Nanoscale metals in Earthgas and mobile forms of metals in overburden in wide-spaced regional exploration for giant deposits in overburden terrains

This paper describes the use of NAnoscale Metals in EarthGas (NAMEG) and MObile forms of MEtals in Overburden (MOMEO) methods in regional scale geochemical exploration for giant deposits in terrains covered by overburden. These methods are based on the premise that gases generated from the earth's interior can not only transport mobile forms of elements from an ore deposit and its geochemical halos to the surface to form a local anomaly, but also transport them from distinct bedrock “geochemical blocks” hosting large and giant ore deposits and give rise to large regional geochemical anomalies and geochemical provinces at the surface.Regional NAMEG and MOMEO surveys for giant gold deposits were carried out in Shandong Province, where the largest gold deposits in China are found, and in the Muruntau region of the Kyzylkum Desert, Uzbekistan, one of the world's largest gold ore provinces.In Shandong Province, where most of the area is covered by complex overburden, large regional anomalies in earthgas and water-extractable Au were delineated over and around the giant gold deposits. For many trace elements, the anomalies are larger in area and have greater contrast than those from other methods. High concentration of water soluble Au extends into the southern area covered by transported overburden, suggesting that this region may have potential for the discovery of new concealed gold deposits. The anomalous provinces of Au in both earthgas and water soluble salts coincide with a deep fault, supporting the idea that the deep fault is the main conduit of Au from the interior.In the central Kyzylkum Desert, nearly all Au-hosting rocks are covered by sedimentary sequences overlain by desert sand. Gold and As anomalies over Muruntau and Kokpatas gold deposits have contrasts ranging from 2 to 400 times background. Strong anomalies were also discovered in the south of the Muruntau region, suggesting a promising area for the discovery of new giant gold deposits.     

云南北衙地区钨矿化特征与找矿方向

云南北衙矿床是中国21世纪初新发现的超大型矽卡岩-斑岩型金多金属矿床之一,除已经勘查评价的Au、Fe、Cu、Pb、Zn等元素外,还伴生有一定量的W元素等有益组分。文章对北衙金多金属矿床万硐山矿段及外围马头湾和南大坪矿区中的钨矿化开展系统的岩石学和矿物学研究,初步查明了万硐山矿段和其外围矿床中的钨矿化特征。研究发现,这些矿区(段)的含钨矿物主要为白钨矿,在万硐山矿段和马头湾矿区还有少量的黑钨矿产出;钨矿化主要产于岩体与围岩地层接触部位的矽卡岩或其退化蚀变岩中,白钨矿多充填在石榴子石等矿物的晶体间隙,个别被石榴子石包裹(南大坪矿区);万硐山矿段和马头湾矿区中的白钨矿具有较高的w(Mo)。这些特征表明,北衙地区的钨矿化作用与典型矽卡岩型白钨矿矿床基本一致。万硐山矿段中白钨矿交代黑钨矿的过程与磁铁矿的结晶过程密切相关,暗示钨矿化与铁、金矿化作用是同一成矿作用的产物。北衙地区的区域土壤W元素地球化学异常具有良好的浓度分级,且部分异常中心与已知的矿床/点明显对应,说明北衙地区具有良好的钨矿找矿潜力,白钨矿和黑钨矿均可以作为找矿标志性矿物,而Mo元素地球化学异常则可以作为间接找矿标志。     

福建南靖南坑钼多金属矿异常特征及找矿远景分析

南靖南坑土壤地球化学圈出5个Mo多金属综合异常,异常呈北东向分布在燕山早期中酸性侵入岩与文宾山组碎屑岩接触带及断裂带附近,异常元素组合以Cu、Mo为主,伴有Pb、Zn、W等,浓集中心明显,局部证实为矿致异常,其中甲3-1异常经详查,Mo多金属矿达中型规模,综合分析该区成矿地质背景、地球化学特征和已发现矿(化)点,认为南坑一带具有良好的钼矿找矿远景。     

长江中下游地区不同尺度铜地球化学异常的意义与大型矿床预测

以长江中下游1∶20万铜区域地球化学数据为基础,研究了铜元素地球化学异常特征,认为不同尺度的地球化学异常图具有不同的研究意义:(1)1∶20万地球化学异常可以圈定矿床异常,用于大型矿床预测。研究区内13个大型矿床中有12个落在具有三层套合结构的地球化学异常中,已知矿床储量与异常面金属量、异常面积之间的相关系数分别为0.94、0.95,显示区域地球化学异常规模与储量之间的较好相关性。(2)1∶50万地球化学异常可以圈定矿区异常,用于在成矿带中预测有利成矿区。(3)1∶100万地球化学异常可以圈定大型矿集区或成矿带,用于矿集区预测。如果把研究区内面积大于1 000km2且含有3个以上已知矿床的异常作为矿集区的话,则长江中下游存在3个大型矿集区:马鞍山—南京矿集区、九江—瑞昌—大冶矿集区和德兴—黄山—安庆—铜陵矿集区(实际上包含德兴和铜陵2个矿集区)。大型矿床多产于多层套合的地球化学异常中,大型矿集区所形成的异常具有至少3层套合结构,浓集中心与大型矿床存在对应关系,这些规律的发现为在不同成矿域预测新的大型矿集区提供了重要地球化学标志。     

Regional geochemical secondary negative anomalies and their significance

Research involving secondary negative anomalies and their application in regional stream sediment surveys has been scarce. Conventionally, negative anomalous threshold values have been calculated in the same way as positive anomalous threshold values. But the conventional methods all have drawbacks which hinder their application. In this paper, we have chosen to delineate negative (and/or positive) anomalies using contrast values in order to overcome the drawbacks.Regional stream sediment surveys at a scale of 1 : 200 000 have been carried out in western Jungger, Shanxi, Kunlun, northwestern Jiangxi, and other areas in China. The geochemical data were processed using System RESMA.On the basis of the distribution of negative and positive single-element anomalies, three possible arrangements may occur: (1) negative anomalies accompanied by positive anomalies; (2) only positive anomalies occurring with no negative anomaly nearby; (3) only negative anomalies, with no positive anomaly nearby. These situations reflect different geological settings and different mineral forming processes. Basically, two different distribution patterns of regional negative anomalies in relation to the backgrounds — low background (LB) and high background (HB) —may be observed in different geological environments: (1) regional negative anomalies are distributed only around the positive anomalies in the LB area; (2) regional negative anomalies can exist on the periphery of positive anomalies in both LB and HB areas.Two kinds of patterns for regional multi-element negative and positive anomalies reflecting different geological processes have been noted: (1) coincident positive anomalies for one group of elements and negative anomalies for another group of associated elements can be used to uniquely define ore deposition; (2) regional positive multi-element anomalies of some elements (including ore and associated elements) occurring over a deposit are accompanied by negative anomalies on the periphery of the deposits. Two regional models of negative and positive anomalies are established for Au and Cu deposits.Integration of multi-element positive and negative composited geochemical anomalies are much more useful than positive anomalies or positive composited anomalies to delineate regional structures.     

Models of Spatial Structures of Regional Multi-element Geochemical Anomalies over Copper-Polymetallic Orefields

Regional stream sediment surveys at a 1:200,000 scale reveal positive and negative regional multi-element geochemical anomalies over medium to large copper-polymetallic orefields of different genetic types in China. Regional geochemical anomalies of orefield refer to those geochemical anomalies that are related to metallogenesis of an orefield in a certain area. The anomaly area is typically 10 to 100 km2. The regional multi-element anomalies related to mineralization can be divided into three groups, that is, the ore-element anomaly association, indicator element anomaly association, and metallogenic environmental element anomaly association. Their common spatial distributions over ore deposits or orefields possess unique structures.The model of spatial structure of regional multi-element geochemical anomalies (RAGSS) of an orefield delineates structural feature possessed by orderly spatial distributions of different groups of multi-element anomaly associations related to orefield metallogenesis. It is     

地球化学测量在乌兰乌珠尔多金属找矿中的作用

乌兰乌珠尔位于柴达木盆地西缘东昆仑西段,柴西缘1∶20万地球化学扫面在该区圈定综合异常一处,通过对该异常作1∶5万水系沉积物测量加密分解,进一步浓缩找矿靶区,对分解后的子异常采用岩石测量控制异常浓集中心层位,然后对异常地段作工程验证,发现了多金属矿床一处。说明地球化学测量在柴西缘地区寻找多金属矿是有效的,可为该区找矿提供参考。     

地球化学负异常及其找矿意义

地球化学负异常的存在具有普遍性。完整的地球化学异常场应包括正异常场和负异常场。负异常按其规模和找矿意义可分为区域、矿床和矿体３个不同层次。区域负异常，可以指明区域找矿方向，圈定找矿靶区；矿床负异常指出矿床可能存在的地段；矿体负异常具体圈定矿体存在的空间位置。负异常与正异常的综合研究，有助于深化对矿床成因的认识，扩大找矿信息，提高找矿效果。     

安徽马头地区斑岩型钼铜矿异常结构研究

利用元素质量平衡计算方法,将元素含量转换成迁移量,直观展现出由元素迁移量构成的原生异常,根据异常的空间分布规律,总结出了由成矿地球化学环境指示元素(Na2O、Ba、Sr)负异常、矿化剂元素(S)正异常、成矿元素(Mo、Cu)及其伴生元素(Ag、As、Sb、W等)正异常构成的马头斑岩型钼铜矿原生异常结构,利用原生异常结构可以对深部成矿前景进行判断和评价;地表岩石(屑)测量结果表明研究区地表同样存在异常结构,且对原生异常结构有很好的继承性,利用地表异常结构可以指明找矿方向、成矿有利地段和矿床产出位置。上述研究成果的取得,不仅丰富和充实了地球化学勘查方法技术,为其他同类型矿床的地球化学勘查提供了参考案例,同时对勘查地球化学应用基础理论而言也是有益的尝试。     

Geochemical exploration for unconformity-type uranium deposits in permafrost terrain, Hornby bay basin, Northwest territories, Canada

The Hornby Bay sandstone basin of the Northwest Territories represents one of three areas in Canada in which the geological environment is favourable for the occurrence of unconformity-type uranium deposits. The project area lies within the zone of continuous permafrost and is associated with relatively thin and locally derived tills and abundant outcrops. Topographic relief is normally in the order of 100 m but may locally exceed 300 m/km in more rugged areas.Geochemical case histories for soil and lake-sediment surveys illustrate: identification of regional anomaly, anomaly follow-up, and detailed investigations. Success in locating uranium occurrences using geochemical surveys is high. Orientation studies trace anomalous dispersion trains 10 to 200 m downslope of recognized sources. Anomaly generation is favoured by active hydromorphic processes in geochemically homogeneous overburden containing an average background of 0.5 ppm uranium (using a 4N nitric acid leach). Anomaly contrasts are typically 2 Xto 3 X this value, and anomalous values exceeding 1.5 ppm uranium are highly reproducible.Copper and radium anomalies act as pathfinders for uranium. Lead is present in anomalous concentrations in specimens from the uranium occurrences but lead enrichment in overburden is not sufficiently great to permit its use as a pathfinder element. Preliminary work based on radon and ²¹⁰Po has not led to identification of anomalies other than those recognized by more routine geochemical surveys.Association of geochemical anomalies with faults within the sandstone basin constitutes one of four conditions elevating an area to drill target status. Methods for drill testing of geochemical soil anomalies depend on the relationship between the geochemical anomaly and an identifiable fault zone.     

陕西秦岭巴山地区化探异常查证找矿实例分析

在陕西秦岭巴山地区9万km²内,通过1:20万区域化探扫面,发现了一批多元素综合异常,并根据地质构造背景分析划分出五个异常带(区)。其中新发现的北秦岭Au、Ag、Pb、Zn异常带,规模大、元素组合复杂且含量高,为一重要的金、多金属成矿带。1986年开始,在该区大力开展区域化探异常查证工作。通过1:5万水系沉积物测量,圈定了以金元素为主的化探异常。在主体异常部位系统地开展了1:1万土壤测量和槽探工程,于当年就在周至县马鞍桥发现了金矿体。随后又根据化探异常特征,布置了钻探和坑探工程验证。经进一步检查和详查,确认马鞍桥金矿为一大型金矿床。     

粤北某铀矿勘查区深部铀矿找矿潜力分析

基于大比例尺区域地质调查工作,在粤北某铀矿勘查区通过分量化探和土壤氡气测量开展深部铀矿找矿工作。已知的隐伏铀矿区测量结果表明,铀矿赋存在断裂之中,在含矿断裂上方形成U的分量化探异常和土壤氡气异常;在该异常区内,同时伴随W、Be、Ba、Mo、Li、Ni的分量化探异常。综合分析分量化探和土壤氡气资料,勘查区内北北东向F_2、F_1处的分量化探和土壤氡气异常具备已知隐伏铀矿区的全部异常特征,推测该处异常具有较大的深部找矿前景,进一步的钻探工作正在进行中。     

河南省栾川县罗村钼矿成矿特征及找矿

通过对河南省栾川县罗村钼矿区域地质背景、矿床地质特征与南泥湖、三道庄及东沟超大型钼矿的综合对比、分析、研究,总结归纳了矿区NWW构造形迹、小岩体与钼矿成矿关系、围岩对成矿的控制作用、围岩蚀变与成矿的关系、地球化学异常与钼矿床的关系等成矿特征.根据罗村钼矿的成矿特征,初步指出今后的找矿方向.     

物化探综合找矿方法在西口沟钼矿勘查中的应用

通过梳理、筛选1∶20万区化异常,结合成矿地质背景,选择具有良好找矿前景的化探异常,利用1∶5万水系沉积物测量进一步缩小了找矿靶区。在此基础上,综合应用1∶1万土壤测量等地球化学方法及激电中梯测量、激电测深等地球物理方法,在物化探异常对应较好及矿化发育地段,择优开展钻探工程验证,最终发现了西口沟钼矿,取得了较好的找矿效果。这说明综合运用物化探方法找矿是可行、有效的,对于区域上寻找同类型矿床具有很好的借鉴意义。     

西藏隆子县那穷锑金矿地质特征及找矿前景分析

那穷锑金矿是近年来通过区域地质矿产调查在西藏自治区隆子县新发现的金多金属矿床,其矿化带受断裂构造控制。目前该矿床研究程度相对较低,若对其成矿地质条件、地质特征及找矿潜力等内容进行专门性和系统性研究,可为该矿床的下步找矿勘探工作提供依据。文章通过总结区域成矿地质背景,分析了该矿床地质特征、地球物理与地球化学异常特征、包裹体地球化学特征,并结合遥感地质特征和异常查证开展相关研究工作,结果表明:矿体主要产于上三叠统涅如组中,受东西向次级断裂构造带控制,目前共发现3条破碎蚀变带;土壤地球化学剖面测量工作中,选择了Sb、Au、As、Bi、Cu作为Sb及多金属成矿指示元素,共圈定单元素异常10处,各元素异常套合较好;激电中梯测量共圈定极化体2条,视极化率异常3处;与成矿有关的流体包裹体类型主要为富液包裹体,并推测矿区流体为含微量CO₂、N₂气体的中低温低盐度NaCl-H₂O热液体系。综合分析认为那穷锑金矿区具备优越的成矿条件,具有寻找金多金属矿的潜力。      

四川杨柳坪Cu-Ni-PGE矿田区域地球化学异常特征

在杨柳坪Cu-Ni-PGE矿田进行的1:20万水系沉积物测量表明,该矿床区域地球化学异常的指示元素有:Pt、Pd、Cr、Ni、Cu、Co、Ag、Cd、Sb、Pb和Zn,异常具有空间分带特征,即:从矿床向外的异常元素依次为Pd、Pt-Cr、Ni-Co、Cu-Cd、Ag-Zn-Pb、Sb.因此在筛选1:20万区域化探异常时,不但要考虑成矿元素的异常强度和规模,而且还要考虑其它指示元素的异常强度和规模.同时也说明1:20万水系沉积物测量可作为铂矿区域普查的有效方法.     

吉林省海沟金矿床的地球化学异常模式

在总结海沟金矿床区域水系沉积物、矿区水系沉积物及矿体的岩石、土壤地球化学异常特征的基础上,建立了海沟金矿床的地球化学异常模式,并依据该模式对区域47个异常进行了研究对比,预测出一处寻找海沟式金矿床的有望异常。     

陕南某微细浸染型金矿床地球化学异常模式

陕南某微细浸染型金矿床是从发现金矿田（床）水系沉积物异常开始，运用地质，地球化学综合方法对异常反复踏勘检查，系统开展大比例尺化探详查找矿程序后找到一处有望成特大型的金矿床。     

Geochemical sampling techniques in the Eastern Desert of Egypt

This paper describes various problems in carrying out geochemical prospecting under the conditions that prevail in the Eastern Desert of Egypt. Conclusions are based on four years experience in geochemical exploration in the Eastern Desert, including studies of over 25,000 geochemical samples. In prospecting for ore deposits in stony and sandy deserts, different kinds of geochemical survey techniques can be successfully applied. In carrying out regional geochemical surveys, stream-sediment sampling in combination with panning of heavy concentrates may be used with a considerable degree of success. The method of the cold extraction of metals produces best results when the alluvial silt and argillaceous fraction (minus 0.075 mm) is sampled. Spectrographic analysis, on the other hand, provides dependable data when the minus 1-plus 0.25-mm fractions are sampled. It is established as a fact that sieving-out of the minus 0.25-mm fraction helps to get rid of aeolian sands which otherwise “dilute” anomalies.In the localities where colluvium is mixed with aeolian sand, sampling of the minus 1-plus 0.25-mm fraction considerably increases the contrast of anomalies (by 3.7 times for Sn, 3.8 for Mo, and 1.5 for Cu) and enlarges their size (4 times for Sn, 2.6 for Mo, and 2.5 for Cu). A possibility of forming of “false” anomalies in colluvium, resulting from the secondary concentration of certain heavy minerals resistant to weathering (e.g. Sn, W, Nb, Ta, Zr, etc.) was proven. This should be taken into consideration while carrying out geochemical prospecting in similar conditions.     

甘肃北山辉铜山铜矿地球化学异常结构研究

以甘肃北山辉铜山铜矿为例,探讨了矽卡岩型铜矿中元素的富集贫化特征以及由富集、贫化元素形成的正、负异常构成的地球化学异常结构.结果表明,在矿床中发生富集的元素,例如成矿元素Cu、矿化伴生元素As、Ag、Mo等、常量组分MgO等在试验区内形成了明显的环带结构,中间为这些元素的正异常,向外经背景带过渡为负异常.这些元素的正异...