Early Fluids Research Articles

Fluid inclusion LA-ICP-MS constraint on hydrothermal evolution of proximal cassiterite-bearing quartz veins in the giant Gejiu orefield: Implications for controls on metallogenic potential of granite-related skarn system

Sn and Cu are proposed to have their mineralization potential predetermined by their contents in initial fluids of granite-related magmatic-hydrothermal systems. However, it remains ambiguous whether the giant Sn-mineralized skarn system is applicable, and whether the Sn-Cu association in some deposits is predominantly determined by their initial metal contents. The Gejiu orefield is one of the most essential Sn-polymetallic districts worldwide, with proven resources of 3.27 million tons of tin, 3.25 million tons of copper, 4.29 million tons of lead and zinc, and >20 other metals with economic significance. Sn-polymetallic mineralization at Gejiu constitutes a composite skarn ore system that includes proximal skarn and related cassiterite-sulfide, greisen, and tourmaline-vein types. The Laochang Sn-polymetallic deposit hosts several largest skarn and cassiterite-sulfide orebodies in the eastern part of Gejiu. Recent exploitation at Laochang discovered Sn-mineralized quartz veins hosted in the concealed granite, providing a valuable opportunity to characterize the proximal magmatic-hydrothermal process of the mineralizing granitic system. Here, fluid inclusion analysis is carried out on these veins to discuss the fluid evolution, cassiterite precipitation mechanism and whether metal content in early proximal magmatic fluids determines the metal association and endowment in the deposit.Based on the paragenesis of ore and gangue minerals, three hydrothermal stages are distinguished, including quartz-tourmaline stage (Stage I), cassiterite-arsenopyrite-quartz stage (Stage II) and late sulfide stage (Stage III). Fluid evolution controlling vein formation is constrained by microthermometry and LA-ICP-MS analysis of four fluid inclusions generations successively entrapped in quartz and cassiterite. The fluids involved during vein formation show an interplay between single-sourced magmatic fluids and meteoric water. The intermediate-density single phase fluid recorded at stage I quartz is derived from initial fluids directly exsolving from granitic magma. At stage II, fluid immiscibility occurred and the separated brines were entrapped in quartz and early-formed cassiterite. Along with cassiterite precipitation, brines were mixed with low-salinity and cooler meteoric water, leading to entrapment of low-salinity aqueous fluid in outer growth zones of cassiterite at stage II. The constructed fluid evolution history suggests that fluid immiscibility may have facilitated the nucleation of cassiterite crystals at the onset of deposition while mixing of magmatic fluid with meteoric water likely dominate later cassiterite mineralization.Compared with the fluid dataset of barren and mineralized granitic systems worldwide, pre-ore fluids of the studied quartz veins are enriched in Sn, confirming that high Sn content in the initial magmatic fluid can serve as indicator to distinguish mineralized system. In contrast, although Cu mineralization is economically important in the Laochang deposit, predicted Cu contents in pre-ore proximal magmatic fluids are as low as those obtained from Cu-barren system. This implies introduction of Cu into the hydrothermal system from other sources.

Genesis studies of Li–Rb deposits in pegmatites from Bailongshan, western China: Evidence from chronology, fluid inclusions, and H–O isotope analysis

The Bailongshan Pegmatite deposit, located in the West Kunlun Orogenic Belt, Northwest China, is a newly discovered, super-large Li–Rb (Be–Ta–Nb) rare-metal deposit. Since complex magmatic-hydrothermal processes are responsible for the mineralization of such rare-element pegmatites, it is desirable to study the evolution and sources of ore-forming fluids to analyze the genesis of ore deposits. In this study, the 40Ar/39Ar plateau ages of muscovite and biotite were determined to be 171.36 ± 1.87 and 172.39 ± 1.66 Ma, respectively, indicating that the duration of hydrothermal mineralization was approximately 170 Ma. Based on the zonal nature of the mineral assemblage, the Bailongshan area was divided into four zones and stages (I–IV), namely the albite–quartz–lithium tourmaline (AQT, stage I), albite–quartz-bearing mica (AQM, stage II), albite–quartz–spodumene (AQS, stage Ⅲ), and spodumene–quartz (SQ, stage IV) zones. Among these, AQS and SQ were the main ore-bearing areas. In terms of the fluid inclusions found in quartz and spodumene, the different types include a gas-rich phase (V-type), a liquid-rich phase (L-type), a daughter mineral-bearing three-phase (S-type), and a carbon dioxide-bearing phase (C-type). In stage I, the homogeneous temperatures of the V- and S-type fluid inclusions varied from 365 to 415 °C, while their corresponding salinities were 8.5–12.9 and 44.8–47.2 wt% NaCl equiv., respectively. In stage II, the homogeneous temperature and salinity of the L-type inclusions were 315–365 °C and 9.9–13.3 wt% NaCl equiv., respectively, while in stages Ⅲ and IV, the homogeneous temperatures of the L- and S-type fluid inclusions were between 235 and 335 °C, while their salinities were 7.2–12.3 and 32.1–37.0 wt% NaCl equiv., respectively. Furthermore, for the C-type inclusions, the homogeneous temperature and salinity were 235–320 °C and 4.9–10.6 wt% NaCl equiv., respectively. The laser Raman results showed that the fluid in the metallogenic stage was an H2O–NaCl–CO2–CH4 system. Based on the homogeneous temperature and salinity results, the fluid capture pressure from stage III to stage IV was calculated to be 280–150 MPa, and the depth of the capture was >6 km. Moreover, the H–O isotope results suggested that the early ore-forming fluids are mainly magmatic hydrothermal fluids, whereas the later (stage IV) mineralizing fluids may be mixed with a small amount of meteoric water. The subsequent immiscibility of the fluid may be one of the factors responsible for the discharge and precipitation of minerals.

Origin of the Narenwula quartz vein-type W deposit, Inner Mongolia, China: Insights from geochemistry of hosting granites, fluid inclusions, H-O-S isotopes, and wolframite trace elements

Wolframite that coexists with quartz is common hydrothermal mineral in tungsten deposits, and its geochemical features can be used to constrain the tungsten mineralization. Here we show that the Narenwula deposit is a typical quartz vein-type W deposit on the northern margin of the North China Craton, Northeast China, and temporally and spatially associated with Early Cretaceous granitoids, provides an opportunity to decipher the W mineralization process. All the orebodies are composed of a series of northeast- trending wolframite-polymetallic sulfides bearing quartz veins accompanied by intense alterations, mainly hosted in the Early Cretaceous monzogranite and porphyraceous monzogranite. Three paragenetic stages were identified: (I) quartz-wolframite, (II) quartz-wolframite-sulfide, and (III) quartz-fluorite-calcite. LA−ICP−MS trace element analyses revealed that both wolframite (I) and (II) have similar trace elements, REEN patterns, and overall consistent Nb/Ta and Y/Ho ratios, indicate a single fluid source and evolution in the W mineralization of the Narenwula deposit. Fluid inclusions microthermometry of quartz and wolframite, coupled with H-O isotopes suggest that the early ore-forming fluids of the Narenwula deposit are mainly magmatic water with relatively moderate-to-high temperature and salinity, while the late ore-forming fluids are mixed with meteoric water, with medium-to low temperature and low salinity. The δ34S values of pyrite (4.63–6.65 ‰, average = 5.44 ‰) further support a magmatic origin for the sulfides. The metallogenic mechanisms at the Narenwula deposit include fluid boiling and fluid-rock interactions were the two major factors controlling the deposition of wolframite and sulfide, while simple cooling and fluid mixing may have also promoted wolframite precipitation.

Fluid evolution of the Nulasai Cu deposit, Xinjiang, NW China: Evidence from fluid inclusions and O-H-C isotopes

The Nulasai deposit is the earliest Cu mine in Xinjiang, NW China, and has been mined and smelted since the warring state period. Another striking characteristic of the deposit is the high-grade (ave. 1.34 % Cu) with bornite, chalcopyrite and chalcocite as main ore minerals. Through a field and petrographic investigation, three phases of hydrothermal evolution have been recognized at the Nulasai Cu deposit, including the stage I magnetite – quartz ± chalcopyrite ± bornite veins, the stage II calcite – barite ± chalcopyrite ± chalcocite ± pyrite ± bornite veins, and the stage III calcite – barite ± chalcopyrite ± sphalerite ± pyrite ± galena veins. Fluid inclusions of the stage I veins were captured under two-phase condition indicates that existence of both contemporaneous daughter mineral-bearing and liquid-rich fluid inclusions; they have an intermediate-high salinity (11.5 ∼ 38.5 wt% NaCl equiv) and homogenization temperature (266 ∼ 376 °C), with entrapment pressures from 47 to 167 bar (depth of approximately 0.5 to 1.7 km). The coexistence of vapor-rich and liquid-rich fluid inclusions was a defining feature of the stage II fluid inclusions, and they have an intermediate salinity (6.2 ∼ 10.7 wt.%NaCl equiv) and homogenization temperature (211 ∼ 287 °C), with entrapment pressures from 18 to 70 bar (depth of approximately 0.2 to 0.7 km). Fluid inclusions of the stage III veins were captured under two-phase condition, and intermediate-low salinity (3.2 ∼ 9.2 wt.%NaCl equiv) and homogenization temperature (155 ∼ 241 °C), with entrapment pressures of 6 to 32 bar (depth of 0.1 to 0.6 km). According to the stable isotope (O-H-C) data for the three mineralization phases, magmatic water containing organic carbon made up the majority of the early ore-forming fluids, whereas abundant meteoric water has been involved during the late stage of mineralization. Therefore, we suggest that fluid mixture between magmatic water and meteoric water may have led to simultaneous decrease of fluid temperature, salinity and their stable isotope values, and finally facilitates the Cu ore precipitation. This study emphasizes how high-grade Cu deposition in orogenic belts is initiated by fluid dilution.

Fluid inclusion and He-Ar-Pb isotope studies of the Dabie-type Leimengou giant porphyry Mo deposit, Qinling Orogen

The Leimengou deposit is a Dabie-type porphyry Mo system in the Leimengou-Qiyugou orefield of Qinling Orogen. Orebodies host within the porphyry and the metasedimentary Taihua Supergroup. However, the characteristics and sources of ore-forming fluid, metal precipitation mechanism, and the sources of mineralizing substances remain unclear. In this contribution, by a comprehensive study comprising an investigation of deposit geology, fluid inclusion microthermometry, and He-Ar-Pb isotope, we discuss the source and evolution of ore-forming fluids and the molybdenum precipitation mechanism of the Leimengou deposit. The mineralizing process is divided into the Stage I quartz ± K-feldspar vein in potassic altered zone, Stage IIa molybdenite ± quartz vein, and Stage IIb molybdenite + quartz + pyrite ± purple fluorite vein in silicification-phyllic altered zone, Stage III quartz + pyrite + sphalerite + galena ± chalcopyrite ± green fluorite ± pink calcite in prophylitic altered zone and Stage IV quartz ± calcite vein in carbonatization zone based on cross-relationship. The Stage IIa and IIb veins characterize the main molybdenum mineralization stages. By microthermometry, CO2-bearing (C-), Water (WV- and WL-), and daughter minerals-bearing (S-) types of inclusions were recognized. The Stage I quartz contains C-type fluid inclusion assemblages (FIAs) with a salinity of 6.3 ± 1.4 wt% NaCl equiv., and a total homogenization temperature (Th, total) of 473 ± 3 °C. This suggests that the early fluids show characteristics of high temperature, CO2-rich, and moderate salinity, distinguishing them from those of Endako-type and Climax-type deposits. C-type and coexisting W-type FIAs from Stage IIa show similar salinity, ranging from 1.9 to 13.0 wt% NaCl equiv. and 1.9 to 14.1 wt% NaCl equiv., with Th, total of 349–376 °C and 327–392 °C, respectively. Moreover, C-type FIAs homogenize to distinct phases and also show similar homogenization temperatures, indicating fluid immiscibility. The FIAs in Stage IIb show an average salinity of 8.3 ± 7.4 wt% NaCl equiv. and a Th, total of 302 ± 14 °C. WL-type and WV-type FIAs coexist, with similar temperatures varying from 308 to 310 °C during this stage, indicating significant fluid boiling. These observations indicate that the decrease in temperature, fluid immiscibility, and decompression boiling collectively led to the precipitation of molybdenite. Trapping pressures are estimated to be 82–231 MPa for Stage IIa and 43–115 MPa for Stage IIb, corresponding to ore-forming depths of approximately 8.4 km and 4.3 km, respectively. Additionally, the He-Ar isotopes obtained from pyrite indicate a clear mixing trend of crustal fluids with mantle fluids at Stage IIb, with mantle-derived fluid components increasing during Stage III. This coincides with the tectonic shift from regional compression to extension, leading to the formation of many Dabie-type Mo deposits, alongside crustal thinning and the upwelling of asthenospheric mantle materials. Futhermore, Pb isotopes from the ore, ore-hosted gneiss, and ore-causative granitoids demonstrate that the Taihua Supergroup gneiss supplied ore-forming materials, suggesting a crustal origin for the Leimengou Mo deposit.

Magmatic-hydrothermal fluid evolution of the tin-polymetallic metallogenic systems from the Weilasituo ore district, Northeast China

The large Weilasituo Sn-polymetallic deposit is a recent exploration discovery in the southern Great Xing’an Range, northeast China. The ore cluster area shows horizontal mineralization zoning, from the inner granite body outward, consisting of high-T Sn–W–Li mineralization, middle-T Cu–Zn mineralization and peripheral low-T Pb–Zn–Ag mineralization. However, the intrinsic genetic relationship between Sn-W-Li mineralization and peripheral vein-type Pb–Zn–Ag–Cu mineralization, the formation mechanism and the deep geological background are still insufficiently understood. Here, we use fluid inclusions, trace elements concentrations in quartz and sphalerite, and H–O isotope studies to determine the genetic mechanism and establish a metallogenic model. Fluid inclusion microthermometry and Laser Raman spectroscopic analysis results demonstrates that the aqueous ore-forming fluids evolved from low-medium salinity, medium–high temperature to low salinity, low-medium temperature fluids. Laser Raman spectroscopic analysis shows that CH4 is ubiquitous in fluid inclusions of all ore stages. Early ore fluids have δ18OH2O (v–SMOW) values from + 5.5 to + 6.2‰ and δD values of approximately − 67‰, concordant with a magmatic origin. However, the late ore fluids shifted toward lower δ18OH2O (v–SMOW) (as low as 0.3‰) and δD values (~ − 136‰), suggesting mixing between external fluids derived from the wall rocks and a contribution from meteoric water. Ti-in-quartz thermometry indicates a magmatic crystallization temperature of around 700 °C at a pressure of 1.5 kbar for the magmatic ore stage. Cathodoluminescence (CL) imaging and trace element analysis of quartz from a hydrothermal vug highlight at least three growth episodes that relate to different fluid pulses; each episode begins with CL-bright, Al-Li-rich quartz, and ends with CL-dark quartz with low Al and Li contents. Quartz from Episode 1 formed from early Sn-(Zn)-rich fluids which were likely derived from the quartz porphyry. Quartz from episodes 2 and 3 formed from Zn-(Sn)-Cu-rich fluid. The early magmatic fluid is characterized by low fS2. The SO2 produced by magma degassing reacted with heated water to form SO42−, causing the shift from low fS2 to high fS2. The SO42− generated was converted to S2– by mixing with CH4-rich, Fe and Zn-bearing external fluid which led to late-stage alteration and dissolution of micas in vein walls, thus promoting crystallization of pyrrhotite, Fe-rich sphalerite and chalcopyrite and inhibiting the precipitation of anhydrite. This study shows that ore formation encompassed multiple episodes involving steadily evolved fluids, and that the addition of external fluids plays an important role in the formation of the later Cu–Zn and Ag–Pb–Zn mineralization in the Weilasituo ore district.

Characteristics of Ore-Forming Fluids and Genesis of the First Mining Area and Eastern Ore Section of the Pulang Porphyry Copper Deposit, Southeastern China: A Comparative Study

The Pulang copper deposit, formed in the Late Triassic, is the largest porphyry Cu-Mo-Au deposit in the eastern Tethys, and its genetic type and mineralization potential have received widespread attention. Identifying the characteristics of ore-forming fluids and the sources of ore-forming materials in the deep and peripheral ore bodies of Pulang is particularly important for constructing a complete porphyry copper mineralization system. Based on detailed core logging and geological observations, this article provides extensive petrographic, fluid inclusion micro-thermometry, laser Raman spectroscopy, and H-O-S isotope data on the veins of the main mineralization stage (B veins) in the first mining area and eastern ore section of the Pulang porphyry copper deposit. The genetic correlation between the eastern ore section and the first mining area is clarified, and their mineralization potential is inferred. The results indicate that the deep vein bodies in the first mining area exhibit multi-stage characteristics, and the fluid in B veins exhibits both high-temperature and salinity characteristics. The magma-derived early ore-forming fluids underwent processes such as boiling and experienced immiscibility during meteoric water mixing, which could be the primary mechanism of the precipitation of Cu, Mo, Au, and other metals. The outer eastern ore section is located in a medium-to-low-temperature hydrothermal mineralization zone far from the mineralization center. This outer eastern ore section is a distant part of the magmatic–hydrothermal system of the first mining area.

Remobilization of HFSE, Y, and REE during Diagenetic Alteration of Heavy Minerals in Sandstones from the Chvalčov Site, Flysch Belt of the Outer Western Carpathians, Czech Republic

An in situ electron microprobe study of detrital minerals yielded important insights into the diagenetic history of the Cretaceous-to-Paleogene flysch sandstones from the Chvalčov site, Rača Unit, Flysch Belt of the Outer Western Carpathians. Detrital titanite and a Fe-Ti mineral (probably ilmenite) were almost completely altered to TiO2 minerals, which also newly crystallized in intergranular spaces of sandstone. Brookite, anatase, and, exceptionally, rutile were identified by Raman spectroscopy. Authigenic TiO2 phases show complex composition with occasionally elevated contents of Fe, Nb, Zr, V, Sc, Cr, Al, Y, and/or P, which were likely sourced from altered neighboring heavy minerals. In addition, rare authigenic LREE- and Y-enriched apatite rims were observed on detrital apatite. The remobilization of REE, Y, and HFSE was likely mediated by acidic early diagenetic fluids enriched in fluoride and sulfate anions. The superimposed formation of calcite cement was associated with the dissolution of detrital garnet, feldspars, and quartz. The compositions of detrital apatite and garnet (Alm60-82Prp4-30Sps0-24Grs0-19) are comparable with those from adjacent parts of the Flysch Belt. Detrital rutile is enriched in Nb, V, Cr, and Zr. Our study illustrates the intensity of diagenetic alteration of detrital minerals in flysch sandstones as well as the usefulness of in-situ electron-microprobe investigations for the recognition of processes influencing heavy minerals in diagenetically altered sediments.

In-situ molybdenite and rutile geochemistry of the Nannihu porphyry Mo-W deposit, East Qinling, China: A perspective on ore-forming processes

As the important strategic mineral resource, molybdenum is widely utilised by various industries of national economy. Most of the Chinese Mo deposits are classified as porphyry deposits, such as the Nannihu porphyry Mo-W deposit that is one of the biggest Mo deposits in China. Previous studies mostly focused on the geochemistry, geochronology, and isotopic geochemistry of the Nannihu deposit, but its element immigration and occurrence as well as the ore-forming source remain unclear, which limits the development of ore prospecting. Here we document in-situ major and trace element geochemistry of different stages of molybdenite and rutile from the Nannihu deposit, with major aims to determine ore-forming element immigration and occurrence and to reveal ore-forming processes. Based on mineral assemblages and micro-texture, three types of rutile were identified in the Nannihu deposit. The type-1 rutile has stable Y/Ho ratios 16.74–20.82 and similar upper crust rare earth elements (REEs) patterns, which suggest magmatic and crustal origin. The type-2 and 3 rutiles show wide variation Y/Ho ratios (10.69–49.55 for type-2 and 17.85–43.64 for type-3) and belong to hydrothermal rutiles. In addition, two types of molybdenite are also presented, with the Mo1-type for the major ore-forming stage and the Mo2-type for the late ore-forming stage. The fluctuation of elements in the time resolved LA-ICP-MS spectra curve diagram of the Mo1- and Mo2-type molybdenites indicate that the Te, Bi, Pb, Fe and Mn elements are hosted as mineral inclusions in molybdenite lattices. However, the Re and Se elements in these molybdenites display flat signatures and have negative correlations with Mo and S elements, which imply that the Mo and S elements are substituted and occur as isomorphous constituents in molybdenite lattices. The low Re contents (1.60–12.90 ppm) of molybdenites also suggest crustal-mantle mixing metallic sources for the Nannihu deposit. The increasing Fe (4245 to 23943 ppm) and W (1631 to 5922 ppm) contents in hydrothermal type-2 and type-3 rutiles as well as the increasing W contents (113 to 243 ppm) in Mo1- and Mo2-type molybdenites both indicate that the Nannihu ore-forming fluids were under the temperature and oxygen fugacity (fO2) of reduction conditions. The Mo1-type molybdenite is enriched in light REEs and depleted in high field strength elements (HFSEs), and coupled with the late ore-forming stage of F-rich fluorite, which indicate the ore-forming fluid evolution from Cl- to F-rich. Integrating with previous studies, the mineralising fluids of the Nannihu deposit are suggested to be featured by high Cl−, CO2 and metallic contents. The Mo and W ions in mineralising fluids immigrate as Cl-complexes at the early stage of mineralisation, the Mo4+ is then replaced by W4+ in molybdenite lattices at the later stage, and the high temperature and fO2 of the early ore-forming fluids promote the migration of Mo and W elements during ore-forming processes. Eventually, the fluids boiling, and the reduction conditions in temperature and fO2 jointly result in the final precipitation of Mo and W to generate the giant Nannihu deposit under extensional tectonics.

Origin of the Early Cretaceous Be mineralization in the Tongbai-Dabie orogen, central China

The Niangniangding Be deposit is a Be-only deposit in the Tongbai-Dabie orogen. The Be mineralization is hosted in albitized granite in the contact zone between biotite monzogranite and metasedimentary rocks. Genthelvite, a Zn-rich helvine-group mineral, is the major carrier of Be. The Niangniangding biotite monzogranite and albitized granite were emplaced at 769–766 Ma and were derived from reworking of Paleoproterozoic crust in a Neoproterozoic continental-rift setting. Hydrothermal monazite coexisting with genthelvite yields an in situ U-Pb age of 126.7 ± 1.6 Ma, demonstrating that the Be mineralization is genetically unrelated with the Niangniangding granite that was albitized by Early Cretaceous ore-forming fluids. The albitization caused an increase of Al, Na, Mn, Fe, Zn, Be and Sr contents and a decrease of Si, K, Rb and Ba contents, reflecting in the formation of spessartite, albite, genthelvite and calcite and the consumption of quartz, K-feldspar and biotite. Petrographic and geochemical evidences hint that ore-forming fluids and metals (e.g., Be, Zn, Mn) may be sourced from non-exposed Cretaceous intrusions and metasedimentary wall rocks (the Huangmailing Formation). The Early Cretaceous intrusions are related to crustal extension due to the rollback of Paleo-Pacific plate. The close spatial relation between genthelvite, calcite, and albitization indicate that the fluid composition (the availability of Na+ and CO2– 3) may have crucially controlled the precipitation of Be. Our study indicates that the Tongbai-Dabie orogen has potential for Early Cretaceous extension-related Be deposits.

Fluid evolution and mineralizing process of the Bawang Fe-Zn-Sn deposit, Danchi Fold-and-Thrust belt, South China

The Bawang deposit, a newly discovered Fe-Zn-Sn deposit occurred in the paleokarst in the Youjiang Basin, South China, offers an excellent opportunity to understand the ore-forming process and genesis of this unique tin mineralization, thus enriching the tin mineralization theories. Mineralogy, X-ray photoelectron spectroscopy (XPS), and laser ablation-inductively coupled plasma-mass (LA-ICP-MS) analysis were performed on sphalerite to investigate the fluid evolution and mineralizing process of the Bawang deposit. The formation of the deposit involved hydrothermal-cassiterite-sulfides and oxidation periods. The hydrothermal-cassiterite-sulfides period is dominated by the mineralization of Zn- (stage 1), Sn- (stage 2), and Sb- (stage 3) in order. Three types of sphalerite were identified in these hydrothermal stages. Mineralogical studies and spectrum data show that the massive sphalerite in stage 1 (Sp1) is euhedral coarse-grained and characterized by high Fe contents (9.67–15.69 wt%), with obvious pyrrhotite blebs, pyrite laths, stannite and/or chalcopyrite solid solutions. The sphalerite with 5.56–11.31 wt% Fe contents in stage 2 (Sp2) occurs as fine-grained, euhedral to subhedral crystals (15–50 μm) and coexists with cassiterite, arsenopyrite, and quartz. The sphalerite in stage 3 (Sp3) is characterized by low Fe content (0.59–2.99 wt%) and is generally micro-fine-grained (10–30 μm) associated with stibnite, sulfosalts, and carbonates. LA-ICP-MS analyses of sphalerite suggest that Sp1 and Sp2 have similar characteristics and are enriched in Fe, Cu, Sn, Ga, and Cd, whereas Sp3 is enriched in Sb, Pb, Ag, Bi, and Tl. The principal component analysis (PCA), boxplots, and bivariate plots of trace elements from sphalerite, combined with previous Raman spectroscopy data for fluid inclusions and H-O-Cd isotopic compositions, indicate two types of ore-forming fluids were involved in the mineralization of the Bawang deposit. The early Fe-Zn-Sn-Cu-In-rich fluids originated from granitic magma and underwent Zn- and Sn-dominated mineralization in order in a slowly cooling closed system. The later hydrothermal fluids with the addition of oil field brine were enriched in Sb, Pb, Ag, and Bi elements in the Sb-sulfosalts-carbonates stage in an open system with a drop in temperature. The mineralization process of the Bawang deposit can be concluded as follows: The early ore-forming fluids derived from an inferred concealed intrusion infilled into the paleokarst (below 350 m of the altitude) and caused the massive euhedral ferroan sphalerite (stage 1) to precipitate. The deposition of sphalerite decreased sulfur fugacity (fS2) in a slowly cooling closed system, and increased relative oxygen fugacity (fO2) which promoted cassiterite to precipitate in stage 2. The foreign hydrothermal fluids lowered the temperatures of residual ore-forming fluids due to the addition of oil field brine. Then the Pb-Sb sulfides and Pb-Sb-Ag-Bi-bearing sulfosalts (stage 3) crystallized at shallow depths (350 to 500 m of the altitude).

Study on the complex magmatic and hydrothermal metallogenic processes in the giant Huayangchuan uranium (U)-polymetallic ore district: Constraints from geochemical and geochronological evidences

The supergiant Huayangchuan uranium (U)-polymetallic deposit is situated in the west part of Lesser Qinling Orogen, Central China, which is renowned for its unique metallogenic type and complex mineralization processes. This newly-discovered deposit contains economic endowments of U, Nb, Pb, Se, Sr, Ba and REEs. The genesis of this deposit remains hugely controversial and the related magmatic and metallogenic framework have not been well established. In our study, we present newly obtained zircon U-Pb age data, whole-rock trace elements, detailed SEM observation, carbon and oxygen isotope determination and titanite U-Pb age result to provide geochemical and geochronological constraints on the magmatic and hydrothermal metallogenic processes in Huayangchuan ore district and give insight into the REE, Nb and U mineralization and remobilization mechanism. Carbonatite in Huayangchuan deposit is rich in Ba, Sr, Nb, U and REE and the δ18OSMOW and δ13CPDB (‰) values of carbonatite vary between + 7.30 ‰ to + 9.80 ‰ and − 6.00 ‰ to − 7.20 ‰, respectively, which is the unique characteristic of igneous carbonatite. The total REE contents of carbonatite range from 1319.5 to 2535.8 ppm, significantly higher than that of the granite pegmatite dykes and Taihua Group granitic gneiss. Two zircon grains from the Huayangchuan carbonatite yield the 206 Pb / 238 U age of 223 ± 5.6 Ma and 217 ± 8.6 Ma. Uranium and niobium are mainly hosted in the primary mineral of betafite, minorly in uraninite and fergusonite. REE are remained in various REE carbonates, phosphates and silicates, e.g. allanite, parite, monazite, apatite, yttrialite and xenotime. Betafite contains numerous mineral inclusions of calcite, allanite and apatite, which displays as vermicular relicts with metasomatic corrosion texture. The intimate relationship between betafite, calcite, apatite, allanite and REE carbonates implies that U and Nb mineralization occurred during carbonatite-related magmatic stage. Late Triassic carbonatite magmatism (∼220 Ma) was responsible for the world-class U-Nb-Mo-REE mineralization in the Qinling Orogen. Whereas, LA-ICP-MS U-Pb data of titanite collected from Huayangchuan carbonatite reveal two sets of ages in the Huayangchuan deposit: during the Late Triassic and the Early Cretaceous. LA-ICP-MS data of the Triassic titanite and Cretaceous titanite in Huayangchuan deposit yield the lower intercept age of 223.1 ± 9.4 Ma and 141.9 ± 4.7 Ma respectively in the Tera-Wasserburg (238U/206Pb - 207Pb/206Pb) diagram. Cretaceous hydrothermal titanites show enrichment in Y, HREEs and depletion in TiO2 and LREEs relative to the Triassic magmatic titanites. Primary betafite and titanite were subjected to later hydrothermal alteration. The close genetic relation between altered titanite and Ti-Fe-Nb-Pb-U mineral inclusions demonstrates that Early Cretaceous hydrothermal fluids contributed to the Nb, U and Ti remobilization. Early Cretaceous regional granitic magmatic activity brought hydrothermal fluids to alter the early carbonatite magmatic pyrochlore and titanite. U, Nb, Ti, Y, Pb and HREEs were transferred and subsequently re-precipitated into uraninite, and hydrothermal titanite.

The genetic association between vein and skarn type tungsten mineralization in the Yaogangxian tungsten deposit, South China: Constraints from LA-ICP-MS analysis of individual fluid inclusion

The large-scale Yaogangxian W deposit, located in central of the Nanling metallogenic belt, South China, comprises independent quartz vein-type and skarn-type W mineralization. Wolframite-bearing quartz veins occur invariably in metasandstone and slate to the northwest of the Yaogangxian granitic intrusion, whereas scheelite-skarn are mainly hosted by the limestone to the east. The vertical extension of single wolframite-bearing quartz vein can reach up to 1000 m and we focused on the vein samples collected from the deepest level (26 level) which likely recorded early magmatic fluids. For skarn mineralization, two scheelite precipitation stages were recognized, namely scheelite-1 in retrograde stage and scheelite-2 from sulfide-stage. To reveal the fluid sources and characteristics of two mineralizing systems, detailed petrography and microthermometry analyses were carried out on fluid inclusion assemblages (FIA) in scheelite, wolframite and their coexisting quartz. Fluid compositions were obtained from individual fluid inclusion (FI) in ore and gangue minerals via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. These data aid elucidation on the source and nature of fluids in the two distinct W mineralization styles. The chemical compositions of FIs hosted in wolframite and scheelite points to a common magmatic source. The fluid in the scheelite ore section exhibits lower As and B than the wolframite ore section, indicating that boiling may have occurred at early skarn stage. Fluid evolution in the two mineralizing systems suggest that formation of diverse W mineralization styles is mainly controlled by different host lithology and fluid processes. In the wolframite ore section, ore-forming fluid recorded in the deepest level of vein show elevated As, B, K and Rb contents than previously reported ore-forming fluid obtained from the tip of the vein. This likely indicate absence of intensive fluid immiscibility in the deep during wolframite formation, which may rather be accompanied by fluid-rock interaction. In the scheelite ore section, constant injection of meteoric water is revealed. FI hosted in scheelite-1 and 2 exhibit similar compositions, and the lower K content in scheelite-2 fluid is thought to be caused by sericitization in the retrograde stage skarn. The Mo content of scheelite decreased from the retrograde stage to sulfide-stage, indicating a decrease in oxygen fugacity. Based on these conclusion and previous geological and geochronological studies, we propose a metallogenic model of the coupled wolframite-quartz vein and scheelite-skarn mineralization.

Carbonatite-related delicate REE mineralization processes revealed by fluorocarbonates and monazite: Insights from the giant Bayan Obo REE-Nb-Fe deposit, China

Fluorocarbonates and monazite are common economic REE minerals in carbonatite-related REE deposits, such as the largest known REE deposit at Bayan Obo, China. The geochemical evolution of REE minerals is a sensitive and effective indicator of delicate REE mineralization processes. In this study, the fluorocarbonates and monazites were classified into three generations, corresponding to three REE mineralizing stages. The first generation (Gen-1) of bastnäsite and monazite are generally characterized by elevated La/Ce, La/Nd and La/Lu ratios, with right-declining chondrite normalized REE distribution patterns. They have low Th and radiogenic Sr content, with forming age of about 1.3 Ga and εNd(t) around 0, indicating a primary origin and orthomagmatic crystallization from carbonatite melts. The second generation (Gen-2) of REE minerals, formed at 1.25–1.2 Ga, normally constitute banded aggregates with associated hydrothermal gangue minerals (fluorite, aegirine, sodium amphibole etc.). The Gen-2 REE minerals are featured by moderate-low La/Ce, La/Nd, La/Lu ratios but slightly elevated 87Sr/86Sr0 ratios, indicating a Mesoproterozoic hydrothermal origin related to carbonatitic fluids. Gen-2 bastnäsite and monazite precipitated earlier in low-fluid/rock-ratio environment with right-declining LREE distribution patterns, while the subsequent Gen-2 parisite and huanghoite display convex LREE patterns and higher OH/F ratios, indicative of relative La-depletion and increased ambient fluid/rock ratios during progressive hydrothermal REE mineralization. The third generation (Gen-3) of REE minerals are generally megacrysts in the vein-type ores formed in the early Paleozoic REE mineralization stage (470–420 Ma). The Gen-3 REE minerals are typified by significantly variable REE, Sr and Nd isotopic components, indicating extensive hydrothermal metasomatism and intense contamination of crustal material. Induced by activities of early Paleozoic subduction-related fluids, Gen-3 REE minerals were formed through local REE re-enrichment within the ore-hosting dolomite, rather than by introduction of REE from external sources. In this case study, a comprehensive model of the delicate REE mineralization processes of the giant Bayan Obo REE-Nb-Fe deposit has been established. This study highlights the great potential of fluorocarbonates and monazites widely distributed in carbonatite-related REE deposits as universal geochemical indicators of late-stage evolution of carbonatite and delicate magmatic-hydrothermal REE mineralization processes.

CeAF Ameliorates Diabetic Wound Healing by Alleviating Inflammation and Oxidative Stress via TLR4/NF-κB and Nrf2 Pathways.

With the rise in diabetes incidence, diabetic foot ulcers have become the most common clinically chronic refractory wounds. Persistent chronic inflammation is a typical feature of diabetic cutaneous wounds, and diabetic wound healing can be improved by alleviating inflammation and oxidative stress. Chick early amniotic fluids (ceAF) consist of native conglutinant substances with balanced amounts of growth factors, cytokines, and chemokines. However, whether ceAF modulates inflammation and oxidative stress and thus promotes diabetic wound healing remains unknown. RAW264.7 cells were categorized into four groups: negative control, LPS, LPS + ceAF, and ceAF. 10% of ceAF was selected to treat different groups of mice with a full-thickness skin defect wound. Then, RT-qPCR, western blot, immunofluorescence, and other assays were carried out to explore the effect of ceAF on wound healing and its molecular mechanism. Topical administration of ceAF improved M2 macrophage polarization and inflammatory response in the wound tissues, thereby ameliorating delayed wound healing. Histological improvement could be observed in the grade of inflammation, collagen deposition, and neovascularization in wound edge tissues. ceAF also increased M2 macrophage-specific markers expression and exogenous ceAF suppressed LPS-induced cellular inflammatory response in vitro high glucose environment. Additionally, ceAF could activate TLR4/NF-κB and Nrf2 signal transductions to promote M2 macrophage polarization in vitro. In summary, ceAF downregulates inflammatory response, regulates M2 macrophage transition via TLR4/NF-κB and Nrf2 signaling pathways, and thus improves diabetic wound healing.

Relative importance of magmatic and hydrothermal processes for economic Nb-Ta-W-Sn mineralization in a peraluminous granite system: The Zhaojinggou rare-metal deposit, northern China

Highly evolved granitic melts typically experience late-stage melt-melt and fluid-melt immiscibility as well as fluid-melt and fluid-rock interaction. These processes are particularly important in the formation of deposits of the rare metals Nb, Ta, W, and Sn. We document the relation between immiscibility and alteration processes and the partitioning behavior of rare metals for the Zhaojinggou rare-metal deposit of northern China. This deposit shows a systematic change from a magmatic to a hydrothermal system, including the reaction of the exsolved fluid with earlier crystallized granite and the formation of late-stage quartz veins. The magmatic stage (Stage I) includes biotite alkali-feldspar granite (BAG) with moderate Nb-Ta mineralization. Extreme fractional crystallization of BAG eventually resulted in melt-melt immiscibility and the separation of a hydrosaline melt. Fractional crystallization of this hydrosaline albite granite (AG) melt finally exsolved a magmatic fluid. Therefore, the magmatic-hydrothermal transition (Stage II) includes a melt-dominated Stage IIa with strong Nb-Ta-Sn mineralization in AG and a fluid-dominated Stage IIb with minor Nb-Ta-Sn mineralization in muscovite and biotite greisen. Late hydrothermal processes (Stage III) formed quartz veins with important W mineralization. There are several texturally and chemically distinct generations of cassiterite and columbite-group minerals (CGM) in BAG and AG reflecting crystallization from an evolving magma. The porous and patchy-zoned reaction rims of tantalite-(Mn) and wodginite on CGM in AG are the result of fluid-melt interaction. Texture and compositions show that wolframite in AG is hydrothermal and formed through interaction of early exsolved magmatic fluids with the host granite. CGM and cassiterite in the biotite greisen and Ta-rutile in the muscovite greisen, as well as wolframite and scheelite in quartz veins that formed when fluid-rock interaction reduced the availability of H+ or F− or the temperature of the fluid decreased. The distribution and importance of mineralization demonstrate that Nb, Ta, W, and Sn strongly partitioned into the hydrosaline melt during melt-melt immiscibility and that W partitioned into the magmatic fluid during fluid-melt immiscibility. Exsolved magmatic fluids interacted with earlier crystallized rocks mobilizing rare (Nb, Ta, and Sn) and base (Fe and Ti) metals from Li-Fe mica, providing the ore elements for subordinate Nb-Ta-Sn mineralization in AG and in biotite and muscovite greisen. Thus, magmatic processes (with later metal redistribution by magmatic fluids) dominantly control economic Nb-Ta-Sn mineralization, whereas hydrothermal processes mainly control the formation of economic W mineralization.

Isotopic signals in fracture-filling calcite showing anaerobic oxidation of methane in a granitic basement

Understanding the long-term redox conditions and the related carbon cycle in groundwater is essential for long-term safety assessment because they affect the performance of barrier systems and radionuclide transport in geological disposal. However, it is difficult to identify those long-term changes directly. To help understand this, we conducted a paleohydrogeological study on calcite mineralization associated with fracture-controlled groundwater flow-paths in the Toki Granite in central Japan, focusing on its carbon and oxygen stable isotope characteristics. Previous studies revealed four generations of fracture-filling calcite in the Toki Granite. Therefore, we conducted isotopic analysis on both bulk samples of calcite and spatially-resolved microsamples of discrete generations of calcite within zoned crystals. The δ18OVPDB of calcite ranging between −32.7‰ to −0.59‰ revealed that the groundwater that precipitated the calcite was derived from various origins over the geological history of the area, including early hydrothermal fluids associated with the late-stage cooling of the granite (less than −17.2‰); freshwater invasion from the surface following regional uplift (−18.5‰∼ −8.3‰), and; seawater that penetrated during periods of marine transgression (−8.7‰ ∼ −0.3‰). The range in δ13CVPDB values (−56.5‰ ∼ +6.0‰) was wider than the isotopic range of dissolved inorganic carbon (DIC) that originated from hydrothermal, meteoric, and seawater sources (−25‰ ∼ +2‰). Calcite with low δ13CVPDB values less than −25‰ is believed to have precipitated from groundwater with DIC that was provided by anaerobic oxidation of methane (AOM), whereas calcite with δ13CVPDB higher than +2‰ is believed to have precipitated from groundwater containing 13C-enriched DIC as a carbon source derived during methanogenesis. These processes influencing the formation of calcite mineralization in the Toki Granite are comparable to those at other crystalline rock sites in European countries. The AOM calcite and calcite associated with methanogenesis in the Toki Granite precipitated during the transition of the groundwater origin from meteoric to seawater. Understanding these redox processes and the related carbon cycle in granitic groundwater can provide important insights into processes relevant to assessing the long-term evolution of geoenvironmental systems.

Geochronology (U-Pb and Re-Os) and H[sbnd]O[sbnd]S isotopes reveal ore fluid origin and crucial role of meteoric water for Laozuoshan quartz-vein-hosted gold metallogeny in Jiamusi, NE China

The Laozuoshan auriferous sulfide-quartz veins, which are hosted in the granodiorite, monzogranite, and quartz diorite, are the only Early Cretaceous gold deposit discovered in the central Jiamusi Massif, but its origin and ore-forming processes remain unclear. Here, we integrate mineralogy, HOS isotopes, and U-Pb and Re-Os geochronology to unravel the formation of the Laozuoshan quartz-vein gold mineralization. Zircon and molybdenite from the monzogranite wallrock and gold ores yield weighted mean U-Pb and isochron Re-Os dates of 259.9 ± 2.1 Ma and 103.3 ± 2.3 Ma, respectively. Our radiometric dating suggests that the Laozuoshan quartz-vein gold mineralization was coeval with the quartz diorite (105–103 Ma) but after the monzogranite emplacement. Quartz grains from the auriferous veins of different stages yielded scattered δ18O values (5.4 to 13.0 ‰), with the δD values (fluid inclusions) ranging from –99.9 to –74.9 ‰. The δ18O values of quartz (10.9–13.3 ‰) and feldspar (9.4–11.0 ‰) from the unaltered wallrocks are similar to those (δ18Oquartz = 11.2–13.2 ‰ and δ18Ofeldspar = 10.0–10.4 ‰) from the potassic alteration halos. Meanwhile, the sericite-altered rocks have δ18O values of 12.4–12.9 ‰ (quartz) and 3.4–5.2 ‰ (sericite). Sulfides from the gold ores yielded decreasing δ34S values from 5.3 to 6.9 ‰ (early stage), through 1.0–3.5 ‰ (intermediate stage), to –4.9 to –4.4 % (late stage). The isotope data reflect a largely magmatic source for the early ore fluids, whilst the sulfur was possibly derived from the Mashan Group migmatite. The results, in combination with geologic evidence, indicate that the Laozuoshan quartz-vein gold mineralization was spatially, temporally, and genetically related to the Early Cretaceous quartz diorite, and thus can be classified as intrusion-related, magmatic-hydrothermal-vein type. In the ore-forming processes, the ascending Early Cretaceous magma may have acquired most of their sulfur and gold through assimilation of the Mashan Group migmatite. The early ore fluids derived from the quartz diorite magma may have initially focused into narrow cracks/fractures in the quartz diorite margin and then flow along the fracture system. Subsequently, meteoric water incursion led to temperature drop, boiling, oxygen fugacity increase, and chemical exchange of the resultant fluids, which facilitated gold scavenging by bismuth-rich melts and rapid precipitation as arsenopyrite-hosted electrum and gold-bismuth mineral eutectic assemblage. This study highlights the crucial role of meteoric water in formation of the magmatic-hydrothermal-vein type gold deposit.

Age and compositions of garnet in a magnesian skarn Au-Cu deposit, Tibet, implications for ore-fluid evolution

Compared to calcareous skarn Au-Cu deposits, magnesian skarn (Mg-skarn) Au-Cu deposits are scarce; hence the early evolution of the ore-fluids to late mineralization for the kinds of deposits has been inadequately investigated. Located at the southern margin of the Bangong-Nujiang metallogenic belt, the Galale Au-Cu deposit contains 32.59 tonnes of gold (average grade 2.04 g/t) and 105,600 tonnes of copper (average grade 0.66 %). The orebodies are hosted in an Mg-skarn with associated minerals, including olivine, pyroxene, garnet, and serpentine, which developed in the contact zone between the granodiorite and dolomite of the Jiega Formation. However, the genetic relationship between the Mg-skarn, granodioritic magma, and Au-Cu mineralization remains unclear. The contribution of early stage ore-forming fluids to late Au-Cu mineralization is still vague. In this study, we present the major and trace element compositions, and U–Pb isotope data for garnets obtained from the Galale deposit. We used the data to define the timing, nature, and evolution of early ore-forming fluid and described the genesis of the deposit. The color, at macro- and micro-scales, and chemical composition of the garnets can be used to divide them into two categories, namely early Al-rich Grt-I type garnets, and late stage Fe-rich Grt-II type garnets. In practice, Grt-I (And29.5∼56.1Gro41.3∼68.0Pra1.6∼2.8) and Grt-II (And96.7∼99.9Gro0∼2.7Pra0.1∼0.7) are grossular-andradite solid solution system garnets. Based on the chondrite-normalized REE patterns, Grt-I can be further divided into two sub-classes: Grt-I-1 domain in the core, enriched in HREEs and U, and Grt-I-2 material in the rim, relatively depleted in HREEs. Grt-II is enriched in LREEs and depleted in HREEs. Eu anomalies are slightly negative for the Grt-I-1 domain, weakly positive for the Grt-I-2 domain, and strongly negative for the Grt-II type garnets. The variations in texture and composition in garnets indicated that the formation of Grt-I garnets occurred during diffusive metasomatism in a relatively closed system, in a moderately oxidized ore-forming fluid setting. The formation of Grt-II occurred in a strongly oxidized setting during advective metasomatism in an open system. The enrichment of REE and U in Grt-I garnets was mainly controlled by a “menzerite” type substitution mechanism, partially explaining the strong positive correlation between Mg and REE concentrations. In the Grt-II type garnets, enrichment may also have been co-controlled by coupling substitution and adsorption. In situ U–Pb dating of garnet shows that Grt-I-1 and Grt-I-2 material has isotopic ages of 92 ± 2 Ma (2σ, MSWD = 0.85) and 91 ± 2 Ma (2σ, MSWD = 0.96), respectively. The results were consistent with the previous ages obtained from the granodiorite and Molybdenite using Re–Os isotopic dating within error. This indicates that magma, skarn alteration, and mineralization were spatially and temporally related. In addition, it indicates that the Galale deposit is a typical Mg-skarn Au-Cu deposit. In the earliest stages of deposit development, ore-forming fluids with a high oxygen fugacity (fO2) have inherited their characteristics from the magma. The crystallization of many magnetites during the oxide stage has decreased oxygen fugacity in the metallogenetic system. This has resulted in a relatively low fO2 fluid for Au-Cu precipitation. The study demonstrates that the ore-fluid fO2 plays a vital role in metal migration, hence Au-Cu mineralization in Mg-skarn deposits.

New insights from thermohaline multiphase simulations into the mechanisms controlling vent fluid salinity following a diking event at fast-spreading ridges

Hydrothermal fluids expelled at mid-ocean ridge vent sites show a large spatial and temporal variability in exit temperatures and chlorinities. At the East Pacific Rise (EPR), 9°50.3'N, time series data for a 25+ year period reveal a correlation between these variations and magmatic diking events. Heat input from dikes appears to cause phase separation within the rising fluids splitting them into low-salinity vapor and high-salinity brine phases. The intrusion of a new dike is therefore likely to result in a characteristic salinity signal, with early post-eruptive fluids showing vapor-influenced low salinity and later brine-influenced fluids showing high salinity values.We here use a 2-D multiphase hydrothermal flow model to relate these observations to processes and properties within the sub-seafloor such as permeability, porosity, background flow rates, and phase separation as well as segregation phenomena. We have grouped the time evolution of vent fluid salinity into four temporal stages and have identified how multiphase flow phenomena control vertical salt mass fluxes within each stage. Rock porosity and permeability as well as background temperature of the undisturbed hydrothermal system control the duration of the four stages and maximum venting salinity. Based on our results, we are able to reproduce the characteristics of time-series data from the EPR at 9°50.3'N and infer the likely ranges of rock properties and the hydrothermal conditions within the oceanic crust beneath.