皖南地区区域地球化学特征及成矿潜力的地球化学预测

根据皖南地区1:20万区域化探资料,计算了区内元素的背景值、区域浓集系数、总体变化系数等参数,阐明了区内元素含量空间分布与成矿元素共生组合特征。使用区域浓集系数及变化系数两个参数,对皖南地区32种元素的成矿潜力进行排序,在目前安徽省地质勘查主攻矿种中,皖南地区的成矿潜力依次为金(银)-钨-钼-铜-铀-锌-铅。同时根据地球化学块体理论和方法,预测了区内金、银资源量,分别为金474t、银16117t,显示出较大的找矿潜力。     

Regional geochemical reconnaissance of the Cordillera Occidental of Ecuador: economic and environmental applications

A regional geochemical reconnaissance survey of the Cordillera Occidental of Ecuador was initiated in 1995 as a sub-component of a wider Mining Development and Environmental Control Technical Assistance Project (PRODEMINCA) in Ecuador. The 36,000 km² survey area encompasses oceanic and continental-margin volcano-sedimentary terranes with known occurrences of porphyry-style Cu-Mo, exhalative massive sulphide, epithermal Au and mesothermal polymetallic mineralisation. A survey sample medium of <177 μm stream sediments was selected following an orientation study in the vicinity of known porphyry Cu mineralisation. In the 2–4°S sector of the Cordillera Occidental for which data are presented, 4850 drainage samples were collected at an average density of 1 per 2.57 km². All were analysed for 36 major and trace elements (Au, Ag, Cu, Pb, Zn, Mo, Ni, Co, Cd, Bi, As, Sb, Fe, Hg, Mn, Te, Ba, Cr, V, Sn, W, La, Al, Mg, Ca, Na, K, Sr, Y, Ga, Li, Nb, Sc, Ta, Ti, Zr). A stringent quality-control procedure included the systematic analysis of certified reference samples, field duplicates and replicates, data for which were used to calculate analytical precision, temporal drift and practical detection limits. Results for this part of the cordillera highlight the contrasting lithogeochemical signatures of the ocean-floor basalt terrane (Pallatanga Unit), the island-arc terrane of the Macuchi Unit, the continental volcanics of the Saraguro Group and the acid and intermediate lavas extruded from the Late Miocene to the Quaternary. Regional geochemical images for Au and associated pathfinder elements are dominated by anomalies relating to known mines and prospects. New exploration targets, often inconspicuous at the regional scale, have however been identified through the normalisation of data for individual lithological units against their respective geochemical backgrounds. In addition to mineral exploration, the drainage geochemical dataset for the Cordillera Occidental provides an unparalleled environmental baseline against which the impacts of future anthropogenic activities (including mining) may be assessed. A basis for the formulation of pragmatic sediment quality criteria and for the identification of natural geochemical hazards is also provided.     

中国区域化探若干基本问题研究：1999—2009

1999—2009年,中国区域化探发生了根本性改变。主导思想是以地球化学理论为指导研究区域化探方法技术问题和进行矿产资源潜力评价。区域化探方法技术研究的基本要求是最大限度保持原生地球化学分布特征,表生地球化学条件下采样物质问题是区域化探方法研究的核心,样品采集应以代表地质找矿信息的基岩物质成分为原则,在全国范围内最大限度地保持采样物质的一致性。基于成矿地球化学理论建立资源潜力地球化学评价方法和实行地质找矿定量预测,使勘查地球化学从单纯方法手段上升到指导地质找矿的理论高度。主要标志是在全国建立完整的区域化探工作方法技术系统和实行样品分析质量全程监控。在区域化探高精度数据基础上绘制与出版精美的地球化学图集,使区域地球化学图精确地反映地质背景分布与异常特征,促进区域化探数据信息深度开发和利用,建立具有从区域、普查到详查进行全过程独立开展资源调查、评价和预测的方法技术体系和工作程序。区域化探长期支撑中国地质找矿工作,是整个地质找矿工作的先导。随着新一代地区和全国地球化学图的形成,将在基础地质和成矿规律研究以及揭示重大地质事件等方面提供新的发现、新的认识和新的观点,对于未来中国勘查地球化学和整个地质工作产生重要影响。     

新疆诺尔特地区化探特征及成矿潜力分析

新疆阿尔泰诺尔特地区经历了前泥盆纪基底陆壳演化期、上叠盆地发育期、上叠盆地的关闭期和造山后期4个阶段;在地质演化过程中伴随着一系列成矿作用。区域化探资料显示,区内下石炭统中—酸性火山岩出露区以Au、Pb、Zn、Cu为特色的化探综合异常带规模大,强度高,化探异常浓集中心明显,在部分异常区内已经先后发现多处金、铜、多金属矿床、矿点和矿化点。区域构造演化富集了成矿元素,特别是下石炭统红山嘴组火山岩为金、铜、铅、锌矿源层,燕山期岩浆活动对矿源层中的成矿元素进一步富集,并在构造有利部位成矿。本文通过研究区区域成矿条件和区域化探异常特征分析,指出诺尔特地区具有较大的找矿潜力。     

新疆东昆仑维宝地区铅锌矿床找矿标志及找矿方向

在新疆东昆仑祁漫塔格地区新发现大量的以Fe,Cu,Pb,Zn,W,Sn为主的多金属矿床(点),铅锌矿床便是其中之一。文章通过对维宝矿区区域成矿地质条件、区域化探异常特征,以及铅锌矿赋矿地层、产出特点、矿化特征、围岩蚀变及成矿物质来源的初步分析,认为维宝地区具备寻找大型铅锌矿床的地质、地球化学条件,Pb-Zn成矿地质条件优越,具有很好的找矿前景;归纳出铅锌矿床的找矿标志,建立了铅锌矿床的经验找矿模型;指出了区内铅锌矿床的找矿方向和找矿靶区,并针对不同类型的矿床提出了下一步的工作建议。     

Introducing a new approach of geochemical anomaly intensity index (GAII) for increasing the probability of exploration of shear zone gold mineralization

Increasing the prediction rate in the identification of mineralization zones using the stream sediment geochemical data is an essential issue in the regional exploration stage. The various univariate (such as fractal and probability plot (PP) methods) and multivariate methods (such as principal component analysis (PCA)) have been performed for interpreting the geochemical data and detecting the mineralization areas. In this study, a new geochemical criterion named geochemical anomaly intensity index (GAII) was proposed for geochemical anomaly mapping. This approach was developed based on the PCA method and the catchment basin coefficient (CBC). The GAII as a weighted geochemical index is calculated using the mineralization principal component (MPC) scores and CBC. GAII can be mapped and utilized for geochemical anomaly mapping and detecting the mineralization areas. Besides, GAII can identify paragenesis elements better than the current methods. In this research, GAII was successfully used to generate geochemical anomaly maps on shear zone gold mineralization in the southwest of Saqqez, NW Iran. The geochemical data have been divided into three groups based on catchment basins and the host rock type. Then the MPCs and paragenesis elements of Au mineralization have been obtained individually using PCA. Three mineralization paragenesis groups consisting of (Au, Sn), (Au, W), and (Au, As, Sb and Ba) have been recognized for different catchment basins of the southwest of Saqqez district using PCA. GAII was calculated and mapped based on the CBC_{(Au, Sn)}, CBC_{(Au, W)}, CBC_{(Au, As, Sb, Ba)}, and their MPC scores. GAII accurately detected the Au mineralization zones and improved the geochemical anomaly map in this area compared to the PP method, concentration-area fractal model, and U-spatial statistics method. The results demonstrated that GAII was successfully used for (a) identifying the mineralization paragenesis elements, (b) intensifying the geochemical anomaly, and (c) increasing the prediction rate of mineralization zones. The shear zone gold mineralization areas in the southwest of Saqqez district were effectively detected using this new data analysis approach. GAII has provided better results than the current PP method, concentration-area fractal model, and U-spatial statistics method.     

Recognition of geochemical footprints of mineral systems in the regolith at regional to continental scales

Understanding the character of Australia's extensive regolith cover is crucial to the continuing success of mineral exploration. We hypothesise that the regolith contains geochemical fingerprints of processes related to the development and preservation of mineral systems at a range of scales. We test this hypothesis by analysing the composition of surface sediments within greenfield regional-scale (southern Thomson Orogen) and continental-scale (Australia) study areas. In the southern Thomson Orogen area, the first principal component (PC1) derived in our study [Ca, Sr, Cu, Mg, Au and Mo at one end; rare earth elements (REEs) and Th at the other] is very similar to the empirical vector used by a local company (enrichment in Sr, Ca and Au concomitant with depletion in REEs) to successfully site exploration drill holes for Cu–Au mineralisation. Mapping of the spatial distribution of PC1 in the region reveals several areas of elevated values and possible mineralisation potential. One of the strongest targets in the PC1 map is located between Brewarrina and Bourke in northern New South Wales. Here, exploration drilling has intersected porphyry Cu–Au mineralisation with up to 1 wt% Cu, 0.1 g/t Au, and 717 ppm Zn. The analysis of a comparable geochemical dataset at the continental scale yields a compositionally similar PC1 (Ca, Sr, Mg, Cu, Au and Mo at one end; REEs and Th at the other) to that of the regional study. Mapping PC1 at the continental scale shows patterns that (1) are spatially compatible with the regional study and (2) reveal several geological regions of elevated values, possibly suggesting an enhanced potential for porphyry Cu–Au mineralisation. These include well-endowed mineral provinces such as the Curnamona and Capricorn regions, but also some greenfield regions such as the Albany-Fraser/western Eucla, western Murray and Eromanga geological regions. We conclude that the geochemical composition of Australia's regolith may hold critical information pertaining to mineralisation within/beneath it.     

Erosion level of the epithermal Rogovik deposit estimated from geochemical data,northeast Russia

The geochemical zoning of the Rogovik epithermal deposit in northeast Russia has been established on the basis of endogenic anomalous geochemical fields (AGCF) of Au–Ag zones, their qualitative and quantitative compositions, and spatial distribution of chemical element indicators of Au–Ag mineralization. The obtained geochemical data (monoelemental AGCF, associations of elements, their composition, contrast, and correlation) allowed us to estimate the erosion level of Au–Ag ore zones. It has been shown that AGCF related to Au–Ag mineralization are distinguished by simple component composition (Au, Ag, Hg, Sb, As, Cu, Pb, Zn) and regular spatial distribution of the elements. It has been established that the least eroded central part of the object is characterized by widespread and the most contrasting Au, Ag, Hg, Sb, and As AGCF closely related to the ore-bearing units of the deposit. The contrast of these fields gradually decreases with depth. Low-contrast Cu, Pb, and Zn AGCF typical of the footwall depth intervals and flanks of Au–Ag zones intervals appear at depth. The northern part of the area is eroded to the deepest level. The contrast of Ag, Hg, Sb, and As geochemical fields abruptly decreases here, and Cu, Pb, and Zn AGCF become widespread with depth. The relatively contrasting fields of anomalous Au concentrations develop here extremely locally and near the surface. It has been concluded that the as yet poorly explored southern part of the Rogovik deposit most likely is promising for further geological exploration and the discovery of new mineralized areas.     

湘东南炎陵横岗铅锌矿床地质特征及其找矿标志

横岗铅锌矿位于南岭东西向构造-岩浆成矿带东北缘。通过物化探剖面测量、地质填图、槽探、老隆调查等地质勘查工作,基本查清了炎陵横岗铅锌矿成矿地质特征,总结了矿床成因,认为其应属典型的中温热液裂隙充填型脉状铅锌矿床。在此基础上,预测该矿床具有中型规模找矿远景,并提出了下一步工作的重点区。     

西藏玉龙斑岩铜钼矿床区域地球化学异常特征和找矿标志

研究了西藏玉龙斑岩铜矿矿床的区域地球化学特征,结合地质条件综合分析了区域地球化学异常分布规律与矿床的关系,提出了地质、地球化学找矿标志。这对玉龙成矿带进一步勘查找矿有一定的意义。     

运用扫描电镜和压汞法研究江汉盆地古新统—白垩系砂岩储层孔喉结构及定量参数特征

通过储集层的孔喉结构来评价储层已广泛运用于油气开发,但目前尚未运用于钾盐储层的评价。本文利用扫描电镜和压汞法获得的大量储层孔隙、孔喉实验数据,研究了江汉盆地古新统—白垩系富钾卤水砂岩储层的孔喉类型和结构、毛细管压力曲线,以及孔喉定量特征参数。研究表明,古新统沙市组砂岩储层以Ⅱ类孔隙结构为主,排驱压力平均值为2.72 MPa,孔隙度平均值为6.32%。而白垩系红花套组砂岩储层以Ⅰ、Ⅱ类孔隙结构为主,Ⅰ类排驱压力平均值为0.28 MPa,孔隙度平均值为16.99%,渗透率为87.79×10~(-3)μm~2;Ⅱ类排驱压力平均值为1.103 MPa,孔隙度平均值为10.02%,渗透率为18.83×10~(-3)μm~2。通过综合分析孔喉定量特征参数(如最大汞饱和度、最大孔喉半径、中值半径、退汞效率等)来评价储层质量,认为古新统沙市组砂岩类型以粉砂岩为主,储层质量较差,属于特低孔低渗储层;白垩系红花套组砂岩类型以细砂岩为主,储层质量较好,属于低孔低渗储层。本研究为该区富钾卤水储层评价以及进一步勘探开发提供了可靠的地质依据。     

Comparison of U-spatial statistics and C–A fractal models for delineating anomaly patterns of porphyry-type Cu geochemical signatures in the Varzaghan district,NW Iran

The delineation of populations of stream sediment geochemical data is a crucial task in regional exploration surveys. In this contribution, uni-element stream sediment geochemical data of Cu, Au, Mo, and Bi have been subjected to two reliable anomaly-background separation methods, namely, the concentration-area (C–A) fractal and the U-spatial statistics methods to separate geochemical anomalies related to porphyry-type Cu mineralization in northwest Iran. The quantitative comparison of the delineated geochemical populations using the modified success-rate curves revealed the superiority of the U-spatial statistics method over the fractal model. Moreover, geochemical maps of investigated elements revealed strongly positive correlations between strong anomalies and Oligocene–Miocene intrusions in the study area. Therefore, follow-up exploration programs should focus on these areas.     

Biogeochemical exploration for gold at a site in the Cordillera Cantabrica,Spain

Dried leaves of Festuca ovina L. (Gramineae) and Chamaespartium tridentatum (L.) P. Gibbs. sub. sp. cantabricum (Spach.) Riv.-Mart., Izco & Costa (Leguminosae) were systematically collected over areas of gold mineralization in the southern part of the Cordillera Cantabrica and analyzed for gold, arsenic and antimony by neutron activation analysis during biogeochemical exploration for gold. Although both plants indicated similar areas of gold mineralization, anomalies with F. ovina were more pronounced than those with C. tridentatum. Plant gold concentrations were shown to correlate with soil gold concentrations for the one transect examined. Cumulative frequency data were used to estimate the geochemically anomalous areas. It was concluded that biogeochemical exploration for gold was feasible within this geochemical province.     

Microchemical Characterization of Natural Gold and Copper Alloys from the Ancient Um Shashoba Gold Mine,South Egypt

The SEM-EDX technique was applied to investigate Au, and Cu＋Sn alloyed grains in the mineralization of the Um Shashoba mine for achieving further understanding of occurrences, internal structures and microchemistry of Au and Cu alloys and associated minerals, and mineralization type. This study is aiming at the genetic history of ore-bearing fluid events, geochemical evaluation and exploration significance. The results showed that the mineralization could be considered as a single major episode generated by metamorphic mesothermal solution rich in sulfides and unsaturated respect to Au. It was differentiated into many stages; started with formation of auriferous pyrite that was pseudomorphed by secondary hematite, limonite and goethite. Three phases of Au alloy were precipitated, and Cu＋Sn and Ag-rich alloys were produced respectively and followed by deposition of two generations of barren pyrite. Calcite and ankerite were crystalized, surrounded and partially replaced some of early formed minerals. Finally, barren muscovite recrystallized around and inside both later formed carbonate minerals that were free of any sign of Au in their structures. The processes of deformation, recrystallization, annealing, dissolution, remobilization and re-precipitation played the most important roles in the genetic history of the mineralization.     

加拿大拉布拉多铀矿化类型和铀矿勘探潜力

拉布拉多(Labrador)地处加拿大地盾东部边缘,其U矿化类型多样,但最重要的是赋存于变质火山岩和沉积岩内的矿化,主要分布于Makkovik省中心矿带区(CMB)的古元古代表壳岩和侵入岩中。该区矿化有岩浆型(伟晶岩和酸性火山岩)、后生--热液型(有些类似于Fe氧化物--Cu--Au(IOCG)型矿床)、剪切带型(可能是变质--交代成因)和砂质沉积岩中的层状矿化,但未发现典型的不整合型。根据其矿化类型,结合已发现矿床的成矿地质特征和矿化地质资料分析,得出该区的一些成矿远景区有较大的勘探潜力,圈定White Bear湖U矿勘查战略选区和Nash湖U矿勘查战略选区。     

黑龙江黑河五道沟地区区域地球化学特征及其与成矿的关系

五道沟地区处于兴安地块与松嫩地块结合部位,多宝山矿集区东部,成矿地质条件优越.该区为森林覆盖区,在该区开展矿产调查过程中,化探方法显得尤为重要.分层次开展区域地质调查、区域地球化学测量和重点区土壤测量,研究该区地球化学特征,确定主攻矿种,圈定重点找矿靶区,取得了一定的找矿成果.通过异常查证新发现铜矿点2处,金矿化点2处,金（铜）矿化信息地10处,找矿线索3处.圈定Ⅰ级找矿靶区3处,Ⅱ级找矿靶区2处.通过研究元素分布规律等,结合成矿地质背景分析,认为该区Au、Ag、Cu、Pb等元素局部富集,Au、Cu成矿的可能性较大,中生代岩浆作用与成矿关系密切.     

黑龙江省新林-塔源地区地球化学特征及成矿远景预测

通过对黑龙江省新林-塔源地区1∶5万水系沉积物测量数据的统计分析,结合多学科知识,对研究区Au、Ag、As、Sb、Bi、Cu、Pb、Zn、Mo、W、Cr、Ni、Hg 13种元素的平均值、标准离差、变异系数、相关性和元素空间分布情况等各项地球化学参数特征进行因子分析及聚类分析,总结出各元素的地球化学分布特征及地质意义。通过对研究区典型矿床的综合研究,总结出区域成矿地质和地球化学条件,结合单元素异常和组合异常的解释评价,最终认为矿集区北部有找到表生铅锌多金属矿的可能,而南部是寻找隐伏铅锌多金属矿的有利地段。     

地球化学调查数据在地质背景、成矿条件分析中的应用:以中国西北干旱荒漠区为例

1:5万矿产地质调查中通常会优先部署地球化学调查工作,采样密度一般大于8点/km2,并分析多达38项地球化学指标,其主要目的是发现"矿致异常",指导矿产勘查工作.而研究表明,区域地球化学数据是地表物质化学组成的直接反映,所以不仅包含了与成矿有关的异常信息,更包含了丰富的地质信息.在本次工作中应用中国西北干旱荒漠景观区1:5万地球化学调查数据成功识别了工作区地质体单元的分布.相比1:20万地质底图,通过clr-PCA分析提取出的1:5万地球化学数据信息展现了更多的细节:（1）地质体单元可以更为细致地划分为多个次级单元;（2）侵入体单元可以进行期次或岩相划分;（3）可为地质体单元的归属提供依据.本项研究结果成功指导了后续开展的1:5万地质调查工作,并对最终的1:5万地质图进行了验证,此外还提供了多处有利找矿线索.      

Identification and mapping of geochemical patterns and their significance for regional metallogeny in the southern Sanjiang,China

The southern Sanjiang region, southwestern China, comprises various continental blocks, tectonic sutures and arcs. This complex structural area is a proper place for the recognition of geochemical patterns and understanding of regional metallogenesis. Considering each individual tectonic unit (i.e., western South China block, Ailaoshan suture, Simao block, Changning–Menglian suture, Baoshan block and Tengchong block) as a statistical unit, this study identifies the distribution patterns of geochemical elements, distinguishes elemental associations for different geological backgrounds (controlled by the regional lithology) and diverse mineralizations, and thereby delineates the mineralized anomalies. To achieve the goals, the kriging interpolation, staged factor analysis and local singularity technology were utilized after the centered logratio (clr) transformation of stream sediment geochemical data. The spatial distributions of metallogenic elements (Au, Ag, Cu, Pb, Zn and Sn) show that not all the areas with high concentrations of elements contain ore deposits. It means that the formation of ore deposits is an independent anomalous geological event, not necessarily related to the original regional abundance of geochemical elements. The different element associations obtained by staged factor analysis of 28 elements are able to reveal the geological backgrounds and metallogenic signatures for different tectonic units. For example, the element associations for the first, second and third factors (Fs) in the western South China block are groups of Ti–Co–V, Sb–Ag–As and Th–U–Be (see text for the detailed element associations), which represent the Emeishan flood basalts, Ag–Pb mineralization and felsic rocks, respectively. Similarly, the element associations Co–V–Cu, Be–U–Th and Sb–Ag–Au for F1, F2 and F3 in the Ailaoshan suture respectively represent the ophiolite complex and mafic rocks, felsic rocks and Au mineralization. The associations from F1 to F4 in the Simao block are Th–U–Sn, V–Co–Cr, Cd–Ag–Pb and Au–Sb, which represent the Linchang batholith, mafic rocks, Ag–Pb–Zn mineralization and Au mineralization, respectively. The distribution patterns of their factor scores can roughly distinguish the anomalies caused by regional backgrounds and mineralizations. The local singularity of factor scores for mineralization can further identify mineralized areas in most of the tectonic units. Nevertheless, an exception occurs in the western South China block where the background element association, Ti–Co–V–Cu–Ni–Cr–P–Mn–Nb–Zn (F1), obscures the Au signature. Therefore, we substituted the single element Au for mineralized element association (F1) to perform singularity mapping, and obtained better result. It was concluded that the combination of staged factor analysis, local singularity and tectonic setting is effective in regional metallogenic potential analysis.     

东秦岭及邻区岩石圈金的丰度特征及与成矿的关系

区域成矿作用的地球化学研究必须以岩石圈物质分异的观点来认识地壳地元素迁移和演化，必须以大区域地壳体系的地球化学特征来指导局部地区的基础地质认训和找矿问题，这是由于地壳与地幔体系的物质运动是不平衡的，明显具分异特征，为些不同构造单元岩石圈的化学成分是不均一的，这就决定了不同构造单元的成岩，成矿作用具有不同的地球化学特征，本文从东秦岭及领区岩石圈金的丰度特征研究入手，探讨该区不同构造环境中金（银）成太