湘东某铁帽型金银矿床特征与成因探讨

湘东某铁帽型金银矿床,位于某多金属矿床中部,受一压扭性走向断裂及潜水面控制.主矿体赋存在印支期花岗班岩与下石炭统大塘阶页岩或砾岩的接触面上。矿区处于亚热带潮湿气候的低山丘陵区,氧化带比较发育,矿区中部氧化带深度较大。含金银的硫化矿体经风化剥蚀裸露地表,一些元素淋漓、迁移、流失,另一些元素残余富集,金、银极其稳定,附着在铁矿物的裂隙、空洞、晶隙中,或被吸附在粘土矿物表面,形成金银矿体。     

木里新山铁帽地质特征及其原生铜矿床远景预测

木里新山在地质构造上处于扬子地台西缘推覆弧形构造带上的一个穹窿中,地表出露有许多褐铁矿体,规模很大。本文认为这些铁帽由原生铜矿床氧化形成,且与李伍铜矿具有相同的成矿地质环境和类似的矿床地质特征,预测铁帽的下部,可能存在一中至大型的原生铜矿床。     

The geochemistry of gossans associated with Sarcheshmeh porphyry copper deposit,Rafsanjan, Kerman,Iran: Implications for exploration and the environment

The Sarcheshmeh copper deposit is one of the world's largest Oligo-Miocene porphyry copper deposits in a continental arc setting with a well developed supergene sulfide zone, covered mainly by a hematitic gossan. Supergene oxidation and leaching, have developed a chalcocite enrichment blanket averaging 1.99% Cu, more than twice that of hypogene zone (0.89% Cu). The mature gossans overlying the Sarcheshmeh porphyry copper ores contain abundant hematite with variable amounts of goethite and jarosite, whereas immature gossans consist of iron-oxides, malachite, azurite and chrysocolla. In mature gossans, Au, Mo and Ag give significant anomalies much higher than the background concentrations. However, Cu has been leached in mature gossans and gives values close or even less than the normal or crustal content (< 36.7 ppm). Immature gossans are enriched in Cu (160.3 ppm), Zn (826.7 ppm), and Pb (88.6 ppm). Jarosite- and goethite-bearing gossans may have developed over the pyritic shell of most Iranian porphyry copper deposits with pyrite–chalcopyrite ratios greater than 10 and therefore, do not necessarily indicate a promising sulfide-enriched ore (Kader and Ijo). Hematite-bearing gossans overlying nonreactive alteration halos with pyrite–chalcopyrite ratios about 1.5 and quartz stringers have significant supergene sulfide ores (Sarcheshmeh and Miduk). The copper grade in supergene sulfide zone of Sarcheshmeh copper deposit ranges from 0.78% in propylitized rocks to 3.4% in sericitized volcanic rocks, corresponding to the increasing chalcopyrite–pyrite or chalcocite–pyrite ratios from 0.3 to 3, respectively. Immature gossans with dominant malachite and chrysocolla associated with jarosite and goethite give the most weakly developed enrichment zone, as at God-e-Kolvari. The average anomalous values of Au (59.6 ppb), Mo (42.5 ppm) and Ag (2.6 ppm) in mature gossans associated with the Sarcheshmeh copper mine may be a criterion that provides a significant exploration target for regional metallogenic blind porphyry ore districts in central Iranian volcano–plutonic continental arc settings. Drilling for new porphyry ores should be targeted where hematitic gossans are well developed. The ongoing gossan formation may result in natural acidic rock drainage (ARD).     

Metavolcanic host rocks,mineralization, and gossans of the Shaib al Tair and Rabathan volcanogenic massive sulphide deposits of the Wadi Bidah Mineral District,Saudi Arabia

The Wadi Bidah Mineral District of Saudi Arabia contains more than 16 small outcropping stratabound volcanogenic Cu–Zn–(Pb) ± Au-bearing massive sulphide deposits and associated zones of hydrothermal alteration. Here, we use major and trace element analyses of massive sulphides, gossans, and hydrothermally altered and least altered metamorphosed host rock (schist) from two of the deposits (Shaib al Tair and Rabathan) to interpret the geochemical and petrological evolution of the host rocks and gossanization of the mineralization. Tectonic interpretations utilize high-field-strength elements, including the rare earth elements (REE), because they are relatively immobile during hydrothermal alteration, low-grade metamorphism, and supergene weathering and therefore are useful in constraining the source, composition, and physicochemical parameters of the primary igneous rocks, the mineralizing hydrothermal fluid and subsequent supergene weathering processes. Positive Eu anomalies in some of the massive sulphide samples are consistent with a high temperature (>250°C) hydrothermal origin, consistent with the Cu contents (up to 2 wt.%) of the massive sulphides. The REE profiles of the gossans are topologically similar to nearby hydrothermally altered felsic schists (light REE (LREE)-enriched to concave-up REE profiles, with or without positive Eu anomalies) suggesting that the REE experienced little fractionation during metamorphism or supergene weathering. Hydrothermally altered rocks (now schists) close to the massive sulphide deposits have high base metals and Ba contents and have concave-up REE patterns, in contrast to the least altered host rocks, consistent with greater mobility of the middle REE compared to the light and heavy REE during hydrothermal alteration. The gossans are interpreted to represent relict massive sulphides that have undergone supergene weathering; ‘chert’ beds within these massive sulphide deposits may be leached wall-rock gossans that experienced silicification and Pb–Ba–Fe enrichment from acidic groundwaters generated during gossan formation.     

耳泽古溶洞中的菱铁矿—铁帽型金矿床的地质特征

四川木里耳泽金矿分布于上二叠统岗达概组大理岩中,矿带受此唤背斜轴部的破碎带控制。矿床面积约1.1km~2,矿体形态复杂,与围岩呈不规则接触。矿石分为原生含金黄铁矿—菱铁矿型和铁帽型两大类。主要金矿物是自然金,次为银金矿。金来源于岗达概组大理岩和下伏火山岩。成矿地下热水主要为大气降水与变质水混合而成。成矿环境稳定,经间歇性的抬升运动、岩溶作用形成溶洞。先在溶洞中形成含金黄铁矿—菱铁矿石,再表生氧化形成铁帽型金矿。     

铁帽型金矿中黄铁矿与褐铁矿含金量的测定

利用分散分析－浮选－选择溶解相结合的方法，分离了铁帽型金矿中两种主要载金矿物──褐铁矿和黄铁矿，然后根据已分离矿物的矿物量及含金量计算出金在各矿物中的配分，解决了物相分析测定金在氧化铁矿物与硫化铁矿物中配分的难题。     

高植被覆盖区遥感找锰矿实验研究——以桂西—滇东南的下雷—大新地区为例

桂西—滇东南区域植被覆盖茂盛,高覆盖的植被遥感信息相对于地质遥感信息而言是一个很强的干扰。本文以桂西—滇东南的锰矿化信息较为丰富、植被覆盖度高的下雷—大新区域TM遥感影像为例,利用基于主成分变换的铁染遥感异常信息、羟基异常信息和泥岩碳酸岩异常遥感信息提取,以及基于SAM和实地地物光谱测量的基础上提取的氧化锰露头的遥感信息,研究结果与已知锰矿化信息的空间分布区域有较高的吻合度。研究结果表明,本文的研究方法对于遥感找锰矿的宏观靶区框选有较高的参考价值。     

安徽省铁帽型金银矿床地质特征、成矿条件及其评价准则研究

安徽省铁帽型金、银矿床在全国发现比较早,分布广,并且有一定规律,工业利用程度高,效益好。铁帽型金、银矿广泛产于各类型原生含Au、Ag硫化矿床的氧化带,以产于石炭系层状含(Cu)硫化矿床的上部氧化次生富集带规模较大,品位富。本次积累完整的矿床地质特征资料,探索矿床分类、氧化分带,研究金、银的赋矿规律和成矿条件,总结找矿标志和评价准则。     

通化地区铁帽含金性定量评价

通化地区早元古宙集安群变质岩系中,分布着众多的铁帽,其含金量各异。本文在地质、物探资料综合解释的基础上,分析了控矿铁帽产出的地质条件,对铁帽中的金等元素组合做了统计分析,以数量化理论划分了三种铁帽类型,其中含钒、钛的铁帽,系铁质岩石氧化而成,为假铁帽与金矿无关;铅、锌硫化物的铁帽也与金矿无关;而含铜硫化物铁帽则含金较高,具有指示找金的意义。     

河北省宽城县沙窝店地区地质-地球物理特征及找硫铁矿效果

矿区内铁帽发育,矿化特征明显,含矿层和黄铁矿体在电性上与围岩之间存在着明显的电性差异,采用时间域激发极化法和视电阻率法等综合物探方法深部找矿,共发现有意义异常五处。结合地质、钻探资料认为它们分别是由黄铁矿体、规模较小（连续性较差）的矿化体及碳质页岩引起的异常,说明运用综合物探,结合地质进行深部找矿效果明显。