超大型矿床的探寻与研究的若干进展

本文主要讨论最近两年国内外探寻与研究超大型矿床所取得的若干进展。内容涉及：超大型矿床与类似名词定义、典型剖析、超大型矿床分类、矿化类型、全球背景研究等问题。在简要介绍国内外超大型矿床研究现状后，文中提出，结合我国矿产地质实际，宜以１９８７年国家储量委员会规定之大型矿床５倍储量为超大型矿床下限。超大型矿床可暂分三类：第一类之同类型大、中、小型矿分布甚广；第二类则反之，同类型矿床极罕见；第三类为过渡类型。笔者指出，不少有色金属在超大型矿床的矿化类型上有强烈选择性，即某一矿种虽可存在多种矿化类型，但一般仅一、二种类型可形成超大型矿床。提出这一点对寻找超大型矿床十分重要。文中举出若干实例，论证对某些超大型矿床进行全球背景研究之必要及超大型矿床研究可提高成矿理论水平。     

An annual fossil record of production,planktivory and piscivory during whole-lake manipulations

Annual and subannual paleolimnological records of pigments and zooplankton were used to analyze three whole-lake manipulations. The relative abundance of cladoceran remains in recent seasonal laminae was significantly correlated with the relative abundance of species in the plankton (r ²=0.59,P<0.001). Comparison of food-web structure after piscivore introduction showed that there are multiple outcomes of predation and that final food-web structure depended on the strength of interaction between piscivorous and planktivorous fish. Intense predation on cyprinids (Phoxinus eos, P. neogaeus, Umbra limi) by largemouth bass (Micropterus salmoides) allowed large herbivores (Daphnia pulex) and invertebrate predators (Chaoborus punctipennis) to dominate. Analysis of fossil invertebrate morphology suggested that small grazers (Bosmina longirostris, Diaphanosoma birgei) were eliminated by invertebrate predators. Under moderate predation by rainbow trout (Oncorhynchus mykiss), cyprinids remained, only intermediate-size herbivores (D. rosea) increased in abundance, andBosmina persisted. In contrast to food-web manipulations, increased algal abundance resulting from watershed disturbance (road construction) did not alter the species composition or size-structure of fossil Cladocera.     

Protecting the national parks and the world heritage sites in China: challenge and strategy

About 70% of its land area as mountains and plateaus, China is the largest mountain country in the world. Thanks to its vast territory (9.6 million km²), outstanding relief and varied climates, China boasts extremely plenty of ecosystems and landscapes. From south to north, it traverses almost all the temporal zones from tropical rainforest in the southernmost to frigid-temperate needle-leaved forest in the northernmost; from east to west, it sees a gradual transition fro humid forest landscape to extremely arid desert landscape; vertical change of landscapes is most striking owing to the existence of many high mountains (above 6000–7000 m, e.g., the Himalayas, the Kunlun, the Tianshan, the Hengduan, etc.) and plateaus, especially the immense Tibetan Plateau (averagely 4500 m above sea level). All of this give rise to the richness and diversity of ecosystems and landscape in China. Some of the ecosystems are endemic to China, e.g., alpine desert and alpine steppe in the Tibetan Plateau. As a result, China bears a great responsibility in the protection of global ecosystems and landscape.     

Deep Natural Gas Resources

From a geological perspective, deep natural gas resources generally are defined as occurring in reservoirs below 15,000 feet, whereas ultradeep gas occurs below 25,000 feet. From an operational point of view, deep may be thought of in a relative sense based on the geologic and engineering knowledge of gas (and oil) resources in a particular area. Deep gas occurs in either conventionally trapped or unconventional (continuous-type) basin-center accumulations that are essentially large single fields having spatial dimensions often exceeding those of conventional fields.Exploration for deep conventional and continuous-type basin-center natural gas resources deserves special attention because these resources are widespread and occur in diverse geologic environments. In 1995, the U.S. Geological Survey estimated that 939 TCF of technically recoverable natural gas remained to be discovered or was part of reserve appreciation from known fields in the onshore areas and state waters of the United States. Of this USGS resource, nearly 114 trillion cubic feet (Tcf) of technically recoverable gas remains to be discovered from deep sedimentary basins. Worldwide estimates of deep gas also are high. The U.S. Geological Survey World Petroleum Assessment 2000 Project recently estimated a world undiscovered conventional gas resource outside the U.S. of 844 Tcf below 4.5 km (about 15,000 feet).Less is known about the origins of deep gas than about the origins of gas at shallower depths because fewer wells have been drilled into the deeper portions of many basins. Some of the many factors contributing to the origin and accumulation of deep gas include the initial concentration of organic matter, the thermal stability of methane, the role of minerals, water, and nonhydrocarbon gases in natural gas generation, porosity loss with increasing depth and thermal maturity, the kinetics of deep gas generation, thermal cracking of oil to gas, and source rock potential based on thermal maturity and kerogen type. Recent experimental simulations using laboratory pyrolysis methods have provided much information on the origins of deep gas.Technologic problems are among the greatest challenges to deep drilling. Problems associated with overcoming hostile drilling environments (e.g. high temperatures and pressures, and acid gases such as CO₂ and H₂S) for successful well completion, present the greatest obstacles to drilling, evaluating, and developing deep gas fields. Even though the overall success ratio for deep wells (producing below 15,000 feet) is about 25%, a lack of geological and geophysical information continues to be a major barrier to deep gas exploration.Results of recent finding-cost studies by depth interval for the onshore U.S. indicate that, on average, deep wells cost nearly 10 times more to drill than shallow wells, but well costs and gas recoveries differ widely among different gas plays in different basins.Based on an analysis of natural gas assessments, deep gas holds significant promise for future exploration and development. Both basin-center and conventional gas plays could contain significant deep undiscovered technically recoverable gas resources.     

Availability of Bauxite Reserves

Based upon a large database, this paper analyzes the record of bauxite mine production, exploration success, and resource depletion and evaluates the availability of bauxite reserves in the near future. The record clearly shows that for the past 50 years world bauxite production rose by an annual increase of over 5% while per capita consumption rose during the same period by about 4%. Time trends of the world bauxite reserve life index (RLI); that is, known world reserves of a given year divided by world production of the same year, are episodic and seem to follow bauxite price cycles. The present-day RLI indicates adequate bauxite supply for about 180 years and is the same as it was in 1950. However, if an annual growth rate of 5% is considered, the currently known reserves will be exhausted within the next 20 years and the reserve base will be adequate for not more than 25 years. This scenario is based, of course, on the unrealistic assumption that future exploration efforts fail to discover additional reserves. Evaluation of the quality, in terms of bauxite signatures, and quantity of presently known bauxite prospects that may be mined in future suggests that there is sufficient potential for adequate bauxite supply for the next 20 to 25 years at least. Bauxite signatures cover a wide range of values that allows selection of the most favorable bauxite prospects for future mining, both in economic as well as environmental terms. Although, there is the general believe that the world abundance of bauxite resources will ensure sufficient supply to meet future demands significant additional reserves have to be discovered if exponential growth rates continue. As the question of future bauxite supply is subject to economic and geologic principles one has to take into consideration that increasing exploration maturity in many mineral provinces will make it difficult to locate additional bauxite reserves and that decreasing real commodity prices will influence the level of investment in bauxite exploration.     

网络地图人性化界面设计

目前网络地图发展迅猛,但界面设计缺少理论指导,仍存在着许多问题.文中首先研究了网络地图的特点和界面内容,对目前网络地图界面设计中存在的突出问题进行归纳.接着提出了基于认知心理学理论的一般性网络地图界面设计原则.最后,对网络地图的用户层次进行分类,举例说明上述设计原则在人性化网络地图界面设计中的应用.     

CHINA: A COUNTRY OF THE THIRD WORLD OR THE THIRD GREAT POWER?

l.TheRapidEcono1ulcDevelopmentofCho1aSinceeconoAncreformandopen-doorpolicy,Cltinahasgrownrapidly.GDPinl993is3.4tilllesasmuChasti1atinl978.Annualgrowtlrateis9.2percent.li1ti1isresped,itisworthwniletostudyWhereChinaislocatedinti1eecononticltistoryoftheworld,andwhatthetrendofcurrentdeveoPmentwillChangeinto.Indevelopedcountriesofh1eWest,whentherateofecononhcdevelopmotwasthelligheSt,itwasnotltigherti1anthatofCltina'seconol11icdevelopmentafterreforl11andopen-doorpolicy.U.K.,forexample,Whichh…     

矢量图形与主数据库无缝连接万维网地理信息系统的设计和实现

首先介绍了万维网地理信息系统、Ｊａｖａ和ＪＤＢＣ，讨论了目前万维网地理信息系统的设计和实现方法以及存在的问题，提出了矢量图形与主数据库无缝连接模型，并使用Ｊａｖａ和ＪＤＢＣ设计实现了万维网地理信息系统软件，使客户在客户端实现放大、缩小、漫游、查询、统计和分析等地理空间分析功能。     

基于WebGIS 的地下水环境监测信息发布系统研究

基于WebGIS的地下水环境监测信息发布系统涉及了网络技术、地理信息系统技术、数据库技术、软件工程等。本文简要介绍了WebGIS的关键技术，并从数据库、WebGIS综合管理服务、Web服务器和Web浏览器4个方面阐述了构成地下水环境监测信息发布系统的技术框架。根据系统的设计方案进行了相应的开发和配置，并以山东省地下水环境监测数据为例，实现了基于WebGIS的地下水环境监测信息发布。