广西河池地区矿产资源勘查成果展销会情况介绍

１９９５年７月１１日—１２日，广西地矿厅和河池地区行署首次联合举办矿产资源勘查成果展销会，会址设在河池市，与会代表１３０余人。展销会提交大会展销的矿产资源勘查成果３８项，引资勘查项目３８项。经买卖双方三天的洽谈，涉及到的项目２５项，会议期间签订矿产资源勘查成果合同协议４项，愈千万元，取得较好的社会经济效益。为地勘资金多渠道来源开辟了新路子，对促进地勘单位地质找矿工作及勘查成果有偿使用发挥了重要作用     

桂西古侵蚀沉积间断面型金矿床(续载)

古侵蚀沉积间断面型金矿是桂西的主要金矿床类型。文章着重分析该类型金矿成矿地质条件 ,论述矿床成因及成矿机理 ,认为此类型金矿易采易冶 ,经济效益显著 ,建议加大开发力度。     

贵港市矿业发展现状与对策

文章从贵港市矿产资源情况出发 ,通过对开发现状及存在问题的分析 ,探讨保证资源的合理开发和永续利用 ,为经济建设提供物质支撑的理念 ,提出了矿业可持续发展的对策。     

A 20‐ka climate record from Central Himalayan loess deposits

The southwest monsoon that dominated Central Himalaya has preserved loessic silt deposits preserved in patches that are proximal to periglacial areas. The occurrence of such silts suggests contemporary prevalence of cold and dry northwesterly winds. Field stratigraphy, geochemistry, mineral magnetism, infrared stimulated luminescence (IRSL) and radiocarbon dating has enabled reconstruction of an event chronology during the past 20 ka. Three events of loess accretion could be identified. The first two events of loess deposition occurred betweem 20 and 9 ka and were separated by a phase of moderate weathering. Pedogenesis at the end of this event gave rise to a well‐developed soil that was bracketed around 9 to > 4 ka. This was followed by the third phase of loess accretion that occurred around 4 to > 1 ka. Episodes of loess deposition and soil formation are interpreted in terms of changes in the strength of the Indian southwest monsoon. Copyright © 2005 John Wiley & Sons, Ltd.     

Annual variation of atmospheric carbonyl sulfide in the marine atmosphere in the Southern Indian Ocean

Measurements of the concentrations of carbonyl sulfide (COS) in the marine atmosphere were made over a period of two years in the southern Indian Ocean (Amsterdam Island, 37°50 S–77°31 E; March 1987–February 1988 and April 1989–February 1990). The mean atmospheric COS concentration for the whole period was 475±48 pptv (n=544). Atmospheric COS concentrations show no significant seasonal variation with a summer to winter ratio of 1.05. Taking into account the observed variability of the atmospheric COS concentration (10%), a value of 1.4 yr is estimated as a lower limit for the atmospheric COS lifetime. A comparison of the COS data at Amsterdam Island with those obtained in the Southern Hemisphere in the past 12 yr does not reveal any significant trend in the tropospheric background COS mixing ratio.     

柿竹园矿床大理岩型锡矿石工艺矿物学研究

大理岩型锡矿石产于燕山早、中期千里山花岗岩与中、上泥盆统灰岩的外接触带。矿石呈细脉、网脉浸染状,锡矿物有:锡石、黄锡矿,富钛尼日利亚石、尼日利亚石和木锡矿,脉石矿物绿帘石、石榴石、电气石、萤石、方解石及磁黄铁矿等亦含锡,锡主要呈锡的浊立矿物存在,占总锡量的89.78％,其中锡石锡占总锡量的80.01％,其次有呈类质同象形式存在的锡,在绿帘石、石榴石、电气石等矿物中以Sn~(4+)取代Fe~(3+),这类锡占总量的8.33％。工艺矿物学研究表明,该类锡矿石以“贫”、“细”、“杂”为特征。锡不仅十分分散,而且品位偏低,矿石矿物组合及镶嵌关系复杂、相互包裹,紧密连生;锡矿物粒度微细,粒径一般为0.2～0.01mm,部分为<0.0l～0.002mm,是一种难选的锡矿石类型。通过锡的回收试验,采用选冶联合工艺流程,预测锡的最佳回收率可达50％以上。     

Age and depositional environment of the Draa Sfar massive sulfide deposit, Morocco

The Draa Sfar mineralization consists of two main stratabound orebodies, Sidi M’Barek and Tazacourt, located north and south of the Tensift River (“Oued Tessift”), respectively. Each orebody is comprised by at least two massive sulfide lenses. The hosting rocks are predominantly black shales, although minor rhyolitic rocks are also present in the footwall to the southern orebody. Shales, rhyolitic volcanic rocks, and massive sulfides are all included into the Sarhlef Series, which is recognized as one of the main stratigraphic units of the Moroccan Variscan Meseta. Hydrothermal activity related with an anomalous thermal gradient, together with a high sedimentation rate in a tectonically driven pull-apart marine basin, favored the accumulation of organic-rich mud in the deepest parts of the basin and the sedimentary environment suitable for massive sulfide deposition and preservation. This took place by replacement of the hosting unlithified wet mud below the sediment–water interface. Geochemical data suggest a sedimentary environment characterized by oxic water column and anoxic sediment pile with the redox boundary below the sediment–water interface. The low oxygen availability within the sediment pile inhibited oxidation and pyritization of pyrrhotite. Biostratigraphic analysis, based on the palynological content of the hosting black shales, restricts the age of the sulfides to the Asbian substage (mid-Mississippian). This age is consistent with earlier geochronological constraints.     

Mineralogy and composition of Kuroko deposits from northeastern Honshu and their possible modern analogues from the Izu-Ogasawara (Bonin) Arc south of Japan: Implications for mode of formation

The Kuroko deposits of NE Honshu are a key type deposit for the study of volcanogenic massive sulfide deposits. However, these deposits have not been studied in detail since the early 1980's and knowledge of their mode of formation is now dated. In this study, we present the analysis of 12 samples of the Kuroko deposits, 12 samples of submarine hydrothermal minerals from the Sunrise deposit and 6 samples from Suiyo Seamount, both of which are located on the Izu-Ogasawara (Bonin) Arc, for 27 elements. For the Kuroko deposit, Cd>Sb>Ag>Pb>Hg>As>Zn>Cu are highly enriched, Au>Te>Bi>Ba>Mo are moderately enriched, In>Tl are somewhat enriched and Fe is not significantly enriched relative to the average continental crust. Within each of these deposits, a similar pattern of element associations is apparent: Zn–Pb with As, Sb, Cd, Ag, Hg, Tl and Au; Fe–Cu–Ba with As, Sb, Ag, Tl, Mo, Te and Au; Si–Ba with Ag and Au; CaSO₄. The enrichment of the chalcophilic elements in these deposits is consistent with hydrothermal leaching of these elements from the host rocks which are dominantly rhyolite–dacite in the case of the Kuroko deposits, rhyolite in the case of the Sunrise deposit and dacite–rhyolite in the case of the Suiyo Seamount deposit. However, this pattern of element enrichment is also similar to that observed in fumarolic gas condensates from andesitic volcanoes. This suggests that there may be a significant magmatic contribution to the composition of the hydrothermal fluids responsible for the formation of the Kuroko deposits, although it is not yet possible to quantify the relative contributions of these two sources of elements.The compositional data show that Sunrise and Suiyo Seamount deposits are much closer compositionally to the Kuroko deposits from NE Honshu than are the submarine hydrothermal deposits from the JADE site in the Okinawa Trough which contain, on average, significantly higher concentrations of Pb, Zn, Sb, As and Ag than each of these deposits. In spite of the greater similarity in tectonic setting of the Hokuroku Basin in which the Kuroko deposits formed to the Okinawa Trough (intracontinental rifted back-arc basin) compared to Myojin Knoll and Suiyo Seamount (active arc volcanoes), it appears that submarine hydrothermal deposits from Myojin Knoll and Suiyo Seamount are closer analogues of the Kuroko deposit than are those from the Okinawa Trough. The present data are consistent with the magmatic hydrothermal model for the formation of Kuroko-type deposits as formulated by Urabe and Marumo [Urabe, T., Marumo, K., 1991. A new model for Kuroko-type deposits of Japan. Episodes 14, 246–251].     

青海南部熔积岩的发现:对寻找VMS型矿床的重要启示

熔积岩指的是侵入、混合到未固结或弱固结的湿沉积物中的熔浆分解、原位形成的一类特殊岩石。正确地认识该类岩石,有利于增进人们对岩浆-水(沉积物)相互作用过程的理解,恢复古环境。在青海南部沱沱河地区发现了一套角砾为撕片状、锯齿状及浑圆状的安山岩,胶结物为铁硅质组合的特殊熔积岩。研究表明,该熔积岩的角砾为岩浆遇水后快速淬火、裂解的产物,铁硅质组合为海底喷气沉积形成的含铁建造;且安山岩与含铁建造发生混合时,含铁建造尚未固结。该套熔积岩的发现,改变了长期以来对开心岭铁矿为火山热液交代安山岩而形成的认识,对于在矿区寻找VMS型矿床、区域内寻找海底热水喷流沉积型矿床具有重要的启示意义。     

云南官房铜矿床矿石矿物特征及银的赋存状态

通过显微镜鉴定、电子探针(EPMA)及扫描电镜能谱分析(SEM/EDS)等方法,首次对官房铜矿的矿物组合和银的赋存状态进行了研究。初步查明,矿石矿物为中-低温热液成因,并受火山机构及断裂构造的控制;银矿物主要为碲银矿和辉银矿。矿石中银与铜呈明显正相关关系,而方铅矿中不含银。银主要以类质同象的形式赋存于含铜矿物或黄铁矿中;银的独立矿物含量低,且多呈包裹体的形式存在于黄铜矿、斑铜矿及黄铁矿中,或以微细粒状赋存于矿物颗粒间和斑铜矿的表面。