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The Qiman Tagh W-Sn ore belt is located in the westernmost sector of the East Kunlun Orogen, NW China. It has been recognized as a unique W-Sn belt that formed in the early Paleozoic and related to closure of the Proto-Tethys. To understand the evolution of ore-forming fluids and its relationship with the tectonic setting of East Kunlun Orogen, we report the results obtained from fluid inclusion and H-O isotopic studies of ores and quartz veins for the Qiman Tagh W-Sn ore belt. Mineralization in Qiman Tagh includes four stages characterized by quartz-cassiterite-wolframite assemblage stage 1, quartz ± scheelite assemblage stage 2, quartz-polymetallic sulfides stage 3, and ore-barren veins stage 4. The former two stages are conducive to mineralization, while the latter two stages are less important. The fluid inclusions are distinguished between CO 2 -H 2 O (C-type) and NaCl-H 2 O (W-type) in composition, containing a trace of CH 4 , N 2 , C 2 H 6 , SO 2 , and CO 3 2– . Cassiterite and quartz in stage 1, instead of wolframite, contain a great deal of C-type inclusions. All inclusions in minerals of stage 1 yield homogenization temperatures of 230.1–384.1 °C (peaking at 310–320 °C), with salinities lower than 14.76 wt% NaCl equiv. and bulk densities of 0.63–0.89 g/cm 3 . The stage 2 minerals contain both two types of inclusions, yielding homogenization temperatures of 183.4–335.9 °C (peaking at 280–290 °C), with salinities lower than 14.53 wt% NaCl equiv. and bulk densities of 0.66–0.97 g/cm 3 . Fluid inclusions in minerals of stages 3 and 4 are mainly W-type and homogenized at temperatures of 140.6–277.6 °C (peaking 210–220 °C), and 116.9–255.1 °C (peaking 160–170 °C), respectively. The H-O isotopic systematics shows that the fluids were dominated by magmatic water in stages 1 and 2, but by meteoric water in stages 3 and 4. Integrating all the geological and geochemical data, we conclude that the fluids forming the Qiman Tagh W-Sn ore belt evolved from granite-derived, CO 2 -rich and reducing, to meteoric water-dominated, CO 2 -poor and oxidizing. Fluid immiscibility, cooling and interaction with rocks are main mechanisms for metallic deposition. [ABSTRACT FROM AUTHOR]

The large Yueyang Ag-Au-Cu deposit is commonly regarded as a low-sulfidation epithermal deposit in the Zijinshan orefield, Fujian Province, southeastern China. The Ag-Ag-Cu orebodies hosted in the Zijinshan granitic batholith are mainly stratoid and lens in shape, and controlled by a series of NW-trending listric faults with shallow dip angles. Four mineralization stages are recognized on the basis of mineral assemblage, ore fabrics, and crosscutting relationships of the ore veins, namely: pre-ore (pyrite + sericite + quartz ± chlorite), main Cu (chalcopyrite + pyrite + sericite + quartz ± bornite), main Ag-Au (Ag and Au minerals + pyrite + quartz + adularia ± calcite ± apatite ± chalcopyrite ± galena ± sphalerite) and post-ore (quartz ± chalcedony ± calcite) stages. Fluid inclusions (FIs) in the deposit include aqueous liquid-rich (WL-), aqueous vapor-rich (WV-), and minor carbonic (C-) and daughter mineral-bearing (S-) type ones. WL-subtype is the main inclusion type in the Yueyang deposit, accounting for more than 90% in proportion in each stage. Minor WV-subtype inclusions occur in both the main Cu and Ag stages, while the C-type and S-type ones are only observed in the main Cu stage. Fluid inclusion and H-O isotope study indicated that the ore-forming fluid of the main Cu stage is primarily magmatic vapor, which further underwent fluid boiling and mixing with meteoric water, while the ore-forming fluid of the main Ag stage is meteoric water-dominated, and the precipitation of silver and gold was mainly resulted from fluid boiling and the precipitation of other sulfides. On the basis of the aforementioned geological, fluid inclusion and stable isotope studies, we proposed a two-stage model for the Yueyang deposit, including a magmatic vapor-related porphyry type Cu mineralization and meteoric water-related low-sulfidation epithermal Ag-Au-Cu mineralization, although the porphyry Cu mineralization is very limited in scale. The mineralization and exhumation depths of the Yueyang deposit are estimated to be 448‒527 m and 18‒97 m, respectively. By comparison with the exhumation depths of other deposits in the Zijinshan orefield, it is suggested that more epithermal deposits could be found in the southwest of the orefield due to less uplift and exhumation therein. [ABSTRACT FROM AUTHOR]

South China Block (SCB) is the area including the Yangtze Craton and the Huanan Orogen where scattered Precambrian terranes are usually regarded as segments of Cathaysia Land. It is the third most important molybdenum metallogenic province in China, next to the Qinling-Dabie area and Northeast China, containing 29 Mo-only or Mo-dominated, 9 W-Mo(-Sn-Bi) and 8 Cu-Mo deposits. These 46 deposits are located mainly in: (1) the Lower Yangtze River Belt of the northeastern Yangtze Craton, (2) the Northern Jiangnan Orogenic Belt that is generally considered a Meso-Neoproterozoic magmatic arc complex accreted onto the southeastern margin of the Yangtze Craton, (3) the Wuyi-Yunkai Orogenic Belt characterized by local exposures of Proterozoic metamorphic terranes and the more widespread Sinian (Uppermost Proterozoic) to Triassic sedimentary sequences, and (4) the Southeast Coastal Volcanic Belt characterized by Yanshanian andesitic to felsic volcanic rocks. Their genetic types are dominated by porphyry and skarn mineral systems, with only a few quartz-vein systems. The orebodies form veins, lens, cylindrical shapes, pipes, or irregular in shape, usually controlled by faults at various scales and volcanic-subvolcanic complexes. The host-rocks are variable in lithologies, including granites, porphyries, volcanic breccias and tuffs, clastic sediments and carbonate rocks, but the high-grade orebodies are usually hosted in carbonate-shale sequences. Hydrothermal mineralization processes can be generally divided into four stages, from early to late, they are (1) K-feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-polymetallic sulfide stockworks, and (4) quartz-carbonate-fluorite veinlets. Fluid-rock interaction as exemplified by wallrock alteration evolved from K-silicate alteration (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alteration, with skarn alteration typically occurring in skarn-type mineral systems. Hydrothermal mineral assemblages vary between two end-members, namely the dry system formed by CO 2 -rich fluids and marked by quartz, K-feldspar, fluorite, carbonate and epidote, and the wet system mainly originated from CO 2 -poor fluids and composed of biotite, sericite and chlorite. The ore-forming fluids are magmatic in origin and show high-temperature and high-salinity. The melt-fluid systems forming Cu-Mo deposits are more oxidizing than those forming the W-Mo or Mo deposits, as suggested by accessory minerals in granitoids and daughter minerals in fluid inclusions. The Cu-Mo deposits are related to the I-type granitic rocks (adakite-like), whereas the W-Mo and Mo-only systems are related to granitic rocks of S- or A-types, although all of them show high K contents. Available isotope ages show that the Mo and Mo-bearing deposits were predominantly formed in the early Yanshanian Orogeny (170–134 Ma), followed by the late Yanshanian Orogeny (110–92 Ma) and the Caledonian Orogeny (450–410 Ma). The Caledonian Mo-mineralization has been observed only in the Wuyi-Yunkai Orogenic Belt and related to the collision between the Yangtze Craton and the pre-Devonian Huanan Orogen or terranes separated from the Cathaysia Land, linked to the assembly of the Gondwana supercontinent. The Early Yanshanian mineralization affected the entire Huanan Orogen and the eastern Yangtze Craton, and resulted from the syn- to post-collisional tectonism following the closure of eastern Paleo-Tethys. The Late Yanshanian Mo deposits mainly occur in the Southeast Coastal Volcanic Belt and the southeastern margin of the Wuyi-Yunkai Orogenic Belt, and are related to the westward subduction of the Paleo-Pacific plate. The skarn-type mineral systems generally show lower Re contents than the porphyry-type deposits in a same tectonic unit, suggesting that carbonate host-rocks have lower Re contents than the causative porphyries. The Re contents in molybdenites from porphyry or porphyry-skarn Cu-Mo systems are > 50 ppm, mainly > 100 ppm, suggesting a source significantly contributed by the mantle; whereas the Re contents in molybdenites from the Mo-only or W-Mo-dominated deposits are < 100 pm, mainly < 50 ppm, indicating a genetic relation to the crust-sourced granitic magmatism. [ABSTRACT FROM AUTHOR]

The Dabie Shan in central East China is a collisional orogenic belt suturing the North China and Yangtze blocks. It was formed by Jurassic-Early Cretaceous continental collision, following the Triassic closure of the northernmost paleo-Tethyan Ocean. In the area, at least ten porphyry Mo systems have been discovered, including two giant ones, with a total reserve of > 3 Mt Mo metal. The porphyry-type Mo mineralization mainly occurred during 156–110 Ma, in the post-collisional extension setting. The location of Mo deposit is controlled by NW- and NNE-trending faults, mostly in the south of the Gui-Mei Fault suturing the North China and Yangtze blocks. Mo mineralization is generally associated with the Yanshanian high-K calc-alkaline metaluminous-peraluminous granitic intrusions, with orebodies being located in the intrusions and/or host-rocks. The hydrothermal ore-forming process generally includes four stages, with the initial ore-forming fluids being featured by high temperature, high salinity and CO 2 -rich. Geochemical signatures indicate that the ore-causative magmatism in the Dabie Shan mainly originated from either the northern or southern Dabie complex, but mixed with the Precambrian rocks of the North China block, except for the Tianmugou porphyry system which shares more similar geological and geochemical characteristics with the porphyry Mo deposits in eastern Qinling Orogen. We also develop a scissor-style intracontinental subduction model to interpret the differences in spatial distribution, geneses, and geochemical and geological characteristics between the Mo deposits in Dabie Shan and Qinling Orogen. In our model, the basement of the North China Block southwardly underthrusted beneath the Dabie Shan, possibly along the Gui-Mei Fault; whilst the basement of the Yangtze Block northwardly underthrusted beneath the Qinling Orogen; and the inferred Minggang-Xinyang fault zone served as a dextral strike-slip fault zone in the North China Block, but acted as a sinistral transpressional fault zone within the orogenic area. Compared to the subduction- or Endako- and rift- or Climax-types of porphyry Mo deposits, the porphyry Mo deposits in the Dabie Shan are unique because of their crustal source for the magma and ore-forming materials, and as such are assigned to the Dabie- or collision-type. Hence we develop a new global tectonic model for porphyry Mo deposits of three types, showing their genetic tectonic settings. [ABSTRACT FROM AUTHOR]

Northwest China, covering northern Xinjiang, northern Gansu and westernmost Inner Mongolia, mainly includes Junggar Basin and its surrounding mountains such as Chinese Altay, Junggar, Chinese Tianshan and Beishan. It lies at the junction of Siberia, Tarim and Kazakhstan plates, and is a key sector of the Central Asian Orogenic Belt (CAOB), characterized by multistage Phanerozoic continental growth. Herein at least nine Mo-only or Mo-dominated, fourteen Cu-Mo, two W-Mo and one Be-Mo deposits have been discovered. These 27 deposits occur in Altay, West Jungar, West Tianshan, East Tianshan and Beishan areas, and have been formed during accretionary or collisional orogenies. The majority of the deposits are porphyry type, followed by the skarn and quartz vein types. The orebodies occur mainly as veins, lens, pods in the positions from inner intrusions through contact zones to the hostrocks distal to causative intrusions. The host-rocks are variable in lithologies, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from orebodies to hostrocks, the wallrock alteration is zoning from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations, with skarn specifically occurring in skarn-type systems. Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-polymetallic sulfide stockworks, and (4) quartz ± carbonate ± fluorite veins or veinlets. The ore-forming fluids were initially magmatic in origin and shew high-temperature and high-salinity, containing daughter mineral- and/or CO 2 -bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO 2 -poor meteoric water. The porphyry Mo deposits can be further subdivided into two subtypes, i.e., Dabie- and Endako-types. The Endako-type Mo deposits, e.g., Suyunhe and Hongyuan, together with all the Cu-Mo systems, were formed in the Palaeozoic subduction-related magmatic arcs. The Dabie-type porphyry Mo deposits, represented by giant Donggebi and Baishan, together with the Mo-only, Mo-dominated and W-Mo or Be-Mo deposits were formed in syn- to post-collisional tectonic setting, with isotope ages ranging 260–213.2 Ma, with the Kumutage skarn-type Mo system being an exception aged 319 Ma. The Dabie-type porphyry Mo deposits are characterized by the CO 2 -bearing fluid inclusions that cannot be observed in the Endako-type porphyry Mo systems. The Re contents in molybdenites from porphyry and porphyry-skarn Cu-Mo systems are mainly > 100 ppm, suggesting a source significantly contributed by the mantle; whereas the Re contents in molybdenites from the Mo-only or W-Mo deposits are mainly < 100 ppm, indicating a genetic relation to the crust-sourced granitic magmatism. Therefore, the types of porphyry Mo deposits and their contrasting geological and geochemical characteristics are a powerful indicator of the tectonic settings; and the available data from the Mo deposits in NW China indicate a Late Carboniferous-Permian transformation from subduction-related accretionary orogeny to continental collision orogeny. [ABSTRACT FROM AUTHOR]

Northeast (NE) China lies in the eastern sector of the Central Asian Orogenic Belt (CAOB) that connects with the Circum-Pacific Orogenic Belt in the east, and accommodates multistage magmatism, crustal growth and mineralization. In this region 69 Mo-only or Mo-dominated and 9 Cu-Mo deposits have been discovered, including 65 deposits ranking medium-size (> 10 Kt Mo metal) or larger in tonnage and containing a total resource of 10.5 Mt Mo metal. Six giant and seventeen large deposits have total reserves of 6.7 and 3.1 Mt Mo, respectively. These deposits occur in the areas surrounding the Songliao Basin, including the northern margin of the North China Craton, the Great Hingan Range and the Ji-Hei Fold Belt, and have been formed during Paleozoic and Mesozoic tectono-magmatic events. All the Mo-only or Mo-dominated deposits were formed in the Mesozoic, postdating the closure of the Paleo-Asia Ocean, and in a series of pulses around 250–200 Ma, 200–160 Ma, 160–130 and < 130 Ma (130–100 Ma), suggesting that the Paleozoic crust, compared with the Mesozoic crust, was less sialic and unfavorable for Mo mineralization. This is supported by the variation of Re contents in molybdenites from the deposits, i.e., increasing with the Cu/Mo ratios and the ore-forming ages. Mineralization was generally associated with granitic rocks mainly of crust-sourced and high-K calc-alkaline to shoshonite series. The majority of the deposits are porphyry (including breccia pipes) type, followed by the skarn and quartz vein types. The porphyry Mo deposits can be further subdivided into three subtypes, i.e., collision- or Dabie-, rift- or Climax-, and subduction- or Endako-types. The Mo deposits aged 250–200-Ma and 200–160-Ma belong to the collision-type and have been formed in syn- to post-collisional tectonic setting. The 160–130-Ma Mo mineralization mainly occurs in the Great Hingan Range and northern margin of the North China Craton, and includes Endako- and Climax-types of porphyry Mo systems, which resulted from southward subduction of the Mongol-Okhotsk oceanic plate. The 130–100-Ma deposits belong to the Endako-type and are only located in the eastern Ji-Hei Fold Belt, which must be related to the westward subduction of the Paleo-Pacific oceanic plate. Therefore, as shown by the porphyry Mo deposits in NE China, these mineral systems are a powerful indicator of tectonic settings and associated evolutionary trends. [ABSTRACT FROM AUTHOR]

The Great Hingan Range is located in the eastern sector of the Central Asia Orogenic Belt, and is the second important Mo province in China, next to the Qinling–Dabie orogenic belt. Previous studies concluded that all the Mo deposits (Mo-only or Mo-dominated polymetallic) in the area were formed in the Mesozoic, and related either to the syn- to post-collisional setting following the closure of the Paleo-Asia Ocean, or to the westward subduction of the Pacific plate. However, the fluids forming the giant Diyanqin'amu porphyry Mo deposit in the area disagree with the features of collision-type Mo deposits, but accord with those of the subduction- or continental arc-type. The Mo mineralization is hosted in the Late Jurassic volcanic rocks and genetically related to the buried porphyritic granite and aplitic granite. Two porphyritic granite samples yield LA-ICP-MS zircon weighted mean 206 Pb/ 238 U ages of 158.7 ± 0.8 Ma (MSWD = 0.64, 2σ) and 158.0 ± 0.9 Ma (MSWD = 0.38, 2σ), respectively. The aplitic granite yields a zircon U–Pb weighted mean 206 Pb/ 238 U age of 156.9 ± 1.1 Ma (MSWD = 0.48, 2σ), slightly younger than the porphyritic granite. Seven molybdenite samples from the ores yield Re–Os isotope ages of 156.1 ± 2.2 to 158.1 ± 4.3 Ma. These ages constrain that the Diyanqin'amu Mo system was formed in the period of 159–156 Ma. The granites at the deposit have high contents of SiO 2 , K 2 O and Al 2 O 3 , and low contents of TiO 2 , MgO and CaO, showing a peraluminous high-K calc-alkaline affinity. These granites and the host volcanic rocks are characterized by enrichment of K, Rb, U, Pb, Th and LREE, and depletion of Nb, Ta, Ti and HREE, with negative Eu anomaly, which are similar to magmatic rocks in the Andean arc. Zircon grains from the granites show positive ε Hf ( t ) values of 4.2–9.0, with T DM2 (Hf) ages of 0.63–0.94 Ga. These geochemical data imply that the granites at Diyanqin'amu are highly fractionated I-type, formed in a continental arc generated by the southeastward subduction of the Mongol–Okhotsk oceanic plate. [ABSTRACT FROM AUTHOR]

The Waifangshan Mo-quartz vein cluster occurs at the northernmost margin of the Qinling Orogen. The orebodies occur as quartz veins and are controlled by low-angle faults. We identify three hydrothermal stages, characterized by veinlets of quartz–pyrite, quartz–molybdenite–pyrite–chalcopyrite–galena–sphalerite, and quartz–carbonate assemblages, respectively. The early-stage quartz veins were structurally-deformed, brecciated, and filled by non-deformed middle- or late-stage veinlets, suggesting that the mineralization is associated with a tectonic transition from compression to extension. Five molybdenite separates from the Zhifang Mo deposit yield individual Re–Os ages from 241.2 ± 1.6 to 247.4 ± 2.5 Ma, with a weighted mean age of 243.8 ± 2.8 Ma. Individual Re–Os isotope ages of four molybdenite samples from the Badaogou Mo deposit range from 238.9 ± 2.1 to 255.8 ± 2.2 Ma, with a weighted mean age of 246 ± 10 Ma. Four analyses of molybdenite separates from the Xiangchungou Mo deposit yield individual Re–Os isotope ages of 243.8 ± 8.8 to 247.7 ± 4.4 Ma, with a weighted mean age of 246.0 ± 1.1 Ma. All of these data yield a weighted mean age of 241.9 ± 1.9 Ma, coeval with the accretionary orogeny. We thus conclude that the Waifangshan Mo-quartz veins formed during a transition from continental arc to back-arc setting. The Waifangshan Mo-quartz veins share similar geological, geochemical and geochronological features with the orogenic-type systems. We propose that the Waifangshan Mo-quartz veins are an orogenic-type Mo mineralization, and possibly represent the deepest member in the crustal continuum model of the orogenic-type mineral systems. The molybdenite samples from the Mo-quartz veins in the Waifangshan area have low Re contents (1.457 to 39.16 ppm), suggesting a continental crust-dominated source. [ABSTRACT FROM AUTHOR]

The Xiaobaishitou W (–Mo) deposit is located in the eastern segment of the Central Tianshan, northwestern China. The deposit represents a skarn system distributed in the contact zones of biotite granite and crystalline limestone of the Mesoproterozoic Kawabulag Group. The Xiaobaishitou deposit is characterized by a typical calc-silicate mineralogy dominated by garnet, diopside and wollastonite, with minor epidote, tremolite, actinolite, chlorite, quartz, fluorite and calcite. The prograde and retrograde skarns are characterized by garnet–clinopyroxene–wollastonite and epidote–tremolite–actinolite–chlorite, respectively, intruded and replaced by mineral assemblages of scheelite–cassiterite–magnetite, quartz–sulfides and calcite–quartz–fluorite in younger order. Six molybdenite samples from the deposit yielded Re − Os isotope model ages ranging from 239.7 ± 3.6 Ma to 251.4 ± 3.6 Ma. The zircon crystals from biotite granite and Mo-mineralized granite yield weighted 206 Pb/ 238 U age of 242 ± 1.7 and 240.5 ± 2.1 Ma, respectively. Both the zircon U − Pb and the molybdenite Re − Os ages obtained in this study fall in a narrow span of 242–240 Ma, which suggest that the Xiaobaishitou W (–Mo) system was formed in the Triassic. The Re contents of the molybdenites range from 40.33 to 64.67 ppm, suggesting that the ore-forming materials were derived mainly from continental crust together with the involvement of minor mantle components. Combined with the 87 Sr/ 86 Sr ratios of tungsten-bearing quartz veins from other studies, which scatter between 0.707153 and 0.709877, demonstrating mixing between two end-member isotopic compositions of crust and mantle. It can be concluded that the Indosinian Xiaobaishitou deposit was formed in a tectonic transition from collisional crust shortening and thickening to post-collisional extension and thinning. [ABSTRACT FROM AUTHOR]

Isotope dilution thermal ionization mass spectrometry (ID-TIMS) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) are two popular analytical methods used to constrain the age of minerals, including cassiterite. Compared to ID-TIMS, the LA–ICP-MS analytical method is often favoured due to its simple analytical procedure and sample preparation, although the methodology constantly needs modification. Our recent paper on dating cassiterite from the Baiganhu W-Sn ore field in NW China based on LA–MC-ICP-MS and ID-TIMS methods has received a response from Dr. Leonid A. Neymark (2017). Definitely, Neymark is appreciated, and his suggestions are helpful to improve the methodology of cassiterite U–Pb geochronology. Based on a discussion on the cassiterite U–Pb dating method, we re-confirm the validity of the cassiterite U-Pb ages for the Baiganhu W-Sn ore field. The initial non-radiogenic 204 Pb used in the U-Pb isochron approach can be replaced by the non-radiogenic 207 Pb, because the radiogenic 207 Pb decayed from 235 U can be ignored in cassiterite with a high Pb content. Therefore, the cassiterite U-Pb isochron yields an age similar to that obtained from T-W concordia for the same sample, testifying the validity of the cassiterite 238 U/ 207 Pb– 206 Pb/ 207 Pb isochron method. [ABSTRACT FROM AUTHOR]

The Qiangma gold deposit is hosted in the > 1.9 Ga Taihua Supergroup metamorphic rocks in the Xiaoqinling terrane, Qinling Orogen, on the southern margin of the North China Craton. The mineralization can be divided as follows: quartz-pyrite veins early, quartz-polymetallic sulfide veinlets middle, and carbonate-quartz veinlets late stages, with gold being mainly introduced in the middle stage. Three types of fluid inclusions were identified based on petrography and laser Raman spectroscopy, i.e., pure carbonic, carbonic-aqueous (CO 2 –H 2 O) and aqueous inclusions. The early-stage quartz contains pure carbonic and CO 2 –H 2 O inclusions with salinities up to 12.7 wt.% NaCl equiv., bulk densities of 0.67 to 0.86 g/cm 3 , and homogenization temperatures of 280−365 °C. The early-stage is related to H 2 O–CO 2 ± N 2 ± CH 4 fluids with isotopic signatures consistent with a metamorphic origin (δ 18 O water = 3.1 to 5.2‰, δD = − 37 to − 73‰). The middle-stage quartz contains all three types of fluid inclusions, of which the CO 2 –H 2 O and aqueous inclusions yield homogenization temperatures of 249−346 °C and 230−345 °C, respectively. The CO 2 –H 2 O inclusions have salinities up to 10.9 wt.% NaCl equiv. and bulk densities of 0.70 to 0.98 g/cm 3 , with vapor bubbles composed of CO 2 and N 2 . The isotopic ratios (δ 18 O water = 2.2 to 3.6‰, δD = − 47 to − 79‰) suggest that the middle-stage fluids were mixed by metamorphic and meteoric fluids. In the late-stage quartz only the aqueous inclusions are observed, which have low salinities (0.9−9.9 wt.% NaCl equiv.) and low homogenization temperatures (145−223 °C). The isotopic composition (δ 18 O water = − 1.9 to 0.5‰, δD = − 55 to − 66‰) indicates the late-stage fluids were mainly meteoric water. Trapping pressures estimated from CO 2 –H 2 O inclusions are 100−285 MPa for the middle stage, suggesting that gold mineralization mainly occurred at depths of 10 km. Fluid boiling and mixing caused rapid precipitation of sulfides and native Au. Through boiling and inflow of meteoric water, the ore-forming fluid system evolved from CO 2 -rich to CO 2 -poor in composition, and from metamorphic to meteoric, as indicated by decreasing δ 18 O water values from early to late. The carbon, sulfur and lead isotope compositions suggest the hostrocks within the Taihua Supergroup to be a significant source of ore metals. Integrating the data obtained from the studies including regional geology, ore geology, and fluid inclusion and C–H–O–S–Pb isotope geochemistry, we conclude that the Qiangma gold deposit was an orogenic-type system formed in the tectonic transition from compression to extension during the Jurassic−Early Cretaceous continental collision between the North China and Yangtze cratons. [ABSTRACT FROM AUTHOR]

The Donggou Mo deposit in the eastern Qinling area, China, is a giant porphyry system discovered based on a targeting concept by using the tectonic model for collisional orogeny, metallogeny and fluid flow (CMF model). Mo mineralization is associated with the Donggou aluminous A-type granite porphyry and was formed during the Early Cretaceous in a tectonic regime of continental extension. The orebodies mainly occur as numerous veinlets in the host-rocks. Hydrothermal ore-forming processes include at least three stages, characterized by veinlets of (1) quartz + K-feldspar + minor molybdenite, (2) quartz + molybdenite ± beryl and (3) quartz + carbonate + fluorite. Three types of fluid inclusions (FIs) are distinguished in quartz and beryl in stages 1 and 2, i.e., aqueous (W-type), carbonic–aqueous (C-type) and solid-bearing (S-type), with only aqueous FIs observed in stage 3 minerals. S-type FIs contain variable daughter minerals including halite, chalcopyrite, calcite and an unidentified transparent crystal, but only halite can dissolve during heating. Halite-bearing S-type FIs are mainly homogenized by halite dissolution at 182–416 °C, corresponding to salinities of 30.9–49.2 wt.% NaCl equiv.; minor halite-bearing S-type FIs are homogenized to liquid at 190–360 °C via vapor disappearance, with salinities of 29.1–36.2 wt.% NaCl equiv. Other FIs in minerals of stages 1, 2 and 3 are homogenized at temperatures of 341–550 °C, 220–440 °C and 125–225 °C, with salinities of 8.0–18.3, 5.3–16.8 and 0.5–7.3 wt.% NaCl equiv., respectively. The estimated minimum trapping pressures are up to 141 MPa in stage 1 and up to 81 MPa in stage 2, respectively, corresponding to an initial mineralization depth of no less than 5 km. The quartz in veinlets yields δ 18 O values of 8.5–10.0‰, corresponding to δ 18 O H 2 O values of − 2.9 to 5.9‰, while the δD H 2 O values of fluid inclusions range from − 59 to − 82‰. These data suggest that the ore fluids forming the Donggou deposit changed from high-temperature, high-salinity, CO 2 -rich magmatic to low-temperature, low-salinity and CO 2 -poor meteoritic fluids via boiling and mixing, resembling those of other magmatic–hydrothermal systems in Qinling Orogen and Dabie Shan. This supports the notion that the porphyry systems generated in a post-collisional tectonic setting were initially CO 2 -rich, as indicated by abundant C-type and CO 2 -bearing S-type fluid inclusions. [ABSTRACT FROM AUTHOR]

The Wenyu giant gold deposit is hosted in the Precambrian Taihua Supergroup metamorphic rocks within the Xiaoqinling terrane (Qinling Orogen), on the southern margin of the North China Craton. The mineralization can be divided into three stages: quartz–pyrite veins early, quartz–sulfide veins middle (main), and carbonate–quartz veinlets late, with gold being mainly introduced in main stage. Quartz formed in two earlier stages contains three compositional types of fluid inclusions, i.e. pure CO2, CO2–H2O and NaCl–H2O, but the late-stage minerals only contain the NaCl–H2O inclusions. The inclusions in quartz formed in the early, main and late stages yield total homogenization temperatures of 262–417°C, 236–407°C and 114–239°C, respectively, with salinities no higher than 13wt.% NaCl equiv. Trapping pressures estimated from CO2–H2O inclusions are 139–399MPa and 111–316MPa in the early and main stages, corresponding to mineralization depths of 14km and 11km, respectively. Fluid boiling and mixing caused rapid precipitation of sulfides and native Au. Through boiling and inflow of meteoric water, the ore-forming fluid system evolved from CO2-rich to CO2-poor in composition, and from metamorphic to meteoric, as indicated by decreasing δ18Owater values from early to late. The carbon, sulfur and lead isotope compositions suggest the hostrocks within the Taihua Supergroup to be a significant source of ore metals. Integrating the data obtained from the studies including regional geology, ore geology, fluid inclusion and C–H–O–S–Pb isotope geochemistry, we conclude that the Wenyu gold deposit was an orogenic-type system formed in the tectonic transition from compression to extension during the Jurassic–Early Cretaceous continental collision between the North China and Yangtze Cratons. [ABSTRACT FROM AUTHOR]

The Luoboling Cu–Mo deposit in the Zijinshan Orefield, Fujian province, southeastern China, is a large porphyry deposit hosted by the Sifang granodiorite and the Luoboling granodiorite porphyry. The largest Cu–Mo orebody is saddle-shaped with various types of hydrothermal veinlets. Intensive hydrothermal alteration in the deposit is characterized by outward zoning from potassic, overprinted by phyllic alteration, to phyllic and alunite–dickite alteration. Based on the mineral assemblages and crosscutting relationships of veins, the ore-forming process can be divided into three stages, namely: an early-stage K-feldspar+quartz±magnetite±molybdenite veins associated with potassic alteration; a middle-stage quartz+molybdenite+chalcopyrite+pyrite veins in phyllic zone; and a late-stage quartz±gypsum veins in the phyllic and alunite–dickite alteration zones. Six molybdenite separates yield a Re−Os isochron age 104.6±1.0Ma, which is identical to the age of emplacement of the Sifang and Luoboling granodiorite porphyries. Three types of fluid inclusions (FIs) were observed at the Luoboling deposit: 1) NaCl–H2O (aqueous), 2) daughter mineral-bearing and 3) CO2–H2O fluid inclusions. FIs of the early and middle stages are predominantly vapor-rich aqueous and daughter mineral-bearing inclusions, together with minor CO2-rich and liquid-rich aqueous inclusions; whereas the late-stage minerals only contain liquid-rich aqueous inclusions. Homogenization temperatures and salinities of FIs trapped in the early-stage minerals range from 420 to 540°C and 0.4 to 62.9wt.% NaCl equiv., respectively. FIs of the middle-stage yield homogenization temperatures of 340 to 480°C and salinities of 0.5 to 56.0wt.% NaCl equiv. CO2 content and the oxygen fugacity (indicated by daughter minerals) of FIs trapped in middle-stage minerals are lower than those in the early stage. The liquid-rich aqueous inclusions of the late-stage homogenize at temperatures of 140 to 280°C, yielding salinities of 0.4 to 8.4wt.% NaCl equiv. The minimum estimated pressures of the three stages are 30–70MPa, 10–40MPa and 1–10MPa, respectively, corresponding to minimum ore-forming depths of 1–2.8km. Fluids trapped in early, middle and late stages yield δD values of −67‰ to −54‰, −54‰ to −70‰, and −62‰, and δ18O values of 5.4‰ to 6.7‰, 2.8‰ to 4.2‰, and −2.1‰, respectively. Fluid boiling, which resulted in the formation of stockworks and the precipitation of sulfides, occurred in the early and middle stages. The fluids subsequently evolved into a low temperature, low salinity system in the late stage, along with an input of meteoric water. The Luoboling porphyry Cu–Mo system was developed in a transition from continental arc to back-arc extension region, which was related to the westward subduction of the paleo-Pacific plate beneath the Huanan Orogen. [ABSTRACT FROM AUTHOR]

The Eastern Qinling, Central China, containing more than 20 Mesozoic porphyry±skarn systems, is the most important Mo province in the world. The Shangfanggou giant Mo deposit, Luanchuan County, Henan Province, is a porphyry-skarn system hosted in a lithologic association comprising carbonaceous sandstone, shale, carbonate and chert within the Neoproterozoic Luanchuan Group. Mo ores are mainly altered porphyry, skarn and hornfels, with minor altered gabbro. The mineralization process includes four stages, potassic alteration of the porphyry and skarnization of dolomite marble in stage 1, stockworks of quartz+molybdenite±sulfide (stage 2), pyrite+quartz±sulfides (stage 3), and carbonate±quartz±fluorite (stage 4), respectively. Mo mineralization was generally associated with strong silicification and/or phyllic alteration. The fluid inclusions in minerals include three compositional types, i.e., CO2-bearing (C-type), aqueous (W-type) and daughter mineral-bearing (S-type). Minerals formed in stages 1 to 3 contain all the three types of FIs, but the stage 4 minerals only contain the W-type FIs. Oxides and Cu-phosphate are recognized as daughter minerals in S-type inclusions in minerals of stage 1, whereas the daughter sulfide and reducing gases such as CO, CH4, H2S and C2H6 can be observed in quartz of stages 2 and 3, suggesting that the ore-forming fluids were initially oxidizing and then evolved to reducing. Boiling fluid inclusion assemblages can be observed in minerals formed in stage 2 or earlier, but not in stage 3 or later. Fluid boiling caused CO2 escape, oxygen fugacity decrease and rapid precipitation of ore minerals, and was a key factor causing Mo-mineralization at Shangfanggou. Data and interpretations presented in this contribution show that the fluids forming the Shangfanggou Mo deposit evolved from CO2-rich, high-salinity hypothermal, to CO2-poor, low-salinity epithermal (low-T). The Mo mineralization at the Shangfanggou deposit mainly occurred at depth of 6.6–7.0km, deeper than the majority of porphyry systems in volcanic arcs, which resulted from a CO2-rich magma–fluid system originating from partial melting of thickened lower crust. The Shangfanggou mineral system developed during 158–134Ma when the Yangtze–North China continental collision began to evolve from compression to extension. Magmatic hydrothermal deposits developed in a continental collision regime are generally formed by CO2-rich, high-salinity fluids. [ABSTRACT FROM AUTHOR]

Abstract: The Yindongpo gold deposit is located in the Weishancheng Au–Ag-dominated polymetallic ore belt in Tongbai Mountains, central China. The ore bodies are stratabound within carbonaceous quartz–sericite schists of the Neoproterozoic Waitoushan Group. The ore-forming process can be divided into three stages, represented by early barren quartz veins, middle polymetallic sulfide veinlets and late quartz–carbonate stockworks, with most ore minerals, such as pyrite, galena, native gold and electrum being formed in the middle stage. The average δ18Owater values changed from 9.7‰ in the early stage, through 4.9‰ in the middle stage, to −5.9‰ in the late stage, with the δD values ranging between −65‰ and −84‰. The δ13CCO 2 values of ore fluids are between −3.7‰ and +6.7‰, with an average of 1.1‰. The H–O–C isotope systematics indicate that the ore fluids forming the Yindongpo gold deposit were probably initially sourced from a process of metamorphic devolatilization, and with time gradually mixed with meteoric water. The δ34S values range from −0.3‰ to +5.2‰, with peaks ranging from +1‰ to +4‰. Fourteen sulfide samples yield 206Pb/204Pb values of 16.990–17.216, 207Pb/204Pb of 15.419–15.612 and208Pb/204Pb of 38.251–38.861. Both S and Pb isotope ratios are similar to those of the main lithologies of the Waitoushan Group, but differ from other lithologic units and granitic batholiths in the Tongbai area, which suggest that the ore metals and fluids originated from the Waitoushan Group. The available K–Ar and 40Ar/39Ar ages indicate that the ore-forming process mainly took place in the period of 176–140Ma, during the transition from collisional compression to extension and after the closure of the oceanic seaway in the Qinling Orogen. The Yindongpo gold deposit is interpreted as a stratabound orogenic-style gold system formed during the transition phase from collisional compression to extension. The ore metals in the Waitoushan Group were extracted, transported and then accumulated in the carbonaceous sericite schist layer. The carbonaceous sericite schist layer, especially at the junction of collapsed anticline axis and fault structures, became the most favorable locus for the ore bodies. [Copyright &y& Elsevier]

Abstract: The Dahu Au–Mo deposit is a structure-controlled lode system occurring in the northern Xiaoqinling terrane, Huaxiong Block, Qinling Orogen. This paper reports a new Sr–Nd–Pb isotope dataset obtained for ore sulfides and the hostrocks within the Taihua Supergroup, in an attempt to constrain the source of the ore-forming fluids from a new dimension. 16 sulfide samples yield I Sr ratios of 0.70470–0.71312, with an average of 0.70854; εNd(t) values between −13.5 and −18.1, with average of −15.1; and (206Pb/204Pb)i, (207Pb/204Pb)i and (208Pb/204Pb)i ratios of 17.033–17.285, 15.358–15.438, and 37.307–37.582, with averages of 17.162, 15.405, and 37.440, respectively. 5 gneiss samples from the Taihua Supergroup yield I Sr ratios of 0.70947–0.73201, averaging 0.72294; εNd(t) values of −20.0 to −31.1, averaging −25.1; and (206Pb/204Pb)i, (207Pb/204Pb)i, (208Pb/204Pb)i ratios of 17.127–18.392, 15.416–15.604 and 37.498–37.814, with averages of 17.547, 15.470 and 37.616, respectively. These data show that the ore sulfides have less radiogenic Sr–Nd–Pb isotope systematics than the hostrocks, and suggest that the ore-forming fluids, which interacted with the wallrocks to form ores, must be sourced from a depleted mantle or a depleted, subducted oceanic slab. In combination with the spatial scenario and geochemical signatures of the Triassic magmatites and mineral systems, we argue that in the Triassic the Mianlue Ocean was not completely closed, and that the northward oceanic plate subduction still survived along the Mian-Lue suture, which caused the Late Triassic magmatism and associated mineralization in Qinling Orogen, including the Au–Mo Dahu deposit. [Copyright &y& Elsevier]

Abstract: The Qiyugou gold deposits, Henan Province, are hosted in breccia pipes within the Xiong''er terrane (Qinling Orogen), on the southern margin of the North China Craton. In these deposits three paragenetic assemblages have been recognized: an early K-feldspar–epidote–quartz–pyrite; a middle quartz-polymetallic sulfide; and a late quartz–carbonate±adularia. In this paper we review and interpret fluid inclusion and stable and radiogenic isotopic data of host rocks and ores. Fluid inclusions in quartz and calcite include water-rich, CO2-rich, and daughter crystal-bearing. The CO2-rich and daughter mineral-bearing fluid inclusions are common in the early-stage quartz and absent in the late-stage quartz and calcite which only contain water-rich fluid inclusions. Accordingly, the early-stage ore-fluids are magmatic in origin and characterized by high-temperature (>350 °C), high-salinity (>30 wt.% NaCl equiv.), and are CO2-rich. Fluid-boiling in the middle ore stage resulted in CO2-release, decreasing oxygen fugacity and rapid precipitation of ore materials. The late stage fluids, have low-temperature, low-salinity, are CO2-poor and lack daughter minerals. These fluids are probably sourced from meteoric water. H–O–C isotope systematics confirm that, the ore–fluid system evolved from magmatic to meteoric. The carbon and lead isotope ratios indicate that the Meso-Neoproterozoic sequence south of the Xiong''er terrane was the likely source of the ore-forming materials. The Qiyugou breccia-pipes and their associated gold ores were emplaced during an extensional regime following a transition from collision to rifting tectonics, linked to collision and subduction of the Yangtze plate beneath the North China Craton. Geochronological studies show that Mesozoic magmatism in the region occurred between the Triassic and Cretaceous. The Triassic to Jurassic magmas were mostly derived from partial melting of ancient crust, whereas the Cretaceous magmas show juvenile signatures, indicating mantle-derived components. Processes of fragmentation of lithospheric roots, crustal and lithospheric thinning, extension and rifting were probably associated with the subducting Pacific (Izanagi) plate. These crust–mantle geodynamic processes were responsible for the development of anorogenic granitic melts that interacted with the Meso-Neoproterozoic volatile-rich sedimentary successions, producing a flow of gas-rich hydrothermal fluids that resulted in the emplacement of the Qiyugou auriferous breccia pipes. We conclude that the Qiyugou gold deposits are intrusion-related explosive breccia pipe-type that evolved from hypothermal through mesothermal to epithermal. [Copyright &y& Elsevier]

Abstract: Seventy skarn-type gold deposits, including 1 super-large, 19 large and 24 medium-sized, are known from different geotectonic units of China. They contain a total resource of approximately 1000 t of gold (625 t in South China), and account for 20% of China''s gold reserves. These skarn deposits are sited in collisional orogenic belts, fault-controlled magmatic belts and reactivated cratonic margins. All of the Chinese skarn gold provinces were affected by Phanerozoic collisional orogenesis. The timing of the metallogenic events and the spatial–temporal distribution of the Chinese skarn gold deposits indicates that they were formed during ore-forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen, and not to subduction systems as is commonly advocated for porphyry copper systems around the Pacific Rim. [Copyright &y& Elsevier]

[Display omitted] • Five ore-forming stages are recognized in the Yechangping porphyry-type orebodies. • Fluid characteristics suggest that Yechangping is a Dabie-type porphyry Mo deposit. • The process of fluid immiscibility, boiling, and mixing cause the mineralization. • Magmatic-hydrothermal system of Yechangping deposit extends to depths of 10 km. Dabie-type porphyry Mo deposits have recently emerged as a distinct subtype of porphyry Mo deposits, but questions remain about the magmatic-hydrothermal fluid evolution in the formation of this type of deposit. Here, well-developed fluid inclusions in quartz phenocrysts, unidirectional solidification textures (UST), and quartz veins in the Yechangping porphyry Mo-W deposit, Qinling Orogen, completely record the magmatic-hydrothermal mineralization process. The characteristics and evolution of the ore-forming fluid in this deposit are investigated through petrography, microthermometry, and laser Raman spectroscopy analysis of fluid inclusions at different stages in order to improve our understanding of the fluid evolution in the genesis of Dabie-type porphyry Mo deposit. The mineralization process in the porphyry-type orebody can be divided into three periods and five stages: (1) magmatic period, including quartz phenocrysts (stage 1); (2) magmatic-hydrothermal transition period, including UST (stage 2); (3) hydrothermal period, including quartz ± K-feldspar veins (stage 3), quartz-molybdenite veins (stage 4), and calcite ± quartz veins (stage 5), where stage 4 is the main ore-forming stage. The fluid inclusions in quartz and calcite can be recognized as pure CO 2 (PC type), CO 2 -H 2 O (C type), daughter minerals-bearing (S type), and H 2 O (WV type and WL type) inclusions. Ore-forming fluid is initially high temperature, high salinity, and CO 2 -rich, belonging to the H 2 O-CO 2 -NaCl (±KCl) system suggested by the fluid inclusions identified in UST. The estimated lithostatic pressures of stage 1 range from 284–362 MPa, corresponding to depths of 10.3 to 13.2 km, which are consistent with the formation depth of the underlying magma chamber. The presence of UST in stage 2 indicates that the magma was saturated with fluid. Due to the fluctuating pressure (123–260 MPa) in UST of stage 2, fluid immiscibility happened soon after the fluid exsolution and is inferred to occur between the CO 2 -rich and aqueous phases. Then, the fluid boiling and mixing occurred in stages 3 and 4, respectively. The estimated pressures of stage 4, which represent the main mineralization stage, range from 45–175 MPa, corresponding to depths of 4.6–6.4 km. The immiscibility of CO 2, along with the fluid mixing-induced cooling and dilution, caused an increase in p H and a decrease in oxygen fugacity, which serves as a crucial mechanism for Mo mineralization at the Yechangping deposit. Stage 5 is characterized by low temperature (185–309 °C) and low salinity (2.9–8.7 wt% NaCl equiv.). The primary high temperature, high salinity, CO 2 -rich fluids, and relatively deep ore-forming depth suggest that the Yechangping deposit is a typical example of a Dabie-type porphyry deposit. The characteristics of fluids and the variation in estimated depth at each stage record the evolutionary process of a magmatic-hydrothermal system extending to depths of nearly 10 km in the Yechangping deposit. [ABSTRACT FROM AUTHOR]

The Tianmugou molybdenum (Mo) deposit is a newly discovered porphyry deposit in the Dabie Shan of eastern China. The Mo-mineralization is spatially and genetically related to the Tianmushan granite batholith, and mainly occurs as thin molybdenite-bearing pegmatite dykes and numerous hydrothermal veins, with the development of potassic alteration, silicification, sericitization, propylitization, and fluoritization. The Tianmushan batholith is composed of outermost fine-grained K-feldspar granite (Phase 1), medium-grained K-feldspar granite (Phase 2), coarse-grained biotite monzogranite (Phase 3), porphyritic granite (Phase 4), and innermost fine-grained K-feldspar granite (Phase 5). Zircon crystals from the biotite monzogranite yield a weighted average 206 Pb/ 238 U age of 123.0 ± 0.8 Ma, but those from the porphyritic granite do not yield a good age because of their high contents of Th, U and Pb. Seven molybdenite samples from the ores yield individual Re–Os isotopic ages of 120.5 ± 1.7 Ma to 122.5 ± 1.9 Ma, which are slightly younger than the U–Pb age for the biotite monzogranite. These ages constrain the ore-forming magmatic-hydrothermal activity at the Tianmugou Mo deposit that took place during the post-collisional tectonism subsequent to the collision between the Yangtze and North China continents, consistent with the 142–111-Ma regional Mo mineralization event in Dabie Shan. The biotite monzogranite and porphyritic granite have high contents of SiO 2 , K 2 O and Al 2 O 3 , and low contents of TiO 2 , MgO and CaO, showing a metaluminous to peraluminous high-K calc-alkaline affinity, with significant depletion in Eu, Ba, Sr, P and Ti, and enrichment in Rb, Th, U, Nb, Ta, Hf and Y. The rocks have high initial 87 Sr/ 86 Sr ratios of 0.73546–0.89204, and negative εNd( t ) values of − 11.6 to − 11.0, with T DM2 (Nd) of 1.81–1.86 Ga. Their ( 206 Pb/ 204 Pb)t, ( 207 Pb/ 204 Pb)t and ( 208 Pb/ 204 Pb)t are 17.337–17.554, 15.450–15.465 and 37.992–38.147, respectively. The Sr-Nd-Pb isotopic signatures indicate that the causative granitic intrusions for the Tianmugou deposit mainly originated from partial melting of the Qinling Group during Early Cretaceous post-collisional tectonic extension. The Tianmugou Mo deposit belongs to a collisional- or Dabie-type porphyry Mo system. [ABSTRACT FROM AUTHOR]

The large Zankan iron deposit is hosted in the pre-Devonian Bulunkuole metamorphic complex within the Taxkorgan terrane, West Kunlun Orogen, southwestern China. The deposit is unique for its mineral association of magnetite, pyrite and anhydrite in variable proportions, forming disseminations, banded and massive ores. Magnetite grains from the ores show variable contents of many elements, such as Mg (182–1167 ppm), Al (198–2691 ppm), Ti (898–1677 ppm), V (112–8468 ppm), Mn (821–4695 ppm), Co (7–26 ppm), Ni (1–29 ppm), Zn (5–45 ppm), and Ga (20–62 ppm). The high Al, Ti and V contents are interpreted to result from relatively reduced, Al–Ti-rich seafloor hydrothermal activities. The magnetite coexisting with sulfide has lower Co concentrations (7.8–13 ppm) than those not coexisting with sulfides (Co = 22–26 ppm). Compositional variations of magnetite possibly related to oxygen fugacity, temperature and coexisting minerals. The δ 56 Fe values in magnetite range from − 0.3 to 0.5‰, suggesting a changing hydrothermal precipitation environment. The Fe isotope fractionation between pyrite and magnetite (△δ 57 Fe py-mag ) range 0.2–1.1‰, implying a high-temperature crystallization (≥ 236 °C). The δ 56 Fe ratios in pyrite range 0.6–0.8‰, higher than the coexisting magnetite. Such a negligible variation of positive δ 56 Fe values indicates that the pyrite possibly originated from a slow precipitation or a transformation from FeS (mackinawite), which was induced by the rise of atmospheric oxygen at ~ 0.6 Ga. Integrating the data obtained from the studies including regional geology, ore geology, magnetite composition and Fe isotope geochemistry, we conclude that the Zankan Fe deposit was formed from an Early Cambrian seafloor hydrothermal system developed in a volcanic arc caused by southward subduction of Proto-Tethyan plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zircon U-Pb ages record two phases of granitic magmatism of 159 and 145 Ma. • Molybdenum and W are enriched in porphyry by prolonged fractionation and high f O2. • Scheelite petrography and compositions reflect mechanisms of Mo-W mineralization. • Porphyry-skarn Mo-W systems may be controlled by magmatic sources and wall rocks. Eastern Qinling Orogen is the largest Mo province in the world, hosting nine giant Mo deposits. Four giant Mo deposits contain economic W mineralization, while the mechanism of W mineralization remains unclear. The Yechangping deposit is a representative porphyry-skarn Mo-W deposit, with four paragenetic stages of prograde skarn, retrograde skarn, polymetallic sulfides and carbonate stage. Magmatism at Yechangping includes early barren monzogranite porphyry at 159.0 ± 1.5 Ma and late ore-related granite porphyry at ca. 145 Ma, and the latter porphyry shows a higher magmatic fractionation than the early barren monzogranite porphyry. Both barren and ore-related porphyries have similar high magma oxidation states, which may efficiently extract Mo during partial melting and hinder subsequent molybdenite crystallization until the porphyry-skarn Mo mineralization. Three types of scheelites are distinguished by their texture, paragenetic relationship and geochemistry, including Sch-1a in the retrograde skarn stage, and Sch-1b and Sch-2 in the polymetallic sulfides stage. Scheelite displays decreasing MoO 3 contents from 7.01–51.59 % in Sch-1a, through 3.15–17.51 % in Sch-1b, to 0–1.51 % in Sch-2. The decreasing MoO 3 contents in scheelite are attributed to the transformation of dominant Mo-bearing phases, i.e., from retrograde skarn stage powellite to polymetallic sulfides stage molybdenite. We suggest that the Mo-W mineralization is triggered by the decreasing oxygen fugacity, p H, and temperature, supported by thermodynamic modeling. In addition, the precipitation of fluorite and destabilization of fluorine complexes may have also promoted the Mo-W mineralization. Zircon Hf isotopes yielded ε Hf (t) values of −14.9 to −7.5 and T DM2 ages of 1671–2147 Ma, indicating that Yechangping porphyries were primarily sourced from the ancient basement of the Huaxiong Block, with additional contribution from the North Qinling Accretionary Belt. Skarn W mineralization in the southern part of Huaxiong Block may be controlled by both magmatic fertility and carbonate wall-rocks. [ABSTRACT FROM AUTHOR]

The Keketale Pb–Zn deposit is located in the Devonian volcanic-sedimentary Maizi basin of the Altay orogenic belt. The mineralization at Keketale is hosted in marbles and deformed volcanic tuffs and biotite–garnet–chlorite schists, folded into a series of overturned synclines formed in multiple deformation events. Keketale contains economic amounts of Pb (0.89Mt @ 1.51wt.%), Zn (1.94Mt @ 3.16wt.%) and Ag (650t @ 40g/t). Detailed petrographic studies have defined two main generations of sulfide development. The banded pyrite of the early Stage A is commonly stratiform, with minor galena, sphalerite and chalcopyrite. Stage B is characterized by a large amount of polymetallic sulfides including pyrrhotite, chalcopyrite, sphalerite and galena, with minor pyrite hosted in quartz veins. Three types of fluid inclusions (FIs), including mixed carbonic-aqueous (C-type), pure carbonic (PC-type) and aqueous (W-type), have been recognized in quartz of stage B. The C-type FIs have homogenization temperatures of 150–326°C and salinities of 0.2–16.6wt.% NaCl equivalent. The PC-type FIs are dominated by CO2 with minor CH4 and N2 and have initial ice-melting temperatures of −57.5 to −56.7°C, CO2 homogenization temperatures of 11–14.1°C. The W-type primary FIs were completely homogenized at temperatures of 124–359°C with salinities of 5.0–14.6wt.% NaCl equivalent. Such CO2-rich fluid inclusions are consistent with those discovered in orogenic-type deposits in the Altay area and elsewhere. Muscovite separates from the polymetallic quartz veinlets of stage B yield a well-defined 40Ar/39Ar isotopic plateau age of 259.33±2.56Ma, with an isochron age of 259.62±2.65Ma. This age is coeval with the closure of the Paleo-Asia Ocean and reactivation of the Ertix Fault system. LA-ICP-MS analyses of two generations of pyrite indicate that the banded pyrite of stage A is relatively depleted in metallic elements and contains low contents of Cu (0.39ppm), Ag (0.20ppm), Au (below the detection limits), Pb (17.43ppm) and Zn (14.38ppm); whereas the pyrite in quartz–polymetallic sulfide veinlets of the stage B is relatively rich in metallic elements, e.g., Cu (2.56ppm), Ag (3.07ppm), Au (0.01ppm), Pb (1047ppm) and Zn (1136ppm). The trace amounts of Cu, Pb, Zn, Au and Ag are interpreted to have been initially locked in the lattice of type-A pyrite, and then liberated and precipitated as micromineral inclusions with type-B pyrite during subsequent metamorphism and deformation. Two key factors are considered vital to the formation of economic ores of the Keketale Pb–Zn deposit, namely the original Devonian banded pyrite formed in a VMS system and subsequent Permian deformation and metamorphic processes that liberated Cu, Pb, Zn, Au and Ag from the lattice of type-A pyrite to form galena, sphalerite and chalcopyrite with minor muscovite in quartz veinlets. The model provides a new interpretation of VMS Pb–Zn deposit occurring in back-arc basin environments followed by collision, and new insights into the unique regional Fe–Cu–Pb–Zn–Au mineralization in the Altay orogenic belt. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Dongguashan quartz-diorite stock was built by multiple magma pulses. • Early magma pulse was guided by inherited NE-SW-trending structure in country rock. • Late magma pulse emplacement was assisted by regional extensional regime. • Eastward magma emplace might control location of skarnization in stock eastern sideable 1. We present a study on the Dongguashan quartz diorite stock which is the largest Early Cretaceous intrusion associated with skarn-porphyry polymetallic ore deposit in the Tongling Ore Cluster, Middle-Lower Yangtze Metallogenic Belt in East China. The Dongguashan quartz diorite show massive texture without obvious foliation, and intrusive contact was locally observed inside of the stock. The anisotropy of magnetic susceptibility (AMS) results of the stock show two distinct groups. The Group I (G-I) is dominated by NE-SW-striking magnetic foliation with variably oriented magnetic lineation. The Group II (G-II) that intruded into G-I is characterized by steep NW-SE-striking magnetic foliation and lineation, which are parallel to the vein-like orebody developed in the stock. The 3D geometrical modelling of the stock displays a triangular shape in plan-view with an eastward bulge and irregular stock boundary in the eastern side and the contact surface is steeper in the west than that in the east, denoting that the stock was constructed with an eastward magma accretion trend. Furthermore, the Dongguashan quartz diorite has a wide range of composition and geochronological data, suggesting a multiple magma pulses emplacement model. Accordingly, we propose that the Dongguashan stock was constructed by at least two stages magma pulses. The earlier stage magma pulses intruded along the NE-SW-striking pre-emplacement structures in the country rock and partly intruded into the lithological and mechanical discontinuous interfaces which yielded the stratabound skarn orebody. The eastward magma accretion produced a highly deformed and longer heated country rock on the eastern side of the stock, favoring the orebody development along the eastern stock-country rock contact interface. The late-stage magma pulse and the parallelism among the trend of magnetic foliation of G-II, extensional structure and vein-like orebody suggest that the vein-type orebodies may controlled by both magma emplacement and regional tectonics. [ABSTRACT FROM AUTHOR]

Abstract: The Wulasigou Cu deposit occurs as veins controlled by a NW-trending structure in a Devonian volcano-sedimentary basin of the Altay orogenic belt, Xinjiang, China. Igneous and sedimentary rocks exposed in the area have undergone greenschist-facies metamorphism. The ore-forming process can be divided into early, middle, and late stages, represented by, respectively, pyrite-quartz, polymetallic sulfide-quartz, and carbonate–quartz veins, veinlets, and/or replacement bodies. The early veins were deformed and brecciated during a compressional or transpressional event. The middle-stage veinlets filled fractures in the early-stage vein and alteration assemblages, and are undeformed, suggesting a tensional shear setting. The late-stage veinlets are mainly open-space fissure fillings that cut veins and replacement bodies formed in the earlier stages. Four types of fluid inclusions (FIs), including aqueous (W-type), mixed carbonic-aqueous (M-type), purely carbonic (C-type) and daughter mineral-bearing (S-type), have been identified in copper-related quartz and calcite from the Wulasigou deposit. The early-stage quartz contains M- and W-type primary FIs that completely homogenized at temperatures of 322–412°C with low salinities of 0.9–6.5wt.% NaCl equiv. In contrast, the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 101–234°C, and salinities of 0.9–2.9wt.% NaCl equiv. This indicates that the metallogenic system evolved from CO2-rich, metamorphic to CO2-poor, through input of meteoric fluids. All four types of FIs can only be observed in the middle-stage minerals, where they show evidence of vein formation during an episode of fluid immiscibility. These FIs homogenized at temperatures ranging mainly from 230 to 347°C, with salinities clustering 2.7–10.2wt.% NaCl equiv for the W-, M- and C-types, and 34.7–38.2wt.% NaCl equiv for the S-type, respectively. The metal precipitation resulted from a decrease in copper solubility during the fluid immiscibility episode. The estimated trapping pressures for the middle-stage fluids are 1.55–3.55kbar, suggesting an alternating lithostatic-hydrostatic fluid-system, controlled by fault-valve activity at a depth of 13–15.5km. Muscovite separates from the middle-stage polymetallic-quartz veinlets yield a well-defined 40Ar/39Ar isotopic plateau age of 219.41±2.10Ma, and an 39Ar/36Ar - 40Ar/36Ar isochron age of 219.73±2.17Ma. This age postdates the final Paleo-Asia Ocean closure (at ca. 250Ma) by about 30Ma, and indicates that the Cu mineralization at Wulasigou has occurred in the Triassic continental collision setting. Hence, the Wulasigou Cu deposit may be the first example of orogenic lode Cu deposits formed in accretionary orogeny or continental collision. [Copyright &y& Elsevier]

Abstract: The Yuchiling Mo deposit, East Qinling, China, belongs to a typical porphyry Mo system associated with high-K calc-alkaline intrusions. The pure CO2 (PC), CO2-bearing (C), aqueous H2O-NaCl (W), and daughter mineral-bearing (S) fluid inclusions were observed in the hydrothermal quartz. Based on field investigations, petrographic, microthermometric and LA-ICP-MS studies of fluid inclusions, we develop a five-stage fluid evolution model to understand the ore-forming processes of the Yuchiling deposit. The earliest barren quartz±potassic feldspar veins, developed in intensively potassic alteration, were crystallized from carbonic-dominant fluids at high temperature (>416°C) and high pressure (>133MPa). Following the barren quartz±potassic feldspar veins are quartz-pyrite veins occasionally containing minor K-feldspar and molybdenite, which were formed by immiscible fluids at pressures of 47–159MPa and temperatures of 360–400°C. The fluids were characterized by high CO2 contents (approximately 8mol%) and variable salinities, as well as the highest Mo contents that resulted in the development of quartz-molybdenite veins. The quartz-molybdenite veins, accounting for >90% Mo in the orebody, were also formed by immiscible fluids with lower salinity and lower CO2 content of 7mol%, at temperatures of 340–380°C and pressures of 39–137MPa, as constrained by fluid inclusion assemblages. After the main Mo-mineralization, the uneconomic Cu-Pb-Zn mineralization occurred, as represented by quartz-polymetallic sulfides veins consisting of pyrite, molybdenite, chalcopyrite, digenite, galena, sphalerite and quartz. The quartz-polymetallic sulfide veins were formed by fluids containing 5mol% CO2, with minimum pressures of 32–110MPa and temperatures of 260–300°C. Finally, the fluids became dilute (5wt.% NaCl equiv) and CO2-poor, which caused the formation of late barren quartz±carbonate±fluorite veins at 140–180°C and 18–82MPa. It is clear that the fluids became more dilute, CO2-poor, and less fertile, with decreasing temperature and pressure from quartz-pyrite to late barren veins. Molybdenite and other sulfides can only be observed in the middle three stages, i.e., quartz-pyrite, quartz-molybdenite and quartz-polymetallic sulfide veins. These three kinds of veins are generally hosted in potassic altered rocks with remarkable K-feldspathization, but always partly overprinted by phyllic alteration. The traditional porphyry-style potassic–phyllic–propylitic alteration zoning is not conspicuous at Yuchiling, which may be related to, and characteristic of, the CO2-rich fluids derived from the magmas generated in intercontinental collision orogens. Among the fluid inclusions at Yuchiling, only the C-type contains maximum detectable Mo that gradationally decreases from 73ppm in quartz-pyrite veins, through 19ppm in quartz-molybdenite veins, and to 13ppm in quartz-polymetallic sulfide veins, coinciding well with the decreasing CO2 contents from 8mol%, through 7mol%, to 5mol%, respectively. Hence it is suggested that decreasing CO2 possibly results in decreasing Mo concentration in the fluids, as well as the precipitation of molybdenite from the fluids. This direct relationship might be a common characteristic for other porphyry Mo systems in the world. The Yuchiling Mo deposit represents a new type Mo mineralization, with features of collision-related setting, high-K calc-alkaline intrusion, CO2-rich fluid, and unique wall-rock alterations characterized by strong K-feldspathization and fluoritization. [Copyright &y& Elsevier]

Abstract: The Nannihu Mo–W deposit, located in the Henan Province of China, is a giant porphyry deposit formed in the Qinling Orogen during the Jurassic continental collision between the North China and Yangtze Cratons. Mo–W mineralization is associated with the Nannihu porphyritic monzogranite, occurring as numerous stockwork veinlets in the altered wallrocks and the causative porphyry. Both the porphyry stock and wallrocks underwent intense hydrothermal alteration, ranging outwardly from potassic to phyllic alteration, and to carbonation zones with increasing distance from the intrusion. The hydrothermal ore-forming process can be divided into four stages characterized by veinlets, from early to late: (1) quartz+potassic feldspar±molybdenite±pyrite; (2) quartz+molybdenite veins containing minor pyrite and chalcopyrite; (3) quartz+polymetal sulfide; and (4) quartz+carbonate+fluorite. Most of the ores are formed during stages 2 and 3. Four types of fluid inclusions (FIs) are distinguished in this study based on petrographic and microthermometric criteria, i.e. pure CO2, NaCl–H2O, CO2–H2O and daughter mineral-bearing fluid inclusions. All of the four types of FIs can be observed in the hydrothermal quartz formed in stages 1, 2 and 3; while the stage 4 minerals contain only NaCl–H2O fluid inclusions. Fluid inclusions of stage 1 are mainly homogenized between 350 and 460°C, with salinities ranging from 5.7 to 17.9wt.% NaCl equiv. The stage 2 FIs yield homogeneous temperatures of 300–380°C and salinities of 3.5–16.9wt.% NaCl equiv. FIs of stage 3 are homogenized between 250 and 370°C, with salinities of 1.8–14.3 and 28.6–39.1wt.% NaCl equiv. FIs of stage 4 are homogenized at temperatures of 115 to 265°C, yielding salinities of 0.5 to 1.2wt.% NaCl equiv. Daughter minerals, such as halite, chalcopyrite and some unknown minerals, are frequently present in stage 3 FIs, which probably represent a reducing and oversaturated fluid-system resulting from fluid-boiling. The daughter mineral-bearing FIs coexist with vapor- and liquid-rich NaCl–H2O FIs that have contrasting salinities. These FIs are homogenized in divergent ways at similar temperatures, suggesting that fluid boiling took place in stages 2 and 3. The estimated pressures range from 70 to 270MPa in stage 1, through 30–150MPa in stage 2, to 30–85MPa in stage 3, corresponding to a depth of no less than 3km. In other words, the ore-forming fluids are characterized by high temperature, high salinity, high fO2 and high CO2 content; and fluid-boiling resulted in CO2 release, fO2 decrease and ore mineral precipitation. We suggest that the CO2-rich fluid is a distinctive feature of porphyry systems developed in continental collision setting, in transitional compressional to extensional regime, contrasting to the CO2-poor NaCl–H2O fluids observed in volcanic arcs. [Copyright &y& Elsevier]

Abstract: East Qinling is the largest porphyry molybdenum province in the world; these Mo deposits have been well documented. In West Qinling, however, few Mo deposits have been discovered although granitic rocks are widespread. Recently, the Wenquan porphyry Mo deposit has been discovered in Gansu province, which provides an insight into Mo mineralization in West Qinling. In this paper we report Pb isotope compositions for K-feldspar and sulfides, S isotope ratios for sulfides, the results obtained from petrochemical study and from in situ LA-ICP-MS zircon U-Pb dating and Hf isotopes. The granitoids are enriched in LILE and LREE, with REE and trace element patterns similar to continental crust, suggesting a crustal origin. The Mg# (40.05 to 56.34) and Cr and Ni contents are high, indicating a source of refractory mafic lower crust. The ε Hf(t) values of zircon grains from porphyritic monzogranite range from −2.9 to 0.6, and from granitic porphyry vary from −3.3 to 1.9. The zircons have T DM2 of 1014 to 1196Ma for the porphyritic monzogranite and 954 to 1224Ma for the granitic porphyry, implying that these granitoids were likely derived from partial melting of a Late Mesoproterozoic juvenile lower crust. The Pb isotope compositions of the granitoids are similar to granites in South China, showing that the magma was sourced from the middle–lower crust in the southern Qinling tectonic unit. The Pb isotopic contrast between the Mo-bearing granitoids and ores shows that the Pb in the ore-forming solution was derived from fractionation of a Triassic magmatic system. δ34S values of sulfides are between 5.02 and 5.66‰, similar to those associated with magmatic-hydrothermal systems. LA-ICP-MS zircon U-Pb dating yields crystallization ages of 216.2±1.7 and 217.2±2.0Ma for the granitoids, consistent with a previously reported molybdenite Re-Os isochron age of 214.4±7.1Ma. This suggests that the Mo mineralization is related to the late Triassic magmatism in the West Qinling orogenic belt. In view of these geochemical results and known regional geology, we propose that both granitoid emplacement and Mo mineralization in the Wenquan deposit resulted from the Triassic collision between the South Qinling and the South China Block, along the Mianlue suture. Since Triassic granitoid plutons commonly occur along the Qinling orogenic belt, the Triassic Wenquan Mo-bearing granitoids highlight the importance of the Triassic tectono-magmatic belt for Mo exploration. In order to apply this metallogenic model to the whole Qinling orogen, further study is needed to compare the Wenquan deposit with other deposits. [Copyright &y& Elsevier]

[Display omitted] • Five types of tourmaline have been identified in the Donggebei Mo deposit. • The tourmalines belong to alkali group, changing from shorl to dravite. • The δ11B values imply magmatic-hydrothermal fluid origin. • Chemical variations of tourmaline trace the ore-forming processes. Tourmaline is a chemically and mechanically stable mineral that commonly occurs in hydrothermal mineral systems, and has been used to trace the mineralization processes of many genetic types of ore deposits. Here we apply tourmaline chemistry and isotopic composition to trace the genesis of a porphyry Mo system for the first time. Tourmaline is widespread in the Donggebi Mo deposit in East Tianshan, NW China, where it occurs in five distinct associations: type PG disseminated in the porphyritic granite, TS as hydrothermal tourmalite in the country rocks (strata), V1 in quartz-molybdenite vein, V2 in quartz-polymetallic sulfide vein, and V3 quartz-calcite-fluorite vein. All the tourmaline types belong to the alkali group, with the V3 being schorl and the other types being dravite and schorl. The PG-type tourmalines partly inherit the features of the porphyritic granite, and are rich in F, Na, Al and Sc, and poor in Fe, Mg, Ca, Sr, Ba, Pb, V and Mo compared to the other types. They have low Fe3+ concentrations and low Fe3+/(Fe3++Fe2+) ratios, suggesting a reducing fluid system. They also display weaker Eu-depletion (with an average (Eu/Eu*) N value of 0.96) than the porphyritic granite, and are considered to be the products of interaction of the reducing fluids and the granites. The average (Eu/Eu*) N values of tourmalines decrease from 6.66 of type V1, 5.65 of type V2, to 4.80 of type V3, indicating that the fluids became progressively less reducing along with sulfide precipitation. The δ11B values of the tourmalines range between −15.9 ‰ and −12.5 ‰, resembling those of S-type granites or clastic sediment-sourced hydrothermal fluids. The tourmaline grains in our study do not display any remarkable δ11B variation from the cores to rims, indicating that the δ11B values of the fluids and their source were relatively constant. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pyrite and arsenopyrite display complex textural and compositional evolution. • Pyrite incorporates significant amounts of refractory Au, up to 1.02 wt.%. • Arsenopyrite incorporates significant amounts of refractory Au, up to 1.75%. Apy3 was formed at 325–385 °C based on arsenopyrite geothermometer. Abstract The Axi deposit is the largest low-sulfidation epithermal gold deposit in Chinese Western Tianshan, Central Asian Orogenic Belt. In this contribution, combined petrological observations, electron microprobe analysis (EMPA) and X-ray backscattered electron images (BSE) have been conducted on Fe-S-As minerals to reveal their textural and compositional evolution. Pyrite and arsenopyrite are ubiquitous. Their texture and composition show gradual changes with time. Four generations of pyrite can be identified, named Py1, Py2, Py3 and Py4 from early to late. The coarse-grained, euhedral to subhedral Py1 (mostly 100–300 μm) from the quartz-chalcedony stage is the earliest, and predates gold mineralization. Sometimes they contain silicate and arsenopyrite (Apy1) inclusions. Compositionally, they are enriched in Pb (up to 0.60 wt%), but depleted in As (0.06–7.61 wt%, mostly <0.30 wt%) and Au (0.01 wt%–0.25 wt%, mostly <0.10 wt%). Subhedral to anhedral Py2 grains (50–1000 μm) coexist with other sulfides such as chalcopyrite, sphalerite, galena and tetrahedrite in the quartz-polymetallic sulfides stage. They are unusually rich in Au (with a mean value of 0.06 wt%), Ag (with a mean value of 0.04 wt%), Cu (with a mean value of 0.21 wt%) and As (with a mean value of 3.06 wt%), implying a syn -mineralization feature. Subsequent Py3 occurs as very fine-grained disseminations of euhedral crystals (10–50 μm) in quartz-polymetallic sulfides stage and carbonate-quartz stage. They display clear oscillatory zoning and contain arsenopyrite (Apy3), sphalerite and Sb-Te mineral inclusions. Their Au content vary greatly from 0.02 wt% to 1.02 wt%, with corresponding As content varying from 0.07 wt% to 8.28 wt%. The post-mineralization Py4 crystals (30–5000 μm) mainly occur as foliated, sheaf, or radiaxial aggregates in carbonate-quartz stage. They have the lowest Au (with a mean value of 0.04 wt%), As (with a mean value of 0.32 wt%), Co (with a mean value of 0.04 wt%) and Ni (with a mean value of 0.04 wt%) concentrations, although dramatically high S contents (with a mean value of 52.72 wt%). Correspondingly, there are three generations of arsenopyrite: Apy1 (20–50 μm) and Apy3 (3–15 μm) mainly occur as inclusions in Py1 and Py3, respectively, whereas the latest Apy4 (<5–60 μm) can occur either as serrated grains surrounding Py4 or overgrowth Py1 and Py3, or as individual euhedral to sub-euhedral grains. They also contain considerable, but much higher Au contents than pyrite, with the values of 0.6 wt%–1.1 wt% for Apy1, 0.18 wt%–1.32 wt% for Apy3 and 0.50 wt%–1.75 wt% for Apy4, respectively. Besides, they also contain considerable amounts of trace elements such as Co, Zn, Pb, Sb and Se. Arsenopyrite geothermometer constrains the ore-forming temperature responsible for Apy3 formation to 325–385 °C. Our result reveals that significant invisible gold accommodated by sulfides is the main cause of refractory ores at the Axi deposit. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Zankan Fe deposit in West Kunlun, China is a seafloor hydrothermal system. • Zankan deposit has a unique mineral association of magnetite, pyrite and anhydrite. • Variable δ34S values show that both igneous rocks and seawater are sulfur sources. • High-temperature hydrothermal fluid and seawater supplied the ore-forming fluid. Abstract The Zankan iron deposit (Taxkorgan County, Xinjiang) is a recently discovered large Fe deposit in western China. The deposit is hosted in the Bulunkuole metamorphic complex in the Taxkorgan terrane of the West Kunlun Orogen. The ores are uniquely composed of magnetite, pyrite and anhydrite with variable contents, and show massive, disseminated and banded styles. The ores contain widely varying (Al 2 O 3 + TiO 2) (0.28–5.48 wt%), Zr (3.0–83 ppm) and Hf (<0.2–2 ppm), indicating a terrigenous clastic material input. Detrital contamination is minor, as demonstrated by poor correlations of Y/Ho ratio vs. Zr, Th, Hf and Al 2 O 3 contents, as well as Zr vs. TiO 2. The ores contain seawater-like LREE depletion, positive La and Y anomalies, and occasional Eu enrichment, which suggest hydrothermal contributions. In addition, three samples show relatively high REY (604–1254 ppm), negative Eu anomalies (Eu/Eu∗ PAAS = 0.36–0.96) and MREE enrichment (Sm/Yb PAAS = 1.25–2.81), suggesting a probable fluvial input and shallow precipitation. The δ34S ratios range widely (3.2–32.8‰) and show an alternating and/or mixing source of two end-members. The seawater sulfate may have been an indispensable end-member, and the other end-member may have been the volcanic host rocks in the Bulunkuole Complex, which has likely contributed the ore-forming metals. Integrating evidence from regional geology, ore geology, and geochemistry, we conclude that the Zankan Fe deposit was the result of an Early Cambrian seafloor hydrothermal system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Kuruer Cu-Au deposit is hosted by volcanic and volcano-sedimentary rocks. • It displays porphyry-type hydrothermal alteration and mineralization. • The ore-forming fluids are magmatic water mixed with meteoric water. • The deposit is a transition from high sulfidation epithermal to porphyry system. Abstract Western Tianshan along the southwestern margin of the Central Asian Orogenic Belt is well-endowed with epithermal and porphyry Au deposits. The Kuruer Cu-Au deposit, recently discovered in the eastern part of Western Tianshan, was considered as a high sulfidation epithermal deposit. However, our geological, fluid inclusion and stable isotopic studies indicate that it actually formed in transition from high sulfidation to porphyry. The host rocks include the Dahalajunshan Formation volcanic and volcano-sedimentary rocks such as andesite, rhyolite, ignimbrite and tuff. Cu-Au mineralization mainly occurs as quartz-dominated stockworks or disseminations, with abundant pyrite and chalcopyrite and minor galena and sphalerite. Gold occurs as invisible phase in sulfides. Hydrothermal alteration includes a silicic core, surrounded by phyllic alteration and peripheral propylitic alteration. Based on field observations, paragenetic and crosscutting relationship, the mineralization process can be roughly divided into three stages. The early stage is characterized by the assemblage of quartz + pyrite + chalcopyrite while the middle stage contains quartz and chalcopyrite at absence of pyrite. The late stage is characterized by calcite ± quartz ± chlorite ± chalcopyrite veins. Fluid inclusions at the early stage are mainly liquid-rich aqueous and CO 2 -rich inclusions and minor vapor-rich aqueous and solid-bearing inclusions. Their homogenization temperatures and salinities can be up to 420 °C and 39 wt.% NaCl eq., respectively, indicating that the initial ore-forming fluids are high temperature, high salinity, H 2 O-CO 2 -NaCl systems. In the middle stage, there are only liquid-rich aqueous inclusions, with homogenization temperatures and salinities of 130–190 °C and 0.18 to 10.7 wt.% NaCl eq., respectively. Liquid-rich aqueous inclusions in the late stage display much lower temperatures and salinities, ranging from 110 to 130 °C and 0.18–2.7 wt.% NaCl eq., respectively. Obtained δD H2O and δ18O H2O values of quartz from the middle stage are −98 to −107‰ and −2.1 to 0.74‰, respectively. The δ34S values of 9 chalcopyrite samples range from −10.2 to −2.4‰, with an average of −4.1‰. We conclude that the initial ore-forming fluids are magmatic in origin, and further cooled and diluted by mixing with meteoric water. Intensive fluid boiling and mixing facilitated hydrothermal alteration and mineralization. [ABSTRACT FROM AUTHOR]

The giant Donggebi porphyry Mo deposit is located in the Jueluotage metallogenic belt of Eastern Tianshan, Xinjiang, Northwest China. Mo mineralization mainly occurs as numerous veinlets in the altered sandstone wall-rocks, with the development of potassic, phyllic, argillic and propylitic alteration assemblages outward from a buried porphyritic granite stock. Zircon crystals from the buried porphyritic granite yield a weighted average 206 Pb/ 238 U age of 236 ± 2.2 Ma (MSWD = 1.2, 1σ, n = 17), slightly older than the molybdenite Re–Os isotope ages of 231–234 Ma, suggesting that the Donggebi porphyry Mo deposit was formed in the Triassic, post-collisional tectonism subsequent to termination of the Paleo-Asia Ocean. The samples from porphyritic granite show high contents of SiO 2 , K 2 O and Al 2 O 3 , low contents of TiO 2 , MgO and CaO, and peraluminous high-K calc-alkaline to shoshonite affinity, with obvious LREE enrichment and negative Eu anomalies. They have high initial 87 Sr/ 86 Sr ratios of 0.70618 to 0.70821, ε Nd( t ) values of 0.60 to 1.62, and T DM2 (Nd) ages of 0.88 to 0.96 Ga. Their ( 206 Pb/ 204 Pb)t, ( 207 Pb/ 204 Pb)t and ( 208 Pb/ 204 Pb)t values are 17.122–18.577, 15.493–15.574, and 37.887–38.006, respectively. Zircons from the porphyritic granite yield εHf(t) values of − 1.58 to 4.82, and T DM2 (Hf) ages of 0.96–1.36 Ga. These geochemical and isotopic data imply that the Donggebi porphyritic granite originated mainly from partial melting of lower continental crust derived from a depleted mantle. The Donggebi Mo deposit is unique based upon the crustal source for the causative porphyry, the distal position of mineralization, and the previously revealed CO 2 -rich ore-forming fluids, and thus belongs to the collisional- or Dabie-type porphyry deposits as exemplified by the Qiane'chong and Yaochong deposits in Dabie Shan, the Donggou deposit in Qinling Orogen, China. [ABSTRACT FROM AUTHOR]

The Kalatag Cu–Zn–Au district contains a number of economically important Cu deposits in eastern Tianshan in Xinjiang, NW China. Due to the lack of precise mineralization ages, the metallogenesis of this area has long been a matter of debate. In this study, chalcopyrite Re–Os isotope methods are used to date the South Meiling Cu–Zn and Hongshi Cu deposits in the eastern part of Kalatag area. The South Meiling Cu–Zn deposit is hosted in volcanic-sedimentary rocks of the Late Ordovician to Early Silurian Daliugou Formation. The deposit consists of two parts: a concordant massive sulfide ores and discordant vein-type ores located in the footwall strata. The principal ore minerals are pyrite, chalcopyrite, sphalerite, minor tetrahedrite, galena and pyrrhotite. Gangue minerals include quartz, sericite and barite, and minor chlorite, plagioclase and carbonate minerals. The Hongshi Cu deposit represents a hydrothermal vein system hosted in the mafic volcanic rocks of Daliugou Formation. The orebodies are associated with quartz veins and controlled by subsidiary faults of the Kalatag fault. The ore-forming process can be divided into the early, middle and late stages and is characterized by quartz–pyrite, quartz–chalcopyrite–pyrite and quartz–carbonate–gypsum veins, respectively. Re–Os analyses of chalcopyrite from the South Meiling Cu–Zn deposit yield an isochron age of 434.2 ± 3.9 Ma and initial 187 Os/ 188 Os ratio of 0.647 ± 0.098 (MSWD = 0.59). Re–Os analyses of chalcopyrite from the Hongshi Cu deposit yield an isochron age of 431.8 ± 2.7 Ma and initial 187 Os/ 188 Os ratio of − 0.165 ± 0.075 (MSWD = 0.77). Since chalcopyrite is the primary copper mineral, we interpret these isochron ages as the timing of Cu mineralization, based on field geology and petrographic evidence. These results suggest that the Re–Os ages presented here provide, for the first time, a direct constraint on an early Paleozoic Cu mineralization event of the eastern Tianshan Orogen. The high initial 187 Os/ 188 Os ratios (0.647 ± 0.098) ratio of ~ 434 Ma chalcopyrite from the South Meiling deposit suggest that the metal was sourced from a two end-member mixing of crust and mantle materials. Moreover, we propose that the VMS mineral system and hydrothermal vein system of the Kalatag district were related to the south-dipping subduction of the Kalamaili oceanic plate during the Late Ordovician–Silurian. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Xiaoqinling area is widespread of the ∼2.3 Ga Xiaohe granitic plutons. • The REE patterns and Sr/Y and δEu values of granites vary with source depth of magmas. • The Xiaohe granite is A-type granite emplaced in an extensional setting. • The Xiaohe granite was intruded by the ∼1.8 Ga granite. The early Paleoproterozic is generally considered as a worldwide tectonic quiescent period. It is unusual that widespread early Paleoproterozoic magmatism has been identified in the North China Craton (NCC), especially in the Xiaoqinling Terrane at the southern NCC. The Xiaohe granite occurs along the southern margin of the Xiaoqinling Terrane and intrudes the lower portion of the Taihua Supergroup (gneisses). Previous data suggest the emplacement time of the Xiaohe granite ranging from the early to late Paleoproterozoic, leaving a controversy over 500 Ma. To accurately constrain the age, genesis and tectonic setting of the Xiao granite, we have carried out a comprehensive study and here present new petrographical, geochronological, and isotope and element geochemical data. It is confirmed that the Xiaohe granite is dominated by the ca. 2.3-Ga monzogranite and locally intruded by the Guijiayu granites at 1.82 ± 0.05 Ga. Three samples from the Xiaohe granite yield consistent zircon U − Pb ages of ca. 2.3 Ga, and ɛ Hf (t) values showing mixing of juvenile and recycled continental crust sources. The Xiaohe granite are characterized by high SiO 2 (70.7–79.6 %) and high alkali (5.67–10.15 %), belong to calc-alkaline to shoshonite series and show weak peraluminous feature with A/CNK values around 1.1. Its geochemical characteristics are similar to those of A-type granites formed involcani arc or syn- to post-collision tectonic settings. Samples also display eastward decrease of Sr/Y, (La/Yb) N and δEu values, and weakening REE fractionation, indicating an eastward increase of plagioclase in residue during partial melting of the crust, and the magma sources become shallow eastwardly. Hence it is concluded that the Xiaohe granite was formed in a widespread granitic event associated with continental collision or terrane amalgamation. [ABSTRACT FROM AUTHOR]

Tourmaline is widespread in the Baiganhu W–Sn deposit, Xinjiang Province, NW China. In this study, electron microprobe analysis reveals that tourmaline in the Baiganhu deposit belongs to the alkali and X-site group with low Ca and moderate X site vacancy, all beyond the confines of schorl–dravite series, with Na/(Na + Ca) and Fe/(Fe + Mg) ratios ranging from 0.769 to 0.965 and 0.518 to 0.822, respectively. In chemical discrimination diagrams, the tourmaline samples plot in the fields of Li-poor granite, associated with Al-saturated metapelites and metapsammites. The tourmaline cores are depleted in Mg, Ca, Ti, but enriched in Al and Fe compared to the rims. Substitution mechanisms for the compositional variations are dominantly due to MgFe − 1 , □Al(NaFe) − 1 , □Al(NaMg) − 1 , and AlO(Fe − 1 (OH)) − 1 exchange vectors. The δ 11 B values of the tourmalines range from − 12.9 to − 7.9‰, with a slight variation between cores and rims, which reflect a common boron source, and also indicate that the tourmaline crystallized during a single magmatic-hydrothermal event related to monzogranite. Tourmaline is a valuable prospecting indicator of W–Sn mineralization. [ABSTRACT FROM AUTHOR]

The Caixiashan giant carbonate-hosted Zn–Pb deposit (~ 131 Mt@ 3.95% Zn + Pb) formed by replacement of dolomitized marble, with stratiform massive and breccia bodies is located near the base of the Proterozoic Kawabulake Group limestone and marble. It is one of the largest carbonated-hosted massive sulfides Zn–Pb ore deposits in Northwest China to have been discovered in recent years. Abundant pyrite occurs in dolomitized marble, along fractures in dolomitized clasts in the host rocks and filling cracks in the host rock. Locally, colloform or framboidal pyrites are observed in the early period and sometimes replaced by the later sphalerite. The sulfide assemblage of the main ore stage is characterized by massive or disseminated sphalerite and galena, with less pyrite than the earlier stage, and minor pyrrhotite. Galena occurs as small veins cutting the early-formed sphalerite. Dolomite and calcite are the main gangue minerals that co-precipitated with these sulfides. Tremolite and quartz alteration commonly overprints the orebodies. According to the crosscutting relationships and the different mineral associations within the host rocks and ore bodies, three stages are recognized at Caixiashan, i.e., syn-sedimentary pyrite (stage I), pyrite alteration, sphalerite–carbonate and galena–pyrite–carbonate (stage II-1, stage II-2 and stage II-3, respectively) and magmatic/metamorphic reworking (stage III). Calcite and quartz crystals are important host minerals among the three hypogene stages (stages I–III, although quartz mainly occurred in stage III). Stage I contains only aqueous inclusions (W-type), which were homogenized from 110 to 236 °C (main range of 138–198 °C and average at 168 °C; main range = average ± σ) and the salinities are from 0.5 to 16.5 (main range of 5.1–15.1 with average of 10.1) wt.% NaCl eqv. In the pyrite alteration of stage II-1 the W-type fluid inclusions homogenized from 175 to 260 °C (main range of 210–260 with average of 235) and the salinities range from 8.5 to 22.4 (main range of 16.7–20.1 with average of 18.4) wt.% NaCl eqv. In the main Zn–Pb mineralization stage (stage II-2–3), four types of fluid inclusions were identified an aqueous phase (W-type), a pure carbon phase (PC-type), a carbon phase containing (C-type) and mineral bearing inclusions (S-type). The W-type fluid inclusions of stage II-2–3 homogenized at 210 to 370 °C (main range of 253–323 and average at 270) and the salinities range from 5.9 to 23.1 (main range of 13.3–20.3 with average at 16.8) wt.% NaCl eqv.; C-type homogenized at 237 °C to 371 °C and the salinities range from 6.4–19.7 wt.% NaCl eqv.; S-type fluid inclusions homogenized at 211 to 350 °C and daughter minerals melted between 340 and 374 °C during heating, indicating a salinity range of 42 to 44 wt.% NaCl eqv. PC-type fluid inclusions with homogenization temperatures of CO 2 phase show large variation from 7.4 °C to 21.2 °C. Laser Raman analyses show that CH 4 , CO 2 and SO 4 2 − coexist in the main mineralization stage fluids. The magmatic/metamorphic reworking stage only contains W-type fluid inclusions which yield homogenized between 220 and 360 °C (main range of 251–325 and average at 288), with salinities ranging from 1.7 to 23.0 (main range of 14.3–20.0 and average at 18.8) wt.% NaCl eqv. The textural features, mineral assemblages and fluid geochemistry suggest that the Zn–Pb ores were formed through hydrothermal convection of hot marine waters along the faults and fractures resulting in metal (Zn, Pb and Fe) enriched stratiform orebodies. Subsequent rapid precipitation of sulfides was triggered by sulfate (SO 4 2 − ) thermal reduction with the CH 4 preserved in sedimentary rocks and early stage I pyrite bodies. This process occurred at moderate temperatures ( ca . 270 °C). Higher-temperature magmatic hydrothermal alteration overprinted the orebodies, but only provided a minor contribution to the mineralization. [ABSTRACT FROM AUTHOR]

The genesis of polymetallic deposits in southern Altay, NW China has been disputed between a syngenetic seafloor hydrothermal process and an epigenetic orogenic-type mineralization. The Dadonggou Pb–Zn deposit occurs as NW-trending veins in the Devonian Kangbutiebao Formation volcanic-sedimentary sequence in the Kelan basin, southern Altay. A set of integrated zircon U–Pb and biotite 40 Ar/ 39 Ar geochronological data were applied to constrain the forming ages of the ores and their country rocks. Three samples of host volcanic rocks yielded weighted mean 206 Pb/ 238 U ages of 397.1 ± 4.5 Ma, 391.7 ± 3.6 Ma and 391.1 ± 4.2 Ma, respectively, indicating that the Kangbutiebao Formation was deposited in a Devonian back-arc basin. Two biotite samples separated from the Pb–Zn-containing quartz veins yielded 40 Ar/ 39 Ar plateau ages of 205.9 ± 2.1 Ma and 204.3 ± 2.2 Ma, respectively, which represent the age of the Pb–Zn mineralization that is attributed to the closure of the Kelan back-arc basin and the Late Triassic orogeny. Combining the available geological and geochronological data, this contribution outlines the successive evolution from the development of a Devonian back-arc basin to the Late Triassic post-subduction orogeny, and proposes that the Dadonggou Pb–Zn deposit is an epigenetic orogenic-type deposit placed in the Late Triassic orogeny. [ABSTRACT FROM AUTHOR]

[Display omitted] • Taishanmiao was constructed by three pulses of magmatism at 125, 123 and 116 Ma. • The latest porphyritic syenogranite induced Mo mineralization at Zhuyuangou. • The highly fractionated I-type granite results from partial melting of ancient crust. • Small porphyry can concentrate Mo from batholith and then effectively deposit it. The Qinling Orogen is well known for its huge Mo resource. The porphyry Mo deposits are associated with small granite porphyries, albeit great batholiths accommodate limited Mo mineralization. In this study, detailed geochemical, isotopic, and geochronological studies were carried out to constrain the petrogenesis of the Taishanmiao batholith and time framework of magmatism and associated Mo mineralization at Zhuyuangou. Zircon geochronology reveals gradually decreasing emplacement ages, from 124.8 ± 1.0 Ma for the medium- to coarse-grained syenogranite, through 122.8 ± 1.4 Ma for fine- to medium-grained syenogranite, to 115.1 ± 0.95 Ma for porphyritic syenogranite. The last two phases hosted the Zhuyuangou Mo mineralization with a molybdenite Re-Os isochron age of 117.7 ± 1.0 Ma. Major and trace element features support highly fractionated I-type affinity for Taishanmiao. Zircon Lu-Hf isotopic studies yield ε Hf (t) values of −19.6 − -8, and two-stage Hf model ages (T DM2) of 1679–2408 Ma. It thus supports ancient continental crust, especially Taihua Supergroup and Xiong'er Group, as the primary source. Compared to the source rock, the low Mo concentrations of the batholith are attributed to the massive fluid flux that contributes to the formation of the Zhuyuangou and Donggou deposits. Small porphyries can effectively concentrate exsolved fluids and metal compared with great batholith. Their shallow emplacement depths result in greater temperature/pressure/composition gradient with the wall rocks, higher cooling rate, more fractures or even breccia, and fluid boiling and mixing, facilitating intensive hydrothermal alteration and mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] Western Tianshan along the southwestern Central Asian Orogenic Belt is well-endowed with epithermal and porphyry Au-Cu deposits. The Kuruer Cu-Au deposit, recently discovered in the eastern part of Western Tianshan, represents a transition from a high-sulfidation epithermal to a porphyry system. In this contribution, we explored the capacity of chalcopyrite to record direct mineralization time and fluids evolution in the Kuruer deposit, by presenting Re-Os isotopic data and the concentration range of 16 trace elements obtained through LA-ICP-MS. The chalcopyrite Re-Os isochron age of 256 ± 12 Ma (MSWD = 2.6) is comparable within error with the U–Pb age of the ore-causative albite porphyry which demonstrates a Permian porphyry-epithermal system instead of the previously proposed Carboniferous epithermal mineralization. The initial 187Os/188Os ratio of 0.81 ± 0.17 for chalcopyrite implies mixing between crust and mantle. Both pyrite and chalcopyrite can host trace elements in considerable amounts, where pyrite primarily hosted Co, As, Au, V, and Bi, but chalcopyrite concentrated more Zn, Cd, In, Sn, Sb, Mo. The study also highlighted systematic variation of trace element concentrations and Cd/Zn ratios in chalcopyrite and pyrite that can be powerful indicators of fluid phase separation and fluid mixing with meteoric water. [ABSTRACT FROM AUTHOR]

Abstract: To understand the processes and timing of their formation, six non-sulfide Zn–Pb ore deposits were investigated in the Moroccan High Atlas. Sulfide and non-sulfide ores are hosted in Lower Jurassic reefal to para-reefal limestone. Zn (Pb) carbonates, Zn silicates and associated hydrated phases directly replace the stratabound primary ore bodies or fill cavities along fractures related to the Atlasic compression. Field observation has been complemented by a multidisciplinary approach (e.g. XRD, Raman, SEM, EPMA) for the mineralogical characterization. All six ore deposits present similar paragenesis revealing three successive stages for ore deposition: 1) formation of the protore sulfides, 2) early supergene weathering with formation of Zn–Pb-bearing carbonates and iron oxi-hydroxides and 3) late supergene weathering with deposition of Zn-carbonates, Zn-silicates and hydrated phases. Direct replacement of primary sulfides is accompanied by precipitation of zinc non-sulfide minerals in cavities or internal sediments filling. The proposed three-step scenario can be placed within the tectonic evolution of the Moroccan High Atlas belt. Deposition of primary sulfides is contemporaneous with opening of the Tethyan and Atlantic oceans. During the Tertiary, intracontinental deformation has given rise to the High Atlas fold-and-thrust belt and to regional uplift. As a result, Zn–Pb sulfides, hosted in carbonates experienced oxidation under an arid climate to form karst-related Zn–Pb non-sulfide ore bodies. [Copyright &y& Elsevier]

• The Qi189 porphyry gold deposit is a collisional-type porphyry ore deposit. • The Qi189 gold system was formed during 130–127 Ma. • The ore sources involve the crustal material, with a minor mantle component. • Mineralization and related magmatism occurred in post-collisional setting. The Qi189 gold deposit is a recently discovered porphyry system in the Qiyugou Orefield, located in the northeastern Qinling Orogen along the southern margin of North China Craton. The orebodies are hosted in the porphyritic granite emplaced in the Taihua Supergroup. Three molybdenite and five pyrite samples from the ores yield Re–Os isochron ages of 129.5 ± 2.8 Ma and 127.5 ± 8.2 Ma, respectively, which are coincident with the zircon U–Pb age of the porphyritic granite within analytical error (128.6 ± 0.8 Ma). Zircon grains from the post-ore quartz monzonite yield weighted mean 206Pb/238U age of 124.7 ± 0.6 Ma (n = 31, 1σ, MSWD = 0.23). These ages constrain that the Qi189 gold system was formed in the period of 130–127 Ma. The porphyritic granite and quartz monzonite show high-K calc-alkaline affinity, enrichment of LREE and LILE, depletion of HREE and HFSE, and negligible Eu anomaly. Zircon grains show negative ε Hf(t) values of −20.7 to −14.9, with T DM2 (Hf) ages of 2.49–2.13 Ga. This indicates that the Qi189 porphyry system originated from a source mixed by the materials from the North Qinling Accretion Belt and the basement of North China Craton, with minor contribution from the mantle, and developed under a post-collisional tectonic setting. [ABSTRACT FROM AUTHOR]