The origin and significance of non-aqueous CO2 fluid inclusions in the auriferous veins of Bin Yauri,northwestern Nigeria

Non-aqueous CO₂ and CO₂-rich fluid inclusions are found in the vein quartz hosting mesothermal gold-sulphide mineralization at Bin Yauri, northwestern Nigeria. Although mineralizing fluids responsible for gold mineralization are thought to be CO₂-rich, the occurrence of predominantly pure to nearly pure CO₂ inclusions is nevertheless unusual for a hydrothermal fluid system. Many studies of similar CO₂-rich fluid inclusions, mainly in metamorphic rocks, proposed preferential loss (leakage) of H₂O from H₂O-CO₂ inclusions after entrapment. In this study however, it is proposed that phase separation (fluid immiscibility) of low salinity CO₂-rich hydrothermal fluids during deposition of the gold mineralization led to the loss of the H₂O phase and selective entrapment of the CO₂. The loss of H₂O to the wallrocks resulted in increasing oxidizing effects. There is evidence to suggest that the original CO₂-rich fluid was intrinsically oxidized, or perhaps in equilibrium with oxidizing conditions in the source rocks. The source of the implicated fluid is thought to be subducted metasediments, subjected to dehydration and devolatilization reactions along a transcurrent Anka fault/shear system, which has been described as a Pan-African (450–750 Ma) crustal suture.     

Stochastic modeling of gold mineralization in the Champion lode system of Kolar gold fields (India)

Stochastic modeling of gold mineralization in the Champion lode of Kolar gold fields was carried out using assay data taken from developmental headings. After dividing the lode into 71 horizontal and 18 vertical strata, autoregressive (AR), moving average (MA), and autoregressive and moving average (ARMA) models were developed and applied. The model selection with the acf and pacf for the various strata showed that in most of the cases, ARMA modeling of first-order would forecast gold headings with a reasonable degree of confidence. This was substantiated by comparing the coefficients of variation. From a parsimony point of view, AR (1) model may also be considered valid. The best overall models are: ARMA (1, 1), ; AR (1), , where a_t is N (0, _a ² ), x is in logarithms of in-dwt, and t is in block units of 100 ft. The applications of these models to a specific stratum are given. These models would also be helpful to describe the characteristics of the gold mineralization process of this lode.     

Orebody geometry in lode gold deposits from Zimbabwe: implications for fluid flow,deformation and mineralization

The geometry of some orebodies can be described simply and accurately by three orthogonal axes, U≥V≥W. The ratios between these axes can be expressed as a parameter j=(U/V−1)/(V/W−1), and represented by a graph of U/V plotted against V/W, analogous to the treatment of strain ellipsoids. The orientations of orebodies can be plotted simply on projections using the UVW axes. Measurements of ore bodies from two examples of lode gold deposits from the Zimbabwe craton show that most of these orebodies are oblate. However, orebodies can have significant U/V ratios, implying a component of pipe-like fluid flow during mineralization. Pipe flow is demonstrated to be orders of magnitude more conductive than flow in planar veins and faults. There are significant variations in orebody geometry between deposits and within different sections of a single deposit. W values appear to be influenced by host rock: more permeable rocks have higher W. A negative trend of j value with orebody volume indicates that orebodies do not evolve in a self-similar way, but tend to more oblate shapes with increasing volume.     

马达加斯加北部绿岩带石英脉型金矿流体包裹体特征及成矿作用分析

为探讨马达加斯加北部绿岩带石英脉型金矿的成矿温度和物质来源,对Maevatanana和Andriamena两个绿岩带石英脉型金矿的石英脉流体包裹体的研究表明,这两条绿岩带金矿流体包裹体较为发育,有H₂O-NaCl包裹体,即水溶液型(Ⅰ类);CO₂-H₂O-NaCl包裹体,即L_H2O+V_CO2型(Ⅱ类);富CO₂包裹体,即L_H2O+L _CO2+V_CO2型(Ⅲ类)和少量含子晶的H₂O-NaCl包裹体,即含NaCl子矿物型(Ⅳ类)等4种类型;成矿阶段可分为早期成矿、主成矿、后期成矿阶段,早期成矿阶段以I和部分Ⅱ类包裹体为主,偶见少量Ⅳ类含NaCl子晶包裹体,主成矿阶段以大部分Ⅱ类和Ⅲ类包裹体为主,后期成矿阶段以Ⅰ类包裹体为主;Maev和Adm金矿成矿流体以CO     

新疆包古图地区金矿床矿化类型和与围岩关系研究

西准噶尔包古图地区是新疆北部重要的金铜产地,已发现中型金矿床1处,金矿点20余处,大型斑岩铜（金、钼）矿床1处。金矿床按矿化类型可分为石英脉-蚀变岩型、蚀变岩型、辉锑矿-石英脉型、富硫化物型以及产于斑岩型铜矿中的伴生金。石英脉-蚀变岩型是最主要的矿石类型,构成包古图地区最主要的经济矿体。蚀变岩型是包古图地区近年来发现的新矿化类型,矿体由就位于NW向断裂中的蚀变凝灰质细砂岩和蚀变凝灰岩组成。辉锑矿-石英脉型矿石中含自然砷、自然锑、Paakkonenite、方锑金矿和硫锑金银矿等罕见矿物,这些矿物都与金矿化直接相关。富硫化物型矿石中,自然铋和辉铋矿与金矿化紧密相关。这些金矿化在空间上与中酸性岩体和岩体附近的岩脉关系紧密,成因上金矿化与岩体密切相关,而与岩脉关系不大。成矿元素在岩体中含量最高,其次为岩体附近的火山碎屑沉积岩,同一区域内岩脉的成矿元素含量最低,离岩体越远,成矿元素含量越低。Au与As、Sb、Bi之间具有不同程度的正相关性,As、Sb、Bi异常是该区找金的重要化探标志。中酸性岩体是最重要的找矿标志,岩体附近的断裂系统是金矿最有利的就位空间。     

Geochemical dispersion of gold related to copper-gold mineralization in northeastern Thailand

The nature of gold dispersion in soils and stream sediments associated with a copper-gold-mineralized system in northeastern Thailand has been investigated as a basis for identifying appropriate geochemical exploration techniques for the search for comparable deposits in similar environments.Soils were collected with varying relationships to mineralization as a basis for determining sample representativity, size distribution of gold, variation with soil horizon and possible pathfinder elements. Similarly, stream sediments were collected to estimate sample representativity, size distribution of gold, variation of gold with depth in the stream sediment profile and to compare the relative recoveries of gold in field-panned and laboratory-prepared heavy-mineral concentrates. Samples were analyzed for Au and potential indicator elements by a variety of methods but mostly by instrumental neutron activation analysis.Results indicate the consistent distribution of fine-grained gold in soils which allows Au analysis of relatively small samples from B-horizon soils to be used effectively and reliably to identify the surficial patterns of gold mineralization in the study area. Anomalous patterns of other indicator elements, Co, As, Cu, Sb, W, Pb, Zn, Ag, Fe and Mn, may contribute additional information regarding type of mineralization. This finding indicates the effectiveness of soil surveys in gold exploration, particularly in areas of deep weathering where fresh bedrock exposures are infrequent.Unlike soils, size distributions of gold in stream sediments, as a result of the local flow regime, vary both between sampling sites and at depths within a sampling site. Exploration requires Au analysis of the fine fraction (minus 63 μm) of active stream sediments to reduce the problem of sampling representativity. The presence of coarse-grained gold in the stream channel has drawn attention to the possible benefit of using the conventional field-panning method as a semiquantitative technique for providing immediate results. However, highly erratic distribution of pannable gold on a very local scale together with variable proportions of the total gold recovered in field-panned or heavy-mineral concentrates highlights a potentially serious drawback of the method. Combination of analysis of the minus 63 μm fraction and field panning appears warranted to cover the possible existence of gold of a wide size range in stream sediments.The overall results indicate the utility of geochemical exploration techniques in the search for gold mineralization. However, particular care is necessary in the design and implementation of geochemical techniques to ensure maximum reliability of exploration.     

康滇地轴大田地区铀成矿与重大地质事件

康滇地轴混合岩型铀成矿与混合岩化、构造以及脉岩的关系一直以来存在较大的争议,而大田地区分布的混合岩、长英质脉岩(构造蚀变带内)以及辉绿岩/花岗质脉岩,尤其是富含石墨矿物的石英片岩的年代学特征成为解决这一问题的理想研究对象。在结合研究团队前期年代学研究工作的基础上,本文对大田地区辉绿岩/花岗质脉岩、富石墨石英片岩进行了系统的年代学研究,并获得以下认识:(1)大田地区混合岩化作用发生于840～860 Ma,其原岩形成时代为中元古代;(2)晶质铀矿形成年龄约为775 Ma,与混合岩化作用并无直接的关系,其形成年代与辉绿岩/花岗质脉岩、构造蚀变带内脉岩形成年代较为接近,表明可能为一期产物;(3)锆石中U含量结果分析表明U元素在混合岩化过程中发生了明显的富集现象,表明混合岩是最可能的铀源之一;(4)粗粒晶质铀矿的形成与Rodinia大陆的裂解具有一定的耦合关系,期间断裂活动和脉岩活动提供了成矿热源、流体以及储矿空间。     

纳米物质及对金成矿作用的思考

纳粹物质具有不同于普通物质的奇异性质，纳米物质易于气化运移，可以很好解释诸如矿床元素分带现象和金的成矿多样性等许多传统观念下难以解释的地质现象，从而为成矿理论及找矿方法引发新的思考。     

Re-Os geochronology of gold mineralization in the Fawakhir area,Eastern Desert,Egypt

We report the first Re-Os data on gold-associated arsenopyrite from mesothermal gold-quartz veins in the ancient Egyptian Fawakhir–El Sid gold mining district in the central Eastern Desert. This mining district has an ~5000-year-old history and is displayed in the Turin Papyrus Map (about 1150 BC), which is widely acclaimed as the world’s oldest geographic map, as well as the oldest geologic and mine map. The Fawakhir–El Sid district is part of a regional NNW-trending shear corridor (15 km wide) that hosts several other historic gold mines associated with left-lateral wrench structures and related granite intrusions. Vein-style gold mineralization is hosted within and at the margin of an I-type and magnetite-series monzogranite, the Fawakhir granite intrusion, and a Pan-African (~740 Ma) ophiolite sequence. The ore mineralogy of the mineralized quartz veins includes pyrite-arsenopyrite-pyrrhotite-sphalerite-galena-chalcopyrite-electrum plus a number of tellurides of Ag, Au, and Bi. The ¹⁸⁷Re/¹⁸⁸Os versus ¹⁸⁷Os/¹⁸⁸Os regression on 5 points of arsenopyrite gives an age of 601 ± 17 Ma with an initial ¹⁸⁷Os/¹⁸⁸Os of 0.24 ± 0.07 (2 σ; MSWD = 17). This age coincides within error with the U-Pb age on zircon from the Fawakhir monzogranite (598 ± 3 Ma). The age coincidence and the hydrothermal Te and Bi metal signature suggest a foremost role of granite-related fluids in the quartz-vein system.     

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.     

鲁西铜石地区金矿成矿综合信息预测

鲁西铜石地区是上世纪末期新发现的金矿聚集区。文章在已有找矿模型的基础上,对预测模型的三大类找矿信息进行量化及运算;采用了不同权重求和方案,根据经验分别赋予地质信息、地球物理信息和地球化学信息的权重系数,使这三大类信息图层成为带权重累加的综合信息图层,并分别圈定一、二、三级预测找矿靶区,其中圈定一级靶区4个。对靶区进行的野外检查发现,一级预测区矿化蚀变较强,三级预测区相对较弱,并且在一级预测区发现金矿点一处。     

Dating of detrital zircon grains and fossils from Late Palaeozoic sediments of the Baruo area,Tibet: constraints on the Late Palaeozoic evolution of the Lhasa terrane

ABSTRACT

To determine the Late Palaeozoic evolution of the Lhasa terrane, we report the results of field mapping, petrological and fossil investigations, and U–Pb dating of detrital zircon grains (n = 474) from lower-greenschist-facies clastic rocks of the Lagar Formation in the Baruo area, Tibet. Our results indicate that the Lagar Formation was deposited during the Late Carboniferous to Early Permian in a shallow-marine environment on the northern margin of Gondwana. Glacial marine diamictites are common within the Lagar Formation and record glaciation of Gondwana during the Late Palaeozoic. Moreover, the detrital materials of the Lagar formation originated mostly from the collision orogenic belt. The ages of detrital zircon grains from the Lagar Formation make up five main groups with ages of 410–540 Ma, 550–650 Ma, 800–1100 Ma, 1600–1800 Ma, and 2300–2500 Ma, which display three characteristic age peaks at ~1150, 2390 and 2648 Ma. We tentatively suggest that the Lhasa terrane was a shallow-marine basin under the influence of the Gondwanan glaciation during the Late Carboniferous–Early Permian.     

胶东大尹格庄金矿碳酸盐矿物的特征、物源及其在金成矿过程中的作用

胶东金矿的成因研究一直是矿床学研究的热点, 其中金的物质来源与活化、沉淀机制是最受关注的问题之一。大尹格庄金矿位于胶西北地区的招平断裂带中段, 是区内典型的超大型破碎蚀变岩型金矿, 以存在大量碳酸盐脉而有别于区内其他金矿床, 这些热液成因的碳酸盐脉对该矿区Au成矿具有重要作用, 因而是破解胶东巨量Au物质来源和成矿机制的良好对象。本研究通过细致的岩相学观察, 发现大尹格庄金矿中的碳酸盐矿物主要包括菱铁矿和方解石, 以脉状、浸染状存在于黄铁绢英岩型矿石中, 其中部分菱铁矿与黄铁矿等金属硫化物共生, 其他菱铁矿则与石英共生, 方解石则呈浸染状和脉状两种形式产出, 菱铁矿和方解石均为热液型碳酸盐矿物。扫描电子显微镜研究表明, 在菱铁矿和方解石中均发现有金矿物的存在。Au含量分析结果表明, 菱铁矿和方解石是大尹格庄金矿的重要载金矿物, 形成于成矿作用的主要阶段。碳酸盐矿物原位微区稀土元素数据也显示出热液型碳酸盐矿物的特征; 同位素地球化学数据显示大尹格庄金矿中碳酸盐矿物与胶东地区前寒武纪变质基底中的大理岩明显不同。C-O同位素分析显示, 大尹格庄金矿中菱铁矿的δ¹³C_PDB为-5.12‰~-4.82‰, δ¹⁸O_SMOW为12.13‰~12.80‰, 具有明显的幔源特征; 而方解石δ¹³C_PDB为-0.64‰, δ¹⁸O_SMOW为6.21‰, 显示出幔源流体在上升过程中受到了一定程度的围岩的影响。金矿中菱铁矿显示轻稀土相对亏损, 重稀土相对富集, 有轻微的负Eu异常, (⁸⁷Sr/⁸⁶Sr)_i为0.709842~0.710087, ε_Nd(t)为-18.5~-17.1;方解石的(⁸⁷Sr/⁸⁶Sr)_i为0.710861, ε_Nd(t)为-12.7, 指示形成碳酸盐矿物的CO₂流体可能来自于幔源的基性岩浆。结合胶东以及整个华北克拉通中生代地质演化, 本文认为胶东巨量金可能来自于富集的岩石圈地幔, 成矿物质随这些幔源基性岩浆的活动沿断层等壳内软弱面向上运移, 而CO₂流体在这个过程中起到了促进作用, 并随含金流体最终运移至地壳浅部发生金成矿作用。

     

延边地区五凤-五星山金矿床成矿流体与成矿作用研究

五凤-五星山金矿床是延边地区重要的金矿床类型之一。五凤金矿床、五星山金矿床位于石人火山断陷盆地的南北端,相距近3 km。五凤矿体产在金沟岭组火山岩内,为脉状,五星山矿体产在碱性花岗岩与次粗面安山岩接触带上,为网脉-浸染状。笔者运用显微测温、激光拉曼探针技术,对矿床中各个矿化阶段石英内的流体包裹体进行研究。实验结果表明:1流体包裹体类型主要为气液两相包裹体,纯液相包裹体,少量含CO_2三相的包裹体;2均一温度变化范围在110~440℃之间,与石英脉阶段(Ⅰ)、含硫化物-石英脉阶段(Ⅱ)、方解石石英脉阶段(Ⅲ)以及方解石-沸石阶段(Ⅳ)4个矿化蚀变阶段相对应的流体包裹体的均一温度分别为440~350℃、340~220℃、220~160℃、160~110℃;3盐度w(NaCleq)变化在0.53%~9.47%之间,Ⅰ、Ⅱ、Ⅲ、Ⅳ矿化阶段成矿流体的盐度w(Na Cleq)分别为2.23%~4.63%、9.47%~2.88%、3.85%~1.21%和0.87%左右;4气体成分主要为H_2O、CO_2,少量H_2S、CH_4、N_2。上述结果和硫、碳、氢氧同位素数据,与成矿有关的岩浆作用研究成果,表明该矿床为低硫化型浅成低温热液金矿床,初始成矿流体为大气水,有少量岩浆水参与的中低温、低盐度,还原性流体,成矿物质源于壳幔相互作用的安山质岩浆,成矿机制为流体沸腾作用,可能伴有部分围岩的硫化作用。     

新疆西北缘晚古生代金铜成矿作用与构造演化

晚古生代,新疆西北缘地处古亚洲洋中部,是我国中亚造山带的重要组成部分,伴随着晚古生代强烈的构造岩浆活动,发生了明显的金铜成矿作用,形成了300多个金铜矿床和矿点,已经成为我国重要的金铜矿产开发基地之一.新疆西北缘金铜成矿作用主要有4种类型,即VMS型、韧性剪切带型、火山热液型和斑岩型,所形成的矿床具有成群分布、分段集中的特点,构成了阿尔泰铜多金属成矿带、额尔齐斯金矿带、萨吾尔金铜成矿带、哈图金矿带、包古图金铜成矿带等.新疆西北缘金铜成矿作用与该地区晚古生代洋-陆转化过程中的俯冲、碰撞和后碰撞演化密切相关.早泥盆世,阿尔泰南缘的斋桑洋向北俯冲,形成克兰弧后盆地,伴随双峰式火山活动和热液活动,形成阿舍勒等VMS型块状硫化物矿床;中泥盆世-早石炭世,斋桑洋向南俯冲,在西准地区北缘形成萨吾尔岛弧,并伴随着钙碱性火山活动和阔尔真阔腊等火山热液型金矿床的形成,与此同时,准噶尔洋向北俯冲,在西准地区东南部形成哈图弧后盆地和包古图岛弧,发生拉斑系列火山活动和哈图火山热液型金矿床的形成以及随后的中酸性岩浆侵入和包古图富金斑岩型铜矿床的形成;晚石炭纪-二叠纪发生弧陆碰撞及后碰撞的伸展,形成多拉纳萨依等韧性剪切带型金矿床.金铜成矿作用在新疆西北缘贯穿于整个晚古生代,在晚古生代早期形成的金铜矿床可能遭受了晚期弧陆碰撞和(或)后碰撞的构造岩浆活动的叠加和改造,显示了新疆西北缘金铜成矿作用的多期性和复杂性.     

胶东牟平邓格庄金矿床流体包裹体研究

邓格庄金矿是胶东牟平-乳山金成矿带内第二大石英脉型金矿,金主要产于黄铁矿和多金属硫化物石英脉/细脉中。流体包裹体研究表明,邓格庄金矿不同蚀变带岩石和各成矿阶段金矿石中的流体包裹体主要有三种类型：H2O-CO2包裹体、CO2-H2O±CH4包裹体和H2O溶液包裹体。早期乳白色石英中主要赋存原生的H2O-CO2包裹体和次生的CO2-H2O±CH4包裹体;成矿期黄铁矿石英脉和多金属硫化物石英脉中的CO2-H2O±CH4包裹体主要为原生,随机分布,气液比变化较大,有时出现不同相比例的包裹体共存现象,而H2O溶液包裹体明显沿愈合裂隙分布;在成矿晚期的石英和方解石中主要发育原生H2O溶液包裹体。显微测温结果显示,成矿前（第1阶段）H2O-CO2包裹体的完全均一温度（Th,TOT,至液相）为254℃至365℃,成矿期（第Ⅱ和Ⅲ阶段）CO2-H2O±CH4包裹体的完全均一温度（Th,TOT,至液相）为195～317℃,成矿后（第Ⅳ阶段）H2O溶液包裹体的均一温度（Th,TOT;至液相）为156—219℃。成矿的初始流体富CO2,主成矿期有CH4流体加入,成矿晚期则演化为低温的水溶液流体。水／岩反应及流体不混溶可能是邓格庄金矿金沉淀的主要原因。     

辽宁朝阳长在地区金矿化地质特征与成因分析

辽宁朝阳长在地区金矿 (化 )点为产于辽西中生代断陷盆地边缘元古宇蓟县系雾迷山组白云质灰岩中的微细粒型矿化。区内构造 -岩浆活动强烈 ,金矿 (化 )点受 NNE向断裂及其低序次的断裂、褶皱和层间裂隙控制。矿 (化 )体具有规模小、连续性差的特点 ,Au含量一般 0 .1× 1 0 -6～5.0× 1 0 -6 ,金矿物多以不可见金的形式存在。矿区地质特征、硫同位素组成及流体包裹体研究表明 ,成矿物质来源于地层和脉岩 ,成矿溶液以热卤水 [属 Ca2 - Mg2 (K ) - SO2 -4- (Cl-)型 ,有部分大气水的混入 ]为主 ,呈中偏酸性 ,成矿为中 -低温、高硫低氧的还原环境。     

Magnesite abundance as a guide to gold mineralization associated with ultramafic flows, Timmins area

Altered komatiitic flows of the Tisdale Group locally contain secondary calcite, dolomite or magnesite, where alteration intensity and bulk-rock composition are favourable. Talc is present only in the least carbonatized samples and does not coexist with quartz and magnesite. Magnesite is present only in carbonatized ultramafic komatiitic flows (> 20 wt.% MgO) containing at least 18 wt.% loss on ignition (> 14 wt.% CO₂). Magnesite abundance increases with increasing loss on ignition and ) whole-rock ratio. Altered flows having magnesite to dolomite weight precent ratios exceeding 70 occur in proximity to mineable concentrations of gold and define surface-exploration targets 500 m in diameter.The spatial association of gold with the more magnesian ultramafic komatiitic flows arises in part because of the reactive nature of olivine-rich rocks in the presence of CO₂-bearing aqueous hydrothermal fluids, and possibly because the most magnesian ultramafic flows occur in proximity to an eruptive vent area where the likelihood of rock-fluid interaction is greatest because of the local structural regime.Talc-magnesite—quartz assemblages are present in some ultramafic dykes which cut the older Deloro Group volcanic rocks; the apparent absence of gold in these rocks may be attributed to the higher formation temperature of the talc-bearing, relative to the talc-free, magnesite-quartz assemblages.     

广西大瑶山古里脑和龙头山金矿岩浆期后断裂成矿作用及找矿意义

通过对大瑶山区古里脑和龙头山金矿床地层、岩浆岩含矿性的分析,并进行断裂构造作用多期性的分析和岩浆期后断裂成矿作用的讨论,认为该区深部地层和岩体中的金元素在次火山—斑岩期后断裂构造热液的作用下逐步向上叠加、富集成矿;矿体与岩浆岩体在空间上具有密切的关系;构造-热液作用导致次火山岩、斑岩体或周围地层产生破碎,并使成矿热液沿裂隙充填和再充填而形成金矿体,区内凡构成工业富集的富矿体和含金石英脉或破碎带都与多期次活动的构造-热液作用有关。因此,多期活动的构造-热液作用在大瑶山区具有非常重要的找矿意义。