Characteristics of Gold Mineralization at the Baguiomo Gold Panning Site, Koudougou Region, Burkina Faso, West Africa

The Birimian Baguiomo formations are located in the northern part of the Boromo greenstone belt. In this belt, the volcanic rocks (tholeiitic basalt, calcalkaline basalt, andesite) hosting the gold mineralization are located in the Kwademen-Baguiomo shear zone. This mineralization, located only a few kilometers from the Kwademen gold deposit, is uncharacterized and, together with the latter, could constitute a gold potential capable of being economically exploitable. It is in this sense that this work is carried out with a view to characterizing the gold mineralization of the Baguiomo gold panning site. To carry out this work, we have made direct field measurements, combined with microstructures, and combined all this with data from geochemical rock analysis of the basalts that are the main host formations. Geochemical data show that tholeitic basalts formed from a mantle plume that was emplaced in an oceanic plateau context. Calc-alkaline basalts and andesites are comparable to Paleoproterozoic tholeitic basalts (PTH3), which are slightly enriched in light rare earths. Fertility tests show that these basalts concentrate between 3 and 6 ppb of gold at the time of accretion, which is sufficient for remobilization of this primary gold during the Eburnian orogeny to yield a deposit of around 4 - 5 Moz. Gold mineralization is associated with pyrite crystals when the latter are disseminated in the rock mass, whereas it is associated with hematite in quartz veins concordant with S1 shear deformation. It is mainly the pyrite crystals in the pressure shadows that contain the gold grains, whose development would be synchronous with micro-shear zone reactivation during the first phase of D1B deformation. The second phase of D2B deformation, which is a crenulation or fracture schistosity, does not significantly affect the shear deformation that controls mineralization.

Lead Isotopic Steep-Dipping Zone and Mineralization—An Example from Mineral Deposits Concentrated Area in East Qinling,China

Lead isotopic geochemical steep-dipping zone usually exists on inhomogeneous boundaries of earth blocks. Its crossing with the geophysical gradient zone often convergently occurs at giant deposits. Deep structures or concealed structural planes obviously have the coupling relationship with the convergent area of mineral deposits. The geochemical steep-dipping zone is usually distributed along the boundary of ancient continental blocks. Its crossing effect with geophysical gradient zone is usually presented as depression or swell of Moho discontinuity on the crossing direction with the ancient continental margin, which would lead to form deep fractures of earth crust at block margins or lead to adjustment of earth crust texture. The deep hydrothermal liquid would rise up along the structural planes to form the convergent areas of mineral deposits. For example, Luonan- Luanchuan area in east Qinling is a typical crossed area of the geochemical steepdipping zone and geophysical gradient zone. The mineral deposit belt extends along EW direction. It was controlled by the geochemical steepdipping zone equidistantly distributed along NE direction like a string of beads controlled by a gravity gradient zone in NE direction and a mantle depression slope. Along a plunging mantle syncline on EW plunging direction, from the east to the west, checkform was distributed which controls synergic crustmantle granoporphyry rocks. Therefore, a convergent mineralization area of Mo, W, Zn and Au giant deposits occurred.

The efficiency and accuracy of probability diagram, spatial statistic and fractal methods in the identification of shear zone gold mineralization: a case study of the Saqqez gold ore district,NW Iran

In this study,geochemical anomaly separation was carried out with methods based on the distribution model,which includes probability diagram(MPD),fractal(concentration-area technique),and U-statistic methods.The main objective is to evaluate the efficiency and accuracy of the methods in separation of anomalies on the shear zone gold mineralization.For this purpose,samples were taken from the secondary lithogeochemical environment(stream sediment samples)on the gold mineralization in Saqqez,NW of Iran.Interpretation of the histograms and diagrams showed that the MPD is capable of identifying two phases of mineralization.The fractal method could separate only one phase of change based on the fractal dimension with high concentration areas of the Au element.The spatial analysis showed two mixed subpopulations after U=0 and another subpopulation with very high U values.The MPD analysis followed spatial analysis,which shows the detail of the variations.Six mineralized zones detected from local geochemical exploration results were used for validating the methods mentioned above.The MPD method was able to identify the anomalous areas higher than 90%,whereas the two other methods identified 60%(maximum)of the anomalous areas.The raw data without any estimation for the concentration was used by the MPD method using aminimum of calculations to determine the threshold values.Therefore,the MPD method is more robust than the other methods.The spatial analysis identified the detail soft hegeological and mineralization events that were affected in the study area.MPD is recommended as the best,and the spatial U-analysis is the next reliable method to be used.The fractal method could show more detail of the events and variations in the area with asymmetrical grid net and a higher density of sampling or at the detailed exploration stage.

GEOLOGICAL CHARACTERISTICS OF MAIN TYPES OF GOLD DEPOSITS IN SHEAR ZONES AND SIMULATING EXPERIMENTS ON TECTONO-CONTROLLED GOLD MINERALIZATION

Gold deposits in shear zones in China can be divided into four types: ductile, brittle-ductile,ductileubrittle and britt1e. Among them, each type has its own geochemical characteristics: the Hetai gold deposit in Guangdong province for example, is a kind of mylonite type gold deposit in a ductile shear zone, and the gold ore has the forms of layer and vein; the Erjia gold deposit formed in a brittleuductile shear zone, and the gold ore, being of two types, mylonite type and cataclasticaltered rock type, has the form of vein; the Shangguan gold deposit, Henan Province, was located in a ductile-brittle shear zone, and the gold ore is of two types, cataclastic-altered rock type and quartz vein type; and the Linglong gold deposit occurs in a brittle shear zone, with the main gold ore of quartz vein type having the forms of vein and lens. Simulating experiments on tectono-controlled formation of gold ores gave us the idea that not only the samples underwent crack deformation, but also changes occurred in chemical composition of minerals, and also caused gold to be remobilized and finally filled into the newlyuproduced fissures.

South-Altai Mineralization Zone

Altai mineralization zone is located in the north-west of Xinjiang Uigur Autonomous Region.Throughout the zone 70 and more mineral species have been discovered.There are 46 mineral spe-cies reserve of which hag been verified.Altai is an importantest place of occurrence of beryllium,lithium,tantalum,niobium and other rare metals.It is also a producing area of high-qualitymuscovite,biotite and other mica.The precious stone,lade and marble are also produced there.

Metallogenic Processes:Evidencesfrom Zoning Patterns of Mineralization and alteration and fluid inclusion geochemistryin the Lehong Zn-Pb Deposit in Northeastern Yunnan, China

1 Introduction The large clusters of Zn-Pb deposits in northeastern Yunnan,located in the southwestern margin of the Yangtze Block,are an important part of the Sichuan-YunnanGuizhou Pb-Zn Poly-metallic Metallogenic Triangle Area

Mineralization Zoning in Yindongzi-Daxigou Barite-Siderite, Silver-Polymetallic Deposits in the Qinling Orogen, China

The Yindongzi\|Daxigou strata\|bound barite\|siderite, silver\|polymetallic deposits discovered in the Qinling orogen are hosted within flysch facies in a deep\|water fault\|controlled basin on the passive northern margin of the Qinling microplate. The orebodies occur in a series of hydrothermal depositional rocks. Mineralization zoning is characterized by Fe\|Ba←Ba\|Cu←Pb\|Ag→Cu\|Ag→Pb→Au. This is obviously a gradational transition mineralization from vent\|proximal mineralization to more distal mineralization. In this gradational transition between Chefanggou and Yindongzi, vent\|proximal mineralization consists of silver\|polymetallic orebodies (Pb\|Ag), which is the center of hydrothermal mineralization. The Chefanggou Ba\|Cu ore district in the west and the Yindongzi Cu\|Ag ore district in the east represent vent lateral mineralization. Distal mineralization in the west is represented by the Daxigou Fe\|Ba ore district while distal mineralization in the east is represented by the Pb ore district. Thick massive, laminated barren albite chert and jasperite, sometimes with minor silver\|ploymetallic mineralization of commercial importance, and pyritization in rocks feature more distal mineralization. Geochemical anomalies of Au\|As associations are found in ankerite phyllite and muddy sandstone. Actually, Au deposits are dominantly controlled by the late brittle\|ductile shear zone.

Geochemical Characteristics of Two Types of Ores from Jinshan Shear Zone-hosted Gold Deposit, Jiangxi, with a Discussion on the Mechanism of Two-stage Mineralization

Two types of gold ores,siliceous mylonite and quartz vein,formed at the first and second stages of mineralization respectively, can be clearly recognized in the shear zone-hosted gold deposit at Jinshan, Jiangxi.Similarity in REE and trace elements between the siliceous mylonite and the country rocks indicates that the ore metals were supplied by the surrounding strata during the first stage of mineralization.On the other hand, as indicated by fluid inclusion data,the ore-forming fluid at the second stage was of meteoric origin and the precipitation of gold was caused by phase separation.

Mineralogy and Geochemistry of the High-Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements(PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios(<0.1). In mid-ocean ridge basalts(MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral(PGM) grains were discovered from the samples, including laurite, erlichmanite, Os-Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os-Fe alloy and increased thereafter, with the fall in temperature. Primary Fe-Ni and Fe-Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high-pressure and low-pressure chromites. Low-pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high-pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.

Quantitative analysis of intrusive body morphology and its relationship with skarn mineralization——A case study of Fenghuangshan copper deposit, Tongling, Anhui, China

The shapes of intrusive body and contact zone might influence the formation and distribution of orebodies in skarn deposit.By taking Xinwuli intrusive body in Fenghuangshan copper deposit,Tongling,Anhui,China,as the research object,a new method was used to obtain the quantitative relationship between intrusion morphology and skarn mineralization.The first step of the method was to extract morphological characteristic parameters based on mathematical morphology and Euclidean distance transformation;then the quantitative relationship between the parameters and orebodies was analyzed;finally correlational analyses between the parameters and mineralization indices were conducted.The results show that morphological characteristic parameters can effectively indicate the location of concealed ore bodies in skarn deposit,with the following parts as advantageous positions of skarn mineralization:(1)the parts away from the1st trend surface in the range from?25to50m;(2)the convex parts about200m away from the2nd trend surface,around which the tangent plane of the intrusive body is approximately consistent with the trend surface;(3)the contact zones with angle between intrusive body original contact surface and trend contact surface ranging from35°to70°;(4)the parts with angle between intrusive body original contact surface and regional extruding far crustal stress ranging from50°to60°.These knowledge can be applied to more skarn deposits for future mineral exploration.

Evidence of Iron Mineralization Channels in the Messondo Area (Centre-Cameroon) Using Geoelectrical (DC &IP) Methods: A Case Study

A geophysical survey was conducted in the Kelle-Bidjocka village, Messondo subdivision, in the Centre Region, Cameroon. The data acquisition was made by combining Schlumberger profiling and electrical soundings along six (06) profiles of 1500 m in length for a total of 64 geoelectrical stations’ survey conducted through a variable mesh 100 m × 200 m, or 100 m × 300 m. The equipment used is the DC resistivimeter Syscal Junior 48 (Iris Instrument). Processing and modelling of field data are made by using the Res2Dinv, Qwseln and Surfer software. The investigation methods used are electrical resistivity (DC) and induced polarization (IP) methods. The analyses and interpretations have helped to highlight areas of weakness or conductive discontinuities (fractures, faults, shear zones, etc.) in Precambrian gneiss formations, sometimes undergoing weathering processes. They identify the weathering or mineralogical accumulation horizons, the most promising is a mineralization channel identified in the NE-SW direction. The highlighted mineralization is characterized by strong gradients of chargeability or polarization. Samples and other geological evidences observed in the area are used to associate the most polarizable structures with ferriferous formations. Weakly polarizable and particularly conductive backgrounds identified by the inverse pseudo-sections are thought to be sulphate minerals or groundwater targets for future hydrogeological studies.

Deep gold mineralization features of Jiaojia metallogenic belt,Jiaodong gold Province:Based on the breakthrough of 3000 m exploration drilling

Recently,continuous breakthroughs have been made about deep gold prospecting in the Jiaodong gold province area of China.Approximately 5000 t of cumulative gold resources have been explored in Jiaodong,which has thus become an internationally noteworthy gold ore cluster.The gold exploration depth has been increased to about 2000 m from the previous<1000 m.To further explore the mineralization potential of the Jiaodong area at a depth of about 3000 m,the Shandong Institute of Geological Sciences has drilled an exploratory drillhole named“Deep drillhole ZK01”to a depth of 3266 m.Hence,as reported herein,the mineralization characteristics of the Jiaojia metallogenic belt have been successfully documented.ZK01 is,to date,the deepest borehole with an gold intersect in China,and constitutes a significant advance in deep gold prospecting in China.The findings of this study further indicate that the depth interval of 2000 m to 4000 m below the ground surface in the Wuyi Village area incorporates 912 t of inferred gold resources,while the depth interval of 2000 m to 4000 m below the surface across the Jiaodong area possesses about 4000 t of inferred gold resources.The Jiaojia Fault Belt tends to gently dip downward,having dip angles of about 25°and about 20°at vertical depths of 2000 m and 2850 m,respectively.The deep part of the Jiaojia metallogenic belt differs from the shallow and moderately deep parts about fracturing,alteration,mineralization,and tectonic type.The deep zones can generally be categorized from inside outward as cataclastic granite,granitic cataclasite,weakly beresitized granitic cataclasite,beresitized cataclasite,and gouge.These zones exhibit a gradual transitional relation or occur alternately and repeatedly.The mineralization degree of the pyritized cataclastic granite-type ore in the deep part of the Jiaojia metallogenic belt is closely related to the degree of pyrite vein development;that is,the higher the pyrite content,the wider the veins and the higher the gold grade.Compared to the shallow gold ores,the deep-seated gold ores have higher fineness and contain joseite,tetradymite,and native bismuth,suggesting that the deep gold mineralization temperature is higher and that mantle-sourced material may have contributed to this mineralization.ZK01 has also revealed that the deep-seated ore bodies in the Jiaojia metallogenic belt are principally situated above the main fracture plane(gouge)and hosted within the Linglong Granite,contradicting previous findings indicating that the moderately shallow gold ore bodies are usually hosted in the contact zone between the Linglong Granite and Jiaodong Group or meta-gabbro.These new discoveries are particularly significant because they can help correct mineralization prospecting models,determine favorable positions for deep prospecting,and improve metallogenic prediction and resource potential evaluation.

Effects of grain size on landscape patterns in mineral resource zones:a case study of Wu’an,China

A mineral resource zone,rich in resources and energy,is intensively developed and disturbed by human activities,which causes an obvious change of landscapes.Taking Wu’an of Hebei Province,China,as a case study,this paper extracts landscape information of mineral resource zones through overlapping mineral resources distribution map and landscape pattern map.And then,various landscape indices are selected for analyzing the effects of grain size(30,60,90,120,150,180,210,240,270 and 300 m)on landscape patterns.Due to different kinds of landscape information transmitted by indices,the changing trends vary with the increase of grain sizes.Accordingly the landscape indices are classified into three types of effects:disturbance,continuity and sustainability,and each type of effect has its own optimal range for grain sizes.Then the optimal range of grain size on landscape patterns in mineral resource zones is gained through a comparison of the effects in various grain sizes of landscape indices.The best first domain of scale covers 30-90 m,with a suitable grain size of 30-60 m before intensive mining and a suitable grain size of 60-90 m after intensive mining.Besides,the suitable grain sizes for reflecting disturbance,continuity and sustainability before intensive mining are 30-60,30-60 and 30-90 m,respectively,however,the sizes are changed to 60-90,60-90 and 30-90 m,respectively,after intensive mining.The results are helpful for rational land use and optimal landscape allocation.

Geospatial Mapping of Singhbhum Shear Zone (SSZ) with Respect to Mineral Prospecting

Singhbhum Shear Zone is a highly mineralized zone having variety of minerals, predominantly those of uranium, copper and some sulphide minerals. From Remote Sensing data it is possible to decipher the regional lithology, tectonic fabric and also the geomorphic details of a terrain which aid precisely in targeting of metals and minerals. Mapping of mineralized zones can be done using Geospatial Technology in a GIS platform. The present study includes creation of various maps like lithological map, geomorphological map, contours and slope map using satellite data like IRS LISSIV and ASTER DEM which can be used to interprete and correlate the various mineral prospective zones in the study area. Even the alterations of the prevalent mineral zones can be mapped for further utilization strategies. The present work is based on the investigations being carried under ISROSAC Respond Project (Dept. of Space, Govt. of India SAC Code: OGP62, ISRO Code: 10/4/556).

Gold Mineralization Channels Identification in the Tindikala-Boutou Area (Eastern-Cameroon) Using Geoelectrical (DC &IP) Methods: A Case Study

To achieve the current study, geoelectrical surveys along six (06) profiles of 4 km long in a 100 m × 200 m grid defined according to the triangulation principle in the Ngoura area (Tindikala-Boutou villages) have been made through electrical sounding and profiling following Schlumberger array. The instrument is the resistivimeter Syscal Junior 48 (IRIS Instrument) which uses the electrical current. The data have been processed and modelled with Res2Dinv and Winsev softwares then interpolated with Surfer software. Electrical methods used are the Direct current (DC) and the Induced Polarization (IP). Interpretation and analyses of results from each investigation method highlight weak zones or conductive discontinuities and mineralized zones. Conductive zones have been identified as shear zones within granitic structures of the Precambrian basement, according to the geologic and tectonic background of the area. The structural trend of these shear zones is E-W. The mineralization within it is N-S and characterized by high values of chargeability, essentially in the eastern part of the area under study. This mineralization proves the presence of metalliferous or sulphide heaps disseminated in weathered quartz veins which cross shear zones. Also, the poor mineralization and conductive structures in shear zones characterize the groundwater zones. The intense activities of gold washers encountered in the area enable to link that mineralization to gold within quartz veins. The near surface gold mineralization is eluvial or alluvial, and in depth this mineralization is primary.

Preliminary Study of the Characteristics and Genesis of Arsenate Minerals in the Oxidized Zone of the Debao Skarn-Type Cu-Sn Ore Deposit in Guangxi

Through the study of the oxidized zone of the Debao skarn-type Cu-Sn deposit in Guangxi, the authorshave found 14 arsenate minerals, most of which are for the first time reported in China. They are mainly Cuarsenate minerals with subordinate Cu-Pb arsenate minerals and minor Fe-Pb-Ba varieties. Based on their paragenesis these minerals may be divided into the following series: (1) the clinoclasite-olivenite-cornwallite- cornubite- debaoite- copper silicarsenate association, (2) the scorodite- carminite- beudan-tite-bayldonite- duftite association, and (3) the scorodite-Ba-bearing pharmacosiderite- dussertite association. Arsenate minerals are formed generally in the oxidized zone of the sulfide-type deposits which lie in thewarm, humid and rainy torrid-subtropical zone with pH=6-8 and contain large amounts of arsenopyrite andcarbonate rocks.

中亚成矿域西部早二叠世金、镍重大成矿事件

晚古生代是地球历史上一个重要时期,蕴含着潘吉亚超大陆、规模最大冰期、最严重的生物大灭绝以及巨量矿产资源形成的关键信息。地处欧亚大陆腹地的中亚成矿域是全球最大的显生宙大陆增生区,以晚古生代大规模成矿为显著特色,尤其早二叠世(270~290 Ma)在中亚成矿域西部天山及邻区巨量金、镍爆发性集中成矿作用,造就出世界第二大金成矿省,形成了超过10000 t金,造就出具有世界特色的造山带岩浆型镍矿集区,形成了包括8个大型-超大型矿床在内的东天山、额尔齐斯、北山3个重要镍矿床集中区,镍资源达250万t,是一次全球罕见的金-镍时间耦合重大成矿事件。文章基于最新研究成果,系统论述了中亚成矿域西部早二叠世金、镍大规模成矿的时空分布和基本地质特征,探讨了该重大成矿事件的区域动力学背景和可能成矿机制。研究认为,早二叠世金矿床产于天山古缝合带附近的脆/韧性构造变形带,构成独具特色的大陆变形带金成矿系统,已有成矿理论难以涵盖,含碳碎屑岩系、地块抬升导致的大规模区域变质作用、多来源的流体作用、多期构造活化富集、多种因素耦合叠加等,可能是大规模金成矿的关键条件;早二叠世镍矿床沿天山、北山、阿尔泰地区深大断裂附近的镁铁-超镁铁质岩体线性展布,是全球造山带镍成矿作用最强烈、发现矿床数量最多的地区,俯冲熔/流体的交代岩石圈地幔/软流圈发生高程度部分熔融、区域超壳深断裂为玄武质岩浆提供快速运移的通道、壳源物质加入触发硫化物熔离、硫化物与多幕脉动侵位的岩浆反应是造山带岩浆型镍大规模成矿的关键。整体上,中亚成矿域西部早二叠世金、镍重大成矿事件表现为“时间耦合、西金东镍”的时空格局,但大规模成矿的全球和区域动力学背景、金与镍富集机制及成矿响应机理还是未解之谜。

黑龙江多宝山铜矿区韧性剪切变形时代及其对铜矿化改造的约束

黑龙江多宝山斑岩铜矿主要赋存于奥陶纪花岗闪长岩中,少量发育于奥陶纪花岗闪长斑岩及奥陶系多宝山组安山岩中,铜矿化以浸染状、细脉-浸染状为主。成矿过程经历了斑岩期、剪切变形期。矿区发育韧性剪切变形带,多宝山组、花岗闪长岩、花岗闪长斑岩、安山质凝灰角砾岩及矿体均发生了剪切变形作用,沿剪切面发育绢云母新生矿物。绢云母的坪年龄和正反等时线年龄分别为280.1±1.2 Ma和281.4±1.3 Ma、281.3±1.3 Ma,在误差范围内基本一致,限定矿区韧性剪切变形的时间为早二叠世(约280 Ma)。多宝山斑岩铜矿床主要成矿作用形成于斑岩期,成矿时代为早奥陶世(约475 Ma),早二叠世的韧性剪切变形作用对原生斑岩铜矿化进行了改造,使矿石的铜进一步富集,品位相对增高。

淮南矿区张集煤矿1410(3)工作面顶板风氧化带探查与评价

工作面顶板工程地质条件对工作面支架选型、围岩稳定性评价及安全回采具有重要理论与实际意义,以淮南矿区张集煤矿1410(3)上提工作面为研究对象,基于井下钻探探查工程,采用岩心鉴定与描述、X射线衍射分析等方法,开展了工作面顶板风氧化带探查与评价,获得了工作面基岩风氧化带深度及风化程度。结果表明:工作面顶板30 m范围内岩石存在明显的风氧化现象,基岩风氧化带深度在28~35 m,基岩风氧化程度表现为中等风化-残积土,风氧化带岩石颜色以黄色为主,风化裂隙发育,岩体结构表现为块状-碎裂状-土状,岩石风化后矿物成分以高岭石、蒙脱石、伊利石及绿泥石为主,含量可达60%以上,风氧化带内岩石较正常岩石结构破碎,工程地质特性下降,研究结果可对下一步工作面顶板管理及回采上限确定提供依据和指导。