Source Of Gold Research Articles

Inhomogeneities of the earth’s crust of the Aldan-Stanovoy shield along the 3-DV profile (Eastern Siberia, Russia

Profile 3-DV (Skovorodino-Tommot) crosses in the sublatitudinal direction the Stanovoy and Aldan megablocks of the Aldan-Stanovoy shield. As the basic elements of the Earth’s crust section along the profile 3-DV, a technique was adopted for identifying regional inhomogeneities of the lithosphere based on the results of the analysis of seismic and gravimetric data with subsequent typification of their nature. According to the SRM-CMP data, in the upper part of the section (up to 35 km) of the Aldan megablock, the Yakokut and Chulman heterogeneities are distinguished, and the Stanovoy megablock — the Kalara-Dzhugdzhur heterogeneity. The Yakokut and Chulman seismic inhomogeneities in the gravitational field correspond to minima with an the amplitude of up to 25 mGal. The gravitational field of the Kalara-Dzhugdzhur heterogeneity is mosaic and reflects its block structure.
 It is shown that the deep structure of the Aldan megablock in the area of the 3-DV profile is determined by the Yakokut granite-gneiss dome and Chulman sublateral decompaction zone, and the upper part (0—25 km) of the Stanovoy megablock is represented by the Kalar-Dzhugdzhur structure, composed of the Stanovoy complex of rocks and blocks of highpressure granulites. A significant (up to 10 km) increase in the thickness of the earth’s crust of the Aldan megablock is explained by the presence of the upper layer juvenile crust formed in the Paleoproterozoic as a result of regional metamorphism of igneous rocks. The Earth’s crust of the Stanovoy megablock is tectonically rebuilt for almost the entire thickness of up to 40 km during the Mesozoic collision of the Precambrian North Asian and Sino-Korean cratons.
 The Yakokut granite-gneiss dome, in accordance with the proposed model of the structure of the Earth’s crust of the Aldan megablock, is the ore-controlling structure of the Central Aldan gold-bearing region, and highpressure granulites of the Zverevsky block of the Kalara-Dzhugdzhur heterogeneity of the Stanovoy megablock served as a source of gold in the Chako-Berkakit ore cluster.

Trace elements in pyrite and pyrrhotite in the Pitangui Orogenic Au deposit, Pitangui greenstone belt, São Francisco Craton: Implications for the ore-forming fluids and metal sources

Orogenic Au deposits represent one of the largest sources of gold in the world and in Brazil, particularly at the Quadrilátero Ferrífero, southeastern portion of the São Francisco Craton. In the last decades, advances in in-situ analytical techniques allowed a detailed investigation of the chemistry of sulfides. This can reveal information about the origin and composition of the mineralizing fluids, potential sources of metals and sulfur and the fluid-rock interaction during the ore-forming processes. In this paper we combine Electron Microprobe Analysis and LA-ICP-MS analyses to put constraints on the nature and evolution of the Pitangui gold deposit. The Pitangui deposit represents an important Orogenic Au deposit hosted in clastic metasedimentary rocks of the Pitangui greenstone belt, northwestern portion of the Quadrilátero Ferrífero. Detailed drill hole, petrographic observations and in-situ chemical analyses of the hydrothermal alteration zones show that pyrite is the dominant ore mineral in the deposit and two possible origins are suggest including (i) syngenetic pyrite development at the early stages of the greenstone belt evolution and (ii) epigenetic pyrite, which is associated with hydrothermal processes during the Orogenic Au event. Syngenetic pyrite (PyI) has high Co, Bi, Pb, Sb, Te, Se, Ag and Au concentrations. The PyI could represent an important source of metals, a set of trace elements and likely sulfur for the later Orogenic Au mineralization. Epigenetic pyrites (PyII, PyIII and PyIV), conversely, are mainly found in association with hydrothermal minerals and within the mineralized carbonate-quartz-vein. The variations at Co, Ni, Pb, Te, Sn, Se, As, Bi, Sb, Ag, Mo and W in the epigenetic pyrite indicate that the dehydration PGB sequences during orogenesis constitutes the main fluids sources. The PyV, in turn, only appears at metamafic dyke, but its origin remains unclear.

Microscopic and NanoSIMS characterization of black shale-hosted pre-kinematic pyrites: Possible gold source of the orogenic gold deposits in the Truchas Syncline (Variscan Iberian Massif)

The Truchas Syncline contains orogenic gold deposits (OGDs), hosted mainly by the Armorican Quartzite Fm. In order to look for the source of gold in these deposits, pre-kinematic sulphides from black shales from the overlying Luarca Fm. were studied using both optical and scanning electron (SEM) microscopy, as well as nanoscale secondary ion mass spectrometry (NanoSIMS). NanoSIMS images allowed the observation of relevant structures (pyrite with high As content nodules) hidden to SEM.Microscopy and 36S, 75As32S, 75As, 75As34S, and 197Au mappings, as well as δ34S analysis (‰ Vienna-Canyon Diablo Troilite) allowed 4 types of pyrite to be characterized. According to their sequence of deposition, the pyrite types identified are the following: (1) framboid nuclei (FmPy), with δ34S between +4.1‰ and +57.5‰; (2) overgrowths (OgPy), with presence of Au, As and δ34S of approximately +20.5‰; (3) pyrite with high As content (AsPy), replacing previous pyrites, with δ34S of approximately +23‰, nodular shapes and non-detected Au; (4) subhedral pyrite (ShPy), with δ34S of approximately +19.7‰ and Au and As distribution showing (a) nuclei, (b) rims with Au and As and (c) structures interpreted as replacements of previous pyrite. Luarca Fm. pyrite framboids reach 75 µm in size, larger than framboids described in most previous NanoSIMS work, with microcrystals sufficiently large to be analyzed without contamination from edge effects. The FmPy formed in early diagenetic conditions by dissimilatory reduction of marine sulphate plus Rayleigh distillation or anaerobic oxidation of methane processes. The first FmPy nuclei formed in the periphery of framboids, and then started to form in the central region until completion of the framboidal structure. Growth of OgPy, AsPy and ShPy corresponded to more advanced diagenetic conditions, although the last stage of ShPy growth followed an aggregation model, in which ShPy metamorphic pyrites grew over ShPy diagenetic pyrites.The sulphur isotopic signature of the four types of pyrite is in good agreement with a source from Ordovician marine sulphate. A hypothesis stating that the source of Au in OGDs in the district could be in Luarca Fm. is supported by the results of the present research. Firstly, a source of Au in the district could have been the replacement of previous pyrites by AsPy and the release of Au to the system, instead of the framboidal to euhedral pyrite recrystallization process observed in other gold deposits. Secondly, by the correspondence between δ34S isotopic signature of the pyrites from Luarca Fm. and those from sulphides in OGDs. However, these results do not rule out other possible sources.

Geochemistry of Pyritic Mudstones from the Singa Formation, Malaysia: Insights into Gold Potential, Source of Sulfur and Organic Matter

Major trace element analyses, including pyrite chemistry of pyritic mudstones of shallow-marine Singa Formation of Pennsylvanian–Early Permian age have been carried out to assess gold potential, the source of sulfur and organic matter. Regionally, Singa Formation spatially correlates with the Bohorok Formation (Sumatra, Indonesia), the Kaeng Krachang group (Thailand), and the Lebyin group (Burma or Myanmar). In Southeast Asia, this formation is important because it has a record of glacial processes that occurred along the northern margin of Gondwana in the Late Paleozoic age. This study has revealed that mudstones of the Singa Formation, which contain lonestones of glacial origin, deposited under suboxic–oxic conditions in shallow marine environment during Pennsylvanian–Early Permian time. The black mudstones contain total organic carbon which ranges from 0.1 to 0.7 wt.%, and gold content varying from 40 to 62 ppb, making them gold source rocks. This study has revealed diagenetic gold presence in the early pyrite generations (pyrites 1, 2, and 3) in these mudstones with gold content ranging up to 1.6 ppm Au which is indicative of early enrichment of gold. Conversely, late generations of pyrite (pyrites 4, 5, and 6) in these mudstones record low gold content up to 0.5 ppm Au. The δ34S values for pyrite grains range from −24.6‰ to +6.2‰ likely indicate a combination of magmatic and biogenic source of sulfur. Organic carbon isotope composition of the pebbly mudstone samples shows a wide range from −23.9‰ to −5.8‰ indicating a mixed terrestrial and marine source.

(Invited) Compact Model for Short-Channel Organic Thin-Film Transistors with Extension for Non-Quasistatic Circuit Simulation and Variability Analysis

We present a compact model for organic thin-film transistors (TFTs) that covers both below-threshold and above-threshold operation with a single charge-based current expression [1]. The effect of hopping transport is included by a power-law mobility model. Contact resistances for staggered and coplanar device structures (Fig. 1) are considered, which can be nonlinear in the case of work-function mismatch between contacts and organic semiconductor [2]. Short-channel effects in submicron transistors, such as threshold-voltage roll-off and drain-induced barrier lowering (DIBL), are included [3].From the expression for the accumulated channel charge, a closed-form model for the drain-current variability due to carrier-number and correlated mobility fluctuations has been derived, relating these statistical variations to the trap density in the channel [4].Furthermore, by applying a partitioning scheme, charges are explicitly attributed to the source and drain contacts, allowing the derivation of a charge-based capacitance model valid for quasi-static operation [5]. Charges in the gate-to-contact overlap regions have been included.Utilizing this device model in a transmission-line approach, a circuit simulation including non-quasistatic effects is possible [6]. In the circuit-simulation netlist, the TFT is replaced by a macro model consisting of a finite number of n single transistors, whereby each single transistor represents a section of the intrinsic channel capacitance and a segment of the intrinsic channel resistance. This model is able to capture the charging and discharging of the channel capacitance of each segment through the channel resistance of the adjacent transistors. In this way, the frequency dependence of the node-to-node capacitances of the full device is obtained.The compact model has been implemented in the hardware description language Verilog-A and verified using results of measurements performed on organic p-channel TFTs fabricated on flexible polyethylene naphthalate (PEN) substrates by stencil lithography (Figs. 2, 3). The TFTs consist of 25-nm-thick aluminum gate electrodes, a 5.3-nm-thick hybrid AlOx/SAM gate dielectric, 30-nm-thick gold (Au) source and drain contacts coated with a pentafluorobenzenethiol (PFBT) monolayer, and a 25-nm-thick vacuum-deposited layer of the small-molecule organic semiconductor DPh-DNTT [7,8]. The transmission-line approach has been verified with good accuracy by comparison with frequency-dependent admittance measurements and numerical simulations of the transient switching behavior of organic TFTs. For a transient analysis, the optimum number of segments required to achieve good agreement between the results from the model and those from TCAD simulations is approximately n=6.In conclusion, the model presented here is fully capable of providing accurate results in dc, small-signal ac, and transient circuit simulations, including short-channel effects. Furthermore, the same set of equations allows an estimation of the drain-current variability due to charge trapping. Acknowledgements: This project was funded by the German Federal Ministry of Education and Research ("SOMOFLEX", No. 13FH015IX6), German Research Foundation (DFG) under Grant KL 1042/9-2 (SPP FFlexCom), and EU H2020 RISE ("DOMINO", No. 645760). We acknowledge AdMOS GmbH, Germany for support.

Characterization of heavy mineral concentrates and detrital gold particles from the Bigorne granite-hosted gold deposit in the Iberian Variscan Belt

Abstract The Bigorne gold deposit, located in the Iberian Variscan belt, is a gold-bearing vein system, which cross-cuts Variscan granites. The hypogene mineralization corresponds to sheet-veins parallel to the late-Variscan Penacova–Régua–Verín fault. A combined study was undertaken of gold particles from hypogene mineralization and locally derived eluvial material, as well as gold from alluvial deposits in local drainages, to assess possible sources of the alluvial gold. The geochemistry and mineralogy of heavy mineral concentrates revealed a similar signature to the hosted granites and hypogene mineralization, which indicates a local source for the surficial materials, with limited contribution from surrounding rocks. Hypogene and detrital gold particles at Bigorne area are entirely primary in origin and correspond essentially to a Au–Ag alloy (<22 wt% Ag), locally with minor amounts of Cu. The compositional range of Ag and Cu is a consequence of variation in parameters formation of the deposit, such as temperature. Our study highlights the first results on gold detrital particles chemistry for granite-hosted gold deposits in the Iberian Variscan belt, and has provided a platform for further work to characterize gold from this environment, such that it may be used as a generic indicator mineral together with other resistant ore minerals.

Polyphase gold mineralization at the Yaou deposit, French Guiana

Abstract The Yaou deposit, located in French Guiana within the Guiana Shield, is one of the most promising gold deposits of the regional Paleoproterozoic greenstone belt. It displays numerous quartz monzodiorite bodies aligned along a sinistral shear zone where a five-deformation phases model is established at the camp scale. The ductile D 1/2YA phase is responsible for the main penetrative foliation while the D 3YA phase is related to shearing. An intrusive event is identified as being pre to syn-D 3YA . The following phase D 4YA represents a brittle quartz-carbonate veining set hosted preferentially within intrusive bodies and along the shear zone. A local D 5YA brecciation event crosscuts the D 4YA veins. Among this deformation history, two auriferous events (D 3YA and D 4YA ) control the overall grade of the Yaou gold deposit. More specifically, most of the Au grade is associated with the main economic D 4YA veining event, where the gold is visible and linked to Py 4 within an ankerite/hematite rich alteration halo. At the microscopic scale, results of in situ analyses using LA-ICP-MS on pyrite show that metasediment-hosted Py 0 is a primary source of submicroscopic gold having a low contribution to the total endowment. Py 3 shows some gold content due to possible remobilization of Au D0YA . Gold in Py 4 is found as submicroscopic gold, as micro-inclusions and as infilling fractures in association with elements such as Te, Ag and Bi. Most contribution to the Au grade is from micro-inclusions and, to a lesser extent, from free and submicroscopic gold. The ore shoot locations are lithologically controlled for Au D0YA (metasedimentary unit-hosted), structurally controlled (shear zone-hosted) for Au D3YA and rheologically controlled for the Au D4YA (intrusion-hosted). The deposit is clearly polyphase both at the macroscopic and the microscopic scales, invisible gold is associated with As whereas visible gold is observed as inclusions in pyrite with high contents of Ag, Te and Bi. We define an early low-grade enrichment of Au D0YA to Au D3YA followed by a later high-grade event, Au D4YA supporting polyphase mineralization processes. This study confirms that orogenic gold deposits can be formed by remobilization and/or new gold inputs during multiple deformation, veining and hydrothermal events.

A metasedimentary source of gold in Archean orogenic gold deposits

AbstractThe sources of metals enriched in Archean orogenic gold deposits have long been debated. Metasedimentary rocks, which are generally accepted as the main metal source in Phanerozoic deposits, are less abundant in Archean greenstone belts and commonly discounted as a viable metal source for Archean deposits. We report ultralow-detection-limit gold and trace-element concentrations from a suite of metamorphosed sedimentary rocks from the Abitibi belt and Pontiac subprovince, Superior Province, Canada. Systematic decreases in the Au content with increasing metamorphic grade indicate that Au was mobilized during prograde metamorphism. Mass balance calculations show that over 10 t of Au, 30,000 t of As, and 600 t of Sb were mobilized from 1 km3 of Pontiac subprovince sedimentary rock metamorphosed to the sillimanite metamorphic zone. The total gold resource in orogenic gold deposits in the southern Abitibi belt (7500 t Au) is only 3% of the Au mobilized from the estimated total volume of high-metamorphic-grade Pontiac sedimentary rock in the region (25,000 km3), indicating that sedimentary rocks are a major contributor of metals to the orogenic gold deposits in the southern Abitibi belt.

Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

Crustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.

Petrographic, geochemical and structural characteristics of gold-bearing metasedimentary rocks from the Atacora structural unit, Northwestern Bénin Republic

The metasedimentary rocks of the Atacora structural unit around Natitingou in Benin are composed of quartzites, quartz muscovite schist and mica schist. Being auriferous, the petrographic, geochemical and structural features of these rocks were investigated to ascertain the source of gold and its relation to structural deformations. Quartz, muscovite and opaque minerals constitute the dominant minerals in the quartz muscovite schist. The quartzites and mica schists are predominantly composed of quartz, plagioclase, microcline, muscovite and chlorite in varying proportions, with biotite, garnet and epidote in mica schist. The rocks have quartzose sedimentary composition and plot within the passive margin setting on major element discrimination diagrams. The Pan-African ductile and brittle deformation phases produced predominantly folds, strike-slip faults, dextral shear plane and fractures within the area. Gold-bearing veins in the host rocks occur within and near the N-S to NE-SW trending microfolds and the major brittle E-W and NE-SW faults. Gold mineralization is hosted within the NE-trending shear zones and NE-SW trending asymmetric folds which are attributed to transpressional D2 phase of the Pan-African orogeny. Pathfinder elements for gold mineralization in the Atacora are W–Cu–As–Mo ± Sn. This may suggest interaction between host rocks and mineralizing fluids, probably from deformation and metamorphic processes during the late stages of the Pan-African Orogenic event. However, fluid inclusion and stable isotopic studies are required to constrain the origin of ore fluids.

Fluid volatile composition associated with orogenic gold mineralization, Otago Schist, New Zealand: Implications of H2 and C2H6 for fluid evolution and gold source

We provide the first large-scale investigation of gold mineralizing fluids from 19 gold deposits distributed in the Mesozoic Otago Schist belt endowed with approximately 580 tonnes of gold (past production and resources). Fluid inclusions from gold-bearing veins were petrographically studied and analysed by solid-probe mass spectrometry for H2O, CO2, N2, C2H6, He, Ar, CH4, SO2, H2S, and H2. Fluid inclusion assemblages are quite similar for all studied gold deposits, a particular feature for orogenic gold districts. Gold-bearing fluids are dominantly aqueous (H2O > 82.13 mol %) with very low contents of CO2 (<12.93 mol) in comparison with other orogenic gold deposits worldwide, with H2 (up to ~8 mol %) and C2H6 (up to ~0.5 mol %). Fluid composition is exceptionally homogeneous at the belt-scale. It is proposed that the relatively low content of CO2 and high content of H2 is related to chemical reactions in the fluids inducing graphite precipitation in the host rocks and mineralized structures and consumption of CO2 and CH4. The unique homogenous composition of fluids through time and space for the Otago Schist is related to the combination of: 1) the relatively homogeneous sedimentary rock source for fluid generation by metamorphic dehydration; 2) large-scale chemical reactions for consuming carbon-bearing volatiles; and 3) lack of external source (meteoric or magmatic) for fluid mixing. The presence of C2H6 is interpreted to be an indication that gold was sourced from primary gold-bearing pyrite hosted in carbon-rich turbidites, which is also the source for fluid generation and its hydrocarbon components.

Intrusion-Associated Gold Systems and Multistage Metallogenic Processes in the Neoarchean Abitibi Greenstone Belt

In gold-endowed greenstone belts, ore bodies generally correspond to orogenic gold systems (OGS) formed during the main deformation stage that led to craton stabilization (syntectonic period). Most OGS deposits postdate and locally overprint magmatic-hydrothermal systems, such as Au-Cu porphyry that mostly formed during the main magmatic stage (synvolcanic period) and polymetallic intrusion-related gold systems (IRGS) of the syntectonic period. Porphyries are associated with tonalite-dominated and sanukitoid plutons, whereas most IRGS are related to alkaline magmatism. As reviewed here, most intrusion-associated mineralization in the Abitibi greenstone belt is the result of complex and local multistage metallogenic processes. A new classification is proposed that includes (1) OGS and OGS-like deposits dominated by metamorphic and magmatic fluids, respectively; (2) porphyry and IRGS that may contain gold remobilized during subsequent deformation episodes; (3) porphyry and IRGS that are overprinted by OGS. Both OGS and OGS-like deposits are associated with crustal-scale faults and display similar gold-deposition mechanisms. The main difference is that magmatic fluid input may increase the oxidation state and CO2 content of the mineralizing fluid for OGS-like deposits, while OGS are characterized by the circulation of reduced metamorphic fluids. For porphyry and IRGS, mineralizing fluids and metals have a magmatic origin. Porphyries are defined as base metal and gold-bearing deposits associated with large-volume intrusions, while IRGS are gold deposits that may display a polymetallic signature and that can be associated with small-volume syntectonic intrusions. Some porphyry, such as the Côté Gold deposit, demonstrate that magmatic systems can generate economically significant gold mineralization. In addition, many deposits display evidence of multistage processes and correspond to gold-bearing or gold-barren magmatic-hydrothermal systems overprinted by OGS or by gold-barren metamorphic fluids. In most cases, the source of gold remains debated. Whether magmatic activity was essential or marginal for fertilizing the upper crust during the Neoarchean remains a major topic for future research, and petrogenetic investigations may be paramount for distinguishing gold-endowed from barren greenstone belts.

Laser ablation ICP–MS trace element composition of native gold from the Abitibi greenstone belt, Timmins, Ontario

Trace elements in native gold provide a “fingerprint” that tends to be unique to individual gold deposits. Fingerprinting can distinguish gold sources and potentially yield insights into geochemical processes operating during gold deposit formation. Native gold grains come from three historical gold ore deposits: Hollinger, McIntyre (quartz-veined ore), and Aunor near Timmins, Ontario, at the western end of the Porcupine gold camp and the southwestern part of the Abitibi greenstone belt. Laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) trace element concentrations were determined on 20–25 µm wide, 300 µm long rastor trails in ∼60 native gold grains. Analyses used Ag as an internal standard with Ag and Au determined by a scanning electron microscope with an energy dispersive spectrometer. The London Bullion Market AuRM2 reference material served as the external standard for 21 trace element analytes (Al, As, Bi, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Pd, Pt, Rh, Sb, Se, Si, Sn, Te, Ti, Zn; Se generally below detection in samples). Trace elements in native gold associate according to Goldschmidt’s classification of elements strongly suggesting that element behaviour in native Au is not random. Such element behaviour suggests that samples from each Timmins deposit formed under similar but slightly variable geochemical conditions. Chalcophile and siderophile elements provide the most compelling fingerprints of the three ore deposits and appear to be mostly in solid solution in Au. Lithophile elements are not very useful for distinguishing these deposits and element concentrations may be controlled by microinclusions such as tourmaline. The deposits show low Ag contents, which is consistent with mesothermal Au. Hollinger and McIntyre deposits have similar trace element abundances with higher Ag, Pb, Bi, Sb, and Pd and generally low Cu; however, Cu concentrations in McIntyre are higher than in Hollinger. In contrast, Aunor shows comparatively low Ag, Bi, Sb, Pb, and Pd and higher Au/Ag consistent with higher hydrothermal fluid temperatures. Gold grain signatures reflect the chemical characteristics of the host rock superimposed on a chemical signature inherited from the mineralizing fluid. The association of Pb–Bi–Cu bearing phases such as galena and chalcopyrite with gold apparently enriched in these elements supports precipitation from hydrothermal fluids carrying the elements.

Technoeconomic Assessment of Organic Halide Based Gold Recovery from Waste Electronic and Electrical Equipment

Waste Electronic and Electrical Equipment (WEEE) is one of the fastest growing waste streams worldwide, with significant economic value due to the precious metals contained within. Currently, only a small share of the total globally produced quantity produced is treated effectively and a large amount of valuable non-renewable resources are being wasted. Moreover, the methods currently applied in industry on a large scale are not always environmentally friendly. Thus, an economically viable and environmentally friendly method that would achieve high recovery of certain elements is sought. The objective of this paper is to assess four different organic halides as leaching agents for gold recovery from WEEE. Two of them have been previously tested (namely N-bromosuccinimide, NBS, and N-chlorosuccinimide, NCS) and have shown promising results, whereas the other two are novel and were selected due to their lower toxicity levels (trichloroisocyanuric acid, TCICA, and tribromoisocyanuric acid, TBICA). Both commercially supplied pure gold powder and WEEE dust from a recycling company were used as the gold source. Results show that from a technical standpoint, the NBS is a superior solution with both substrates, reaching 61% and 99% extraction efficiency from WEEE dust and pure gold, respectively. The other three methods recorded lower recovery efficiency (with the highest value reaching 36% for NCS, 53% for TCICA and 29% for TBICA). However, taking into account the price of gold and the expenses of the extraction process, only three of the lixiviants tested (NBS, NCS and TCICA) could be potentially profitable and viable on a larger scale.

Mantle-derived gold scavenged by bismuth-(tellurium)-rich melts: Evidence from the mesozoic wulong gold deposit in the north china craton

Mesozoic gold deposits associated with large-scale cratonic destruction of the North China Craton (NCC) made up a giant gold province that is unique among ancient cratons worldwide. The Au sources of these deposits are highly debated among Archean to Proterozoic strata, Mesozoic granitoid plutons, subducting slab-derived fluids, and mantle-derived fluids. Here we chose the Wulong gold deposit, a typical lode gold deposit in the NCC, to constrain the sources of gold and sulfur. Sulfides from auriferous quartz veins in the Wulong gold deposit have restricted Δ33S (−0.1 to +0.2‰), without diagnostic signature of Archean sedimentary sulfur. Their mantle-like δ34S (−0.9 to +3.3‰) and restricted Pb isotopic ratios are remarkably different from those of sulfides from Paleoproterozoic strata and Mesozoic granitoid plutons. Sulfides from the Mesozoic doleritic dykes in the Wulong district have nearly identical δ34S (+1.7 to +2.0‰) to that of auriferous quartz veins, indicating that they were derived from similar mantle sources. We interpret that the sulfur and gold of the Wulong gold deposit were likely sourced from mantle-derived fluids released from devolatilization of the hydrated, subcontinental lithospheric mantle (SCLM). However, the enrichment of Au is not directly linked to an anomalously Au-rich source in the SCLM beneath the NCC which contains 0.39 ppb Au on average. Neither Mesozoic igneous rocks (0.22 ppb Au on average) nor Paleoproterozoic strata (0.19 ppb Au on average) in the Wulong district are enriched in Au. In addition, sulfides from auriferous quartz veins are not enriched in Au (commonly < 1 ppm Au), indicating that the mantle-derived fluids are likely Au-undersaturated during the deposition of sulfides. On the other hand, positive correlation of Au and Bi of auriferous quartz veins and close association of native gold with native bismuth and Bi-Te-S minerals consistently indicate that Au enrichment is likely related to Bi-(Te)-rich melts. The Bi-(Te)-rich melts may have precipitated from the Au-undersaturated auriferous fluids and scavenged Au from the fluids, leading to the Au enrichment. The insignificant fractionation of δ34S among sulfides and typical reduced assemblage of native bismuth, joséite and pyrrhotite in auriferous quartz veins consistently indicate that the occurrence of Bi-(Te)-rich melts is related to the reduction of fluids. This study demonstrates that Au in the mantle-derived fluids can be scavenged and significantly enriched by Bi-(Te)-rich melts, even if the fluids were Au-undersaturated, leading to the formation of giant lode gold deposits.

Zircon U--Pb ages of Au-bearing host rocks in Northwest Iran as evidence for gold mineralization in the Carboniferous, not Cenozoic time!

A few gold deposits occur in northwest Iran which are hosted by mylonitic granitoids and phyllonite. New U--Pb ages yield ages of 350–311 Ma for the mylonitic granitoid and 354–348 Ma for the phyllonite, which indicate Carboniferous magmatic activity in northwest Iran. The host granitoid and phyllonite have high contents of Zr (212, 246 ppm) and Y (26.8, 38.7 ppm). High 10,000 × Ga/Al ratios (2.1–5.1) and fractionation of the rare earth elements (REEs) pattern with depletion of Eu, Sr, and P may infer an A-type (anorogenic) granite affinity for the host rocks. Correspondingly, these rocks are characterized by high contents of Nb (33.1 to 39.2 ppm), Ta (1.68 to 2.40 ppm), Tb (0.84 to 1.17 ppm), and Th/Yb ratios with some similarity to OIB-like rocks. Whole rock compositions of these host rocks are consistent with both A1 and A2 type granites, which infer magmatic activity in an extensional tectonic regime. Perhaps the extension may have occurred during rifting of Neo-Tethys in northern Gondwana. Upwelling of the hot OIB-like melts during the opening of Neo-Tethys ocean was the main mechanism of this extension. The OIB signatures of the A-type granitoids controlled the gold mineralization during this process. Accordingly, we classify the gold mineralization in NW Iran as intrusion-related gold deposits. These mantle-derived magmas from the asthenosphere may support a source of both sulfur and gold. These elements were concentrated in hydrothermal fluids in the late stages of magma crystallization. Also, hot magma injection increased the geothermal gradient and caused extensive dehydration of the sedimentary rocks inin the roof of the magma chamber. Circulation of these hot fluids with injection into the hot crystallizing magmatic rocks and mixing with late-stage magmatic-hydrothermal fluids and meteoric water (?) seem to all have essential roles for transporting the gold and precipitating it within fractures in the semi-brittle to brittle zone. The gold precipitated as native or nanoparticles in pyrite in the inner part of the shear zone. This research reveals that mineralization occurred in the Late Paleozoic in an extensional tectonic regime and not above the subduction zone or collision zone which had been suggested before.

القبائل النوبیة خلال عصر الدولة القدیمة

تنوعت علاقات مصر مع القبائل النوبية خلال عصر الدولة القديمة نتيجة تنوع أغراض مصر من تلک القبائل وديارها، منها ما کان ذو طابع سياسية وحربي بحت مثل اهتمام ملوک الأسرة السادسة بالنوبة بسبب الضغط الذي وقع على الحدود المصرية من قبل البدو الأسيويين، وتعدي هذا الاهتمام من مجرد إرسال الحملات إلى استخدام الجنود النوبيون کمرتزقة في الجيش المصري، ومنها ما کان ذو طابع إقتصادي حيث کانت بلاد النوبة هي البلاد المصدرة للذهب والعاج والعديد من الخيرات التي کان الملک وحاشيته يتهافتون للحصول عليها بالإضافة إلي کونها معبر للتجارة المصرية إلي قلب أفريقيا. ونتيجة لذلک عمل الملوک المصريون على السيطرة على بلاد النوبة بيد من حديد في الوقت الذي کان يسکن بها القبائل المعروفة بأسم المجموعة (أ) ثم وفد عليهم قبائل عرفت بقبائل المجموعة (ج) مع نهاية عصر الدولة القديمة، تعني هذه الدراسة بذکر أثر القبائل النوبية على مصر خلال عصر الدولة القديمة من خلال المصادر المصرية والنوبية المعاصرة وتشمل أيضا على التعريف بأهم القبائل النوبية التي ظهرت في المصادر المصرية وما خلفته تلک القبائل من آثار تعطينا فکرة عن الجوانب المختلفة لحياتها. The Relations between Egypt and Nubian tribes diversed during old kingdom period, As a result of the diversed Egyptian needs from the Nubian tribes and their lands. Some of these relations were political and martial such as the sixth dynasty special care of Nubia because of the Asiatic Bedouin danger in their times, So Egyptian kings recruited the Nubian warriors as soldiers in the Egyptian army beside the military campaigns which they led on their lands. On the other hand we can consider the economic motive as a strong motive for the Egyptian king, As Nubia was a source of gold, ivory and other goods for the king and his courtyards, in addition to this Nubia was a passage for the Egyptian trade, which goes to center Africa. All of these motives make us believe that Egyptian domination over Nubia was very harsh when it was inhabited by the tribes known as group (A) tribes then a new tribes came in the latest days of the old kingdom period whom we know as group (C) tribes, in this research I will talk about the Nubian tribes effect on Egypt through the Egyptian and contemporarily Nubian resources, and I will talk about the Nubian tribes from the ancient Egyptian texts and Nubian monuments which give as an idea about How these Nubian tribes lived their life.

Mineralogical features of gold of the Permian conglomerates of the Sololiy uplift of the Olenek high (Northeastern Siberian platform)

Typomorphic features of placer gold of conglomerates of the Ortokinskaya formation of the Early Permian age (P1or) of the Sololiy Uplift of the Olenek High and modern channel alluvium of the Ortoku Eekit river, which drains these deposits, are studied. It is found that extremely heterogeneous composition and complex inner structure are typical features of the vast majority of gold of the Permian conglomerates. There are several stages of different fineness (from 251‰ to 999‰) within a single gold particle, as a result, gold has a mosaic-block inner structure. It is proposed that such heterogeneity is formed due to epigenetic transformations of primary medium-grade gold in an intermediate reservoir of the Permian age, and also under influence of superposed hydrothermal mineralization with low-grade gold, related to the processes of the Mesozoic tectonomagmatic activation. The latter is indicated by the discovery of impregnated gold-sulfide mineralization in the Permian conglomerates. Ore mineralization is represented by gold, silver, pyrite, sphalerite, chalcopyrite, galena, argentite, native tin, and barite. Association mineralization to thin tectonic zones of conglomerate fragmentation, suggests that superposed gold-sulfide hydrothermal mineralization of impregnated type was formed as a result of manifestations of the Mesozoic tectonomagmatic activation, when gold-bearing hydrothermal solutions migrated in faults. It is determined that auriferous conglomerates of the Ortokinskaya formation of the Permian age were major sources of placer gold of modern alluvium in the studied part of the Ortoku Eekit.

Magnetic Sources of Gold and Freshwater Rivers: Using Ultra-Strong Magnets in the Production of Freshwater and Gold Fishing from Salty and Freshwater Currents

Magnetic Sources of Gold and Freshwater Rivers: Using Ultra-Strong Magnets in the Production of Freshwater and Gold Fishing from Salty and Freshwater Currents

Regularities of ore gold placement in central kyzylkumakh (South Tyan-shan)

The article discusses the patterns of distribution of gold mineralization in the Central Kyzylkum desert of the Southern Tien Shan. As a result of applying the methods of statistical metallogenic analysis, quantitative characteristics of the localization of gold-bearing objects were obtained, explaining some of the features of their formation in connection with the stages of the geological development of the region. It was found that the formation of the gold source and the gold deposits of the Central Kyzyl Kum itself involved all stages, from the stage of formation of the oceanic crust in the spreading zones to the stage of collision and associated metamorphism.