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The Handan–Xingtai region in the southern Taihang Mountains in central North China Craton hosts several skarn‐type iron deposits. Here we investigate an ore‐forming intrusion associated with a typical iron skarn deposit to explore the magmatic evolution from mineral zoning textures, and to constrain the ore genesis. We report results of X‐ray mapping of the composition of amphibole and plagioclase. The amphibole thermobarometers suggest: (a) magma chamber at a depth of 17 km; (b) two types of magma with different physical and chemical properties, one representing the main magma chamber with high water content, and the other characterized by more mafic composition and higher oxygen fugacity. The final emplacement depth of magma is estimated as ca. 1.5 km. The oxygen fugacity shows an obvious increase from the primary magma chamber to its emplacement depth. The zoning texture of plagioclase and amphibole suggest that the mafic magma was injected into felsic magma chamber many times, leading to magma mixing. We construct a petrogenetic and metallogenic model which envisages the following processes: (a) during 135–120 Ma, mantle‐derived magma and crust‐derived magma underwent mixing and homogenization at the crust–mantle boundary; (b) the hybrid magma rose to the middle crust and formed a magma chamber; (c) multiple injection of mafic magma into the felsic magma chamber resulted in oscillatory zoning; (d) the magma with high water content and higher modal content of plagioclase and amphibole formed through multiple magmatic injection‐mixing‐crystallization processes; and (f) the high water content and higher oxygen fugacity enabled the hybrid magma to rise to the shallow crust, where it released iron‐rich melt and fluids, which reacted with the surrounding limestones to generate the skarn‐ type iron deposit. [ABSTRACT FROM AUTHOR]

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 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]

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 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]

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]

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 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 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]