Largest Gold Deposits Research Articles

Zircon U Pb geochronology and Sr-Nd-Pb-Hf isotope geochemistry of the Dahuabei pluton from the northern margin of North China Craton: Implications for petrogenesis, tectonic setting and Au Mo mineralization

The Late Paleozoic Dahuabei Pluton is located in the Wulashan area at the northern margin of the North China Craton (NCC), adjacent to the Hadamengou gold deposit, the largest gold deposit in Inner Mongolia, China. However, its petrogenesis and its relationship with AuMo mineralization remain debatable. In this contribution, a geochemical, isotopic, and geochronological study was carried out on the Dahuabei pluton to constrain its magma sources, petrogenesis, and tectonic setting, and further discuss the linkage between the magmatism and AuMo mineralization. The Dahuabei pluton mainly consists of monzogranite and syenogranite, with abundant mafic microgranular enclaves (MMEs) in the monzogranite. Zircon UPb dating shows that the ages of the Dahuabei pluton range from 357 to 353 Ma, suggesting an Early Carboniferous emplacement. The crystallization age of the MMEs (355.4 ± 3.2 Ma) is nearly simultaneous to that of host monzogranite (356.5 ± 2.0 Ma). Geochemically, the granitoids show high-K calc-alkaline and weakly peraluminous affinities and are classified as highly to moderately fractionated I-type granites. Moreover, they are enriched in light rare earth elements and large ion lithophile elements, depleted in high field strength elements, resembling typical continental arc magmatic rocks. Isotopically, the granitoids have negative εNd(t) (−10.0 to −7.3) and εHf(t) values (−10.0 to −4.4), as well as old Nd (1923–1704 Ma) and Hf (1986–1697 Ma) model ages, suggest that the granitoids were mainly derived from partial melting of ancient mafic lower continental crust, with involvement of mantle-derived components. The sharp contacts, fine-grained igneous textures, numerous xenocrysts from host granites, and similar crystallization ages with host granites of the MMEs suggest a magma mingling process, in which the MMEs represent discrete mafic to hybrid magma globules formed by undercooling after the injection of hotter mafic magma into cooler felsic magma. Geochemical and isotopic data (εNd(t) of −6.2 to −5.4 and εHf(t) of −10.2 to −2.8) indicate that the parental magma of MMEs was derived from partial melting of the enriched subcontinental lithospheric mantle metasomatized by slab-derived fluids and had experienced significant fractional crystallization. The indistinctive chemical and isotopic contrast between MMEs and host monzogranite implies their chemical and isotopic exchange during various degrees of magma mingling. Integrating the geochronological, geochemical, and Pb isotope data of the Hadamengou AuMo deposit and the Dahuebei pluton, we propose that the magmatic-hydrothermal system emanated from the magma mingling event during the emplacement of the Dahuabei pluton might be favorable for the mineralization. The Late Devonian to Early Carboniferous magmatism may have been a trigger for the formation of the AuMo deposits in the northern margin of the NCC.

Apatite records metamorphic and hydrothermal fluid evolution at the large Shuangqishan orogenic gold deposit, SE China

Orogenic gold deposits are currently the world’s major source of Au, but uncertainty exists in the timing of mineralization relative to the ages of host rocks, metamorphism, and magmatism. Consequently, the origin and detailed evolution of ore-forming fluids have long been elusive. Apatite occurs widespread in various types of mineral deposits and can provide valuable information on ore genesis. Here, we present textural, high-precision in situ U-Pb geochronological, trace elements, and Sr isotope data for metamorphic and hydrothermal apatite in the Shuangqishan gold deposit in southeastern China. These data, together with U-Pb dates of metavolcanic host rocks, granitic and mafic intrusive rocks, allow us to precisely constrain the timing of mineralization and reconstruct the history of the ore-forming fluids there. The apatite crystals within metamorphic and auriferous quartz veins can be grouped into three generations according to cathodoluminescence imaging and trace element concentrations: Ap1 precipitated in the pre-mineralization metamorphic stage, whereas Ap2 and Ap3 formed in the auriferous hydrothermal stage. Metamorphic Ap1 displays a negative Eu anomaly, indicating a predominance of Eu2+ and crystallization under relatively reduced conditions. On the other hand, syn-gold hydrothermal Ap2 and Ap3 have marked positive Eu anomalies. Radiometric ages for metamorphic Ap1 are at ca. 461 Ma, whereas hydrothermal Ap2 and xenotime from auriferous quartz gave U-Pb ages of 425 ± 15 Ma and 416 ± 15 Ma, interpreted as the time of gold mineralization. Emplacement ages determined by U-Pb zircon data are 439 ± 2 Ma for granitic intrusion and 427 ± 2 Ma for a mafic dike in the mining district. Mineralization, therefore, postdates the metamorphism of local host rocks and granitic magmatism by ∼35 ± 24 m.y. and ∼14 ± 17 m.y., respectively. The synchronism of gold genesis and mafic magmatism provides additional evidence for a mantle derivation of the ore-forming fluids. The highly radiogenic 87Sr/86Sr ratios obtained for Ap1 (0.7178−0.7302) are consistent with its precipitation from a metamorphic fluid. Higher Sr concentrations (Ap2 = 1228−2884 ppm, Ap3 = 2325−3169 ppm) and positive Eu anomalies (Eu/Eu*: Ap2 = 1.03−2.84, Ap3 = 2.00−4.30) but lower and variable 87Sr/86Sr ratios in hydrothermal Ap2 (0.7100−0.7165) and Ap3 (0.7086−0.7116) are mainly ascribed to extensive fluid-wall rock exchange of Sr during mineralization. It is therefore suggested that fluid-rock reaction played a vital role in the observed positive Eu anomalies of hydrothermal apatite. Our study highlights the usefulness of apatite as a novel and robust geochronological, geochemical, and isotopic indicator of complex mineralization processes in hydrothermal gold deposits.

Ore-controlling structures of the Qingchengzi Pb-Zn-Au-Ag orefield, northeastern China and significance for deep ore prospecting: Revealed from gravity and magnetic anomalies

Located in the middle of Liaodong Rift, the Qingchengzi orefield is an important Pb-Zn-Ag-Au polymetallic mining area in Northeast China. The Pb-Zn-Au-Ag mineralization mainly occurs in the Liaohe Group strata and is closely related to Indosinian and Yanshanian magmatic intrusive bodies. Currently the Qingchengzi orefield is poorly explored at depths greater than 1500 m, with no large deep concealed gold deposit being discovered yet. This study focused on delineating deep concealed ore-controlling structures from the local gravity and aeromagnetic anomalies in different wavelet orders acquired by the application of discrete wavelet transform (DWT), and evaluating their potential for undiscovered gold-rich polymetallic mineralization in the Qingchengzi orefield. We started from summarizing the characteristics of gravity and magnetic anomalies corresponding to the ore-controlling structures obtained from surface geology, exploration profiles and drilling results. Under the guidance of the correspondence, we interpreted the structural control factors of the tectonic-magmatic metallogenic system for the whole Qingchengzi orefield, such as faults, strata, magmatic bodies and mineralized alteration belts. Based on the spatial relationship between the known deposits and structural factors interpreted from gravity and magnetic anomalies, it is concluded that the gold-rich polymetallic deposits and mineralization are controlled by five major deep regional faults (two in the NE direction and three in the NW direction). Moreover, the borders of the Indosinian and Yanshanian concealed magmatic intrusions, as well as the intersections of deep regional faults are more favorable for the deposition of gold-rich polymetallic minerals. A NNE-trending concealed structure was found in the middle of our study area, connecting the Shuangdinggou, Qingchengzi, Xinling and Gujiagou intrusions, serving as a possible channel for magmatic activities in the Indosinian. The forward modeling results on the gravity and magnetic data of profile L1 indicates that the Liaohe Group strata and the possible Mesozoic concealed intrusion lies beneath the Paleoproterozoic Dadingzi granite. This finding supplements the traditional understanding that the Paleoproterozoic Dadingzi granite is the deepest boundary for ore prospecting, and provides new thoughts searching for deep-seated ore bodies for the Xiaotongjiapuzi ore deposits.

Crustal conductivity footprint of the orogenic gold district in the Red Lake greenstone belt, western Superior craton, Canada

AbstractA magnetotelluric (MT) study across the Red Lake greenstone belt of the western Superior craton, Canada, images a 50-km-long north-dipping conductor (<20 Ω·m) at 20–25 km depth and subvertical conductors spatially correlated with crustal-scale shear zones and large orogenic gold deposits. The conductors are interpreted to be the conductivity signature of the deep crustal source of the auriferous fluids and pathways of the orogenic gold system. The geophysical results, supported by existing geochemical and fluid inclusion studies, suggest that the Au- and CO2-rich fluids responsible for gold mineralization were released by devolatilization of supracrustal rocks underthrust to mid- to lower-crustal levels during subduction. This MT study links shallow gold mineralization to a deep crustal source region, demonstrating the connection between a crustal suture zone and the formation of orogenic gold deposits in an Archean greenstone belt.

Dubreuilville (Canada): A Strategic Action Plan for a Rural Community

The town of Dubreuilville, with a population of just under 1,000, is located in Northern Ontario, Canada, approximately one thousand kilometers North-West of Toronto. The region was previously known for lumber production. When the Canadian lumber market collapsed due to the imposition of duties by Washington, the local mill shut down. Large gold deposits were found nearby, and Dubreuilville became a mining town almost overnight. Half of the population had left by the time the mine opened, and part of the workforce commutes from cities located up to six-hour drives away. With the opening of a second gold mine in the area planned for 2023, Dubreuilville had to prepare to attract and retain more workers for the project to succeed and for the town to prosper. Below is the strategic plan that was prepared by Mayor Nantel and Economic Development Officer Melanie Pilon, with the help of a Laurentian University Management professor and three students.

Geology, Pyrite Geochemistry and Metallogenic Mechanism of the Wulong Gold Deposit in Liaodong Peninsula, North China Craton

The Wulong deposit is a large gold deposit in the Liaodong peninsula (North China Craton). Silicic and pyrite alterations are well-developed in the deposit and closely related to mineralization. The least altered and silicified microdiorite samples were selected for major and trace element analyses to reveal the elemental migration/enrichment. Pyrites of stage 1 (Py1) were selected for backscattered electron (BSE) imaging and LA-ICP-MS trace element analyses to reveal their possible metallogenic link. Mass balance calculation showed that Al2O3, CaO, Fe2O3, K2O, SiO2, Ag, As, Cu, and Pb were brought in, whereas MgO, Na2O, FeO, Cr, Zn, and Ni were leached out during silicification. LA-ICP-MS trace element analyses show that Py1 has higher Au and Zn contents than Py2 and Py3, Py2 has higher Au and Cu contents than Py1 and Py3, and Py3 has higher Pb, Cu, and As contents than Py1 and Py2. During the process of silicification and pyritization, the depleted H+ concentration and HS− concentration in the ore-forming fluids led to instability of the Au(HS)2− complexes and led to gold precipitation. The depleted sulfur and the reduced temperature during the precipitated of bismuthinite also led to instability of the Au(HS)2− complexes and gold precipitation.

Mineralization Based on CSAMT and SIP Sounding Data: A Case Study on the Hadamengou Gold Deposit in Inner Mongolia

The Hadamengou deposit is the largest gold deposit in Inner Mongolia. However, given that the sources of ore-forming alkaline magmatic hydrothermal solutions and ore-controlling structures are still controversial, the theories behind the genesis of the deposit have been controversial. In this study, four controlled-source audio magnetotellurics (CSAMT) and spectral induced polarization (SIP) profiles in the mining area were used to obtain the underground resistivity model and the pseudo section map of the apparent frequency dispersivity based on fine inversion. In the resistivity model, there are two high-resistivity blocks with resistivity greater than 3000 Ω m and three low-resistivity channels with resistivity less than 50 Ω m. Combined with the regional geological and drilling data, it is inferred that the high-resistance bodies, R4 and R5, may be alkaline magmatic intrusions related to multiple stages of magmatic hydrothermal activities, ranging from the Precambrian to Yanshanian periods. The highly conductive channels, C3, C5, and C4, may represent the Baotou-Hohhot fault, secondary faults, and ductile shear zone, respectively, which were formed in the Precambrian era and underwent multiple activations during the Hercynian to Yanshanian period. According to the spatial relationship, it is inferred that the ductile shear zone is an important ore-controlling and ore-hosting structure. However, the Baotou–Hohhot fault may be a pre-metallogenic fault rather than an ore-controlling fault. By comparing the resistivity model with the pseudo section of the apparent frequency dispersivity, it was found that all the known gold veins are located in the superimposed area of low resistivity and high-frequency dispersivity. It is speculated that the ductile shear zone outside the alkaline magmatic rock with the superimposed characteristics of low resistivity and high-frequency dispersivity is the favorable area for mineralization.

Garnet geochemistry of the giant Beiya gold–polymetallic deposit in SW China: Insights into fluid evolution during skarn formation

The Beiya deposit in the central Jinshajiang–Ailaoshan metallogenic belt of SW China is the country’s largest gold skarn and third largest gold deposit. In this study of the Beiya deposit, we use garnet mineralogy and geochemistry to delineate three skarn alteration zones (i.e., contact, proximal and distal skarn). We investigate the possible controls on the rare earth element (REE) incorporation into skarn-type garnet, the ore-fluid evolution, and metasomatic dynamics. Garnet in the Beiya deposit belongs to the grossular–andradite solid solution series, and comprises three types: (1) Grt1 andradite (Adr67–88Grs9–32) in the contact skarn, exhibiting light REE (LREE) enrichments, heavy REE (HREE) depletions, and positive Eu anomalies; (2) Oscillatory-zoned Grt2 andradite (Adr55–98Grs1–44) in proximal skarn, which has moderate to low LREE/HREE enrichments and varying Eu anomalies; (3) Grt3 andradite (Adr29–76Grs22–69) in distal skarn with low LREE/HREE enrichments and minor negative Eu anomalies. Grt1, Grt2 and Grt3 yielded lower intercept U–Pb ages of 36.4 ± 1.8 Ma (MSWD = 0.87, n = 67), 34.8 ± 0.7 Ma (MSWD = 1.8, n = 31) and 33.4 ± 1.0 Ma (MSWD = 1.2, n = 25). Garnet shows compositional changes from Grt1 to Grt3 due to the fluid-wallrock reactions. With decreasing andradite and increasing grossular contents, the (La/Yb)N ratio decreases. Ore-forming fluids changed from diffusive metasomatism to infiltration metasomatism, and then again to diffusive metasomatism. Meanwhile, the ore-fluid physicochemical conditions changed from acidic to near-neutral (both oxidised), whilst the water/rock ratio first increased and then decreased. The proximal skarn recorded high water/rock ratio with intermittent boiling events, leading to fluctuating oxygen fugacity, which is conducive to ore deposition. Therefore, the skarn-type garnet composition from the various alteration zones can reveal the fluid activity and physicochemical fluid evolution path, preserving rich information about the mineralisation process.

Combining 3D Geological Modeling and 3D Spectral Modeling for Deep Mineral Exploration in the Zhaoxian Gold Deposit, Shandong Province, China

The Jiaodong Peninsula hosts the main large gold deposits and was the first gold production area in China; multisource and multiscale geoscience datasets are available. The area is the biggest drilling mineral-exploration zone in China. This study used three-dimensional (3D) modeling, geology, and ore body and alteration datasets to extract and synthesize mineralization information and analyze the exploration targeting in the Zhaoxian gold deposit in the northwestern Jiaodong Peninsula. The methodology and results are summarized as follows: The regional Jiaojia fault is the key exploration criterion of the gold deposit. The compression torsion characteristics and concave–convex section zones in the 3D deep environment are the main indicators of mineral exploration using 3D geological and ore-body modeling in the Zhaoxian gold deposit. The hyperspectral detailed measurement, interpretation, and data mining used drill-hole data (>1000 m) to analyze the vectors and trends of the ore body and ore-forming fault and the alteration-zone rocks in the Zhaoxian gold deposit. The short-wave infrared Pos2200 values and illite crystallinity in the alteration zone can be used to identify 3D deep gold mineralization and potential targets for mineral exploration. This research methodology can be globally used for other deep mineral explorations.

Analysis of the mineral resource base of gold mining in the Lena gold-bearing district and substantiation of the development directions of placer mining methods

Development of the gold mining industry is in the first place associated with an increase in the mineral resource base, development of promising deposits and improvement in the quality of raw materials. At the same time, experts have been noting a deterioration in the quality of alluvial gold reserves over the last years both in Russia as a whole and in Eastern Siberia in particular. Therefore, the purpose of this research is to analyze the dynamics of the mineral resource base of gold mining in the Lena gold-bearing area as well as to substantiate the development trends of the placer development technology. The assessment was given to the state of the mineral resource base of the gold mining industry of the Irkutsk region in the period from 2000 to 2021. A quantitative and qualitative characteristic of alluvial gold reserves was provided with identified key changes caused by placer mining over the past 20 years. Having indicated the deterioration dynamics in the quality of alluvial gold reserves, the authors specified its reasons for the period under analysis. In addition, a brief description of the main mining and engineering indicators of the large and medium-sized alluvial gold deposits worked out in recent years is given. The distribution structure of reserves in technogenic deposits is presented. The conclusions are formulated on the results of the research performed, relevant problems of modern placer gold mining are formulated and the prospects of placer mining in the Irkutsk region are assessed. The replenishing possibilities of the mineral resource base by involving technogenic reserves in the development are described.

ЭКСПЕДИЦИЯ ГЕОЛКОМА ВСНХ СССР (1925 Г.) ПО ОЦЕНКЕ ЗОЛОТОНОСНОСТИ БАССЕЙНА Р. АЛДАН

The expedition of the Geolkom (Geological Committee) of the VSNX USSR carried out its work in Yakutia in 1925 under the guidance of the famous geologist V.N. Zverev. The main goal of the expedition was to justify the genesis and nature of gold placers in the Aldan River basin, to define the depth of occurrence of gold-bearing layers and the boundaries of their strike in plan. Such information was essential for a comprehensive and reliable assessment of the potential of a new, practically unexplored before, large alluvial gold deposit in the east of the country. The expedition to the newly discovered Aldan gold-bearing province was to play a decisive role in determining the future status and funding of the new gold mining enterprise. The importance of the goal being fulfilled became the reason for the accelerated preparation of the expedition, so its organization was unscheduled, carried out outside the programs and with special funds of the Geological Committee of the VSNX USSR. Based on the study of surviving archival sources, it was established that the expedition members carried out thorough geological, exploration and topographic work on gold deposits in the area of the middle Aldan River, including its right tributary basins. One of the main tasks of the expedition ruled by V.N. Zverev was the calculation of explored reserves and the assessment of forecast gold resources in the explored area. In general, the expedition fulfilled its tasks, managed to form a theoretically substantiated idea of the genesis of placer deposits of Aldan gold, provided materials that make it possible to bring the necessary scientific base under the general plan of exploration work for future placer gold mining along the Aldan River basin.

Karakteristik Mineralisasi Endapan Emas Epitermal Sulfidasi Rendah di Daerah Mekarbakti, Kecamatan Bungbulang, Kabupaten Garut, Provinsi Jawa Barat

The southern mountains of western Java have been known to have large gold deposit potential. The Mekarbakti area, located in Garut regency, is known to have gold-bearing quartz veins, but the distribution and characteristics of these veins are not well recorded. The purpose of this study is to determine the geological conditions of the deposits and the characteristics of the epithermal deposits in the study area, in term of alteration, ore mineralization, vein texture, and ore geochemistry. Field work includes random sampling of veins from surface outcrops and cores. Laboratory analysis includes mineragraphic, geochemical analysis by means of Fire Assay Atomic Absorption Spectrophotometry (FA-AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) . The lithology of the Mekarbakti area is composed of volcanic rocks including andesite lava, andesite intrusion and pyroclastic rocks such as breccia and tuff. The mapping results show that the hydrothermal alteration that developed is divided into three zones of alteration type, namely the silicification zone (silica + - clay), the argillic zone (kaolinite + - smectite - illite) and the propylitic zone (chlorite - smectite - epidote - illite). Quartz texture is generally dominated by brecciated, colloform, comb, lattice bladed and cockade textures. The texture interpretation of the veins shows a crystalline quartz zone, which is enriched in base metals such as galena, sphalerite and chalcopyrite and a crustiform – colloform zone which usually contains gold and silver. Veins in the study area contain the elevated grades of 3.21 ppm Au and 75.5 ppm Ag.

Geological and structural position of the Svetlinsky gold deposit (Southern Urals)

The paper presents the geological and structural position of the large Svetlinsky gold deposit in the Kochkar anticline (Southern Urals), localized in the zone of the Late Paleozoic (D3) deep thrust of the western dip. The study confirms and clarifies the notion of its multiphase and polychronism. The thrust caused bending moments in its wings, subsidence of the lying crust, emergence of a shallow marine basin with rapid accumulation of terrigenous carbonate sediments (C1v), and formation of numerous landslide structures. The heating of rocks in the anticline core was accompanied by granitization and dome formation. A small Svetlinsky dome formed in the immediate vicinity of the thrust, creating a thermobaric gradient field (С2). The zone of dome dynamic influence also includes the adjoining thrust area, complicated by a series of sub-vertical thrusts of sub meridional strike and numerous steeply dipping subparallel cracks of the latitudinal strike, synchronously filled with vein quartz and accompanied by hydrothermal metasomatic rock transformations. The formation of the gold deposit occurred during the post-collisional relaxation stage (from P1 to, probably, the Early Jurassic). The association of gold mineralization with the Svetlinsky dome is indicated by the presence of native gold in Neogene ravine placers in the dome area and marbles of the Svetlinsky deposit, in association with fluorite, F-phlogopite, Cr-muscovite, pink topaz, pure quartz, and native sulphur. The presence of native gold in Neogene ravine placers in the dome area and marbles of the Svetlinsky deposit, in association with fluorite, F-phlogopite, Cr-muscovite, pink topaz, pure quartz, and native sulphur, indicates the association of gold mineralization with the Svetlinsky dome.

LA-ICP-MS zircon U-Pb dating of granite porphyry and 40Ar/39Ar dating of chromian sericite of the Shuangqishan and Xiaoban gold deposits in central Fujian, South China and their restriction on gold mineralization

The shuangqishan and Xiaoban are the two largest gold deposits in the Dehua-Youxi-Yongtai (DYY) mineral concentrated area of central Fujian Province. They are located adjacent to each other and show similarities in geological background, metallogenic characteristics and mineral assemblage. The orebodies are hosted in the Caledonian alaskite and the metamorphic rock of Neoproterozoic Daling Formation. Gold mineralization is closely related to pyritization, silicification, and micatization, with native gold mostly occurring in the cracks of pyrite, which formed slightly later than pyrite. In this paper, geochronologic work has been conducted on the granite porphyry and chromian sericite related to gold mineralization in the two deposits to determine the age of mineralization and discuss the genesis of the deposits. The chromian sericite is a hydrothermal alteration product of granite porphyry, and is a main indicator of gold enrichment. The plateau 40Ar/39Ar isotopic dating of chromian sericite indicates the mineralization ages of the two deposits were 146.21 ± 1.59 Ma and 149.28 ± 1.26 Ma respectively, similar to the LA-ICP-MS zircon U-Pb age(149.0 ± 1.0 Ma) of granite porphyry in the mining district. The ages of the chromian sericite and granite porphyry point to a close link with a large-scale magmatism event at the late stage of Late Jurassic in central Fujian. Based on the geology, alteration, mineralization and chronology characteristics, the Shuangqishan and Xiaoban gold deposits can be classified as the magmatic hydrothermal type gold deposits.

Genesis of orogenic gold systems in the Daduhe belt: Evidence of long-lived fertile mantle lithosphere as a source of diverse metallogeny on the western margin of the Yangtze Craton, China

The poorly documented Daduhe gold belt on the western margin of the Yangtze Craton, an important metallogenic belt in southwest China, is characterized by typical orogenic gold systems against a highly anomalous geodynamic setting. A synthesis of regional and deposit geology, mineralization ages, and S-O isotopic compositions of 33 gold deposits from the Danba-Kangding-Shimian-Mianning area of the belt reveals regional metallogenic patterns, establishes a consistent genetic model, and demonstrates a source equivalent to other diverse mineral systems on the western margin of the Yangtze Craton. The Daduhe orogenic gold deposits are controlled by the lithosphere-scale Xianshuihe and Anninghe strike-slip faults in the northern and southern segments of the belt, respectively. The alteration and ore mineral assemblages of the Daduhe orogenic gold deposits define a wide range of hypozonal, mesozonal, and epizonal sub-types. They formed during two episodes: 1) Early Jurassic gold mineralization related to closure of the Paleo-Tethys Ocean, with a large hypozonal gold deposit on the margin of the Danba dome in the northern segment; 2) Cenozoic gold mineralization associated with continental collision on the Tibetan Plateau, with small mesozonal and epizonal gold deposits in shear zones in migmatite basement and at contacts with cover sequences in both the northern and southern segments. At the belt and deposit scales, the ore-controlling structures for both mineralization episodes are NNE-trending second-order extensional faults or their intersections with the dominant NW-trending compressional faults. The three deposit sub-types have overlapping δ34S of 0 ∼ 10‰, δ18Ofluid of 6 ∼ 11‰, and low He-Ar isotope ratios, all consistent with derivation of ore fluids from metasomatized mantle lithosphere. Importantly, the Daduhe orogenic gold deposits have similar S-O-He-Ar isotope compositions to the giant IOCG, Cu-Ni-PGE, Fe-V-Ti, anomalous porphyry Cu-Mo-Au, and carbonatite-related REE deposits in the Panxi region on the shared margin of the western Yangtze Craton. This suggests that these diverse mineral systems have a common source of ore fluids and metals derived from fertile mantle lithosphere during different geodynamic and metallogenic events. Such a widespread hydrous metal-rich deep source with lithosphere-scale faults as ore fluid pathways, and a depth continuum of orogenic gold deposits in the Daduhe belt suggest a high prospectivity and a higher future gold endowment for the belt. This study adds to an increasing awareness of the diversity of mineral systems on specific craton margins globally.

Genesis of the Maoling gold deposit in the Liaodong Peninsula: Constraints from a combined fluid inclusion, C-H-O-S-Pb-He-Ar isotopic and geochronological studies

The large tonnage Maoling gold deposit (25 t @ 3.2 g/t) is located in the southwest Liaodong Peninsula, North China Craton. The deposit is hosted in the Paleoproterozoic metamorphic rocks. Four stages of mineralization were identified in the deposit: (stage I) quartz-arsenopyrite ± pyrite, (stage II) quartz-gold- arsenopyrite-pyrrhotite, (stage III) quartz-gold- polymetallic sulfide, and (stage IV) quartz-calcite-pyrrhotite. In this paper, we present fluid inclusion, C-H-O-S-Pb-He-Ar isotope data, zircon U-Pb, and gold-bearing sulfide (i.e. arsenopyrite and pyrrhotite) Rb-Sr age of the Maoling gold deposit to constrain its genesis and ore-forming mechanism. Three types of fluid inclusions were distinguished in quartz-bearing veins, including liquid-rich two-phase (WL type), gas-rich two-phase (GL type), and daughter mineral-bearing fluid inclusions (S type). Fluid inclusions data show that the homogenization at temperatures 197 to 372 °C for stage I, 126 to 319 °C for stage II, 119 to 189 °C for stage III, and 115 to 183 °C for stage IV, with corresponding salinities of 3.7 to 22.6 wt.%, 4.7 to 23.2 wt.%, 5.3 to 23.2 wt.%, and 1.7 to 14.9 wt.% NaCl equiv., respectively. Fluid boiling was the critical factor controlling the gold and associated sulfide precipitation at Maoling. Hydrogen and oxygen stable isotopic analyses for quartz yielded δ18O = −5.0‰ to 9.8‰ and δ D = −133.5‰ to −77.0‰. Carbon stable isotopic analyses for calcite and ankerite yielded δ13C = −2.3‰ to −1.2‰ and O = 7.9‰ to 14.1‰. The C-H-O isotope data show that the ore-forming fluids were originated from magmatic water with meteoric water input during mineralization. Hydrothermal inclusions in arsenopyrite have 3He/4He ratios of 0.002 Ra to 0.054 Ra, and 40Ar/36Ar rations of 1225 to 3930, indicating that the ore-forming fluids were dominantly derived from crustal sources almost no mantle input. Sulfur isotopic values of Maoling fine-grained granite range from 6.‰1 to 9.8‰, with a mean of 7.7‰, δ34S values of arsenopyrite from the mineralized phyllite (host rock) range from 8.9‰ to 10.6‰, with a mean of 10.0‰, by contrast, δ34S values of sulfides from ore vary between 4.3‰ and 10.6‰, with a mean of 6.8‰, suggesting that sulfur was mainly originated from both the host rock and magma. Lead radioactiveisotopic analyses for sulfides yielded 206Pb/204Pb = 15.830–17.103, 207Pb/204Pb = 13.397–15.548, 208Pb/204Pb = 35.478–36.683, and for Maoling fine-grained granite yielded 206Pb/204Pb = 18.757–19.053, 207Pb/204Pb = 15.596–15.612, and 208Pb/204Pb = 38.184–39.309, also suggesting that the ore-forming materials were mainly originated from the host rocks and magma. Zircon U-Pb dating demonstrates that the Maoling fine-grained granite was emplaced at 192.7 ± 1.8 Ma, and the host rock (mineralized phyllite) was emplaced at some time after 2065.0 ± 27.0 Ma. Arsenopyrite and pyrrhotite give Rb–Sr isochron age of 188.7 ± 4.5 Ma, indicating that both magmatism and mineralization occurred during the Early Jurassic. Geochronological and geochemical data, together with the regional geological history, indicate that Early Jurassic magmatism and mineralization of the Maoling gold deposit occurred during the subducting Paleo-Pacific Plate beneath Eurasia, and the Maoling gold deposit is of the intrusion-related gold deposit type.

Metamorphic Conditions and Raman Spectroscopic Carbonaceous Material Thermometry of Host Schists of Olympiada and Eldorado Gold Deposits (Yenisey Ridge, Russia)

Metamorphic processes play a key role in forming orogenic gold deposits. In this paper, we present new evidence that host schists of the two largest gold deposits of the Yenisey ridge (Russia) Olympiada and Eldorado underwent a single stage of metamorphism in contrast to surrounding blocks. This metamorphism is of moderate thermal gradient and belongs to the Barrovian type, which is typical for the collisional event in the time range 800–850 Ma. The new Ar/Ar age data presented in this paper and the review of magmatic and metamorphic events and ore-forming processes indicate that the most productive stage (gold-sulfide-quartz) correlates well in time with the regional metamorphism of the Barrovian type. This indicates that metamorphic processes can have a crucial role in forming gold deposits of the Yenisey ridge. Carbonaceous material thermometry indicates a wide range of obtained temperatures around 90–150 °C around the mean temperature for each sample. The highest temperatures are close to the peak metamorphic temperatures estimated by garnet-biotite thermometry.

Material Composition of the Mesozoic Alkaline Rocks of the Yukhta Massif (Southern Yakutia, Central-Aldan Ore Region)

The paper considers the petrographic composition of the Mesozoic alkaline igneous rocks of the Yukhta massif. It is part of the Central Aldan ore region and is spatially located in the central part of the Nymnyr block. The massif is a large multiphase structure, of the most productive stage of the territory’s development – the Mesozoic tectonic-magmatic activation of the Aldan-Stanovoy shield. Determination of the qualitative quantitative-mineralogical characteristics of the 2 and 3 phases of intrusion (emplacement) most promising for gold-radioactive mineralization with the help of crystal-optical methods was the main goal of this work. As a result of petrographic studies of Mesozoic alkaline igneous rocks, it is defined that, the Yukhta massif is a multiphase magmatic structure, with decrease of the content of dark-colored minerals in rocks from the early to later phases of intrusion. In general, the rocks of the massif bear significant traces of secondary changes, which are related to the gradual formation of the massif. According to the features of the composition of the massif rocks, it was found that the latter could be formed from residual differentiates during the fractional crystallization of rock-forming minerals with the involvement of plagioclases. The Yukhta massif is associated with the large Samolazovskoye gold deposit, which formation is related to an intense contact-metasomatic impact on carbonate rocks. Hydrothermal-metasomatic transformations of the latter are the products of multi-stage silica-alkaline metasomatosis associated with the second and especially with the third phases of the massif intrusion, and with further weathering processes, involving karst formation, disintegration of gold-ore metasomatites and the formation of a thick oxidation zone. From whence it is concluded that uranium being a chemically active element does not accumulate in a hypergenic form within the Yukhta massif. Where the weathering crust is intensively developed, a gold-ore type of mineralization is observed. On the other hand, the rocks of the massif itself, in particular syenites of the 2 and 3 phases of intrusion, may be promising for the uranium-thorium-rare earth (U-Tn-REE) type of mineralization. In general, these studies in this direction will provide insight into a number of issues related to the study of the evolution and metallogeny of the Mesozoic tectonic-magmatic activation of the Aldan-Stanovoy Shield

Magma evolution and Cu-Au mineralization potential of the Upper Devonian-Lower Carboniferous Tulasu basin, Western Tianshan Orogen (NW China): Apatite U-Pb dating and geochemical perspectives

The large Axi low-sulfidation epithermal gold deposit (reserve: 50 tonnes Au) is one of the most important gold deposits in the Tulasu basin (Western Tianshan Orogen, NW China), and is hosted by the Upper Devonian-Lower Carboniferous Dahalajunshan Formation volcanic rocks. Due to the close relationship between the genesis and spatial distribution of epithermal gold and porphyry copper deposits, whether the latter is buried beneath the Tulasu basin is highly debated.In this study, apatite and zircon grains from nine ore-hosting volcanic rocks were LA-ICPMS U-Pb dated and analyzed for their minor and trace element compositions. Zircon U-Pb dating suggests multiphase magmatism, with the main phase at ca. 370 and 360 Ma. Apatite U-Pb dating results are consistent with those of zircon U-Pb dating and previous zircon dating works (ca. 380 to 350 Ma), demonstrating the accuracy of apatite U-Pb dating. The apatite Cl content varies with age, which shows that it has the potential to record Cl replenishment from the subducting slab into the mantle wedge. Compared with the apatite Cl content from porphyry Cu deposits worldwide, the apatite Cl content from Axi is much (1–2 wt%) lower, suggesting low potential in forming porphyry copper deposits.

Structural controls on the gold mineralization at the eastern margin of the North China Craton: Constraints from gravity and magnetic data from the Liaodong and Jiaodong Peninsulae

The eastern block of the North China Craton (NCC) has been completely decratonized and it hosts numerous early Cretaceous gold deposits dated at about 130–120 Ma. The Jiaodong Peninsula in the easternmost NCC is the largest gold producing district in China, and it hosts more than 150 gold deposits with known gold resources of over 5000 tonnes (t). Also located at the eastern margin of NCC, the Liaodong Peninsula is poorly explored at depths greater than 800 m, with no large concealed gold deposit being discovered yet. In this paper, we carefully analyzed the gravity and magnetic characteristics of the ore-controlling structures in both provinces, including faults, Precambrian basement metamorphic rocks and the Mesozoic granitic intrusions. The deep regional faults are characterized by linear gravity gradient zones or elongated positive magnetic anomalies. The Precambrian basement metamorphic rocks usually have large-amplitude gravity and magnetic highs, while the lithological contacts of Mesozoic granite intrusions are commonly defined by gravity lows or narrow magnetic high anomalies. Interpretations from gravity and magnetic signatures predict two concealed lithological contacts between Mesozoic granites and Precambrian metamorphic rocks beneath Liaodong and Jiaodong.The spatial locations of known gold deposits are then correlated with the concealed structures inferred from the gravity and magnetic data in our paper. Their spatial relationship suggests that the gold mineralization is mainly controlled by oblique regional faults along the structural and lithological contacts between Mesozoic granites and Precambrian metamorphic rocks. Additionally, the structural intersections of different ore-controlling faults, especially the hydrothermal alteration zones at the contacts between Precambrian basement metamorphic rocks and the Mesozoic granites, are most favorable for the gold mineralization in the Liaodong and Jiaodong areas. Many large gold deposits are documented along a deep-seated, but concealed, structure beneath the Jiaodong gold district, while the Qingchengzi ore field and its vicinity in the Liaodong Peninsula still remain underexplored, despite of having a very similar structural setting, and deserve further investigation.