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The Yixingzhai gold deposit is a quartz‐vein–type deposit accompanied by skarn iron and porphyry molybdenum mineralization. There are four crypto‐explosive breccia pipes which provide an important ore‐controlling structure. Here we investigate the composition and compositional zoning of the native gold, garnet, and epidote in the Tietangdong skarn breccia pipe through detailed petrography, electron probe microanalysis, and elemental mapping. The native gold compositions show that they were formed in a relative higher temperature condition. Based on their composition and optical characteristics, the zoning in garnet can be divided into three types. The garnets of Generations 1 and 3 show high contents of spessartine (2.91–10.17 mol%) and grossular (20.94–54.71 mol%) and anomalous birefringence, indicating that they formed under relatively higher pressure and temperature and lower oxygen fugacity. The garnets of Generation 2 are mainly composed of andradite (75.70–99.98 mol%) and show compositional homogeneity, with formation under relative lower pressure and temperature and higher oxygen fugacity conditions. Magmatic‐hydrothermal pulses and multiple crypto‐explosions could be the main geological processes that caused the formation of the zoning textures. Zoning in epidote is more complex than that in garnet, and from core to the rim, the iron content shows an abrupt increase and aluminium content shows decrease. There is also decrease in iron and increase in aluminium in the inner part. These features might record multiple crypto‐explosion processes. Combining the complex replacement features of iron oxides and sulphides in the breccia pipe, we suggest that the Tietangdong breccia pipe formed through several crypto‐explosions. The fluid system in the breccia pipe activated during multiple crypto‐explosions, and oxygen fugacity varied greatly, which was disadvantageous to the accumulation and precipitation of ore‐forming elements. Crypto‐explosions destroyed the ore bodies formed during the early stage, resulting in their scattered distribution throughout the breccia pipe. Cone fractures formed eventually with the shrinking of the cooling breccia pipe after the magmatism ceased. Those fractures provided important ore‐hosting structures for the gold mineralization during the late stage. Our research indicates that there is high prospecting potential for porphyry Mo, Cu, and Au deposits in the deeper domains of the breccia pipes. [ABSTRACT FROM AUTHOR]

The Jiawula Ag–Pb–Zn deposit is located in the northern part of the Great Xing'an Range metallogenic belt within the eastern segment of the Central Asian Orogenic Belt. Here, we report results from muscovite 40Ar/39Ar geochronology and fluid inclusion study and formulate a vertical projection map of the ore grade in this deposit. The muscovite from the Jiawula deposit yields a plateau age of 133.27 ± 0.66 Ma and a 40Ar/39Ar isochron age of 131.88 ± 0.83 Ma. The muscovite 40Ar/39Ar data indicate a discrete second hydrothermal event postdating the mineralization, which we correlate with post‐collisional extension after the subduction direction of the Palaeo‐Pacific Plate changed. Low‐salinity aqueous fluid inclusions in quartz from the Jiawula deposit represent meteoric water or groundwater. Based on the fluid inclusion study, the fluids were trapped during cooling and decompression, which may have resulted in metal precipitation. We envisage that the copper precipitated from a high‐temperature fluid in the southern domain whereas lead, zinc, and silver precipitated at a lower temperature in the north. The spatial distribution of the ore‐forming elements, therefore, reflects the ore fluid migration‐cooling path from the south to north. [ABSTRACT FROM AUTHOR]

Mesozoic magmatism and lithospheric destruction in East China exerted significant control on gold metallogeny. Here, we investigate the mineralogy, geochemistry, geochronology, and isotopic systematics of the Dongyang gold deposit in southeast China to constrain its origin and geodynamics. This is a newly discovered epithermal gold deposit along the Circum–Pacific metallogenic belt and is characterized by intense silicification and sericitization. The C–H–O isotope data suggest deep magmatic sources of the ores and indicate that the ore‐forming fluids comprised a mixture of magmatic water and meteoric water. The S–Pb values of the pyrite indicate magmatic origin for the sulfur, and deposit was derived mostly from crustal sources, mixed with mantle materials. The Rb–Sr dating of the pyrite from the ore deposit shows an age of 164.2 ± 9.9 Ma, whereas the zircon U–Pb SHRIMP ages of the rhyolite porphyry is 160.9 ± 0.5 Ma, suggesting that the timing of mineralization is close to that of the crystallization of the dykes. In conjunction with previous studies on similar deposits, we suggest that the gold mineralization was the response of continental lithospheric thinning in southeast China triggered by the subduction of the Palaeo‐Pacific Ocean Plate. [ABSTRACT FROM AUTHOR]

Tellurium–gold deposits differ from normal gold mineralization in their significant content of tellurium‐bearing minerals with a close relation between Au and Te. The Guilaizhuang gold deposit is a major tellurium–gold deposit in the Shandong Province of China, and is located in the eastern margin of the North China Craton. The main sulfide minerals in this deposit are pyrite, As‐bearing pyrite, arsenopyrite, chalcopyrite, galena, sphalerite, chalcocite, and argentite. Tellurides contain native tellurium, altaite, coloradoite, petzite, and calaverite. Here, we investigate the fluid characteristics based on fluid inclusion studies and evaluate the intensive variables through thermodynamic computations to evaluate the ore genesis. We identify four stages for the mineralization: quartz‐pyrite stage, gold‐polymetallic sulfide stage, gold‐telluride stage, and carbonate stage. The gold‐telluride stage represents the main stage of gold precipitation. In gold‐polymetallic sulfide stage, Au formed within pyrite and As‐bearing pyrite in the form of invisible gold, whereas in the gold‐telluride stage, Au occurs as visible gold, such as native gold, electrum, calaverite, and petzite. Our data show that the mineralizing fluids were partly acidic and reduced during the gold‐polymetallic sulfide stage. Gold was transported as AuCl2− and Au(HS)2− complexes which was reduced by Fe2+. Gold might also occur as submicroscopic Au0 inclusions in pyrite and As‐bearing pyrite. The acidic state of the fluids favoured Au leaching from the surrounding rocks. During the gold‐telluride stage, gold might have migrated mostly as Au(HTe)2− and the Te combined at first with Ag to form hessite and subsequently with Au and Ag to form petzite and calaverite. With the decrease in Te content and increase in Au saturation, tellurium and native gold were precipitated. Our study provides insights into the physicochemical conditions of the formation of Te–Au deposits. [ABSTRACT FROM AUTHOR]

The Bagrote and Dainter valleys in Gilgit Baltistan Pakistan, belonging to the Kohistan island arc and southwestern domain of the Karakorum metamorphic complex, respectively, are a location of regional placer gold mining. However, no in situ hydrothermal gold deposits have been discovered in this region. Here, we report the textural, morphological, and geochemical characteristics of placer gold from the stream sediments of the Bagrote and Dainter valleys with a view to trace the provenance. The morphological features of the studied gold grains indicate proximal source mineralization. The gold grains display a microtexture typical of mechanical abrasion rather than chemical activity. Their chemical composition of most of the grains from each stream falls in a restricted range (minor alloying elements mainly Cu) with high fineness (1,000 Au/(Au + Ag)), suggesting derivation from a homogeneous source or limited number of mineralization types. The high Cu content of the gold grains from the Bagrote stream suggests that the gold here might be associated with previously undiscovered porphyry gold mineralization, whereas the Au–Ag–Hg alloys from the Dainter stream suggest a genetic linkage with undiscovered fault‐controlled auriferous veins of epithermal origin in the southwestern part of the Karakorum metamorphic complex. The chemical composition of both streams placer gold in triangular diagram in terms of Au–Ag–Cu shows all the gold grains from Dainter stream were derived from epithermal type of mineralization, and most of the plots of Bagrote stream fall on the domain of porphyry epithermal type of deposits which are also in consistent with a continental arc setting in the study area. The mechanically developed microtexture, homogeneous chemical composition in individual grains from core to rim, and absence of high fineness rims of the gold grains from both streams, suggest the absence of any supergene regrowth and direct transfer from the primary source through glacier to the fluvial system. The Gilgit Baltistan province, dominated by dry temperate climate and glacial environment having steep geomorphology, precluding any significant supergene processes such as silver leaching and addition of authigenic gold on detrital gold grains. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Diaoquan Ag-Cu deposit formed at about 130 Ma, during the peak stage of the destruction of NCC. • The metallogenic components were sourced from both mantle and crust. • The inner and deeper domains of the intrusions have good potential for future prospecting. Abstract The North China Craton (NCC) has been the focus of investigations on metallogeny in relation to craton destruction. The Diaoquan Ag-Cu polymetallic skarn mineralization is one of the large Ag deposits in central NCC. Here we present new mineralogical, geochronological and geochemical data from this deposit with the objective to gain an insight into the magmatic hydrothermal processes in relation to decratonization. The timing of polymetallic mineralization in this deposit is constrained as ca. 130 Ma by phlogopite Ar-Ar and molybdenite Re-Os dating. The physico-chemical conditions of the magmatic evolution estimated from amphibole, biotite, magnetite-ilmenite mineral thermobarometer indicate that the monzonite and porphyritic granite magma developed in a magma chamber at a palaeoburial depth of 2–3.3 km, and was subsequently emplaced at 1–2 km palaeodepth. The oxygen fugacity conditions were relatively high (>ΔNNO + 1.6 buffer) in the early stage and rapidly dropped (<ΔFMQ buffer). The major and trace element features suggest magma mixing as a possible mechanism that generated the different intrusions. Sr-Nd-Pb and zircon Hf isotope data indicate that lower crust is the major source of the magma and that part of metallogenic elements might have been sourced from mantle-derived components. We constructed the magmatic hydrothermal system as follows: (1) mafic magma formed by the partial melting of thinned mantle lithosphere; (2) the mafic magma underplating resulted in the partial melting of the lower crust, and generated granitic magma; (3) mixing of the mafic and felsic magmas generated the intermediate magma; (4) ore-forming fluids from the magma chamber migrated into the contact zone through fractures, resulting in Ag-Cu mineralization by skarnization; and (5) Mo-bearing fluid separated from the granite magma deposited the molybdenite in the inner contact zone. [ABSTRACT FROM AUTHOR]

The redox condition, a key parameter of mineralization, is one of the most difficult parameters to constrain precisely. Here we employ electron probe and X-ray photoelectron spectroscopy (XPS) to analyse sulphur (S) in apatite grains from five granitoid plutons that are differentially related to gold mineralization in the world-class gold fields of Jiaodong, Xiaoqinling, and Wutai-Hengshan within the North China Craton (NCC) to constrain the redox condition of melt. The results show increasing order of the apatite S content and S6+/ΣS ratios in the Linglong (only spatially close the Jiaodong gold deposits), Sunzhuang (related with the Yixingzhai gold deposits), Huashan (weakly related with the Xiaoqinling gold deposits), Wenyu (closely related with the Xiaoqinling gold deposits) and Guojialing plutons (closely related with the world-class Jiaodong gold deposits), indicating that the oxidation state increased from the Linglong pluton to the Guojialing pluton. The S concentrations of Guojialing, Wenyu, Huashan and Sunzhuang plutons, are estimated using previous methods are, 120–208 ppm, 107–138 ppm, 72–77 ppm and 10–74 ppm, respectively. Combined with the regional differences in gold mineralization in the North China Craton, the gradual increase in mineralization scale is consistent with the trend of increasing oxidation state in the granitoid plutons from Wutai-Hengshan to Xiaoqinling to Jiaodong goldfields, thus also underpinning the contribution of Mesozoic granites to gold mineralization in the North China Craton through providing the thermal energy and medium for the activation and migration of ore-forming fluids. [ABSTRACT FROM AUTHOR]

The widespread tectonic and magmatic events in Southeast China during the Mesozoic were accompanied by large‐scale metallogenesis. Here, we investigate the petrology, geochemistry, and zircon U–Pb age of the porphyry dykes in relation to the gold mineralization at Dongyang deposit in the Fujian Province. The geochemical data show silica‐rich and Mg‐ and Ca‐poor A‐type granite affinity for the dykes. The rocks have high concentrations of Light Rare Earth Elements (LREE) and Large Ion Lithophile Elements (LILE) and relatively low contents of Heavy Rare Earth Elements (HREE) and High Field Strength Element (HFSE). They display (La/Yb)N and (La/Sm)N values in the range of 5.7 to 31.4 and 6.0 to 8.3, respectively, with negative anomalies of Ba, Nb, Ta, Sr, Zr, Eu, and Ti and positive Ce anomaly. The source magma for the dykes was derived from a mixture of partially melted Al‐rich crustal material, with an input of mantle components. We present sensitive high‐resolution ion microprobe zircon U–Pb data from the dykes, which show emplacement ages in the range of 158 to 162 Ma, coinciding with the onset of the Yanshanian magmatism in Southeast China. Integrating the data obtained from studies on geology, geochronology and petro‐geochemistry, we suggest that the dykes played role in controlling the gold mineralization, and the magmatism and gold mineralization are the response of continental lithosphere thinning in Southeast China triggered by the subduction of the ancient Pacific Ocean Plate. [ABSTRACT FROM AUTHOR]

The Yongxin gold deposit is a large, fracture-controlled ore deposit in the Duobaoshan gold-copper metallogenic belt within the eastern domain of the Central Asian Orogenic Belt (CAOB). Silicification, sericitization and potassic alteration are the main hydrothermal alteration types which display successive zoning surrounding the ore-bodies. Pyrite, galena, sphalerite and chalcopyrite are the major metallic minerals in the deposit, and gold is mainly distributed in pyrite. Here we investigate the trace element composition and isotope (Pb and S) characteristics of pyrite from this deposit. The auriferous pyrite is mainly allotriomorphic and homogeneous in chemistry with a homogenous distribution of As, Ni, Mo and Fe from the core to rim of grains. These features are consistent with the 207 Pb/ 206 Pb- 206 Pb/ 204 Pb, and 208 Pb/ 204 Pb- 206 Pb/ 204 Pb of the grains that suggest a single source with no evidence for involvement of late fluids. The δ 34 S values range from +3.5‰ to +5.4‰ with an average of +4.48‰, suggesting a mantle-derived magmatic provenance for the sulfur. The high Co content and Co/Ni ratios, low Ni and Mo/Ni ratios suggest a mafic/ultramafic source for the Yongxin gold deposit. The Co-Ni-As relation indicates a magmatic hydrothermal affinity with a classification as epithermal gold deposit. High arsenic and gold contents on the rims of pyrite grains indicate that Au and As were simultaneously precipitated in anoxic, low temperature and near-surface conditions. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) is a window to decratonization and associated gold metallogenesis during the Mesozoic. Although Early Cretaceous gold mineralization associated with craton destruction has been reported, information on decratonic gold metallogenesis during the other periods remain scarce. Here we investigate the Guilaizhuang crypto-explosive breccia-type Te-Au deposit from eastern NCC and present Rb-Sr geochronological data on pyrite which provide new constraints on the timing of mineralization as 180.8 ± 2.3 Ma, corresponding to Jurassic gold metallogenesis. The S-Pb-C-O isotopic systematics and the ( 87 Sr/ 86 Sr) i value of the pyrite as ca. 0.712429 ± 0.000076 suggest that the ore-forming nutrients were derived from crustal and mantle sources. The Guilaizhuang Te-Au deposit formed during the tectonic transformation from compression to extension associated with the extensional collapse of the Dabie–Sulu UHP orogen and the delamination of the NCC lithosphere, triggering mantle upwelling and extensive crustal melting. [ABSTRACT FROM AUTHOR]

The Niujuan breccia-type silver deposit forms part of the North Hebei metallogenic belt along the northern margin of the North China Craton. The Hercynian Baiyingou coarse-grained granite and the Yanshanian Er’daogou fine-grained granite are the major Mesozoic intrusions exposed in this region. Here we investigate the salient characteristics of the mineralization and evaluate its genesis through zircon U-Pb and fluorite Sm-Nd age data, and Pb, S, O, H, He and Ar isotope data. The orebodies of the Niujuan silver deposit are hosted in breccias, which contain angular fragments of the Baiyingou and Er’daogou granitoids. The δ 34 S values of pyrite from the silver mineralized veins range from 2.4‰ to 5.3‰. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios of the sulfide minerals show ranges of 16.837–16.932, 15.420–15.501 and 37.599–37.950, respectively. The 3 He/ 4 He and 40 Ar/ 36 Ar ratios of the fluids trapped in pyrite are 0.921–4.81Ra and 299.34–303.84, respectively. The δ 18 O and δ 18 D w values of the ore-forming fluids range from 0.6‰ to −4.15‰ and from −119.4‰ to −98.7‰, respectively. Our isotopic data suggest that the ore-forming fluids were originally derived from the subvolcanic plutons and evolved into a mixture of magmatic and meteoric water during the main hydrothermal stage. The ore-forming materials were primarily derived from the lower crust with limited incorporation of mantle materials. The emplacement time of the Er’daogou granite is constrained by LA-ICP-MS zircon U-Pb geochronology at 145.5 ± 2.1 Ma. Five fluorite samples from the last hydrothermal stage yielded a Sm-Nd isochron age of 139.2 ± 3.8 Ma, indicating the upper age limit for the silver mineralization. These ages correlate with the formation of the Niujuan deposit in an extensional setting associated with the closure of the Mongol-Okhotsk Ocean and the subduction of the Paleo-Pacific oceanic plate beneath the North China Craton. [ABSTRACT FROM AUTHOR]

The Yixingzhai and Xinzhuang gold deposits are the most important gold mineralization of the Wutai-Hengshan region in the center of the North China Craton (NCC). Here we present new geological, mineralogical, geochemical and geochronological evidence from these deposits with a view to formulate a comprehensive model for the Mesozoic magmatism and metallogeny in the NCC. Our Re-Os dating of molybdenite from the Hewan granite porphyry constrains the timing of mineralization as 142 Ma. Gold mineralization occurred in the late stage of magmatism with close temporal and spatial relationships with the Sunzhuang pluton. Intensive parameters using amphibole, biotite, magnetite-ilmenite mineral thermobarometry and oxygen fugacity indicate that the parental magma for the Sunzhuang pluton evolved at high oxygen fugacity (>NNO + 2 buffer), and was emplaced at a depth of 2–2.6 km. The He-Ar isotopic composition of the fluid inclusions from pyrite grains in the Yixingzhai gold deposit suggests the involvement of mantle-derived fluids although the Pb isotope data shows that ancient lower crust is the major source. The major and trace element features, Sr-Nd-Pb and zircon Hf isotope data coupled with available geophysical information suggest that magmatism and mineralization in this region witnessed the interaction of mantle-derived mafic magmas with lower crust, with the latter as the major source. The magmatic and metallogenic processes involved the following: (1) partial melting and production of mafic magma triggered by upwelling asthenosphere; (2) mafic magma underplating under lower crust and partial melting of the ancient lower crust generated granitic magma; (3) formation of intermediate magma through the interaction between mafic and felsic magmas; (4) separation of ore-forming fluids from the Sunzhuang pluton and their migration through fault zones in the shallow crust generating the gold mineralization. [ABSTRACT FROM AUTHOR]

The Karakoram Block in North Pakistan formed during the late Permian-Triassic on the southern margin of Asian Plate with a topography characterized by glaciated high mountains. Several rivers and streams draining from these mountain peaks carry detritus with precious and base metals. However, the primary source deposits and their ore genesis remain unknown due to the rugged glaciated topography and inaccessibility for prospecting and in situ sampling. Here, we present a multi-parametric analytical approach including major and trace element characteristics, thermoelectric analysis, EPMA elemental mapping, XRD analysis, and sulfur and lead isotopic studies on the detrital auriferous pyrite from Shimshal Valley placer gold deposits in the Karakoram Block of the north Pakistan to gain insights into the ore genesis, provenance and current erosion or denudation rate of the source primary deposits found in the hinterlands of the Shimshal Valley. The pyrite with varying forms such as {100} + {111} + {210} followed by {210} + {111} and {100} + {210}, which are highly enriched in gold (up to 1700 ppm) as revealed through EPMA analysis. The low to moderate temperature estimated for their formation (100 to 360 °C), pyrite geochemical characteristics, geochemical discrimination diagrams (Fe/S-As, Fe + S-As, As-Co-Ni) and elements contents (Au, Ag, Cu) of the placer gold grains, as well as the high (58.2 %) and low (41.8 %) thermoelectric coefficients of N-type and P-type, suggest that the auriferous pyrite belong to the epithermal type of magmatic-hydrothermal systems. The XnP value (average −48.7 %), γ value (average 62.8 %) in conjunction with the n(S)/n(Fe) values of 1.97–2.11 of pyrite indicate that the placer gold deposits are derived from the middle-upper part of the ore body. The high Mo/Ni (average 5.4) and Co/Ni (average 2.7) ratio combined with detrital zircon U Pb geochronology, zircon fertility indicators such as Eu/Eu*, Ce/Nd, (Ce/Nd)/Y, Dy/Yb, (Eu/Eu*)/Y, texture and REE patterns correlate the ore mineralization with the Hunza Plutonic Unit emplaced on the catchment of the valley. The narrow variations in δ34S values, ranging from −5.3 to 3.8 ‰ with an average of −4.7 ‰, suggest that sulfur has a homogeneous magmatic source. The Pb isotopes values range 18.487 to 18.692, 15.713 to 15.745, and 38.964 to 39.416 for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, respectively. Our results suggest that metals for ore-forming fluid involved considerable contribution of crustal-derived materials. [Display omitted] • The studied placer gold deposits are sourced from epithermal type of deposits. • Proximal source with probable mineralization beneath the current level of erosion • Gold is found in pyrite as micro to nano inclusions as Au0 instead of Au+1. • Source deposits are associated with 109 MA plutons of Hunza Plutonic Unit. • Orogenic belts and crustal derived ore forming fluids are suggested. [ABSTRACT FROM AUTHOR]

Located in the eastern section of the Central Asian Orogenic Belt, the Jiawula Ag-Pb-Zn deposit is classified as a volcanic to subvolcanic related vein-type ore deposit. New U-Pb zircon geochronology, whole-rock geochemistry, mineral chemistry, and Sr-Nd isotope data are presented for the intrusions in the Jiawula deposit in order to evaluate the timing, petrogenetic type of the granitoid rocks, origin and evolution of magmatism, geodynamics, and to establish its relationship with lead-zinc mineralization. Zircon SHRIMP U-Pb analyses yield weighted mean ages of 150.1 ± 1.8 Ma for quartz porphyry, 148.8 ± 2.2 Ma for syenite porphyry, and 145.3 ± 1.9 Ma for monzonite porphyry, indicating a Late Jurassic (Yanshanian) magmatic event. An earlier magmatic event (Indosinian) occurred during the Late Permian to Early Triassic from ca. 254 Ma to ca. 247 Ma and is represented by granodiorite (254 ± 2 Ma), dacite porphyry (252.9 ± 4.8 Ma), and diorite porphyry (278 ± 4.1 Ma). Both the Indosinian and Yanshanian igneous rocks are classified as I-type granitoids. The late Jurassic intrusions are highly fractionated and characterized by negative anomalies of Eu, Sr, P, and Ti. The hypabyssal intrusions have initial 87 Sr/ 86 Sr values between 0.70458 and 0.70522, and ε Nd (t) values of −3.4 to −0.2, indicating relatively older crust in Jiawula among more juvenile crust in this area. Magma generation in Jiawula is linked to juvenile lower crustal and slightly enriched mantle sources. The ∼250 Ma magmatic episode in Jiawula might be related to the subduction of the Mongol-Okhotsk oceanic plate towards the south beneath the Erguna massif. The ∼150 Ma magmatic event occurred after the closure of the Mongol-Okhotsk Ocean followed by the change in subduction direction of the Paleo-Pacific plate. Varying temperature, stronger fractionation and higher oxygen fugacity related to the magmatic-hydrothermal transition caused Pb-Zn mineralization. [ABSTRACT FROM AUTHOR]

Jiaodong peninsula, located at the southeastern margin of the North China Craton, is well known for its rich endowment of super-large gold deposits. This region is also characterized by hundreds of intermediate – mafic dykes that cluster into several dyke swarms. In this study, we present zircon U-Pb ages which show that the timing of dyke emplacement as ca. 120 Ma, which followed the crystallization of the (quartz-) diorite porphyry at ca. 130 Ma. These ages coincide with the peak ages reported for magmatism and metallogeny in the central North China Craton. The various ages (2450–2570 and 154 Ma) from the inherited zircon crystals in these rocks suggest that substantial lower to middle crustal basement rocks and Jurassic granitoids were involved during dyke emplacement. The dyke swarms, varying between alkaline and subalkaline, are compositionally low-Si low-Ti lamprophyre and low-Si high-Ti dolerite porphyry in the western of the Jiaodong peninsula, whereas those in the eastern part are composed of both high-Si low-Ti and low-Si high-Ti lamprophyres. These features imply multiple sources for the dykes from convective asthenospheric mantle to ancient enriched lithospheric mantle with magma generation at different depths involving mixture of slab-derived hydrous fluids. The source magmas of the dykes were hydrous and enriched in volatiles as well as ore components, and their evolution occurred under high oxygen fugacity conditions. The relatively rapid emplacement and cooling of the dyke systems enabled the migration of fluids into ore-controlling faults or fractures. We envisage that the dyke swarms played an important role in generating the world-class gold mineralization of Jiaodong. [ABSTRACT FROM AUTHOR]

The Jiawula Ag–Pb–Zn deposit is located in the northern part of the Da Hinggan Mountains metallogenic belt in the eastern section of the Central Asian Orogenic Belt. Sphalerite, galena, pyrite, chalcopyrite, and arsenopyrite are the major sulfide minerals occurring in this deposit. Here we report results from electron probe micro-analysis (EPMA), thermoelectricity, and sulfur isotope studies of the constituent silver minerals and sulfide phases of the Jiawula deposit. Petrographic observations and EPMA study reveal abundant silver mineralization in the ore, especially within sphalerite and galena. Discrete grains of silver minerals (including argentite, pyrargyrite, and canfieldite) and isomorphism in silver-bearing sulfides are identified. Silver and tellurium contents in galena are relatively high and show interrelationship. Significant substitution of S by Te in the galena lattice facilitates silver entering the galena structure, which might have been promoted by relatively low lg f S 2 . The thermoelectric coefficient of pyrite shows a marked gradient from N-type to P-type from pre- to post-metallogenic stages. Pyrites in Jiawula are enriched in Co and As and in the absence of Ni, displaying features typical of epithermal deposits. The isotopic data present a close relationship between the sulfur source and magmatism. [ABSTRACT FROM AUTHOR]

The Fushan iron ores, located in the southern part of the Taihang Mountains (TM) within the Trans-North China Orogen, is among the medium-sized skarn iron deposits in China. In this paper we report U–Pb age data on zircon grains from the magmatic intrusion related with the skarn formation and from the Neoarchean metamorphic basement in the area. The results show that the dioritic intrusion which generated the skarn mineralization was emplaced at 128.8 ± 1.9 Ma. Zircon grains from the basement rocks and xenoliths, as well as inherited zircon in the dioritic intrusion show Neoarchean to Paleoproterozoic ages, corresponding to similar ages reported from elsewhere in the North China Craton. Our results and those from previous studies suggest that the continental lower crust was the major source of Mesozoic magmatism and associated ore mineralization. The Mesozoic magmatism and metallogeny in the Fushan region correlate with the peak of lithospheric destruction of the North China Craton. [ABSTRACT FROM AUTHOR]

The Early Cretaceous gold deposits of the Jiaodong Peninsula, eastern China, define China’s largest gold province with an overall endowment estimated more than 3000 t Au. The Wang’ershan gold deposit at the northern margin of the Jiaolai Basin in Jiaodong Peninsula of eastern China is located in the central-southern segment of the Wang’ershan fault zone. The major Mesozoic intrusions exposed in this region are the Linglong granite and the Guojialing granodiorite to the northeast of the deposit. Both these intrusions show high-K and alkaline signature. The Linglong granite displays peraluminous feature whereas the Guojialing granodiorite is metaluminous. Zircon U–Pb dating of the Linglong granite yields 206 Pb/ 238 U weighted mean age of 149.0 ± 1.3 Ma. The muscovite from the alteration zones associated with mineralization in the Linglong granite yields a plateau age of 130.35 ± 0.96 Ma, representing the initial phase of the hydrothermal activity. The δ 34 S values of pyrite from the gold mineralized veins range from 6‰ to 8.3‰ with the mean value of 7.66‰. The 3 He/ 4 He ratios of pyrite are in the range 1.58–2.71 Ra with a mean value at 2.168 Ra. The 40 Ar/ 36 Ar ratios show variation from 1220.3 to 1625.7 with an average of 1483.8. The δ 18 O values of the mineralizing fluids show a range of −2.13‰ to 7.5‰, with an average of 2.4‰. The δ 18 D w values are in the range of −97.5‰ to −61.4‰, with a mean at −82.6‰. Detailed elemental and isotopic data suggest that the hydrothermal fluids in early stage were mainly magmatic and derived from the Guojialing granodiorite, and the ore-forming fluids in the main ore-forming stages evolved into a mixture of magmatic and meteoric water. The ore-forming materials were primarily derived from crust, with minor input of mantle components. The ore-forming fluids might be related to the subduction of the paleo-Pacific slab beneath the North China Craton and the associated asthenosphere upwelling and consequent lithospheric thinning. [ABSTRACT FROM AUTHOR]

The Wutai-Hengshan region in the northwestern domain of Taihang Mountains (TM) occurs along the Trans-North China Orogen (TNCO) that amalgamates the Western and Eastern Blocks of the North China Craton (NCC). The metamorphic basement in the region is composed of ca. 2.5 Ga granite-greenstone belts within which the Mesozoic magmatic suites are widely emplaced, associated with polymetallic mineralization. The timing, origin and evolution of the magmatic rocks in the Wutai-Hengshan region provide important clues to evaluate the timing, mechanism and process of the destruction of the NCC. In this study, we report new zircon U–Pb and in-situ Hf isotopic data on some of the Mesozoic intrusions associated with Au–Ag–Cu–Mo mineralization from this region. The results show that magmatism and metallogeny in the Yixingzhai and Boqiang-Gengzhuang mining regions occurred during 142–130 Ma, starting with felsic granite porphyry with Mo–Cu mineralization, and intermediate magma associated with gold mineralization. The emplacement of magma and mineralization in Diaoquan mining region occurred about 132–130 Ma, with the intermediate magma emplaced earlier than felsic magma. The in-situ Hf isotopic data indicate that most of the felsic magma was produced by partial melting of the lower crust, and that the intermediate magma witnessed intrusion of mafic magma derived from mantle with magma mixing in different proportion. The process of crystallization differentiation played an important role in the formation of Diaoquan complex intrusion. The magmatism and metallogeny in the Wutai-Hengshan region were coeval with the craton destruction of the NCC. The Mesozoic magmatism and metallogeny in this region during 142–130 Ma contributed to the destruction of the stable cratonic architecture of the NCC. The mafic lower crust was modified by magma derived from mantle during this process. The regional geodynamics associated with these processes are correlated to the subduction of the paleo-Pacific oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The Han-Xing region is located in the south Taihang Mountains (TM) in the central part of the North China Craton, and is an important iron producing area. The iron deposits in this region are of skarn type, related to an Early Cretaceous high-Mg diorite complex, including gabbro diorite, hornblende diorite, diorite, diorite porphyrite, and monzonite. In this study we report the detailed mineral chemistry of the high-Mg diorites and skarn rocks. The olivine in the gabbro diorite shows chemical composition similar to that in mantle peridotite xenoliths. Clinopyroxene in the gabbro diorite is dominantly augite, with only minor diopside, whereas the clinopyroxenes in the diorite and monzonite are diopside. Amphiboles in the high-Mg diorites show compositional range from magnesiohornblende to magnesiohastingsite, with minor pargasite and tschermakite. Most plagioclase in the high-Mg diorite is andesine and oligoclase. The magnesio-biotite in gabbro diorites shows chemical characteristics of re-equilibrated primary biotites and those in calc-alkaline rocks. In the diorite and diorite porphyrite, plagioclase shows complex chemical zoning. Clinopyroxene and garnet in skarn rocks show varying FeO contents, the former containing low FeO (< 9 wt.%) and occurring as the major skarn mineral in large-scale iron deposits, and the latter within small-scale iron deposits with high FeO (mostly > 25 wt.%) content. We computed the pressure, temperature, oxygen fugacity and water contents based on the mineral chemistry of amphibole and biotite. Based on the results, the magma crystallization can be divided into two stages, one within the deep magma chamber, forming clinopyroxene, amphibole and plagioclase phenocrysts; the other after emplacement, forming the rim of phenocrysts and matrix minerals. The magma during the early stage shows high temperature (~ 900 °C–950 °C), pressure (~ 300 MPa–500 MPa), relatively high logfO 2 (NNO–NNO + 2), and H 2 O content in melt (4%–8%). During the late stage, the magma temperature dropped to about 750 °C, and pressure came down to less than 100 MPa, with the logfO 2 rising to NNO + 1–NNO + 2. The zoning of amphibole and plagioclase records the process of magma mixing and crystallization, with injection of mafic magma into the felsic magma chamber. The relatively high logfO 2 and H 2 O content inhibited partitioning of iron into mafic minerals and favored concentration of Fe in the melt. Iron ore precipitation occurred when the magma was emplaced at shallow level, and was principally controlled by the chemical composition of carbonate wall rocks. The high logfO 2 , Fe 3 + rich ore-forming fluid generated andradite and clinopyroxene when it reacted with limestone and dolomitic limestone respectively. [ABSTRACT FROM AUTHOR]

The Qiubudong silver deposit is a breccia-type silver deposit in the Fuping ore cluster region within the Taihang Mountain region of the central North China Craton (NCC). The cylindrical breccia pipe occurs at the conjunction of a NE trending fracture and a NW trending fracture and along the latter a number of quartz porphyry and felsite dikes are emplaced. The breccia clasts include quartz porphyry, leptite, and felsites, cemented mainly by felsic magmatic and hydrothermal components. The ore formation process can be divided into five stages: magnetite–quartz stage (I), biotite–quartz stage (II), quartz–pyrite stage (III), quartz-polymetallic sulfide stage (IV), and quartz–carbonate stage (V). Hydrothermal alteration is characterized by pyritization, sericitization, silicification, carbonatization, potash feldspathization, epidotization and chloritization with a systematic zoning from the ore body to the margin with transitional contact boundaries. We present S, Pb, He, and Ar isotope compositions of the ore minerals and evaluate the source of the ore-forming materials and fluids. The δ34S values of the pyrite range from 0.5‰ to 3.4‰, with an average of 1.6‰, consistent with a mantle input. The Pb isotope compositions from the sulfide minerals range from 15.799 to 16.049 for 206Pb/204Pb, 15.143 to 15.241 for 207Pb/204Pb, and 36.999 to 37.590 for 208Pb/204Pb, suggesting a lower crustal origin. Helium isotopic compositions of the fluid inclusions trapped in pyrite vary from 0.45Ra to 1.65Ra with an average of 0.98Ra (Ra is the 3He/4He ratio of air equal to 1.4×10−6), tending to crustal contribution with calculated mantle helium proportions ranging between 5% and 20% (average at 12%). Six pyrite samples from the silver deposit yield a Rb–Sr isochron age of 102.04±0.61Ma, whereas crystallization of the quartz porphyry dike is dated by zircon U–Pb LA-ICP-MS chronology at 107.95±0.87Ma. These ages suggest a close link between the silver mineralization and magmatism that generated the quartz porphyry. Combined with previous age data, we infer that the magmatism and metallogenesis in the central NCC took place during 140–100Ma with a duration of 40Ma, accompanied by mantle upwelling and lithospheric thinning. [ABSTRACT FROM AUTHOR]

Abstract: The Beiyingxigou quartz vein and alteration type Pb–Zn–Ag deposit forms part of the metallogenic region southwest of the Mapeng batholith in the Central North China Craton. The quartz vein-type polymetallic deposit is associated with intermediate-felsic intrusives emplaced with Mesoarchean metamorphic basement. The mineralization is dominantly controlled by N–S and NW–SE trending faults. We identify four distinct stages of mineralization associated with the hydrothermal activity: pyrite phyllic stage, quartz–pyrite stage, quartz–polymetallic sulfide stage, and quartz–carbonate stage. Among these, the first two stages and the quartz–polymetallic sulfide stage represent the early and main metallogenic stages, respectively. Here we present results from integrated stable isotope studies (S, Pb, He–Ar and H–O) to deduce the possible sources of the mineralizing fluids and metals. The δ34S values recorded in the sulfide minerals of the early and main metallogenic stages show ranges of +0.4‰ to +2.2‰, and −11.4‰ to −6.8‰, respectively. The data illustrate two distinct pulses of hydrothermal fluids with δ34S mean values of 1.1‰ and −8.7‰. The S isotopes of pyrite and galena, sphalerite from the early and main metallogenic stages suggest a mixed source from the Mesozoic magmatism and the Precambrian basement. We infer that the slow cooling magma at the main metallogenic stage led to a larger interaction with the country rocks and resultant contamination, as compared to the early–middle metallogenic stage. The lead isotopic composition of pyrite, galena and sphalerite from the early to main stages shows restricted ranges with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 15.720–16.275, 15.068–15.140 and 38.688–41.316, respectively. The data are all characterized by lower crustal nature, suggesting the contribution of Pb from both the Mesozoic intrusions and the basement rocks in the region. The 3He/4He and 40Ar/36Ar ratios of fluid inclusions from the Beiyinxigou Pb–Zn–Ag deposit show a range of 0.01–0.23 Ra and 270.2–298.1, respectively. The 4He and 40Ar concentrations vary from 26.6 to 340.6 (10−7 cm3 STP/g) and 165.6 to 357.9 (10−7 cm3 STP/g), respectively, suggesting dominantly crustal contribution. The δ18OQ values of quartz and the δ18Dw values show ranges of 10.9‰ to 13.6‰ and −85.2‰ to −57.8‰, respectively. The calculated δ18OW values of the mineralizing fluids show a range of 3.7‰ to 7.5‰. Our data suggest that the hydrothermal fluids were a mixture of both magmatic and meteoric water. The results presented in this study link the Beiyinxigou Pb–Zn–Ag deposit to metallogeny associated with Mesozoic magmatism in the North China Craton. [Copyright &y& Elsevier]

Abstract: The link between metallogeny and craton destruction in the North China Craton (NCC) remains poorly understood, particularly the mechanisms within the interior of the craton. In this overview, we summarize the major stages in the history of formation and evolution of the NCC, the spatio-temporal distribution and types of major ore species, as well as mantle contribution to the metallogeny, in an attempt to evaluate the geodynamic settings of metallogeny and the mechanisms of formation of the ore deposits. The early Precambrian history of the NCC witnessed the amalgamation of micro-blocks and construction of the fundamental tectonic architecture of the craton by 2.5Ga. The boundaries of these micro-blocks and the margins of the NCC remained as weak zones and were the principal locales along which inhomogeneous destruction of the craton occurred during later tectonothermal events. These zones record the formation of orogeny related gold, copper, iron and titanium during the early to middle Paleoproterozoic with ages ranging from 2.5 to 1.8Ma. The Early Ordovician kimberlite and diamond mineralization at ca. 480Ma, the Late Carboniferous and Early to middle Permian calc-alkaline, I-type granitoids and gold deposits of 324–300Ma, and the Triassic alkaline rocks and gold–silver-polymetallic deposits occurring along these zones and the margins of the blocks correlate with rising mantle plume, southward subduction of the Siberian plate and northward subduction of the Yangtze plate, respectively. The voluminous Jurassic granitoids and Cretaceous intrusives carrying gold, molybdenum, copper, lead and zinc deposits are also localized along the weak zones and block margins. The concentration of most of these deposits in the eastern part of the NCC invokes correlation with lithosphere thinning associated with the westward subduction of the Pacific plate. Although magmatism and mineralization have been recorded along the margins and few places within the interior of the NCC in the Jurassic, their peak occurred in the Cretaceous in the eastern part of the NCC, marking large scale destruction of the craton at this time. The junctions of the boundaries between the micro-continental blocks are characterized by extensive inhomogeneous thinning. We propose that these junctions are probably for future mineral exploration targeting in the NCC. [Copyright &y& Elsevier]

Abstract: Magmatism and associated metallogeny provide important constraints on geodynamic processes. The Hengshan terrain of northern Taihang Mountains located within the central North China Craton is well-known for several Mesozoic gold deposits. Here we investigate the Yixingzhai quartz vein-hosted gold deposit associated with the Sunzhuang quartz monzodiorite intrusive complex. We present U–Pb data on zircon grains from the monzodiorite which constrain the timing of emplacement of the pluton as ca.134Ma, coeval with the formation of Yixingzhai quartz vein gold deposit (at ca. 131Ma). The magmatism and metallogenesis during early Cretaceous in the Hengshan terrain are part of a major regional magmatic and metallogenic event in the Taihang Mountains and elsewhere in the North China Craton at ca. 130Ma ago. We characterize the zircon grains from the Sunzhuang quartz monzodiorite through morphology, internal structures and chemistry, and also present data from analyses of the chemistry (Co and Ni), and S–Pb–D–O isotopes of the minerals from the Yixingzhai gold deposit and Sunzhuang quartz monzodiorite. Our results reveal a lower crustal signature with mantle input for the source magma of the Sunzhuang Pluton. The magma was enriched in water and alkalis and shows a wide range of crystallization temperature (850–550°C, and mainly 650 to 700°C) under high oxygen fugacity. The ore minerals and the mineralizing fluids in the Yixingzhai gold deposit were derived from magma generated in the lower crust with additional input of mantle components. Our study links the gold metallogenesis with magmatism in the Hengshan terrain. Based on the new results reported in this study, and in conjunction with our interpretation of the ultra-broadband high-precision magnetotelluric sounding profile from the region, we suggest that the lithosphere beneath the Hengshan terrain was strongly thinned and decoupled between the crust and mantle in the early Cretaceous, and that the partly destructed lithosphere was largely preserved through the Cenozoic to present. The metallogenesis in the Hengshan terrain was closely related to the lithosphere thinning and crust–mantle decoupling in the North China Craton. [Copyright &y& Elsevier]

The Jilongshan skarn Cu-Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle-Lower Yangtze River valley metallogenic belt. The region is characterized by NW-, NNW- and EW-trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO2, K2O, and Na2O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al2O3)/[ n(CaO) + n(Na2O) + n(K2O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)N = 7.61-12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high-K calc-alkaline signature typical of intrusives associated with skarn and porphyry Cu-Au-Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) zircon U-Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle-Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re-Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle-crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Jinchang gold deposit is located in the easternmost portion of the Central Asian Orogenic Belt (CAOB), and represents one of the major gold districts in eastern Jilin–Heilongjiang provinces of China. The gold ore bodies are hosted mainly in altered Mesozoic granitoids, breccia pipes and ring and radial faults. Gold mineralization consists of alteration (stockwork in hydrothermally altered granites), breccia, and quartz-sulfide vein-types. Alteration assemblages around the alteration-style ore body show a vertical sequence of potassic, phyllic, and propylitic zones. In this study, we present U–Pb and Lu–Hf isotope data on zircons derived from mineralized granophyric granite, biotite monzogranite, granodiorite, and granite porphyry, and sericite Rb–Sr ages from the Jinchang gold deposit. The results show 206Pb/238U ages of 201±3Ma (MSWD=1.1), 203±4Ma (MSWD=1.4), 201±5Ma (MSWD=2.1), and 110±3Ma (MSWD=1.6), respectively. Sericite from the gold-mineralized phyllic-altered granodiorite and granite porphyry returns Rb–Sr isochron ages of 110±4Ma (MSWD=1.04) and 107±5Ma (MSWD=0.91), respectively. Our new data indicate that the gold mineralization at Jinchang took place at ca. 110Ma and was temporally related to intrusion of the granite porphyry. Zircon ε Hf (200Ma) values of the ca. 200Ma granites vary from −4.8 to +8.1, with TC DM model ages of 727–1535Ma, reflecting their derivation mainly by partial melting of juvenile Proterozoic crust. The gold-bearing 110Ma granite porphyry returns ε Hf (110Ma) values in the range of −1.6 to +9.8, with TC DM model ages of 542–1069Ma, suggesting partial melts of juvenile Proterozoic crust with notable input of mantle components as compared to the ca. 200Ma granites. Compiled oxygen (δ18OSMOW =−0.7–10.1) and hydrogen (δDSMOW =−99 to −70) stable isotopic values of quartz from ores indicate that the ore-forming fluids were predominantly exsolved from magmas with minor amount of meteoric water in quartz-sulfide veins at the late stage. The Hf isotope data from the granite porphyry, integrated with the results from previous data on S and Pb isotopic composition of ores, constrain the source of ore-forming components as lower crust with discernible mantle inputs and wall rock assimilation. Our results have implications bearing on the widespread magmatism and metallogenic event during the Early Cretaceous time in East China, and link them to mantle upwelling that contributed both heat and volatiles for crustal melting and scavenging of metals which in turn were concentrated in upper crustal levels through exsolution for the magmas. [ABSTRACT FROM AUTHOR]

Epidote is a major hydrous mineral in subducted mafic oceanic crust. Understanding its stability in the subduction zone environment is important for evaluating its role as a conveyor of water into the deep Earth. Here we report experimental results on epidote by simulating the high-pressure-temperature (P-T) conditions of the plate subduction environment. We used a diamond-anvil cell with an external resistance heating system, combined with in situ X-ray diffraction (XRD) and Raman spectroscopy techniques. Experiments at ambient pressure and high temperatures indicate that epidote starts to decompose at 1223 K and breaks down completely at 1373 K. In situ XRD analyses show no phase transition at temperatures up to 1272 K and pressures up to 14.0 GPa. Raman spectra indicate that epidote is stable at 1272 K and 14.0 GPa, but the energies of two Si-O bonds (v2,v5) and one M-O bond (v3) increase with increasing temperature. The cation H+ moves for a distance when the P-T is increased to 13.0 GPa and 1123 K. Based on the thermal structure of subducted slabs in typical hot and cold subduction zones, we infer that epidote can convey water downward into the mantle transition zone through subducted mafic oceanic crust. [ABSTRACT FROM AUTHOR]

The mineral zircon has a robust crystal structure, preserving a wealth of geological information through deep time. Traditionally, trace elements in magmatic and hydrothermal zircon have been employed to distinguish between different primary igneous or metallogenic growth fluids. However, classical approaches based on mineral geochemistry are not only time consuming but often ambiguous due to apparent compositional overlap for different growth environments. Here, we report a compilation of 11 004 zircon trace element measurements from 280 published articles, 7173 from crystals in igneous rocks, and 3831 from ore deposits. Geochemical variables include Hf, Th, U, Y, Ti, Nb, Ta, and the REEs. Igneous rock types include kimberlite, carbonatite, gabbro, basalt, andesite, diorite, granodiorite, dacite, granite, rhyolite, and pegmatite. Ore types include porphyry Cu-Au-Mo, skarntype polymetallic, intrusion-related Au, skarn-type Fe-Cu, and Nb-Ta deposits. We develop Decision Tree, XGBoost, and Random Forest algorithms with this zircon geochemical information to predict lithology or deposit type. The F1-score indicates that the Random Forest algorithm has the best predictive performance for the classification of both lithology and deposit type. The eight most important zircon elements from the igneous rock (Hf, Nb, Ta, Th, U, Eu, Ti, Lu) and ore deposit (Y, Eu, Hf, U, Ce, Ti, Th, Lu) classification models, yielded reliable F1-scores of 0.919 and 0.891, respectively. We present a web page portal (http://60.205.170.161:8001/) for the classifier and employ it to a case study of Archean igneous rocks in Western Australia and ore deposits in Southwest China. The machine learning classifier successfully determines the known primary lithology of the samples, demonstrating significant promise as a classification tool where host rock and ore deposit types are unknown. [ABSTRACT FROM AUTHOR]

The Early Cretaceous mafic dikes occur widely in the major gold districts of the eastern North China Craton (NCC), which are coeval and cospatial with many gold deposits, and these mantle-derived magmatic rocks provide a window to investigate the mantle compositions and metasomatism. Here, we present the Sr-Nd-Pb isotopic compositions of the Xiaoqinling mafic dikes and compare with regional geochemical and isotopic data for mafic dikes in Jiaodong, Xiaoqinling and interior of the NCC. The results indicate that the Early Cretaceous mafic dikes of Xiaoqinling and Jiaodong low-Ti group were derived from arc-like subcontinental lithospheric mantle (SCLM), that of Jiaodong high-Ti group were derived from OIB-like asthenospheric mantle, and that of the interior NCC were derived from both of lithospheric and asthenospheric mantle. Further, their mantle sources during Early Cretaceous were dominantly metasomatized by aqueous fluids derived from subduction slab as well as by limited melt and carbonate. Furthermore, the mantle beneath the Jiaodong low-Ti and Xiaoqinling is mainly characterized by EM2 type, whereas that of the interior NCC is mainly of EM1 type. Besides, the whole-rock Nd and zircon Hf isotopic compositions of these mafic dikes show clearly temporal and spatial variations with their ages of 145 ~ 110 Ma, reflecting that the mantle of the eastern NCC changed from the ancient IAB-like SCLM to juvenile OIB-like mantle through metasomatism. This process was controlled by the slab rollback of the paleo-Pacific plate during the extension. [ABSTRACT FROM AUTHOR]

• Porphyry and epithermal type of gold deposits in the hinterlands of the Bagrote valley. • Proximal source and high content of gold in pyrite suggest probable mineralization beneath the current level of erosion. • Gold occurs in pyrite in the form of micro to nano inclusions as Au0 instead of Au+1. • Ore forming fluids were derived from orogenic belts with minor contribution of lower crust. The Bagrote valley in North Pakistan, belonging to the Kohistan island arc, is well-known for regional placer gold mining. However, no economically feasible in situ hydrothermal gold deposits have been discovered in this region due to rugged terrain and remote nature of its location in the western Himalaya. The streams draining the Main Karakoram Thrust (MKT)/Shyoke suture zone carry placer gold in sediments as well as old river terraces, although the primary source remains unknown. In this paper, we employ a multiparametric approach including, X-ray Diffraction (XRD) analysis, thermoelectricity, major and trace element geochemistry and isotopic characteristics of pyrite associated with placer gold with a view to identify the nature of the unknown deposits and ore forming fluids on the catchment of the Bagrote valley. Pyrite in the Bagrote valley placers is euhedral to subhedral indicating the proximal gold sources. The high rate of occurrence of N-type thermoelectric coefficients (89%) with low P-type (11%) and crystallization temperature (290 °C−380 °C) combined with chemical features indicate that the pyrite was derived from porphyry or epithermal type of magmatic hydrothermal gold deposits from the hinterlands of the Bagrote valley. The X-Ray elemental maps show that Fe, As, Mo and Ni are homogenously distributed from core to rim suggesting stable crystallization condition without any alteration by later fluids. The calculated chemical formula of pyrite of our samples is [Au0.0006Fe] S2.004], plots of Au-As and Au-Fe shows that gold occurs in pyrite as micro to nano inclusion as Au0. The δ 34 S V - CDT values of pyrite range from – 0.6‰ to 0.9‰ with an average of −0.02‰, indicating the derivation of sulfur from a homogeneous magmatic source. The Pb isotope data indicates that the Pb was sourced from orogenic-type source, with minor contribution of lower crust. The narrow variations in 206Pb/204Pb and 208Pb/204Pb values suggest a single lead source. The low, medium and high Mo/Ni ratios reflect a mixed provenance for the auriferous pyrite. The average value of γ (71.8%), of pyrite computed from thermoelectric parameters (XnP), suggests that the dominant part of the primary source that contributes to the placers might have already been eroded. However, the proximal source and with high content of gold in the pyrite grains (up to 1160 ppm) suggest the possibility of significant economic mineralisation below the present erosion level of the deposits in the hinterlands of Bagrote Valley. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC), which underwent multiple subduction and lithospheric destruction during the Mesozoic, is well known for hosting some of the world-class gold deposits. In many cases, Mesozoic mafic dykes are associated with the gold deposits, although there has been no systematic studies aimed to integrate the characteristics of these dykes in different regions of the NCC. Here we investigate diabase and lamprophyre dyke suites in the Xiaoqinling region along the southern margin of the NCC, and compile the published geochronological, geochemical and isotopic data for regional mafic dykes and gold deposits from the major gold belts including Jiaodong, Xiaoqinling and central NCC. Zircon U-Pb data show the mafic dykes in Xiaoqinling were emplaced in two episodes at 219–227 Ma and 121–137 Ma, and their εHf(t) values (ranging from −2.1 to 3.8 and −13.6 to 1.6 respectively) suggest increasing input of lithospheric materials in the Early Cretaceous dykes. The compiled geochemical data on the mafic dykes from different regions in the NCC show that the magmatic evolution involved olivine and clinopyroxene fractional crystallization with limited crustal contamination and subduction-related fluid metasomatism. The geochemical and isotopic signature suggests multiple sources for the parent magma of the mafic dykes ranging from convective asthenospheric mantle to ancient lithospheric mantle, with the magma source characterized by enriched mantle (EM2 or EM2+ EM1), and that signatures might be potential for gold mineralization. Further, most dykes are coeval and cospatial with gold deposits in the NCC. The geochronological data show that small amount of both Mesozoic dykes and gold deposits formed in Triassic whereas the peak formed in Cretaceous following slab roll back of the Pacific plate subducting from the east during 145–110 Ma. We envisage that the tectonic extension associated with Pacific slab subduction contributed to the magmatism and gold mineralization in the NCC. [ABSTRACT FROM AUTHOR]

The Shihu quartz vein‐type gold deposit in the central North China Craton occurs within Neoarchean TTG (tonalite‐trondhjemite‐granodiorite) gneisses and shows spatial relationship with quartz diorite porphyry. The occurrence of the ore body is controlled by the N‐S fracture. Primary mineral assemblage of the ore body is composed of quartz, calcite, and base‐metal sulphides, including pyrite, galena, sphalerite, chalcopyrite, and pyrrhotite. Eight pyrite samples from veins of the main mineralization stage yield an isochron age of 129 ± 3 Ma (MSWD = 1.6), coinciding with the major Early Cretaceous magmatic event, and associated lithospheric thinning recognized in the NCC. The (87Sr/86Sr)i values of the pyrite (0.7102 ± 0.0006) are lower than the continental crust mean value (0.719) and higher than that of the mantle initial ratio (0.707), suggesting mixed crust–mantle source for the metallogenic components. Three types of hydrothermal pyrite from the early to major ore‐forming stages were identified in the quartz vein, including Py(I) as disseminated euhedral grains, Py (II) as dense bulks, and Py (III) as intergrowth with base‐metal sulphides. Electron microprobe analysis of the pyrite grains indicates a trend from S‐deficient to S‐enriched and from Fe‐enriched to Fe‐deficient stages, suggesting an increase in sulphur fugacity and reducing conditions. The arsenic in pyrite shows decrease against increasing Au during Stages II and III, implying that As is not the only trigger of gold precipitation, but electrochemical‐geochemical barrier played a major role in the formation of the ore. The Co and Ni concentrations, as well as Co/Ni ratios in pyrite, are relatively high, which provide an additional clue to the link with the regional magmatic event. Combined with the textural features, we propose a wider potential for gold exploration in this region, linking the mineralization with a major transitional tectonic regime. [ABSTRACT FROM AUTHOR]

The Shihu quartz vein‐type gold deposit, the largest gold deposit in the central North China Craton, occurs within wall rocks of Neoarchean TTG (tonalite–trondhjemite–granodiorite) gneiss and shows a close relationship with the early Cretaceous Mapeng granitoid pluton and various intermediate–mafic dykes. The occurrence, morphology, composition, and precipitation mechanism of the Au–Ag minerals are short of research, which is the purpose of this study. The primary mineral assemblage of orebody contains quartz, calcite, and base‐metal sulphides including pyrite, galena, sphalerite, chalcopyrite, and minor pyrrhotite and enargite. The Au–Ag minerals can be classified into three distinct types, namely, (a) quartz‐hosted, (b) pyrite‐hosted, and (c) base‐metal sulphidehosted, corresponding to formation sequence. Electron microprobe analysis indicates that these Au–Ag minerals show fineness (=Au/[Au + Ag] × 1,000) ranging from 976 to 366 with an average of 667 and are rich in Bi, Te, and Hg while deficient of Cu, As, and Se. Bismuth and tellurium in the Au–Ag minerals show a linear relationship with Au, whereas in the coexisted sulphides are almost below detection limits. We suggest that Bi and Te fundamentally influenced the transportation, enrichment, and precipitation of gold as scavengers to concentrate and deposit gold at the location with an "appropriate distance" from magma. Phase analyses of native bismuth and Bi–Te minerals included in pyrite, reported for the first time in Shihu Gold deposit, imply that the gold precipitation witnessed the ore‐forming fluid evolution with log fTe2 decreasing from approximately −11 to approximately −15 and log fS2 increasing from approximately −13 to more than −11. Mineralogical mapping with the fineness of Au–Ag minerals (fineness contours) suggest that the ore‐forming fluids came from the deep earth beneath the north of the mining area with excellent gold potential, which has been verified by later drilling. [ABSTRACT FROM AUTHOR]

The large‐scale concentration of Au associated with Mesozoic granitoid intrusions in the North China Craton (NCC) has inspired many investigations to explore the genetic relationship between the magmatism and gold metallogeny. The Xiaoqinling gold province is located in the southern margin of the North China Craton. The Wenyu and Huashan monzonitic granites formed at Early Cretaceous represent two of the important intrusions in this region, and a large number of gold deposits occur around the Wenyu pluton. Here we present results from an integrated study using in situ zircon U–Pb ages, trace elements, and Hf isotope to infer the composition and environmental changes during different evolution stages of the fertile Wenyu pluton and compare with the infertile Huashan pluton. The Huashan pluton was emplaced at 144.0 ± 0.6 Ma, whereas the fertile Wenyu pluton experienced multistage magmatic activity from 141.4 ± 0.6 to 129.6 ± 0.5 Ma. Temperatures computed from Ti‐in‐zircon thermometry indicate that the late‐stage Wenyu magma crystalized at 644°C, the Huashan magma, and early‐stage Wenyu magma crystalized at around 750°C. And the oxygen fugacity (Ce4+/Ce3+ > 200 and Eu/Eu* > 0.7) and the water content of the late‐stage Wenyu magma stay at higher levels. The U/Yb–Hf and U/Yb–Y relationship with εHf(t) (−15.63 to −17.89) of the late‐stage Wenyu magma suggest that the ancient lower crust with subsequent inputted basaltic components make up the source of the fertile and infertile plutons. Combined with previous geochronological data and geodynamics studies, we propose that the late‐stage intrusion of the Wenyu pluton experienced intensive magma mixing. And the formation of Wenyu pluton created conducive heat energy, oxygen fugacity, and water conditions for the formation of high‐grade gold deposits. [ABSTRACT FROM AUTHOR]

The Chen'er gold deposit hosted in the Precambrian Taihua Supergroup metamorphic rocks is one of the typical gold deposits in the Xiaoqinling region along the southern margin of the North China Craton. The metallic mineral assemblage in this deposit includes sulfides, tellurides, native gold, electrum, and native bismuth. The telluride minerals are composed of calaverite, petzite, hessite, altaite, joseite; except for hessite and matildite, the other tellurides and native bismuth are first reported in this study. Fluid inclusion studies in the auriferous quartz reveal three types: aqueous, aqueous–carbonic, and carbonic inclusions. The homogenization temperatures range from 184 to 364°C, and salinities are in the range of 1.74‐ to 11.47‐wt.% NaCl equiv. At temperatures of 275°C, the logfTe2 and logfS2 of the fluid are estimated as −16.13 to −8.19 and −12.74 to −4.80, respectively, and at temperatures of 305°C, the pH and logfO2 of the fluid are estimated as 3.61 to 5.69 and −34.31 to −27.81, respectively. It is inferred that Au(HS)2− and Au(HS)0 are the predominant gold‐bearing complexes, and tellurium was transported as Te22−. Based on thermodynamic models of logfO2(g) versus pH, we suggest that the precipitations of native gold and electrum in the early and main mineralization stages are different, with the oxygen and hydrogen isotope values of auriferous quartz suggesting mixing of magmatic water with meteoric water. [ABSTRACT FROM AUTHOR]

Quartz cathodoluminescence (CL) images are commonly combined with trace element concentrations to decipher complex histories of hydrothermal systems. However, the correlations between aluminum content and CL zoning of low-temperature hydrothermal quartz and their genesis remain controversial. In this contribution, a multiparametric study was carried out on CL-aluminum zoning of low-temperature hydrothermal quartz (<350 °C) from the Shihu and Rushan quartz-vein type Au deposits in the North China Craton. The results show that aluminum concentration correlates negatively with CL intensity in quartz from the Shihu Au deposit. CL-dark quartz zoning has significant Al concentrations as well as detectable Al-H bonds. However, in the Rushan Au deposit, the correlation is positive, and aluminum is enriched in the CL-bright quartz zoning. The Al content is positively correlated with K content with r2 = 0.769. Combined with the electron backscatter diffraction (EBSD), X-ray single crystal diffraction (XRD), and transmission electron microscope (TEM) data, we infer that the genesis of CL zoning in the low-temperature hydrothermal quartz is closely related to Al3+-H+ and Al3+-K+ concentrations. The Al3+-K+ may act as the CL-activator, while the Al3+-H+ may act as the CL-dampener. Where Al3+-Si4+ substitution is charge balanced by hydrogen, the intensity of CL response decreases; where Al3+-Si4+ substitution is charge balanced by potassium, the intensity of CL response increases. The correlations between CL intensity and aluminum concentration in the low-temperature hydrothermal quartz reflect pH fluctuations of hydrothermal system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The isotope values and of pyrite indicate that oxygen fugacity increased slightly from stage Ⅱ to stage III. • The Rb-Sr dating on sulfide minerals from Chen'er yield an isochron age of 129.2 ± 3.4 Ma. • The metallogenic components and fluids were derived dominantly from magmatic or mantle sources. The Chen'er gold deposit, with 27 tons of known Au reserves, is one of the typical gold deposits in the Xiaoqinling district along the southern part of the North China Craton. In order to better understand the gold precipitation time and mineralization process, we report in-situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) trace element analyses, elemental maps, and the Rb-Sr and S-Pb isotopic composition of sulfides from the Chen'er gold deposit with a view to gain insights into the mineralization time and process. Trace element analyses and elemental maps of pyrite show that the content of As is low and has no correlation with Au, indicating As is unlikely to have controlled the Au incorporation into pyrite. Gold mainly occurs as solid solutions in the Py Ⅰ and Py Ⅱ, and as Au-Ag and/or Au-Te sub-micrometer inclusions in Py III. The Rb-Sr isotopic data on sulfides from the Chen'er deposit yielded an isochron age of 129.2 ± 3.4 Ma, which overlaps with the previously reported 40Ar/39Ar age of hydrothermal mica, indicating that the gold mineralization occurred in the Early Cretaceous. The in-situ sulfur isotope values of sulfides from stage Ⅱ to stage III fluctuate significantly (the average value decreases from 4.95 to −0.24‰) and were affected by physicochemical parameters of the mineralization process, especially ƒO 2. In addition, the δ34S values are in a narrow range (-1.34 to 5.24‰), indicating a magmatic source for the sulfur. In-situ Pb isotopic compositions of the pyrite and galena of stage Ⅱ and stage III are relatively constant with 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb values in the range of 37.264–37.595, 15.364–15.423, 16.992–17.078, respectively, indicating a mixed mantle-crust origin. Based on the new geochronological, geochemical and isotopic data presented in this study, and combined with those from previous studies, we suggest that the lode gold deposits in the Xiaoqinling district are magmatic hydrothermal ore deposits, with metal and ore-forming fluid originating primarily from the mantle, coupled with the cratonic reactivation during the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Trans-North China Orogen (TNCO), a Paleoproterozoic suture that amalgamates the Western and Eastern Blocks of the North China Craton (NCC), witnessed extensive magmatism and metallogeny during Mesozoic, associated with intraplate tectonics and differential destruction of the cratonic lithosphere. Here we investigate a suite of porphyry dykes surrounding the Mapeng batholith in the Fuping Complex within the TNCO in relation to the Mesozoic gold and molybdenum mineralization. The major element chemistry of these dykes show a range of SiO 2 (57.92 to 69.47 wt.%), Na 2 O (3.20 to 4.77 wt.%), K 2 O (3.12 to 4.60 wt.%) and MgO (0.51 to 3.67 wt.%), together with high concentration of LREE and LILE, and relatively low contents of HREE and HFSE. The rocks display (La/Yb) N = 13.53–48.11, negative Nb, Ta, Th, U and Zr anomalies, and distinctly positive Ba, K and Sm anomalies. The mineralogy and geochemistry of the porphyry dykes indicate the rocks to be high-K calc-alkaline, and I-type, with adakitic features similar to those of the adjacent Mapeng batholith. The source magma for these rocks was derived from a mixture of reworked ancient continent crust and juvenile mantle materials. The zircon U–Pb data from these rocks show ages in the range of 124 to 129 Ma, broadly coinciding with the emplacement age of the Mapeng intrusion. The inherited zircons of ca. 2.5, 2.0 and 1.8 Ga in the dykes represent capture from the basement rocks during melting. The zircon Lu–Hf isotopic compositions show negative ε Hf ( t ) values varying from − 27.8 to − 11.3, with Hf depleted model ages ( t DM ) ranging from 1228 Ma to 1918 Ma and Hf crustal model ages ( t DM C ) of 1905 Ma to 2938 Ma, suggesting that the Mesozoic magmatism and associated metallogeny involved substantial recycling of ancient basement rocks of the NCC. We present an integrated model to evaluate the genesis of the porphyry systems and their relation to mineralization. We envisage that these dykes probably acted as stoppers (impermeable barriers) that prevented the leakage and run-off of the ore-bearing fluids, and played a key role in concentrating the gold and molybdenum mineralization. [ABSTRACT FROM AUTHOR]

The Jiaodong type comprises a unique class of gold mineralisation which includes the Linglong type quartz-vein hosted and the Jiaojia type fracture-disseminated style deposits. Although the type area is in the Jiaodong Peninsula in NE China, where some of the world's richest gold reserves occur, we identify similar occurrences in other parts of China and elsewhere in the world under this category. The ore fluids migrated upwards forming quartz vein type of gold ore (Linglong type) wherever the ore-controlling fractures are at high angles. Fluid infiltration into the surrounding wall rocks and generation of the Jiaojia type disseminated style deposits resulted where the ore-bearing fluids encountered low angle fractures. On a regional scale, the Jiaodong type gold mineralisation occurs along the margins of reactivated cratons, within the interior of cratons along paleosuture zones, or along the junctions of micro-blocks, and is distinctly different from the classic orogenic gold in terms of their tectonic setting, ore characteristics and genetic history. Unlike skarn and porphyry type of deposits, the Jiaodong type gold deposits do not always show close spatial relationship with magmatic intrusives and some of the deposits occur distal to plutons (> 10 km). In this paper, we evaluate the salient geological, geochronological, geochemical and isotopic features of the Jiaodong type gold deposits and propose some general guidelines for gold prospecting. Based on case studies, we predict that the gold lodes in the Jiaodong type mineralised zones might extent vertically up to 3000 m with only minor mineralogical and geochemical variations. [ABSTRACT FROM AUTHOR]

Silicate perovskites ((Mg, Fe)SiO3 and CaSiO3) are believed to be the major constituent minerals in the lower mantle. The phase relation, solid solution, spin state of iron and water solubility related to the lower mantle perovskite are of great effect on the geodynamics of the Earth's interior and on ore mineralization. Previous studies indicate that a large amount of iron coupled with aluminum can incorporate into magnesium perovskite, but this is discordant with the disproportionation of (Mg,Fe)SiO3 perovskite into iron-free MgSiO3 perovskite and hexagonal phase (Mg0.6Fe0.4)SiO3 in the Earth's lower mantle. MnSiO3 is the first chemical component confirmed to form wide range solid solution with CaSiO3 perovskite and complete solid solution with MgSiO3 perovskite at the P-T conditions in the lower mantle, and addition of MnSiO3 will strongly affects the mutual solubility between MgSiO3 and CaSiO3. The spin state of iron is deeply depends on the site occupation of the Fe3+ or Fe2+, the synthesis and the annealing conditions of the sample. It seems that the spin state of Fe2+ in the lower mantle perovskite can be settled as high spin, however, the existence of intermediate spin or low spin state of Fe2+ in perovskite has not been clarified. Moreover, different results have also been reported for the spin state of Fe3+ in perovskite. The water solubility of the lower mantle perovskite is related with its composition. In pure MgSiO3 perovskite, only less than 500 ppm water was reported. Al-MgSiO3 perovskite or Al-Fe-MgSiO3 perovskite in the lower mantle accommodates water of 1100 to 1800 ppm. Further experiments are necessary to clarify the detailed conditions for perovskite solid solution, to reliably analyze the valence and spin states of iron in the coexisting iron-bearing phases, and to compare the water solubility of different phases at different layers for deeply understanding the geodynamics of the Earth's interior and ore mineralization. [ABSTRACT FROM AUTHOR]

The Trans-North China Orogen (TNCO) along the central part of the North China Craton (NCC) is considered as a Paleoproterozoic suture along which the Eastern and Western Blocks of the NCC were amalgamated. Here we investigate the Precambrian crustal evolution history in the Fuping segment of the TNCO and the subsequent reactivation associated with extensive craton destruction during Mesozoic. We present zircon LA-ICP-MS U–Pb and Lu–Hf data on TTG (tonalite–trondhjemite–granodiorite) gneiss, felsic orthogneiss, amphibolite and granite from the Paleoproterozoic suite which show magmatic ages in the range of 2450–1900 Ma suggesting a long-lived convergent margin. The ε Hf ( t ) values of these zircons range from −11.9 to 12 and their model ages suggest magma derivation from both juvenile components and reworked Archean crust. The Mesozoic magmatic units in the Fuping area includes granite, diorite and mafic microgranular enclaves, the zircons from which define a tight range of 120–130 Ma ages suggesting a prominent Early Cretaceous magmatic event. However, the ε Hf ( t ) values of these zircons show wide a range from −30.3 to 0.2, indicating that the magmatic activity involved extensive rejuvenation of the older continental crust. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zircon U-Pb ages of 101–148 Ma reflecting prolonged hydrothermal alteration. • Three groups of hydrothermal zircons are recognized from decratonic gold deposits. • Ore-forming fluid of decratonic gold deposits is relatively oxidized than those of orogenic and porphyry gold deposits. Decratonic gold deposits constitute the most important type of gold endowment in the North China Craton (NCC), although the nature and evolution of ore-related fluids in these deposits remain controversial. Here we investigate geochemistry of hydrothermal zircon grains from the Dahu gold deposit in the Xiaoqinling region in the southern margin of the NCC. We also compile the published information on trace elements in hydrothermal zircon from deposits in the other major gold districts of the NCC. The zircon U-Pb data show ages in the range of 101–148 Ma reflecting prolonged hydrothermal alteration that occurred within an extensional tectonic setting. Based on the trace elements, three distinct groups of hydrothermal zircons are recognized. Group 1 shows low La contents (<1 ppm), high Ce/Ce* (>10), and steep positive LREE patterns ((Sm/La) N > 20); Group 2 possesses high La contents (<10 ppm), low Ce/Ce* (<10), and weak positive LREE patterns ((Sm/La) N < 20); Group 3 displays ultra-high La contents (>10 ppm), low Ce/Ce* (<10), and flat LREE patterns ((Sm/La) N < 20). This classification is also applicable to orogenic and porphyry gold deposits. Group 1 grains initially crystallized from magma and underwent subsequent modification by post-magmatic fluids, whereas Group 2 and Group 3 directly crystallized and regrew from zirconium-saturated aqueous fluids. The La-enriched signature in hydrothermal zircons may mainly originate from undetected REE-bearing phases within zircon that formed during the hydrothermal alteration events. The fluid flow has a significant effect on the redox state of gold metallogenic system. The hydrothermal zircons from decratonic gold deposits display higher Ce/Ce* ratios (1–258) and Ce/Nd ratios (0.7–32.2) than those from orogenic and porphyry gold deposits, indicating that the zircon grains formed from a relatively oxidized fluid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apatite from both the Huashan and Wenyu plutons are fluorapatite of magmaticorigin. • Wenyu apatite formed under a higher oxidation state and incorporated more mantle-derived materials than Huashan apatite. • Wenyu apatite crystallized earlier than feldspar and Huashan apatite was affected byfeldsparcrystallization. • The magma of the Wenyu pluton incorporated more intensive fluid exsolution during crystallization. • Wenyu pluton is more favorable to gold mineralization than the Huashan pluton. The relationship between granitic magmatism and lode gold mineralization has remained as a controversial topic among economic geologists. In this paper, we report in situ elemental and Sr isotopic signature of apatite from the Wenyu and Huashan granitic plutons in the Xiaoqinling goldfield, southern margin of the North China Craton (NCC), intending to provide further constrain the relationship between magmatism and metallogeny. The formation ages of Huashan and Wenyu granitic plutons are coeval with the gold mineralization, but most of the gold deposits are clustered nearing the Wenyu pluton, and only a few small gold deposits are found adjacent to the Huashan pluton. Although apatite from both plutons is all fluorapatite, characterized by negative Eu anomaly and enrichment of LREEs, the apatite from the two plutons shows different signatures. Based on these differences, the apatite from the Huashan pluton is divided as group A (HS-A) and group B (HS-B). The δEu, δCe values and MnO and Ga contents of the Wenyu and HS-A apatite indicate high oxygen fugacity range from MH to NNO for the magma, whereas the HS-B apatite shows low oxygen fugacity range from NNO to FMQ. The 87Sr/86Sr, REE, Th/U, and Ce/Y values of the apatite suggest that the magma for the Wenyu pluton incorporated more mantle-derived materials in contrast to Huashan pluton. Sr/Y ratio and REE content of the apatite indicate that WY apatite crystallized earlier than feldspar and Huashan apatite was affected by feldspar crystallization. The fluid-volatiles exsolution texture and S content of the apatite indicate higher content of volatiles in the Wenyu pluton magma, where the magma experienced more intense fluid exsolution than that of the Huashan pluton during apatite crystallization. The characteristics of many mantle-derived materials, high oxygen fugacity, and higher volatiles as revealed by the apatite data show that the magmatism of Wenyu pluton was more conducive to the mineralization of gold deposits than that of the Huashan pluton and is more closely related to gold deposits. [ABSTRACT FROM AUTHOR]

The Luxi area in the central part of Eastern North China Craton (NCC) is located in a relatively stable intraplate environment and preserves some of the large granite–greenstone belts in the North China Craton (NCC). The intensity and extent of multiple magmatic pluses associated with the destruction of the NCC during Mesozoic were comparatively less in this region. However, the nature and timing of the magmatic pulses in the Luxi area are critical to the evaluation of the differential destruction of the NCC's lithosphere as well as in understanding the origin and extent of the associated gold mineralization. In this study, we report new zircon U−Pb data on the basement rocks in the Luxi area which show that the protoliths of the TTG (tonalite–trondhjemite–granodiorite) gneisses, granitoids and amphibolites formed at 2572.2±8.8Ma, 2531±12Ma, and 2572±32Ma respectively. The Luxi area experienced two major crust accretions at 2.7−2.75Ga and ca. 2.5Ga. The Mesozoic Tongshi complex formed at 175.6±1.7−178.4±2.1Ma associated with fluid modification at the later stage of magma crystallization. The alteration age (162.2±3.2−165.4±2.8Ma) may represent the mineralization age of the Guilaizhuang gold deposit. The diorite porphyry of Tongjing complex was emplaced at 128.0±5.4Ma. The inherited zircon and Lu−Hf isotope data suggest extensive recycling of basement rocks in the Luxi area. The sequence of Mesozoic magmatic intrusions shows a clear variation from intermediate (alkaline) through intermediate (cal-alkaline), and felsic–mafic, and the main intrusive ages can be divided into distinct phases at 170–200Ma, 100–150Ma (with peak at 120–130Ma), and 80–90Ma respectively. The Tongshi complex formed during the compression–extension stage after the collision of the Yangtze Craton and North China Craton, whereas the Tongjing complex and other alkaline, felsic and mafic complexes in the Luxi area formed within the geodynamic setting of Pacific subduction. The early Cretaceous magmatism also simultaneously occurred in the Taihang Mountain area (far from the plate margin) in the central part of the North China Craton, with related gold mineralization. The Mesozoic gold mineralization in Jiaodong and Luxi in the eastern, and those in the central parts of the North China Craton appear to be linked to extensive crustal recycling in an extensional tectonic regime. [ABSTRACT FROM AUTHOR]

The Yinan gold deposit in the Luxi area of Shandong Province in northeastern China is a skarn-type ore deposit. In this article, we present results from sulphur, lead, carbon–oxygen, and helium–argon isotope chemistry to characterize the ore genesis and source features. We also present rhenium–osmium ages from molybdenite to evaluate the timing of ore formation. The δ34S values of pyrite from the ore deposit range from 0.7‰ to 5.60‰ with a mean at 2.70‰, close to mantle and meteorite sulphur. Among Pb isotopes,206Pb/204Pb values range from 18.375 to 18.436,207Pb/204Pb values from 15.694 to 15.8, and208Pb/204Pb values from 38.747 to 39.067. The δ13C values of calcite associated with the ores range from −0.2‰ to −0.5‰ and their δ18O values show variation from 9.4‰ to 12.6‰, suggesting a mixed fluid source. The3He/4He and40Ar/36Ar ratios of fluids trapped in pyrite are in the range of 0.27–1.11 Ra and 439.4–826, respectively, with calculated proportion of the mantle-derived He ranging from 3.25% to 14.03% and atmosphere argon ranging from 35.8% to 67.3%. The data suggest that the ore-forming fluids were derived from the crust and were mixed with a distinct contribution of mantle helium. The Re and Os values vary from 32 × 10−6to 93.02 × 10−6and from 0.01 × 10−9to 0.34 × 10−9, respectively. The model ages of molybdenite range from 126.96 ± 1.82 Ma to 129.49 ± 2.04 Ma, with a weighted mean age of 128.08 ± 0.75 Ma and isochron age of 130.3 ± 3 Ma. These ages are close to the age of the associated quartz diorite porphyrite pluton, suggesting a close relationship between Cretaceous magmatism and metallogeny in NE China. A comparison of the Yinan gold deposit in the Luxi area with those of the Jiaodong area shows that the contrast in metallogenic features between the two are linked with the tectonic and geodynamic history. [ABSTRACT FROM AUTHOR]

Quartz-vein type gold mineralization at Xishimen is a recently discovered gold deposit in the central North China Craton. More than 50 auriferous quartz veins occur in this region within a NNW–SSE-trending fault zone 4600 m in length and 3–10 m wide. Wall rocks are mainly Precambrian tonalite–trondhjemite–granodiorite (TTG) gneisses and associated supracrustals, modified by K-feldspathization and pyrite-phyllic hydrothermal alteration. Based on detailed field and petrographic studies, we identify five episodes of mineralization: pyrite-phyllic stage (I), coarse-grained pyrite-milky white quartz stage (II), fine-grained smoky grey quartz-pyrite stage (III), fine-grained smoky grey quartz-polymetallic sulphide stage (IV), and quartz-carbonate stage (V). We present results of δ34S analysis of sulphide minerals from the different stages which show tightly clustered values in the range of –1.0‰ to 2.1‰, close to those of mantle and meteorite sulphur. Lead isotopic ratios of pyrite from the early to main stages also show restricted ranges with206Pb/204Pb of 16.289–17.286,207Pb/204Pb of 15.217–15.453,208Pb/204Pb of 37.012–38.232, implying lower crustal input.3He/4He and40Ar/36Ar ratios of fluid trapped in pyrite are 0.68 Ra to 1.20 Ra (where Ra is the3He/4He ratio of air = 1.4 × 10−6) and 540.9–1065, respectively.3He and4Ar concentrations vary from 10.05 to 18.5 (10−7 cm3STP/g) and 6.15 to 17.4 (10−7cm3STP/g), respectively, with calculated mantle helium ranging from 8.47% to 14.96% (average 11.01%). δ18OQand δ18DQvalues of quartz range from 8.0‰ to 13.2‰ and –101.9‰ to –70.5‰, respectively, with calculated δ18OWvalues of the mineralizing fluid ranging from 1.11‰ to 5.72‰, suggesting the mixing of magmatic aqueous fluid with meteoric water during gold precipitation. We correlate the mixed crust–mantle signature of the ore-forming sources to magmatism and metallogeny associated with Mesozoic inhomogeneous lithosphere thinning in the central North China Craton. [ABSTRACT FROM AUTHOR]

Abstract: The Beiminghe (BMH) iron ore in the southern part of the Taihang Mountain (TM), Hebei province, is one of the largest skarn iron deposits in China. Here we report phlogopite 40Ar–39Ar and zircon U–Pb age data, as well as sulfur, lead, and He–Ar isotope geochemistry of pyrite from the ores and skarnitized rocks in the deposit in an attempt to constrain the timing and mechanism of formation of the mineralization. The phlogopite 40Ar–39Ar and LA-ICP-MS zircon U–Pb data show markedly consistent ages constraining the timing of ore formation as 136–137Ma. The presence of several inherited zircons with late Archean or Paleoproterozoic ages indicates the participation of the basement rocks during the ore-forming process. The δ34S values of pyrite from the ores range from 12.2 to 16.5‰, with 206Pb/204Pb=17.84–18.79, 207Pb/204Pb=15.46–15.62, and 208Pb/204Pb=37.93–39.75, suggesting that continental crust is the major contributor. This is further confirmed by the He–Ar isotope data (3He/4He=0.0648–0.1886 Ra, mean 0.1237Ra; 40Ar/36Ar=311.7–22909.4; and 40Ar⁎/4He=0.036–0.421). The Mesozoic magmatism and metallogeny in the BMH correlate well with the peak event of lithospheric thinning and destruction of the North China Craton during this process, the early Precambrian lower crustal rocks in the region were re-melted through underplating of mantle magmas, leading to the formation of the Beiminghe monzodioritic pluton. Minor mantle input occurred during the evolution of the monzodiorite magma, which scavenged the ore-forming materials from the lower crust. Interaction of the magmas and fluids with the surrounding rocks resulted in the formation of the Beiminghe skarn iron deposits. The magmatism and metallogeny in the Taihang Mountain are signatures of the extensive craton destruction and lithospheric thinning in the eastern part of the North China Craton during Mesozoic, probably associated with Pacific slab subduction. [Copyright &y& Elsevier]

[Display omitted] • Bitumen Sm-Nd age of 234.6 Ma is interpreted as the hydrocarbon deposition timing. • The ore-forming age of Erdaokan is constrained at middle Triassic. • Bitumen Sm-Nd can be used to constrain the hydrothermal mineralization age. Dating of bitumen can potentially constrain both the timing of mineralization and hydrocarbon deposition in hydrocarbon-bearing hydrothermal deposits. Here we report for the first time direct Sm-Nd dating on bitumen from the Erdaokan Ag-Pb-Zn deposit, a newly discovered, large, hydrocarbon-bearing hydrothermal deposit with 2964 kt of ore and 1535 t Ag with an average grade of 517 g/t Ag, 0.6 wt% Pb and 0.41 wt% Zn in the Back-Arc basin of NE Great Xing'an Range, NE China. Dating results show that Sm-Nd isochron age of four bitumen samples is 234.6 ± 1.2 Ma and an isochron age that includes three galena and four bitumen samples is 234.9 ± 1.4 Ma. In order to verify these ages, we performed Rb-Sr dating on pyrite and galena from the same deposit and U-Pb dating of zircon from the adjacent diorite porphyrite dike, which yielded ages of 232.9 ± 2.3 Ma and 234.2 ± 2.8 Ma, respectively. The highly concordant ages from multiple techniques confirms that bitumen Sm-Nd isotopic dating is reliable, and that the ages obtained in our study represent the hydrocarbon deposition as well as mineralization timing in the deposit. We conclude that, in the Duobaoshan metallogenic belt, the Erdaokan Ag-Pb-Zn deposit is the first identified large, Middle Triassic, hydrocarbon-bearing silver-lead–zinc deposit and is of great significance to the regional metallogenesis research and prospecting work in the Great Xing'an Range. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study deepens understanding of the spatial and temporal evolution of minerals in the Bayan Obo Deposit. • Detailed mineralogical assemblages and fabric features of each ore are presented. • This study established the formation mechanism of different REE-Nb-Fe minerals and the metallogenic process of the deposit. The Bayan Obo deposit in the northern margin of the North China Craton is a world-class REE-Nb-Fe deposit, the complex mineralization history of which remains unresolved. In this study, we employ SEM and Image J software combined with mineralogical data obtained by in-situ EDS and EPMA analyses to analyze petrographic images rapidly and to investigate the mineralogical assemblages of each type of rocks/ores from the Main Orebody in an attempt to understand the mineralization process and ore-formation mechanism of this deposit. We identify three metallogenic periods and six ore-forming stages based on the field occurrence of ores combined with published geochronological data. The Mesoproterozoic magmatic event comprises two stages, which were distinguished as the coarse-grained dolomite stage (stage 1) and the fine-grained dolomite stage (stage 2). Three stages were recognized in the Mesoproterozoic shear deformation-hydrothermal mineralization period, including the disseminated mineralization stage (stage 3), the banded mineralization stage (stage 4) and the massive mineralization stage (stage 5). The Paleozoic hydrothermal period involved the vein mineralization stage (stage 6). Based on detailed studies of the mineral assemblages and paragenesis, as well as the complex textures of the ores, we propose a model of the multi-stage metallogenic process as follows: (1) The REE minerals and rutile occurring as inclusions wrapped within magmatic idiomorphic dolomite grains indicate that the REE-Nb mineralization might have started during the magmatic period. (2) The Nb minerals, such as fergusonite and ilmenorutile, intergrown with REE minerals, such as monazite and bastnäsite, indicate that the Nb and REE were transported by the same ore-forming magma or fluid and precipitated during the same metallogenic process. (3) From the fine-grained dolomite stage to the massive mineralization stage (from stage 2 to stage 5), the mineral assemblages become more complex, with a gradual increase in the degree of hydrothermal alteration suggesting that more hydrothermal fluid was involved in the ore mineralization. (4) The complex mineralogical assemblages and textural relationships indicate multiple formation mechanisms for the REE-Nb-Fe minerals. We propose that the unusually large volume of REE-Nb-Fe resources in the Bayan Obo deposit was the result of combined magma and hydrothermal fluid activities in the Mesoproterozoic (from stage 1 to stage 5), whereas the fluids only caused reactivation of the ore materials previously deposited without the addition of exogenous materials in the Paleozoic stage (stage 6). [ABSTRACT FROM AUTHOR]