中国东部古生界沉积-改造型铁矿床地质及成生机制     

冯志文  夏卫华 《地球科学》1988,(6)

中国东部古生界沉积—改造型铁矿床含矿岩系基本上由细碎屑—碳酸盐岩组成,而且常与富铁白云岩共生。矿体产状多与围岩一致,呈沉积整合接触。矿床中普遍发育有后生“再造”型矿体,呈脉状叠加在层状矿体之上,有明显的穿层现象。 海解作用是沉积成矿的重要因素,再造成矿作用是在沉积富铁碳酸盐建造的基础上发生富铁碳酸盐矿物的重溶,铁质被搬运、迁移,最后在碱性或偏碱性围岩中重新沉淀出来。  相似文献   

永胜6.0级地震的破坏特征及分析   总被引：1，自引：2，他引：1  

施伟华  周光全  付正新  卢吉高  崔建文 《地震研究》2003,26(4):388-395

介绍了永胜6．0级地震震区的自然概况、震害分布及特征，分析了各种破坏产生的机理，提出了震区在恢复重建与规划发展时的建议以及各类建(构)筑物加强抗震的措施。  相似文献   

Sedimentary and Geochemical Characteristics of Sinian Cap Carbonates in the Upper Yangtze Region     

杨瑞东  王世杰  董丽敏  姜立君  张卫华  高慧 《中国地球化学学报》2003,22(4):320-329

A global-scale glaciation occurred at about 600 Ma ago. As a result, the Earth became the “Snowball Earth“. The glaciation came to the end abruptly when atmospheric carbon dioxide increased to such an extent as to be about 350 times the modem level because of subaerial volcanic degassing. The rapid termination of glaciation would have led to warming of the Snowball Earth and extreme greenhouse conditions would have been created. The transfer of atmospheric carbon dioxide to oceans would give rise to the rapid precipitation of calcium carbonate in warm surface seawaters, thus forming the cap carbonate rocks as observed worldwide today. Regionally persisting, thin layers of carbonate rocks directly and ubiquitously overlie Proterozoic glacial deposits almost on every continent, and are commonly referred to as cap carbonates. Their unusual litho- fabrics, stratigraphically abrupt basal and upper-level contacts and strongly negative carbonate isotopic signatures ( δ ^13Cearb. values range from -7.0‰ —0‰) suggest a chemical oceanographic origin, the details of which remain unknown. It is proposed that these enigmatic deposits are related to the destabilization of gaseous hydrate in terrestrial permafrost following rapid postglacial warming and flooding of widely exposed continental shelves and internal basins. The authors carried out studies on the geochemistry, sedimentology and palacontology of the Sinian cap carbonates in Guizhou and Hunan provinces, including the occurrence of cap carbonates of unusual fabrics, strongly negative carbon isotopic signatures, and a lot of bitumen nodules.From the results it is suggested that the cap carbonates were formed from solid methane seepage, and it is in agreement with Kennedy‘‘ s viewpoint (2001) that the cap carbonates resulted from the rapid precipitation of calcium carbonate in response to solid methane seepage.  相似文献   

Geochemical Characteristics of Volcanic Rocks of the Laochang Ag Polymetallic Deposit,Lancang,Yunnan Province,China     

刘友梅  杨蔚华  陈多福 《中国地球化学学报》2002,21(3):266-273

In terms of major element, trace element and REE geochemical characteristics ofvolcanic rocks in the area studied and by making use of the TiO2-K2O-P2O5,The-Hf-Ta and Zr-Nb-Y trianglar diagrams and the environmental discrimination diagrams of incompatible ele-ment distribution pattems,the authors have drawn some conclusions that are different from those by previous workers.It is concluded that volcanic rocks in the Laochang Ag polymetallic deposit at Lancang,Yunnan belong to continental within-plate alkali basalts, and that their geotectonic setting seems to be at the northeastern margin of East Gondwana Land.  相似文献   

Biotic recovery from the Late Devonian F-F mass extinction event in China   总被引：5，自引：5，他引：5  

廖卫华 《中国科学D辑(英文版)》2002,45(4):380-384

The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatoporoids, bryozoans, nearly all tentaculites, a few superfamilies of brachiopods, such as Atrypacea and Pentameracea and some important elements of goniatites, such as Manticoceras. The end-Frasnian was a phase of mass extinction. A large number of shelly benthos were killed by the F-F event. Early and middle Famennian was the survival interval. The marine faunas were very rare at that time. The late Famennian was the recovery interval. There appeared to have many new taxa in the Strunian stage. It lacked a radiation interval in Late Devonian Famennian because another event (the D-C mass extinction) happened at the Devonian-Carboniferous boundary. Several causes for the F-F mass extinction have been proposed by some geologists, which have been grouped into two broad types, terrestrial and extraterrestrial. The former is related to sea level changes, climate changes and anoxic water event. The latter is linked with some forms of meteorite impact. A large-scale eustatic change of sea level and black shales representing an anoxic environment has been invoked to explain one of the causes for the F-F mass extinction.  相似文献   

滚石在平台上的运动特征分析   总被引：6，自引：0，他引：6  

黄润秋  刘卫华 《地球科学进展》2008,23(5):517-523

危岩体;滚石;平台;运动距离;现场试验;滚动摩擦系数  相似文献   

一种土的非线性弹性本构模型参数的反演方法   总被引：2，自引：1，他引：1  

刘增荣  崔伟华  王鑫 《工程地质学报》2008,16(3):338-341

旨在提出一种土的非线性弹性本构模型参数反演的方法。以现今普遍实行的地基载荷试验为基础,依据遗传算法的组合优化理论,采用正演计算和遗传算法优化相结合的方式,建立了土层非线性弹性本构模型参数反演的方法;并依据某黄土场地地基载荷试验数据,实施了黄土土层非线性弹性本构模型参数反演的全过程。计算结果表明,所建立的方法可以实现土层非线性弹性本构模型中相互关联的多个参数的组合优化,并在对初始值要求较低的情况下,可以获得良好的参数反演精度。从而为土的变形特性分析和土与其中及相邻结构的共同作用分析,提供了较好的土体本构模型参数的确定方法。  相似文献   

UV-Vis spectrophotometric and XAFS studies of ferric chloride complexes in hyper-saline LiCl solutions at 25-90 °C     

Weihua Liu  Barbara Etschmann  Leone Spiccia  Brent McInnes 《Chemical Geology》2006,231(4):326-349

The speciation and thermodynamic properties of ferric chloride complexes in hydrothermal solutions and hypersaline brines are still poorly understood, despite the importance of this element as a micronutrient and ore-component. Available experimental data are limited to room temperature and relatively low chloride concentrations. This paper reports results of UV-Vis spectrophotometric and synchrotron XAFS experiments of ferric chloride complexes in chloride concentrations up to 15 m and at temperatures of 25-90 °C. Qualitative interpretation of the UV-Vis spectra shows that FeCl²⁺, FeCl₂⁺, FeCl_3(aq) and FeCl₄⁻ were present in the experimental solutions. As chloride concentrations increase, higher ligand number complexes become important with FeCl₄⁻ predominating in solutions containing more than 10 m at 25 °C. The predominance fields of FeCl_3(aq) and FeCl₄⁻ expand to lower Cl concentrations with increasing T. Both XANES and UV-Vis spectra reveal a major change in the geometry of the complex between FeCl₂⁺ and FeCl_3(aq). EXAFS data confirm that the number of chloride ligands increases with increasing chloride concentration and show that Fe³⁺, FeCl²⁺ and FeCl₂⁺ share an octahedral geometry. FeCl_3(aq) could be either tetrahedral or trigonal dipyramidal, while FeCl₄⁻ is expected to be tetrahedral. EXAFS data support a tetrahedral geometry for FeCl₄⁻, especially at 90 °C, but do not allow to distinguish between a tetrahedral or trigonal dipyramidal geometry for FeCl_3(aq) because of similar Fe-Cl distances. At room temperature, EXAFS data suggest that FeCl_3(aq) may be a mixture of octahedral and tetrahedral or trigonal dipyramidal forms.The room temperature formation constants for three ferric chloride complexes (FeCl₂⁺, FeCl_3(aq) and FeCl₄⁻) determined from the UV data are generally in good agreement with previous studies. Calculations based on the properties extrapolated to 300 °C show that hematite solubility is much higher than previously estimated, and that the high orders complexes FeCl_3(aq) and FeCl₄⁻ are important at high temperatures even in solutions with low chloride concentrations. The accuracy of these properties is limited by a poor understanding of activity-composition relationships in concentrated electrolytes, and by limitations in the available experimental techniques and extrapolation algorithms; however, the inclusion of higher order complexes in numerical models of ore transport and deposition allows for a more accurate qualitative prediction of Fe behaviour in hydrothermal and hypersaline systems.  相似文献   

腾冲全新世未来火山喷发灾害损失预测初探     

姜朝松  王锡财  非明伦  施伟华 《地震研究》2000,23(2):249-261

介绍腾冲全新世火山喷发灾害损失静态预测的方法、喷发灾害等级、预测范围划分、各类地面财富、火山喷发、经济损失及人员伤亡预测。地面财富包括房屋建筑、工矿企业、水库、电站、公路、桥梁、森林等 ,给出了预测结果  相似文献   

地理信息系统空间分析功能的应用   总被引：1，自引：0，他引：1  

石树中  宋立军  杨纪林  胡伟华  吴小莉 《内陆地震》2000,14(1):24-29

以北天山活动断裂地理信息系统为例,介绍了地理信息系统(ARCVIEW)空间分析功能,如空间选择、空间连接、合并分析、几何量算等;着重讨论了地理信息系统空间分析功能在地震活动性分析、活动断裂分析等方面的应用。  相似文献