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Carlin-type gold deposits are among the most important gold-bearing hydrothermal ore systems and are mainly located in Nevada, USA, and southwestern China. However, the source and evolution of the ore-forming fluids for these deposits remain controversial, especially those found within China. In this study, lithium and oxygen isotopic analyses of quartz-hosted fluid inclusions are used to elucidate the source and evolution of the giant Shuiyindong Carlin-type gold deposit. Fluid inclusions trapped in quartz of three distinct genetic stages have low salinity (0.8–6.3wt% NaCl equiv.) and moderate temperature (154–343 °C), but display variable Li and O isotope signatures. The Li and O isotopes of stage I fluids (δ7Li values from + 5.1 to + 9.1‰; δ18O values from + 6.3 to + 10.0‰) indicate predominantly a magmatic source for the initial ore-forming fluids. The large variations of Li and O isotopes of stage II fluids (δ7Li values from + 9.3 to + 16.0‰; δ18O values from + 0.1 to + 7.7‰) suggest that the fluids are controlled by mixing of magmatic fluids and meteoric water, which in turn triggered the precipitation of gold-bearing sulfides. The isotopic compositions of stage III fluids (δ7Li values from + 15.5 to + 22.8‰; δ18O values from − 5.4 to − 2.8‰) confirm that the final fluids are dominated by meteoric water. Furthermore, this work demonstrates that the combined Li–O isotopic analysis of fluid inclusions is a powerful tracer to decode the source and evolution of ore-forming fluids in hydrothermal mineralizing systems. [ABSTRACT FROM AUTHOR]

The formation of Carlin-type gold deposits is poorly constrained, mainly due to the lack of accurate ages for gold mineralization. The Youjiang basin, SW China, represents the world's second-largest Carlin-type gold province after NV, USA. In this paper, we use hydrothermal apatite U–Th–Pb dating to systemically determine the mineralization ages of five Carlin-type gold deposits, namely, Shuiyindong, Jinfeng, Zimudang, Linwang, and Jinya, in the Youjiang basin. The hydrothermal apatite is characterized by intimate intergrowth with gold-bearing sulfides, presence of primary fluid inclusions, irregular morphology and cathodoluminescence zoning, and MREE-enriched composition patterns, indicating that it is clearly associated and coeval with gold mineralization. The concentrations of lattice-bound U and Th in the apatite are highly variable, making it suitable for in situ secondary ion mass spectrometry (SIMS) U–Th–Pb dating. The dating results of hydrothermal apatite from the five deposits show that they formed at ca. 150–140 Ma, contemporary with the widespread felsic magmatism and associated W–Sn mineralization to the east of the Youjiang basin, probably in response to slab breakup of the Paleo-Pacific oceanic plate beneath the South China continental plate. Our case story suggests that hydrothermal apatite could be a robust chronometer for age dating of sedimentary rock-hosted gold mineralization worldwide. [ABSTRACT FROM AUTHOR]

The Lanping basin, Yunnan province, SW China, is located at the juncture of the Eurasian and Indian Plates in the eastern part of the Tibetan Plateau. The Lanping basin, in the Sanjiang Tethyan metallogenic province, is a significant Cu-Ag-Zn-Pb mineralized belt in China that includes the largest sandstone-hosted Zn-Pb deposit in the world, the Jinding deposit, as well as several Ag-Cu deposits (the Baiyangping and Jinman deposits). These deposits, with total reserves of over 16.0 Mt Pb + Zn, 0.6 Mt Cu, and 7,000 t Ag, are mainly hosted in Meso-Cenozoic clastic rocks and are dominantly controlled by two Cenozoic thrust systems developed in the western and eastern segments of the basin. The Baiyangping, Babaoshan, and Hetaoqing ore deposits are representative of the epithermal base metal deposits in the Lanping basin. The microthermometric data show that the ore-forming fluids for these deposits were low temperature (110-180 °C) and had bimodal distribution of salinity at moderate and mid to high salinities (approximately 2-8 wt.% and 18-26 wt.% NaCl equivalent). The C and O isotope data indicate that the ore-forming fluids were related to hot basin brines. We present new He and Ar isotope data on volatiles released from fluid inclusions contained in sulfides and in barite in these three deposits. 3He/4He ratios of the ore-forming fluids are 0.01 to 0.14 R/Ra with a mean of 0.07 Ra (where R is the 3He/4He ratio and Ra is the ratio for atmospheric helium). This mean value is intermediate to typical 3He/4He ratios for the crust (R/Ra = 0.01 to 0.05) and the ratio for air-saturated water (R/Ra = 1). The mean ratio is also significantly lower than the ratios found for mantle-derived fluids (R/Ra = 6 to 9). The 40Ar/36Ar ratios of the ore-forming fluids range from 298 to 382 with a mean of 323. This value is slightly higher than that for the air-saturated water (295.5). The 3He/4He ratios of fluids from the fluid inclusions imply that the ore-forming fluid for the Baiyangping, Babaoshan, and Hetaoqing deposits was derived from the crust and that any mantle-derived He was negligible. The content of the radiogenic Ar ranges between 0.2 to 20.4%, and the proportion of air-derived 40Ar averages 94.1%. This indicates that atmospheric Ar was important in the formation of these deposits but that some radiogenic 40Ar was derived from crustal rocks. Based on these observations coupled with other geochemical evidence, we suggest that the ore-forming fluids responsible for the formation of the Ag-Cu-Pb-Zn polymetallic ore deposits in the Baiyangping area of the Lanping basin were mainly derived from crustal fluids. The fluids may have mixed with some amount of air-saturated water, but there was no significant involvement of mantle-derived fluids. [ABSTRACT FROM AUTHOR]

Focuses on a study which measured the strontium and rubidium concentrations in fluid inclusions of quartz in gold deposits found in Hunan, China. Details of gold mineralization; Measurement of hydrothermal fluids; Formation of ore minerals; Methodology and results.

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]

The article offers information on the research "He and Ar Isotopes of Fluid Inclusions in the Taoxikeng Tungsten Deposit, South China" by Song Shengqiong and colleagues. It concludes that the ore-forming fluids of the region are fluid contains atmospheric argon and crustal helium, and mantle components and formed by crustal melting.

The Jinman Cu polymetallic deposit is located within Middle Jurassic sandstone and slate units in the Lanping Basin of southwestern China. The Cu mineralization occurs mainly as sulfide-bearing quartz-carbonate veins in faults and fractures, controlled by a Cenozoic thrust-nappe system. A detailed study of fluid inclusions from the Jinman deposit distinguishes three types of fluid inclusions in syn-ore quartz and post-ore calcite: aqueous water (type A), CO2-H2O (type B), and CO2-dominated (type C) fluid inclusions. The homogenization temperatures of CO2-H2O inclusions vary from 208°C to 329°C, with corresponding salinities from 0.6 to 4.6 wt.% NaCl equivalent. The homogenization temperatures of the aqueous fluid inclusions mainly range from 164°C to 249°C, with salinities from 7.2 to 20.2 wt.% NaCl equivalent. These characteristics of fluid inclusions are significantly different from those of basinal mineralization systems, but similar to those of orogenic or magmatic mineralization systems. The H and O isotope compositions suggest that the ore-forming fluid is predominantly derived from magmatic water, with the participation of basinal brine. The δ34S values are widely variable between −9.7 ‰ and 9.7 ‰, with a mode distribution around zero, which may be interpreted by the variation in physico-chemical conditions or by compositional variation of the sources. The mixing of a deeply sourced CO2-rich fluid with basinal brine was the key mechanism responsible for the mineralization of the Jinman deposit. [ABSTRACT FROM AUTHOR]

The Beiya Au deposit in the Sanjiang metallogenic belt, SW China, is a porphyry-skarn deposit that formed in an intracontinental setting. Three stages of hydrothermal veins, namely quartz veins (Stage 1), quartz-pyrite veins (Stage 2), and Au-rich sulfide-quartz veins (Stage 3) were identified on the basis of field relationship and petrography under scanning electron microscopy cathodoluminescence (SEM-CL). Intermediate density aqueous fluid inclusions (ID1, ID2), high density brine inclusions (B1, B2), and low density vapor inclusions (V1, V2) have been identified in both Stage 1 and Stage 2 veins. Only liquid-rich fluid inclusions (L3) were found in Stage 3 veins. Raman spectroscopy revealed that all the inclusions contain abundant CO 2 . H 2 S was identified in ID2 and V2 inclusions. Salinities and homogenization temperatures of the intermediate density aqueous fluid inclusions (ID1, ID2), high density brine inclusions (B1, B2), and low density vapor inclusions (V1, V2) are 7.4 ± 1.1–11.9 ± 2.2, 33.6 ± 0.5–39.2 ± 1, and 1.6 ± 0.7–5.8 ± 0.8 (wt% NaCl equiv.) and 400 ± 35–440 ± 37, 395 ± 20–414 ± 6, and 386 ± 5–416 ± 4 °C, respectively. Salinities and homogenization temperatures of the L3 inclusions range from 4.9 ± 1.6 to 9.8 ± 0.7 (wt% NaCl equiv) and from 301 ± 28 to 398 ± 4 °C, respectively. Initial intermediate density aqueous fluid inclusions contain 2000–10,000 ppm Fe, 2000–4000 ppm Cu, 200–600 ppm Zn, 200–500 ppm Pb, 17–89 ppm Mo, 1–8 ppm Ag, and 0.9–5.9 ppm Au, comparable to that of intermediate density inclusions in subduction-related porphyry deposits. Brine inclusions are rich in metals and have 9000–24600 ppm Fe, 3400–11,000 ppm Cu, 1200–5200 ppm Pb, 500–3000 ppm Zn, hundreds of ppm Mo, and tens of ppm Ag. The corresponding vapor inclusions contain lower metal concentrations: 400–6000 ppm Fe, 1700–4700 ppm Cu, 50–270 ppm Pb, 100–500 ppm Zn, and minor Mo and Ag. Low to intermediate density fluids are abundant and are inferred to have been the main metal transporting medium. A temperature decrease to approximately 350 °C during Stage 3 triggered metal precipitation. [ABSTRACT FROM AUTHOR]

Alkali-rich Cu (Au, Mo) deposits are of increasing economic significance and are an attractive exploration target. They include some of the world's highest grade and largest porphyry related gold resources as well as some of the largest gold accumulations in epithermal settings. The Jinshajiang–Red River alkali-rich intrusive belt, with many porphyry Cu (Au, Mo) deposits, is a representative magmatic belt associated with mineralization. The Jinshajiang–Red River alkali-rich intrusive belt contains several Cu (Au, Mo) mineralized alkali-rich porphyry rocks including the Yulong quartz monzonite porphyry, the Machangqing granite porphyry, the Tongchang quartz syenite porphyry, and the Beiya quartz syenite porphyry. Additionally, there are also some barren alkali-rich porphyry rocks in the belt, such as the Yanshuiqing quartz syenite porphyry. Fluid inclusion petrography and microthermometry on those porphyry rocks are carried out in detail. The results show that the fluid inclusion assemblages in ore-bearing and barren porphyries are distinct: inclusions from barren porphyry are dominated by primary melt inclusions, and contain rare or no fluid inclusions, whereas inclusions from ore-bearing porphyries are dominated by fluid inclusions, and contain rare melt inclusions. Furthermore, halite, sylvite, calcite daughter minerals and an opaque phase in fluid inclusions from ore-bearing rocks are common, but rare in fluid inclusions from barren rocks. The results suggests that the evolution of ore forming fluids especially the halite, sylvite, calcite and opaque daughter minerals bearing fluid inclusions of quartz phenocrysts could be used to judge the degree of metasomatism and mineralization of a porphyry system. [ABSTRACT FROM AUTHOR]

The Baituyingzi Mo (Cu) deposit is a newly identified porphyry deposit located in the southern part of the Xilamulun Mo metallogenic belt, Northeast China. Mo (Cu) mineralization mainly occurs as quartz veinlets and stockwork veinlets in the potassic altered Baituyingzi monzogranite porphyry. A detailed investigation of fluid inclusions and O H isotopes from hydrothermal veins at Baituyingzi allow us to establish the evolving history of the fluid system, as well as understand factors controlling Cu Mo precipitation in CO 2 -rich fluids. Six vein types are recognized at Baituyingzi, which belong to five hydrothermal stages: (1) UST quartz vein, formed during magmatic-hydrothermal transitional stage; (2) A 1 vein (sulfide-barren quartz vein) and A 2 vein (quartz–pyrite–chalcopyrite ± molybdenite vein, Cu mineralization), related to potassic alteration; (3) B vein (quartz–molybdenite ± chalcopyrite ± pyrite vein, Mo mineralization), formed during the potassic-sericitic transitional stage; (4) D vein (quartz–pyrite ± molybdenite ± chalcopyrite vein), associated with sericitic alteration; and (5) late stage L vein (quartz–carbonate vein). Four types of fluid inclusions have been observed in these veins, i.e., liquid-rich inclusions (L-type), vapor-rich inclusions (V-type), polyphase high-salinity inclusions (S-type), and CO 2 -rich inclusions (C-type). UST quartz veins contain abundant S- and co-existing V-type inclusions, accompanied by minor melt inclusions, indicating that the parent fluids were likely in the form of bubbly magma (~ 10 wt% NaCl equiv.) that was derived from a deep magma chamber. A 1 veins are dominated by coexisting S- and V-type inclusions that homogenized at temperatures ranging from 400° to 548.5 °C and pressures between 300 and 750 bar, which may represent the result of parent fluid immiscibility (vapor-brine) at depth. Apart from S- and V-type inclusions, Cu-bearing A 2 veins are especially rich in isolated L-type inclusions (homogenized at 347 to 430 °C) that share the same salinity range as V-type inclusions (homogenized at 375 to 470 °C), suggesting that the vapor gradually contracted to a liquid phase at around 350 bar. Because the system was still in a lithostatic condition (revealed by textures of A 2 veins), Cu precipitation at Baituyingzi was thus largely controlled by temperature reduction (to below 400 °C) near the vapor-liquid surface in relatively oxidized fluids (indicated by the precipitation of abundant hematite). C-type inclusions (homogenize at 275 to 350 °C) seem to be more widely developed, and they commonly co-exist with L-type inclusions (homogenized at 340 to 380 °C) of similar salinity in B veins, implying that they unmixed at temperatures below 350 °C and pressures below 200 bar. Considering that the system had already fluctuated to hydrostatic conditions (revealed by clear open-space filling textures), as well as considering the occurrence of minor feldspar-destructive alteration halos in B veins, Mo precipitation would likely be a result of water-CO 2 immiscibility at temperatures below 350 °C with a sharp pressure reduction to below 200 bar and an increase in fluid acidity. D veins contain plentiful L- and minor C– and S-type inclusions that homogenized at lower temperatures (240 to 350 °C) and pressures (30 to 150 bar). The wide feldspar-destructive alteration halos indicate that the fluids became progressively more acidic and reacted intensely with wall-rocks. L veins only contain low temperature (168 to 280 °C) and low salinity (0.4 to 10.9 wt% NaCl equiv.) L-type inclusions, implying that meteoric water was introduced to the barren magmatic fluids, leading to precipitation of a large amount of remnant material. δ 18 O and δD isotope ratios in quartz (δ 18 O fluid = 3.54‰ to 7.51‰, δD = − 107‰ to − 87‰) also confirm a primary magmatic origin for ore-forming fluids in earlier veins, except for L veins. Therefore, fluid evolution at Baituyingzi was characterized by relatively continuous, system-scale cooling along an ascent path gradually straddling the vapor-brine, vapor-liquid, and water–CO 2 surface in the vapor-dominated H 2 O CO 2 NaCl fluid system, whereas the subtle temporal change in P-T-redox conditions and acid balance of the evolutionary paths of the magmatic fluid may be responsible for Cu and Mo separation at the Baituyingzi CO 2 –rich systems. Additionally, water-CO 2 immiscibility seems to be an additional important mechanism that complicates Mo precipitation in CO 2 –rich systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] Baiyangping Cu–Ag polymetallic ore deposit. [•] The sources of ore-forming fluids and materials in the eastern ore zone. [•] Analyses of fluid inclusion, rare earth element, and isotopic composition (C, O, and S). [ABSTRACT FROM AUTHOR]

Abstract: Carlin-type gold deposits are best known for the scarcity of visible gold in their ores. It has long been recognized that the majority of gold is “invisible”, such that it cannot be resolved by conventional microscopy, and resides in arsenian pyrite. Shuiyindong differs in that sub-μm to μm-sized native gold is present in arsenian pyrite veinlets and disseminations. It is also the largest (55 tonnes) and highest grade (7 to 18 ppm), stratabound, Carlin-type gold deposit in Guizhou, China and has produced 5 tonnes of gold from sulfide refractory ores extracted by underground mining methods. In this study, an electron microprobe analyzer (EMPA) was used to map the spatial distribution of “invisible” gold and sub-μm to μm-size visible gold particles in arsenian pyrite in high-grade ore samples from the Shuiyindong. The samples studied are hosted in Permian bioclastic ferroan limestone of the Longtan Formation and exhibit evidence of decarbonation, silicification and sulfidation. Arsenian pyrite with detectable Au (>400 to 3800 ppm) is disseminated in altered limestone and was deposited in two stages separated by an episode of corrosion in a veinlet. The results show that there are two populations of native gold in arsenian pyrite. One is comprised of sub-μm size gold particles (0.1 to 0.2 μm) that are occasionally present in the gold-bearing arsenian pyrite disseminated in the host rocks. This arsenian pyrite is interpreted to have been formed by sulfidation of ferroan calcite and dolomite. Another is comprised of coarser (1 to 6 μm) native gold grains present in the arsenian pyrite veinlet, either on the first stage where it has been corroded or on the second stage. The lack of fluid inclusion or other evidence of boiling and the low iron content of fluid inclusions in quartz, suggest the veinlet formed by sulfidation of another fluid containing Fe. The Fe-bearing fluid may be a depleted ore fluid that gained Fe by dissolution of ferroan limestone after H2S had been consumed. The association of the largest visible gold grains with an episode of corrosion suggests that fluids episodically became undersaturated with arsenian pyrite while remaining saturated with gold (e.g., pH decrease or an increase in the oxidation state). This may have resulted from incursion of relatively acidic or oxidized fluids that were able to dissolve arsenian pyrite and remain saturated with gold. In this case, sulfidation of iron from the host rock, was the most important depositional mechanism for Au-bearing arsenian pyrite with, or without, grains of native gold. [Copyright &y& Elsevier]