首先要保证随机建模模型的"相序"符合地质规律;其次要保证建模实现的微相分布统计概率与单井沉积微相数据离散化至三维网格后的统计概率相一致;第三要确保三维数据中每种微相的变差函数特征与定量地质知识库一致。因而,从沉积形成与演化的成因角度来指导沉积储层随机建模过程,应用多参数协同、分层次约束的方法,以河道的平面展布和垂向演化来控制建模的结果,使其更逼近地下地质的真实。  相似文献   

Geochemical characteristics and origin of gases from the Upper,Lower Paleozoic and the Mesozoic reservoirs in the Ordos Basin,China     

AnPing Hu  Jian Li  WenZheng Zhang  ZhiSheng Li  Lu Hou  QuanYou Liu 《中国科学D辑(英文版)》2008,51(1):183-194

The Ordos Basin, the second largest sedimentary basin in China, contains the broad distribution of natural gas types. So far, several giant gas fields have been discovered in the Upper and Lower Paleozoic in this basin, each having over 1000×10⁸m³ of proven gas reserves, and several gas pools have also been discovered in the Mesozoic. This paper collected the data of natural gases and elucidated the geochemical characteristics of gases from different reservoirs, and then discussed their origin. For hydrocarbons preserved in the Upper Paleozoic, the elevated δ ¹³C values of methane, ethane and propane indicate that the gases would be mainly coal-formed gases; the singular reversal in the stable carbon isotopes of gaseous alkanes suggests the mixed gases from humic sources with different maturity. In the Lower Paleozoic, the δ ¹³C₁ values are mostly similar with those in the Upper Paleozoic, but the δ ¹³C₂ and δ ¹³C₃ values are slightly lighter, suggesting that the gases would be mixing of coal-type gases as a main member and oil-type gases. There are multiple reversals in carbon isotopes for gaseous alkanes, especially abnormal reversal for methane and ethane (i.e. δ ¹³C₁>δ ¹³C₂), inferring that gases would be mixed between high-mature coal-formed gases and oil-type gases. In the Mesozoic, the δ ¹³C values for gaseous alkanes are enriched in ¹²C, indicating that the gases are mainly derived from sapropelic sources; the carbon isotopic reversal for propane and butane in the Mesozoic is caused by microbial oxidation and mixing of gases from sapropelic sources with different maturity. In contrast to the Upper Paleozoic gases, the Mesozoic gases are characterized by heavier carbon isotopes of iso-butane than normal butane, which may be caused by gases generated from different kerogen types. Finally, according to δ ¹³C₁-R ₀ relationship and extremely low total organic carbon contents, the Low Paleozoic gases would not be generated from the Ordovician source as a main gas source, bycontrast, the Upper Paleozoic source as a main gas source is contributed to the Lower Paleozoic gases.  相似文献   

A late-glacial transition from Picea glauca to Picea mariana in southern New England     

Matts Lindbladh  W. Wyatt Oswald  David R. Foster  Edward K. Faison  Juzhi Hou  Yongsong Huang 《Quaternary Research》2007,67(3):502-508

Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at  14,500–14,000 cal yr BP, followed by a transition to Picea mariana between  14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO₂ levels.  相似文献   

西安市两次突发暴雨成因分析   总被引：5，自引：1，他引：5  

张弘  梁生俊  侯建忠 《气象》2006,32(5):80-86

利用常规探空资料、地面加密观测资料以及卫星云图等，对发生在西安市的两次突发暴雨进行了诊断分析。结果表明：暴雨是台风北侧低空东风急流与中纬度西风带低值系统共同作用的结果；台风低压北侧的气旋性环流在低空形成的偏东风急流带是此类暴雨的主要水汽通道和能量通道；暖区内中β尺度对流系统（MβCS）的活跃直接导致了突发暴雨的生成和维持。  相似文献   

Numerical modeling of geothermal groundwater flow in karst aquifer system in eastern Weibei,Shaanxi Province,China     

Li Ming  Li GuoMin  Yang Liao  Dang XueYa  Zhao ChunHu  Hou GuangCai  Zhang MaoSheng 《中国科学D辑(英文版)》2007,50(1):36-41

The quantitative assessment of geothermal water resources is important to the exploitation and utilization of geothermal resources. In the geothermal water systems the density of groundwater changes with the temperature, therefore the variations in hydraulic heads and temperatures are very complicated. A three-dimensional density-dependent model coupling the groundwater flow and heat transport is established and used to simulate the geothermal water flow in the karst aquifers in eastern Weibei, Shaanxi Province, China. The multilayered karst aquifer system in the study area is cut by some major faults which control the regional groundwater flow. In order to calibrate and simulate the effect of the major faults, each fault is discretized as a belt of elements with special hydrological parameters in the numerical model. The groundwater dating data are used to be integrated with the groundwater flow pattern and calibrate the model. Simulation results show that the calculated hydraulic heads and temperature fit with the observed data well.  相似文献   

中国地震台网与美国地震台网测定震级的对比(Ⅱ) #8209;面波震级   总被引：11，自引：2，他引：11       下载免费PDF全文

刘瑞丰  陈运泰  Peter Bormann  任枭  侯建民  邹立晔  杨辉 《地震学报》2006,28(1):1-7

采用正交回归方法， 利用中国地震局地球物理研究所（IGCEA）和美国地质调查局国家地震信息中心（USGS/NEIC）1983——2004年的观测资料，对这两个机构测定的面波震级进行了系统的比较，得到了中国地震台网与美国地震台网面波震级之间的关系式. 结果表明，由于使用的震级计算公式和观测仪器不同，IGCEA测定的面波震级总体上要比NEIC测定的结果偏高0.2级；对于3.5~4.5级的地震，IGCEA测定的震级比NEIC测定的震级偏高0.3级；对于5.0~6.5级的地震，IGCEA偏高0.2级；对于7.0级以上的地震，IGCEA偏高小于0.1级.   相似文献   

北京市人大办公楼的结构地震反应观测台阵研究     

王飞  胡平  王湘南  侯丽娟  阎婷 《地震地磁观测与研究》2006,27(2):68-73

概述了国内外强震动观测的研究现状和结构地震反应观测台阵的研究情况。并对北京市人大办公楼的结构地震反应观测台阵的研究实例作了分析,该观测台阵在没有强震的情况下,依然取得了有用的地震记录。文中对该台阵得到的两次地震记录分析、处理,结果的对比分析用于验证该结构反应观测台阵布设的合理性。最后阐述了该台阵布设的不足,针对不足给出几点结构反应观测台阵布设的合理建议,并展望了结构地震反应观测台阵布设研究的美好前景。  相似文献   

Nature, diversity of deposit types and metallogenic relations of South China   总被引：5，自引：10，他引：5  

Khin Zaw  Stephen G. Peters  Paul Cromie  Clive Burrett  Zengqian Hou 《Ore Geology Reviews》2007,31(1-4):3-47

The South China Region is rich in mineral resources and has a wide diversity of deposit types. The region has undergone multiple tectonic and magmatic events and related metallogenic processes throughout the earth history. These tectonic and metallogenic processes were responsible for the formation of the diverse styles of base and precious metal deposits in South China making it one of the resource-rich regions in the world. During the Proterozoic, the South China Craton was characterised by rifting of continental margin before eruption of submarine volcanics and development of platform carbonate rocks, and the formation of VHMS, stratabound copper and MVT deposits. The Phanerozoic metallogeny of South China was related to opening and closing of the Tethyan Ocean involving multiple orogenies by subduction, back-arc rifting, arc–continent collision and post-collisional extension during the Indosinian (Triassic), Yanshanian (Jurassic to Cretaceous) and Himalayan (Tertiary) Orogenies. The Late Palaeozoic was a productive metallogenic period for South China resulting from break-up and rifting of Gondwana. Significant stratabound base and precious metal deposits were formed during the Devonian and Carboniferous (e.g., Fankou and Dabaoshan deposits). These Late Palaeozoic SEDEX-style deposits have been often overprinted by skarn systems associated with Yanshanian magmatism (e.g., Chengmenshan, Dongguashan and Qixiashan). A number of Late Palaeozoic to Early Mesozoic VHMS deposits also developed in the Sanjiang fold belt in the western part of South China (e.g., Laochang and Gacun).South China has significant sedimentary rock-hosted Carlin-like deposits, which occur in the Devonian- to Triassic-aged accretionary wedge or rift basins at the margin of the South China Craton. They are present in a region at the junction of Yunnan, Guizhou, and Guangxi Provinces called the ‘Southern Golden Triangle’, and are also present in NW Sichuan, Gansu and Shaanxi, in an area known as the ‘Northern Golden Triangle’ of China. These deposits are mostly epigenetic hydrothermal micron-disseminated gold deposits with associated As, Hg, Sb + Tl mineralisation similar to Carlin-type deposits in USA. The important deposits in the Southern Golden Triangle are Jinfeng (Lannigou), Zimudang, Getang, Yata and Banqi in Guizhou Province, and the Jinya and Gaolong deposits in Guangxi District. The most important deposits in the Northern Golden Triangle are the Dongbeizhai and Qiaoqiaoshang deposits.Many porphyry-related polymetallic copper–lead–zinc and gold skarn deposits occur in South China. These deposits are related to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) magmatism associated with collision of the South China and North China Cratons and westward subduction of the Palaeo-Pacific Plate. Most of these deposits are distributed along the Lower to Middle Yangtze River metallogenic belt. The most significant deposits are Tonglushan, Jilongshan, Fengshandong, Shitouzui and Jiguanzui. Au–(Ag–Mo)-rich porphyry-related Cu–Fe skarn deposits are also present (Chengmenshan and Wushan in Jiangxi Province and Xinqiao, Mashan-Tianmashan, Shizishan and Huangshilaoshan in Anhui Province). The South China fold belt extending from Fujian to Zhejiang Provinces is characterised by well-developed Yanshanian intrusive to subvolcanic rocks associated with porphyry to epithermal type mineralisation and mesothermal vein deposits. The largest porphyry copper deposit in China, Dexing, occurs in Jiangxi Province and is hosted by Yanshanian granodiorite. The high-sulphidation epithermal system occurs at the Zijinshan district in Fujian Province and epithermal to mesothermal vein-type deposits are also found in the Zhejiang Province (e.g., Zhilingtou). Part of Shandong Province is located at the northern margin of the South China Craton and the province has unique world class granite-hosted orogenic gold deposits. Occurrences of Pt–Pd–Ni–Cu–Co are found in Permian-aged Emeishan continental flood basalt (ECFB) in South China (Jinbaoshan and Baimazhai in Yunnan Province and Yangliuping in Sichuan Province). South China also has major vein-type tungsten–tin–bismuth–beryllium–sulphide and REE deposits associated with Yanshanian magmatism (e.g., Shizhuyuan and Xihuashan), important world class stratabound base metal–tin deposits (Dachang deposit), and the large antimony deposits (Xikuangshan and Woxi). During the Himalayan Orogeny, many giant deposits were formed in South China including the recently emerging Yulong and Gangdese porphyry copper belts in Tibet and the Ailaoshan orogenic gold deposits in Yunnan.  相似文献