贵州中三叠统烂泥沟金矿有机质的初步研究

烂泥沟金矿是以浊积岩为容矿岩石的微细浸染型金矿。有机岩石学分析表明,矿石与围岩中干酪根类型无明显差别,同属腐泥-腐植型。与围岩相比,矿石中干酪根成熟度(R₀=2.74%-3.06%)和含金性(6.15-24.8μg/g)均较高;干酪根总含金量在全岩中所占的比例是围岩高于矿石。氯仿沥青“A”的检测说明,矿石样品中可溶性有机质形成于强还原和高盐度环境,沥青质和含硫有机化合物发育。研究认为,干酪根含金性与碳的活化有关;不饱和的有机基因对金的动一定转换可能具有重要意义。     

矿物标型六性及其在胶东金矿中的应用

目前矿物标型研究和应用已进入一个新的阶段。作者从哲学的高度,把国内外矿物标型特征的分散研究加以集中概括和总结,提出了“矿物标型六性”的普遍规律,即普遍性、特殊性、变化性、相应性、继承性和分带性,对矿物标型特征研究具重要的指导意义。这些规律在胶东金矿中得到广泛应用,并已取得良好效果。     

An electrochemical study of pyrite oxidation in the presence of carbon coatings in cyanide medium

The anodic and cathodic behaviour of pyrite with clay and different carbon coatings of activated carbon, graphite and carbonaceous matter in cyanide medium was investigated using the potentiodynamic method. The presence of clay coating did not change the polarisation curve appearance for either the anodic oxidation of pyrite or the cathodic reduction of oxygen or the potential of the current plateau, but only decreased the plateau current especially at a higher coating thickness. The presence of the carbon coatings marginally shifted the rest potential for pyrite to a more anodic position and slightly changed the polarisation curve appearance for pyrite oxidation. The current density for pyrite oxidation largely increased in the presence of the carbon coatings, the potential at the plateau shifted to more cathodic positions, and the plateau width became smaller. These effects became more noticeable at a higher coating thickness. The activated carbon, graphite and carbonaceous matter coatings performed similarly in affecting pyrite oxidation at a similar thickness. The carbon coatings significantly increased the limiting current densities for oxygen reduction on pyrite, and the limiting current plateau became steeper at a higher coating thickness. The carbon coatings increased the limiting current density for oxygen reduction to a similar extent at a low coating thickness, but increased to varied extents at a higher coating thickness. The carbon coatings also greatly increased the cathodic current density for gold reduction on pyrite. The enhancement of pyrite oxidation and oxygen or gold reduction on pyrite by the carbon coatings was likely attributed to the electrochemical interaction between pyrite and the carbon materials with electron-rich surfaces and high conductivity. The presence of the carbon coatings significantly increased the oxidation of pyrite in aerated cyanide solutions and the preg-robbing of pyrite especially at a higher coating thickness.     

Environmental impacts from mining at Taojiang Mn ore deposit, central Hunan, China

The Taojiang Mn ore deposit was exploited in the early 1960s, and waste rocks were developed since then. Because the Mn ores were hosted within the metal-enriched black shales （Peng et al., 2004）, the continuous mining has led to the exposure of an immense quality of black shales, which might cause serious impacts on environments. The present study deals with this environmental issue with samples from the waste rocks, and from the surrounding soils and surface water. The mineralogy of the waste rock was studied using EMPA, then a large number of elements in all waste rock, soil, and water samples were analyzed at a wide range of concentrations with high accuracy using an Elan6000 ICP-MS machine at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The waste rock is composed mostly of black shales, with minor Mn carbonates. Both black shales and Mn carbonates of the waste rock contain many sulfide minerals, mainly pyrite, with minor galena, sphalerite, chalcopyrite, and others. The waste rocks are enriched in many metals including Sc, V, Cr, Co, Ni, Fe, Mn, Cu, Zn, Pb, Th, U, Mo, Sb, Sn, Tl, and others, and the metals are mostly hosted within the sulfides. Weathering of waste rocks might cause emission of the following metals： V, Cd, Ni, Th, U, Mo, Sb, Tl, Sc, Cr, Cu, Zn, Sn, and minor Co, and Pb. The surrounding soils are highly enriched in Cr, Co, Cu, Zn, Mn, Mo, Cd, Tl, and Pb, with the enrichment factors of 2.67.3.8, 7.26, 7.27, 8.2, 5.7, 13, and 5.4, respectively. The element ratios （Rb/Cs, Fe/Mn, Nb/Zr, Hf/Zr, and Ba/Sr） and REE distribution patterns of the soils are similar to those of the waste rocks and bedrocks.     

The Ore-forming Fluid of the Gold Deposits of Muru Gold Belt in Eastern Shandong, China - a Case Study of Denggezhuang Gold Deposit

Abstract. Denggezhuang gold deposit is an epithermal gold‐quartz vein deposit in northern Muru gold belt, eastern Shandong, China. The deposit occurs in the NNE‐striking faults within the Mesozoic granite. The deposit consists of four major veins with a general NNE‐strike. Based on crosscutting relationships and mineral parageneses, the veins appear to have been formed during the same mineralization epochs, and are further divided into three stages: (1) massive barren quartz veins; (2) quartz‐sulfides veins; (3) late, pure quartz or calcite veinlets. Most gold mineralization is associated with the second stage. The early stage is characterized by quartz, and small amounts of ore minerals (pyrite), the second stage is characterized by large amounts of ore minerals. Fluid inclusions in vein quartz contain C‐H‐O fluids of variable compositions. Three main types of fluid inclusions are recognized at room temperature: type I, two‐phase, aqueous vapor and an aqueous liquid phase (L+V); type II, aqueous‐carbonic inclusions, a CC₂‐liquid with/without vapor and aqueous liquid (LCO₂+VCC₂+Laq.); type III, mono‐phase aqueous liquid (Laq.). Data from fluid inclusion distribution, microthermometry, and gas analysis indicate that fluids associated with Au mineralized quartz veins (stage 2) have moderate salinity ranging from 1.91 to 16.43 wt% NaCl equivalent (modeled salinity around 8–10 wt% NaCl equiv.). These veins formatted at temperatures from 80d? to 280d?C. Fluids associated with barren quartz veins (stage 3) have a low salinity of about 1.91 to 2.57 wt% NaCl equivalent and lower temperature. There is evidence of fluid immiscibility and boiling in ore‐forming stages. Stable isotope analyses of quartz indicate that the veins were deposited by waters with δ^O and δD values ranging from those of magmatic water to typical meteoric water. The gold metallogenesis of Muru gold belt has no relationship with the granite, and formed during the late stage of the crust thinning of North China.     

Origin of fluids in iron oxide–copper–gold deposits: constraints from δ 37Cl, 87Sr/86Sri and Cl/Br

The origin of the hypersaline fluids (magmatic or basinal brine?), associated with iron oxide (Cu–U–Au–REE) deposits, is controversial. We report the first chlorine and strontium isotope data combined with Cl/Br ratios of fluid inclusions from selected iron oxide–copper–gold (IOCG) deposits (Candelaria, Raúl–Condestable, Sossego), a deposit considered to represent a magmatic end member of the IOCG class of deposit (Gameleira), and a magnetite–apatite deposit (El Romeral) from South America. Our data indicate mixing of a high δ ³⁷Cl magmatic fluid with near 0‰ δ ³⁷Cl basinal brines in the Candelaria, Raúl–Condestable, and Sossego IOCG deposits and leaching of a few weight percent of evaporites by magmatic-hydrothermal (?) fluids at Gameleira and El Romeral. The Sr isotopic composition of the inclusion fluids of Candelaria, Raúl–Condestable, and El Romeral confirms the presence of a non-magmatic fluid component in these deposits. The heavy chlorine isotope signatures of fluids from the IOCG deposits (Candelaria, Raúl–Condestable, Sossego), reflecting the magmatic-hydrothermal component of these fluids, contrast with the near 0‰ δ ³⁷Cl values of porphyry copper fluids known from the literature. The heavy chlorine isotope compositions of fluids of the investigated IOCG deposits may indicate a prevailing mantle Cl component in contrast to porphyry copper fluids, an argument also supported by Os isotopes, or could result from differential Cl isotope fractionation processes (e.g. phase separation) in fluids of IOCG and porphyry Cu deposits.     

Gold mining in Ghana's forest reserves: a report on the current debate

This paper examines the debate surrounding a recent decision made by the Ghanaian government to permit gold exploration – and potentially, mining – in 'protected' forest reserves. In 2001, four mining companies were awarded mineral exploration concessions in forested regions of the country, and have since put forward applications to mine for gold. Notwithstanding the sharp divide in opinion on the issue, the continued uncertainty surrounding the implications of the proposed activities makes further research on the ground imperative in the short term. Work aiming to elicit indigenous perspectives on the projects, as well as research that facilitates dialogue between and/or among stakeholder parties, should be prioritized.     

鄂尔多斯盆地北部底河道砂岩型铀矿地质特征

鄂尔多斯盆地北部直罗组中的铀矿,是典型的产于河道中的砂岩铀矿,该矿床发育较好的卷状矿体。通过对该铀矿地质特征的研究,认识到发育卷状矿体的底河道砂岩型铀矿必须具备两大条件:其一是成矿砂体条件,即砂体要有较好的成层性、连通性和渗透性;其二是地层结构条件,即砂体必须存在较好的上、下隔水岩层。就砂体而言,河流相辫状沉积砂体是形成卷状矿体的主要砂体,并且以具有从辫状河向曲流河完整演化的辫状沉积砂体较好。砂体的上、下隔水岩层则有多种表现形式:下隔水层可由不透水的基岩或湖相沉积泥岩等构成;上隔水层由不透水的湖相泥岩、曲流沉积地层或岩浆岩等构成。在层间氧化作用过程上,存在纵横两个方向的氧化,即存在与河道方向一致的纵向氧化和与河道垂直的横向氧化,两种氧化作用成矿常叠加形成复杂的矿体类型;在矿化赋存的部位上,铀砂体通常发育在基底之上或不同建造之间;在古气候演变上,成矿作用发生在干旱气候条件下,或由潮湿向干旱的气候转变阶段。     

深部找铀及湘南-桂北地区深部找铀潜景分析

概述了国内外深部找矿的研究成果,指出深部找矿是当今发展的趋势。国内外重大矿产的成功发掘,其深度均在千米以上,铀矿化垂向分布深度可达4 km以上。综合介绍了国内外勘查深大矿床的特点和条件,认为岩石-构造条件是深部矿化定位的重要因素,复式岩体、成矿系统的垂向变化、构造地球物理-地球化学异常模型是深部找矿的关键依据。综述了中国南方湘南—桂北地区深部找铀的有利地质构造条件和潜力,成矿流体是该区铀矿化的根源,白垩—第三纪重大地质事件是该区深部铀成矿的重要前提,重大地质事件引发的NE-NNE,NW向深大断裂及断陷盆地是铀矿化赋存的重要场所和勘查靶区。在已知铀矿田、成矿带勘查范围基础上,在该区进行深部探索将会获得重大突破。探讨了湘南—桂北地区深部找铀的勘查思路和方法。     

陕西金矿床类型及其找矿方向

通过对陕西金矿资源的分析、总结,将陕西金矿成因类型划分为7类14亚类;与金矿有关的成矿系列划分为3个矿床成矿系列组合,7个成矿系列类型,10个成矿系列和4个亚系列;金矿床空间分布严格受隐伏基底和出露基底,隐伏岩体、重磁吻合构造,构造和成矿时代的控制;与金成矿有关的Ⅲ级成矿区(带)有4条,有关的Ⅳ级成矿区(带)有10条,有关的Ⅴ级主要金成矿区(带)有16条;提出了金矿新的找矿方向,为今后本区金矿地质找矿的新突破提供信息.