Spatial data analysis of mineral deposit point patterns: Applications to exploration targeting

Systematic spatial analysis of mineral deposit point patterns can reveal significant spatial properties of mineral systems, with major implications for regional mineral prospectivity modelling. For valid results, a study area needs to be clearly defined, taking into account permissiveness of the geological units for a particular mineral system and effects of cover. Standard statistical tests assuming an isometric contiguous study area with regionally homogeneous distribution of deposits are likely to produce invalid results. Analysis of regional uniformity of spatial deposit density is required for adequate design and interpretation of tests for clustering. Spatial distribution of orogenic gold deposits in the Hodgkinson Province in Queensland and the Western Lachlan Orogen in Victoria (Australia) indicates the presence of significant regional linear metallogenic zones, probably controlled by deep crustal domain boundaries oblique and not related to any recognised major faults. Within the metallogenic zones in both regions, individual gold occurrences are strongly clustered into ore fields, but the distribution of ore fields is random.     

蛇绿岩型金刚石和铬铁矿深部成因

地球上的原生金刚石主要有3种产出类型,分别来自大陆克拉通下的深部地幔金伯利岩型金刚石、板块边界深俯冲变质岩中超高压变质型金刚石,和陨石坑中的陨石撞击型金刚石。在全球5个造山带的10处蛇绿岩的地幔橄榄岩或铬铁矿中均发现金刚石和其他超高压矿物的基础上,我们提出地球上一种新的天然金刚石产出类型,命名为蛇绿岩型金刚石。认为蛇绿岩型金刚石普遍存在于大洋岩石圈的地幔橄榄岩中,并提出蛇绿岩型金刚石和铬铁矿的深部成因模式。认为早期俯冲的地壳物质到达地幔过渡带(410~660 km深度)后被肢解,加入到周围的强还原流体和熔体中,当熔融物质向上运移到地幔过渡带顶部,铬铁矿和周围的地幔岩石以及流体中的金刚石等深部矿物一并结晶,之后,携带金刚石的铬铁矿和地幔岩石被上涌的地幔柱带至浅部,经历了洋盆的拉张和俯冲阶段,最终在板块边缘就位。     

中南地区金矿分布规律浅议

本文就我国中南4省区金矿分布的一般规律及金成矿地质条件进行了初步探讨,提出中南地区金矿分布5大规律:空间上集中分布具一定的统一性;赋矿层位多为古老的变质岩系;在空间分布和成因上与岩浆岩密切相关;金成矿在赋矿围岩上虽无较大的选择性,但仍偏重基性火山岩和侵入岩以及有机质、炭质高的沉积岩和变质岩;金的成矿期主要是从前寒武纪到中生代。文章并以部分典型矿床为例,论述了中南4省区金矿控矿因素除矿源层(体)、岩浆岩、构造这3个要素外,还应将深部液态矿源层及区域变质作用视为同等重要的控制因素。     

Crustal-scale shear zones and their significance to Archaean gold mineralization in Western Australia

Many large Archaean epigenetic gold deposits show a broad spatial relationship to regional lineaments in greenstone belts, although in detail they are sited in subsidiary brittle-ductile fault structures. Fluids, originating from a deep source, follow a complex path and re-equilibrate with different lithologies and with metamorphic fluid during migration to higher crustal levels. Temperature and pressure conditions at or below the amphibolite/greenschist metamorphic boundary, where most gold deposits are located, favour the establishment of brittle-ductile and brittle subsidiary structures, the preferred structural setting of gold deposits. Physical gradients between the regional ductile structures and more brittle subsidiary structures ensure transient, strongly localized, fluid flow into the latter, where lower temperatures and suitable host rocks with high Fe/(Fe + Mg) ratios favour gold-deposition. The multi-source origin and continuous re-equilibration of the fluid with crustal rock, which includes granitoid and greenstone-belt lithologies of different ages, is reflected in the diverse isotopic and geochemical signature of the gold deposits.     

The geological setting of lode-gold deposits in the central southern Urals: a review

The late-Paleozoic Uralides represent one of the largest lode-gold metallogenic provinces in the world. In the southern Urals, gold distribution is heterogeneous and is confined mainly to two tectonostratigraphic zones, namely the Main Uralian fault and the East Uralian zone. The important lode-gold districts within and in the immediate hangingwall of the first-order crustal suture of the Main Uralian fault are characterized by a complex tectonic history of earlier compressional tectonics involving thrusting, folding and reverse faulting and later transcurrent shearing. Gold mineralization is hosted by second- and third-order brittle to brittle–ductile strike-slip faults that developed late during the kinematic history of the Main Uralian fault. Strike-slip reactivation of earlier compressional structures was related to the late-stage docking of the passive margin of the East European platform with island-arc complexes of the southern Urals, an event that is tentatively related to changes in plate motion during the final stages of terrane accretion during the upper Permian and lower Triassic. Gold mineralization was controlled by the permeability characteristics of the hydrothermal conduits, as well as by competence contrasts and geochemistry of the mainly volcanic host rocks. Mineralization occurred at relatively shallow crustal levels (2–6 km) and largely post dates peak-metamorphism of the host rocks. The large and very large (up to 300 to Au) gold deposits of the East Uralian zone are hosted by upper-Paleozoic granitoid massifs. Gold mineralization is temporally associated with the main phase of regional-scale compressional tectonics and granite plutonism during the upper Carboniferous and lower Permian. Controlling structures have a dominantly east–west strike and occur as hybrid shear-tensional vein systems in competent granitoids subjected to east/west-directed regional shortening. Deformation textures and alteration mineral assemblages indicate lower-amphibolite-facies conditions of mineralization close to peak metamorphic conditions that are associated with the mid-Permian regional metamorphism and tectonism. Gold deposits in the southern Urals are, therefore, polygenetic and are temporally and genetically distinct in each of the two major mineralized tectonostratigraphic zones of this well-preserved collisional orogenic belt. The different timing of ore fluid generation and fluid discharge is interpreted to be the result of the different tectonic, metamorphic and magmatic evolution of terranes in the southern Urals.     

Lithospheric controls on the formation of provinces hosting giant orogenic gold deposits

Ages of giant gold systems (>500 t gold) cluster within well-defined periods of lithospheric growth at continental margins, and it is the orogen-scale processes during these mainly Late Archaean, Palaeoproterozoic and Phanerozoic times that ultimately determine gold endowment of a province in an orogen. A critical factor for giant orogenic gold provinces appears to be thickness of the subcontinental lithospheric mantle (SCLM) beneath a province at the time of gold mineralisation, as giant gold deposits are much more likely to develop in orogens with subducted oceanic or thin continental lithosphere. A proxy for the latter is a short pre-mineralisation crustal history such that thick SCLM was not developed before gold deposition. In constrast, orogens with protracted pre-mineralisation crustal histories are more likely to be characterised by a thick SCLM that is difficult to delaminate, and hence, such provinces will normally be poorly endowed. The nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks, with back-arc basalts, transitional basalts and basanites enriched in gold relative to other rock sequences. Thus, segments of orogens with thin lithosphere may enjoy the conjunction of giant-scale fluid flux through gold-enriched sequences. Although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits, the precise siting of those giants depends on the critical conjunction of a number of province-scale factors. Such features control plumbing systems, traps and seals in tectonically and lithospherically suitable terranes within orogens.     

3D numerical modelling of fluid flow in the Val-d’Or orogenic gold district: major crustal shear zones drain fluids from overpressured vein fields

Fluid flow patterns have been determined using oxygen isotope isopleths in the Val-d’Or orogenic gold district. 3D numerical modelling of fluid flow and oxygen isotope exchange in the vein field shows that the fluid flow patterns can be reproduced if the lower boundary of the model is permeable, which represents middle or lower crustal rocks that are infiltrated by a metamorphic fluid generated at deeper levels. This boundary condition implies that the major crustal faults so conspicuous in vein fields do not act as the only major channel for upward fluid flow. The upper model boundary is impermeable except along the trace of major crustal faults where fluids are allowed to drain out of the vein field. This upper impermeable boundary condition represents a low-permeability layer in the crust that separates the overpressured fluid from the overlying hydrostatic fluid pressure regime. We propose that the role of major crustal faults in overpressured vein fields, independent of tectonic setting, is to drain hydrothermal fluids out of the vein field along a breach across an impermeable layer higher in the crust and above the vein field. This breach is crucial to allow flow out of the vein field and accumulation of metals in the fractures, and this breach has major implications for exploration for mineral resources. We propose that tectonic events that cause episodic metamorphic dehydration create a short-lived pulse of metamorphic fluid to rise along zones of transient permeability. This results in a fluid wave that propagates upward carrying metals to the mineralized area. Earthquakes along crustal shear zones cause dilation near jogs that draw fluids and deposit metals in an interconnected network of subsidiary shear zones. Fluid flow is arrested by an impermeable barrier separating the hydrostatic and lithostatic fluid pressure regimes. Fluids flow through the evolving and interconnected network of shear zones and by advection through the rock matrix. Episodic breaches in the impermeable barrier along the crustal shear zones allow fluid flow out of the vein field.     

湘中前寒武系金矿地质及相关成矿问题探讨

湘中前寒武系金矿床主要分布于白马山-龙山-紫云山E-W向构造-岩浆岩带,包括锑金、锑砷金、砷金等不同矿物组合的矿床.金矿类型主要为破碎带蚀变岩型,次为石英脉型.金矿产于岩体外接触带及其附近和隐伏岩体上方.其成因为变质热液型金矿床和热接触变质热液型金矿床.区域矿床成矿规律性强,找矿标志明显,远景可观.     

超高压变质矿物中的多相固体包裹体研究进展

大陆碰撞过程中熔/流体的组成和演化是研究大陆深俯冲动力学的重要内容,而超高压岩石记录了大陆俯冲和折返过程中的熔/流体-岩石相互作用,因而是研究大陆碰撞过程中熔/流体组成和演化的天然实验室。大陆俯冲带高压/超高压变质矿物中多相固体包裹体作为熔/流体活动的直接记录,为我们提供了揭示超高压变质过程中熔/流体演化的重要制约。近年来,围绕超高压岩石中多相固体包裹体的形成时间、演化过程及其所反映的俯冲带超高压变质熔/流体的组成和性质,进行了大量的研究工作。超高压岩石中多相固体包裹体的发现,为理解峰期超高压变质流体的组成和演化提供了重要制约,同时也为研究俯冲板片-地幔楔界面的熔/流体交代作用提供了新的途径。本文从多相固体包裹体形成机制、结构形态特征、矿物化学成分及其地质地球化学意义等方面,对于超高压变质岩中多相固体包裹体的研究现状和存在的问题进行系统地总结和探讨,以期促进多相固体包裹体的岩石学和地球化学研究。     

A review of the distribution of metamorphism in the ancient Rhodesian craton

During the early development of the Rhodesian craton the regional metamorphism of some of the oldest rocks of Bulawayan and Shamvalan age, was apparently progressive and is expressed in terms of a clearly defined metamorphic zonation established under conditions of relatively high geothermal gradients in which very low grades typical of the central craton pass into extremely high grades that define the cratonic margin particularly within the Zambezi and the Limpopo belts. The distribution of the associated early granitic rocks relates to the metamorphic pattern, thus implying that both metamorphism and granite development were due to thermal highs centred on the Limpopo mobile belt and possibly the Zambezi belt.     

Metallogenic ‘factories’ and resultant highly anomalous mineral endowment on the craton margins of China

The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone, hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities. After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic, with incorporation of iron ores on assembled micro-block margins, the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle. The rifted margins with trans-lithosphere faults provided pathways for Cu-Au (Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas, and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks. There was diachronous formation of hydrothermal orogenic gold, antimony, and bismuth systems in the narrow orogenic belts between the cratons. Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton, leading to anomalous heat flow and formation of orogenic gold deposits, including those of the giant Jiaodong gold province on its north-eastern margin. These gold deposits, many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle, helped propel China to be the premier gold producer globally. The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems. Although craton margins globally control the formation and preservation of a diverse range of mineral deposits, China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history.     

Distribution of orogenic gold deposits in relation to fault zones and gravity gradients: targeting tools applied to the Eastern Goldfields, Yilgarn Craton, Western Australia

A quantitative spatial analysis of mineral deposit distributions in relation to their proximity to a variety of structural elements is used to define parameters that can influence metal endowment, deposit location and the resource potential of a region. Using orogenic gold deposits as an example, geostatistical techniques are applied in a geographic-information-systems-based regional-scale analysis in the high-data-density Yilgarn Craton of Western Australia. Metal endowment (gold production and gold ‘rank’ per square kilometer) is measured in incremental buffer regions created in relation to vector lines, such as faults. The greatest metal tonnages are related to intersections of major faults with regional anticlines and to fault jogs, particularly those of dilatant geometry. Using fault length in parameter search, there is a strong association between crustal-scale shear zones/faults and deposits. Nonetheless, it is the small-scale faults that are marginal or peripheral to the larger-scale features that are more prospective. Gravity gradients (depicted as multiscale edges or gravity ‘worms’) show a clear association to faults that host gold deposits. Long wavelength/long strikelength edges, interpreted as dominantly fault-related, have greater metal endowment and provide a first-order area selection filter for exploration, particularly in areas of poor exposure. Statistical analysis of fault, fold and gravity gradient patterns mainly affirms empirical exploration criteria for orogenic gold deposits, such as associations with crustal-scale faults, anticlinal hinge zones, dilational jogs, elevated fault roughness, strong rheological contrasts and medium metamorphic grade rocks. The presence and concurrence of these parameters determine the metallogenic endowment of a given fault system and segments within the system. By quantifying such parameters, the search area for exploration can be significantly reduced by an order of magnitude, while increasing the chance of discovery.     

小秦岭金矿田太古宙太华群变质岩与金矿关系的探讨

小秦岭金矿田变质岩是由表壳岩经过区域变质、深部重熔、混合岩化作用形成,典型特征是低钾富钠,具有太古宙TTG岩石特点.Au元素在太华群岩层、岩石中分布不均匀、多重母体分布是造成现今太华群金丰度值低的一个重要原因.Au元素在太华群地层和侵入于其中的花岗质岩石遭受变质及混合岩化作用过程中曾经历了非均一化作用并产生早期活化转移,在一些部位贫化,在一些部位富集,富集部位就可能形成矿床.硫、铅同位素的对比研究,证实了成矿物质来源于该套古老变质岩系.     

Numerical modelling of orogenic processes and gold mineralisation in the southeastern part of the Yilgarn Craton,Western Australia

We use numerical modelling codes to simulate aspects of some current hypotheses for the origin of gold deposits and hydrothermal systems in the Yilgarn Craton of Western Australia. In particular, we investigate conceptual models advocating vertically continuous hydrothermal systems as well as those invoking extensive lateral flow and possible links with advection of heat by late orogenic granitic magmatism. Numerical models of part of the Eastern Goldfields Province and Southern Cross Province have been built with FLAC3D, to simulate crustal‐scale coupled interaction between deformation and fluid flow. These illustrate the potential for fluid focusing and mixing in shear zones, including downflow of meteoric water, lateral fluid flow driven by topographic elevation and upwards flow of fluids derived from melting and metamorphism in the deep crust. In some cases, downflow also occurs within the middle crust, at depths where fluid influx might trigger melting if the geothermal gradient were appropriate. The models indicate that tectonic wedging within a layered crust and diverging thrust systems that generate ‘pop‐up’ wedges may be important in facilitating efficient fluid upflow and downflow during uplift, while topographic elevation related to asymmetric thrust migration and loading tends to promote lateral fluid flow. However, the effect of topography appears more important than the precise depth or location of the site of fluid production in the deep crust. The effects of thermal convection and fluid‐fluid interaction have also been numerically modelled for a simplified section across the Kalgoorlie Terrane. Modelling under both hydrostatic and lithostatically overpressured pore‐pressure gradients has effectively delineated domains of convective fluid flow within the middle and upper crust, and has identified two generic sites that are favourable for fluid mixing, notably hangingwall and footwall environments in major shear zones, such as the Bardoc Shear, and in broad antiforms, such as the Goongarrie ‐ Mt Pleasant Antiform. The thermal effect of small plutons embedded in a regional metamorphic regime can cause significant lateral displacement of fluid convection patterns, over distances greater than pluton diameter, as well as more proximal effects on precipitation and dissolution of mineral species. However, these results are highly dependent on the pore‐pressure gradient and the permeability structure of the crust, and require magmatic and metamorphic fluid generation to be precisely timed with respect to deformation, thus reinforcing the dynamic feedback between deformation, magmatism and fluid production and migration.     

大别-苏鲁区超高压(UHP)变质岩的多阶段构造折返过程

追溯和重塑超高压变质岩由100多千米地幔深度折返至上地壳及地表的过程,对理解会聚板块边缘及大陆碰撞带的运动学和动力学是极为重要的.主要依据构造学、岩石学、地球化学和可利用的地质年代学资料,结合区域多期变形分析,大别-苏鲁区超高压变质岩的折返过程至少可分解出4个大的阶段.块状榴辉岩记录了三叠纪(约250~230 Ma)大陆壳岩石的深俯冲/碰撞作用.超高压变质岩早期迅速折返发生于超高压峰期变质作用(P＞3.1~4.0 GPa,T≈800±50 ℃)之后,处于地幔深度和柯石英稳定域,相当于区域D₂变形期阶段.分别与区域变形期D₃、D₄和D₅对应的折返过程,以及后成合晶、冠状体等卸载不平衡结构发育和减压部分熔融作用2个中间性构造热事件,均发生在地壳层次. 网络状剪切带在折返过程的不同阶段和不同层次均有发育,标志着在超高压变质带内的变质和变形分解作用曾重复进行.着重指出,超高压变质岩的折返,主要是由大陆壳的深俯冲/碰撞和伸展作用控制的构造过程,且受到俯冲带内、带外诸多因素的约束,其中水流体就起关键作用.      

A strike‐slip core complex from the Najd fault system,Arabian shield

Metamorphic core complexes are usually thought to be associated with regional crustal extension and crustal thinning, where deep crustal material is exhumed along gently dipping normal shear zones oblique to the regional extension direction. We present a new mechanism whereby metamorphic core complexes can be exhumed along crustal‐scale strike‐slip fault systems that accommodated crustal shortening. The Qazaz metamorphic dome in Saudi Arabia was exhumed along a gently dipping jog in a crustal‐scale vertical strike‐slip fault zone that caused more than 25 km of exhumation of lower crustal rocks by 30 km of lateral motion. Subsequently, the complex was transected by a branch of the strike‐slip fault zone, and the segments were separated by another 30 km of lateral motion. Strike‐slip core complexes like the Qazaz Dome may be common and may have an important local effect on crustal strength.     

胶东中生代金成矿系统

胶东是我国最重要的金矿集区,其内已发现金矿床150余处,探明金资源储量4000余吨。虽然其金矿床数量众多、资源储量巨大、分布地域广泛、产出空间各异、矿化类型多样,但它们的成矿地球动力学背景、赋矿围岩环境与产出条件及其成矿作用特征总体一致:(1)胶东是一个主要由前寒武纪基底岩石和超高压变质岩块组成、中生代构造-岩浆作用发育的内生热液金矿集区,约130~110Ma的金成矿事件比区域变质作用晚约2000Myr;(2)区域金成矿系统形成于早白垩世的陆缘伸展构造背景,大规模金成矿事件发生在区域NW向伸展转换为NE向伸展后的NEE向挤压变形作用过程中,对应于中国东部岩石圈大规模减薄、华北克拉通破坏和大陆裂谷作用的高峰;(3)金矿床群聚于NNE向玲珑、鹊山和昆嵛山变质核杂岩周边,主要沿前寒武纪变质岩与中生代花岗岩体接触带形成的区域NE-NNE向拆离断层带分布;(4)控矿断裂带经历了早期的韧-脆性变形和晚期的脆性变形构造叠加,在三维空间上呈舒缓波状延展,控制了金矿体的侧伏和分段富集;(5)矿化样式以破碎带蚀变(砾)岩型、(硫化物-)石英脉型和复合脉带型为主,矿石普遍发育压碎、晶粒状和填隙结构,浸染状、细脉浸染状、网脉状、脉状、团块状和块状构造,反映其形成于韧-脆性→脆性变形环境;(6)矿石中金属矿物以黄铁矿、黄铜矿、方铅矿和闪锌矿为主,非金属矿物以石英、绢云母、钾长石、斜长石和方解石为主;金矿物以银金矿和自然金为主、含少量金银矿,主要以可见金的形式赋存于黄铁矿和石英裂隙中、含少量晶隙金和包体金;热液蚀变主要为黄铁矿化、硅化、钾长石化、绢云母化和碳酸盐化;成矿元素为Au-Ag(-Cu-Pb-Zn);呈现出中-低温蚀变矿化组合特征;(7)成矿流体为壳-幔混合来源,以壳源变质流体为主;成矿物质总体来源于中生代活化再造的前寒武纪变质基底岩石,并混入了少量浅部地壳和地幔组分。这种区域成矿特征的一致性,表明胶东金矿集区早白垩世大规模金成矿作用受控于统一的地质事件,属于后生的中-低温热液脉金成矿系统。这些金矿床具有明显的时空群聚分布特征,主要沿三个变质核杂岩周边的岩相接触带产出,且自西向东,金成矿作用年龄由老变新。据此,可划分为胶北隆起蚀变岩-石英脉型、苏鲁超高压变质带硫化物-石英脉型和胶莱盆地北缘蚀变砾岩型三个金成矿子系统。其矿化样式由浸染-细脉、细脉-网脉型和石英脉型→硫化物-石英脉型→蚀变(角)砾岩型变化,矿石结构、构造以细脉浸染状构造为主→环带结构与梳状构造→角砾状构造为特色,反映其成矿作用分别发生于脆-韧性转换带(约15km)→脆性张剪性断裂带→脆性角砾岩带(约5km)环境;矿化、蚀变规模和强度逐渐减弱,成矿物质中浅部壳源组分逐渐增多,可能与其矿床定位空间越来越远离源区有关;成矿温度和压力依次降低、成矿流体中大气降水和/或盆地卤水贡献逐渐增大,与其成矿深度越来越浅、成矿构造环境越来越偏张性的变化趋势一致。这种成矿特征的区域规律性变化反映至少在拆离断层韧-脆性转换带附近→脆性角砾岩带之间的地壳剖面中、在不同的垂向深度上连续成矿。胶东中生代金成矿系统的上述特征明显区别于典型的"与侵入岩有关的金矿"和"造山型金矿",也不同于全球其它已知的金矿床类型,不能被已有成矿模式所涵盖。为合理解释胶东中生代金成矿系统独特的地质与成矿特征,我们提出新的"胶东型金矿"成矿模式,指出古太平洋Izanagi俯冲板片的回转作用可能是引起区域前寒武纪变质基底岩石中成矿物质大规模活化再造的主要驱动机制,成矿流体主体来源于俯冲板片变质脱水,金可能主要以Au(HS)2-络合物的形式在流体中沿拆离断层系输运,在韧-脆性转换带附近→脆性角砾岩带,由于构造空间急剧增大、成矿流体的温度和压力突然降低,CO2、H2S逸出和硫化作用导致Au(HS)2-等金络合物失稳分解,金大规模沉淀富集成矿。     

闽中尤溪－德化－永泰地区金矿地质特征、成矿条件及成矿规律

闽中尤溪－德化－永泰地区中元古界基底变质岩在火山岩中呈“天窗”断续出露，火山－侵入岩浆活动强烈，北东、北西向断裂发育，是我省金矿潜在的有找矿远景的地区之一。本文通过对控制成矿的地质因素的分析研究，认为：含基性－中酸性火山沉积建造的中元古界卓地组、葛坑组基底变质岩是金的重要矿源层，是成矿的前提条件；各种构造，尤其是断裂构造，控制了成矿带的展布和矿床（点）的形成，并决定了矿（化）体的定位空间，是成矿的先决条件；多期次的岩浆活动为成矿提供热源、热液源的部分矿源，是成矿的必要条件。成矿时期始于晋宁期，印支期有明显的矿化活动，燕山期为主要的成矿时期。同时，阐述了由控矿因素所制约的若干成矿规律，进而提出该地区金的区域成矿模式，并对金的潜在资源和找矿远景进行了初步预测和评价。     

中国金矿资源特征及勘查方向概述

基于金矿成矿地球动力学环境以及矿床基本地质特征等,将中国金矿床类型归纳为11 类,其中以构造破碎带蚀变岩型、中深成侵入岩体内及其外接触带型、卡林-似卡林型、浅变质碎屑岩中热液型、陆相火山岩型等为主要找矿类型;成矿年代以中生代、新生代为主。在中国Ⅲ级成矿区带划分基础上,总结研究大地构造单元、地质演化、成矿地质条件、空间分布特征、金矿类型、区域成矿要素、资源量等,初步厘定42 个金矿集区,其空间呈集中分布特征。根据金矿勘查单位面积的钻探数量,初步将中国金矿集区划分为高、中、低工作程度区,高程度区主要分布在中东部地区;除砂金矿外,中国88.12%的岩金（伴生金） 矿探矿深度在500 m 以上,说明探矿钻探验证偏少、偏浅。文章还探讨了中国金矿集区资源找矿潜力,提出了勘查找矿方向和建议,指出中东部老矿山深部、外围和西部金矿集区特别是位于新疆、青海、西藏等地区的,是未来找矿潜力重点区域,未查明资源储量巨大。     

黔西南隐伏岩体圈定与金矿物源探讨

黔西南金矿勘查已升级至国家战略层面,弄清其成因机制具有重要意义。综合运用区域重磁资料,对区内深部基底物质进行研究,通过对浅、深部隐伏岩体圈定及地质-重力模型异常拟合计算,结合区域地质、矿产及化探资料,提出金矿成矿物源,主要有两种供给方式,一种为前人的由表层沉积岩提供矿源层,一种为本研究提出的由深部以中生代花岗岩或变质基底(含基性-超基性岩浆岩类参与)提供矿源层。厘定了12处浅部隐伏岩体异常区,分离出4大深部岩浆岩块体。研究成果基本反映了区内的客观地质现象和地质作用结果,为研究区金矿勘探提供相关依据。