High-grade Gold Research Articles

Clinical significance of HIF-1α, ET-1, and NO as biomarkers in chronic obstructive pulmonary disease patients with pulmonary hypertension.

Pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD), with repeated infections and airflow limitation leading to endothelial dysfunction. The objective of this study was to retrospectively investigate the clinical significance of serum hypoxia-inducible factor 1-alpha (HIF-1α), plasma endothelin-1 (ET-1), and nitric oxide (NO) as non-invasive blood biomarkers for diagnosing patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). A total of 230 AECOPD patients were assessed for serum HIF-1α, plasma ET-1, and NO levels using Doppler echocardiography and blood tests. Clinical characteristics, including age, COPD duration, and comorbidities, were compared between patients with and without PH. The diagnostic value was determined through ROC analysis. Pearson correlation and multivariate logistic analyses explored the correlation of biomarkers in AECOPD with PH. Serum HIF-1α, plasma ET-1, and NO levels showed significant differences between COPD patients with and without PH. The combination model (0.027 * HIF-1α + 0.028 * ET-1 - 0.049 * NO) demonstrated an AUC of 0.89, indicating superior diagnostic value compared to individual biomarkers. Multivariate logistic analysis identified smoking, higher GOLD grade, hypertension, and elevated levels of HIF-1α, ET-1, and NO as independent risk factors for AECOPD. Positive correlations were observed between serum HIF-1α and plasma ET-1 levels with pulmonary artery systolic pressure (PASP), while NO demonstrated a negative correlation. Serum HIF-1α, plasma ET-1, and NO were associated with AECOPD and PH, and detecting individual or combined levels of these biomarkers in the blood can predict COPD-related PH.

Polyphased gold enrichment as a key process for high-grade gold formation: Insights from the 10 Moz Jundee-Bogada camp (Yilgarn Craton, Western Australia)

High-grade (> 10 g/t) gold mineralization in orogenic gold deposits is of significant economic importance. Understanding the formation of such enriched ore zones is critical for gold exploration success. The world-class Jundee-Bogada gold camp in the Yilgarn Craton of Western Australia comprises both high-grade (avg. > 10 g/t, Jundee deposit) and low-grade (avg. < 3 g/t, Bogada prospect) lodes, despite shared host stratigraphy. The paragenetic framework established for the Jundee gold deposit suggests that the overall gold endowment developed over three deformation events. An early episode of low-grade gold mineralization is associated with colloform-crustiform veins that formed during extensional deformation (DJB2A). A switch to transtensional deformation (DJB2B) resulted in brecciation of the colloform-crustiform veins and coeval deposition of native gold. Late reverse faults record evidence for a third mineralization stage resulting from a NE-SW-directed shortening (DJB3). Mineralization during this late stage was dominantly low-grade, with local occurrences of ultra-high-grade ore zones (> 100 g/t). Each event records transient changes in fluid chemistry during continued hydrothermal activity that spanned local deformation histories. We argue that at the Jundee gold deposit, protracted gold enrichment during three polyphased mineralization episodes resulted in the formation of high-grade gold ores. Whereas the complete metallogenic history is recorded at the Jundee deposit, gold within the Bogada prospect was introduced solely during the late contractional stage (DJB3), resulting in a bulk low-grade endowment. We hypothesize that gold enrichment in high-grade orogenic gold deposits is a direct consequence of the spatial superimposition of protracted ore-forming events.

Release and re-enrichment of invisible gold in arsenian pyrite promoted by coupled dissolution-reprecipitation reactions

The mechanisms responsible for invisible gold enrichment driven by coupled dissolution-reprecipitation reaction (CDR) are debated. Here we report the micro- to nano-scale textures of arsenian pyrite in a high-grade (>10 g/t) gold ore from the Chang’an deposit to trace the gold enrichment process. Our study records a CDR-driven evolution of mineral growth from an As-rich, Au-poor pyrite core, with numerous fine arsenopyrite inclusions, to an inclusion-free, As-Au-rich oscillatory pyrite rim. The reaction occurred at ~260 °C under 4.7 to 5.8 pH and –36.6 to –32.9 logfO2 conditions. The elevated As but depleted S contents in the pyrite core indicate a combined elevation of S fugacity and solubility of Au. The coprecipitation of arsenopyrite inclusions in the core caused a depletion of S fugacity to –13.8 ~ –11.7, triggering Au enrichment in the rim. This non-unique process has the potential to explain the upgrade of invisible Au in arsenian sulfides, worldwide.

Gold source and deposition in the Sanakham gold deposit, SW Laos: Constrains from textures, trace element geochemistry and in-situ sulfur isotopes of pyrite

The Luang Prabang (Laos) – Loei (Thailand) metallogenetic belt is endowed with major porphyry-skarn, and epithermal gold deposits. The Sanakham gold deposit is a newly discovered hydrothermal vein-type orogenic gold deposits (10.6 t Au @ 3.05 g/t) in the belt, and consist of a series of quartz-sulfide veins that are controlled by secondary structures of the regional NNE-trending brittle-ductile shear zone. Its mineralization can be divided into four stages: (I) quartz–pyrite–arsenopyrite, (II) quartz–pyrite–pyrrhotite–chalcopyrite, (III) quartz–pyrite–base-metal sulfide, and (IV) quartz–carbonate. Three pyrite generations were identified: py1 (stage I) as disseminated euhedral to subhedral coarse grains; py2 (stage II) as subhedral to anhedral fine grains occur around the cataclastic and corrosion textures in py1; py3 (stage III) as subhedral to anhedral fine grains occurred in sulfide veins or veinlets that overprint the existing quartz-sulfides. All three generations of pyrite have low trace-element contents including very low lattice-bound gold (py1: 0.040 ppm; py2: 0.098 ppm; py3: 0.028 ppm) and arsenic (py1: 227 ppm; py2: 133 ppm; py3: 13.3 ppm) contents. Visible gold grains are sited in textures of pyrite grains that relate to brittle cataclastic deformation. Considering the relatively low contents of pyrite in the ores of Sanakham, it is impossible to derive the high-gold grade orebodies through local remobilization of originally lattice-bound gold in pyrite. The py2 might be formed during hydrothermal overprinting and dissolution of py1 led by continuous supply of ore fluids with relatively higher contents of Au, Ag, Cu, Sb, Te, Pb, and Bi. A reduction reaction related to reduced carbon species in wallrock is an assignable cause for gold deposition, even though the fluid-rock interaction and fluid immiscibility processes might be important. The Au- and As-poor pyrites have similar δ34S values (py1: –2.58 to –0.83 ‰; py2: –2.17 ‰ to + 0.25 ‰; py3: –1.24 to –0.60 ‰ ppm) that close to 0 ‰, indicating the sulfur may have been originated from magmatic or mantle sources. Therefore, we propose that the Sankham gold deposit is a member of the orogenic deposit class, but notably characterized by the low concentrations of invisible gold in the relatively As-poor pyrite lattice.

San Albino, Nicaragua: A Low-Angle, Thrust-Controlled Orogenic Gold Deposit

Abstract The San Albino deposit is an orogenic gold occurrence hosted by a low-angle thrust that is the site of a new open-pit mine in northern Nicaragua. The deposit is hosted in greenschist facies rocks of the Jurassic metasedimentary Neuvo Segovia Formation. The schist was uplifted and exposed during arc accretion and Cretaceous thin-skin deformation, forming the NE-striking Colon fold-and-thrust belt. Deformation included emplacement of the 119 to 113 Ma NE-trending Dipilto batholith into the regionally metamorphosed clastic rocks about 5 km northwest of the San Albino deposit. Mineralization is dominated by three laminated quartz vein systems (i.e., San Albino, Naranjo, Arras) that broadly follow shallowly dipping (approx. 30°) carbonaceous shears roughly concordant to schistosity along the limbs of a doubly plunging antiform. The three main parallel shears are each separated by about 90 m and individually reach a maximum thickness of about 8 m. Maximum thickness of ore zones is where post-ore local folding and reverse motion along the shallow shears has duplicated the laminated low-angle gold-bearing veins (D2 and early D3). Additional gold was added to the veins, with abundant sulfides, during a subsequent brecciation event of the early formed quartz veins that accompanied progressive thrusting (late D3). This predated boudinage of the veins during continued compression and thrust loading (D4); high gold grades are particularly notable along pyrite- and arsenopyrite-bearing stylolites formed during D4 pressure solution. The D2 to D3 gold event is likely coeval with Albian uplift of the Dipilto batholith and with back thrusting in the schist aided by the stress inhomogeneities provided by the igneous complex. Low-angle thrust-controlled orogenic gold deposits may represent world-class exploration targets because of their large linear footprints, although they are traditionally looked at as less favorable exploration targets relative to gold systems developed more commonly along high-angle reverse faults. Our case study of the San Albino deposit shows that although low-angle deposits are not inherently misoriented for failure like the more common subvertical reverse fault-related deposits, they may be sites of significant pressure buildup due to hydrothermal mineral precipitation during initial water-rock interaction or slight temperature decreases along the low-angle flow path. Resulting fluid cycling may lead to thick laminated vein development, such as seen at San Albino, where especially high-grade zones may be associated with local steepening and/or dilational zones within the broader, low-angle vein-hosting shear system.

Effect of Power and Exposure Time on the Microwave-Assisted Roasting of Refractory Gold Ore

Reserves of high-grade gold ore worldwide are decreasing, and some industries have started processing refractory gold ore. Refractory gold ore contains sulfide minerals such as pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS), and sphalerite (ZnS). Gold in refractory ores occurs as fine-size gold-bearing sulfide minerals. In this study, the microwave-assisted roasting method has been investigated as a pretreatment for a refractory gold ore. This method can provide rapid heating radiation, cause micro-cracks, and trigger the decomposition of sulfide minerals. The presence of additive helps in the oxidation of sulfide minerals. The microwave-assisted roasting was carried out using variations in microwave power and time. Microwave power between 300 - 600 watts significantly affected the increase in roasting temperature and weight loss of refractory gold ore. The highest temperature reached 567°C in roasting at 800 watts for 30 minutes. The optimum condition for microwave roasting was achieved at 400 watts of power with a roasting time of 30 minutes. Metals extraction of Cu, Zn, Pb, and Fe reached 97.2%, 82.7%, 16.1%, and 2.1% in water leaching.

Mineralogy and Geochemistry of the Mupane and Shashe Gold Deposits of the Tati Greenstone Belt (NE Botswana): Implications for Mineral Deposit Models and Exploration

Abstract The Archean Tati greenstone belt is located at the southwestern margin of the Zimbabwe craton (northeast Botswana) and hosts numerous Cu-Ni ± platinum group element (PGE) and Au ± Ag occurrences and deposits. Gold occurrences/deposits are poorly studied, and key questions pertaining to their genesis remain unclear, including the mode of occurrence(s) of gold, the relative timing of gold introduction with respect to the evolution of the greenstone belt, the number of gold mineralization events, the alteration patterns, and the relationships between each alteration pattern and gold mineralization. A detailed study that includes sulfide and gold grain chemistry using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and electron probe microanalysis (EPMA), respectively, and X-ray diffraction (XRD) of mineralized rock samples of three Tati greenstone belt gold deposits was carried out to constrain the genesis of gold mineralization and formulate exploration guidelines in the Tati greenstone belt. Gold in the Tati greenstone belt is the result of multiple events, is mainly associated with arsenopyrite, pyrite, and sphalerite, and occurs as (1) microinclusions within sulfides, (2) intergrowth with sulfides, (3) minute particles (&amp;lt;2–10 µm) within the silicate matrix, (4) microfractures and microvug infills, and (5) lattice-bound and sulfide-hosted refractory gold. The first gold event (as electrum) is premetamorphic and associated with sphalerite-quartz veins. The second stage is a postmetamorphic high-grade gold event that is accompanied by extensive carbonatization and propylitization of host rocks. The third stage of gold mineralization is marked by the dissolution of gold in the early formed stages 1 to 2 and subsequent reprecipitation within cracks, fractures, and vugs. Auriferous pyrite composition suggests that Au-bearing mineralizing fluids are predominantly of magmatic origin and that their physicochemical compositions changed during the mineralization process, as supported by chemically zoned Au-bearing arsenopyrite, various alteration types containing gold, and variation in gold fineness across the several gold deposits in the Tati greenstone belt. Gold deposition in the Tati greenstone belt mainly occurred through sulfidation, as indicated by the closest spatial association between gold and Fe-bearing sulfides and ferromagnesian silicates. Gold in the Tati greenstone belt is closely correlated with As, Sb, Pb, Bi, Ni, Hg, Tl, Cd, In, Mo, W, Zn, and Te and moderately to weakly associated with Sn, Se, Cr, Co, Ge, Cd, Mn, V, Ga, and Ag. The correlation between Au and fluid mobile elements, i.e., Te, Sb, Se, As, Hg, and Bi, can be used as a vectoring tool during the exploration of gold within the Tati greenstone belt, as these elements likely form halos that are much broader than the primary footprint of gold mineralization.

МОРФОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ, ХИМИЧЕСКИЙ СОСТАВ РОССЫПНОГО ЗОЛОТА БАССЕЙНА РЕКИ КЕНГЕВЕЕМ И ПЕРВЫЕ СВЕДЕНИЯ О СОПУТСТВУЮЩЕЙ ПЛАТИНОВОМЕТАЛЛЬНОЙ МИНЕРАЛИЗАЦИИ (МАГАДАНСКАЯ ОБЛАСТЬ)

The paper presents the results of the study of typomorphic characteristics of placer gold of the tributaries of the Kengeveem River, Magadan region. Placer gold was studied by optical and scanning electron microscopy at the Institute of Volcanology and Seismology of the Far East Branch of the Russian Academy of Sciences. As a result, the first information on the morphology, internal structure and chemical composition of placer gold from the southeastern part of the Taigonos Peninsula was obtained. Three types of the gold were determined. The first type is dominant. The grains are chacterized by sub-ore morphology, with weak and medium degrees of roundness. Only Au-Ag is present in the composition of native gold, other macrocomponents were not found. The gold grade is 750–950 ‰. Some gold grains bear signs of hypergene transformation, expressed in the development of high-grade gold rims and intergrain veins. The second type of gold is represented by well-rounded lamellar extractions with a grade of 980–990 ‰. The third type is loose aggregates of secondary high-grade mustard gold. The obtained data allowed us to determine the different drift distances of native gold and to consider the low-sulfide epithermal Au-Ag mineralization and presumably far-distant gabbroids as the primary sources of gold.

Ore-Forming Fluids of Orogenic Gold Deposit In Tamilouw-Haya, Seram Island, Indonesia

The Tamilouw-Haya orogenic gold deposit is located in the southern arm of Seram Island, Indonesia, occupying Tehoru Metamorphic Complex. Gold mineralization is predominantly in the form of veins, stockwork, and breccia, although minor dissemination is slightly appeared in the rock float samples. Ore-mineral assemblages are dominated by native gold, pyrite, chalcopyrite, sphalerite, tetrahedrite-tennantite (sulfosalt), galena, pyrrhotite, marcasite, realgar, kalininite, and arsenopyrite. Covellite, hematite, goethite, and malachite appear as supergene minerals. High-grade gold ores in this area are generally found in quartz-carbonate veins with the main alteration processes involving silicification, carbonatization, and sericitic. The P-T history of the mineralization was revealed by fluid inclusions, and this study implies the depth of ore deposit and its evolution during mineralization. The primary fluid inclusions from three different types of quartz/quartz-carbonate veins in Tamilouw-Haya crystallized at the homogenization temperature (Th) of 240 °C to 340 °C, with a fluid salinity from 3.87 to 0.70 wt. % NaCl equivalent, and melting temperature (Tm) of -0.4 to -2.3 oC. The ore-forming fluids consist mainly of two-phase (VCO2+LH2O) liquid-rich aqueous inclusions, characterized by low to rich CO2, low salinity, and moderate temperature. There are three vein types as the ore-bearing fluids with precious metals and anomalous high basemetal contents. Quartz type 1- veins (V1); concordant veins, formed at a temperature of 240-307 oC with an average salinity of 1.8 wt. % NaCl equivalent. Quartz type 2- veins (V2) tend to cut the rock foliation which are formed at temperature range from 293-336 oC with the average salinity that shows a value of 2.4 wt. % NaCl equivalent. Meanwhile, type 3 quartz-carbonate veins (V3) are formed at the temperature range of 240-340 oC and the average salinity of 2.72 wt. % NaCl equivalent. These quartz-carbonate veins cut the wall-rock foliation, which is identified as the late stage and associated with ore deposition in Tamilouw-Haya. The gold deposit in Tamilouw-Haya is formed at a depth of about 5.5-9 km of paleosurface, and the pressure between 1.7-2.4 Kbar in epizonal to mesozonal zones. Keywords: Tamilouw-Haya, orogenic gold, fluid inclusion, microthermometry, ore-forming fluids

Experimenting with Dimethyl Sulfoxide to Leach Gold from a Colombian Artisanal Gold Ore

The diverse uses of gold and its crucial role in the global economy are growing, particularly during cycles of economic crises. The broad use of cyanide by conventional gold-mining companies and mercury by artisanal miners poses environmental and health concerns for local communities. This article introduces an innovative gold-leaching process using a non-toxic organic reagent, dimethyl sulfoxide (DMSO), a water-free lixiviant that extracts gold from ores/concentrates in combination with copper halides. The results of laboratory experiments using dimethyl sulfoxide and a sample of high-grade gold ore from Colombia show that 96.5% of the gold was extracted in 2 h at room temperature. The typical cyanidation process using 5 g/L of CN− at pH 10.5 on the same ore sample obtained 97% gold extraction in 24 h at ambient temperature. The gold extracted using DMSO was precipitated by adding a mild acidic solution, and the reagent can be recycled via distillation and reused in repeating cycles. The results show that DMSO can be used as a promising agent for gold leaching, offering a straightforward, cost-effective, and eco-friendly procedure with minimal chemical waste.

Respiratory Symptoms, Disease Burden, and Quality of Life in Australian Adults According to GOLD Spirometry Grades: Data from the BOLD Australia Study.

Population data on the burden of chronic obstructive pulmonary disease (COPD) are often based on patient-reported diagnoses of COPD, emphysema or chronic bronchitis, without spirometry. We aimed to investigate the relationship between health burden, quality of life and severity of airway obstruction in Australian adults aged ≥40 years. We used data from the BOLD Australia study, which included randomly selected adults aged ≥40 years from six study sites to reflect the sociodemographic and geographic diversity of the Australian population (n = 3522). Participants with post-bronchodilator airflow limitation (ratio of forced expiratory volume in 1 second FEV1 to forced vital capacity <0.7) were grouped by GOLD spirometry grades 1-4. Quality of life was assessed with Short Form 12 (SF-12) Health Survey Questionnaire. Health burden was assessed as lost time off work or social activities, and healthcare utilization. Of the study sample, 2969 participants did not have airflow limitation, 294 (8.4%) were classified as GOLD Grade 1, 212 (6.0%) as GOLD 2 and 43 (1.2%) as GOLD 3-4. Participants with higher GOLD grades had more respiratory symptoms, more comorbidities and greater burden than those with lower GOLD grades. The scores of mental and physical subscales of SF-12 were lower, indicating worse quality of life, from the no airflow limitation group to the GOLD 3-4 group (P = 0.03 and P < 0.001, respectively). Greater airflow limitation is associated with greater burden and poor quality of life. Interventions to prevent, or reduce the level of, airflow limitation will reduce the symptom burden and improve quality of life for patients.

Effect of mechanical activation on biooxidation and gold extraction of a high-grade flotation concentrate using mesophilic and moderately thermophilic microorganisms

The effect of mechanical activation and biooxidation on the gold extraction from a high-grade (168 g/t) gold sulfide concentrate was investigated using a mixed culture of iron- and sulfur-oxidizing microorganisms. The influence of mechanical activation pretreatment, the nutrient medium type (Norris and 9K), initial pH, and microbial culture type was investigated on the biooxidation ability of mixed cultures of mesophilic and moderately thermophilic microorganisms. Results showed that gold extraction from the non-activated non-biooxidized concentrate was 83.9%, while after biooxidation, it reached 98.8%. The gold recovery from the mechanically activated non-biooxidized concentrate was 77.3%, which reached 97.6% after biooxidation. Therefore, biooxidation was found to have a significant positive effect on gold extraction, but mechanical activation had a negative effect on it in both abiotic and biotic media. The characterization of solid residues was performed by SEM/EDS and chemical analyses. Jarosite and gypsum were the main precipitates formed during biooxidation, especially in 9K nutrient medium. It was found that mechanical activation reduced the efficiency of biooxidation process mainly as a result of overcoming negative effects such as weak bacteria-mineral attachment, the release of toxic species, increasing pulp viscosity, and the coating of gold grains by less soluble solids on the positive effects such as the enhancing of surface area and the disordering of the crystal structure of refractory sulfide phases.

The main stages of ore formation of the Svetloe epithermal gold deposit (Khabarovsk Region) based on the study of the mineral composition of metasomatic rocks and ores

The study of the spatiotemporal relationships of metasomatites and ores of various zones of the epithermal Au-Ag deposit Svetloe (Khabarovsk Region) using a traditional mineralogical and petrographic approach made it possible to establish several stages of ore formation confined to two paleovolcanic structures of the central type. The early stage corresponds to the moderately acidic (IS) type of mineralization, the second stage of ore formation corresponds to the acidic sulfate (HS) type.Gold mineralization associated with the early stage of ore formation is represented by two main types: Au-Ag-Te and Au-Ag. The late stage of mineralization is characterized by the predominance of redeposited high-grade gold, as well as the presence of other native elements: tellurium, selenium, sulfur, and bismuth.

Interfacial adsorption of gold nanoparticles on arsenian pyrite: New insights for the transport and deposition of gold nanoparticles

Gold nanoparticles (AuNPs) are found extensively in the near-surface Earth system. The transport, aggregation, and deposition of AuNPs have been potentially recognized as an important process and even a fundamental intermediary step both in formation of high-grade gold deposits and in the dispersion of gold into the Earth's surface environment. The interfacial adsorption between AuNPs and sulfide minerals is a long-recognized process regulating transport and deposition of gold in hydrothermal fluids, and the occurance of Au and As in pyrite are often observed in various hydrothermal Au deposits. However, the adsorption behavior of AuNPs on sulfide minerals and the fundamental chemical mechanism for the AuAs relationship remain enigmatic. In this work, we selected citrate as a surrogate for typical natural organic compounds abundantly found in lower-temperature hydrothermal systems and Earth's surface environment, and experimentally investigated the adsorption of negatively charged AuNPs on pyrite and arsenian pyrite under anaerobic conditions. We demonstrate that pyrite and nanoparticle surface properties, and solution chemistry, control the adsorption process. Negligible adsorption of AuNPs on pyrite (absent of As) was verified under all experimental conditions likely due to high electrostatic repulsion. However, we observed AuNPs adsorption on arsenian pyrite and suggest that this interaction is due to negative charge-assisted hydrogen bonds ((−)CAHBs) between hydroxyl/oxyl groups on the surface of arsenian pyrite and carboxyl groups on the citrate capping agent of AuNPs. Also, the lower negative charge density of arsenian pyrite surfaces significantly reduces electrostatic repulsion between both negatively charged AuNPs and arsenian pyrite. The solution pH, coexisting organics (citrate) concentration, and ionic strength are demonstrated to play substantial roles in the adsorption of AuNPs on arsenian pyrite. However, the solution pH appears to be an overriding factor controlling the adsorption of AuNPs which decreases with the increase of pH. With respect to citrate concentration, the adsorption rates of AuNPs onto arsenian pyrite initially decreases, but only slightly, and then increases. Increased ionic strength also promotes the adsorption of AuNPs. Our findings highlight a potentially important role of AuNPs in transport and deposition processes of gold in aqueous mediums, and provide new insights on the geochemical behavior of metal nanoparticles in the hydrothermal systems and Earth's surface environment.

Application and mechanism of a compound collector for the beneficiation of low-grade gold ore

High-efficiency beneficiation of low-grade gold ore becomes an inevitable trend with the depletion of high-grade gold ore. The work innovatively proposed a novel beneficiation process for a typical low-grade gold ore through developing compound collector and discussed the adsorption mechanism. PAX and ADD are most suitable compound collector when the ratio is 3:1 and dosage is 100 g/t. A concentrate with gold grade of 18.40 g/t and recovery of 79.72% is obtained by the novel “one-stage rougher, three-stage cleaner, and two-stage scavenger” closed-circuit process, which has the advantages of low-cost, simple-process, and high-efficiency comparing with the conventional process. The FTIR spectra analysis shows that PAX is a saturated organic compound containing branched chains and ADD is a straight-chain organic compound containing unsaturated bonds. The adsorption of PAX or ADD on the gold ore is chemisorption process and the compound collector has a strong chemisorption capacity. The novel closed-circuit flotation process using compound collector develops an excellent beneficiation effect and provides a prospective and effective approach to concentrate low-grade gold ore.

Fractal dimension used as a proxy to understand the spatial distribution for carlin-type gold deposits

The spatial distribution of ore-forming element grades typically exhibits strong nonlinear characteristics as a result of continuous geological processes. The trend of change in ore grade sequences is a crucial indicator of the degree of enrichment of an ore deposit. Therefore, quantitative evaluation of the spatial distribution of ore-forming elements holds great significance for understanding ore-forming processes as well as for ore exploration. In this work, based on the principles of fractal theory, a MATLAB-based program to calculate fractal dimensions was developed, and fractal analysis was conducted on the gold concentration values (g/t) of 25 drill holes in the Lannigou Gold Mining Area, Guizhou, China. Rescaled range analysis and the fractal correlation integral were utilized to obtain the spatial distribution of gold concentrations in the drill holes. Rescaled range analysis revealed that the Hurst exponent (HR/S) values vary in the range of 0.58–0.97, which reflected the persistent behavior of vertical variation in gold tonnage at the studied wells. Furthermore, the relationship between gold grade distribution and associated fluctuations in the fractal dimension derived from the correlation dimension (DC) was discussed. The DC value was found to vary between 1.01 and 1.59, indicating that high-grade gold deposits were distributed along steep fractal gradients and that fractal dimension values could be used as a reliable proxy to efficiently understand the migration pathways of auriferous fluid. Studies have shown that the Hurst exponent of the Au grade sequence exhibited a strong dependence on the grade of mineralization, with gold mineralized veins persisting throughout the studied drill holes. Thus, fractal dimension gradients can serve as an important proxy for identifying the locations of potential economic gold deposits in unexplored areas. Moreover, this approach can be employed to map the distribution patterns of other types of ore deposits.

Application of integrated geological and structural investigations to the discovery of new mineral zones related to the Daping gold deposit, Southwest China

The Daping gold deposit is one of the largest gold deposits in the Ailaoshan gold belt of SW China. It has proven gold reserves of more than 70 tonnes and has been mined for 36 years. Finding new orebodies to extend the mine life has become urgent since the main gold orebodies are almost depleted. Ore deposit types in the Daping area include quartz-vein and porphyry gold types of mineralization. The quartz-vein ores are hosted in late Proterozoic diorite and Silurian limestones and controlled by NW trending faults. We have studied the ore-controlling structures to determine palaeo-stress directions of V1-2-3 and V37 orebodies, and the distribution of gold mineralization in the V1-2-3 orebodies. Based on the field observation, we identified six stages of structure in the Daping gold deposit, i.e., pre-mineralization (stage 1), syn-mineralization (stages 2 to 4), and post-mineralization (stages 5 and 6). The spatial distribution of gold orebodies at Daping is mainly controlled by the compressional faults of stage 1 that is associated with the Ailaoshan orogenic belt, and overprinted by structures of later stages. Orebodies from gold deposits in orogenic belts commonly have greater vertical dimensions than horizontal dimensions, suggesting that V1-2-3 orebodies may extend to deeper area.Our data indicate that higher gold grades and the thickest parts of the orebodies are associated with deeper parts of the V1-2-3 orebodies (up to 800 m in depth), and are likely related to a concealed mineralized porphyry which was intersected in drill core and identified as xenolith in lamprophyre dikes in the underground mine workings. The quartz-vein type gold mineralization at the Daping gold deposit was possibly overprinted by the porphyry gold mineralization, as indicated by the discovery of the new quartz-vein-associated orebodies beneath the current levels of Daping gold deposit and associated porphyry gold orebodies at Daping gold area.

Mapping of geological complexity and analyzing its relationship with the distribution of gold deposits in the Guangxi Gold Ore Province, Southern China

The Guangxi gold ore province contains >370 gold deposits with total resources of >260 t Au. Factor analysis (FA) of geochemical data, and calculation of lineament density within 10 km, 20 km, and 30 km circular search grids across a geological map, were applied in Guangxi to highlight geological complexity and to analyze its relationships with the distribution of gold deposits. The FA of stream sediment geochemical data for 42 elements, subjected first to center logarithmic transformation (clr), yield several element combinations that allowed distinction of metallogenic signatures from geological backgrounds. The element combinations of the first and second factors were Cd–Co–Cr–Cu–Li–Mn–Ni–P–Sb–Y–Zn–Mg and Be–Bi–La–Nb–Pb–Sn–Th–U–W–Zr–Al, and the spatial distributions of their factor scores overlap the Devonian to Permian strata and granite, respectively. The distribution of factor scores of mineralization-related element combination, Ag–As–Au–Mo, coincides with 70 % of gold deposits. The lineament density mapping can highlight different-scale faults and lithological contacts by using circular search grids with different diameters. The C–A fractal modeling for lineament density has indicated four populations, namely low, moderate-low, moderate-high, and high lineament densities. About ∼80 to ∼90 % of the known gold deposits exist in areas with moderate-low to moderate-high lineament densities. This highlights the importance of distinguishing geological complexity based on faults and lithological contacts, which are commonly the pathways for the focused fluid flow and gold ore formation. The deposit-scale geological complexity mapping has predicted several exploration targets, where high-grade gold orebodies have been prospected successfully by drilling in 2018. The geological complexity mapping is a kind of geochemical and geological complementation for resource potential assessment.

Mechanism and age of gold remobilization in orogenic gold deposit from primary laminated ore to the high-grade ore: A case study from Cenozoic Bangbu gold deposit, Tethyan Himalaya

The formation of high-grade gold ore has always been attractive, mostly located in Precambrian gold deposits with various mechanisms. Yet, in the orogenic Bangbu gold deposit, Tibet, we discovered that the coupled dissolution-reprecipitation (CDR) process and low melting point chalcophile elements (LMCE) -related melting are responsible for the formation of high-grade ore at ca. 38 Ma constrained by in-situ U-Th-Pb dating of hydrothermal monazite. Three generations of pyrite have been recognized, metamorphic barren pyrite (Py I) in the host schist, hydrothermal pyrite (Py II) in the preceding primary laminated ore with an Au grade of ∼8 g/t, and the hydrothermal coarse pyrite (Py III) in later massive ore with a grade of up to 29 g/t. In the primary laminated ore, the Py II in the sulfide ribbons is intergrown with native gold and colloform quartz and carries abundant trace element contents, such as Au, As, Cu, Pb, Zn, Te, Se, and Bi. These suggest that the rapid precipitation and local supersaturation occurred during the episodic crack-seal process. In the later high-grade massive ore, Py III exhibits distinct zonation, ranging from Py III-1 in the core to Py III-3 in the rim. The Py III-1, porous and rich in inclusions, has sharp boundaries and successive lattice orientation with the mantle Py III-2 suggesting a CDR process. Higher Au and As in Py III-2 than the Py III-1, and the close affinity between visible gold and LMCE melt inclusions at the boundary suggest that gold was remobilized and facilitated by the LMCE during the CDR process. The electron backscatter diffraction (EBSD) mapping result shows little crystallographic misorientations of Py III, excluding the deformation process that has significantly contributed to the remobilization of gold. The decrease of the δ34S ratio of pyrite between Py II (δ34S = 2.0‰ to 4.3‰, mean 3.4‰) and Py III (δ34S = −2.5‰ to 3.8‰, mean −0.2‰) most likely reveals a more oxidized condition in the open space which may trigger the CDR process and gold remobilization of the pyrite in the primary ore. Within the zonation of Py III, an increasing trend of the δ34S ratio represent the evolution of the redox state of fluids towards relatively reducing conditions during the healing of quartz veins. The newly obtained ca. 38 Ma age is comparable to regional amphibolite- to granulite-facies metamorphism during the continental subduction, which was considered to trigger the modification of primary gold orebody to form high-grade ore.

Nanoscale Distribution of Elements in Gold: Examples from Contrasting Deposit Types

Abstract Quantifying the distribution and nature of trace elements in native gold is a novel approach to understanding the genesis of gold deposits and has implications for metallogenic processes, mineral exploration, and metallurgical processing. Most previous research on the formation of gold deposits has utilized proxies for gold, rather than gold itself, to infer its source, transport, and depositional mechanisms, despite the difficulty in establishing unequivocal relationships among the proxies and gold. This approach has left many questions regarding the formation of high-grade coarse gold. This contribution presents results on the composition and distribution of trace elements in native gold using electron probe microanalysis and, for the first time, atom probe tomography. Gold grains selected are from a deformed and metamorphosed Archean orogenic gold deposit (Preston Mine) and a young, undisturbed epithermal gold deposit (McLaughlin mine) which are endmembers in terms of deposit type and geologic time. Results show that Cu, Ag, and Hg are homogenously distributed in gold while Sb is not, which raises questions regarding the substitution mechanisms of large radii metallic elements in gold. These data provide new insights into the incorporation of trace elements in gold, as well as primary and secondary processes related to the formation of high-grade gold deposits through time.