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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]

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 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]

[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]

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]

[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 • 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]

[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]

• 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]