Metamorphic ore remobilization in the Hällefors district, Bergslagen, Sweden: constraints from mineralogical and small-scale sulphur isotope studies

The marble- and metavolcanic-hosted Pb–Zn–(Ag–Sb–As) deposits of the Hällefors district, located in the Palaeoproterozoic Bergslagen ore province, south central Sweden, comprise both stratabound sulphides and discordant, Ag-rich sulphide–sulphosalt veins. The complex sulphide–sulphosalt assemblages of the Alfrida-Jan Olof mines at Hällefors were investigated by a combination of ore microscopy, electron-microprobe analysis, and in situ laser sulphur isotope analysis. The massive ore is characterized by positive and homogeneous ³⁴S (+1.4 to +2.7 V-CDT), whereas vein-hosted sulphides and sulphosalts exhibit similar, but generally less positive to slightly negative ³⁴S (–0.6 to +2.0). Comparison of the observed ore mineral assemblages with calculated phase equilibria in the system Fe–As–S–O–H and isotopic fractionation as a function of temperature, oxygen fugacity and pH indicates that the vein-type mineralization was formed from relatively reduced and rather alkaline hydrothermal fluids. At these reduced conditions, fractionation of ³⁴S via changes of fO₂ is insignificant, and thus the isotopic signatures of the vein minerals directly reflect the composition of the sulphur source. We therefore conclude that the vein-type ore essentially inherited the sulphur isotope signature from the pre-existing massive sulphides via metamorphic remobilization at approximately 300–400°C and 2–3 kbar. Scales of remobilization observable are on the order of about 5 mm to 30 cm. Overall, the sulphide–sulphosalt assemblages from the Alfrida-Jan Olof mines exhibit ³⁴S values which are comparable to a majority of metasupracrustal-hosted deposits in the Bergslagen province, thereby suggesting a common origin from ca. 1.90–1.88 Ga volcanic-hydrothermal processes.Editorial handling: S. Nicolescu     

遥感在灾害调查中产生的社会经济效益——以北京市门头沟区洪水、地质灾害遥感调查为例

本文叙述了北京市门头沟地区洪水、泥石流等灾害遥感技术调查的概况。同时指出,该成果对门头沟区历年的汛期防灾部署起到重要作用,成为防灾救灾的重要依据,产生了巨大的社会经济效益。文中对该区主要灾害的类型及其危害程度作了评价,同时按村镇的受害程度,将村镇分为4类,并对每类村镇受灾害的危害程度及应采取的措施,提出了具体意见。还对日后可能发生严重灾害的潜在因素进行了分析。     

淮北地区寒武系/新元古界界线讨论

淮北地区寒武系与新元古界的界线 ,长期以来存在争议 ,主要有 5种划分意见 :猴家山组 /沟后组 ,沟后组 /金山寨组 ,沟后组上段 /沟后组下段 ,金山寨组 /望山组及猴家山组 /金山寨组之间。通过近年来的实地考察和室内研究 ,从叠层石、宏体碳质压膜化石及小壳动物化石组合综合考虑 ,认为该区新元古界最上面的岩组应是沟后组 ,而超覆于区内新元古界不同层位上的长期被描述为猴家山组“豹斑状”灰岩、白云岩 ,实为昌平组 ,属下寒武统     

用于虚拟现实的分区漫游

为了加快对三维可视化中海量数据浏览的速度，提出了分区漫游的思想，并通过虚拟现实建模语言和Java的结合来实现。     

Basic characteristics of recent tectonic stress field in southwest China

Direction and structure characteristics of 58 tectonic stress tensors have been determined in 41 surveyed areas (points) in the southwestern district of China through a calculation method for inversion of tectonic stress tensors from sliding direction of faults, and, in combination with seismic mechanism solution andin-situ stress measurements, the following characteristics of the recent tectonic stress fields in the southwestern district of China have been defined: (1) the stress fields in this district have remained stable since the end of early to mid-Pleistocene; (2) the effect of such tectonic stresses is mainly horizontal; (3) the orientation of the maximum principal stress axis shows a trend of regular rotation from north to south, i. e. from NEE-SWW in northern Songpan and Longmen Shan areas to sub-EW in the central part of western Sichuan, and further to NNW-SWW or sub-SN in Yunnan; (4) the regional tectonic stress fields are of distinct division character; (5) there is well concordance between the main direction and type of stress structures in the stress tate both in deep and shallow parts of the crust. In addition, studies of staged tectonic stress tensors preliminarily show that in early Quaternary the southwestern district was mainly affected by lateral compression of Indian plate, under which the regional tectonic stress fields mainly display NE-sub-EW compression. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 407–417, 1993.     

论工业区的地域结构与地域类型

本文分析了工业区地域结构的特点和演变规律,把工业区划分为5种地域类型,并阐述各类工业区的地域结构特点。     

桂西北区中三叠统含金浊积岩系沉积学

本文以中三叠统浊积岩系岩性相的识别为基础,通过垂向层序的划分和分析,结合区分出浊流主体流向与溢堤流流向数据的古流分析、古坡向分析、中三叠统板纳组地层等厚图,概括了本区中三叠统浊流沉积的总体配置,厘定了右江浊积盆地在安尼期、拉丁期时的沉积格局。最后,讨论了右江浊积盆地的水深变化趋势、浊积岩系形成的背景条件,以及浊积盆地的存在与金矿成矿作用之间的关系。     

应用模式识别方法确定乌鲁木齐以西的潜在震源区

根据乌鲁木齐以西地区与强震活动有关的地质、地貌、地球物理等特征,应用cora—3方法对乌鲁木齐以西的潜在震源区进行模式识别,结果表明,容易发生强震的地区主要与断裂及其端点、拐点、交点有关,而且其数目越大判定为强震可能发生地点的概率越大,1943——1989年已发生地震的五个地区,均为未来可能发生强震的地点。     

渭南地区建设地理研究

本文应用建设地理学的理论,对陕西渭南地区的区域开发提出了以下战略构想和措施。①建立重轻农和第三产业协调发展的产业结构模式;②建立新兴的重化工、有色金属、能源和建材工业基地;③建立开放型的现代农业体系;④建立整体协调的区域社会经济结构;⑤疏通各种渠道,吸引外资;⑥开发旅游资源,完善旅游服务体系;⑦加强生态环境建设;⑧进一步解放思想,提高干部和公民的现代文化和改革开放意识。     

第四系覆盖层及水体下遥感影像隐伏地质构造信息的提取

本文阐述了利用多时相多波段卫星遥感影像和CCT磁带进行计算机数字增强处理、提取山东省南四湖含煤区水体下及第四系覆盖层下隐伏地质构造信息的方法,解译出了该区的主要断裂构造格架,指出了隐伏的隆起、凹陷、褶皱和火成岩体的分布范围,为煤田勘探和开采提供了有价值的资料。