GEOLOGICAL MARKS OF A POSSIBLE EXTRATERRESTRIAL IMPACT EVENT ON THE BOUNDARY BETWEEN SINIAN/CAMBRIAN IN TIANMENSHAN IN WESTERN HUNAN     

HUANG Huaiyong  WANG Daojing  CHEN Guanghao  YIN Hanhui 《大地构造与成矿学(英文版)》2004,28(1):43-52

Geologic marks related to extraterrestrial impact events, such as impact split gravels, impact brecciate layers, impact dikes, microirghizites, microtektites, especially meteoritic residues, were discovered on the boundary between Sinian/Cambrian at Tianmenshan of Western Hunan, which may possibly demonstrate that an extraterrestrial impact event has ever occurred there on the S/C boundary.  相似文献   

建立混合经济架构，奠定地勘单位长远发展基础     

魏建全 《中国煤田地质》2004,16(6):63-64,66

分析了非公有制经济对国有地勘队伍经济体制的影响，论述了适时改革地勘单位产权制度的必要性，提出了地勘单位应该建立混合经济架构的设想，为其长远发展奠定基础。  相似文献   

矿产资源规划环境影响评价工作方法探讨   总被引：10，自引：0，他引：10  

李善峰  张进德 《地质通报》2004,23(11):1153-1156

根据《中华人民共和国环境影响评价法》关于规划的环境影响评价要求，初步探讨了矿产资源规划环境影响评价的工作思路。参照国土资源部《矿产资源规划管理暂行办法》的有关规定，列举了矿产资源规划的类型；依据《环评法》第七条和第八条，阐明了不同类型的矿产资源规划所对应的环境影响评价文件编制的要求；提出了矿产资源规划环境影响评价的工作程序和环境影响评价指标体系的建议，并简单地探讨了2种评价方法。  相似文献   

开发旅游观光资源与四川西部之发展     

赵友年 《四川地质学报》2004,24(1):46-50

川西甘孜州旅游观光资源丰富多彩，遍布的温泉、热泉与雪山、草地、森林相配置成的景点、景区比比皆是．加之悠久的人文、宗教建筑和文物，都具有很高的研究和观赏价值。开发这些资源以引导甘孜州经济的发展，将是大有可为的。  相似文献   

Magmatic effects of the lunar late heavy bombardment     

Linda T Elkins-Tanton 《Earth and Planetary Science Letters》2004,222(1):17-27

Large volumes of mare basalts are present on the surface of the moon, located preferentially in large impact basins. Mechanisms relating impact basins and mare basalt eruptions have previously been suggested: lunar impacts removed low-density material that may have inhibited eruption, and created cracks for fluid flow [Icarus 139 (1999) 246], and lunar basins have long been described as catchments for magma (e.g., [Rev. Geophys. Space Phys. 18 (1980) 107] and references therein). We present a new model for melt creation under near side lunar basins that is triggered by the impacts themselves. Magma can be produced in two stages. First, crater excavation depressurizes underlying material such that it may melt in-situ. Second, the cratered lithosphere rises isostatically, warping isotherms at the lithosphere-asthenosphere boundary which may initiate convection, in which adiabatic melting can occur. The first stage produces by far the largest volume of melt, but convective melting can continue for up to 350 Ma. We propose that giant impacts account for a large portion of the volume and longevity of mare basalt volcanism, as well as for several compositional groups, including high alumina, high titanium, KREEP-rich, and picritic magmas.  相似文献   

Crater formation in soils by raindrop impact     

Hossein Ghadiri 《地球表面变化过程与地形》2004,29(1):77-89

The process of crater formation by the impact of water drops on soil, sand and various other target material was studied. Craters of various shapes and sizes were observed on different target materials or conditions, ranging from circumferential depression to completely hemispherical shape. Crater shape was dependent upon target material, its ?ow stress or shear strength and the presence and thickness of water on the surface. Between 5 and 22 per cent of impact energy was spent on cratering, but the relationship between crater volume and kinetic energy of a raindrop was curvilinear, indicating a lower ef?ciency of impact energy in removing target material as the energy increases. Impact impulse, on the other hand, showed a more linear relationship with crater volume, and the ratio of impulse over crater volume (I/V) remained constant for the entire range of drop sizes, impact velocities, and surface conditions used in this study. Surface shear strength, represented by the penetration depth of fall‐cone penetrometer, appeared to be a key factor involved in this process. An equation was developed which related crater volume to cone penetration depth and impact impulse. Crater volume, which appeared to be a better indicator of the total amount of material dislodged by a raindrop than splash amount, can thus be predicted using this equation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Research on the effect estimation of seismic safety evaluation     

邹其嘉  陶裕禄 《地震学报(英文版)》2004,17(1):87-98

IntroductionItisdefinitelystipulatedintheLawofthePeople'sRepublicofChinaonProtectingagainstandMitigatingEarthquakeDisastersthattheseismicsafetyevaluationmustbemadeformajorprojects(includinglifelineprojects)and,accordingtotheresultsobtained,theseismicresistancerequirementsshouldbedetermined.Thenecessityofseismicsafetyevaluationhasbeenrecog-nizedgradually,butthetopicontheeffectofsafetyevaluationhasnotbeenreferredmuch.Gener-allyspeaking,althoughmostpeopleapprovethesocialeffectofsafetyevaluatio…  相似文献   

A new method for testing pile by sin- gle-impact energy and P-S curve     

许昭永  段永康  王彬  胡毅力  杨润海  许峻  赵晋明 《地震学报(英文版)》2004,17(Z1)

Introduction Through many year's practices by vast numbers of scientific and technological workers andefforts from all aspects, the dynamic testing method of high-low strain has formally entered intothe technical code of foundation pile test of construction at last (The Industry Standards of thePeople's Republic of China, 2003). The striking mode of the dynamic testing method of high strainis stipulated as hammer in the code, the striking of rocket can also be used. The latter is widely…  相似文献   

珠江河口水环境时空变异对河口生态系统的影响   总被引：6，自引：0，他引：6       下载免费PDF全文

崔伟中 《水科学进展》2004,15(4):472-478

分析近20年来珠江河口水环境变异的特征,探讨珠江河口水环境与水生物相互联系和相互作用的关系。结果表明,珠江河口形态、地貌、水文情势和入河污染物等变异改变了珠江河口水生物的栖息条件,削弱了河口生态系统的自动调节修复能力和稳定性,对河口生态系统的物质循环、能量流动和发育演化平衡构成了重大影响。  相似文献   

矿产品供需关系经济分析     

谢业文 《矿产与地质》2004,18(1):90-92

矿产品供需关系决定矿产品价格的市场走向，运用供需二维图解可以预测矿产品供需动态，给出精确的供需二维图要注意资源增加与减少、代用材料和新产品开发等因素，指出精心积累矿产品供需资料，仔细观察供需关系，可以预测矿产品价格和市场走向。  相似文献