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The Yinachang Fe-Cu-Au-U-REE deposit is located in the Kangdian region at the southwestern margin of the Yangtze Block. This contribution presents petrological, geochronological, whole rock geochemical, and Rare Earth Elements (REE) geochemistry of zircons of gabbro and diorite dykes associated with the Yinachang Fe-Cu-Au-U-REE deposit, aiming to constrain the age of the mineralisation and help refine our understanding of the tectonic setting of the region. Zircons from diorite have a Palaeoproterozoic U-Pb age of 2014 ± 30 Ma, and zircons from the gabbro could not be dated because they are metamict, having a high concentration of uranium. The ca. 2014 Ma age of the zircons in the diorite indicates that the southwestern part of the Yangtze Block is partly synchronous with the Columbia Supercontinent. Geochemically, the diorite and gabbro are enriched in large-ion lithophile elements (LILEs) such as Rb and U, and depleted in high-field-strength elements (HFSEs) such as Nb, P, Ti, Ba, and Sr. The diorite is enriched in light REEs (LREEs) and has a slight to negligible Eu anomaly, which are characteristic of ocean-island basalts containing mantle-derived high potassic calc-alkaline rocks. In contrast, the gabbro is weakly enriched in LREEs and has a slightly negative Eu anomaly similar to those of potassic calc-alkaline enriched mid-ocean-ridge basalt. The average combined REE content of zircons from the gabbro is 19401 ppm and is significantly higher than that of the zircons from the diorite averaging 1020 ppm. This indicates that the gabbro is closely related with the REE mineralisation at the deposit. The geochemistry of the diorite indicates that it formed at the continental margin of a volcanic-arc. It also indicates that the magmatic rocks in the region have a possible mantle plume origin contaminated by crustal material and located at a transitional zone between a rift and an ocean-continent tectonic setting.

The Wurinitu W–Mo deposit is located in the Erlian-East Ujimqin metallogenic belt in the Great Xing’an Range, NE China. Tungsten and molybdenum mineralization generally occurs as veins in quartz hosted by the Middle to Lower Ordovician wall rocks or as disseminations in the Early Cretaceous monzogranite intrusions. Fluid inclusion studies and multiple isotope analyses, provide systematic evidence to determine the evolution of the hydrothermal fluids, the source of metals and fluids, as well as mineral precipitation mechanisms, which are significant for the magmatic-hydrothermal system but are poorly understood. Three types of fluid inclusion assemblages (FIAs), including L (liquid-rich two-phase FIAs), V (vapor-rich two-phase FIAs), and L-V (liquid–vapor two-phase FIAs), have been identified in quartz veins from the W-mineralization (I), Mo-mineralization (II), and quartz – carbonate (III) stages at Wurinitu. The ore-forming fluids evolved from a high- to moderate-temperature and moderate- to low-salinity H2O–NaCl ± CO2 system in the W- and Mo- mineralization stages to a low-temperature and low-salinity H2O–NaCl system in the quartz-carbonate stage; they were trapped at temperatures of ∼365 °C, ∼266 °C, and ∼198 °C. The results of hydrogen and oxygen isotope analyses (δ18OH2O = −4.0 to +7.7‰; δDH2O = −116 to −92‰) indicate that the stage I fluids dominantly originated from magmatic water, and the stages II and III show addition of meteoric water. Sulfur (δ34SVCDT = 1.9–4.0‰) and lead isotope values (206Pb/204Pb = 18.099–18.728, 207Pb/204Pb = 15.527–15.616, and 208Pb/204Pb = 38.019–38.465) suggest that the ore metals in the hydrothermal fluids were derived from the granitic magma. All these observations reveal that (1) the Wurinitu W–Mo deposit is a magmatic-hydrothermal ore system, (2) W- and Mo- mineralization occurred under lithostatic pressure of 203–294 bars, and hydrostatic pressure of ∼102 bars, respectively, and (3) fluid boiling and mixing with meteoric water might be the key factors controlling the large-scale ore deposition at Wurinitu.

The Hardat Tolgoi Ag-Pb-Zn deposit is located in the Erenhot-East Ujimqin polymetallic metallogenic belt, on the western part of the Great Xing’an Range, Inner Mongolia, northeast China. The Ag-Pb-Zn veins are mainly hosted by the argillaceous siltstone and feldspar quartz sandstone of Aobaotinghundi Formation, which show close genetic relationship with the granitoids at Hardat Tolgoi (i.e., biotite granite, syenogranite, and monzogranite). New LA-ICP-MS zircon U-Pb dating yielded the emplacement ages of 196.1 ± 5.8 Ma for biotite granite, 192.3 ± 6.0 Ma for syenogranite, and 194.8 ± 1.7 Ma for monzogranite, respectively, indicating that they were formed in the Early Jurassic. Geochemically, these granitoids are characterized by high SiO2, Na2O + K2O, and low MgO and TiO2 concentrations, belonging to high-K calc-alkaline series. They exhibit relatively flat REE patterns, with pronounced negative Eu anomalies (EuN/EuN* = 0.004–0.015), enriched in LREEs and LILEs (e.g., Rb, U, and Pb), and depleted in Ba, Sr, Nb, P, and Ti. Zircon in situ Hf isotopic analyses yield positive eHf(t) values ranging from + 5.7 to + 11.8, corresponding relatively young Hf isotopic crustal model ages of 452 to 843 Ma. The granitoid samples have the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.950 to 19.444, 15. 573 to 15.615, and 38.487 to 38.789, corresponding to initial Pb ratios of 18.483 to 18.960, 15.552 to 15.662, and 37.905 to 38.193, respectively, and yield the δ30Si values between − 0.4 and − 0.1‰, similar to the quartz separates (−0.7 to − 0.1‰). The available geochemical and isotopic data imply that the source magma at Hardat Tolgoi was most likely derived from partial melting of juvenile lower crust. Combined our whole-rock geochemical and Hf − Pb − Si isotopic data with regional tectono-magmatic evolution, it is proposed that the Early Jurassic magmatism at Hardat Tolgoi was probably attributed to the southeastward subduction of the Mongol − Okhotsk oceanic plate beneath the Erguna massif, and their generation was favorable to the Hardat Tolgoi Ag-Pb-Zn ore formation.

Late Mesozoic Nantai porphyry Mo deposit is located in the Northern Qinling terrane, eastern China. The intrusions at Nantai include lamprophyre, quartz porphyry, and granite porphyry. Among them, molybdenum mineralization is associated with quartz porphyry and granite porphyry. The ore-bearing porphyries and ore-barren lamprophyres emplaced at ca. 155–146 Ma and ca. 156–146 Ma, respectively. The calculated zircon ΔFMQ values for Nantai felsic and mafic intrusions are –5.0 to +9.1 (an average of + 2.2) and –6.7 to +5.0 (an average of +1.2), which are similar to those of contemporaneous giant Mo deposits in the south margin of the North China Block. The quartz porphyry and granite porphyry are characterized by relatively high SiO2 (73.39–75.49%), K2O (4.24–9.61%), and Rb (291–552 ppm) contents, but low total Fe2O3 (0.13–0.83 wt%), MgO (0.1–0.3 wt%), P2O5 (0.01–0.04 wt%), Sr (22.4–141.0 ppm) and Ba (79.8–1757 ppm) concentrations. These granitic samples have TDMC ages of 2204–1592 Ma, corresponding to negative eHf(t) values of –15.8 to –6.2. Geochemical and zircon Lu-Hf signatures as well as lead isotopic analyses for Nantai granitoids suggest that they belong to the high-fractionated I-type granites and were derived from partial melting of lower continental crust with coeval mantle-derived magma contribution. The lamprophyres show low SiO2 (47.59–49.08%) and Rb (96–120 ppm) contents, whereas they have high Ba (1598–2236 ppm), and Sr (771–990 ppm) concentrations, as well as a lack of negative Eu anomalies. The concentrated eHf(t) values (–0.6 to + 3.3), high (Hf/Sm)PMN and La/Sm ratios, as well as Pb isotopic features, indicate that they were derived from an enriched lithospheric mantle that had been metasomatized by subducted components with some crustal material contribution. Combined with our datasets and previous studies, we suggest that the Nantai porphyry Mo deposit formed in a post-orogenic setting.

The Azhahada quartz vein-type Cu-Bi deposit is located in the Erenhot-East Ujimqin polymetallic metallogenic belt, on the western part of the Great Xing’an Range, Inner Mongolia, northeast China. The Cu-Bi veins are hosted by volcanic and metasedimentary rocks in the Devonian Niqiuhe Formation and Carboniferous felsic intrusions (monzogranite, syenogranite, and granite). Three hydrothermal ore stages (I-III) for Cu-Bi formation at Azhahada have been identified. Chalcopyrite and bismuthinite are the dominant ore minerals and mainly occur in vein stage II (quartz–pyrite ± chalcopyrite ± bismuthinite veins). New LA-ICP-MS zircon U-Pb dating indicates the monzogranite, syenogranite, and granite emplaced between 313.9 ± 1.7 and 308.4 ± 1.5 Ma. The monzogranite, syenogranite, and granite show the same geochemical affinity with I-type granites, which are characterized by high SiO2, K2O, and Al2O3 contents, low MgO, TiO2, and P2O5 contents, negative Eu anomalies (EuN/EuN* = 0.04–0.57), and strong enrichment in Rb, K, Pb, and Nd. Moreover, these granitic intrusions have low Mg# values of 22 to 39, low (87Sr/86Sr)i ratios (0.7023 to 0.7053), eNd(t) values between −0.8 and +0.4, positive eHf(t) values of +1.6 to +10.4, suggesting that their parental magmas were most likely derived from partial melts from the lower crust involving some mantle materials in a post-collisional tectonic setting. Sulfide samples from Azhahada have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios similar to those of granitic intrusions. The silicon isotope compositions of the quartz samples (−0.3 to −0.1‰) are highly consistent with values of the granitic intrusions (−0.4 to −0.1‰), indicating that the silicon was derived from the granitic magma. Combined our whole-rock geochemical and Sr–Nd–Hf–Pb–Si isotopic data with previous investigation of regional tectonic evolutions, we suggest that the Azhahada granitoids genetically associated with the Cu-Bi mineralization were generated by the postorogenic lithospheric extension and magmatic underplating during the Late Carboniferous. A post-collisional extensional event coupled with the rising of hot mantle derived melts triggered partial melting of the lower crust, as well as provided metals (Cu and Bi).

The Baimadong uranium deposit is situated in the Yangtze Craton, SW China, and is one of the most representative carbonate-hosted uranium deposits in China. Uranium mineralization has spatial and genetical relationships with black and red alterations that has been documented by previous studies. However, the signature, source, and evaluation of ore-forming fluids producing the alterations and mineralization remain poorly understood. Fluid inclusions hosted in different generations of hydrothermal calcite have been analyzed in this study, including Cal 1 (pre-ore stage), Cal 2 (early ore stage), and Cal 3 (main ore stage). Three types of fluid inclusions were identified: liquid-dominated biphase, vapor-dominated biphase, and vapor-only monophase. Based on fluid inclusion microthermometry using the FIA method, the fluids associated with Cal 2 are characterized by relatively higher temperature (∼243 ℃) and salinity (5.3 wt% NaCl equiv.) compared with fluids associated with Cal 1 (Th = ∼221 ℃; Salinity = 1.9 wt% NaCl equiv.) and Cal 3 (Th = ∼144 ℃; Salinity = 2.5 wt% NaCl equiv.). The results of stable isotopes (C, O, and S) indicate that the carbon in pre-ore stage fluids was dominantly originated from host marine carbonate rocks (δ13Cfluid-PDB = −3.0 to 0.5 ‰; δ18Ofluid-SMOW = 4.8 to 11.3 ‰), the carbon and sulfur in early ore-forming fluids were mainly derived from the Niutitang Formation with minor from deep crust (δ13Cfluid-PDB = −11.2 to −8.4 ‰; δ18Ofluid-SMOW = 7.9 to 11.4 ‰; δ34Sv-CDT = −11.3 to + 2.1 ‰), whereas the main ore-forming fluids were sourced from meteoric fluids (δ13Cfluid-PDB = −8.6 to −4.9 ‰; δ18Ofluid-SMOW = 0.4 to 8.6 ‰). These results reveal that redox reaction as well as fluid-rock reaction are key factors controlling the large-scale uranium mineralization at Baimadong. Combined with these observations, geological setting, and previous geochemical features, we suggest that tectonic system together with overprinting zone of black and red alterations are indicators for exploration of carbonate-hosted uranium deposit in South China and elsewhere worldwide.

The newly identified Wulandele Mo deposit is located in the western part of the Great Xing’an Range, Northeast China. Molybdenum mineralization generally occurs as veins or disseminations hosted in Permian to Cretaceous granitic intrusions, associated with potassic alteration, silicification, greisenization and propylitic alteration. The ore-forming process can be divided into four stages: quartz ± K-feldspar ± biotite ± pyrite (stage I), quartz + molybdenite ± K-feldspar ± pyrite (stage II), quartz + chalcopyrite ± bornite (stage III), and quartz + carbonate (stage IV). Combined fluid inclusion microthermometry and stable and Pb isotopic compositions are used to constrain the hydrothermal processes and ore genesis of the Wulandele Mo deposit. Fluid inclusion data show four types of fluid inclusion assemblages (FIAs), i.e., L0 (liquid-rich two-phase FIAs), V0 (vapour-rich two-phase FIAs), C (CO2-rich FIAs), and rare L1 (liquid-rich three-phase FIAs with one transparent mineral), but only the former three types of FIAs were analysed. Aqueous and carbonic fluid inclusions occur in quartz veins of stages I and II, and only aqueous inclusions are observed in stages III and IV. Hydrogen and oxygen isotopic compositions of quartz indicate a primarily magmatic origin, and the proportion of meteoric water increased during the ore-forming process. Sulfur (δ34SVCDT = 1.90–4.19‰) and lead isotopes suggest that the ore-forming materials came predominantly from magmatic fluids. The Wulandele Mo deposit was formed by an initially high-temperature, high-oxygen fugacity and CO2-rich fluid system at an estimated depth of ∼0.4 to 3.3 km. Decreases in temperature and fO2 as well as the input of meteoric water were critical factors for sulfide precipitation. Combining the integrated analysis of deposit geology, the fluid evolutionary process, and the ore-forming environment, we suggest that the Wulandele deposit should be classified as a porphyry Mo deposit that was formed in a continental collision orogen during post-collisional extension associated with the consumption of the Mongol–Okhotsk ocean in NE China.

The Chigou copper deposit is situated in the southern part of the Qinling orogenic belt, central China, where quartz diorite and quartz diorite porphyry are associated with porphyry-type copper mineralization. Copper generally occurs as veins, veinlets, and disseminations within-host porphyries. The zircon dates tightly constrain the timing of host porphyries to ca. 149–146 Ma, in agreement with the age of porphyry copper mineralization (146.1 ± 2.8 Ma) constrained by using molybdenite Re–Os dating. The calculated zircon ΔFMQ values for quartz diorite are −9.4 to +9.9 (averaging +4.3). The Chigou granitoids show similar geochemical compositions to high-Barium-Strontium (high Ba-Sr) granites, with high Ba (2256–3717 ppm) and Sr (737–1345 ppm), low Rb (86.2–129 ppm), U (1.9–4.7 ppm), Th (16.2–31.2 ppm), and Nb (11.4–19.1 ppm) concentrations, as well as lack of negative Eu anomalies. The concentrated eHf(t) values (−3.0 to +1.4), moderate Mg# values (41–52), and high (Hf/Sm)PMN and La/Sm ratios, but low Ba/Th, U/Th, and (Ta/La)PMN ratios indicate that ore-forming magmas derived from an enriched lithospheric mantle that had been metasomatized by subducted sediment-derived melts with a minor crustal contribution. Combined with previous studies, we suggest that the Chigou deposit formed in a post-collisional tectonic setting during the Late Jurassic.

The late Paleozoic Tuwu porphyry Cu deposit is located in the Dananhu–Tousuquan arc in Eastern Tianshan, northwest China. In this study, we present new apatite fission track data of the intermediate-felsic intrusions (i.e., diorite porphyry, tonalite porphyry, quartz porphyry, and quartz albite porphyry) from Tuwu, together with inverse thermal modeling and previous study, to reveal exhumation and cooling history. Apatite fission track length analyses indicate that the track annealing type belongs to a transition from the undisturbed basement distribution to the mixed distribution. As a whole, two phases of cooling were recognized from inverse thermal modeling including a protracted slow cooling period with an average cooling rate of 0.32 ℃/Ma during late Cretaceous to Miocene and moderate slow cooling with a cooling rate of 1.89 ℃/Ma from Miocene to the present day. The first phase of cooling can be mainly attributed to a tectonically quiet and arid to semiarid climate whereas the later phases of cooling related to structural activation occurred at ~25–15 Ma in response to a distant effect of the India-Eurasia convergence. In addition, the exhumation rates of Tuwu intrusions from the two stages are 10.7 m/Ma and 63 m/Ma, respectively. The calculated total exhumation thickness at Tuwu is 1.2–2.3 km since late Cretaceous. Based on the integration of stratigraphic sequence, tectonic setting, paleogeographic, geochronology, and low temperature thermochronology study, we suggest that the thick deposition of coal-bearing stratum during the early and middle Jurassic, the extended duration slow cooling and exhumation controlled by arid to semiarid climate, and the differential lifting movement of fault blocks are key factors for preservation of the early Carboniferous Tuwu Cu deposit.

The Yandong porphyry Cu deposit (372 Mt at 0.58% Cu) is located in the center of the eastern Tianshan, Xinjiang, NW China. Multiple-stage hydrothermal activities have resulted in potassic, chlorite-sericite, phyllic, and propylitic alteration in this deposit. The Yandong deposit formed in four stages, i.e., an early quartz ± magnetite ± pyrite stage (I), a quartz + pyrite ± chalcopyrite stage (II), a quartz + chalcopyrite ± pyrite ± molybdenite stage (III), and a late quartz + carbonate stage (IV). Three evolutionary episodes were observed by a detailed fluid inclusion study: (1) Early ore stage (I) fluids were trapped under two-phase conditions, as evidenced by the coexistence of vapor-rich (V-type) inclusions (homogenization temperatures = 410–494 °C, average salinity = 2.2 wt% NaCl equiv), liquid-rich (L-type) inclusions (homogenization temperatures = 311–430 °C, average salinity = 9.5 wt% NaCl equiv) and hypersaline (H-type) inclusions (trapped at ∼300 bars, or a depth of approximately 1 km assuming lithostatic pressure conditions). (2) Main ore stage (II and III) fluid inclusions in quartz were also trapped under two-phase conditions (boiling), as identified by the coexistence of V- and L-type fluid inclusions; L-type inclusions homogenized between 161 and 390 °C (average = 270 °C), with salinities of 1.6–9.9 wt% NaCl equiv (average = 4.9 wt% NaCl equiv) and a depth of ∼1 km (∼100 bars, hydrostatic pressure conditions). (3) Late ore stage (IV) fluids are represented by inclusions in barren quartz–carbonate veinlets, characterized by homogenization temperatures ranging from 123 to 261 °C (average = 179 °C) and salinities between 0.7 and 4.7 wt% NaCl equiv (average = 2.0 wt% NaCl equiv). The initial hydrothermal fluids are characterized by high temperature, high salinity and high oxygen fugacity, belonging to a H 2 O–NaCl system. Hydrogen and oxygen isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and mixed with abundant meteoric waters in the quartz-carbonate stage. Sulfur stable isotope suggests that the ore-forming metals came primarily from the tonalite magma that sourced from the subducted oceanic slab involving some mantle peridotites during ascent. The Cu mineralization of the Yandong porphyry deposit occurred at a shallow crustal level (approximately 1 km), and the fluid boiling or phase separation, decrease of temperature, as well as fluid-rock interaction were likely important factors responsible for metal accumulation and deposition in the magmatic-hydrothermal system.

Iron and Magnesium isotopes have been increasingly widely applied to trace mineralization processes of hydrothermal ore systems. In this study, Fe and Mg isotope compositions of whole-rocks, Fe-bearing minerals (pyrite and ankerite) and Mg-bearing mineral (ankerite) from the Shuangwang gold deposits are investigated to evaluate Fe and Mg isotope behaviors in a gold deposit hydrothermal system and provide new constraints on ore-forming processes. The results showed that the magmatic rocks in the Shuangwang gold deposit (mainly granodiorite , monzonitic granite and lamprophyre) yielded δ 56Fe values of 0.05–0.10‰ and δ26 Mg values concentrated in a narrow range from −0.23‰ to −0.21‰. The gold orebodies are hosted by a NW-trending breccia belt. The wall rock samples (mainly argillaceous limestone, carbonaceous slate and albitite) have higher δ 56Fe values of 0.12–0.29‰ and a wide δ26 Mg range from −2.54‰ to −0.35‰. Pyrite mineral separates show larger δ 56 Fe variation from −0.44‰ to 0.16‰, whereas ankerite has a small δ 56Fe range from −0.15‰ to −0.06 and a δ26Mg range from −0.66‰ to −0.35‰. The crystallization of magmatic rocks incorporated preferentially heavy Fe isotopes, resulting in enrichment of light Fe isotopes in the residual fluid exsolved from magma . The interactions between the wall rocks and the fluids resulted in increase of δ 56Fe value in fluids and resulted in decrease of δ56Fe value in the wall rocks. However, the fluid still had much lighter Fe isotope composition. Thus, Fe in the main ore-forming stages is regarded as derived from the magmatic stock. The opposite enrichment in Fe isotopes between pyrite and ankerite from stages II and III may be explained by equilibrium Fe isotope fractionation in an open system. In addition, the negative δ56Fe value in pyrite from stage IV is indicative of the equilibrium between FeS and dissolved Fe in a closed system. The exsolved fluid from magma has Mg isotope composition similar to magmatic rock, and the water–rock reaction led to the enrichment of heavy Fe isotopes in fluid. The evolutions of Mg isotopes in stages II and III precipitation matched well with the prediction of Rayleigh fractionation model. The Mg from wall rocks contributed to the composition of hydrothermal magnesium isotopes during the formation of the Shuangwang gold deposit. A multi-origin is supposed whereby the main stage ore-forming fluids were derived from metamorphic water and were affected by the influx of magmatic water.

The Fuxing porphyry Cu deposit is a recently discovered deposit in Eastern Tianshan, Xinjiang, northwestern China. The Cu mineralization is associated with the Fuxing plagiogranite porphyry and monzogranite, mainly presenting as various types of hydrothermal veins or veinlets in alerted wall rocks, with potassic, chlorite, phyllic, and propylitic alteration developed. The ore-forming process can be divided into four stages: stage I barren quartz veins, stage II quartz–chalcopyrite–pyrite veins, stage III quartz–polymetallic sulfide veins and stage IV quartz–calcite veins. Four types of fluid inclusions (FIs) can be distinguished in the Fuxing deposit, including hypersline (H-type), vapor-rich two-phase (V-type), liquid-rich two-phase (L-type), and trace amounts of pure vapor inclusions (P-type), but only the stage I quartz contains all types of FIs. The stages II and III quartz have two types of FIs, with exception of H- and P-types. In stage IV quartz minerals, only the L-type inclusions can be observed. The FIs in quartz of stages I, II, III and IV are mainly homogenized at temperatures of 357–518 °C, 255–393 °C, 234–322 °C and 145–240 °C, with salinities of 1.9–11.6 wt.% NaCl equiv., 1.6–9.6 wt.% NaCl equiv., 1.4–7.7 wt.% NaCl equiv. and 0.9–3.7 wt.% NaCl equiv., respectively. The ore-forming fluids of the Fuxing deposit are characterized by high temperature, moderate salinity and relatively oxidized condition. Carbon, hydrogen and oxygen isotopic compositions of quartz indicate that the ore-forming fluids were gradually evolved from magmatic to meteoric in origin. Sulfur and lead isotopes suggest that the ore-forming materials were derived from a deep-seated magma source. The Cu mineralization in the Fuxing deposit occurred at a depth of ~ 1 km, and the changes of oxygen fugacity, decompression boiling, and local mixing with meteoric water were most likely critical for the formation of the Fuxing Cu deposit.

The Baishan porphyry Mo deposit formed in the Middle Triassic in Eastern Tianshan, Xinjiang, northwestern China. Mo mineralization is associated with the Baishan monzogranite and granite porphyry stocks, mainly presenting as various types of hydrothermal veinlets in alerted wall rocks, with potassic, phyllic, propylitic, and fluorite alteration. The ore-forming process can be divided into four stages: stage I K-feldspar–quartz–pyrite veinlets, stage II quartz–molybdenite ± pyrite veinlets, stage III quartz–polymetallic sulfide veinlets and stage IV barren quartz–calcite veins. Four types of fluid inclusions (FIs) can be distinguished in the Baishan deposit, namely, liquid-rich two-phase (L-type), vapor-rich two-phase (V-type), solid-bearing multi-phase (S-type) and mono-phase vapor (M-type) inclusions, but only the stage I quartz contains all types of FIs. The stages II and III quartz have three types of FIs, with exception of M-type. In stage IV quartz minerals, only the L-type inclusions can be observed. The FIs in quartz of stages I, II, III and IV are mainly homogenized at temperatures of 271–468 °C, 239–349 °C, 201–331 °C and 134–201 °C, with salinities of 2.2–11.6 wt.% NaCl equiv., 1.1–10.2 wt.% NaCl equiv., 0.5–8.9 wt.% NaCl equiv. and 0.2–5.7 wt.% NaCl equiv., respectively. The ore-forming fluids of the Baishan deposit are characterized by high temperature, moderate salinity and relatively reduced condition, belonging to a H2O–NaCl ± CH4 ± CO2 system. Hydrogen and oxygen isotopic compositions of quartz indicate that the ore-forming fluids were gradually evolved from magmatic to meteoric in origin. Sulfur and lead isotopes suggest that the ore-forming materials came predominantly from a deep-seated magma source from the lower continental crust. The Mo mineralization in the Baishan deposit is estimated to have occurred at a depth of no less than 4.7 km, and the decrease in temperature and remarkable transition of the redox condition (from alkalinity to acidity) of ore-forming fluids were critical for the formation of the Baishan Mo deposit.

The Yuhai porphyry Cu–Mo deposit is located in the eastern Tianshan orogenic belt of the southern Central Asian Orogen Belt, being an economically important porphyry Cu deposit in NW China. The deposit comprises sixteen buried orebodies that are predominantly associated with dioritic and granodioritic intrusions and are structurally controlled by roughly NE-trending faults. LA-ICP-MS zircon U–Pb dating yielded crystallization ages of 441.6 ± 2.5 Ma (MSWD = 0.03, n = 24) for diorite and 430.4 ± 2.9 Ma (MSWD = 0.04, n = 19) and 430.3 ± 2.6 Ma (MSWD = 0.09, n = 24) for granodiorite. In situ zircon Hf isotope data on a diorite sample show e Hf (t) values from + 8.7 to + 18.6, and two granodiorite samples exhibit similar e Hf (t) values from + 12.6 to + 19.6 and + 12.6 to + 18.9, respectively. The dioritic and granodioritic intrusions belong to a low-K tholeiite series and are relatively enriched in large ion lithophile elements (K, Ba, Pb, and Sr) and are depleted in high field strength elements (Th, Nb, Ta, and Ti). Moreover, these intrusions have high SiO 2 , Al 2 O 3 and MgO contents, low Na 2 O, P 2 O 5 and TiO 2 contents, low Nb/Ta ratios, and slightly positive Eu anomalies. Re–Os dating of molybdenite intergrowth with chalcopyrite yielded a well-constrained 187 Re– 187 Os isochron age of 351.7 ± 2.9 Ma (MSWD = 1.5) with a weighted average age of 355.7 ± 2.4 Ma (MSWD = 0.69) Ma, indicating that the Yuhai Cu–Mo deposit is younger than the intrusion of the diorite and granodiorite. Combined with the regional geological history and above-mentioned data, we suggest that the Yuhai intrusions were most likely derived from the partial melting of mantle components that were previously metasomatized by slab melts formed by the northward subduction of the ancient Tianshan ocean plate beneath the Dananhu–Tousuquan island arc during the Silurian to Carboniferous. Under the subduction-related tectonic setting, the metasomatized mantle magma was emplaced into the shallow crust and induced the formation of the Early Carboniferous Yuhai Cu–Mo deposit, and the hydrothermal fluids of enriched sulfides probably played an important role in the Cu–Mo mineralization.

The Hongshi gold deposit is located in the southwestern margin of the Kanggur–Huangshan ductile shear zone in Eastern Tianshan, Northwest China. The gold ore bodies are predominantly hosted in the volcanogenic metasedimentary rocks of the Lower Carboniferous Gandun Formation and the Carboniferous syenogranite and alkali-feldspar granite. The syenogranite and the alkali-feldspar granite yield SHRIMP zircon U–Pb ages of 337.6 ± 4.5 Ma (2σ, MSWD = 1.3) and 334.0 ± 3.7 Ma (2σ, MSWD = 1.1), respectively, indicating that the Hongshi gold deposit is younger than 334 Ma. The granitoids belong to shoshonitic series and are relatively enriched in large ion lithophile elements (Rb, K, Ba, and Pb) and depleted in high field-strength elements (Nb, Ta, P, and Ti). Moreover, these granitoids have high SiO 2 , Al 2 O 3 , and K 2 O contents, low Na 2 O, MgO, and TiO 2 contents, low Nb/Ta ratios, and slightly positive Eu anomalies. The e Hf (t) values of the zircons from a syenogranite sample vary from + 1.5 to + 8.8 with an average of + 5.6; the e Hf (t) values of the zircons from an alkali-feldspar granite sample vary from + 5.0 and + 10.1 with an average of + 7.9. The δ 34 S values of 10 sulfide samples ranged from − 11.5‰ to + 4.2‰, with peaks in the range of + 1‰ to + 4‰. The above-mentioned data suggest that the Hongshi granitoids were derived from the melting of juvenile lower crust mixed with mantle components formed by the southward subduction of the paleo-Tianshan ocean plate beneath the Aqishan–Yamansu island arc during the Early Carboniferous. The Hongshi gold deposit was formed by post-collisional tectonism during the Permian. The granitoids most likely acted as impermeable barriers that prevented the leakage and runoff of ore-bearing fluids. Thus, the granitoids probably played an important role in controlling gold mineralization.

The Chigou porphyry Cu deposit is located in eastern segment of the Southern Qinling metallogenic belt, on the southern margin of the Central China Orogenic Belt. Copper mineralization is associated with quartz diorite, quartz diorite porphyry and granite porphyry, and occurs as veins, veinlets, disseminations, or veinlet-disseminations within host porphyries. Ore-forming process could be divided into three stages: stage I quartz + K-feldspar + pyrite ± chalcopyrite, stage II quartz + chlorite + chalcopyrite ± molybdenite and stage III quartz + calcite + pyrite. Four types of fluid inclusions (FIs) were distinguished in quartz-bearing veins, including vapor-rich two-phase (V-type), liquid-rich two-phase (L-type), hypersaline (H-type), and CO2-rich (C-type) inclusions. The FIs were homogenized at temperatures of 330–473 °C for stage I, 174–345 °C for stage II, and 128–272 °C for stage III, with corresponding salinities of 3.8–53.6 wt% NaCl equiv., 1.4–15.1 wt% NaCl equiv., and 0.4–7.7 wt% NaCl equiv., respectively. Hydrogen and oxygen isotope data indicate that the ore-forming fluids have a dominant magma signature and were diluted by meteoric water during the late stage. Chalcopyrite and pyrite from different stages record a narrow range of δ34S values from −0.2 to −2‰, consistent with the sulfur isotopic values of typical magmatic-hydrothermal system. Chalcopyrite has similar 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios to those of porphyry intrusions. All stable and radiogenic isotope results reveal that the ore-forming components (i.e. metal and sulfur) were sourced from a magmatic reservoir with some crustal materials. Laser Raman micro spectroscopy data and fluid inclusion analytical results suggest that the Chigou deposit was formed by an initially high- to intermediate-temperature, high-oxygen fugacity (fO2) and CO2-rich fluid system at an estimated depth of 0.7–2.1 km. Decreases in temperature and fO2 as well as fluid boiling were critical factors controlling sulfide precipitation at Chigou.

The Cihai Fe deposit (100 Mt @ 48% Fe) represents an economically important iron deposit in Beishan Terrane, on the southern margin of the Central Asian Orogenic Belt, Xinjiang, northwest China. Many Late Carboniferous to Permian Fe(-Cu) deposits (e.g., Yamansu, Shaquanzi, and Weiya) are also present in adjacent Eastern Tianshan orogenic belt. The Cihai deposit is hosted in mafic dykes (i.e., diabase) and in the contact zone between the mafic intrusion and Mesoproterozoic schist. New zircon U–Pb isotope dating in this study gives a crystallization age of 306.9 ± 3.2 Ma for the ore-bearing diabase, which is the first age-constrained Late Carboniferous mafic magmatic activity at Cihai district. In combination with previous Ar–Ar amphibole dating (281.9 ± 2.2 Ma) for the massive ores, it is suggested that the main iron mineralization and associated mafic magmatic activities occurred at ca. 306–282 Ma, coeval with the large-scale iron mineralization epoch (ca. 324–280 Ma) in Eastern Tianshan. The Cihai diabase samples are LILEs-rich (e.g., K, Rb, and Sr) and HFSEs-depleted (e.g., Nb, Ta, and Ti) calc-alkaline series, and exhibit high Mg# values (51–63), as well as low compatible element concentrations (Ni = 14–53 ppm; Co = 18–43 ppm; and Cr = 26–219 ppm), indicating a mantle wedge source. They have elevated Ba/La and Sr/Nd values with limited Th/Yb ratios (

The Linglong porphyry Cu deposit is located in the Dananhu–Tousuquan Arc Belt, adjacent to the large Tuwu–Yandong Cu deposits in Eastern Tianshan, northwest China. In this study, zircon U–Pb, whole rock geochemistry, and zircon Hf–O isotopic analyses were carried out on the Linglong intrusions (i.e., quartz albite porphyry and diorite porphyry). New SIMS zircon U–Pb dating and previous data indicate that the quartz albite porphyry occurred in the Late Carboniferous (318.6 ± 3.0 Ma), younger than emplacement of the diorite porphyry (338–340 Ma) and tonalite porphyry (332–335 Ma) in this area, as well large-scale copper mineralization (331–335 Ma) in Eastern Tianshan. The geochemistry of the quartz albite porphyry intrusions is consistent with calc-alkaline normal arc magmatism, characterized by high SiO2 (74.82–77.89 wt%), obvious Eu anomalies (0.42–0.52), high Y (21–25.9 ppm) and Yb (2.98–3.67 ppm) concentrations, moderate Mg# values (35–40), but relatively low Sr/Y (6.86–9.52)and low 10,000 Ga/Al values. In situ Hf–O isotopic analyses on zircons show that the quartz albite porphyry rocks have variable eHf(t) (+9.0 to + 13.9) and low δ18O values (4.72 to 5.84‰), suggesting a juvenile lower crust derived composition. However, the diorite porphyry intrusions show features of low SiO2 (57.51–61.12 wt%), minor Eu anomalies (0.82–1.15), strong depletion in high field strength elements (e.g., Nb, Ta, P and Ti), but enrichment in large ion lithophile elements (e.g., Rb, Ba, K and Pb). They also exhibit normal island arc magma geochemical signatures, with high Y (20.9–40.2 ppm), and Yb (2.75–4.64 ppm) concentrations, high Mg# (40–51), and relatively low (La/Yb)N (2.07–4.10) and Sr/Y (5.75–12.13) values, suggesting the melt was derived from the subduction-modified mantle mafic to ultramafic materials. Combined with regional tectonic evolution and our new data, we suggest that the Late Carboniferous magma was generated during the period of the northward subduction of the Paleo-Tianshan ocean plate beneath the Dananhu–Tousuquan island arc.

Microporous gold is common in many Te-Au deposits. Experimental formation and textures of microporous gold have recently been studied. However, few studies have worked on naturally occurring microporous gold. At the Dongping gold deposit, which is one of the most studied Au-Ag-Te deposits in China natural microporous gold is widely distributed in both primary and oxidized ores. This provides a good opportunity to study the textures and the formation of microporous gold in nature. This gold is pseudomorphous in addition to being porous, indicating that it formed via interface coupled dissolution-reprecipitation (ICDR) reactions. Four textures that were not described previously in experiments were observed in samples from this deposit. (1) A hackly interface between the microporous gold and parent calaverite. Te content shows a decreasing trend with increasing distance from the interface. This texture may result from diffusion of excess surface energy as the ICDR reaction moves towards equilibrium. (2) A less-porous band exists in the microporous gold. The band has fewer pores, smaller crystal sizes and similar chemical composition with the surrounding microporous gold. It likely formed due to the fluctuation of the fluid physicochemical conditions (including decreasing temperature, αO2(aq) and increasing pH) that changes the dissolution rate of calaverite. (3) Microporous gold precipitated between quartz and calaverite. As well, gaps developed between gold and remnant calaverite. This texture is derived from catalytic effects of a heterogeneous nucleation or recrystallization process. It is helpful for extraction and aqueous processing of Au-Te ores, and accounts for the phenomenon that quartz can accumulate gold in some hydrothermal gold deposits. (4) Petzite coexists with Ag-bearing microporous gold, indicating that petzite may also decompose to microporous gold under hydrothermal conditions. Calaverite could be dissolved without altered pyrite at high-temperature (>200 °C) conditions, but under weathering conditions, pyrite would be altered first. In primary ores, microporous gold coexists with pyrite and baryte, indicating that it was formed during the late-stage mineralization. In oxidized ores, microporous gold coexists with limonite and baryte, indicating it may have generated during late-stage mineralization and then altered by weathering. Hydrothermal fluids derive from late-stage mineralization may play the main role in the formation of microporous gold compared to weathering processes. This observation also leads us to reappraise the importance of hydrothermal fluids in the weathering dominated ICDR geological processes.

The Kanggur gold deposit is located in the southern margin of the Central Asia Orogenic Belt and in the western segment of the Kanggur–Huangshan ductile shear belt in Eastern Tianshan, northwestern China. The orebodies of this deposit are hosted in the Lower Carboniferous volcanic rocks of the Aqishan Formation and mainly consist of andesite, dacite and pyroclastic rocks. The SHRIMP zircon U–Pb age data of the andesite indicate that the volcanism in the Kanggur area might have occurred at ca. 339 Ma in the Early Carboniferous, and that the mineralization age of the Kanggur gold deposit was later than the age of volcanic rocks in the area. Geochemically, the andesite rocks of the Aqishan Formation belong to low-tholeiite and calc-alkaline series and display relative depletions in high field strength elements (HFSEs; i.e. Nb, Ta and Ti). The δ18Ow and δDw values vary from − 9.1‰ to + 3.8‰ and − 66.0‰ to − 33.9‰, respectively, indicating that the ore-forming fluids were mixtures of metamorphic and meteoric waters. The δ30Si values of 13 quartz samples range from − 0.3‰ to + 0.1‰ with an average of − 0.15‰, and the δ34S values of 18 sulphide samples range from − 0.9‰ to + 2.2‰ with an average of + 0.54‰. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of 10 sulphide samples range from 18.166 to 18.880, 15.553 to 15.635 and 38.050 to 38.813, respectively, showing similarities to orogenic Pb; these values are consistent with those of the andesite from the Kanggur area, suggesting a common lead source. All of the silicon, sulphur and lead isotopic systems indicate that the ore-forming fluids and materials were mainly derived from the Aqishan Formation, and that the host volcanic rocks of the Aqishan Formation probably played a significant role in the Kanggur gold mineralization. Integrating the data obtained from studies on geology, geochronology, petro-geochemistry and H–O–Si–S–Pb isotope systematics, we suggest that the Kanggur gold deposit is an orogenic-type deposit formed in Eastern Tianshan orogenic belt during the Permian post-collisional tectonism.

The Tuwu deposit (557 Mt at 0.58% Cu) is the most typical and economically significant one of several porphyry copper deposits in the Dananhu-Tousuquan Arc Belt near the Turpan-Hami Basin, northwest China. The mineralization occurs as chalcopyrite and minor bornite in quartz-bearing veins and host porphyries (i.e. diorite porphyry and tonalite porphyry), and is closely associated with potassic (e.g. K-feldspar, magnetite, and hematite) and phyllic (e.g. sericite, pyrite, albite and chlorite) alterations. Fluid inclusions were studied in different generations of quartz, defined as QzIA+IB, QzII, QzIII, and QzIV. Four types of fluid inclusions were recognized, namely liquid-rich biphase (L0), vapor-rich biphase (V0) and triphase (V1, with one opaque mineral), as well as brine-rich (B0; with or without an opaque mineral) inclusions. Based on fluid inclusion microthermometry using FIA method, the fluids associated with QzIB (early ore stage) are characterized by relatively high temperatures (306–458 °C) and salinities (50.3–62.1 and 6.5–22.6 wt% NaCl + CaCl2 equiv. for B0 and L0 inclusions, respectively), under lithostatic pressure of 167 to 444 bars (depth of 0.6–1.6 km), and the fluids associated with QzII and QzIII (main ore stage) have progressively decreasing temperatures from 201° to 345 °C, under hydrostatic pressure of about 90 bars (depth of 0.9 km), which induced to large-scale mineralization at Tuwu. Mineralogy and physicochemical calculations suggest that the early stage occurred at alkaline and high-oxidized fluid environment (pH = 9.6 to 11.5; logfO2 = −26.4 to − 24.3), whereas the main ore stage took place at acidic and low-oxidized conditions (pH = 4.0 to 5.0; logfO2 = −30.8). The fluids associated with QzIV (late ore stage) show low homogenization temperatures (