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[Display omitted] • The subducted South China Block metasomatized the subcontinental lithospheric mantle. • Subduction of the Paleo-Pacific Plate hydrated the subcontinental lithospheric mantle. • The gold-related lamprophyres had a high H 2 O and high fO 2 , which are felicitous for gold mineralization. Besides granite porphyries, many mafic dikes also have a close temporal and spatial relationship with orebodies in the BWGB. However, compared with the granite porphyries, no detailed attempt has been made to determine the petrogenesis of these mafic dikes or to elucidate their relationships with the gold mineralization. Here, we present comprehensive bulk-rock geochemical data; pyrite, apatite, and amphibole compositions; Sr-Nd-Pb isotopes, and U-Pb zircon data for the lamprophyres to provide constrains on their petrogenesis, magmatic properties, geodynamic setting, and metallogenic implications. We obtained zircon U-Pb ages, which reveal that the lamprophyres were emplaced ~ 130 Ma. The lamprophyres are characterized by pronounced light rare earth element (LREE) enrichment, heavy rare earth element (HREE) depletions ((La/Yb) N > 10). They also have low SiO 2 (<51 wt%) and high MgO (>4.1 wt%) contents; low Rb/Sr (0.01–0.04), Th/La (0.1–0.12), and Lu/Yb (0.13–0.16) ratios; high Ba/Rb ratios (>18), low Sr-Nd values (87Sr/86Sr(t) = 0.7060–0.7076; ε Nd (t) = –8.8 to –12.5); and a wide range of radiogenic Pb isotopic ratios (206Pb/204Pb(t) = 16.37–17.35), indicating an enriched mantle source metasomatized by the upper crust of the subducted South China Block (SCB). Their low apatite MnO contents and high apatite SO 3 contents, high apatite molar OH/F ratios, and high amphibole Mg* and VIAl* values suggest that the mafic magmas were more highly oxidized and hydrated. Taken together, the lithospheric mantle source was initially metasomatized by the SCB and was further hydrated by the subducted Paleo-Pacific Plate, resulting in a mafic melt with a high H 2 O content and oxygen fugacity value, which are favorable conditions for gold transportation. [ABSTRACT FROM AUTHOR]

• Cretaceous adakite-like and calc-alkaline granitoids occur in the Bengbu-Wuhe area. • Both types of granites are different in magmatic fO 2 , H 2 O-Cl contents, and sources. • The adakite-like rocks record conditions favorable for gold mineralization. Sinistral slip along the Tancheng–Lujiang Fault Zone (TLFZ) during the Mesozoic resulted in an offset of approximately 400 km between the Dabie and Sulu orogens. The Bengbu–Wuhe gold belt (BWGB) represents an extension of the Zhaoyuan–Yexian gold belt to the west of the TLFZ. Early Cretaceous intrusions are widely distributed throughout the BWGB. Gold deposits in the BWGB are commonly associated with intermediate acid dykes that are roughly contemporaneous with mineralization, and some orebodies are hosted in granitoids. This paper investigates granitoids within the BWGB to constrain their petrogenesis, tectonic setting, and metallogenic significance using systematic whole-rock elemental geochemistry, apatite geochemistry, zircon U–Pb dating, zircon Lu–Hf isotopes, and whole-rock Sr, Nd, and Pb isotopes. The timing of Au mineralization (134–113 Ma) in the area is consistent with the age of intrusive adakite-like rocks (130–115 Ma) and normal calc-alkaline granitoids (114–109 Ma). The adakite-like samples are characterized by pronounced enrichment in light rare earth elements (REE), depletion in heavy REE ((La/Yb) N = 30.5–66.2), an absence of Eu anomalies, high Sr contents and Sr/Y ratios, low Y and Yb contents, and fractionated REE patterns ((Dy/Yb) N = 1.22–1.69). They have relatively low Mg# values (38–42) and variable Sr–Nd–Pb–Hf isotopic compositions (87Sr/86Sr(t) = 0.7083–0.7111; ε Nd (t) = −22.2 to −14.9; 206Pb/204Pb(t) = 17.219–18.010; zircon ε Hf (t) = −21.0 to −12.3). These features indicate that the parental magmas of the adakites were derived from partial melting of thickened lower crust of the South China Plate and/or the North China Craton. The normal calc-alkaline granitoids have low Sr/Y (6.0–40.5), La/Yb N (6.8–24.7), and Dy/Yb N (0.90–1.28) ratios, exhibit negative Eu anomalies, and have variable Sr–Nd–Pb–Hf isotopic compositions (87Sr/86Sr(t) = 0.7082–0.7085; ε Nd (t) = −22.7 to −17.7; 206Pb/204Pb(t) = 16.686–16.713; zircon ε Hf (t) = −24.9 to −19.0), indicating they were derived from the middle to lower crust of the North China Craton. Compared with the normal calc-alkaline granitoids, the adakite-like rocks have higher zircon Ce4+/Ce3+, higher apatite SO 3 and lower apatite MnO contents, lower and more variable zircon crystallization temperatures, and higher apatite molar OH/F and Cl/F ratios, indicating that the adakitic magmas were more enriched in volatiles and more highly oxidized. Taken together, field observations and geochemical data suggest that the adakite-like rocks related to the subducted South China Block are the ore-causative rocks. [ABSTRACT FROM AUTHOR]

• Low sulfidation epithermal gold deposit is genetically related to volcanic rocks. • Ore deposition is triggered by the mixing of magmatic fluid and meteoric water. • Low and intermediate sulfidation epithermal gold deposits co-exist at Dongkeng District. Low sulfidation (LS) epithermal gold deposits within the Southeastern China Fold Belt (SCFB) are generally associated with Early Cretaceous volcanism (91–110 Ma). The Shangshangang (SSG) gold deposit (3 t Au @ 2.7 g/t) is proposed to be a LS ore system hosted by Early Cretaceous volcanic-subvolcanic rocks in the Dongkeng Basin (DVB), northern SCFB. Early Cretaceous felsic volcanic-subvolcanic rocks within the DVB possess high-K calc-alkaline and metaluminous to weakly peraluminous signatures. They show rare trace element (REE) and trace element patterns resembling those of Early Cretaceous A-type granites and rhyolites in the SCFB with significantly Eu negative anomalies (Eu/Eu* = 0.1–0.3). These volcanic-subvolcanic rocks are potentially formed by mixing of melts from crust and Early Cretaceous enriched mantle under an extensional tectonic setting. This is indicated by their negative ε Hf (t) values (−8.8 to −5.2), young two-stage Hf model ages (T DM2 = 1.32–1.48 Ga), and variable Sr-Nd isotopic compositions. The epithermal event at SSG is represented by three mineralization stages characterized by four distinct quartz vein types. These are: (1) greyish green crustiform comb quartz veins (type A) and smoky grey fine-grained (<0.5 mm) quartz veins (type B) in the early stage, (2) ivory medium- to coarse-grained (>1 mm) quartz veins (type C) in the middle stage, and (3) late white calcite-rich quartz veins (type D). Quartz veins are typically accompanied by hydrothermal alteration with zoning (kaolinite-illite-chlorite zone, adularia-chlorite-quartz zone, and adularia-sericite-quartz zone). Gold mineralization is identified in the early stage and free gold exists as micrometer-sized inclusions of native gold within pyrite. Pb–Zn mineralization dominates the middle stage. Hydrothermal fluids within the ore system are of low salinity (<7 wt% NaCl) and gas-poor. The fluid temperatures decreases from 224 − 316 °C for Au mineralization to 190–261 °C for Pb-Zn mineralization. No indication for fluid boiling is found. The H–O isotopes indicate mixing of magmatic and meteoric fluids and a larger portion of meteoric water at a later stage. The δ 34S values of pyrite related to Au mineralization are 1.1–2.0‰ and of sphalerite and galena related to Pb-Zn mineralization range from −1.8 to 2.5‰. The Pb isotopic compositions of sulfides from the early and middle stages are relatively homogeneous and similar with those of subvolcanic rocks within the DVB. Deposit geology, microthermometric result, and isotopic data support a LS epithermal origin for the SSG gold deposit, and therefore suggest a co-existing relationship between low and intermediate sulfidation epithermal gold mineralization within the DVB. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrite of Carlin-type Au deposits in the Youjiang Basin were analyzed by Nano-SIMS. • The δ34S values Au-bearing pyrite of Linwang vary inversely with Au concentrations. • Initial auriferous fluids of Linwang were sourced from magmatic-hydrothermal systems. • Reduced sulfur in ore-forming fluids of Badu was dominated by sedimentary sulfur. • Sedimentary sulfur contamination result in variable δ34S values of Au-bearing pyrite. The Youjiang Basin in Southwest China is the world's second largest Carlin-type gold (Au)-producing region. However, the source of reduced sulfur that accounts for Au transport in ore-forming fluids remains controversial. Finely characterizing the sulfur isotopic compositions (δ34S values) in micron-scale zonation of Au-bearing pyrite is the key to clearly identify sulfur source. Here, we used high-resolution nanoscale secondary ion mass spectrometry (Nano-SIMS) to characterize the temporal variation in δ34S values and its relationship with metal contents across Au-bearing pyrite from the Linwang and Badu deposits in the Youjiang Basin, with the aim of monitoring the source and evolution of reduced sulfur in auriferous fluids. The Au-bearing pyrite rims in the Linwang deposit contain three growth stages that record episodic injections of Au- and As-rich fluids. Within these rims, the δ34S values vary inversely with Au concentrations. The inner rims with the high Au contents have δ34S values of −1.7‰ to +3.3‰ that are comparable to those of magmatic sulfur. The outer rims with decreasing Au contents have δ34S values of +1.3‰ to +15.7‰ that gradually approach those of pre-ore pyrite in the host rock. Such a variation indicates that the reduced sulfur in the initial Au-bearing ore-forming fluids was primarily originated from deep magmatic-hydrothermal systems while the host rock-derived 34S-enriched sulfur increasingly dominated through fluid-rock interactions during mineralization. In contrast, Au-bearing pyrite from the Badu deposit has positive δ34S values ranging from +9.0‰ to +25.8‰, which overlap those of diagenetic pyrite in the Devonian sedimentary rocks. Combining the intimate spatial association between Au mineralization and the Devonian strata, we propose that the initial ore-forming fluids have leached substantial sulfur from the Devonian strata. Significant contaminations of sedimentary sulfur erased the primary sulfur isotopic signals of the initial auriferous fluids. Our interpretations of these two deposits may also apply to other Carlin-type Au deposits in the Youjiang Basin, where δ34S values of Au-bearing pyrite show host rock-dependent variations. This study demonstrates that high-resolution Nano-SIMS sulfur isotope and elemental analysis of Au-bearing pyrite is a potent tool for tracing the source and evolution of reduced sulfur in ore-forming fluids for sedimentary-host Au deposits worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using pyrite Re–Os dating to confirm the timing of gold mineralization. • Investigating the occurrence and deposition mechanism of visible and invisible gold related to pyrite. • Gold deposits within the Dongkeng volcanic basin have an intermediate-sulfidation epithermal origin. The Dongji (>12.5 t Au @ 4.27 g/t) and Maluntou (>5.0 t Au @ 3.70 g/t) gold deposits are the two largest ones in the Dongkeng Volcanic Basin (DVB), SE China, that are hosted by volcanic rocks. Mineralization is represented by three stages (i.e., stage 1, 2, and 3) that are characterized by four types of unzoned hydrothermal pyrite (i.e., pyrite1, 2a, 2b, and 3). Hydrothermal fluids responsible for pyrite1 deposition are moderate temperatures (308–377 °C) and low salinity (4.6–9.1 wt% NaCl equiv.). The deposition of pyrite2a and 2b is related to the stage 2 fluids featured by moderate-low temperatures (253–341 °C) and low salinity (3.2–9.1 wt% NaCl equiv.). Pyire3 is deposited from the stage 3 fluids with low temperatures (220–250 °C) and salinities (1.0–6.5 wt% NaCl equiv.). Hydrothermal fluids potentially have a magmatic origin and experience fluid boiling and mixing of meteoric water. Scanning electron microscopy and laser ablation inductively coupled plasma-mass spectrometry were used to investigate the occurrence of visible gold and the distribution of invisible gold in pyrite from different generations. Visible gold mainly exists as native gold and electrum within crystal interstices, fractures, and hollows of pyrite2b, and precipitates directly from the fluids during fluid boiling at ca. 329 °C with pressure of ca.120 bar. Invisible gold mainly presents in the form of solid solution in all pyrite types. Solid solution gold is also closely related to pyrite2b as the measured Au concentrations in pyrite2b (up to 27 ppm) exceed those in other pyrite types (<0.6 ppm) by one or two orders of magnitude. The elevated content of invisible Au (together with As, Ag, Zn, and Sb) in pyrite2b is potentially associated with lattice dislocations caused by rapid precipitation of Py2b during boiling process. The Re–Os isochron age of pyrite2b (99 ± 10 Ma) and the zircon U–Pb dating of the volcanic and subvolcanic rocks (95.1–104 Ma) indicate that the formation of gold mineralization and the igneous activity in the DVB were coeval during the Turonia–Albian. Geochronology, fluid characteristics, together with low Ni concentrations (<98 ppm) and high mean Co/Ni ratios (≥2.0) of pyrite from different generations, support that the Dongji and Maluntou gold deposits formed in a magmatic-hydrothermal ore system and have an intermediate-sulfidation epithermal origin. [ABSTRACT FROM AUTHOR]

The summary plot of logarithmic Al concentrations versus δ18O fluid of Yata and Qinglong deposits shows three categories represented as initial fluid, Au metallogenic fluid, and Sb metallogenic fluid. The Carlin-type Au deposit and vein-type Sb deposit in the YMP were similar in origin of ore fluids. Different lithologies of wall rocks and the dilution of meteoric water controlled the compositional evolution of fluids. • The initial fluids of the Yata and Qinglong deposits are comparable. • Interaction between fluids and wall rocks determines variations of fluids in Au mineralization. • Meteoric water is a considerable influence in Sb mineralization. Abundant Carlin-type gold deposits and vein-type antimony deposits were discovered in the Youjiang basin of SW China, constituting the Youjiang Metallogenic Province (YMP). Although they had been widely studied by geologists, the genesis of these deposits remains debatable, while both intrusion-linked and non-intrusion linked models have been proposed. In this paper, new data of in situ trace elements (LA-ICP MS) and oxygen isotope (SIMS) analysis of hydrothermal quartz from the Yata Carlin-type gold deposit and the Qinglong vein-type antimony deposit in the province were provided to better understand the origin of ore-forming fluids as well as the genetic mechanism of Au and Sb mineralization. Four quartz generations were identified from the Yata (YTi to YTiv) and the Qinglong (QLi to QLiv) deposits. In the Yata deposit, the fluid inclusions in quartz have varied homogenization temperatures from 140–260 ℃ and salinities of 2.4–7.4 wt％ NaCl eq , while in the Qinglong deposit, the temperatures and salinities ranged from 140–200 ℃ and 0.2–7.2 wt％ NaCl eq., respectively. Both of the temperatures and salinities tend to decrease from early to late generations in the two deposits. δ18O values of initial fluids in the Yata (YTi: 7.70–10.56‰) and the Qinglong (QLi: 4.66–8.75‰) deposits are similar and suggest that they were mainly from magmatic or metamorphic fluids. The covariability of oxygen isotope and Al concentrations indicate that interaction between fluids and wall rocks is a significant factor in determining the compositions of fluids in Au mineralization, and the meteoric water is a key proxy in Sb mineralization, respectively. From these observations, we proposed that the Carlin-type Au deposit and vein-type Sb deposit in YMP were sourced from an analogous ore fluid. Different lithologies of wall rocks and the dilution of meteoric water controlled the compositional evolution of fluids, which might be the main reason for the diversity of Au and Sb mineralization. [ABSTRACT FROM AUTHOR]

• Use LA-ICP-MS and SIMS technique analyzed trace elements and carbon, oxygen isotopes of calcite in Youjiang basin Carlin-type gold deposit. • Calcite cathode luminescence intensity is controlled by Fe, Mn and ∑REE content. Ore-stage calcite of Carlin-type gold deposit has the characteristics of medium-heavy rare earth enrichment. • The ore-forming hydrothermal fluid of Carlin-type is characterized by diversity and mixed. The Carlin-type gold deposits in the Youjiang Basin, SW China can be further classified into three sub-types; strata-bound, fault-controlled, and diabase-associated. The compositions and sources of the ore-forming fluids for each deposit type are evaluated using the texture of calcite by CL (Cathode luminescence), its chemistry by EMPA (Electron probe microanalysis) and LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry), and its C-O isotopic compositions by SIMS (Secondary ion mass spectroscopy). The studied deposits are the stratabound Zimudang deposit, the fault-controlled Lannigou deposit, and the diabase-associated Badu deposit. Calcite in the Zimudang and Lannigou deposits formed at three different stages: pre-ore stage pore-filling and massive calcite (Cal 1), late-ore stage vein calcite (Cal 2) associated with realgar and pyrite, and post-ore stage vein calcite (Cal 3). Calcite in the Badu deposit formed in two stages: ore stage vein and replacement calcite (Cal 2) associated with pyrite and post-ore stage calcites (Cal 3). Calcite with brighter red CL color has higher Mn and lower Fe content than calcite with darker red CL color. Furthermore, the higher the total REE content, the brighter the CL color. The host rocks are characterized by light REE (Rare earth element) enrichments. In contrast, the ore stage calcite shows middle REE enrichments. The ore stage calcite has higher concentrations of Fe, Mn, Mg, Si and Sr, and lower concentrations of Cu, Sb and Zn than both the pre- and post-ore calcite. The ranges of carbon (PDB) and oxygen (SMOW) isotope compositions of calcite are from −11.29 to 6.89‰ and from 16.49 to 22.60‰ for the Zimudang deposit, from −13.31 to 2.80‰ and from 9.12 to 29.71 for the Lanningou deposit, and from −11.94 to 0.49‰ and from 10.51 to 18.97‰ for the Badu deposit. Generally, the ore stage calcite has a wider range of δ13C and δ18O values than the other stage calcite. The isotope data indicate that a deep crustal fluid was involved in the formation of all of these three deposits. Meteoric water containing abundant organic matter was also involved in the formation of the Badu deposit as well as the Zimudang deposit, whereas a basin brine was also involved in the formation of the Lanningou deposit. [ABSTRACT FROM AUTHOR]