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The Bayan-Uul porphyry Au-Cu-(Mo) deposit occurs within the Mongol–Okhotsk Orogenic Belt, which is a part of the Central Asian Orogenic Belt. To understand geotectonic, petrogenesis, mineralization, and ore-forming fluid evolution of the Bayan-Uul deposit, we report petrographic and geochemical analyses of host rocks, mineralogy of ores, and fluid inclusion characteristics. Based on petrographic and mineralogical analyses, Cu, Mo, and Au mineralization occurs as disseminated and sulfide-bearing quartz–tourmaline veins hosted within granodiorites, monzodiorites, and diorite porphyry and tourmaline breccia. Four main alteration assemblages are identified: potassic, phyllic, argillic, and quartz–tourmaline alteration. The ore mineralogy of quartz–tourmaline veinlets are classified into A-type veinlets (quartz + tourmaline + chalcopyrite + magnetite + pyrite ± electrum), B-type veinlets (quartz + tourmaline + molybdenum + chalcopyrite + pyrite), and C-type veinlets (quartz + tourmaline + pyrite ± chalcopyrite). Fluid inclusions are found in quartz–tourmaline veinlets consisting mainly of liquid-rich two-phase (L-type), vapor-rich two-phase (V-type), and solid-bearing multi-phase (S-type) inclusions. The homogenization temperatures for the fluid inclusions in A-type, B-type, and C-type veinlets range from 215 to 490°C, 215 to 500 °C, and 160 to 350 °C and their salinity varies from 5.4 to 43.5 wt.%, 16 to 51.1 wt.%, and 3.4 to 24.1 wt.% NaCl equivalent, respectively. Coexistance of (L-type), (V-type), and (S-type) inclusions support fluid boiling. The δ18O values of ore fluids from different mineralizing A-, B-, and C-type veins are 8.7‰, 10.9‰, and 8.4‰, respectively, and the δ34S values of sulfide minerals range from −1.4‰ to 5.3‰, which indicates magmatic origin. [ABSTRACT FROM AUTHOR]

The Tagun‐Khin‐Dan gold deposit in the Mogok‐Mandalay‐Mergui Belt, Central Myanmar, is characterized by an array of quartz‐veins hosted in mudstone of the Kogwe Formation of the Carboniferous Mergui Group. Two major deformational stages were recorded in the area; (1) N‐S shortening and (2) uplifting and emplacement of various dykes and quartz veinlets. The N‐S shortening within the area lead the development of km‐scale faults, determined largely by the presence of a zone of major WNW‐ESE trending dextral strike‐slip faulting. Quartz veins in the deposit include: (1) type‐A quartz veins, parallel to the dextral NW‐SE trending major fault; and (2) type‐B quartz veins which occur as isolated parallel veins. Gold in the type‐A quartz vein is present as native gold and electrum locked within pyrite and associated with pyrite and galena and in the type‐B quartz veins as electrum associated with sulfide minerals such as pyrite, chalcopyrite, galena and sphalerite. The mineralization stages can be classified into the type‐A quartz vein stage and the type‐B quartz vein stage. Two type of fluid inclusions; liquid‐rich aqueous inclusions (L‐type) and vapor‐rich aqueous inclusions (V‐type) are identified in the type‐A quartz veins. The homogenization temperature of L‐type fluid inclusions of the type‐A quartz veins ranges from 203 to 321°C and salinity of the fluid inclusions varies from 0.4 to 1.6 wt% NaCl equiv. The homogenization temperature of V‐type fluid inclusions of type‐A quartz veins ranges from 290 to 340°C with a salinity ranging from 0.4 to 1.9 wt% NaCl equivalent. In the type‐B quartz veins, only liquid‐rich aqueous inclusions (L‐type) are identified. The type‐B quartz veins yielded low homogenization temperatures from 160 to 220°C, with low salinities from 0.2 to 1.9 wt% NaCl equiv. compared with those of the type‐A veins. The depth range of ore formation is estimated to be a shallow depth of less than 0.2 km based on fluid inclusion microthermometry. Fluid boiling is evident during the type‐A quartz vein stage, and fluid cooling and mixing in the later type‐B quartz vein stage. Precipitation of pyrite in the ore zone occurred as four recognized types: arsenic‐rich pyrite‐1, 2, 3 in the type‐A quartz veins and pyrite‐4 in the type‐B quartz veins. A positive relation between Au and As contents of pyrites suggests that the gold is present together with arsenic in the structure of pyrites of the type‐A quartz veins as solid solution in addition to as nanoparticle inclusions. The high Co and Ni contents of pyrites of both the type‐A and the type‐B quartz veins, with no evidence of CO2 in the system indicate that the ore‐forming fluids were epizonal magmatic‐hydrothermal fluids rather than metamorphic fluid. The hydrothermal fluids of the Tagun‐Khin‐Dan deposit were driven by faulting to form the mudstone‐hosted epithermal gold mineralization and related to continuing northwards movement of the Indian Plate that initiated the displacement on the strike‐slip Sagaing Fault. [ABSTRACT FROM AUTHOR]

The Woxi Au‐Sb‐W deposit is one of the largest polymetallic ore deposits in the Xuefengshan Range, southern China, hosted in low‐grade metamorphosed Neoproterozoic volcaniclastic rocks. The orebodies of the deposit are predominantly composed of banded quartz veins, which are strictly controlled by bedding and faults. Petrographic observations and geochemical results are reported on the occurrence of Au and properties of the ore‐forming processes for different stages in the deposit. The veins extend vertically up to 2 km without obvious vertical metal zoning. The ore‐forming process can be subdivided into four mineralization stages: Pre‐ore stage; Early stage (scheelite‐quartz stage); Middle stage (pyrite‐stibnite‐quartz stage); and Late stage (stibnite‐quartz sage). Four types of pyrite (Py0, Py1, Py2, and Py3) were identified in the ores and host‐rock: Py0 occurs as euhedral grains with voids in the core, ranging in size from 50 to 100 μm and formed mainly in the Pre‐ore stage and Early stage; Py1 occurs as subhedral grains. Small grains (around 10 μm) of Py1 form irregularly shaped clusters of variable size ranging from tens to hundreds of μm and mainly formed in the Middle stage; Euhedral‐subhedral fine‐grained Py2 formed in the Late stage; Minor subhedral fine‐grained Py3 was deposited in the Late‐stage. Stibnite is widely distributed in the Middle and Late stage ore veins. No systemic difference was recognized in mineralogical features among stibnite formed in different stages. In addition to native gold, the lattice bound Au+1 widely exists in Py1 and Py2 in the deposit, and widespread Py1 is considered as the main Au‐bearing mineral with the highest Au contents. Most elements (such as Co, Ni, Cu, As, Sb, Ba, and Pb) are considered to occur as solid solution within the crystal lattice and/or invisible nanoparticles in sulfides minerals. The Co/Ni ratio of most pyrite is lower than 1, suggesting that the metals in the ore‐forming fluid are sourced from sedimentary rocks. The coupled behavior between Au and As; Au and Sb suggests that the substitution of As and Sb in pyrite can enhance the incorporation of Au. Variation of trace elements in pyrites of different stages suggests some information on the mineralization processes: Large ion lithophile elements (such as Ba and Pb) are enriched in Py0 indicating that water‐rock reaction occurred in the Early stage; Fine‐grained Py1 with a heterogeneous distribution of elements suggests fast crystallization of pyrite in the Middle stage. [ABSTRACT FROM AUTHOR]

• OW-35 scale composed of a mixture of amorphous Al-rich opal-A and crystalline quartz. • Al participates by the isomorphous substitution between Si4+ and Al3+. • Silicic acid in solution exists as (Si(OH) 4) and (Si(OH) 3 O−). • Fe did not participate in the formation of the silica scale. • Aluminum ion was present as a 4-coordinate species. • 29Si MAS NMR spectrum showed three Q4 structures. In the Olkaria geothermal field, Kenya, a silica scale formed from geothermal water at the OW-35 production well was geochemically investigated. The geothermal water is highly alkaline, with a pH of 10.13, while the salinity is low, with a total Cl concentration of 432.4 ppm. The silica scale was precipitated from geothermal water with a high temperature (150–190 °C) in the OW-35 separator. For the mineral composition of the scale sample, it is mainly amorphous Opal-A and crystalline quartz. The SiO 2 content was 85.47 wt.%, and the Al 2 O 3 and Fe 2 O 3 contents were high at 3.16 and 1.11%, respectively, despite the fact that Al and Fe concentrations in the geothermal water were low. Based on the enrichment factor, Al was extremely concentrated from the geothermal water onto the silica scale during the formation, suggesting that Al may participate in the formation of the silica scale. For Fe, there was no contribution of Fe to the formation of silica scale, which was present as magnetite. This silica scale is a mixture of crystalline quartz and amorphous opal-A. The deposition mechanism was considered as follows. The quartz was formed by continuous and slow adsorption of monosilicic acid on the surface of the solid due to the slight supersaturated condition. On the other hand, opal-A was formed by a reaction between aluminate ion and monosilicic acid or monosilicate ion on the solid surface. [ABSTRACT FROM AUTHOR]

The Poboya Prospect lies along the North Northwest ‐ South Southeast Palu‐Koro Fault Zone in the central part of the West Sulawesi Arc. The geology of the area consists of the Palu Metamorphic Complex overlain by the Paleogene‐Neogene Tinombo Formation of volcanosedimentary rocks, the Celebes Molasse sediment, and Late Cenozoic granitic rocks. Petrography, scanning electron microscope with energy‐dispersive spectrometry (SEM‐EDS), electron probe microanalyzer (EPMA), and fluid inclusion microthermometry were carried out to examine vein textures, ore mineralogy, and characteristics of the ore‐forming fluid responsible for mineralization in the River Reef Zone, the Poboya Prospect. Textures of quartz‐carbonate veins in the River Reef Zone include massive micro‐comb, moss, colloform, crustiform, mosaic, feathery, flamboyant, lattice bladed, ghost bladed, parallel bladed, and saccharoidal textures representing primary growth, recrystallization, and replacement. The homogenization temperature and fluid salinity are 240–250°C and 0.3–0.7 wt% NaCl eq., respectively. Ore minerals precipitated in the early stage consist of electrum, naumannite‐aguilarite, chalcopyrite, pyrite, marcasite, sphalerite, and pyrrhotite. Apart from pyrrhotite, these ore minerals were also precipitated in the late stage along with selenopolybasite, freibergite, argyrodite, pyrargyrite, and galena. Selenium more preferably occurs as the crystallographic replacement of sulfur in naumannite‐aguilarite, argyrodite, pyrargyrite, selenopolybasite, and freibergite instead of as independent selenide minerals. The low‐sulfidation epithermal deposit in the River Reef Zone, the Poboya Prospect, illustrates the potential of the West Sulawesi Arc, particularly along the Palu‐Koro Fault Zone, to host epithermal gold mineralization. [ABSTRACT FROM AUTHOR]

The Shwe Min Bon Cu–Au skarn deposit lies within one of the largest Au–Cu belts in Myanmar. The deposit is situated along the Shan scarp zone, which marks the boundary between the Myanmar central basin to the west and the Shan plateau to the east. The Shwe Min Bon deposit comprises skarn‐type metasomatic alteration, and the Cu–Au mineralization occurs along the contact face between the Nwabangyi Dolomite and Shweminbon Formation and the Cretaceous dioritic rocks. The metasomatic process resulted in pro‐ and retrograde mineral assemblages in exoskarn. Hydrothermal activities in the Shwe Min Bon deposit are classified into prograde, retrograde stage I, and retrograde stage II. The prograde skarn is classified into a proximal garnet skarn with minor clinopyroxene and a distal wollastonite skarn. Chlorite, epidote, and tremolite–actinolite were formed during the retrograde stage I. Cu–Au mineralization mainly occurred in retrograde stage I, which was characterized by moderate temperatures (260–320 °C) and fluid with a moderate salinity (5.0–6.0% NaCl equiv.). Low temperature (180–200 °C) and low salinity (2.0–3.0% NaCl equiv.) were responsible for retrograde stage II. Au mineralization is mainly associated with chalcopyrite and tennantite in retrograde stage I and with tellurobismuthite in retrograde stage II. The Shwe Min Bon Cu‐Au skarn deposit lies within one of the largest gold‐copper belts in Myanmar. The metasomatic process resulted in prograde and retrograde mineral assemblages in exoskarn. Gold mineralization is mainly associated with chalcopyrite and tennantite in the retrograde stage I and with tellurobismuthite in the retrograde stage II. [ABSTRACT FROM AUTHOR]

• Visually and chemically diverse scales are found along the movement of geothermal waters at the Dieng geothermal power plant. • Geochemical modeling is examined to guide the determination and the calculation of mineral assemblage in the scale at different locations. • The scale formation mechanisms were directly correlated to the change of properties of the geothermal fluid at each location. The geothermal water discharged from the production well at the Dieng geothermal power plant experiences various drastic changes depending on the specific structure. As a result, various siliceous scales were found along the movement of the geothermal water at the Dieng geothermal power plant. To elucidate the geochemical property relationship between siliceous scales and geothermal waters at different locations, both the scale and the geothermal water samples were collected from (1) the inside of the two-phase pipeline, (2) the inside of the brine pipeline, and (3) at the open canal. The saturation index of the minerals was calculated based on the properties of the geothermal waters at each location to predict minerals that are possible to form. By comparing the properties of the scale and the mineral saturation index, quantitative mineral assemblage at each location was calculated, and the scale formation can be explained as follows. (1) Scale in the two-phase pipeline was composed of (Al, K)- and Fe-rich silicate, amorphous silica, and sulfide minerals formed at high temperature and near-neutral pH. The (Al, K)-rich and the Fe2+-rich silicates were controlled by the oversaturation of clinoptilolite and minnesotaite, and the amorphous silica was formed. The sulfide minerals were formed due to the high sulfur fugacity (fs 2). (2) Scale in the brine pipeline was mainly composed of amorphous silica containing a small amount of (Al, K)-rich silicate formed under low pH (4∼5) and high-temperature conditions. (Al, K)-rich silicates were still precipitated even after acidification, likely due to the oversaturation of clinoptilolite above pH ∼4, and then the amorphous silica was formed. (3) Scale at the open canal was mainly composed of amorphous silica with small particles of hydrous ferric oxide (HFO), formed under an oxidizing condition at low temperature and low pH (4∼5). HFO reacted with silicic acid in geothermal water to form Fe3+-rich silicate that chemically resembles nontronite. The mineral with the highest proportion was amorphous silica in all three siliceous scales. Although the saturation index of amorphous silica was small, precipitation of amorphous silica may be induced and accelerated due to the adsorption of silicic acid on the (Al, K)-rich silicate and the Fe2+-rich silicate at high temperature and on the Fe3+-rich silicate at low temperature because of high surface area. The adsorbed silicic acid polymerizes on the silicate minerals. [ABSTRACT FROM AUTHOR]

Myanmar is endowed with abundant Sn-W mineralization, pre-eminent amongst which is the world-class Mawchi deposit. In the Mawchi area, N-S trending vertical or steeply dipping quartz veins are hosted by both Eocene granite and Carboniferous to Early Permian metasediments. Three stages of ore formation are recognized; (i) tourmaline-cassiterite stage (ii) main ore stage and (iii) sulfide stage. Tourmaline, cassiterite and pyrite-I are early-formed minerals and are representative of the first stage. Their deposition continued together with wolframite, scheelite, molybdenite, arsenopyrite, pyrite-II, fluorite and danalite, which form the second stage. This was followed by the successive deposition of sulfides such as chalcopyrite, sphalerite, galena and Pb-Bi sulfides. A 40 Ar/ 39 Ar magmatic biotite plateau age of 41.50 ± 0.16 Ma (MSWD = 2.5) is determined for the Mawchi biotite granite which we interpret as the time the granite cooled through the biotite blocking temperature, and is consistent with a previously reported LA-ICP-MS U-Pb zircon concordia age of 42.72 ± 0.94 Ma (MSWD = 2). A molybdenite Re-Os model age of 42.4 ± 1.2 Ma indicates that Sn-W mineralization was synchronous with late Eocene granitic magmatism. Our 40 Ar/ 39 Ar hydrothermal muscovite plateau ages from the tourmaline granite (40.14 ± 0.14 Ma; MSWD = 1.48) and quartz vein selvages (40.80 ± 0.12 Ma; MSWD = 0.47) define the timing of hydrothermal alteration and simultaneous veining that accompanied the late stage of ore forming at Mawchi. Fluid inclusion microthermometry from cassiterite, scheelite, quartz, and fluorite reveals that ore fluids in the cassiterite-tourmaline stage and main ore stage are characterized by moderate homogenization temperatures (Th = 260–345 °C) and salinities (4.5–15.7 wt% NaCl equiv), while the sulfide stage is characterized by lower temperatures (Th = 175–260 °C) and moderate to low salinity (2.5–13 wt% NaCl equiv). The mean δ 34 S of all sulfides is 2.9 ± 2.9‰, which is suggestive that the overall system is dominated by magmatic sulfur. The similarity of δ 34 S values in galena and Pb-Bi sulfides (−1.3 to 2.7‰) suggest that sulfur, and inference the Pb and Bi were transported by a common fluid, probably of magmatic origin. The calculated δ 18 O H2O of the hydrothermal fluid associated with cassiterite and tourmaline is 7.3–8.4‰. Scheelite and quartz deposition is characterized by lighter δ 18 O H2O values (2.1–4.9‰) indicating that the ore fluid might be mixed with another source of water, perhaps, meteoric. Hydrogen isotopic compositions (δD = −51 to −121‰) again indicate that origin of the ore fluid is magmatic, but δD (∼−120‰) is low enough to support the δ 18 O H2O data that suggests, in part, a meteoric water component to the hydrothermal fluids at Mawchi. [ABSTRACT FROM AUTHOR]

The Huangshaping deposit is a world-class W–Mo–Pb–Zn–Cu polymetallic deposit that formed during the Jurassic magmatic event in the central Nanling region, South China. In order to reveal the three-dimensional development of mineralization and alteration in this complicated fluid-rock system, four typical hydrothermal K-feldspar samples were collected from potassic alteration zones at different elevation levels around main W–Mo ore bodies, followed by precise trace element analysis and 40 Ar/ 39 Ar dating. The results show that these K-feldspars have a pronounced lanthanide tetrad effect with high contents of Ga, Ta, Nb, U, Y and HREE but low concentrations of Ba, Sr, Eu and Zr, suggesting a hydrothermal origin. Additionally, correlation between the Ca/Cl/K ratios and the apparent ages suggest that metasomatic fluids played an important role in the formation of the hydrothermal K-feldspars. The plateau 40 Ar/ 39 Ar ages which represent the timing of potassic alteration vary from 152.9 ± 0.5 to 154.3 ± 0.6 Ma, spatially showing younger trends from north to south and from shallow to deep. These dates correspond to the previous published molybdenite Re–Os data variations in different elevation levels, which record the mineralization event with relatively older ages ranging from 153.8 to 159.4 Ma. Combined with the spatial relation analysis among samples, the fluid migration rates associated with the mineralization and alteration are calculated at 10–100 m Ma −1 . Thus, we propose a fluid downward migration model for the Huangshaping polymetallic deposit. [ABSTRACT FROM AUTHOR]

This study investigated the precipitation behavior of silicic acid (Si) and iron (Fe) when acidic and weakly alkaline geothermal waters were mixed at various mixing ratios (R) (the proportion of the acidic geothermal water, which ranged from 1 to 9) at 85 ˚C under an oxidizing atmosphere at the Hatchobaru Geothermal Power Plant in Japan. The pH and total Fe concentration of the acidic and weakly alkaline geothermal waters were 2.8 and 8.7 at 25 ˚C and 6.5 and 0.5 ppm, respectively. The pH of the mixed geothermal waters at 85 ˚C ranged from 8.11 to 3.30. Although Si precipitated after they were mixed at R of 1 to 4, Fe precipitated immediately after mixing, independent of R. The amount of Fe precipitated also increased with increasing R (thus increasing the Fe initial concentration). The precipitates were divided into two groups based on their chemical composition: those with a high Si/Fe atomic ratio in the range of 100 to 150, found at R of 1 to 4, and those with a Si/Fe atomic ratio lower than 10, found at R of 5 to 9. Silicic acid polymerized after they were mixed at R between 1 and 3 and the polymerization was not observed at R above 4. Fe was present as colloidal hydrous ferric oxide (HFO) and hydrolyzed species of Fe3+ in the acidic geothermal water. From these results, it may be concluded that the precipitates with a high Si/Fe atomic ratio were formed due to the aggregation of polysilicic acid particles with Fe at R from 1 to 3, whereas the precipitates with low Si/Fe atomic ratios were formed owing to the aggregation of HFO bonding monosilicic acid because of the sudden increase in pH at all R. There was a large amount of precipitate (the sum of Fe and Si mmol) at R from 1 to 4, indicating that delaying the polymerization of the silicic acid is key in preventing large precipitation of Si and Fe. Judging from the saturation indices for minerals commonly found in geothermal fields, the amorphous precipitates with high and low Si/Fe atomic ratios may be precursors of silica polymorph and nontronite as a Fe(III) silicate because they can be formed at R from 1 to 9. [ABSTRACT FROM AUTHOR]

Karavansalija ore zone is situated in the Serbian part of the Serbo-Macedonian magmatic and metallogenic belt. The Cu-Au mineralization is hosted mainly by garnet-pyroxene-epidote skarns and shifts to lesser presence towards the nearby quartz-epidotized rocks and the overlying volcanic tuffs. Within the epidosites the sulfide mineralogy is represented by disseminated cobalt-nickel sulfides from the gersdorfite-krutovite mineral series and cobaltite, and pyrite-marcasite-chalcopyrite-base metal aggregates. The skarn sulfide mineralization is characterized by chalcopyrite, pyrite, pyrrhotite, bismuth-phases (bismuthinite and cosalite), arsenopyrite, gersdorffite, and sphalerite. The sulfides can be observed in several types of massive aggregates, depending on the predominant sulfide phases: pyrrhotite-chalcopyrite aggregates with lesser amount of arsenopyrite and traces of sphalerite, arsenopyrite-bismuthinite-cosalite aggregates with subordinate sphalerite and sphalerite veins with bismuthinite, pyrite and arsenopyrite. In the overlying volcanoclastics, the studied sulfide mineralization is represented mainly by arsenopyrite aggregates with subordinate amounts of pyrite and chalcopyrite. Gold is present rarely as visible aggregate of native gold and also as invisible element included in arsenopyrite. The fluid inclusion microthermometry data suggest homogenization temperature in the range of roughly 150-400°C. Salinities vary in the ranges of 0.5-8.5 wt% NaCl eq for two-phase low density fluid inclusions and 15-41 wt% NaCl eq for two-phase high-salinity and three-phase high-salinity fluid inclusions. The broad range of salinity values and the different types of fluid inclusions co-existing in the same crystals suggest that at least two fluids with different salinities contributed to the formation of the Cu-Au mineralization. Geothermometry, based on EPMA data of arsenopyrite co-existing with pyrite and pyrrhotite, suggests a temperature range of 240-360°C for the formation of the arsenopyrite, which overlaps well with the data for the formation temperature obtained through fluid inclusion microthermometry. The sulfur isotope data on arsenopyrite, chalcopyrite, pyrite and marcasite from the different sulfide assemblages (ranging from 0.4‰ to +3.9‰ δ34SCDT with average of 2.29 δ34SCDT and standard deviation of 1.34 δ34SCDT) indicates a magmatic source of sulfur for all of the investigated phases. The narrow range of the data points to a common source for all of the investigated sulfides, regardless of the host rock and the paragenesis. The sulfur isotope data shows good overlap with that from nearby base-metal deposits; therefore the Cu-Au mineralization and the emblematic base-metal sulfide mineralization from this metallogenic belt likely share same fluid source. [ABSTRACT FROM AUTHOR]

The gold mineralization at the Tau deposit in northeastern Botswana can be distinguished into two stages. The first stage of mineralization consists of invisible gold associated with early, sulfur‐rich arsenopyrite (Apy1). The second stage is characterized by native gold associated with late, sulfur‐poor arsenopyrite (Apy2). This study aims to constrain the nature of the ore‐forming fluid at the Tau deposit on the basis of fluid inclusion microthermometry and arsenopyrite geothermometry. Quartz crystals closely associated with gold‐bearing sulfides (Apy1) from the host rock host three types of fluid inclusions occurring in the same assemblages: Type I, two‐phase aqueous fluid inclusions, Type II three‐phase aqueous‐carbonic fluid inclusions and Type III one‐ or two‐phase CO2‐rich fluid inclusions. Microthermometric and Raman spectroscopic studies revealed the dominance of coexisting H2O+NaCl (Type I) and CO2N2CH4 (Type III) fluid inclusions. The coexisting Type I and Type III fluid inclusions could represent products of the immiscibility of a homogenous H2OCO2NaClN2CH4 primary ore fluid. The salinity of Type I (calculated from melting temperature of ice) and Type II (calculated from dissolution temperature of clathrate) fluid inclusions vary from 3.4 to 9.2 wt% NaCl equiv. and 5.8 to 9.8 wt% NaCl equiv., respectively. The overall fluid inclusion salinity range (<10 wt% NaCl equiv.) and gas compositions of fluids suggest that the primary ore‐forming fluid at the Tau deposit was of low salinity and H2OCO2N2CH4NaCl composition. Integration of fluid inclusion microthermometry and arsenopyrite geothermometer results suggest that the first stage and second stages of gold mineralization and the associated alteration at the Tau deposit occurred at pressure and temperature conditions of 75–145 MPa and 290–370°C and 85–160 MPa and 330–370°C, respectively. These results suggest that there was an increase in temperature from the first stage to the second stage of mineralization, resulting in the recrystallization of invisible gold‐bearing arsenopyrite in the first stage to form native gold‐bearing arsenopyrite in the second stage. Fluid composition and the estimated physico‐chemical conditions at the Tau deposit confirm that gold was transported as reduced bisulfide complexes and initial gold deposition was likely caused by a reduction in sulfur contents as a result of sulfidation reactions and pressure‐induced phase separation (fluid immiscibility). [ABSTRACT FROM AUTHOR]

The Mupane gold deposit, which is one of the numerous gold occurrences in the Tati Greenstone Belt in the northeastern part of Botswana, consists of four orebodies, namely Tau, Tawana, Kwena, and Tholo deposits. The present research, which focuses on the genesis of the Tau deposit, was based on ore petrography, mineral chemistry of sulfides, and sulfur isotope data. Mineralogical characteristics of the host rocks indicate that banded iron formation at the Tau deposit includes iron oxides (magnetite), carbonates (siderite and ankerite), silicates (chlorite and amphibole), and sulfides (arsenopyrite and pyrrhotite). The deposit features arsenopyrite‐rich zones associated with biotite‐chlorite veins, which are indicative of the precipitation of arsenopyrite concomitant with potassic alteration. The replacement of magnetite by pyrrhotite in some samples suggests that sulfidation was likely the dominant gold precipitation mechanism because it is considered to have destabilized gold‐thiocomplexes in the ore‐forming fluids. Based on textural relationships and chemical composition, arsenopyrite is interpreted to reflect two generations. Arsenopyrite 1 is possibly early in origin, sieve textured with abundant inclusions of pyrrhotite. Arsenopyrite 1 was then overgrown by late arsenopyrite 2 with no porous textures and rare inclusions of pyrrhotite. Gold mineralization was initiated by focused fluid flow and sulfidation of the oxide facies banded iron formation, leading to an epigenetic gold mineralization. The mineralogical assemblages, textures, and mineral chemistry data at the Tau gold deposit revealed two‐stage gold mineralizations commencing with the deposition of invisible gold in arsenopyrite 1 followed by the later formation of native gold during hydrothermal alteration and post‐depositional recrystallization of arsenopyrite 1. Laser ablation inductively coupled plasma mass spectrometric analysis of arsenopyrite from the Tau deposit revealed that the hydrothermal event responsible for the formation of late native gold also affected the distribution of other trace elements within the grains as evidenced by varying trace elements contents in arsenopyrite 1 and arsenopyrite 2. The range of δ34S of gold‐bearing assemblages from the Tau deposit is restricted from +1.6 to +3.9‰, which is typical of Archean orogenic gold deposits and indicates that overall reduced hydrothermal conditions prevailed during the gold mineralization process at the Tau deposit. The results from this study suggest that gold mineralization involved multi‐processes such as sulfidation, metamorphism, deformation, hydrothermal alteration, and gold remobilization. [ABSTRACT FROM AUTHOR]

We report for the first time the geochemistry of rare earth elements (REE) in the weathered crusts of I-type and calc-alkaline to high-K (shoshonitic) granitic rocks at Mamasa and Palu region, Sulawesi Island, Indonesia. The weathered crusts can be divided into horizon A (lateritic profile) and B (weathered horizon). Quartz, albite, kaolinite, halloysite and montmorrilonite prevail in the weathered crust. Both weathered profiles show that the total REE increased from the parent rocks to the horizon B but significantly decrease toward the upper part (horizon A). LREE are enriched toward the upper part of the profile as shown by La/Yb value. However, HREE concentrations are high in horizon B1 in Palu profile. The total REE content of the weathered crust are relatively elevated compared to the parent rocks, particularly in the lower part of horizon B in Mamasa profile and in horizon B2 in Palu profile. This suggests that REE-bearing accessory minerals may be resistant against weathering and may remain as residual phase in the weathered crusts. The normalized isocon diagram shows that the mass balance of major and REE components between each horizon in Mamasa and Palu weathering profile are different. The positive Ce anomaly in the horizon A of Mamasa profile indicated that Ce is rapidly precipitated during weathering and retain at the upper soil horizon. [ABSTRACT FROM AUTHOR]

Geochemical studies were conducted on the hydrothermally altered granitic rocks in the Ranong and Takua Pa tin-fields in southern Thailand in order to investigate the mode of occurrence of REE (rare earth elements), with emphasis placed on a potential REE resource associated with granitic rocks in the Southeast Asian Tin Belt. The total REE (Σ REE) content of altered granitic rocks ranges from 130 to 350 ppm at Haad Son Paen (which is presently mined for kaolin clay) in the Ranong tin-field, and that of altered granitic rocks and kaolinite veinlets reaches up to 424 ppm and 872 ppm, respectively, at Nok Hook in the Takua Pa tin-field. Rare earth elements in the altered granitic rocks and kaolinite veinlets show a relatively flat chondrite-normalized pattern, thus enriched in heavy REE compared with the original granitic rocks and their weathered crusts. At Nok Hook ( Takua Pa), the Σ REE content of kaolinite separated from an altered granitic rock by elutriation is 1313 ppm, a Σ REE amount about four times higher than that of whole-rock composition of the altered granitic rock. Chondrite-normalized REE patterns of the elutriated kaolinite and of the altered granite are relatively flat. Sequential extraction experiments suggest that 41 and 85 percent of REE are present as ion exchangeable-form in the altered granitic rock, and in the kaolinite veinlets, respectively. In addition, more than 90% of REE in the kaolinite veinlets are present as the acid-soluble state. On the other hand, the Σ REE content of kaolinite veinlets and of the kaolinite concentrated by elutriation from an altered granitic rock at Haad Som Paen ( Ranong) is 70 ppm and 75 ppm, respectively, thus enrichment of REE in kaolinite was not confirmed. In addition, by the sequential extraction experiments, 23% and 4% of REE were extracted from the altered granitic rock and the kaolinite veinlets at Haad Som Paen. In the altered granitic rocks at Haad Som Paen, REE are present as refractory phases, and REE in the acid-soluble states had been leached by hydrothermal fluid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Central Magmatic-Volcanic Belt (CMVB) hosts several Au-Cu ore types and Thone Myae Song deposit. • Formation of CMVB is related to the eastward subduction of Indian Ocean floor during the Cretaceous. • Sericite-carbonate alteration is important as confines to the margins of mineralized veins. • Fluid immiscibility was a major trigger to the precipitation of gold and base metals at EE3 deposit. Several gold deposits are found in the Central Magmatic-Volcanic Belt (CMVB) of Myanmar, which forms a nearly N–S-trending, 1500-km-long arc extending from the Andaman Sea to northern Myanmar. The CMVB consists of Cretaceous granitoids intruded into folded andesites and pillow basalts (Mawgyi Andesite) which rest on cherts, talc-schists, mudstones and phyllites. The EE3 gold deposit is part of gold mineralization in the Thone Myae Song area, located in the Kawlin–Wuntho block in the northern part of the CMVB. The orebodies occur as sulfide-bearing massive quartz veins hosted by Mawgyi Andesite. Based on the mineral assemblages and cross-cutting relationships, three mineralization stages are identified in the EE3 gold deposit: Stage-I quartz-carbonate-sulfide veins; Stage-II quartz-carbonate veins intersecting the Stage-I veins; and Stage-III quartz-carbonate-sulfide veins parallel to the Stage-I veins. The main hydrothermal alteration minerals are sericite, epidote, chlorite and calcite. Three main types of fluid inclusions were distinguished from the mineralized quartz veins hosted by Mawgyi Andesite: liquid-rich aqueous fluid inclusions (Type A), vapor-rich aqueous inclusions (Type B), and H₂O-CO₂-NaCl inclusions (Type C). The latter occurs only in the Stage-I veins. The ore-forming conditions are estimated from fluid inclusions in the Stage-I, Stage-II and Stage-III veins to be at 180 °C and 28 bars, 176 °C and 26 bars, and 158 °C and 21 bars, respectively. The formation pressures of the Stage-I, Stage-II and Stage-III mineralization correspond to a shallow depth of 300 m, 280 m, and 225 m, respectively. Based on the ore and alteration mineral assemblages, and estimated temperature and pressure conditions of the mineralization, the EE3 gold deposit was formed in an epithermal condition. [ABSTRACT FROM AUTHOR]

In order to elucidate the formation mechanism of low-sulfidation epithermal gold deposit, the adsorption of [Au(S2O3)2]3− (a model compound for gold(I) complex ion) on alumina gel (a model compound for the aluminum-bearing minerals) and change in chemical state of [Au(S2O3)2]3− after adsorption on the surface of alumina gel were investigated as a basic model experiment. In the pH range from 4 to 6, the amount of [Au(S2O3)2]3− adsorbed on alumina gel decreased with increasing pH and decreased drastically between pH 6 and 7, and then approached zero above pH 8 at 30°C. At 60°C, the amount of gold adsorbed above pH 7 was enhanced compared with that at 30°C. This adsorption tendency indicates that [Au(S2O3)2]3− is mainly adsorbed by electrostatic interaction between negative charges of [Au(S2O3)2]3− and positive charges of alumina gel because of its isoelectric point around pH 9. The chemical state of gold after adsorption of [Au(S2O3)2]3− on alumina gel was examined using X-ray absorption near edge structure (XANES). The result showed that [Au(S2O3)2]3− was spontaneously reduced to elemental gold even in the absence of specific reducing agents after adsorption on alumina gel. This reduction reaction might occur by two steps: (i) disproportionation of the adsorbed [Au(S2O3)2]3− at the surface of alumina gel, and (ii) spontaneous reduction of the resulting gold(III) complex ions on the surface of alumina gel. The experimental results suggest that aluminum plays an important role in the concentration of gold(I) complex ions and subsequent reduction of gold during the formation of low-sulfidation epithermal gold deposits. [ABSTRACT FROM AUTHOR]

The Palaeocene granites of Dawei and the Eocene granites of Mawchi both host large‐ to medium‐scale Sn–W deposits and represent two metallogenically prominent segments of the SE Asian tin belt in Myanmar. Combined with previous geochemical data, new whole‐rock elemental and isotope analyses of tin‐mineralized granites were obtained to provide insights into sources involved in the formation of these granites. Tin granites in both regions are highly siliceous (76–80 wt%), peraluminous (A/CNK = 1.02–1.32), depleted in Sr, Ba, Zr and Ti but elevated in Li, Sn, Rb, Pb and U. The highly evolved nature of these granites is emphasized by their high Y/Ho (33–49) ratios as well as low Nb/Ta (1–11) and Zr/Hf (8–24) ratios. The chondrite‐normalized REE patterns, with M‐type tetrad effects (TE1,3 = 1.04–1.16) and strongly negative Eu anomalies (0.01–0.34), point to fractional crystallization of feldspars and other accessories during the evolution of the parental magma and are also indicative of the magmatic to hydrothermal transition that resulted in the pervasive mineralization of these bodies. The Pb isotopic compositions are variably enriched, with age‐corrected 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values ranging from 18.620 to 18.898, 15.728 to 15.770, and 38.288 to 39.402, respectively, all of which point to derivation from evolved crustal material. This is consistent with their low ɛNd(t) and ɛHf(t) values of −10.11 to −11.29, and −5.86 to −8.93, respectively. Collectively, these data suggest that crustal melting, fractional crystallization and late‐stage magma–fluid interactions all played important roles in the generation of the tin‐mineralized granites of Myanmar. [ABSTRACT FROM AUTHOR]

To apply the Fe3+-type cation exchange resin, Fe3+-type UBK 10, which is an effective adsorbent of selenite ions, for the removal and recovery of phosphate ions (PO 4 3−), the adsorption mechanism of PO 4 3− to the Fe3+-type UBK 10 resin was investigated. To elucidate the aforementioned mechanism, the chemical state of Fe3+ in the Fe3+-type UBK 10 resin and the adsorption mode of PO 4 3− into the adsorbent were examined via 57Fe Mössbauer spectroscopy and Fe and P K-edge X-ray absorption spectroscopy. The optimum pH for the adsorption of PO 4 3− was found to be approximately 6 and the adsorbed PO 4 3− was rapidly desorbed using 6 mol dm-3 hydrochloric acid (HCl) through the conversion of Fe3+ to FeCl 4 -, which is practical for the removal and recovery of PO 4 3−. The Fe K-edge X-ray absorption near-edge structure (XANES) spectra showed, through the appearance of three isobestic points, that Fe3+ in the Fe3+-type UBK 10 resin exists as the following four species in equilibrium, depending on the pH: two monomeric hydrolytic species of ferric ions, (-S) 2 FeOH and (-S)Fe(OH) 2 , a μ-oxo dimer with corner sharing structure, (-S) 2 Fe-O-Fe(S-) 2 , and a dihydroxo dimer with edge sharing structure, (-S) 2 Fe-(OH) 2 -Fe(S-) 2 (S: SO 3 group in UBK 10). It should be emphasized that a PO 4 3− can combine with a (-S) 2 Fe-(OH) 2 -Fe(S-) 2 site at pH of 6, which is an optimum pH for adsorption of PO 4 3−, forming a bidentate-binuclear configuration, (-S) 2 Fe-(OH) 2 (OPO 2 O)-Fe(S-) 2 , through the formation of Fe-O-P bonds. [ABSTRACT FROM AUTHOR]

Most of the granite-related Sn–W deposits in Myanmar are located in the Western Granitoid Province (WGP) of Southeast Asia. The Tagu deposit in the southern part of the WGP is a granite related Sn–W deposit. The biotite granite is composed of quartz, feldspars (plagioclase, orthoclase, and microcline), and micas (muscovite and biotite) and belongs to S-type peraluminous granite. Abundances of large-ion lithophile elements (LILEs), such as Rb, K, and Pb, coupled with the deficiency of high-field-strength elements (HFSEs), such as Nb, P, and Ti, indicate that the parental magma for the Tagu granite was derived from the lower continental crust at syn-collisional setting. Mineralized veins consist of early-formed oxide ore minerals, such as cassiterite and wolframite, which were followed by the formation of sulfide minerals. Three main types of fluid inclusions were distinguished from the mineralized quartz veins hosted by granite and metasedimentary rocks: Type-A—two phases, liquid (L) + vapor (V) aqueous inclusions; Type-B—two phases, vapor (V) + liquid (L) vapor-rich inclusions; And type-C—three phases, liquid + CO2-liquid + CO2-vapor inclusions. Quartz in the veins hosted in granite corresponding with earlier deposition contains type-A, type-B, and type-C fluid inclusions, whereas that in the veins hosted in metasedimentary rocks corresponding with later deposition contains only type-A fluid inclusions. The homogenization temperatures of type-A inclusions range from 140 °C to 330 °C (mode at 230 °C), with corresponding salinities from 1.1 wt.% to 8.9 wt.% NaCl equivalent for quartz veins hosted in metasedimentary rocks, and from 230 °C to 370 °C (mode at 280 °C), with corresponding salinities from 2.9 wt.% to 10.6 wt.% NaCl equivalents for quartz veins hosted in granite. The homogenization temperatures of type-B vapor-rich inclusions in quartz veins in granite range from 310 °C to 390 °C (mode at 350 °C), with corresponding salinities from 6.7 wt.% to 12.2 wt.% NaCl equivalent. The homogenization temperatures of type-C H2O–CO2–NaCl inclusions vary from 270 °C to 405 °C (mode at 330 °C), with corresponding salinities from 1.8 wt.% to 5.6 wt.% NaCl equivalent. The original ascending ore fluid was probably CO2-bearing fluid which evolved into two phase fluid by immiscibility due to pressure drop in the mineralization channels. Furthermore, the temperature and salinities of two-phase aqueous fluids were later most likely decreased by the mixing with meteoric water. The salinities of the type-B vapor-rich inclusions are higher than those of the type-C CO2-rich inclusions, which may have resulted from CO2 separation from the fluids. The escape of gases can lead to an increase in the salinity of the residual fluids. Therefore, the main ore-forming mechanisms of the Tagu Sn–W deposit are characterized by fluid immiscibility during an early stage, and fluid mixing with meteoric water in the late stage at a lower temperature. [ABSTRACT FROM AUTHOR]

The Xiangzhong metallogenic province (XZMP), the largest polymetallic mineralization province in southern China, is known for its large number of Sb and Sb-polymetallic deposits (>100). In this study, detailed microscope observation, trace element, and sulfur isotopic analyses were performed on stibnite from the Xikuangshan, Woxi, and Banxi deposits in the XZMP to constrain the ore genesis. Stibnite from three deposits appears similar under backscattered electron imaging and has similar major elements contents. Detectable trace elements in stibnite are Fe, Cu, Zn, As, and Pb. Base metals (Cu, Pb, and Zn) are enriched in stibnite from the Woxi deposit but are depleted in stibnite from the Xikuangshan and Banxi deposits. Gold is detectable only in stibnite from the Woxi deposit. Cu, As, and Pb mainly occur as solid solutions within the crystal lattice in stibnite, while micro-scale inclusions of Fe- and/or Zn-rich phases are also observed. The δ34S values of stibnite from three deposits are distinct but with narrow ranges: +6.8 to +10.2 ‰; +5.5 to +6.5 ‰; −4.2 to +0.1 ‰ for the Xikuangshan, Banxi, and Woxi deposits, respectively. The δ34S values of stibnite suggest that the underlying basement rocks are the potential source of sulfur for the Sb mineralization in the Xikuangshan and Banxi districts while sulfur for the Sb mineralization of the Woxi district may have originated from a deep magmatic source. In addition, a positive trend between the δ34S values of stibnite and sampling depth suggests an input of the 34S-rich basin brine during the mineralization in the Woxi district. We propose a genetic model for the Sb mineralization in the XZMP: Fluids rich in Sb, Au, W, Cu, Pb, and Zn related to igneous activities ascended via regional deep faults and mixed with 34S-rich basin brine. Ore minerals of Sb, Au, and W were deposited within structural traps resulting in the Woxi-type deposits. The basement-derived deep fluids driven by orogenic leached Sb and related metals from the basement metamorphic rocks, which migrated via the regional faults and mixed with cold near surface meteoric water to form the Xikuangshan-type deposits. • In situ trace element and sulfur isotope results of stibnite are reported. • Metals and sulfur for the Woxi deposit may be from a magmatic source. • Mineralization at Xikuangshan and Banxi is related to Proterozoic basement rocks. • Mixing of sulfur-rich basin brine resulted in the stibnite deposition at Woxi. • Mixing of meteoric water caused the stibnite deposition at Xikuangshan and Banxi. [ABSTRACT FROM AUTHOR]

The orientation distribution of dilational fractures is affected by the state of stress around the fractures and by the pressure of the fluid that opened the fractures. Thus, the distribution can be inverted to determine not only the stress but also the pressure condition at the time of vein formation. However, epithermal ore veins that we observe today are the results of a great number of intermittent upwelling of overpressured fluids with different pressures. Here, we define driving pressure index (DPI) as the representative non-dimensionalized fluid pressure for the fluids. We collected the orientations of ∼1000 ore veins in the Hishikari gold mine, which were deposited at around 1 Ma, in southern Kyushu, Japan. It was found that the majority of the veins were deposited under an extensional stress with a NW-SE-trending σ 3 -axis and a northeasterly-inclined σ 1 -axis with relatively high stress ratio. The representative driving pressure ratio was ∼0.2. Data sets obtained at different depths in the mine indicated a positive correlation of representative driving pressure ratios with the depths. The correlation suggests repeated formation and break of pressure seals during the mineralization. Our compilation of the Pliocene–Quaternary stress regimes in southern Kyushu, including the result of the present study, suggests that epithermal gold mineralization was associated with distributed extensional deformations in southern Kyushu, and strain localization into an intra-arc rift seems to have terminated the mineralization. [ABSTRACT FROM AUTHOR]

Tin-tungsten-associated granites occur widely in the Dawei region of the Southeast Asian tin belt. In this contribution, we present a detailed study of zircon U–Pb geochronology and whole-rock and zircon elemental geochemistry for the Wagone and Hermyingyi granites in southern Myanmar, with the aim of determining their petrogenesis, mineralization associations, and tectonic setting. These granitic rocks, which belong to the high-K calc-alkaline series A 2 -type granites, are characterized by high concentrations of SiO 2 (75.2–82.5%), Rb (264–927 ppm), Th (18.4–58.3 ppm), U (10.4–18.3 ppm), and Y (33.5–212 ppm), but low contents of TFeO (0.57–3.45%), CaO (0.23–0.86%), MgO (0.02–0.19%), MnO (0.01–0.38%), TiO 2 (0.01–0.10%), P 2 O 5 (0.003–0.012%), Ba (3–162 ppm), and Sr (4.3–34.4 ppm). Hydrothermal zircons from the mineralized Wagone pluton show an anomalous lack of zoning and vermicular, spongy internal structures, and they contain high concentrations of Ti, Y, U, and light REEs but low Th/U ratios (mostly < 0.1). These features suggest slow crystallization from a U-enriched and Th-depleted residual magmatic fluid under relatively cool and reducing conditions. LA-ICPMS U–Pb dating of magmatic and hydrothermal zircons from the two granites yielded concordant ages of 61–60 Ma, indicating an Early Paleogene magmatic-mineralization event. Geochemical and geochronological data suggest that these A-type granites have a crustal origin and were produced by partial melting of a felsic clay-rich source in a back-arc extensional setting. The magmas may have ascended relatively slowly in the crust and experienced crystal fractionation and upper crustal contamination, contributing to intensive Sn–W mineralization in the Dawei area. [ABSTRACT FROM AUTHOR]

The Sanjin deposit is one of three major ore zones hosted by Pleistocene quartz-adularia veins being mined at the Hishikari low-sulfidation epithermal gold mine, which has produced more than 242 t of gold at an extraordinary average grade since 1985. Hydrothermal alteration zoning of the Sanjin deposit was examined with respect to mineralogy, geochemistry, fluid inclusion microthermometry, and oxygen and hydrogen isotopes. Clay minerals are dominated by interstratified chlorite-smectite (C/S) and interstratified illite-smectite (I/S) with <20% smectite. Epidote and prehnite are recorded for the first time at Hishikari in the southeastern part of the Sanjin deposit, typically coexisting with chlorite. Trapping temperatures of fluid inclusions from associated ore zone quartz veins typically range from 195 to 230 °C, with higher temperatures prevalent in the southeastern part of the Sanjin deposit. The calculated fluid δ18O and δ2H values from clay minerals and quartz cannot be explained by a simple water-rock interaction or a simple fluid mixing model, since variable isotopic exchange temperature and endmembers have to be considered. This suggests that both water-rock interaction and mixing of fluids occurred between dynamically variable end members during mineralization. The average estimated formation temperature of chlorites in the Sanjin deposit using chlorite geothermometry is 233 ± 19 °C, in agreement with the highest temperature zone in Hishikari, estimated by homogenization temperature of fluid inclusions of ore veins. In addition, the estimated formation temperatures of chlorite in epidote- and/or prehnite-rich altered rocks are higher (avg. 240 ± 17 °C) than those in epidote- and/or prehnite-poor altered rocks (avg. 216 ± 9 °C). Thus, the chlorite-epidote/prehnite assemblage can be an index of a high temperature alteration zone in the Sanjin deposit. Considering the position of the paleo-water table of the three ore zones, these factors are consistent with the formation of the Sanjin deposit proximal to the upflow zone responsible for gold mineralization at Hishikari. We suggest that our approach could be utilized to understand the thermal structure of epithermal gold system, which may be important to explore for blind veins at mature mining districts. • Interstratified clay minerals with very low expandability are dominant at Sanjin. • Distinctive occurrence of epidote and prehnite, previously unreported at Hishikari • Chlorite coexisting with epidote/prehnite has the highest formation temperature. • O and H isotopes suggest water-rock interaction and mixing of variable end members. [ABSTRACT FROM AUTHOR]

It is difficult to directly investigate the chemical state of Pt in marine ferromanganese crusts (a mixture of hydrous iron(III) oxide and manganese dioxide (δ-MnO)) because it is present at extremely low concentration levels. This paper attempts to elucidate the mechanism by which Pt is concentrated into marine ferromanganese crust from the Earth's continental crust through ocean water. In this investigation, the sorption behavior of the Pt(II) complex ions on the surface of the δ-MnO that is a host of Pt was examined as a model reaction. The δ-MnO sorbing Pt was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) to determine the chemical state of the Pt. Hydrolytic Pt(II) complex ions were specifically sorbed above pH 6 by the formation of a Mn-O-Pt bond. XPS spectra and XANES spectra for δ-MnO sorbing Pt showed that the sorbed Pt(II) was oxidized to Pt(IV) on δ-MnO. The extended X-ray absorption fine structure (EXAFS) analysis showed that the coordination structure of Pt sorbed on δ-MnO is almost the same as that of the [Pt(OH)] complex ion used as a standard. Therefore, the mechanism for the concentration of Pt in marine ferromanganese crust may be an oxidative substitution (penetration of Pt(IV) into structure of δ-MnO) by a reduction-oxidation reaction between Pt(II) in [PtCl(OH)] and Mn(IV) in δ-MnO through a Mn-O-Pt bond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diverse W metallogeny of the Baiyunxian ore field intensively occurred in 156–153 Ma. • W metallogeny was associated with Late Jurassic highly evolved magmatic phases. • Metal element are derived from remelting of metasedimentary crustal basement. • Lithology of wall rocks is the major cause of varied W mineralization types. The Baiyunxian ore field, a large tungsten ore filed in the Nanling Metallogenic Belt of South China, hosts a variety of tungsten deposits such as the Dapu (quartz wolframite vein type), Chashanjiao (skarn type), Toutianmen (greisen type), and Dashan (quartz scheelite vein type). However, precise mineralization ages of these deposits remain poorly constrained and this has long vexed a better understanding of genetic relationships between diverse W mineralization types and the spatially associated Jiufeng granitic complexes. Here, we report firsthand zircon U–Pb, monazite U–Pb, garnet U–Pb, cassiterite U–Pb, and molybdenite Re–Os ages of different granites and ores from the Baiyunxian ore field. The Jiufeng granitic complexes consists of phase Ⅰ biotite granite (P1), phase Ⅱ two-mica granite (P2), and phase Ⅲ granitic dikes (P3, including greisen W ore). Zircons from P1 granite define a concordant U–Pb age of 166.0 ± 0.9 Ma (MSWD = 1.1). Monazites from P2 granite yielded a Tera–Wasserburg lower intercept age of 159.2 ± 0.7 Ma (MSWD = 0.45). In addition, zircons and monazites from P3 granite in the Toutianmen deposit yield a concordant U–Pb age of 154.7 ± 1.3 Ma (MSWD = 1.3) and a Tera–Wasserburg lower intercept age of 156.6 ± 1.9 Ma (MSWD = 0.14), respectively, suggestive of multi-stage emplacement processes of the Jiufeng complexes. Ten molybdenite samples from the Dapu deposit generate an isochron age of 156.0 ± 3.0 Ma (MSWD = 0.93). In situ garnet and cassiterite LA-ICP-MS U–Pb dating results of the Chashanjiao skarn deposit yield lower Tera–Wasserburg intercept ages of 155.3 ± 1.2 Ma (MSWD = 1.6) and 153.4 ± 3.7 Ma (MSWD = 1.3), respectively. These dating results indicate that different W mineralization events in the Baiyunxian ore field intensively occurred in the Late Jurassic (∼159–153 Ma). Despite a close spatial relationship between various W orebodies and P1 granite, the geochronological results demonstrate that extensive W metallogeny in the Baiyunxian ore filed likely occurred later than P1 granite and contemporaneous with P2–3 granites. In addition, scheelites from the four deposits have similar REE patterns that are characterized by weak MREE enrichment, despite few exceptions being found in scheelites from the Dashan and Chashanjiao deposits. This suggests that the diverse W metallogeny in the Baiyunxian ore field were derived from the same magmatic hydrothermal system and changed as the ore-forming fluid evolved. Multidisciplinary evidence indicates that the Late Jurassic highly evolved P2–3 granites of the Jiufeng complexes were crucial to W mineralization in the Baiyunxian ore field and the lithology of wall rocks exerted first-order control of W mineralization types. [ABSTRACT FROM AUTHOR]

Highlights: [•] A1 and A2 type granites in the Huangshaping deposit have been distinguished. [•] Genesis of the magmas is related to partial melting and fractional crystallization. [•] Extremely high δ 18O values and disequilibrium 18O/16O fractionations are reported. [•] Pb isotopic variations indicate different magma sources for the granites. [•] Relations between granite evolution and metallogenic series have been established. [ABSTRACT FROM AUTHOR]

Abstract: The Huangshaping polymetallic deposit is a large-scale deposit located in the central Nanling region, South China. Different types of mineralization have been classified in the area, which are attributed to three types of granitoids from the composite granitic pluton: quartz porphyry, granophyre and granite porphyry. In order to study the magmatic genesis and evolutionary process, as well as constrain the crystallization and mineralization events, 100 zircon separates from different intrusive stages of the pluton have been analyzed for trace element contents and U–Pb isotopic concentrations. The results show that zircons from the Huangshaping granitoids are enriched in Th, U, Hf, Ti, REE and other trace elements, indicating hydrothermal fluid alteration and transformation. Additionally, there is a large variation between different types of granitoids in terms of trace element concentrations. Compared to the zircons from the quartz porphyry and the granophyre, zircons from the granite porphyry are more enriched in Th, U, Hf, Ti, and P but strongly depleted in Eu. This suggests that the magma that formed the granite porphyry possessed higher temperatures, possibly experienced stronger crystal fractionation and originated from a more evolved, complex magmatic source region with higher degree of crustal maturity. Combined with characteristics of crystal morphology and internal texture, hydrothermal zircons were distinguished from magmatic zircons in each granitoid to reveal mineralization processes. The U–Pb geochronology results show that there are two major stages of mineralization: ~190Ma weak Cu (Pb, Zn) mineralization related to the quartz porphyry and the granophyre, and ~155Ma strong W, Sn (Mo, Pb, Zn) mineralization associated with the granite porphyry. Compositions of these hydrothermal zircons suggest that the earlier stage mineralization could be close to single, relatively cold, reduced and quickly ascended fluids, whereas the later stage might be related to hot, oxidized, strongly fractionated and highly evolved, mixed fluids. This study also indicates that hydrothermal zircons from typical composite granitic plutons could be a good tool to reveal the multi-stage magmatic and mineralization process in middle to late Jurassic South China. [Copyright &y& Elsevier]

Abstract: In order to develop a chemical technique for the recovery of gold (Au) and platinum (Pt) in the metallic state from spent catalysts, e.g., catalysts for environmental protection and automobile and petroleum catalysts, the coprecipitation behaviors of Au(III) and Pt(IV) complex ions with Fe(OH)2 as a scavenging and reducing agent were investigated. The Au(III) complex ions were found to be stoichiometrically and rapidly reduced to metallic Au due to electron transfer in acidic aqueous solution prior to coprecipitation with Fe(OH)2. Conversely, Pt(IV) complex ions were reduced only after coprecipitation with Fe(OH)2 due to electron transfer through a Pt(IV)–O–Fe(II) bond on the solid Fe(OH)2. Using this chemical technique, Au and Pt can be selectively and effectively recovered in the metallic state. [Copyright &y& Elsevier]

Little is known about the nature of ore fluid at the Sopokomil shale-hosted massive sulfide Zn-Pb deposit (North Sumatra, Indonesia). We therefore investigated its ore-fluid salinities, temperatures, densities, redox state, and pH using fluid inclusion microthermometry, sphalerite composition, and thermodynamic modelling. The fluid salinities and temperatures were ≈6 wt.% NaCl equiv and ≈165 °C, respectively, corresponding to an ore fluid less dense than seawater (≈0.96 g/mL). Sphalerite contains ≈9.9 mole% FeS in the stratiform ore and ≈3.4 mole% FeS in the feeder ore, suggesting a reduced fluid, which must have been acidic to be fertile. Such redox state and acidity invoke fluid dilution as the sulfide depositional mechanism. The bulk of the sulfides were precipitated in the early stage of mixing, within T = 165–155 °C. Key ingredients of sphalerite and galena at Sopokomil include (1) Zn that was primarily transported as ZnCl+, (2) Pb that predominantly occurred as PbCl2(aq), and (3) S that was largely supplied by marine sediment porewater. This study highlights the significance of a dramatic shift in thermal and chemical equilibrium induced by fluid dilution in the making of the first significant shale-hosted massive sulfide Zn-Pb deposit in Indonesia. [ABSTRACT FROM AUTHOR]

Seafloor massive sulphide (SMS) deposits, modern analogues of volcanogenic massive sulphide (VMS) deposits on land, represent future resources of base and precious metals. Studies of VMS deposits have proposed two emplacement mechanisms for SMS deposits: exhalative deposition on the seafloor and mineral and void space replacement beneath the seafloor. The details of the latter mechanism are poorly characterised in detail, despite its potentially significant role in global metal cycling throughout Earth's history, because in-situ studies require costly drilling campaigns to sample SMS deposits. Here, we interpret petrographic, geochemical and geophysical data from drill holes in a modern SMS deposit and demonstrate that it formed via subseafloor replacement of pumice. Samples from the sulphide body and overlying sediment at the Hakurei Site, Izena Hole, middle Okinawa Trough indicate that sulphides initially formed as aggregates of framboidal pyrite and matured into colloform and euhedral pyrite, which were replaced by chalcopyrite, sphalerite and galena. The initial framboidal pyrite is closely associated with altered material derived from pumice, and alternating layers of pumiceous and hemipelagic sediments functioned as a factory of sulphide mineralisation. We infer that anhydrite-rich layers within the hemipelagic sediment forced hydrothermal fluids to flow laterally, controlling precipitation of a sulphide body extending hundreds of meters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition from barren to fertile geochemical signatures of arc magmas in the Baguio-Mankayan Mineral District is intimately linked with arc development and subduction dynamics. • Late Eocene barren magmas were generated in a thin nascent Luzon arc. • Middle Pliocene fertile magmas were formed from mixing of mafic and silicic melts associated with ridge subduction. • More hydrous conditions of Early Pleistocene fertile magmas are attributed to progressive crustal thickening and compression induced by ride subduction. The Baguio-Mankayan Mineral District (BMMD) in Northern Luzon, Philippines, is renowned for its world-class auriferous porphyry-Cu and epithermal deposits, which are associated with arc magmatism during the Pliocene-Pleistocene. One of the less studied areas in this region is in southern Mankayan, where the Suyoc epithermal prospect is located. New U-Pb zircon ages, combined with whole-rock and in-situ geochemical analyses of igneous rocks in the Suyoc area, revealed a shift from barren to fertile magmatic episodes in the BMMD. 1) Late Eocene (36.93–37.20 Ma) barren magmas generated in a thin, nascent Luzon arc, 2) Fertile Middle Pliocene (2.87–3.4 Ma) magmatism attributed to the mixing of primitive mafic and silicic crustal melts due to ridge subduction, and 3) Early Pleistocene (1.73 Ma) fertile magmatism associated with more hydrous melts due to progressive crustal thickening. The Late Eocene barren magmatism enhanced both source and intra-crustal conditions for the onset of younger fertile magmatic events via sub-arc modification and crustal addition/thickening. Furthermore, we consider the fertile Pliocene and Pleistocene magmatism in the BMMD as two separate events with different petrogenesis. Mafic-silicic interaction in the Pliocene was documented through core-rim analysis of amphiboles from the Pliocene Suyoc Diorite. On the other hand, the Pleistocene fertile magmatism, represented by the Bato Dacite Porphyry, showed geochemical signatures consistent with a thickened crust and also reflected higher magmatic H 2 O contents ranging from 6.3 to 7.8 wt%. [ABSTRACT FROM AUTHOR]

• Mineralization in MFC at Tubane section exclusively occurs in ultramafic cumulates. • Base metal sulfides are hosted by feldspathic orthopyroxenites. • PGE are hosted by platinum group minerals (PGM), commonly Pt-Pd-Bi-Te. • 79% of PGM are hosted by altered silicates, and 19% by base metal sulfides. • Geochemistry and sulfur isotopes evoke contamination of magmas prior to emplacement. • Sulfides may remain undiscovered in the feeder zones of MFC. The Molopo Farms Complex (MFC) is located near the western margin of the Archean Kaapvaal Craton, in southern Botswana. The complex hosts low grade disseminated Ni-Cu and platinum group elements (PGE) mineralization restricted to the lower ultramafic cumulates, notably in the feldspathic orthopyroxenites. The mineralized feldspathic orthopyroxenites contain up to 0.47 ppm Pt + Pd + Au manifested in the form of platinum group mineral (PGM) assemblages dominated by PGE bismuthotellurides, asernides and minor Au and Ag alloys. The PGM encountered are froodite (PdBi 2), moncheite (PtTe 2), michenerite (PdBiTe), sperrylite (PtAs 2) largely associated with altered silicates and sulfide minerals. The association of PGM with sulfides suggests that they were originally concentrated by sulfide melt, while late stage reaction of sulfides with hydrothermal fluids resulted in the observed spatial proximity of PGM with altered silicates. The Cu/Pd ratios of most of the rocks fall within the primitive mantle range. However, the Cu/Pd ratios of the feldspathic orthopyroxenites are more variable, with few samples falling above and below the primitive mantle range suggesting the prior sulfide extraction from the magmas and the presence of cumulus sulfides. This is supported by the Cu/Zr ratios of these rocks which are also variable above and below unity. Trace element ratios on the (Th/Yb) PM versus (Nb/Th) PM plot indicate strong crustal contamination across all units including those not in proximity to the country rocks. The δ34S of the magmatic rocks are variable between −6.3‰ and −11.4‰. In contrast, the δ34S of dolomitic siltstones of the Transvaal Supergroup which constitute the immediate country rocks vary from −4.1‰ to +0.6‰. These data indicate that crustal contamination largely occurred prior to magma emplacement. It is inferred that the most important contaminant and source of crustal S were the Ramotswa and Ditlhojana Formations that include sulfidic shales at depth. We consider that magnesian basaltic magmas of B1 Bushveld magma composition underwent crustal contamination, assimilation of crustal S and segregation of sulfide melt in the feeder conduit or staging-chamber prior to final magma emplacement. The feeder conduit or staging-chamber was subsequently invaded by further B1 magma. This magma entrained some of the sulfides lodged in the plumbing system and flushed them to the final MFC chamber studied here. After the staging-chamber had already partially solidified, it was invaded by yet another influx of magma, possibly even more primitive than the B1 Bushveld magma. Being a crystal mush, this magma assimilated and entrained some of the previously formed orthopyroxenites manifested by fragments of orthopyroxenite in the harzburgites of the final MFC chamber. The presence of centimeter-sized globular sulfides and fragments of orthopyroxenite within harzburgites suggests that the complex was emplaced as separate pulses of magmas. Therefore, it is considered that sulfide accumulations may remain undiscovered in the feeder zones or the staging-chamber. [ABSTRACT FROM AUTHOR]

• Three generations of pyrite (py 1 , py 2 , and py 3) have been differentiated. • Ore-forming fluid flowed from SE to NW. • Hydrothermal sulfur contributes to mineralization in the feeder zone. • Bacterial sulfate reduction is responsible for the bulk of mineralization. The Dairi Zn + Pb + Ag deposit is the only giant SEDEX deposit that has been discovered to date in Sumatra. Ore-gangue mineralogy and sulfur isotope studies have been carried out to elucidate the paragenetic sequence, deformation of ore, flow direction of ore forming fluid, and sources of sulfur in the Dairi deposit. Stratiform orebodies hosted by the Julu unit (interbedded dolomitic siltstone and carbonaceous shale; multilayers; accounting for greater than 90% of metal resources) consist of pyrite-rich massive, sphalerite-rich massive, bedded sulfide, galena-rich breccias, and vein ore types, whereas discordant orebodies hosted by the Jehe unit (massive and brecciated arenaceous dolostone) comprise vein and disseminated ore types. Fine-grained, subhedral-euhedral and framboidal pyrite (enriched in Co, Ni, Cu, As, Bi, Ag relative to hydrothermal pyrite) were precipitated in the diagenetic stage, followed by precipitation of pyrite (enriched in Zn, Pb, Mn, Tl relative to diagenetic pyrite), sphalerite, galena, chalcopyrite, pyrrhotite, acanthite, tetrahedrite, tennantite, pyrargyrite, boulangerite, freieslebenite, and diaphorite in the hydrothermal stage derived from the exhaled ore-forming fluid. Metamorphic pyrite (enriched in Co and depleted in Cu, Zn, Mn, Tl, Ag relative to the other pyrites) formed from pyrrhotite (depleted in Co relative to metamorphic pyrite) and soft sulfides were remobilized into pyrite fractures and veins during sub-greenschist metamorphism. Ore-forming fluid ascended through fractures in the Jehe unit (forming the discontinuous orebodies) and then it discharged and flowed from SE to NW on the seafloor (forming the stratiform orebodies). Reduced sulfur for diagenetic pyrite (δ 34S = -4.1‰ to + 11.6‰) was supplied by bacteriogenic reduction of Carboniferous seawater sulfate. Hydrothermal sulfur was considered as the source of sulfur for the Jehe-hosted orebodies (δ 34S = +3.5‰ to + 8.0‰). The heavier δ34S of sulfides in the Julu-hosted orebodies (δ 34S = +6.4‰ to + 28.8‰) suggests large-scale bacteriogenic reduction of Carboniferous seawater sulfate in a restricted, anoxic basin. A bacteriogenic reduced sulfur reservoir, rather than hydrothermal sulfur, may be more plausible to account for the scale of the giant Dairi deposit. [ABSTRACT FROM AUTHOR]

Cassiterite (SnO 2) precipitates over a wide physicochemical range during magmatic-hydrothermal processes. Significant variations in chemical and Sn isotopic compositions of cassiterite have been increasingly reported from hydrothermal deposits worldwide. However, the mechanisms responsible for such notable changes in cassiterite geochemistry remain to be fully addressed. Toward this end, we investigated the chemical and Sn isotopic compositions of distinct generations of cassiterite from a highly-evolved magmatic-hydrothermal-metallogenic system (Xianghualing Sn polymetallic deposit, South China). Cassiterite is widespread in the albite granite, greisen, skarn, and sulfide ore of this deposit, covering most of the known cassiterite-bearing rock/ore types. Based on distinct morphologies and mineral paragenesis, three generations of the Xianghualing cassiterite are identified: (1) Cst 1 occurs in albite granite and greisen; (2) Cst 2 occurs in skarn; and (3) Cst 3 is present in sulfide ore. A lattice strain model indicates that inter-element compositional differences of cassiterite are dual-controlled by cassiterite element partition coefficients and melt/fluid compositions for sufficient and deficient elements, respectively. The variations in Zr, Hf, Nb, and Ta elements in cassiterite are recognized as thermo-indicators of the melt/fluid physicochemical conditions. Their concentrations are influenced by pre- and syn-precipitated Zr-Hf-Nb-Ta-enriched minerals that have a wide crystallization temperature range. Due to differentiations of multiple cationic valences, concentrations and interelement ratios of Sb, Fe, V, and U can be utilized to monitor the relative melt/fluid redox state of different cassiterite generations. Tin stable isotopic compositions are notably fractionated in the Xianghualing cassiterite samples, with δ amu Sn values relative to standard NIST 3161a ranging from − 0.16 ‰ to 0.19‰. By comparison with compiled Sn isotopes of other hydrothermal deposits, kinetic disequilibrium fractionation is proposed as the main control on cassiterite Sn isotopes fractionation. A Rayleigh fractionation model generates fractionation factors of 1.00010–1.00025, consistent with fractionation factors predicted by first principles calculations (1.00013 to 1.00037). Thus, progressive precipitation of Sn-enriched minerals due to the change of physicochemical conditions during magmatic-hydrothermal processes will cause lighter Sn isotopic compositions in residual melt/fluid. This study highlights that cassiterite chemical and Sn stable isotopes are novel indicators to magmatic-hydrothermal processes. • A mathematic method is proposed to normalize varied expressions of Sn isotopic data. • Lattice strain model predicts inter-elemental compositional differences of cassiterite. • Cassiterite chemical compositions could trace physicochemical conditions of melt/fluid. • Cassiterite Sn isotope fractionation mainly caused by kinetic disequilibrium fractionation. [ABSTRACT FROM AUTHOR]

Highlights • Silica nanoparticle growth in geothermal brine is examined during the polymerization of silicic acid by observation with dynamic light scattering at the Sumikawa geothermal station. • Three types of geothermal brines, raw (pH 6.6), pH adjusted (pH 8), and diluted brines were examined. • The monosilicic acid concentration rapidly decreased over time in the raw brine but was almost constant in the samples with lower silicic acid concentrations. • The polysilicic acid particle diameters in the raw brine increased from 1 to 6 nm within 5 min and then was almost constant at 7 nm for the subsequent 30 min. Abstract Silica nanoparticle growth in geothermal brine was examined during the polymerization of silicic acid by observation with dynamic light scattering (DLS) at the Sumikawa geothermal station, examining raw (pH 6.6), pH adjusted (pH 8), and diluted brines (100 to 60%). The monosilicic acid concentration rapidly decreased over time in the raw brine but was almost constant in the samples with lower silicic acid concentrations. The average polysilicic acid particle diameter in the raw brine rapidly increased, from 1 to 6 nm, within 5 min (stage I) and then was almost constant at 7 nm for the subsequent 30 min (stage II). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Description of peripheral epithermal deposit inthe Nansatsu District, Southern Japan. • Geochemical and stable isotopic measurements, constraining fluid conditions. • Ar/Ar dating reveals close temporal relationship between differing mineralisations. • Comparison to the wider southern Kyushu epithermal depositional setting. Abstract The Kago deposit is a small deposit located at the southern tip of the Satsuma Peninsula of Southern Kyushu, Japan. It lies proximal to the well-known Nansatsu-type mineralisation province dominated by high-sulfidation type epithermal deposits. The deposit was heavily mined in the 18 th Century, largely for its relatively higher gold compared to that of surrounding and regional deposits. The Kago deposit is a typical low-sulfidation deposit, characterised by adularia-quartz veins, composed of electrum, Ag-tetrahedrite, polybasite, chalcopyrite and pyrite. Based on mine records, the grade ranged from 4.1 to 13.3 g/t Au and 2.6–6.6 g/t Ag. Alteration grades from low to high temperature argillic into a propylitic zone at the extremes of the vein exposures. Carbonate is absent. Fluid inclusion microthermometry reveals a typical temperature range of 220–240 °C with salinity of 0.7–2.6 NaCl eq. wt%. Electrum from high-grade ore ranges from 66 to 69 wt% Au. 40Ar/39Ar age dating of adularia bearing colloform/crustiform and brecciated veins, suggests a mineralisation event from 4.23 to 4.0 Ma. δ18O of veined and silicified quartz ranges from +4.0 to +18.4‰. δ18OH 2 O of fluids in equilibrium with quartz, in the dominant range of measured fluid inclusion temperatures, ranges from −6.5‰ to −0.2‰. δ34S of pyrite has a narrow range from −1.8 to 2.7‰. The deposit lies at the northern extent of the classic Nansatsu high-sulfidation epithermal area, in which a number of silicified bodies punctuate the region in a roughly semi-circular shape. The Kago deposit lies within the principle mineralisation age range of the high-sulfidation deposits, which range from 5.5 to 3.7 Ma. The structural displacement of the Kago deposit from the Nansatsu mineralisation and the differing host rocks has greatly influenced alteration, ore and rock-water interaction of the ore depositing fluids. Here we seek to establish the relationship that this extended mineral province has between the differing styles of mineralisation. [ABSTRACT FROM AUTHOR]

Auriferous quartz veins in the Namicupo gold prospect occur parallel to the foliation of metasedimentary host rocks of the Xixano Complex in northeastern Mozambique. The geochemistry and ore-forming mechanism of the Namicupo prospect have never been scientifically investigated. This study discusses the ore mineralogy, fluid inclusion, and stable isotope (S-O) characteristics of the prospect. The mineralization in the Namicupo prospect is divided into two stages. The Stage I, primary mineralization, is represented by electrum with Ag contents of 15–26 at.%, associated with pyrite and chalcopyrite. The Stage II is supergene mineralization, characterized by electrum with Ag contents of 39–46 at.%, intergrown with goethite, barite, and minium, which replaced primary sulfides. Quartz from the mineralized veins hosts three types of primary fluid inclusions coexisting in the same fluid inclusion assemblage. Type A inclusions are three-phase aqueous‑carbonic inclusions (aqueous liquid, CO 2 liquid and vapor), with final homogenization temperature and salinity varying from 140 to 241 °C, and 1.0 to 7.8 wt% NaCl eq., respectively. Type B inclusions occur either as mono-phase (vapor or liquid) or two-phase (vapor and liquid) CO 2 -rich, N 2 -H 2 O-bearing inclusions, with homogenization temperature varying from +12.9 to +29.3 °C. The Type C inclusions are two-phase (liquid and vapor) aqueous inclusions, which homogenize to liquid phase at temperatures between 209 and 337 °C. The salinity of the Type C inclusions varies from 4.0 to 10.8 wt% NaCl eq. The sulfur isotopic ratios (δ34S CDT) of sulfides associated with Stage I mineralization and the oxygen isotopic ratios (δ18O SMOW) of water calculated from those of quartz from the quartz veins vary from −3.5 to +0.9 ‰ and −1.0 to +2.5 ‰, respectively. The primary mineralization at the prospect is classified as an orogenic-type gold mineralization, formed by aqueous‑carbonic metamorphic fluids. The precipitation of primary gold mineralization in the Namicupo prospect resulted dominantly from fluid immiscibility. The considerable amount of S up to 0.1 wt% and the high Ag contents of electrum intergrown with goethite, minium and barite suggest that the supergene mineralization in the Stage II was caused by oxidation of primary gold-bearing sulfides and Au-rich electrum under moderately acidic and oxidizing conditions, which resulted in Au and Ag liberation, likely by thiosulfate. Dissolution of primary mineralization and supergene gold enrichment in the Namicupo prospect appear to have occurred largely in situ, with little evidence of distant mobilization. • The Namicupo prospect consists of primary and supergene gold mineralization. • The primary mineralization is classified as an orogenic-type gold. • The primary mineralization was formed by aqueous‑carbonic metamorphic fluids. • Supergene enrichment consisted of the mobilization of primary ores by thiosulfate. [ABSTRACT FROM AUTHOR]

Whether the magma storage system is responsible for the formation of the 74 ka Youngest Toba Tuff (YTT) is still debatable. It is currently believed that the YTT super-eruption was formed either by a single voluminous chamber or by multiple magma chambers. This paper presents a detailed component analysis of eruption products, comprehensive stratigraphy, mineralogy, and geochemistry of phenocrysts and matrix glass to shed light on the issue. Based on the componentry, mineral assemblages, mineral and glass compositions, and vesicle texture, we identified four distinct pumice types: YtA–YtD. Of these, YtA is an amphibole-bearing pumice containing an average of 77.1 wt% SiO 2. This type of pumice is characterized by abundant matrix vesicles, with plagioclase showing a wide range of anorthite content (An 20 –An 90) and disequilibrium texture. The YtB and YtC types are the most evolved pumices, with 77.5 and 77.6 wt% SiO 2 , respectively. The plagioclase of these pumices commonly has an unzoned texture with low anorthite content (~An 30). The YtB pumice is biotite-bearing, distinctively characterized by abundant pheno-vesicles; while the YtC pumice includes rare pheno-vesicles, skeletal-polyhedral quartz, and no biotite. The YtD type is a quartz- and sanidine-free pumice, with a less-evolved glass composition (76.3 wt% SiO 2), and is characterized by dominant matrix-vesicles and crystal clots of plagioclase, amphibole, pyroxene, and biotite. The plagioclase of the YtD pumice shows a hollow texture and high anorthite content (~An 50). In situ trace element analysis for the matrix glass of YtA, YtB, YtC, and YtD showed very distinct geochemical signatures, which correlated with the four pumice types. Bivariate plots (Ba vs. Y, Sr vs. Y, and Ba vs. Sr) showed that YtA pumice is characterized by medium Ba (400–875 ppm) and Sr (41–67 ppm), and variable Y (20–53 ppm) content. YtB and YtC pumices are characterized by low Ba (8–136 ppm) and Sr (13–37 ppm), and highly variable Y (27–77 ppm) content. YtD pumice is characterized by high Ba (1173–1340 ppm) and Sr (95–124 ppm), but a narrow range of Y (21–31 ppm) content. The trace-element geochemical signatures, occurrence and absence of certain minerals (i.e., biotite and quartz), and vesicle type from the distinct pumice type, suggest the presence of four distinct magma bodies before the eruptions, namely YtA, YtB, YtC, and YtD. The number of distinct glass shards and pumices with the same geochemical signatures represents the volume fraction of each magma type. The approximate total volume of the magma (5300 DRE km3) and the geographical distributions of each pumice type demonstrated that the voluminous YtA (3406 km3), medium YtB (1354 km3), and smallest YtD (168.5 km3) chambers in the northern direction, and the small YtC chamber (371.5 km3) in the southern caldera, were evacuated during the 74 ka YTT eruption. Eruptions from multiple magma chambers were initiated by a high supersaturation of pheno-vesicle-rich magma (YtB magma), triggering the subsequent eruptions of the YtA, YtB, YtC, and YtD magmas. • The first detailed studies on the 74 ka Youngest Toba Tuff (YTT) eruption products for juvenile and non-juvenile materials. • The classification of pumice types by the human eye correlates with different internal structures and geochemical signatures. • There were at least four pre-eruptive magma chambers prior to the 74 ka YTT super-eruption, namely YtA, YtB, YtC, and YtD. • Eruptions from YTT multiple magma chambers were initiated by a high supersaturation of pheno-vesicle-rich magma (YtB magma). [ABSTRACT FROM AUTHOR]

The intermediate to low sulfidation epithermal gold deposit in Masara, Compostela Valley, Eastern Mindanao, Philippines, is associated with a diorite porphyry from the Late Miocene Lamingag Intrusive Complex. Detailed mineralogical investigation of the host rocks in the deposit reveals five major alteration zones and at least two mineralizing events. A potassic alteration zone characterized by stockwork magnetite veins, secondary biotite and magnetite and an early-stage chlorite-sericite alteration composed of quartz + chlorite + illite + sericite + pyrite ± biotite ± magnetite ± calcite assemblages are interpreted to be linked with an earlier porphyry copper system in the area. These were overprinted by late-stage chlorite-sericite alteration consisting of quartz + chlorite + illite + sericite + pyrite ± adularia ± magnetite ± epidote and sericite assemblages which generally contain quartz + illite + sericite + pyrite. These alteration overprints are inferred to be related to a younger low to intermediate-sulfidation epithermal gold mineralization which involved near-neutral fluids. Advanced argillic alteration comprising quartz + kaolinite + magnetite + dickite ± illite ± calcite was also observed in the area. Isocon analysis shows that alteration zones associated with epithermal mineralization are generally characterized by enrichment in SiO 2 and K 2 O and depletion of CaO and Na 2 O as well as additions of Au, Cu, Zn and Pb. Pearce Element Ratio (PER) analysis indicates high degrees of sericitization in the altered diorite porphyry, tuff and quartz diorite units. At least three major alteration centers are defined based on the spatial distribution of the Alteration Index of surface samples calculated from the PER analysis. The results of this study support the use of whole-rock geochemistry as a complement to traditional techniques in exploration geochemistry. [ABSTRACT FROM AUTHOR]

The article focuses on the muti-stage mineralization of the Early Yanshanian granites found in Nanling region of South China in light of conclusions derived from the geochemical characteristics of rare-earth elements. Topics discussed include division of granite composite in Nanling region, formation of Type III granite composites through different intrusive stages with Europium negative anomaly and association of lead, zinc and copper mineralization with Type I granitoid composites.

Late Cenozoic granitoids are widespread in a 1600 km long belt forming the Western and Northern Sulawesi tectono-magmatic provinces. They can be divided into three rock series: shoshonitic (HK), high-K felsic calc-alkaline (CAK), and normal calc-alkaline to tholeiitic (CA-TH). Representative samples collected from eleven plutons, which were subjected to petrography, major element, trace element, Sr, Nd, Pb isotope and whole-rock δ 18 O analyses, are all I-type and metaluminous to weakly peraluminous. The occurrence of the two K-rich series is restricted to Western Sulawesi, where they formed in an extensional, post-subduction tectonic setting with astenospheric upwelling providing thermal perturbation and adiabatic decompression. Two parental magma sources are proposed: enriched mantle or lower crustal equivalent for HK magmas, and Triassic igneous rocks in a Gondwana-derived fragment thrust beneath the cental and northern parts of Western Sulawesi for CAK magmas. The latter interpretation is based on striking similarities in radiogenic isotope and trace element signatures. CA-TH granitoids are found mostly in Northern Sulawesi. Partial melting of lower-middle crust amphibolites in an active subduction environment is the proposed origin of these rocks. Fractional crystallization and crustal contamination have played a significant role in magma petrogenesis, particularly in the case of the HK and CAK series. Contamination by organic carbon-bearing sedimentary rocks of the HK and CAK granitoids in the central part of Western Sulawesi is suggested by their ilmenite-series (reduced) character. The CAK granitoids further to the north and CA-TH granitoids in Northern Sulawesi are typical magnetite-series (oxidized). This may explain differences in mineralization styles in the two regions. [ABSTRACT FROM AUTHOR]

Demands for "green" additives that control the crystal growth and inhibit the scale formation in industrial processes are growing as never before. Nanobubbles can be the green additive for inhibiting and/or promoting the crystal growth of calcium carbonate, given their well-known unique physicochemical properties. This paper reports for the first time the changes in the crystal growth rate of calcite in liquid in the presence of air nanobubbles. We injected the air nanobubbles into the solution and studied the calcite crystal growth for the first 4 h in a static condition at 20 °C and 88 °C. We found that air nanobubbles retarded the growth rate of calcite crystal by up to 53 % and 33 % at 20 °C and 88 °C, respectively. The retardation of calcite crystal growth could differ with different number densities of air nanobubbles added to the solution. A higher number density of nanobubbles generally showed slightly greater retardation throughout the tested 4 h. Air nanobubbles may influence the crystal growth either by changing solid-liquid interfacial tension on the crystal surface, reducing the free growth sites, adsorbing Ca2+ ions, playing roles in bubble mattress and thermal buffering on the crystal surface, or combinations of them. Our findings suggest that air nanobubbles can be utilized as a green inhibitor of calcite crystal growth and calcium carbonate scale in broad industrial areas. Calcite crystal growth was retarded in the presence of air nanobubbles at 20 °C and 88 °C. [Display omitted] • Calcite crystal growth was retarded by adding air nanobubbles at 20 °C and 88 °C. • The retardation efficiencies of crystal growth were up to 53 % (20 °C) and 33 % (88 °C). • Nanobubbles influence the crystal-liquid interface and the substrate surface. • Air nanobubbles can be a "green" and inexpensive inhibitor for CaCO 3 crystal growth. [ABSTRACT FROM AUTHOR]

We analyzed new radiometric dating and petrological data of DVC in an attempt to reconstruct volcanic history as groundwork to understand magmatic temporal and spatial evolution. The magma of DVC can be divided on the basis of mineral composition into three types: olivine bearing basalt–basaltic andesite, pyroxene basaltic andesite–andesite, and biotite andesite–dacite, which coincide with three volcanic episodes of DVC: pre-caldera, second, and youngest episode, respectively. The pre-caldera episode was active no later than 1 Ma, the second episode occurred between 0.3 and 0.4 Ma, and the youngest occurred after 0.27 Ma. Plots of CaO, K 2 O, Al 2 O 3 , and Rb/Sr against FeO*/MgO and/or MgO suggest that each volcanic episode has distinct differentiation trends, indicating the presence of multiple shallow magma chambers. The close spatial relationship between the geothermal manifestation, geophysical anomalies, geothermal production zones and volcanic edifices supports the presence of multiple shallow magma chambers beneath DVC, which act as a heat source for the existing geothermal system. [ABSTRACT FROM AUTHOR]

• Two types of field tests (batch- and circulation-tests) were conducted at the yamagawa power plant by adding cationic flocculant and quicklime to suppress silica scale deposition. • The reagents were mixed with the brine after a delay of zero minutes (no retention time; NRT) or 15–60 min (retention time for 15–60 min; 15 RT to 60 RT) at 90 °C. • The silicic acid concentration decreased to 300 mg/L as retention time increased, regardless of the reagent concentration when we added a cationic flocculant. • Silica recovery rates increased with the amount of CaO added. • Addition of CaO is the best option for silica recovery from geothermal brine at the yamagawa power plant. To suppress silica scale deposition from supersaturated silica, two types of field tests, i.e., batch- and circulation-tests were conducted at the Yamagawa Power Plant by adding cationic flocculant and quicklime. In the flow test, an improved seed circulation system was used and the flow rate of brine to be treated was about 1.2 tons/hour. The silicic acid concentration in the brine after steam–brine separation under atmospheric pressure was 630 mg/L. In the batch test, the reagent was mixed with the brine after a delay of zero minutes (no retention time; NRT) or 15–60 min (retention time for 15–60 min; 15 RT to 60 RT) at 90 °C. When a cationic flocculant (DADMAC No.6) was added at concentrations ranging from 10 to 50 mg/L, the silicic acid concentration decreased to 300 mg/L with increasing retention time, regardless of the reagent concentration. In contrast, in the case of CaO addition, silica recovery rates increased with the amount of CaO added. The silicic acid concentration decreased to approximately 50 mg/L at NRT when 1 g/L CaO was added. In the flow test, DADMAC No. 6 or CaO was added continuously under various conditions. The silicic acid concentration in the treated brine was reduced to approximately 400 mg/L when DADMAC No. 6 was used. The turbidity of the treated brine was more than 10 NTU. It needs to be reduced to less than 1 NTU for underground reinjection. In contrast, the silicic acid concentration was approximately 100 mg/L when CaO was used, and the turbidity was approximately 0 NTU. These results indicate that addition of CaO is the best option for silica recovery from geothermal brine at the Yamagawa Power Plant. A practical-scale brine treatment plant has a treatment flow rate of 150 t/h. The estimated treatment cost at this time is 0.86–1.0 USD/ton of brine when DADMAC No. 6 was used and 0.83–1.48 USD when CaO was used. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coupled Cu and Sn-W mineralization were identified in the Tongshanling deposit. • The Cu and W-Sn mineralization occurred at ∼ 167 Ma and ∼ 162 Ma, respectively. • Cu and W-Sn mineralization resulted from granitoids with contrasting properties. • Chemical compositions of cassiterites indicate a concealed highly-evolved magmatism. • Most Cu-Sn deposits worldwide are spatially coupled with separated Cu and Sn sources. Formation of hydrothermal Cu and Sn deposits is thought to be related to magmas of differing oxygen fugacities, so the existence of mixed Cu-Sn hydrothermal ores poses a challenge to our understanding of the controls on their genesis. The Tongshanling polymetallic deposit in western Nanling Range (South China) is exceptional for its multiple mineralization types, which include skarn Cu-Pb-Zn and quartz-vein Sn-W-Pb-Zn mineralization, providing an excellent opportunity to reveal the genesis of coupled Cu-Sn deposits. An integrated study was carried out from petrological, mineralogical, geochronological, isotopic, and geochemical perspectives to determine the genesis of the Tongshanling polymetallic deposit and obtain a better understanding of coupled Cu-Sn mineralization processes. The granodiorite in the Tongshanling ore field is classified as oxidized I-type granitoids and emplaced at ∼ 167 Ma based on zircon U-Pb dating, and it is derived from partial melting of amphibolite-facies crustal rocks. In sharp contrast, the quartz porphyry and granite porphyry in the Tongshanling ore field were emplaced at ∼ 171 Ma and ∼ 162 Ma, respectively, both of which are highly evolved, reductive, and volatile-enriched A-type partial melts produced by remelting of granulite-facies crustal rocks. The close spatial relationship between the granodiorite and the skarn orebody is due to a ∼ 167 Ma skarn Cu-Pb-Zn mineralization event. In comparison, cassiterites from the quartz-vein ores define a later ore-forming event at ∼ 162 Ma, consistent with the intrusive age of the granite porphyry. Together with the crosscutting relationship of the quartz vein and skarn mineralization-related rocks (e.g., granodiorite, skarn, and sulfide ores), a ∼ 162 Ma Sn-W polymetallic mineralization event in the Tongshanling deposit may have been associated with a concealed, highly evolved granitic magmatism. Oxygen fugacity of the I-type granodiorite (median ΔFMQ = −1.47) is higher than those of the A-type quartz porphyry and granite porphyry (median ΔFMQ = −1.65 and −2.66, respectively), which may have been a key factor leading to multiple mineralization in the Tongshanling ore field. The chemical compositions of cassiterites indicate that the ore-forming fluid of the quartz-vein stage was reductive, volatile-enriched, and of magmatic origin. In addition, its temperature was lower than that commonly associated with greisen or pegmatite mineralization. These observations suggest that the Cu-Sn metallogeny of the Tongshanling polymetallic deposit was spatially-coupled rather than temporally-coupled, and that the genesis of this deposit can be explained with a two-stage metallogenic model. A comparative study of worldwide Cu-Sn deposits indicates that, in most cases, the Cu and Sn metals do not come from a single source, and that Cu-Sn deposits are a product of spatial coupling, i.e., sequential mineralization events within a single ore field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gold mineralization of the Longkou–Tudui deposit occurred in the early Cretaceous. • Magmatic rocks in this ore field have no genetical association with gold mineralization. • This deposit has a heavy sulfur source inherited from the Jingshan Group. • Fluid cooling and dilution processes were crucial to the gold mineralization. • The genesis of Longkou–Tudui gold deposit is similar to other Jiaodong gold deposits. The Jiaodong Peninsula in eastern China hosts numerous large and giant gold deposits. Recently, a set of gold deposits distributed along the Guocheng Fault have been identified as a new gold mineralization type, of which the Longkou–Tudui gold deposit is spatially associated with the Muniushan monzogranite whereas its genesis is poorly constrained. A systematic study including zircon U-Pb dating, fluid inclusions, C–H–O–S stable isotopes was carried out in order to determine the genesis of the Longkou–Tudui gold deposit. Zircon dating results indicate that the Muniushan monzogranite and dioritic porphyrite were emplaced at 2089–2066 Ma (with a metamorphism probably occurring at 1860 ± 27 Ma, MSWD = 0.98) and 115.6 ± 1.4 Ma, respectively. Combined with cross-cutting relationships of the Muniushan monzogranite, dioritic porphyrite, and gold orebodies, it is inferred that the gold mineralization occurred in the early Cretaceous. Fluid inclusion study demonstrates a H 2 O–NaCl ± CO 2 system, with a progressive decrease in average values of homogenization temperature and salinity from pre-ore to post-ore stages but a slight increase in bulk density. The ore-forming fluid is characterized by reductive, acidic, high to middle temperature, low salinity, and low density as revealed by a combined study on fluid inclusion and stable isotopes. H–O–C–S isotopic compositions indicate that the ore-forming materials have multiple sources including an inherited S source from the Jingshan Group, a mantle-derived C source, and a mixed H–O source induced by the addition of meteoric water. Compared with other Jiaodong gold deposits, the Longkou–Tudui deposit does not differ in mineralization age, nature and evolution of ore-forming fluid, and source of ore-forming materials except for orebody occurrence and heavier δ34S values inherited from the Jingshan Group, and this deposit was a byproduct of oceanic subduction of the Paleo Pacific Ocean. [ABSTRACT FROM AUTHOR]

Abstract: 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was used to investigate the effect of Zn2+ ion adsorption on Al(OH)3 gel. While as-prepared Al(OH)3 gel exhibits a single peak around 5ppm, the same gel with adsorbed Zn2+ has new peaks around 15 and 60ppm. These peaks correspond to AlO6 octahedral species with adsorbed Zn2+ and AlO4 tetrahedral species, respectively. In order to assess the mechanism for the formation of AlO4 tetrahedral species, hydroxide coprecipitates of Al3+ and Zn2+ were prepared and the chemical states of Al in the solids were observed by 27Al MAS NMR. The coprecipitates were found to have the AlO4 tetrahedral structure, except for those with high Zn/Al ratios. From these results, it can be assumed that adsorption of Zn2+ onto Al(OH)3 gel induces Al3+ dissolution followed by the coprecipitation of Al3+ with Zn2+ to form AlO4 tetrahedral structures on the surface of Al(OH)3 gel. [Copyright &y& Elsevier]

The Fukusen No. 1 vein is located in the southeastern part of the Yamada deposit, Hishikari epithermal gold deposits, southern Kyushu, Japan. Ar/Ar plateau ages of adularia from the margin and the center of the Fukusen vein are determined to be 0.617 ± 0.024 Ma and 0.606 ± 0.009 Ma, respectively. The Fukusen No. 1 vein shows banding structure composed mainly of quartz, adularia and clay minerals. Colloform texture is displayed by cryptocrystalline to amorphous silica material that is associated with fine-grained electrum and sulfides near the center of the vein. Pyrite in the Fukusen No. 1 vein often shows acicular shape resulting from inversion from marcasite. Near the center of the vein, primary marcasite occurs associated with colloform texture of silica. The Fukusen No.1 vein preserves primary texture and materials which were deposited from the ore-forming hydrothermal solution. The Fukusen No. 1 vein was formed in a short period and is one of the youngest veins in the Hishikari deposits. [ABSTRACT FROM AUTHOR]