Giant Gold Deposit Research Articles

Sulfur isotopes of lamprophyres and implications for the control of metasomatized lithospheric mantle on the giant Jiaodong gold deposits, eastern China

Abstract The giant Jiaodong gold deposits represent one of the largest gold provinces (>5000 tons of Au) in the North China Craton of eastern China. They formed ~1.7 b.y. after high-grade metamorphism of the crust. The metasomatized subcontinental lithospheric mantle (SCLM) has been increasingly proposed as the main source of such gold mineralization, but the direct geochemical links remain scarce. Here, we present a comprehensive δ34S dataset of sulfides from fresh lamprophyres (130–121 Ma) that formed from the metasomatized SCLM that is spatially and temporally associated with the Jiaodong gold deposits (ca. 120 Ma). Due to the negligible effects of crustal contamination and magmatic degassing, the consistently high δ34S (4‰–6‰, n = 73) of lamprophyres from variable localities reveals δ34S-enriched mantle sources relative to the asthenospheric mantle (−1.3‰ ± 0.3‰). Combined with the radiogenic Sr-Nd-Pb isotope signatures of these lamprophyres, we determined that such high δ34S signatures could have resulted from a period of mantle metasomatism related to subducted continental materials. The lamprophyres share δ34S (4.4‰ ± 0.8‰) and Sr-Nd-Pb isotopes with coeval gold-mineralized diorites (ca. 120 Ma) beneath the ore field (δ34S: 5.4‰ ± 2.5‰), which were interpreted to have sampled the magma chamber underlying the auriferous fluid systems. The lamprophyres and diorites consistently indicate the key control of metasomatized SCLM, although these mantle-derived magmas followed different pathways from source to crust. These relatively primitive and evolved magmas all show S and Pb isotopes similar to ore-related sulfides from the Jiaodong gold deposits, particularly those formed in the deep parts and at the early stage of the Jiaodong auriferous fluid system (δ34S: 5‰–7‰). Such results suggest that the primary auriferous fluids are genetically linked to the magmas derived from the metasomatized SCLM. Combined with radiogenic isotopes, our study on the sulfur isotopes of mantle-derived magmas identifies the metasomatized mantle source of the gold and provides new evidence for establishing a geochemical link between metasomatized SCLM, derivative magmas, and the giant gold deposits, supporting the model that subduction-related metasomatism plays a key role in the enrichment of volatiles and gold in the SCLM for large-scale gold mineralization.

Gold mineralized diorite beneath the Linglong ore field, North China craton: New insights into the origin of decratonization-related gold deposits

Gold deposits in Precambrian cratons were mostly generated during the formation and stabilization of the cratons, but the North China craton is unusual in that its gold deposits were mainly formed ∼1.7 b.y. after its stabilization. A magmatic-hydrothermal origin or mantle-derived fluid source has been proposed for the giant gold deposits of the Jiaodong District in the eastern North China craton, but direct evidence is sparse, and the mineralization processes remain controversial. Here, we present the results of a comprehensive geological, geochronological, and geochemical study of the gold mineralized Xiejia diorite beneath the Linglong ore field at Jiaodong to link the gold mineralization to underlying magmatism. Magmatic zircon and titanite grains from the Xiejia diorite have laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) U-Pb ages of 121.3 ± 0.9 Ma to 120.8 ± 1.1 Ma and 121.7 ± 3.9 Ma, respectively, which are indistinguishable from the time of gold deposition throughout the Jiaodong District as constrained by previous studies. The diorite has a shoshonitic composition and is characterized by strong enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) along with significant depletion in high field strength elements (HFSEs) and heavy rare earth elements (HREEs). Samples of the diorite have high initial 87Sr/86Sr ratios, but low εNd(t) and ɛHf(t) values and low Pb isotope ratios. These geochemical characteristics are akin to those of contemporaneous mafic dikes in most gold mines at Jiaodong, indicating that the Xiejia diorite was most likely derived from an enriched lithospheric mantle source. The upper part of the diorite intrusion is pervasively altered and mineralized, containing an average of 0.32 g/t Au, but locally up to 7.59 g/t. Hydrothermal titanite from the mineralized diorite has a LA-ICP-MS U-Pb age of 122.3 ± 4.3 Ma, which is consistent with the gold-bearing pyrite Re-Os isochron age of 122.5 ± 6.7 Ma. Ore-related sericite aggregates from the Dongfeng gold deposit above the Xiejia diorite have a 40Ar/39Ar plateau age of 122.6 ± 1.3 Ma. Pyrite from the mineralized diorite yielded δ34SCDT values of 2.1‰−9.7‰, which are comparable with those of pyrite (δ34SCDT = 5.8‰−8.1‰, where CDT indicates the Canyon Diablo troilite standard) from gold ores of Dongfeng. Pyrite grains from both groups also have similar Pb isotope compositions. The S and Pb isotope data are consistent with values of mafic dikes that are spatially and temporally associated with gold veins in the Linglong ore field. The results presented here thus indicate a possible genetic link between gold mineralization in the Xiejia diorite and underlying magma presumably represented by the Xiejia diorite. The auriferous fluids exsolved from that magma and migrated upward along the Potouqing fault to form the Dongfeng gold deposit above the Xiejia diorite. The mineralized diorite thus links shallow gold mineralization to deep-seated mantle-derived magmatism generated during the extensive destruction of the North China craton induced by the rollback of the subducted paleo-Pacific plate.

Spatial coupling relationship between faults and gold deposits in the Jiaodong ore concentration area and the effect of thermal doming-extension on mineralisation

As the third largest gold ore-forming province in the world, the deep metallogenic potential of and exploration strategies for Jiaodong gold deposits have attracted substantial attention. By applying three-dimensional (3D) geological modelling to these super-giant and giant gold deposits, this study reveals the 3D morphological characteristics of the ore-bearing faults and the ore-related granites, analyses the relationships between ore body locations and slope dip angle changes in the faults, and discusses the coupling relationships among gold mineralisation, ore-controlling faults, and magmatic activities. In the 3D model, the dip angles of ore-controlling faults gradually decrease downwards and alternate between steep and gentle along the fault dip direction. The ore bodies mainly occur in areas with relatively high fault-dip-angle change rates. Hence, positions with fault dip angles of 20°–50° and change rates of ≥0.91 should be considered as target areas for prospecting deep gold ore bodies. In-depth analysis suggests that the ore-hosting faults, granites, and gold mineralisation resulted from regional thermal doming and extensional movements. Gold ore bodies in the Jiaodong Peninsula occur inside or on the periphery of Mesozoic granite. Strong magmatic activities during the transition from enriched to depleted mantle provided the necessary metallogenic and thermal dynamic environment for gold mineralisation. In particular, the magmatic evolution provided abundant ore-forming materials. The detachment faults with varied dip angles provided favourable space for gold mineralisation, as the fluctuations of ore-forming fluid pressure caused by sudden changes in these dip angles served as the primary mechanism underlying the step-like gold mineralisation pattern.

Structure of the Muruntau gold ore region in the Kyzyl-Kum desert (Central Asia)

The giant gold deposit Muruntau in most works belongs to the “orogenic type”. However, in the description of the geology of the deposit, there is usually no information about the stages (deformation, metamorphism) and the role of regional processes in the formation of host and mineralized rocks of the deposit. Our fieldwork provides unique geological evidence and previously unpublished data that are not reported in any other publications to date. This article presents the results of a detailed structural study of the terrane hosting the Muruntau gold deposit on the example of four sites and the results of deep drilling of two wells. The conducted studies confirm that the lowest Muruntau megaterrane consists of multi-stage metamorphosed Neoproterozoic–Early Paleozoic sedimentary-volcanic rocks and Late Paleozoic carbonate sediments overlain by Late Carboniferous flysch and olistostrome in the top. Two main stages (D1 and D2) of rock deformation in the lower part of the megaterrane associated with the Early Paleozoic accretion and two subsequent stages (D3 and D4) associated with the Late Paleozoic accretion and orogeny are described. Thrust processes D2 and D3 caused the formation of recumbent folds of different orientation and vergence. The normal antiform (D4) extending W–E is an orogenic fold. The Muruntau gold deposit is located in a regional synmetamorphic thrust zone called the Main Muruntau Thrust (MMT), which formed during the Early Paleozoic D2 stage. The MMT is responsible for the formation of secondary rock anisotropy along the cleavage of the D2 recumbent folds and conformal lens-like body of mineralized rocks and gently sloping veins with an area of 7.0 × 2.6 km. The internal structure of the deposit retains fragments of deformed gold quartz veins into recumbent folds. These structural data make it possible to link low-grade gold mineralized zones with Early Paleozoic deformations. We suggest that rock anisotropy within the MMT controlled mineralization twice: in the Early Paleozoic as a synmetamorphic flat high-permeable zone and in the Late Paleozoic as a relatively low-permeable zone for post-magmatic fluids.

Exhumation history and preservation of the Jiaojia giant gold deposit, Jiaodong Peninsula

Exhumation history and preservation of the Jiaojia giant gold deposit, Jiaodong Peninsula

Origin of the Dayingezhuang gold deposit in the Jiaodong district, eastern China: Insights from trace element character of pyrite and C-O-S isotope compositions

The Dayingezhuang gold deposit is a giant gold deposit in the Jiaodong district, with explored gold reserves of 283 t. After decades of research, sources of ore-forming fluids remain controversial, resulting in continuous controversy on the origin of this deposit. In this study, trace elements of pyrite and C-O-S isotopic data are presented to provide constraints on the ore-forming fluids of the Dayingezhuang gold deposit. Two types of gold-related pyrite were identified. Py1, hosted in quartz-pyrite veins, has subhedral to anhedral textures with developed micro-fissures. Py2, hosted in quartz-polymetallic sulfide veins, is generally subhedral to anhedral and intergrown with polymetallic sulfides. Both Py1 and Py2 are characterized by Co/Ni <1, which supports that the ore-forming fluids are metamorphic fluids with the addition of sedimentary materials. The calcite CO isotope suggests a mantle-derived source mixed with sediments. Combined with the anomalously high δ34S values, the ore-forming fluids that generated the Dayingezhuang gold deposits were most likely originated from the mantle lithosphere which is metasomatized and fertilized by the subducted Paleo-Pacific Plate and its overlying marine sediments. This model is similar to the common genesis of worldwide orogenic type gold deposits which suggests that the Dayingezhuang gold deposit may be of orogenic origin.

Study on three-dimensional enrichment regularities of Au, As, and S and their indicative significance in the giant Nibao gold deposit, Southwestern Guizhou, China

Study on three-dimensional enrichment regularities of Au, As, and S and their indicative significance in the giant Nibao gold deposit, Southwestern Guizhou, China

Comprehensive TsNIGRI work in the Lena gold-bearing area: from placer study to the Sukhoi Log potential assessment

The paper reviews to the systematic research of the Lena gold-bearing area by TsNIGRI (until 1957 NIGRIZoloto). The most important results of Lena expedition of this Institute (1938–1963) are presented. The role of crew members of the Lena field season in the early studies of the Sukhoi Log gold deposit conducted in cooperation with the Irkutsk Geological Department specialists is highlighted. TsNIGRI contribution to the further long-term study of the Sukhoi Log aimed at correct estimation of this giant gold deposit’sreserves is shown.

Geochemical studies of Sr-Nd-Pb-Hf isotopes on the Guojialing granite suite: Implications to region Au mineralization in the Jiaodong ore-cluster region

Based on the systematic elemental and isotope geochemical study on the Guojialing granite that is closely related to the gold mineralization in the Jiaodong ore-cluster region, further understandings have been made regarding its genetic mechanism, source material and gold mineralization conditions of the Guojialing granites. The (87Sr/86Sr)i values of Guojialing granite range from 0.7106 to 0.7120, and the εNd(t) from −18.1 to −13.2, respectively, which are similar to the initial SrNd isotopic compositions of those Late Jurassic-Early Cretaceous granites widely distributed in the Sulu orogenic belt, indicating similar sources of these intrusions in both Jiaodong and Su-Lu regions. The values of (206Pb/204Pb)i and(207Pb/204Pb)i of Guojialing granite are from 17.158–17.316, 15.453–15.478, respectively, indicating that the source of granites could be originated from mantle mixed with orogenic belt. The zircon Hf isotope of the Guojialing granite is decoupled from the Nd isotope of the whole rock, it has a zircon Hf model age(1979–3202 Ma) older than the full-rock Nd model age (1928 Ma). Compared to the full-rock Nd model age, the zircon Hf model age provides a more reliable age of crust-mantle differentiation and crust formation, suggesting that there is extensive crust deep-melting in the source area before the granitic magma activity, which was accompanied by strong Sm/Nd differentiation. Guojialing granite has similar characteristics to adakite, indicating that garnet is an important residual phase during magma formation. The formation of the Guojialing granite magma may be the partial melting of lithospheric mantle and thickened lower crust under eclogite facies, mixed with significant Neoarchaean crust or even Linglong granites when the magma upwelling. The Guojialing granite has high zircon Ce4+/Ce3+ ratios with the average values of 1151.7 and 811.4 respectively, indicating that the Guojialing granite was formed in a high oxygen fugacity environment, where sulfur is mainly present in the form of SO or SO2, which prevents the immiscibility of sulfides in the magma and avoids the removal of the sulfide metal elements. With crystallization differentiation, high oxygen fugitive magma will become a magma-hydrothermal fluid which is rich in sulfide metal elements, providing favorable material and environmental conditions for gold mineralization, thus favorably formed such giant gold deposit.

Gold endowment of the metasomatized lithospheric mantle for giant gold deposits: Insights from lamprophyre dykes

The metasomatized sub-continental lithospheric mantle (SCLM) is increasingly proposed to play a key control in the formation of giant gold (Au) deposits. However, the extent of Au enrichment in metasomatized SCLM and the Au contents of its derivative partial melts remain poorly constrained. Lamprophyres are derived from low-degree melting of metasomatic and fusible components in the SCLM, and could provide fundamental information about the metasomatized source and metal release compared to mantle peridotites and/or pyroxenites. The giant Jiaodong Au province (> 5000 tons, ∼ 120 Ma) in the eastern part of the North China Craton (NCC) is an ideal locality to assess the Au endowment of metasomatized SCLM which may serve as the source of Au, as indicated by the presence of mantle-dominated volatiles in auriferous fluids associated with the deposits. Based on detailed petrological studies, we analyzed Au, S, Cu and platinum-group element (PGE) contents of the SCLM-derived lamprophyres that are temporally (130–121 Ma) and spatially associated with the Jiaodong lode Au deposits. The lamprophyre dykes were emplaced in the deep crust and did not experience significant degassing and sulfide segregation, and the sulfide saturation occurred at a late stage during magma cooling, as demonstrated by sulfide petrography, S contents, Cu/S and Cu/Pd ratios of the lamprophyres. The relatively oxidized (ΔFMQ +1 – +2), hydrous (2–4 wt.% H2O) lamprophyres display variable and generally low Au contents (0.04–3.59 ng/g, mainly 1–3 ng/g, n = 31), as well as low PGE and Cu contents. Their high Au/Cu(N) and Au/Pd(N) ratios together with high Ba/Nb indicate a discernible Au addition to their source, resulting from multi-stage mantle metasomatism related to subduction. However, the average Au contents of the metasomatized SCLM before large-scale Au mineralization are heterogeneous and overall in a range of 0.5–1.5 ng/g. The values are higher than that of depleted SCLM (< 0.5 ng/g) but are still lower than or similar to the fertile upper mantle (1.2–1.7 ng/g). These results indicate that mantle metasomatism related to subduction replenished some amount of Au into previously depleted SCLM, leading to local or regional Au enrichment. However, such processes evidently did not result in remarkable Au enrichment of the mantle source beneath the eastern part of the NCC. We thus propose that the metasomatized SCLM and magmas derived from it, though without anomalously high Au contents, could still provide large amounts of Au for large-scale Au mineralization. Importantly, metasomatic volatiles from the metasomatized SCLM exert a key role, and they enable efficient release of Au from mantle sources, promote Au transportation along trans-lithospheric fault channels and subsequent enrichment and precipitation via magmatic-hydrothermal processes for giant Au deposits.

Genesis of the Longkou–Tudui gold deposit, Jiaodong Peninsula, eastern China: Constraints from zircon U-Pb dating, fluid inclusion studies and C–H–O–S stable isotopes

The Jiaodong Peninsula in eastern China hosts numerous large and giant gold deposits. Recently, a set of gold deposits distributed along the Guocheng Fault have been identified as a new gold mineralization type, of which the Longkou–Tudui gold deposit is spatially associated with the Muniushan monzogranite whereas its genesis is poorly constrained. A systematic study including zircon U-Pb dating, fluid inclusions, C–H–O–S stable isotopes was carried out in order to determine the genesis of the Longkou–Tudui gold deposit. Zircon dating results indicate that the Muniushan monzogranite and dioritic porphyrite were emplaced at 2089–2066 Ma (with a metamorphism probably occurring at 1860 ± 27 Ma, MSWD = 0.98) and 115.6 ± 1.4 Ma, respectively. Combined with cross-cutting relationships of the Muniushan monzogranite, dioritic porphyrite, and gold orebodies, it is inferred that the gold mineralization occurred in the early Cretaceous. Fluid inclusion study demonstrates a H2O–NaCl ± CO2 system, with a progressive decrease in average values of homogenization temperature and salinity from pre-ore to post-ore stages but a slight increase in bulk density. The ore-forming fluid is characterized by reductive, acidic, high to middle temperature, low salinity, and low density as revealed by a combined study on fluid inclusion and stable isotopes. H–O–C–S isotopic compositions indicate that the ore-forming materials have multiple sources including an inherited S source from the Jingshan Group, a mantle-derived C source, and a mixed H–O source induced by the addition of meteoric water. Compared with other Jiaodong gold deposits, the Longkou–Tudui deposit does not differ in mineralization age, nature and evolution of ore-forming fluid, and source of ore-forming materials except for orebody occurrence and heavier δ34S values inherited from the Jingshan Group, and this deposit was a byproduct of oceanic subduction of the Paleo Pacific Ocean.

Geology and geochronology of the Tokuzbay gold deposit in the Chinese Altai: A case study of collision-related orogenic gold deposits in Central Asian Orogenic Belt

Orogenic gold deposits are one of the most important gold deposits in the world. However, it is controversial that orogenic gold deposits are only generated at subduction-accretion or both in collisional setting. The Altai Orogen experienced a complex subduction accretion–collision history, including magmatism and metamorphism, and forming giant gold deposits. The Tokuzbay gold deposit consists of quartz vein ores and disseminated ores hosted in dikes. The ore bodies are controlled by secondary shear zone of the NW-, NNW-trending Ma’erkakuli Fault and occurred in meta-sediments, i.e., meta-sandstone and phyllite of Devonian Altai Formation, and diorite dikes and granite porphyritic dikes. Wall rock alteration is represented by silicification, pyritization, and muscovite alteration. The ores are restricted by ductile and brittle deformation in the shear zone. Large amounts of native gold and auriferous tellurium were precipitated during a transition from ductile to brittle regime. These characteristics indicate that the Tokuzbay gold deposit is an orogenic gold deposit in the Altai Orogen. The zircon LA-ICP-MS U-Pb ages of the ore-bearing granite porphyritic dikes and diorite dikes are 390 ± 2.5 Ma (MSWD = 0.87) and 378 ± 4 Ma (MSWD = 0.21), respectively, indicating that the magmatic rocks were emplaced during subduction of the Paleo Asian Ocean beneath Altai Orogen. Muscovite samples associated with gold from the auriferous quartz vein and disseminated ores hosted in diorite dikes returned Ar-Ar ages of 292.7 ± 1 Ma (MSWD = 1.3) and 293.9 ± 1.2 Ma (MSWD = 0.7), indicating that gold mineralization in quartz vein is synchronized with disseminated ores. The gold mineralization is restricted to the Early Permian and overlaps with the collision between Altai Orogen and Junggar Plate. The ore-hosting magmatic rocks related to subduction are more than 100 million years earlier than the ore-forming events. Combined with the regional tectonic evolution and the shear characteristics of the gold district, it is well proved that sinistral shearing trigged by the collision of Junggar Plate and Altai Orogen contributed to gold mineralization of the Tokuzbay deposit. Considering the Altai gold deposits in Kazakhstan, it is revealed that Permian collision between Junggar Plate and Altai Orogen triggered a large number of orogenic gold mineralization.

Sericite 40Ar/39Ar dating and S-Pb isotope composition of the Kanggur gold deposit: Implications for metallogenesis of late Paleozoic gold deposits in the Tianshan, central Asian Orogenic Belt

The Tianshan is one of the largest gold provinces on Earth and hosts several giant gold deposits, while most giant gold deposits are distributed in the western and central segments of the Tianshan (i.e., the Western Tianshan) but not in Chinese Tianshan. Thus, the differences for metallogenesis of gold deposits between the Western and Chinese Tianshan attract intensive interest but remain ambiguous. Here we present sericite 40Ar/39Ar ages and S–Pb isotope compositions of pyrite from the Kanggur gold deposit, the largest shear zone-related gold deposit in the Chinese Tianshan. By integrating new sericite 40Ar/39Ar plateau ages (262.71 ± 2.95 Ma and 263.40 ± 2.94 Ma) with previous geochronological results, three peaks in gold mineralization are identified for the entire Tianshan: an early peak at ca. 330 Ma during which time subduction–accretion-related porphyry-type and orogenic gold deposits formed, a middle peak at ca. 290 Ma during which time post-collisional magmatism-related orogenic gold deposits formed in a collisional compressional to post-collisional extensional environment, and a late peak at ca. 260 Ma during which time strike–slip shear zone-related orogenic gold deposits formed in a post-collisional extensional environment. The sulfur (δ34SV-CDT of −1.0 to +2.5‰ for pyrite from ores and −1.9 to +2.6‰ for pyrite from wall rocks) and lead (18.199–18.231 for 206Pb/204Pb, 15.585–15.624 for 207Pb/204Pb, 38.104–38.229 for 208Pb/204Pb for pyrite from ores, and 18.176–18.244 for 206Pb/204Pb, 15.583–15.611 for 207Pb/204Pb, 38.090–38.205 for 208Pb/204Pb for pyrite from wall rocks) isotope compositions of pyrite indicate that the metals in gold deposits throughout the Tianshan were sourced from different reservoirs. In the Western Tianshan, the ore-forming metals for the deposits southwest of longitude 70°E were mainly sourced from upper crustal reservoirs, whereas those east of longitude 70°E were mainly sourced from lower crustal reservoirs. In the Chinese Tianshan, however, the ore-forming metals were dominantly sourced from lower crustal and/or mantle reservoirs. These different reservoirs were likely responsible for the distinct characteristics of the gold deposits located in the Western and Chinese Tianshan.

Mesozoic Magma Underplating and its Role in the Formation of Jiaodong Giant Gold Deposits, Eastern China

Mesozoic Magma Underplating and its Role in the Formation of Jiaodong Giant Gold Deposits, Eastern China

Precambrian metamorphic crustal basement cannot provide much gold to form giant gold deposits in the Jiaodong Peninsula, China

The Jiaodong gold deposits, eastern China define a giant gold province in the Precambrian high-grade metamorphic crustal basement. Given the early metamorphism, the crustal basement would have been so depleted in gold that cannot be the main source for the later Mesozoic gold deposits. However, previously reported gold contents from crustal rocks were variably high (e.g., >5–10 ppb) and often interpreted to reflect the contribution of crustal basement. In this study, after careful field sampling, we obtained high-precision Au and S contents (with Cu and Ag for many samples) to solve the controversial issue. The Au contents were determined by internal standardization to platinum which was obtained from isotope dilution via high-sensitivity Element XR, and/or another independent method by GFAAS after polyurethane foam pretreatment. These methods achieved low procedural blanks (<0.02 ppb) and reliable analyses of low-Au samples. The analyzed metamorphic crustal rocks are from surface outcrops (n = 30) and crustal xenoliths (n = 10) in the Jiaobei terrane, where hosts the predominant Jiaodong gold resources (>85% of 5000 t). The Archean and Paleoproterozoic metamorphic outcrop rocks were sampled far from gold deposits and faults with the minimum effect of ore-forming fluids, and they display overall low Au contents (0.20 ± 0.18 ppb and 0.47 ± 0.29 ppb, respectively). More importantly, the crustal xenoliths trapped in pre-mineralization Guojialing granodiorites were not affected by hydrothermal overprint and better reflect the pristine features of the metamorphic basement. Although the crustal xenoliths contain variable sulfides with a wide range of Cu, Ag and S contents, they show rather low Au contents (0.18 ± 0.15 ppb). These results indicate the strong depletion of Au contents in the Precambrian crustal basement, consistent with the metamorphic devolatilization model. The Precambrian metamorphic crustal basement thus was rather difficult as the main gold source for the Jiaodong gold deposits, suggesting alternative sources.

The characteristic of microstructural deformation of gold bearing pyrite in Jiaodong: The links between nanoscale gold enrichment and crystal distortion

Auriferous pyrite can host a large proportion of gold resource at giant gold deposits all around the world so that these sulfides minerals become key factors to reveal the genesis of ore deposits. In this paper, the focused ion beam-scanning electron microscope (FIB-SEM) method were conducted to present the in-situ transmission electron microscopy (TEM) high resolution images for dislocation ultrastructure study in auriferous pyrite. The TEM diffraction images evidences were provided to prove the evidence that gold cluster at the nanoscale could be existed among crystal interface or even crystal lattice (0.22 nm ~ 0.54 nm). Finally, we have proposed a model that link these nanostructures with gold concentration, gold aggregate in pyrite. The model illustrates the formation pathway of the of discrete invisible gold in pyrite grains which were controlled by shape and ultrastructure of pyrite crystalline, with ion-by-ion rapid diffusion on the surface or lattice. It’s well interpreting for inhomogeneous distribution of nanogold in pyrite resulted from combining with many of these basic pyrite units. In addition, it also reveals unique in-situ measurement result about crystal-fluid interface dynamic that identify the various lattice spacing with possibility for nanoparticle incorporation into deformed pyrite. This study not only provides a new insight into the interpretation of gold distribution and aggregation in pyrite that has significant indication for gold deposit formation in the world, but also provides important evidences for geochemical exploration for concealed deposits based on nanoscale gold.

Gold in the lithosphere of the western South China Block, SW China: Insights from quartz porphyries from the giant Zhenyuan gold deposit

Numerous Au-rich deposits in the western South China Block, SW China, provide insights into the gold enrichment process at a lithospheric scale. Zhenyuan is a giant gold deposit in the western South China Block, but its genesis remains controversial with competing hypotheses of magmatic–hydrothermal and metamorphic–hydrothermal development. Here, we present new petrographic, major and trace element, and zircon U–Pb age data for quartz porphyry from the Zhenyuan deposit to evaluate the specific gold enrichment process. Zircon SHRIMP and LA–ICP–MS results demonstrate that the Zhenyuan quartz porphyries crystallized at ca. 255–247 Ma. This age is broadly consistent with the Re–Os age of gold-bearing pyrite measured in previous studies. The porphyries are characterized by high-K calc-alkaline compositions and exhibit significant enrichment in LILEs and LREEs, and strong depletion in HFSEs. They share the same source (Au-rich lower crust) with Cenozoic Au-bearing intrusions. The initial melts had a weak oxidation state (ΔFMQ = –0.15–0.55), which favored Au accumulation and migration. However, the gold was precipitated with the crystallization of Ti–Fe oxides in the middle crust, resulting in the emplacement of Au-poor magma in the upper crust. The gold orebodies in the Zhenyuan deposit formed due to Cenozoic hydrothermal processes, as evidenced by our observations of ore-bearing pyrite and Ar–Ar ages of phlogopite measured in previous studies. Combined with regional mineralization data, we propose lithosphere-scale processes for gold accumulation, migration, and precipitation from the Neoproterozoic to Cenozoic. Specifically, we predict an Au-rich middle crust beneath the western South China Block.

Metasomatized lithospheric mantle for Mesozoic giant gold deposits in the North China craton

Abstract The origin of giant lode gold deposits of Mesozoic age in the North China craton (NCC) is enigmatic because high-grade metamorphic ancient crust would be highly depleted in gold. Instead, lithospheric mantle beneath the crust is the likely source of the gold, which may have been anomalously enriched by metasomatic processes. However, the role of gold enrichment and metasomatism in the lithospheric mantle remains unclear. Here, we present comprehensive data on gold and platinum group element contents of mantle xenoliths (n = 28) and basalts (n = 47) representing the temporal evolution of the eastern NCC. The results indicate that extensive mantle metasomatism and hydration introduced some gold (&amp;lt;1–2 ppb) but did not lead to a gold-enriched mantle. However, volatile-rich basalts formed mainly from the metasomatized lithospheric mantle display noticeably elevated gold contents as compared to those from the asthenosphere. Combined with the significant inheritance of mantle-derived volatiles in auriferous fluids of ore bodies, the new data reveal that the mechanism for the formation of the lode gold deposits was related to the volatile-rich components that accumulated during metasomatism and facilitated the release of gold during extensional craton destruction and mantle melting. Gold-bearing, hydrous magmas ascended rapidly along translithospheric fault zones and evolved auriferous fluids to form the giant deposits in the crust.

Gold deposits of China: Resources, economics, environmental issues, and future perspectives

China ranks as the world's largest gold producer and as the second largest gold consumer since the last few years and hosts one of the fastest growing gold markets in the world. The gold mineralization in China has been divided into several super‐large (&gt;100 t Au), large (50 to 100 t Au), and numerous medium to small (20 to 50 and &lt;20 t Au) deposits. Geologically, these are classified into different types such as gold‐only deposits, base metal‐rich type including skarn, porphyry, and vein deposits, and placer accumulations. Integrated genetic models based on geological investigations propose that the gold deposits formed through multiple stages of subduction–accretion–collision associated with different orogenic cycles, with most of the giant gold deposits related to extensive lithospheric destruction and recycling. China has a long history of gold mining starting from the days of the Xia, Shang, and Zhou Dynasties at ca. 2,100–256 bc, which further flourished in the “Silk Road” era, although in the modern times, the country was “officially” reported producing hardly 2 tons of gold for nearly 40 years until a major revival occurred between 1982 and 1993, with a dramatic increase to 160 tons per year. According to recent statistics, China ranks as the world's largest producer of gold with over 460 tons, contributing significantly to the growth of world gold production. In the Asian region, 91% of gold production comes from China and five other countries, with China contributing the major share. With regard to gold consumption, the amount of gold bought in China rose steadily over the past several years from around 204.5 tons in 2002 to 832.18 tons in 2012. Among the various forms of gold jewellery in China, fine gold is the most popular, with 24 K gold accounting for more than 80% of the gold jewellery sold in the country. Studies identify a positive relationship between the rate of technical expertise and economic growth in state‐owned and mixed sectors of gold industry in China. Attracting more private investment into capital‐intensive and state‐owned sectors is considered to help boost the mining industry. China's gold output sustained the world gold market even during the global financial crisis in other bulk commodities. Quantitative analysis in recent studies reveals a power‐law cross‐correlation between price and volume in gold spot and futures markets and predicts long‐term stability despite short‐term fluctuations. Extensive mining activities invariably raise environmental issues and anthropogenic health hazards. With the country announcing the discovery of new gold deposits, such as the biggest ever gold mine in Shandong with gold resources valued more than $22 billion, and moving forward to new horizons in gold mining and production, insightful policies from decision makers are important in the areas of promoting research and development in academic and technical fields, involving technical expertise and advanced technology in gold mining and processing, and implementing strict regulations for environmental protection.

Geology, Geochemistry, and Geochronology of Gabbro from the Haoyaoerhudong Gold Deposit, Northern Margin of the North China Craton

The Haoyaoerhudong gabbro is a mafic intrusion located in the Haoyaoerhudong gold deposit, which is a giant gold deposit (148 t Au) hosted in Proterozoic strata on the northern margin of the North China Craton. In this paper, we present integrated SHRIMP U–Pb, geochemical and Sr–Nd isotopic data from gabbro of the Haoyaoerhudong gold deposit to reveal the magmatic processes behind its origin. SHRIMP zircon U–Pb dating constrains the timing of crystallization of the Haoyaoerhudong gabbro to 278.8 ± 0.81 Ma. Whole-rock geochemical results indicate that the Haoyaoerhudong gabbro has calc-alkaline features with enrichments of large-ion lithophile elements (LILE) and light rare-earth elements (REE) as well as depletions of high-field strength elements (HFSE). The relatively high (87Sr/86Sr)i (0.7053 to 0.7078) and low εNd(t) (−4.6 to −15.1) values of the gabbro indicate the involvement of crustal materials. Low Ce/Pb ratios (1.35 to 7.38), together with nearly constant La/Sm and Th/Yb ratios and variable Ba/Th and Sr/Nd ratios, suggest that the ancient mantle was modified by slab dehydration fluids. Based on new geochemical data and regional geological investigations, we propose that both the Haoyaoerhudong gold deposit and the Haoyaoerhudong gabbro formed in a post-orogenic extensional setting.