The Evolutionary History of Ore-forming Processes of Metallic Ore Deposits in Northern Guangxi

The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late timesfin the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.     

我国气象科技期刊发展与作用

在对历史资料研究的基础上，对气象科技期刊的发展历程与作用进行了回顾及评述，并对目前气象科技期刊的现状及存在的问题做了简要分析。     

高烈度区连续梁桥的减震设计方法研究

本文以高烈度区的某三跨连续梁桥为例，分别采用基础隔震和消能减震两种措施进行结构的减震分析；针对隔震结构减震效果好但主梁位移过大的特点，提出了在采用铅芯橡胶隔震支座的同时设置粘滞阻尼器的减震方案，其非线性时程分析结果表明，该方案能有效地降低结构的地震反应，可供工程实践参考。     

我国金属矿产成矿区带地球化学普查发展历史

二十世纪60～70年代是我国金属矿产成矿区带地球化学普查发展的初期阶段.1976年,成矿区带地球化学普查规划制订,我国金属矿产成矿区带地球化学普查进入大规模普查实施的第一阶段;随着一系列新技术规定的颁布执行,1992年开始进入第二阶段的成矿区带地球化学异常详细检查评价与综合研究;1993年以后,成矿区带地球化学普查与详查仍然以寻找金属矿产为主要任务,同时,成矿区带地球化学普查成果开始向应用地球化学方向发展,这标志着第三个阶段的开始,即应用成矿区带地球化学普查成果进行生态环境地球化学与人类健康、综合农林业地球化学研究和开发.     

From pastoralism to tourism: The historical impact of changing land use practices in Namaqualand

We use the concept of ecological revolutions to explain the environmental history of Namaqualand, from the advent of pastoralism 2000 years BP, to colonial settlement in the 18th century and finally to the recent trend of de-agrarianization from the middle of the 20th century. Early traveller's records and census data are used to assess changes in the human population of the region and how this affected wildlife and agricultural practices. Pre-colonial indigenous hunter-gatherer (Bushmen) and pastoralist (Khoekhoen) populations in Namaqualand consisted of probably no more than a few thousand individuals. Over the next three centuries, the general population rose steadily to more than 65,000 people but has fallen in recent years. Wildlife appears not to have been abundant in Namaqualand's pre-colonial landscapes and large springbok ‘treks’ were probably a rare event. The number of domestic livestock in Namaqualand peaked in 1957 largely as a result of an increase in the number of sheep which have fallen steadily since this time. Crop production was absent from Namaqualand's pre-colonial landscapes but increased to cover nearly 30,000 ha in the early 1970s. The area under cultivation has declined by nearly two thirds since this time largely as a result of the large-scale abandonment of wheat farming in marginal environments. We touch on differences between the communal areas and private farms, particularly in terms of their human populations and agricultural impact on the land. Repeat landscape photographs support our main findings which suggest that both rocky, upland habitats and rivers have not been transformed substantially by land use practices in Namaqualand. Instead, sandy pediments have borne the brunt of human impacts in the region. Finally, we highlight the beginning of a new ecological revolution in Namaqualand due to changes in the global and national political economy.     

Organic fraction of the total carbon burial flux deduced from carbon isotopes across the Permo-Triassic boundary at Meishan,Zhejiang Province,China

By combining the carbon cycle model with the records of carbonate and organic (kerogen) carbon isotope, this paper presents the calculation of the fraction of organic carbon burial (f _org) of beds 23–40 at the global boundary stratotype section and point (GSSP) of the Permian-Triassic boundary at Meishan, Zhejiang Province. The resulting calculation produces two episodes of f _org maxima observed to occur at beds 23–24 and 27–29, which respectively corresponds to the two episodic anoxic events indicated by the flourish of green sulfur bacteria. Two episodic f _org minima occurred at beds 25–26 and 32–34, generally coincident with the flourish of cyanobacteria (bed 26 and upper part of beds 29 to 34) as shown by the high value of 2-melthyhopnoanes. It appears that the f _org is related to the redox conditions, with greater f _org values observed under the reductive condition. The relationship between f _org and the total organic carbon (TOC) content was complex. The f _org value was low at some beds with a high TOC content (such as bed 26), while high observed at some beds with a low TOC content (e.g. bed 27). This association infers the important contribution of primary productivity to the TOC content. The original organic burial could be thus calculated through the configuration of the function of the primary productivity and f _org, which can be used to correct the residual TOC measured today. This investigation indicates that compiling the organic-inorganic carbon isotopes with the carbon cycle model favors to understand the fraction of organic carbon burial, providing information for the reconstruction of the coupling among biota, environments and organic burial. Journal of China University of Geosciences, 2007, 32(6): 767–773 [译自: 地球科学—中国地质大学学报]     

A new approach of selecting real input ground motions for seismic design: The most unfavourable real seismic design ground motions

This paper presents a new way of selecting real input ground motions for seismic design and analysis of structures based on a comprehensive method for estimating the damage potential of ground motions, which takes into consideration of various ground motion parameters and structural seismic damage criteria in terms of strength, deformation, hysteretic energy and dual damage of Park & Ang damage index. The proposed comprehensive method fully involves the effects of the intensity, frequency content and duration of ground motions and the dynamic characteristics of structures. Then, the concept of the most unfavourable real seismic design ground motion is introduced. Based on the concept, the most unfavourable real seismic design ground motions for rock, stiff soil, medium soil and soft soil site conditions are selected in terms of three typical period ranges of structures. The selected real strong motion records are suitable for seismic analysis of important structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake, as they can cause the greatest damage to structures and thereby result in the highest damage potential from an extended real ground motion database for a given site. In addition, this paper also presents the real input design ground motions with medium damage potential, which can be used for the seismic analysis of structures located at the area with low and moderate seismicity. The most unfavourable real seismic design ground motions are verified by analysing the seismic response of structures. It is concluded that the most unfavourable real seismic design ground motion approach can select the real ground motions that can result in the highest damage potential for a given structure and site condition, and the real ground motions can be mainly used for structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake. Copyright © 2007 John Wiley & Sons, Ltd.     

三级层序界面野外露头的识别判断标志——以南盘江坳陷晚古生界地层为例

在岩性及岩相观察基础上以不同类型的米级旋回层序作为分层和描述地层的基本工作单元，把米级旋回层及其有序叠加形式作为识别三级层序的基础，通过野外露头的详细观察、描述认为：在南盘江坳陷晚古生界地层中SB1型层序界面是以区域平行不整合面、古风化壳、古土壤层、下伏地层的强烈白云石化以及沉积物转化面为识别标志；SB2型序界面是以沉积物转化面、地层结构转化面及古土壤层为识别标志：SB3型层序界面是以凝缩段直接覆盖在下伏地层之上为识别标志；SB型层序界面是以上下地层的岩性组合、地层结构转化面及年代地层为识别标志。     

Fourcade: the Centenary of a Stereoscopic Method of Photographic Surveying

In the Preface to his book, The Four Faces of Fourcade, Clare Storrar (1990) wrote: "It is di.cult to appreciate the breadth and depth of Henry Georges Fourcade's intelligence and creative power. He was an intellectual giant, a phenomenon, whose theoretical and practical achievements have never received proper recognition. These were all the more remarkable because he began his original work on photogrammetry when science in South Africa was in its infancy, and he laboured alone far from libraries and other research facilities. His only higher academic training was in land surveying. He was adept in each of four sciences at various stages in his life, but, mainly because of his natural reserve, his reputation was highly compartmentalised. To foresters he was 'the most brilliant forestry officer of his time' to surveyors, he was exceptionally learned in theory and skilled in practice. Photogrammetry was a new subject, unheard of, except by a handful of scientists. In botany, which he took up seriously at the age of fifty-five, his work was highly regarded by leading botanists in South Africa and in Europe. All stood in awe of his extraordinary talent and ability. Some were frightened of him. But few were able—in fact, not even the best brains were wholly qualified—to grasp fully the tremendous intellectual stature and potential of this protean man."
This paper briefly describes the historic achievements of Henry Georges Fourcade, with the emphasis on his land surveying and, in particular, his photogrammetric contributions to science. The centenary of one of these, his proposal of a stereoscopic method of photographic surveying, occurs in October 2001.