周秦两汉时期农业灾害时空分布研究

周秦两汉时期农业灾害发生频繁，种类多样。灾害史料的灾度等级处理和统计结果表明：西周时期发生重大农业灾害8次，春秋战国时期发生重大农业灾害88次，秦汉时期发生重大农业灾害291次，农业灾害在时间分布方式表现出明显的时代特征：（1）农业灾害在年内季节分布中存在不平衡性；（2）农业灾害在年际分布中出现多个集中频发的时间区间，而且，愈到后来农业灾害集中发生的现象愈为明显，在空间分布方面，山东，山西地区是周秦两汉时期的农业重灾区。     

Cretaceous flysch and pelagic sequences of the Eastern Alps: correlations, heavy minerals, and palaeogeographic implications

Flysch and pelagic sedimentation of the Penninic and Austroalpine tectonic units of the Eastern Alps are results of the closure of the Tethyan-Vardar and the Ligurian-Piemontais Oceans as well as of the progressive deformation of the Austroalpine continental margin. The Austroalpine sequences are characterized by Lower Cretaceous pelagic limestones or minor carbonate flysch and various siliciclastic mid- and Upper Cretaceous flysch formations. Chrome spinel is the most characteristic heavy mineral delivered by the southern Vardar suture, the northern obduction belt at the South Penninic-Austroalpine margin and its continuation into the Klippen belt sensu lato of the Carpathians. The South Penninic sequences, e.g. the Arosa zone, the Ybbsitz Klippen zone and some flysch nappes also contain chrome spinel, whereas the sediments of the North Penninic Rhenodanubian flysch zone are characterized by stable minerals and garnet.     

胶东—苏北石榴石二辉橄榄岩形成条件及年代

在胶东—苏北地区,由石榴石二辉橄榄岩、尖晶石二辉橄榄岩、石榴石辉石岩、榴辉岩、斜辉辉橄岩和纯橄岩组成的杂岩成群和成带分布,延长590km。该岩带越过郯庐断裂带延伸至大别山,全长约1200km。岩带内石榴石二辉橄榄岩与尖晶石橄榄岩伴生,组成较大的岩块,并且与榴辉岩伴生,曾被作者确定为一种有层序的岩套。石榴石二辉橄榄岩的Sm-Nd同位素年龄为925±53Ma,矿物地质温度计和压力计表明其形成于115—160km深部,温度为800—1371℃。该石榴石二辉橄榄岩平衡温度和压力符合大陆地温线,而不同于中国东部沿海地区玄武岩中包体石榴石二辉橄榄岩,后者的平衡温度压力符合于大洋地温线。     

Continental rifting and drainage reversal: The clarence river of Eastern Australia

The Clarence River on Australia's east coast has an anomalous drainage pattern. Its right-bank tributaries are markedly barbed, suggesting reversal, whereas Tertiary volcanism has disrupted its left-bank drainage. The southeast-flowing Clarence is closely aligned with the northwest-flowing Condamine River just across the Continental Divide. The Condamine-Clarence alignment is continued by a large southern tributary, the Orara River, which flows northwest, away from the sea, to meet the southeast-flowing Clarence. A broad river with a quite different character flows east from near the Orara-Clarence junction to the sea. This is essentially an overflow channel. This series of aligned streams, the Condamine-Clarence-Orara, represents the remains of an earlier northwest-flowing stream that extended the full length of the Clarence-Moreton Basin, an eastern extension of the Great Artesian Basin. During the Jurassic, the Clarence-Moreton Basin was filled with sediments from the surrounding highlands, including those to the east of the present coastline. Continental rifting from Late Cretaceous times onwards led to the opening of the Tasman Sea, causing the reversal and beheading of the original northwest-flowing streams and the formation of the Great Escarpment. The evolution of the Clarence River does not fit into most conventional geomorphic paradigms such as cycles, climatic geomorphology or steady-state landforms. It is the result of a succession of unique events on a very long timescale, and as such is a classic example of evolutionary geomorphology.     

Marginal basins of the NW Pacific and Eastern Eurasia

ABSTRACT

The broad zone between old oceanic lithosphere of the NW Pacific and Eastern Eurasian continental lithosphere is home to a chain of marginal basins. Different from oceans, marginal basins are more influenced by the underlying subduction zone both geophysically and geochemically and are more likely to be blanketed by sediments from the nearby continent. This special issue collects 19 papers that explore the tectonic, magmatic, sedimentary and fluid activity features of marginal basins during rifting, spreading and post-spreading stages. Most papers in this special issue focus on South China Sea marginal basins, where abundant research provides interesting insights into how marginal sea basins evolve. Because South China Sea basins are fully evolved and their key features have not been overprinted by younger deformation, the results of this special issue are very useful for understanding the evolution of other marginal basins.     

中国大陆东部新构造期北西向断裂带的初步探讨

前人对中国大陆东部新构造期 (N—Q)活动的北东向断裂 (带 )已有很多研究。笔者根据地震构造、新构造和火山活动等资料并结合Pn波速结构研究结果 ,分析了该区新构造期的北西向活动断裂 ,初步得出 :北西向断裂具有成带性 ,可分 7条北西向断裂带 ;它们有鲜明的新生性 ;均为地壳构造带 ;与北东向断裂带呈共轭关系 ,是在先存构造基础上于新构造应力场作用下正在发育的一套地壳共轭剪切破裂系统。     

On the relationship between auriferous talc deposits hosted in volcanic rocks and massive sulphide deposits in Egypt

The volcanic-hosted massive sulphide (VHMS) deposits in the Eastern Desert of Egypt (e.g., Um Saki deposit) are associated with Precambrian coarse acid pyroclastic rocks. The upper contacts of the massive sulphide body are sharp and well-defined; while the keel zone to the mineralization is always associated with pervasive alteration, characterized by the presence of septechlorite and talc, associated with variable amounts of carbonate and tremolite. On the other hand, the economic talc deposits in Egypt are hosted intensively altered volcanic rocks. Besides talc, chlorite, carbonates and tremolite that occur in variable amounts in these deposits, anomalously high concentrations of gold are also present.The present study showed that alterations in the talc deposits of Darhib, El Atshan, Abu Gurdi, Egat, Um Selimat and Nikhira are similar to those occurring in the keel zone underlying the VHMS of Um Samuki and that the chemical modifications due to alteration processes (additions of Mg, Fe, Mn and Ca coupled with depletions in silica, alkalies, alumina and titanium) are comparable, even the host rocks are different, thus reflecting a genetic relationship. It is suggested that, the examined localities of talc deposits are hosted in the intensively altered volcanics in the keel zones of volcanogenic massive sulphide deposits. Recently, detailed geophysical prospecting program, including electric (resistivity, self-potential and induced polarization), electromagnetic and magnetic methods, was carried out at Darhib, Abu Gurdi and Um Selimat talc deposits. The quantitative interpretation of these geophysical measurements revealed the presence of subsurface bodies of sulphides. The present distribution of talc and allied minerals in Darhib, El Atshan, Abu Gurdi, Egat, Um Selimat and Nikhira could be explained by a tectonic process in which the coarse acid pyroclastic rocks with massive sulphides have tilted in such way that the footwall rock alterations (talc and allied minerals) are exposed on the present-day surface at these localities. Structural studies are currently under way in an attempt to explain the deformation regime that led to the present situation of talc deposits.Two distinct spatial and mineralogical associations of gold mineralization could be identified in the volcanogenic massive sulphide deposits and their footwall alterations (the keel zone) in the Eastern Desert of Egypt. These are (1) gold–silver–zinc association, and (2) gold–copper association. In the former, gold grades are very low and silver is anomalous. This association occurs typically in the upper levels of the VHMS deposit where low-temperature sulphides are abundant. Gold was deposited because of the mixing between the ascending hot solutions and the sulphate-rich seawater. The upper levels of Um Samuki sulphide body represent this association. Gold–copper association, on the other hand, typically occurs in the footwall altered rocks (the keel zone) and the lowest parts of the massive sulphide body. Gold grades reach up to 5.54 ppm, but the average is 1 ppm. Silver is very low, usually in the range of 4–10 ppm. Lead usually, but not always, accompanies gold in this association. Deposition of gold probably took place due to decreasing of temperature and/or increasing pH of the ascending hot brines. The keel zones at Darhib, Abu Gurdi, El Atshan, Um Selimat, Nikhira and Egat talc mines better represent this association.     

Convergence or divergence?: Status and prospects for US climate strategy

The objective of this paper is to assess recent developments and prospects for future changes in United States (US) climate strategy. In doing so, the paper explores some of the key factors that have shaped strategies and policies to date, distinguishing between factors related to institutional and governance structures, linkages between science and policy, energy technology and the role of interest groups. Against this background, the paper attempts to explore future development paths for US climate policy. More specifically, the paper assesses opportunities for policy changes compared to the preferences of the current administration, and the prospects for future linkages between US and international climate change strategies. In brief, the paper argues that substantial changes are unlikely to take place in the near to medium term, leaving open, however, the possibility of wide-ranging changes in domestic politics or major incidents that could facilitate a shift in the perceived need for near-term action.     

Trend Surface Modelling of Karlapat Bauxite Deposit, Eastern Ghat Group, Orissa, India

Abstract: The Karlapat bauxite deposit occurs in the Eastern Ghat Group of rocks in Orissa and has developed in the khondalites. Mineralogical and physical observations on bore hole samples reflect the presence of a maximum of six weathered zones from top to bottom. These zones are termed as topsoil, siliceous laterite, ferruginous laterite, bauxite, lithomarge and altered khondalite. Four-dimensional trend surface models are developed for the data of 45 and 36 bore holes from north and south blocks, respectively, on Al₂O₃ and SiO₂ to delineate the zones of metallurgical grade bauxite (SiO₂5 % and Al₂O₃40 %). The results indicate about 15 m thickness of bauxite in the north block while it could be up to 20 m thick in the south block, leaving about 10 m of lat-erites at the top of each block. High grade bauxite (>47 % Al₂O₃) is also encountered at specific locations.