山东河东金矿成矿地质特征

河东金矿床矿体呈完整、连续的透镜体,具有典型的中温热液矿物组合和围岩蚀变分带特征。区内金矿床矿石同位素组成特征表明,成矿物质来源于胶东群。从成矿溶液组分与性质、金的迁移与富集以及多阶段成矿过程等方面探讨了该矿床的成矿机理,矿床属中温岩浆热液裂隙充填交代型金矿床     

从铀系列同位素角度探讨砂岩型铀矿的形成过程及找矿标志

本文通过对512矿床含矿层不同地段铀系列同位素研究,对砂岩型铀矿的形成过程及找矿标志进行了探讨,根据矿卷前锋铀系列同位素组成分布规律和含矿层不同氧化还原分带中样品铀系列同位素分布特征,认为砂岩型铀矿含矿层岩石的铀系列同位素组成分区特征不仅可以记录铀富集的滚动成矿过程,而且可以作为预测铀矿化的重要找矿标志依据,A区应定名为"氧化还原矛盾区"较为合适.     

内蒙古迪彦钦阿木斑岩钼矿床成矿流体的出溶、演化及对成矿的制约

迪彦钦阿木钼矿床位于内蒙古东乌旗地区,矿区侵入岩不发育,主要为细粒正长岩和基性岩脉,矿体主要发育在侏罗纪火山岩中,少量发育在细粒正长岩中,主要矿化类型为细网脉状、脉状、浸染状,具有斑岩型矿化特征。矿区的细粒正长岩中可见含矿石英-钾长石囊团或由之构成中心相的热液脉体,是岩浆-流体转化过程的直接证据。本文在详细岩相学观察的基础上,对石英-钾长石囊团中主要组成矿物开展了阴极发光图像分析,对石英、萤石中流体包裹体开展了显微测温实验,并借助SEM/EDS、显微激光拉曼探针、LA-ICP-MS等手段对包裹体成分进行了系统分析,基于以上实验结果对岩浆流体的出溶过程、出溶流体特征及矿质沉淀机制进行了探讨。研究结果表明,矿区钼成矿与细粒正长岩岩浆出溶流体有关;富F和挥发分造成成矿岩浆具有低的固相线温度和较低的黏度,因此成矿岩浆可以沿断裂快速上侵到地壳浅部;岩浆上侵过程中的减压沸腾可能是流体出溶的主要机制;早期出溶流体为富F和富CO₂的中高温(227～457℃)、中低盐度[w(NaCl_eq)=0.3%～8.6%]流体,由于快速减压造成流体沸腾形成低盐度富CO     

四川盆地东北部砂岩型铀矿石及铀的存在形式特征研究

四川盆地东北部砂岩型铀矿含铀层位为下白垩统苍溪组,主要矿化产在苍溪组第一韵律层下部砂岩或砾岩层中.岩矿鉴定表明,主要含矿岩性为细—中粒砂岩,砂岩矿物碎屑主要为石英,胶结物主要为方解石,含少量黄铁矿.扫描电镜和电子探针分析表明,含矿岩石中除了矿物碎屑石英、胶结物方解石和黄铁矿外,还含有钛铁矿、方铅矿和铀石.铀石为岩石中铀...     

西南天山中—新生界层控砂砾岩型铜铅锌矿成矿规律

西南天山是新疆中—新生界层控砂砾岩型铜铅锌矿的重要产出地区,以萨热克铜矿、乌拉根铅锌矿、花园铜矿、伽师铜矿为代表,均产于隆起剥蚀区边缘的红层盆地中并严格受层位控制,赋矿盆地的下部为煤系生烃岩,中部为渗透性良好的砂砾岩铜铅锌矿储集层,上覆膏岩及泥岩等密闭盖层,具有铜铅锌-铀-煤-天然气同盆共存富集的成矿特征。文章总结了西南天山赋矿盆地沉积-构造演化及赋矿层位特征,研究了铜铅锌典型矿床的控矿条件和成矿作用特征。通过对比分析,总结了中—新生界砂砾岩型铜铅锌矿的区域成矿规律,认为有机质与铜铅锌成矿关系密切,推测在原始矿源层的基础上,在隆起部位经油田卤水叠加形成铜铅锌贫矿体,喜马拉雅期断裂构造沟通深源成矿流体再次叠加形成铜铅锌富矿体。总结构建了西南天山中—新生界层控砂砾岩型铜铅锌矿的成矿模式,以期为已知矿山深边部勘查及区域找矿工作部署提供依据。     

湖南仁里稀有金属矿床岩相学和矿物学特征及其地质意义——以5号脉ZK708号钻孔为例

仁里矿床是中国近年新发现的超大型花岗伟晶岩型稀有金属矿床,文章针对其稀有金属矿化富集规律、成岩成矿演化特征及找矿标志等问题,以5号主矿脉钻孔ZK708全孔岩芯及岩体内、外伟晶岩为研究对象,采用了电子探针、能谱仪分析和全岩地球化学分析等方法,开展了伟晶岩岩相学、矿物学及地球化学等方面的研究工作.研究结果表明:①仁里矿床伟...     

Geodynamic modelling of the Century deposit,Mt Isa Province,Queensland

This paper is concerned with an example of quantitative modelling of orebody formation as a guide to reducing the risk for future mineral exploration. Specifically, the paper presents a detailed 3–D numerical model for the formation of the Century zinc deposit in northern Queensland. The model couples fluid flow with deformation, thermal transport and chemical reactions. The emphasis of the study is a systems approach where the holistic mineralising system is considered rather than concentrating solely on the mineral deposit. In so doing the complete plumbing system for mineralisation is considered with a view to specifying the critical conditions responsible for the ore deposit occurring where it does and having the size and metal grades that are observed. The numerical model is based on detailed geological, tectonic, isotopic and mineralogical data collected over the past 20 years. The conclusions are that the Century zinc deposit is located where it is because of the following factors: (i) a thermal anomaly is associated with the Termite Range Fault due to advection of heat from depth by fluid flow up the Termite Range Fault; (ii) bedding‐plane fissility in the shale rocks hosting the Century zinc deposit has controlled the wavelength and nature of D₁ folding in the vicinity of the deposit and has also controlled increases in permeability due to hydrofracture of the shales; such hydrofracture is also associated with the production of hydrocarbons as these shales passed through the ‘oil‐window’; (iii) Pb–Zn leached from crustal rocks in the stratigraphic column migrated up along faults normal to the Termite Range Fault driven by topographic relief associated with inversion at the end of the Isan Orogeny; these fluids mixed with H₂S derived at depth moving up the Termite Range Fault to mix with the crustal fluids to precipitate Pb–Zn in a plume downstream from the point of mixing. Critical factors to be used as exploration guides are high temperatures, carbonaceous fissile shales now folded into relatively tight D₁ folds, fault‐controlled plumbing systems that enable fluid mixing, depletion of metals upstream of the deposit and,in particular,a very wide Fe‐depletion halo upstream of the deposit.     

Silurian and Devonian systems

The Ediacara mineral field is situated 30 km W of Beltana on the western margins of the Flinders Ranges, South Australia, and consists of silver‐lead and copper deposits in lower Cambrian carbonate rocks that contain anomalous base‐metal contents throughout the Adelaide Geosyncline. The lower Cambrian rocks, which consist of the basal Parachilna Formation and overlying Ajax Limestone, rest disconformably on the Precambrian, and at Ediacara occupy a shallow N‐S elongate syncline near the hinge zone of the Adelaide Geosyncline. The main primary ore minerals of the silver‐lead mineralization are galena and pyrite, with very minor chalcopyrite and sphalerite, and rare tetrahedrite and pearceite. The gangue consists mainly of silica (both chalcedony and quartz), with minor dolomite and rare barite. The mineralization is stratabound and occurs in conformable zones, the lowest of which commences about 30–50 m above the base of the Cambrian sequence. The host to the silver‐lead mineralization, the Ajax Limestone, can be subdivided into three units which represent a set of lithologies, structures and organic traces indicative of a shallow near‐shore carbonate environment. The silver‐lead mineralization is mainly present in sandy and laminated dolomites which were deposited in an environment ranging from sub‐tidal to bar and channel and tidal flat, respectively. Four types of mineralization have been recognized; disseminated sulphides of syngenetic and/or diagenetic origin and epigenetic concentrations along stylolites, in veins and as breccia fillings. Post‐depositional solution activity has affected a large proportion of the carbonate sequence. The effects of this activity range from stylolites through stylobreccias to solution collapse breccias. The epigenetic concentrations of mineralizations have apparently been formed by the remobilization of the disseminated sulphides during solution activity. The ore and gangue minerals of the epigenetic mineralization display both euhedral forms and distinct colloform banding, and framboidal textures have also been observed in both pyrite and galena. There is evidence of repeated episodic precipitation and no simple paragenetic sequence can be recognized. Fluid inclusions in silica and dolomite associated with the epigenetic mineralization have homogenization temperatures of 159 to 199°C and freezing temperatures that indicate the fluids to be saline brines containing NaCl with CaCl₂ and/or MgCl₂. Sulphur isotope analyses show a range of 8³⁴S values from ‐12.5 to +8.6 per mil, with no evidence of significant differences between the four types of mineralization. The data suggest deposition of the disseminated sulphides as a result of biological reduction of seawater sulphate in a system partially open with respect to sulphate supply. Subsequent remobilization of sulphides apparently involved little or no sulphur isotope fractionation. The Ediacara silver‐lead deposits have many features in common with Mississippi Valley‐type lead‐zinc deposits and appear to have similarities in terms of genesis, in that the epigenetic mineralization has been formed as a result of post‐depositional solution activity during diagenesis in a sedimentary basin. The scale of transport of the metals deposited as the epigenetic mineralization at Ediacara appears, however, to have been very much less than that of the metals in other Mississippi Valley‐type deposits.     

Genetic and ore-forming ages of the Fe–P–(Ti) oxide deposits associated with mafic–ultramafic–carbonatite complexes in the Kuluketage block,NW China

Abstract

During the past 50 years, many geological and ore-deposit investigations have led to the discovery of the Fe–P–(Ti)-oxide deposits associated with mafic–ultramafic–carbonatite complexes in the Kuluketage block, northeastern Tarim Craton. In this paper, we discuss the genetic and ore-forming ages, tectonic setting, and the genesis of these deposits (Kawuliuke, Qieganbulake and Duosike). LA-ICP-MS zircon U–Pb dating yielded a weighted mean ²⁰⁶Pb/²³⁸U ages of 811?±?5?Ma, 811?±?4?Ma, and 840?±?5?Ma for Kawuliuke ore-bearing pyroxenite, Qieganbulake gabbro and Duosike ore-bearing pyroxenite, respectively. The CL images of the Kawuliuke apatite grains show core–rim structure, suggesting multi-phase crystallisation, whereas the apatite grains from Qieganbulake and Dusike deposits do not show any core–rim texture, suggesting a single-stage crystallisation. LA-ICP-MS apatite ²⁰⁷Pb-corrected U–Pb dating provided weighted mean ²⁰⁶Pb/²³⁸U ages of 814?±?21?Ma and 771?±?8?Ma for the Kawuliuke ores, and 810?±?7?Ma and 841?±?7?Ma for Qieganbulake and Duosike ores, respectively. The core–rim texture in apatite by CL imaging as well as two different ore-forming ages in the core and rim of the apatite indicate two metallogenic events for the Kawuliuke deposit. The first metallogenic period was magmatic in origin, and the second period was hydrothermal in origin. The initial ore-forming age of the Kawuliuke Fe–P–Ti mineralisation was ca 814?Ma and the second one was ca 771?Ma. On the other hand, the ore-forming ages of the Qieganbulake and Duosike deposits were ca 810?Ma and ca 841?Ma, respectively. Qieganbulake and Duosike deposits were of magmatic origin. Combined with previous geochronological data and the research on the tectonic background, we infer that the Kawuliuke, Qieganbulake and Duosike Fe–P–(Ti)-oxide deposits were formed in a subduction-related tectonic setting and were the product of subduction-related magmatism.     

论辽宁锦西杨家杖子杂岩体的岩浆成因演化及成矿作用

杨家杖子杂岩体中的二长闪长岩代表一种母岩浆,它是燕山早期库拉板块向欧亚板块下俯冲所产生的,并汇聚上升的安山质岩浆。粗粒似斑状二长花岗岩、细粒似斑状二长花岗岩和(碱长)花岗斑岩是二长闪长岩浆在7km深、弱还原环境、氧逸度为10~(-8)～10~(-10)Pa、1200°～1250℃的岩浆房中经结晶分异作用的派生物。以后,这些岩浆相继上侵,定位于2.5km深处。由这些岩浆岩侵入体所引起的镁夕卡岩、钙夕卡岩和岩浆期后酸性热液淋滤蚀变非常发育。只有来自细粒似斑状二长花岗岩和(碱长)花岗斑岩岩浆、富含Mo的酸性热液沿着裂隙侵入夕卡岩中,在240～330℃时,才形成Mo矿床。此种酸性热液也沿着裂隙侵入细粒似斑状二长花岗岩和(碱长)花岗斑岩中,而形成细脉浸染Mo矿床。因此,杨家杖子Mo矿床属于斑岩-夕卡岩型。