云南砂金矿床的成因类型及其找矿前景

在研究云南的残坡堆积、洪积、冲积和冰碛等砂金矿床类型的成矿作用和成矿环境的基础上,总结了云南砂金矿床地质特征。分析了砂金矿床主要受深大断裂或大断裂、地层岩石、地貌、水系和水化学环境的综合因素控制,探讨了金沙江、珠江、红河、澜沧江、怒江和伊洛瓦底江等6大水系砂金成矿条件和找矿前景预测。     

甘肃省礼县田家河砂金矿床地质特征及富集规律

阐述了甘肃省礼县田家河一带砂金矿床的地质特征、第四系地质、地貌条件与成矿特征,分析了各类型松散堆积物的成因、分布特征,对砂金的富集规律和成矿特征进行了总结,通过对混合砂含砾率、砾石度、含泥量等进行了测定,对矿体厚度、品位在纵向上、垂向上的变化特征进行了分析。探讨了成矿物质来源、砂金富集部位和补给方向及搬运距离。田家河砂金矿床产于第四系全新统河床相及河漫滩相中,成因类型属河流冲积型,形态类型属河床、河漫滩型,成矿时代为第四纪全新统;全新世开始,地壳上升幅度极小,河流侧蚀作用增强,使含金地质体和各级阶地的剥蚀物被搬运、分选,并在谷底堆积形成田家河砂金矿。该砂金矿的发现和评价为该区寻找相似类型的砂金矿床提供了找矿标志和找矿模式。     

印度尼西亚苏门答腊LOGAS砂金矿床地质特征

印度尼西亚砂金资源丰富。ＬＯＧＡＳ金矿床是印尼重要砂金矿床之一。它位于苏门答腊金银溅金属成矿带的宽坦河流域的准平原化河谷堆积地带。砂金矿受水系，中低山地形地貌格局和金物质来源的控制，赋存在特定的Ｑａｔ河流阶地和Ｑｔｐｕ层位砂砾层中，层位稳定，矿床埋深５～１２ｍ，砂金品位０．１３１～０．２３５ｇ／ｍ３。     

“金三角”地区砂金矿富集规律及成矿模式研究

"金三角"地区砂金矿主要分布于6个岩金矿集中区附近,勉县-平武深大断裂带附近,NW-NNW向次级裂隙带与主干深大断裂带的交汇部位,本区西北部的中低山区向东南部的低山丘陵区转换的部位,支流与干流交汇部位的下方,石英脉发育地区附近的水系中;成矿模式是高含金地质体→外动力改造高含金地质体,使金物质脱离母体呈显粒金、胶体金、悬浮金以及离子金等形式→由高位搬运迁移到沟谷水系中,迁移过程中显微粒金可有部分转化为显粒金→在沟谷水系中沉积成矿→再改造进行搬运迁移到现在的位置形成规模砂金矿床.     

塔吉克斯坦主要岩金矿床

塔吉克斯坦岩金矿床分布于塔国中部、北部和帕米尔地区,主要集中在泽拉夫尚河流域.工业类型为单一型与伴生型金矿床,成因上多与岩浆岩(花岗岩、花岗闪长岩和闪长岩等)有关,金矿床主要发育于与岩浆有关的石英脉内.按产状可分为:塔罗型、吉劳型、乔列型和丘利博伊型4种,其中吉劳金矿为典型的大型网脉状金矿床.     

黑龙江省多年冻土地区砂金矿床的水文地质特征

本文阐述了黑龙江省北部多年冻土地区河流冲积砂金矿床的冻土类型,分布规律和含水层划分,概述了矿床水文地质特点。     

塞拉利昂中部马卡利地区金矿特征及成矿远景

塞拉利昂中部马卡利地区出露有大片的太古界花岗-绿岩带地质体,其金矿资源丰富。通过矿产勘查和成矿规律研究表明,金的来源与太古界花岗-绿岩带地体密切相关。岩金矿床类型为含铁建造金矿床,主要赋存于绿岩带的绿片岩中及含铁建造的片岩中,受褶皱和断裂构造控制;砂金矿的类型为河流冲积型砂金矿,主要分布在花岗-绿岩带内及其周边河流中的全新统冲积层中下部砂砾石层中。重砂异常和地球化学异常区内具备良好的岩金、砂金成矿地质背景和找矿前景,实施砂金-岩金综合找矿方法,找矿潜力巨大。     

陇南地区区域砂金成矿特点及找矿方向

从金源、构造演化、河流水系的分布、水动力学条件等的分析,认为陇南地区现代砂金矿的空间分布总体方向是受区域深断裂控制,金源层及含金建造的出露与剥离以及河流水系的分布情况对圈定砂金成矿远景区起着决定性的作用。根据砂金的区域成矿特点,认为平行临潭—凤县深断裂分布的碌曲、宕昌、两当槽形沉降带的北缘,甘肃东南部嘉陵江流域的西汉水、白龙江、燕子河、白水江等水系,金源充足、河流流程长,流域面积广,地形地貌条件有利,所以具有较好的成矿远景,而渭河流域成矿条件则较差。     

玻利维亚的矿产资源及开发前景

玻利维亚是矿物原料出口国,锡和钨的生产在世界上占重要地位.砂金矿的开采主要集中在拉巴斯省,砂金矿床星罗棋布,品位较富.主要为现代河流冲积砂金矿,可分为河床、河漫滩和阶地3种砂金矿床类型.玻利维亚政府鼓励外商投资,目前矿业开发投资以砂金开采为首选.     

玻利维亚的矿产资源及开发前景

玻利维亚是矿物原料出口国，锡和钨的生产在世界上占重要地位。砂金矿的开采主要集中在拉巴斯省，砂金矿床星罗棋布，品位较富。主要为现代河流冲积砂金矿，可分为河床、河漫滩和阶地3种砂金矿床类型。玻利维亚政府鼓励外商投资，目前矿业开发投资以砂金开采为首选。     

云南红河三家河地区第四纪地质及其与砂金成矿关系研究

热带，亚热带气候，强烈切割的三家河地区的第四纪地质作用对三家河流域内砂金矿的形成具有直接意义，其砂金矿床类型，富集规律，成矿期次及矿床的工业意义均是第四纪地质作用的体现。     

River drainage reorientation during placer gold accumulation, southern New Zealand

Many alluvial placer deposits around the world occur in river systems that have been affected by tectonic events, causing drainage reorientation and severance of links between placers and their sources. This study documents tectonic rejuvenation of topography in the Otago giant placer goldfield, New Zealand, which has resulted in numerous river capture and drainage reorientation events. These events have induced changes to gold transport directions and numerous stages of separation of detrital gold from primary sources. Goldfield-wide reconstructions of drainage patterns through time are as yet only possible for Miocene–Recent, and numerous earlier drainage changes back to Cretaceous primary orogenic mineralisation are probable. Variations in basement lithologies permit auriferous gravel provenance determinations, facilitating paleodrainage pattern reconstruction and documentation of river capture events. River capture events and timing of these events for gold-bearing paleodrainages have also been documented using genetic divergences of populations of freshwater galaxiid fish that were isolated by drainage reorientation. Gold-bearing quartz pebble conglomerates had a southeastward drainage in the Miocene. This was disrupted in the Pliocene by mountain range uplift and gold placer recycling, with deposition of lithic conglomerates containing only minor gold placers. The most dramatic changes in gold transport directions occurred through the Quaternary, as antiformal ranges grew across the pre-existing drainages. Miocene and Pliocene placers were recycled with numerous local (1–10 km scale) changes in river directions and numerous capture events. Large axial rivers were segmented into a more complex drainage pattern, and on-going river capture resulted in growth of the main Clutha River catchment at the expense of neighbouring catchments. The most productive placers developed in the Clutha River in late Quaternary when increased discharge from captured mountain catchments enhanced gold transport and concentration. Similar river drainage reorientation has occurred in other placer fields around the world, but the lack of preserved evidence inhibits documentation of most such changes.     

Alluvial gold placers directly related to primary sources: An important forecast criterion

Two extreme groups of alluvial gold placers (lost and preserved “live” relation to the primary sources) are distinguished by the character of this relation and mineralogical-geochemical peculiarities. The content of the invisible gold in the first ones is close to the regional background (first mg/t) in contrast to its anomalous (exceeding the local background for several orders of magnitude) amount in placers of the second type. The invisible gold composes the geochemical dispersion flows combined with the placer. The placers of this type are important forecast criterion of the assessment of the nearby areas for the primary gold.     

内蒙古虎拉林地区砂金与岩金的关系

虎拉林地区砂、岩金矿的空间位置关系十分密切。在虎拉林河上中下游及虎拉林岩金矿分别采取样品，结果表明虎拉林河砂金粒度大，分选较差，磨圆度差；砂金形态总体上以粒状为主；溶蚀系数均值小于1。微量元素含量特征表明砂金的主要物质来源是近源，与岩金矿关系密切且具有继承性。虎拉林岩金矿床的矿石中自然金颗粒粗大，矿体的上部遭到剥蚀，虎拉林河砂金主要来源于虎拉林岩金矿床，砂金可作为岩金的找矿标志。自然金化学-结晶温度图表明砂金的原生Au源为中低温热液矿床。     

Possibility of the discovery of eolian gold placers in Tuva

Issue of the influence of eolian processes on the formation of gold placers in the Tuva region is considered. It has been revealed that the formation of placers is related not only to hydrodynamic processes but also to eolian processes, which are reflected in the formation of relief, redistribution of metal, and reworking of the useful component. Study of typomorphic features of the eolian gold and regularities of its redistribution revealed the possibility of discovery of a new type of placer gold (eolian and heterogeneous placers).     

Native gold in Cu- and Ni-bearing pyroxenite-cortlandite intrusions and placers of the Dambuki ore cluster,the Amur region

The Dambuki ore cluster of the Upper Amur region is characterized by numerous and high-grade gold placers. A few small primary deposits and occurrences of gold-quartz type were formerly considered to be the main source of placers. However, the study of widespread Early Cretaceous Cu- and Ni-bearing ultramafic intrusions has shown that gold occurring in primary Cu-Ni ores and products of their weathering practically does not differ from placer gold in morphology, fineness, or geochemical features. In both cases, elements typical of Cu-Ni ore (Cu, Fe, Pd, Ni, etc.) are detected as impurities of gold particles. These data indicate that the Au-and Pt-bearing Cu-Ni ore mineralization may be the main source of placer gold. This ore mineralization is genetically related to small pyroxenite-cortlandite sills and dikes, abundant in the Dambuki ore cluster. The primary gold-quartz deposits and occurrences also contributed to the placers, but their part was rather small.     

Styles of lode gold mineralization contributing to the placers of the Indian River and Black Hills Creek,Yukon Territory,Canada as deduced from microchemical characterization of placer gold grains

Between 1978 and 2009, approximately 430,000 oz of placer gold were obtained from the Indian River and Black Hills Creek, which equates to roughly 20% of the production for the entire Yukon Territory during that period. The area is unglaciated, exposure is poor, and there are few known lode gold occurrences present. The technique of microchemical characterization of placer gold grains has been applied to illuminate the style(s) of source mineralization and their relationship to placer gold from the Klondike gold district immediately to the north. A total of 2,613 placer gold grains from 22 localities were characterised in terms of the Au, Ag, Cu, and Hg content of their alloy and associated suite of opaque mineral inclusions. A combination of alloy and inclusion mineralogy was used to define gold signatures which augmented the previous classification of orogenic gold in the Klondike. Gold type 3b (8–25% Ag) is the main component of the placers in lower Dominion Creek but is augmented and eventually replaced by type 3a gold (10–40% Ag) in placers in the main Indian River valley, probably through erosion of gold-bearing veins in the valley floor. Type 4 gold exhibits highly variable Ag which may contain Hg to a maximum of 11 wt.%. This gold type also hosts a distinctive inclusion assemblage of complex polymetallic sulphides, tellurides, sulfotellurides, and sulfosalts and has previously been ascribed to local low sulfidation epithermal mineralization. Placer gold in drainages radiating from Eureka Dome exhibits various proportions of types 3 and 4 gold depending on location, but type 3 gold forms the major component in Black Hills Creek and northerly flowing tributaries of the Indian River with the exception of Eureka and Montana creeks. Type 5 gold is found only in placers in the middle and lower Indian River. It is distinguished by slightly elevated (0.05–0.17%) Cu in the gold alloy, together with low (5–9%) Ag contents. Inclusions of Bi minerals, Cr-bearing magnetite and molybdenite within type 5 gold suggest derivation from an intrusion-related source. Candidates for such a source include undiscovered lode occurrences associated with Cretaceous age intrusions to the south of the Indian River, or deformed Cu-Au (−Mo) porphyry occurrences which are known to be present in the same area. This analysis of placer gold has indicated that the contribution of low sulfidation epithermal gold from Eureka Creek to the larger placers of the Indian River is minor. Consequently, the placer gold inventory of the Indian River is primarily orogenic in origin. Similarly, the characterization of placer gold in Blackhills Creek strongly suggests an orogenic source. This study has demonstrated for the first time that orogenic lode gold mineralization extends a considerable distance to the south of the southern Klondike goldfield. This information contributes to the regional models of gold mineralization in an area which is currently the focus of intensive exploration.     

Gold resource potential of the eastern Siberian Platform: Placers and their feeding sources

The data on typomorphism of placer gold and its localization in the eastern Siberian Platform have been integrated for the first time. The alluvial, pseudolode, and eolian morphology of gold determines the origin of placers, which is explained not only by hydrodynamic but also by eolian processes. The recent and older alluvial (Au-bearing reservoir rocks in the second case), as well as eolian (unconventional type), genetic types of placers are recognized in the given territory. Precambrian and Mesozoic stages of ore formation are distinguished by the set of typomorphic attributes of placer gold (chemical composition, microinclusions, internal structure, etc.). On the basis of distinguishing features of placer gold, Precambrian lode deposits of great depth spatially related to outcrops of the basement have been forecasted for the first time and classified into low-sulfide gold-quartz, Au-bearing banded iron formation, Au-Cu porphyry, and Au-PGE types. The inferred shallow-seated gold-silver and gold-sulfide-quartz disseminated deposits occur locally and are related to the Mesozoic tectonomagmatic reactivation. The elaborated methods and approaches to the study of placer gold typomorphism in the eastern Siberian Platform also could be helpful in providing insights into placer origin, and forecasting and prospecting gold deposits on the East European Platform, which is close to the Siberian Platform in geological evolution.