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.

Lithostructural Control of the Gold Mineralization of the Douta Permit of African Star Resources (Kédougou-Kéniéba Inlier, Southeastern Senegal)

The Douta permit of African Star Resources/Thor Explorations, located in the southeast of Senegal, in the Kédougou-Kéniéba Inlier (western part of the West African Craton), is dominated to the East by metasedimentary formations such as greywackes, shales, graphitic shales, quartzites, cherts, claystones and breccias characteristic of the Dialé-Daléma basin. To the West, the mafic formations of the Mako volcanic belt are the most common. Metasedimentary rocks are associated with metavolcanosedimentary terms found at the contact zones between the two (2) Birimian groups. These different geological formations are cut by mafic dolerite and gabbro sills and/or dykes, as well as quartz and microgranite veins. The Douta gold project is crossed from North to South by the MTZ (Main Transcurrent Zone), generally oriented NE-SW and becoming N-S towards the North. The permit is characterized by several shear corridors. The rocks are affected by brittle, brittle-ductile to ductile deformations. The gold mineralization is hosted by a NE-trending shear corridor called the Makosa corridor (Makosa shear zone), therefore sub-parallel to the MTZ. It has a subvertical dip (75˚ to 85˚ to the NW). It is associated with a hydrothermal phase characterized by quartz-sericite-epidote-fine, disseminated pyrite and arsenopyrite ± albite ± chlorite paragenesis. These minerals testify to the existence of a low degree of metamorphism (greenschist facies, epizonal domain) in the area. However, metamorphism reaches amphibolite facies in some places, particularly in the vicinity of intrusive bodies, with the presence of hornblende (amphiboles) and plagioclase. The gold mineralization is mainly hosted by two (2) metasedimentary lithological units: meta-greywackes and shales.

Chemical and physical characteristics of quartz from gold deposits in the North China platform: relationship to gold mineralization

This paper seeks to identify macroscopic metallogenic mechanisms of various mineral deposits by studying microscopic typomorphic characteristics of typical minerals associated with the deposits and to reveal the mechanism of lattice gold in detail by studying both physical and chemical characteristics of quartz from representative gold deposits in the North China Platform.As part of their extensive research,the authors examine the relationship between trace elements with wall rock,the ore-forming media,and gold immigration of various types of gold deposits,including their salinity,type,temperature.These are key factors to revealing the mineralization mechanism,and indicators for mineral prospecting,exploration,mining,and metallurgical technology.In order to address the questions posed,the following methods were used:field investigations of geology and sampling of the representative gold deposits,physical study and chemical analysis of quartz including,but not limited to,fluid inclusions as well as their compositions and trace elements in quartz,the unit cell parameters,electron paramagnetic resonance spectrum(EPR),and infrared spectroscopic analysis(ISA).As a result of this study,the authors observe the following key findings:unit cell parameters of quartz vary with their contents of foreign elements including gold,paragenetic stage,wall rock type,and other factors;the higher the forming temperature and the lower the gold content in quartz,the smaller the unit cell parameters,and vice versa.Additionally,the EPR absorption lines resulted from the O–Al defect center.The density of these types of hole centers increases and the EPR signal strengthens when the temperature decreases.Based on the findings,the authors conclude that lattice gold exists in quartz.Gold,in the form of Au^(+)and/or Au^(3+),entering quartz and producing an electron–hole center,namely,the O-Au hole center,makes the center produce spin resonance absorption and results in the EPR absorption peak#I.Both unit cell parameters and EPR of quartz can potentially be used in mineral prospecting,relative ore-forming temperature determination,and grade control during mining.

2.5D Crustal Models Derived from Analytical Polynomial Separation Technique and Spectral Analysis of Gravity Data with Their Probable Gold Mineralization Migrations (Batouri, SE-Cameroon)

Geophysical surveying is crucial in the investigation of mineral resources in poorly exposed areas such as SE-Cameroon, a region known for its gold mineral potential. In this paper, gravity survey is carried out in the Batouri area, SE-Cameroon based on land gravity data from the Centre-south Cameroon. Therefore, an analytical polynomial separation program, based on least-square fitting of a third-degree polynomial surface to the Bouguer anomaly map, was used to separate the regional/residual components in gravity data. This technique permitted to better understand the disposition of the deep and near surface structures responsible of the observed anomalies in the Batouri area. Spectral analysis and 2.5D modelling of two profiles P1 (SW-NE) and P2 (N-S) selected from the residual anomaly map provided depths to basement. These depths constrain the gravity models along the profiles, indicating a variable thickness of the sedimentary infill with an approximate anomaly of -33 mGal. The 2.5D model of the basement shows a gravity body, with a signature suggesting two close and similar masses, which characterize the quartz-bearing formations associated here to granite and gneiss. Our work highlights a main heavy gravity: Gwé-Batouri anomaly, containing the major part of auriferous deposits located along the NE-SW direction. Further, three tectonic sub-basins bounded by normal faults have been highlighted at Guedal, Gwé, and Bélimban, in the south of Guedal-Bélimban depression. They are associated with the extension tectonics, more or less vertical tangential cuts and accidents that have affected the region. A correlation with previous results from tectonic, lithological and gold mineralization activities proves the relevance of the study and the need to intensify geophysical surveying in the area.

Mapping and Petro-Structural Study of Northern Komborodougou Formations, in Korhogo Gold District: A Substantial Contribution to the Discovery of a Potential Gold Mineralization in Birimian Greenstone Belts

The Gold District of Korhogo, in the northern region of C?te d’Ivoire, holds enormous potential for gold mineralizations, some of which are under exploration phase and others in exploitation phase (example of Tongon Gold Mine). Dormant since 1998, Mapping Services of most of the West African countries hardly provide geological maps at the scales of: 1/200,000, 1/50,000 and 1/25,000. This situation of unavailability of detailed geological maps does not help mining operators in the selection of prolific areas and also in the interpretation of in soil geochem anomies or gold mineralizations. Consequently, during the years 2020 and 2021, we have undertaken a campaign of geological mapping and petro-structural study of the northern sector of Komborodougou, located in the southern extension of Banfora Birimian Belt. This work, which allowed the realization of a geological map at 1/20,000 scale, reveals that: the mapped area includes three (3) major lithological units: 1) a volcano-sedimentary unit made up of metasediments (metaarenites, metasiltites and metaflyschs) and metavolcanites (metabasalts), which are metamorphosed and outcrop in the form of schists;2) a metaplutonic and intrusive unit composed on the one hand of quartz-diorites and metagabbros, and on the other hand of granites and granodiorites;3) and finally, a unit of dikes formed by microgranites, microgabbros, aplites and quartzites. The volcano-sedimentary complex is affected by a regional fold with an axis subparallel to the regional tectonic grain and an S1 schistosity oriented NE-SW to NNE-SSW with steep dips (>60o), except for those of the metaflyschs which are weak (o);a regional NW-SE compression would be at the origin of the setting of this schistosity. The volcano-sediment and metaplutonite complex is crossed in a NNE-SSW direction by a senetral shear-zone or main shear-zone and secondary shear-zones oriented sometimes NE-SW or N-S. These shear-zones are intersected by more or less dextral or senestral strike-slip faults of NW-SE and E-W trends. N-S to NNE-SSW (N0o - N20o) and NW-SE (N130o - N160o) vein systems associated with the various shear-zones are the hosts of the gold mineralization in the region. These veins have been mined by orpaillors for more than two decades. The northern sector of Komborodougou is in the NNE continuity of the gold mineralization highlighted by the mining company Mako Gold Sarl on its Gogbala and Tchaga prospects, Napie project.

Characteristics of Gold and Its Mineralization Style in the Boulon Djounga Eastern Perimeter of Liptako Mining Company (Central Southwestern Niger)

The Boulon Djounga eastern perimeter is part of the Tiawa operating permit of the Société des Mines du Liptako (SML), located in the central southwestern part of Liptako (Niger). In this study, we used field data, Reverse Circulation (RC) surveys and chemical analyzes of gold to determine the characteristics of gold and its mineralization style. The eastern perimeter of Boulon Djounga is represented by a succession of metabasalts and metasediments both intersected by intrusions of quartz and dolerite dykes, and covered by sandstone and clayey rocks. Gold is present in low contents (0.00 - 0.30 ppm) in the sedimentary cover and in medium (0.30 - 1.00 ppm) or high contents (1.00 - 4.534 ppm) in the metasediments, and in the gray quartz veins and locally in the volcanics. It exists in a disseminated state or in a concentrated state in the surrounding areas in the form of discrete grains associated with sulphurous minerals (pyrite: FeS2, chalcopyrite: CuFeS2 or arsenopyrite: FeAsS). The presence of gold in the quartz veins, and the NE-SW and NW-SE orientations of the ore bodies suggest that the eastern Boulon Djounga gold mineralization would be established during a late magmatic extensive phase.

Gold Mineralisation in the Intiédougou Prospect (Diébougou District) in Southwest Burkina Faso, West African Craton

The Intiédougou located in the Houndé Birimian greenstone belt has been the subject of several mining and geoscience studies that have led to the discovery of mineralized gold targets. One of these mineralized targets has prompted work that raises the issue of control factors for the gold mineralization of the prospect. The methodology used in this study combines a study of core drill hole data located in the area and laboratory studies. The Intiédougou sector is based on andesito-basaltic, andesitic interstratified volcanoclastite rocks and Tarkwaïen type detrital sedimentary rocks caught in a vice in the volcano-sedimentary unit. Lithostructural analysis of the sector shows that the subvolcanic rocks bearing gold mineralization are subjected to heterogeneous ductile to brittle deformations and affected by hydrothermalism evolving at stages marked by large fissure fillings. These hydrothermal phases evolve in the zones of expansion created by the brittle deformations that have contributed to the deposits of different types of gold-enriched sulphides. These different phases of hydrothermal destabilization generally of low degree accompany the tardi to post-eburnean brittle tectonics. This deformation system is favorable to the establishment of gold mineralization in the form of vein bodies. The overimposition of deformed and altered areas suggests a genetic relationship between deformation and hydrothermal activity. In conclusion, the mineralization of Intiédougou in vein styles, set up in a volcanic arc environment with a paragenesis of gold-pyrite deposit ± chalcopyrite would be controlled by the structural aspect and accompanied by hydrothermal alteration.

Multistage mineralization in the Haoyaoerhudong gold deposit, Central Asian Orogenic Belt: Constraints from the sedimentary-diagenetic and hydrothermal sulfides and gold

The Central Asian Orogenic Belt,as one of world-class gold economic belts,preserves a number of giant,large black shale-hosted gold deposits,while it is still debated for origin of sulfides and gold mainly due to lack of identification for multiple stages of sulfides.The Haoyaoerhudong gold deposit is hosted in a sequence of Mesoproterozoic carbonaceous and pyritic slate,phyllite,and schist that form a tight syncline along the north margin of the North China Craton.Detailed petrography of the host rocks and mineralization have defined five stages of pyrites.The earliest form of pyrite(Py_(1))occurs as fine-grained dispersed pyrite in black carbonaceous slate and medium-to coarse-grained disseminated pyrite in pyrite-rich layers,contains relative low gold and high arsenic content,indicating a syn-sedimentary or diagenetic in origin.Stage Ⅱ pyrite(Py_(2))occurs with garnet and quartz inclusions and Py_(3) occurs as pyrite veins,contains higher gold and lower As content,and are interpreted to have formed from the dissolution-reprecipitation of Py_(1) during the peak metamorphism or post-peak metamorphism.Stage Ⅳ pyrite(Py_(4))from the pyrite-quartz veins crosscut the metamorphic garnet,contains the highest gold concentrations and other trace elements,and is considered to have formed post-peak metamorphism.Abundant native gold,electrum,and maldonite occur as inclusions within Py_(4) and monazite and in fractures that crosscut garnet.While,Py_(5) with typical remobilized feature is thought to be a product of melting of former pyrites(Py_(1) to Py_(4))triggered by the large-scale Hercynian magmatism.The sedimentary/diagenetic Py_(1) have δ^(34)S values that range from +12.4‰to +16.2‰.Later generations of sulfides,including Py_(2) to Py_(5),and Ccp_(2) to Ccp_(3),have δ^(34)S values from +9.5‰to +12.7‰.Monazite with maldonite inclusions from quartz-pyrite veins yielded an intercept age of 341.3±6.6 Ma,while coarse grained monazite associated biotite along fractures in the reefs yielded an intercept age of 254.6±8.2 Ma.The paragenetic,textural,chemical,and isotopic data suggest three distinct gold producing episodes at Haoyaoerhudong gold deposit.Gold and arsenic were clearly initially concentrated in organic muds,and enriched along the structures of diagenetic arsenic-rich pyrite.Subsequently,accompanying metamorphism and deformation,gold was liberated from the dissolution of diagenetic pyrites to form the pyrite veins.Finally,accompanying transformation of pyrite into pyrrhotite,gold was released into the metamorphic fluids to become concentrated as native gold,electrum,and maldonite in pyrite-quart veins.Monazite with age of 341 Ma from quartz-pyrite veins suggests that the third major gold mineralizing event in Haoyaoerhudong occurred before the Hercynian magmatism,suggesting that the Haoyaoerhudong deposit is a typical orogenic gold deposit rather than intrusion-related deposit.

Metallotectic Context of the Mineralization of the Tondabo Gold Prospect(Brobo,Center of Cote d’Ivoire,West Africa)

The gold mineralization of the Tondabo prospect, located in the northern part of the Oumé-Toumodi-Fettêkro greenstone belt, is mainly hosted in the rhyodacite and to a lesser extent in the mafic volcanics (volcanic lavas and volcanoclastites). These rocks were affected by a hydrothermal alteration marked by quartz veins and veinlets associated with crystals of carbonates, sericite, epidote and sulfides. This hydrothermal alteration induced a pervasive alteration of the surrounding bodies with silicification, chloritization, carbonation and sericitization of the feldspars. The metalliferous paragenesis contains an abundant pyrite, with rare pyrrhotite and chalcopyrite. This mineralization indicates that the Tondabo gold prospect exhibits lithological control. The mineralized deposits are generally affected by a S1 schistosity oriented mainly N000-010° and minority N040-050° with a general dip of 60°-80°to the West;however with rare N-S orientations with a dip of 60°-80° to the East. The drilling intervals show that the highest gold contents are linked to the quartz-carbonates veins and veinlets, which are located in the highly deformed zones, characterizing local shear zones.

Alteration Typology and Geochemical Signatures of the Napélépéra Gold-Bearing Granodiorite in South-West Burkina Faso (West Africa)

The characterization of the relationships between mineralization and hydrothermal alteration is an essential element in understanding gold deposits. In south-west Burkina Faso, the Napélépéra mineralisation, the mobility of chemical elements and alteration-mineralization relationships were studied by means of selected core drilling and geochemical analyses using ICP-MS (Inductively Coupled Plasma Mass Spectrometry) and ICP-AES (Inductively coupled plasma atomic emission spectroscopy). The mineralised granodiorite is grey porphyroid with quartz, plagioclase, biotite and amphibole. It is metaluminous and located in the tholeiitic series. The Na2O + CaO versus Fe2O3 + MgO alteration diagram divides the samples according to alteration dominance. Chloritisation and carbonation are the main alterations. There is a relationship between gold mineralisation at Napélépéra and alteration, and the paragenesis of gold + pyrite ± carbonate ± silica ± sericite is the main characteristic. Carbonation is the result of fluid input in the shear corridor of the mineralised zone. The mass balance of comparative metals in the proximal and distal zones of the mineralisation shows the absence of metals, while As, Hg, Ag and Bi are strongly enriched from the distal zone to the mineralised zone. The oxides associated with the mineralisation are mainly NaO, SrO and CaO.

Formation of the Devonian Fengtai Hydrothermal Brine Basin and the Metallogeny of Gold and Lead-Zinc Mineralizations in Shaanxi

The study of the relationships between the hydrothermal sedimentary formations and the gold andlead-zinc mineralizations in the Devonian Fengtai basin in Shaanxi shows that there was a hydrothermal brine sedimentary event which was inserted into the normal sedimentary background from the late Middle Devonian to the early Late Devonian. This event is closely related to gold and lead-zinc mineralizations in this area.

Geochemical and geochronological characteristics of the Um Rus granite intrusion and associated gold deposit,Eastern Desert,Egypt

The Um Rus tonalite-granodiorite intrusion(~6 km2)occurs at the eastern end of the Neoproterozoic,ENE-trending Wadi Muba rak shear belt in the Central Eastern Desert of Egypt.Gold-bearing quartz veins hosted by the Um Rus intrusion were mined intermittently,and initially by the ancient Egyptians and until the early 1900 s.The relationship between the gold mineralization,host intrusion,and regional structures has always been unclear.We present new geochemical and geochronological data that help to define the tectonic environment and age of the Um Rus intrusion.In addition,field studies are integrated with EPMA and LA-ICP-MS data for gold-associated sulfides to better understand the formation and distribution of gold mineralization.The bulk-rock geochemical data of fresh host rocks indicate a calc-alkaline,metaluminous to mildly peraluminous,I-type granite signature.Their trace element composition reflects a tectonic setting intermediate between subduction-related and within-plate environments,presumably transitional between syn-and post-collisional stages.The crystallization age of the Um Rus intrusion was determined by in situ SHRIMP 206 Pb/238 U and 207Pb/235U measurements on accessory monazite grains.The resultant monazite U-Pb weighted mean age(643±9 Ma;MSWD 1.8)roughly overlaps existing geochronological data for similar granitic intrusions that are confined to major shear systems and are locally associated with gold mineralization in the Central Eastrn Desert(e.g.,Fawakhir and Hangaliya).This age is also consistent with magmatism recognized as concomitant to transpressional tectonics(D2:~650 Ma)during the evolution of the Wadi Mubark belt.Formation of the gold-bearing quartz veins in NNE-SSW and N-S striking fault segments was likely linked to the change from transpressional to transtensional tectonics and terrane exhumation(D3:620-580 Ma).The development of N-S throughgoing fault arrays and dike swarms(~595 Ma)led to heterogeneous deformation and recrystallization of the mineralized quartz veins.Ore minerals in the auriferous quartz veins include ubiquitous pyrite and arsenopyrite,with less abundant pyrrhotite,chalcopyrite,sphalerite,and galena.Uncommon pentlandite,gersdorffite,and cobaltite inclusions hosted in quartz veins with meladiorite slivers are interpreted as pre-ore sulfide phases.The gold-sulfide paragenesis encompasses an early pyrite-arsenopyrite±loellingite assemblage,a transitional pyrite-arsenopyrite assemblage,and a late pyrrhotite-chalcopyrite-sphalerite±galena assemblage.Free-milling gold/electrum grains(10 sμm-long)are scattered in extensively deformed vein quartz and in and adjacent to sulfide grains.Marcasite,malachite,and nodular goethite are authigenic alteration phases after pyrrhotite,chalcopyrite,and pyrite and arsenopyrite,respectively.A combined ore petrography,EPMA,and LA-ICP-MS study distinguishes morphological and compositional differences in the early and transitional pyrites(PyⅠ,PyⅡ)and arsenopyrite(ApyⅠ,ApyⅡ).Py I forms uncommon small euhedral inclusions in later PyⅡand Apy II.PyⅡforms large subhedral crystals with porous inner zones and massive outer zones,separated by narrow As-rich irregular mantles.The Fe and As contents in PyⅡare variable,and the LA-ICP-MS analysis shows erratic concentrations of Au(<1 to 177 ppm)and other trace elements(e.g.,Ag,Te,and Sb)in the porous inner zones,most likely related to discrete sub-microscopic sulfide inclusions.The outer massive zones have a rather homogenous composition,with consistently lower abundances of base metals and Au(mean 1.28 ppm).The early arsenopyrite(Apy I)forms fine-grained euhedral crystals enriched in Au(mean 17.7 ppm)and many other trace elements(i.e.,Ni,Co,Se,Ag,Sb,Te,Hg,and Bi).On the other hand,ApyⅡoccurs as coarsegrained subhedral crystals with lower and less variable concentrations of Au(mean 4 ppm).Elevated concentrations of Au(max.327 ppm)and other trace elements are measured in fragmented and aggregated pyrite and arsenopyrite grains,whereas the undeformed intact zones of the same grains are poor in all trace elements.The occurrence of gold/electrum as secondary inclusions in deformed pyrite and arsenopyrite crystals indicates that gold introduction was relatively late in the paragenesis.The LAICP-MS results are consistent with gold redistribution by the N-S though-going faults/dikes overprinted the earlier NNW-SSE quartz veins in the southeastern part of the intrusion,where the underground mining is concentrated.Formation of the Um Rus intrusion and gold-bearing quartz veins can be related to the evolution of the Wadi Mubarak shear belt,where the granitic intrusion formed during or just subsequent to D2 and provided dilatation spaces for gold-quartz vein deposition when deformed by D3 structures.

Genesis and magma fertility of gold associated high-K granites:LA-ICP-MS zircon trace element and REEs constraint from Bakoshi–Gadanya granites in NW Nigeria

High-K granites dominate the rock units in the Bakoshi and Gadanya areas located in the northwestern Nigerian subshield,part of the Trans-Saharan Belt,West Africa.In this contribution,the LA-ICP-MS zircon trace element revealed the fertility of magma responsible for the high-K granites that hosts the Bakoshi–Gadanya gold mineralization.Two likely metallogenic granites types are 1)Gadanya alkali granite,with high Ce^(4+)/Ce^(3+)(mean 1485)and limited range of Eu anomalies may likely be associated with the gold mineralization,and 2)Bakoshi porphyritic granite,Jaulere biotite granite,Shanono coarsegrained granite,and Yettiti granite,all have low Ce^(4+)/Ce^(3+) ratios(mean\100,except second Bakoshi granite D2-1)with wider ranges of Eu/Eu^(*) values,thus are considered reduced granites.These reduced granites have oxygen fugacity values and Eu anomalies comparable to reduced granites associated with tin belts in Myanmar and Zaaiplaats granites in Bushveld Complex,South Africa.Ti-inZircon thermometric study revealed two thermal regimes during the crystallization of the Bakoshi–Gadanya granites:the high temperature(746–724℃):Shanono coarsegrained granite,Bakoshi granite D2-1,and Jaulere biotite granite;and relatively low temperature(705–653℃):Bakoshi porphyritic granite D1-1,Yettiti medium-grained granite,and Gadanya alkali granite.Zircon trace elements including U,Yb,Y,Nb,and Sc ratios constraint the magma source of Bakoshi–Gadanya granites to an enriched mantle metasomatized during the subduction process before its melting.Except for Gadanya alkali granite,fractionation of titanite and apatite dominate the magma evolution with limited amphibole fractionation.Melt that crystallized Gadanya alkali granite is rather saturated in zircon without accessory titanite or apatite.

Geometry and kinematics of brittle deformation in the Central Cameroon Shear Zone (Kékem area): Implication for gold exploration within the Central Africa Fold Belt in Cameroon

The Central Africa Fold Belt(CAFB)is a collision belt endowed with gold deposits in Eastern Cameroon area mined for about 50 years.However,favorable areas for gold exploration are poorly known.This paper presents(1)the kinematics of the brittle deformation in the Kékem area in the SW portion of the Central Cameroon Shear Zone and(2)constraints gold mineralization events with respect to the collisional evolution of the CAFB.The authors interpret that the conjugate ENE to E and NNW to NW trending lineament corresponds to the synthetic(R)and the antithetic(R’)shears,which accompanied the dextral slip along the NE to ENE striking shear.The latter coincides with the last 570-552 Ma D3 dextral simple shear-dominated transpression,which is parallel to the BétaréOya shear zone hosting gold deposits.Gold mineralizations,which mainly occurred during the last dextral shearing,are disseminated within quartz veins associated to Riedel’s previous structures reactivated due to late collisional activities of the CAFB as brittle deformation.Gold mineralizations occurred mainly during the 570-552 Ma D3 event.The reactivation,which might be due to dextral simple shear during mylonitzation,plausibly remobilized the early gold deposits hosted in syn-compressional rocks and/or possibly focused deep-sourced fluid mixed with those released by dehydration.Therefore,the Central Cameroon Shear Zone where Kékem is located,and which shows similar petrographical and structural features to those controling Batouri gold district,is a target area for gold exploration in Cameroon.

Ground Electromagnetic and Electric Studies for Um Salim Gold Mine, Central Eastern Desert, Egypt

Horizontal Loop Electromagnetic (HLEM) and Induced Polarization (IP) methods have been carried out within Um Salim gold mine area. The study area reveals special importance, as it comprises rock units, which show some indication of the presence of various mineralization. The result of HLEM has shown significant and well-defined conductive zones are recorded along with the four used frequencies (110 Hz, 440 Hz, 1760 Hz, and 7040 Hz) at the station 2,782,900 and station 2,782,880 of two (HLEM) profiles (596,050 N & 596,240 N) respectively, that may reflect the sources of the conductive bodies are situated at shallow depths continued to considerable depths. The result of IP exhibits a strong anomalous zone centered at stations 140 and 240, with chargeability values ranging (37 to more than 120 mV/V) on chargeability model section, and corresponding to high resistivity on resistivity model section which may reflect considerable surface and subsurface disseminated mineralization. Through the integration between HLEM and IP a core drilling is recommended at station 140 on IP profile which coincides with station 2,782,850 on HLEM profile (596,240 N) to a depth of concerning 100m take a look at the thickness, depth, and grade of mineralization.

Locating Mechanism of Quartz Vein Gold Deposits in Rushan, Shandong Province

According to the differences in ore-controlling structural systems and the characteristics of host rocks, textures and structures of ores and mineral associations of ores, quartz vein-type gold deposits in the Rushan area can be divided into the Rushan and Tongling styles. Rushan style gold deposits, occurring in the Kunyushan complex, include Rushan, Tangjiagou and Tongxishan gold mines. They are distributed along four NNE-trending and sinistral, compresso-shear faults with a right stepping array. A prominent characteristic of the gold mineralization is that the orebodies in neighbouring gold deposits distributed in a single ore-controlling fault zone take opposite pitches. Study of the locating structures of the quartz vein gold deposits shows that the Rushan-style gold deposits are characterized by NNE and NE zoning. Therefore, the intersections of the NE direction of the known gold deposit and the neighbouring NNE-trending fault zones are favourable for looking for gold deposits, and the ends of

GEOCHEMICAL REASERCH ON ORE-CONTROLLING STRUCTURE IN LIAODONG LUOQUANBEI-BAIYUN GOLD MINERAL BELT

In recent2 0 years,because of the finding ofmany large- superlargegold deposits,we re- new the theories for prospecting and gain many things and conceptions.The current geo- chemical and gold- forming theories underline the importance of the early submarine volcano- sedimentation,metamorphic differention,sedimentation of terrigenous clastics,thermal spring and it’s sedimentation,syngenesis process and other hypergene supplying the source for metallogenic materials.According to the study for source bed(rock) and depsitional for- mation of gold,we find that gold will be gradually enriched and mineralized in source bed (rock) ,because of variousgeologicprocesses,such as regional metamorphism ormigmatiza- tion,geothermal bittern,volcanism. The ore- control of deep and giant fault and ductile shear beltand tectono- flash space is emphasized,especially,we should notice the long- term, succession and multistage of the

Geochronology and zircon geochemistry of auriferous intrusions in the Bumo deposit,Hainan Province,China

Intrusion-related gold deposits(IRGS)are a lowgrade,large-tonnage exploration target.Recently,auriferous magmatic rocks were found in the Bumo deposit of the Gezhen shear zone in Hainan Province,China.However,the geochronology and geochemical characteristics of the intrusions,as well as the mineralization potential,are still unclear.Field and petrographic work show that the sulfidebearing intrusions can be divided into diorite porphyrites,quartz monzodiorites and monzodiorites.Zircon LA–ICP–MS U–Pb dating demonstrates that diorite porphyrites,quartz monzodiorites and monzodiorites were formed at104±1,114±1,114±1 Ma,respectively.In addition,sulfides in Yanshanian intrusion-related gold mineralization haveδ;S values of 0.2–4.4%,lower than those in Hercynian-Indosinian(1.9–9.8%)orogenic deposits(ca.219–378 Ma)in the Gezhen shear zone.In addition,all these intrusions display close correlations between Eu/EuN*with Th/U,consistent with the differentiation of amphibole,apatite and titanite from a hydrous melt.Moreover,zircon Eu/EuN*in the intrusions are higher than0.4,demonstrating that the magmatic rocks have high water contents and oxygen fugacity values,favorable for gold mineralization.Consequently,the Yanshanian magmatic rocks can be a new potential gold exploration target in the Gezhen shear zone.

Evaluation of the Geological and Metallogenic Potential of Koffissiokaha Permit, Area of Katiola, Côte d’Ivoire

The semi-industrial permit of Koffissiokaha, south-eastern area of Katiola, is located in the northern part of Fêtêkro Birimian Greenstone Belt (C&ocirc;te d’Ivoire). This permit, applicated by the company Blue-Hill Exploration Sarl (BHEX), is in the southern continuity area of Lafigué permit (Endeavour Mining). Blue-Hill will have to work to highlight potential gold mineralization, quantify it (resource calculation) and initiate administrative procedures to obtain a Semi-Industrial Exploitation Authorization (AESI). Our recent works, including field mapping coupled with petrographic and microstructural studies, are therefore intended to contribute to the knowledge of the geology and to the evaluation of the gold potential of this permit. They suggest that Koffissiokaha permit includes four major lithologic units: 1) a sedimentary unit formed by metaarenites and metasiltites, 2) a unit of mafic pyroclastites (cinerites, tuffs and volcanic breccias) 3) a plutonic unit of metagabbro and finally, 4) a lode-type unit made up of metarhyodacites. The metamorphism that affected the volcano-sedimentary rocks is of low grade to greenschist facies. On the structural level, deformations with variable gradients are noted. The major planary structure, the schistosity, is oriented N20 - 40 with weak (&#176;), moderate (50&#176;- 60&#176;) and steep dips (>70&#176;) or subvertical. The faults generally correspond to narrow dextral or senestral shear-zones (75&#176;) towards south-east or subvertical. They are most often intersected by late strike-slip faults-oriented NW-SE, NNW-SSE and N-S. Quartz veins are associated with faults or deformation zones. They are generally oriented N20 to N40, with weak (&#176;), moderate (55&#176;- 65&#176;) and steep dips (>75&#176;). Orientations of joints and fractures are mostly subparallel to the plans of schistosity, shears and most of quartz veins. However, ENE, WNW and N-S fractures are also distinguished. The sulphide paragenesis consists of pyrites (and pyrrhotites), arsenopyrites and chalcopyrites. Gold mineralization is controlled by both structural and hydrothermal parameters.

Geodynamics of decratonization and related magmatism and mineralization in the North China Craton

The North China Craton(NCC)experienced strong destruction(i.e.,decratonization)during the Mesozoic,which triggered intensive magmatism,tectonism and thermal events and formed large-scale gold and other metal deposits in the eastern part of the craton.However,how the decratonization controls the formation and distribution of large-scale of gold and other metal deposits is not very clear.Based on a large number of published data and new results,this paper systematically summarizes all the data for the rock assemblages,chronology,geochemistry and petrogenesis of Mesozoic magmatic rocks,as well as for the mineralizing ages of gold and other metal deposits and the evolution of the Mesozoic basins in the eastern NCC.The results are used to restore the extensional rates of Mesozoic to Cenozoic basins and the strike-slip distance of the Tanlu Fault,to ascertain the location of the Paleo-Pacific plate subduction zones during the Mesozoic to Cenozoic,and to reconstruct the temporal and spatial distribution of Mesozoic gold and other metal deposits and magmatic rocks in the eastern NCC.It is obtained that the magmatism and mineralization in the eastern NCC westward migrate from east to west during the Early to Middle Jurassic,but they eastward migrate from west to east during the Early Cretaceous.The metallogenesis of these deposits is genetically related to magmatism,and the magmas provided some ore-forming materials and fluids for the generation of metal deposits.The geodynamic mechanism of decratonization and related magmatism and mineralization is proposed,i.e.,the westward low-angle subduction of the Paleo-Pacific slab beneath the NCC formed continental magmatic arc with plenty of porphyry Cu-Mo-Au deposits in the Jurassic,similar to the Andean continental arc in South America.The mantle wedge was metasomatized by the fluids/melts derived from the subducting slab,laying a material foundation for hydrothermal mineralization in the Early Cretaceous.While the rollback of the subducting slab with gradually increasing subduction angle and the retreat of the subduction zones during the Early Cretaceous induced strong destruction of the craton and the formation of extensive magmatic rocks and large-scale gold and other metal deposits.