Microthermometric and O‐ and H‐isotope characteristics of the mineralizing fluid in the Akgüney copper–lead–zinc deposit,NE Turkey

We use updated rotations within the Pacific-Antarctica-Africa-North America plate circuit to calculate Pacific-North America plate reconstructions for times since chron 13 (33 Ma). The direction of motion of the Pacific plate relative to stable North America was fairly steady between chrons 13 and 4, and then changed and moved in a more northerly direction from chron 4 to the present (8 Ma to the present). No Pliocene changes in Pacific-North America plate motion are resolvable in these data, suggesting that Pliocene changes in deformation style along the boundary were not driven by changes in plate motion. However, the chron 4 change in Pacific-North America plate motion appears to correlate very closely to a change in direction of extension documented between the Sierra Nevada and the Colorado Plateau. Our best solution for the displacement with respect to stable North America of a point on the Pacific plate that is now near the Mendocino triple junction is that from 30 to 12 Ma the point was displaced along an azimuth of ～N60°W at rate of ～33 mm/yr; from 12 Ma to about 8 Ma the azimuth of displacement was about the same as previously, but the rate was faster (～52 mm/yr); and since 8 Ma the point was displaced along an azimuth of N37°W at a rate of ～52 mm/yr.

We compare plate-circuit reconstructions of the edge of the Pacific plate to continental deformation reconstructions of North American tectonic elements across the Basin and Range province and elsewhere in order to evaluate the relationship of this deformation to the plate motions. The oceanic displacements correspond remarkably well to the continental reconstructions where deformations of the latter have been quantified along a path across the Colorado Plateau and central California. They also supply strong constraints for the deformation budgets of regions to the north and south, in Cascadia and northern Mexico, respectively.

We examine slab-window formation and evolution in a detailed re-analysis of the spreading geometry of the post-Farallon microplates, from 28 to 19 Ma. Development of the slab window seems linked to early Miocene volcanism and deformation in the Mojave Desert, although detailed correlations await clarification of early Miocene reconstructions of the Tehachapi Mountains. We then trace the post-20 Ma motion of the Mendocino slab window edge beneath the Sierran-Great Valley block and find that it drifted steadily north, then stalled just north of Sutter Buttes at ～4 Ma.     

Physico-chemical controls on ore deposition in the Arapucandere Pb–Zn–Cu-precious metal deposit,Biga Peninsula,NW Turkey

Arapucandere is one of a number of similar Cu–Zn–Pb ± Au–Ag epithermal deposits in the Biga Peninsula, which are mineralogically and tectonically similar. Fluid inclusions have very low salinities between 1.7 and 0 wt.% NaCl and a wide range of temperatures from ~ 360 to 160 °C. There was extensive boiling and “flashing” of the hydrothermal fluids which initiated mineral deposition. The range of temperatures is consistent with emplacement of the veins at ~ 700 m depth, with the pressure decreasing from near lithostatic to near hydrostatic and a decrease in temperature to ~ 250 °C due to adiabatic expansion of the fluids. There is evidence of a limited amount of boiling, but the temperature and pressure decrease was close to the liquid–vapour curve. Flashing of the fluids was caused by sudden drops to sub-hydrostatic pressures and even lower temperatures. Mineralization was caused by these pressure related temperature decreases as there is no evidence of cooling and dilution of the ore-fluids. δ³⁴S values of sulphides indicate a magmatic source but the more negative than usual values also suggest boiling affected isotopes. δD and δ¹⁸O of the fluids indicate a mixing between meteoric waters and magmatic fluids, with the large range of δD due to boiling. LA-ICP-MS analyses of fluid inclusions reveal high Cu–Zn–Pb concentrations in the fluids, despite their low salinity, transported as chloride complexes. Exceptional pressure and temperature decrease causing the fluids to “flash” was likely to have been in response to earthquakes.     

Ore textures and remobilization mechanisms of the Hongtoushan copper–zinc deposit,Liaoning, China

The Hongtoushan copper–zinc deposit is a volcanic-associated massive sulfide deposit in the Archean greenstone belt in Liaoning, China. Polymetamorphism has resulted in changes to the composition and textures of minerals in the deposit, along with remobilization. During metamorphism, the original alteration minerals that formed with the ore minerals, such as chlorite and sericite, were transformed into cordierite, anthophyllite, and phlogopite. After further remobilization, new minerals, such as gahnite and actinolite, were formed. In this process, the original textures were destroyed and new textures were formed, including recrystallization and growth textures, brittle and ductile deformation textures, durchbewegung textures, replacement textures, chalcopyrite disease, and retrograde textures. The ore-forming components underwent two periods of remobilization. In the first (early) stage, mechanical remobilization was important, and formed a high grade Cu–Zn–Au–Ag “ore pillar” along the vertical hinge of a synformal fold. In the second (late) stage, the mixed hydrothermal–mechanical remobilization affected the ores, and was typically characterized by matrix sulfides, together with silicate minerals, moving from the matrix into individual fractured pyrite metablasts and replacing them to varying degrees.     

Helium, lead and sulfur isotope geochemistry of the Gejiu Sn-polymetallic ore deposit and the sources of ore-forming materials

Studies on the helium, lead and sulfur isotopic composition were performed of the Gejiu super-large Sn-polymetallic ore deposit. The results indicated that the ore-forming materials came from different sources and the deposit is a product of superimposed mineralization. The deposit is characterized by multi-source and multi-period mineralization, which experienced submarine hydrothermal deposition and Late Yanshanian magmatic hydrothermal mineralization. It is held that the Gejiu super-large Sn-polymetallic ore deposit is a multi-genesis deposit.     

Geology and isotope geochemistry (C–O–S) of the Diyadin gold deposit,Eastern Turkey: A newly-discovered Carlin-like deposit

Diyadin mineralization is the first reported gold deposit located in a collisional tectonic environment in Eastern Anatolia. The mineralization is related to N–S and N10–20°W-trending fault systems and hosted within the Paleozoic metamorphic basement rocks of the Anatolide–Toride microcontinent. Calc-schist, dolomitic marble and Miocene and Quaternary volcanic rocks comprise the exposed units in the mineralized area. Geochemical signatures, alteration types and host rock characteristics of the Diyadin gold deposit resemble those of Carlin-type deposits. Mineralization is constrained by alteration of overlying volcanic rocks to younger than ~ 14 Ma (K–Ar).Carbon and oxygen stable isotope measurements of carbonate rocks were made on six drill holes (n = 81) with an additional four samples of fresh carbonate rocks from surface outcrops. Background carbonate rocks have δ¹³C_V-PDB ~ 1.8‰ and δ¹⁸O_V-SMOW ~ 27‰. Isotopically-altered host rock samples have decreased δ¹⁸O (down to ~+11.4‰) and variable δ¹³C (from − 3.6 to + 4.8‰). Postore carbonate veins and cave-fill material have distinctly different isotopic signatures, particularly carbon (from δ¹³C = + 8.4 to + 9.8‰). Whether this post-ore carbonate is simply very late in mineralization associated with the gold system, or is a completely different, younger system utilizing the same pathways, is unclear at present. Within the host rock sample set, there is no correlation between gold and δ¹³C, and a weak correlation between gold and δ¹⁸O, indicative of water–rock interaction and isotopic alteration. Both the isotopic data and structural mapping suggest that the main upflow zone for the deposit is near the northern portion of the drill fence. Additional data at multiple scales are required to clarify the relationship(s) between fluid flow and mineralization.     

SHRIMP U–Pb zircon ages and whole-rock geochemistry for the Şapçı volcanic rocks,Biga Peninsula,Northwest Turkey: implications for pre-eruption crystallization conditions and source characteristics

Palaeogene and Neogene volcanic rocks are widespread on the Biga Peninsula of Northwest Turkey. These rocks were formed during the Eocene, Oligocene–Miocene, and late Miocene, and the early Miocene ?apç? volcanic rocks in the Bal?kesir area consist of andesitic lava flows and associated pyroclastics. Temperatures, pressures, and oxygen fugacities calculated for the hornblendes in these andesitic rocks are 903–930°C, 3.3–4.8 kbar, and –9.91 to –11.88, respectively, and for the biotites they are 755–788°C, 1.30–1.74 kbar, and –14.88 to –13.98, respectively. SHRIMP U–Pb dating of zircons from three andesite samples gave ages of 22.72 ± 0.19, 22.97 ± 0.23, and 18.72 ± 0.17 Ma (early Miocene), and these are regarded as crystallization ages. Geochemical analyses show that the volcanic rocks are mainly high-K and calc-alkaline, and have high contents of large-ion lithophile elements and low contents of high-field strength elements, revealing that they evolved from parental magmas that were derived from an enriched subcontinental lithospheric mantle source. The chondrite-normalized rare earth element patterns of the rocks are concave upwards with La_CN/Lu_CN = 11.9–21.2 and Eu_CN/Eu* = 0.84–0.92, implying significant fractional crystallization of hornblende during their evolution. According to the petrological data with regional geology, Neogene magmatic activity on the Biga Peninsula has a post-collisional feature, and was closely related to slab break-off geodynamic model after collision of Tauride–Anatolide Block and Sakarya continent.     

Petrology and geochemistry of calc-alkaline volcanic and subvolcanic rocks,Dalli porphyry copper–gold deposit,Markazi Province,Iran

Early Miocene igneous rocks associated with the Dalli porphyry ore body are exposed within the Urumieh-Dokhtar Magmatic Arc (UDMA). The Dalli porphyry Cu–Au deposit is hosted by subduction-related subvolcanic plutons with chemical composition from diorite to granodiorite, which intruded andesitic and dacitic volcanic rocks and a variety of sedimentary sequences. ⁴⁰Ar/³⁹Ar age data indicate a minimum emplacement age of ～21 million years for a potasically altered porphyritic diorite that hosts the porphyry system. The deposit has a proven reserve of 8 million tonnes of rock containing 0.75 g/t Au and 0.5% Cu. Chondrite-normalized rare earth element (REE) patterns for the subvolcanic rocks are characterized by light REE enrichments [(La/Sm) _n ?=?2.57–6.40] and flat to gently upward-sloping profiles from middle to heavy REEs [(Dy/Yb) _n ?=?0.99–2.78; (Gd/Yb) _n ?=?1.37–3.54], with no significant Eu anomalies. These characteristics are generated by the fractionation of amphibole and the suppression of plagioclase crystallization from hydrous calc-alkaline magmas. In normalized multi-element diagrams, all analysed rocks are characterized by enrichments in large ion lithophile elements and depletions in high field strength elements, and display typical features of subduction-related calc-alkaline magmas. We used igneous mineral compositions to constrain the conditions of crystallization and emplacement. Biotite compositions plot above the nickel–nickel oxide (NNO) buffer and close to oxygen fugacity values defined by the hematite–magnetite (HM) buffer, indicating oxidizing conditions during crystallization. Assuming a minimum crystallization temperature of 775°C, the oxygen (fO₂) and water (fH₂O) fugacities are estimated to be 10^?10.3 bars (～ΔNNO+4) and ≤748 bars, respectively, during the crystallization of biotite phenocrysts. The temperature and pressure conditions, estimated from temperature–corrected Al-in-hornblende barometry and amphibole-plagioclase thermometry, suggest that the hornblende phenocrysts in Dalli rocks crystallized at around 780 ± 20°C and 3.8 ± 0.4 kbar. An alternative method using the calcic amphibole thermobarometer indicates that the Dalli magmas were, on average, characterized by an H₂O content of 4.3 wt.%, a relatively high oxygen fugacity of 10^?11.0 bars (ΔNNO+1.3), and a hornblende phenocryst crystallization temperature of 880 ± 68°C and pressure of 2.6 ± 1.7 kbar.     

Geochronology,geochemistry, and tectonic setting of the Oligocene magmatic rocks (Marmaros Magmatic Assemblage) in Gökçeada Island,northwest Turkey

Through the ?zmir–Ankara–Erzincan and the Vardar oceans suture zones, convergence between the Eurasian and African plates played a key role in controlling Palaeogene magmatism in northwestern Anatolia, northern Aegean, and eastern Balkans. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the tuffs of the Harmankaya Volcanic Rocks, which are inter-fingered with the lower-middle Eocene deposits of the Gaziköy Formation to the north of the Ganos Fault and the Karaa?aç Formation in the Gelibolu Peninsula, yielded a late Ypresian (51 Ma) age. The chemical characteristics suggest that the lavas and tuffs of the Harmankaya Volcanic Rocks are products of syn- or post-collision magmas. These volcanic rocks show also close affinities to the subduction-related magmas. In addition to the already known andesitic volcanic rocks, our field observations in Gökçeada Island indicate also the existence of granitic and rhyolitic rocks (Marmaros Magmatic Assemblage). Our U–Pb zircon age data has shown that the newly discovered Marmaros granitic plutons intruded during late Oligocene (26 Ma) into the deposits of the Karaa?aç Formation in Gökçeada Island. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the Marmaros rhyolitic rocks yielded a late Oligocene (26 Ma) crystallization age. Geochemical characteristics indicate that the more-evolved Oligocene granitic and rhyolitic rock of the Marmaros Magmatic Assemblage possibly assimilated a greater amount of crustal material than the lower Eocene Harmankaya Volcanic Rocks. Geochemical features and age relationships suggest increasing amounts of crustal contamination and a decreasing subduction signature during the evolution of magmas in NW Turkey from the early Eocene to the Oligocene. The magmatic activity developed following the northward subduction of the ?zmir–Ankara–Erzincan oceanic lithosphere and the earliest Palaeocene final continental collision between the Sakarya and Anatolide–Tauride zones.     

Geology,geochemistry and sulphur isotopes of the Hat Han gold–antimony deposit,NE Vietnam

The Song Hien Rift basin is considered as one of the important regions for gold deposits in North East Vietnam. Host rocks of a number gold deposits in the Song Hien Rift basin are mainly in Lower Triassic sedimentary formations. However, there is the Hat Han gold deposit hosted in fined-grained mafic magmatic rocks with similar characteristics as gold deposit hosted in the Triassic sediments. Sulphur isotopic compositions of sulphide are similar to those in carbonaceous shale, suggesting that the sulphur was ‘borrowed’ from sedimentary rocks in filling the rift basin. Gold-bearing sulphides (pyrite and arsenopyrite) are the main form of Au presence in the ore. Gold in pyrite is present as Au^+ 1, and a minor amount of as nanoparticles of native Au (Au⁰); whereas in arsenopyrite, gold is chemically bound as the octahedral complex AuAs₂. Analysis of geology, as well as geochemical and isotopic studies show that the genesis of the Hat Han gold deposit is not related to the Cao Bang mafic magmatism; instead the latter only serves as (ore) host rock. The geochemical results presented above suggest that the gabbro host rock only supplies iron needed for sulphide formation. With regard to ore genesis, the Hat Han gold deposit in the Song Hien rift basin was generated in the similar way as sediment-hosted gold deposit. There are many similar typomorphic features between the Hat Han deposit and Carlin-like deposits in the Nanpanjang sedimentary basin in China.     

New data for geology and geochemistry of the Rodion gold–quartz deposit,northeastern Russia

This paper is focused on the new data for geology, mineralogy, and geochemistry of stockworks consisting of steep and gentle quartz veins and veinlets forming a complex multilevel structure at the Rodion deposit. These stockworks range from 25 to 150 m in thickness. Average gold grade is 1.8 g/t. Ore minerals pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, and native gold are predominantly concentrated on the vein and veinlet walls. Thermal metamorphism caused by the intrusion of the Ulakhan granodiorite pluton is the important singularity of the deposit. The deposit ore is enriched in chalcophile microelements Au, Ag, As, Sb, Cu, Pb, Zn, and Bi as compared to the average composition of the upper crust and hosting Permian sequences. The enrichment factors range from a few to hundreds of times. Bi, W, Pb, Ag, and Na₂O are positively correlated between each other and with Au. The highest correlation coefficient 0.59 is between Au and Bi. Au is negatively correlated with Ba, Li, Co, Ni, Mn, Ti, and Be. The stockwork ores were formed involving homogeneous low-saline (9.4–4.3 wt % NaCl equiv) substantially aqueous bicarbonate-chloride fluid at 275–330°C and 300–1840 bar fluid pressure. Fluid has a high concentration of CO₂ (up to 349 g/kg of water) and is reductive (СО₂/СН₄ = 17–37.3). Na and Ca are the major cations in the fluid, whereas K and Mg are minor. In addition, many microelements were detected in the fluid: As, Li, Rb, Cs, Mo, Ag, Sb, Cu, Zn, Cd, Pb, U, Ga, Ge, Ti, Mn, Fe, Co, Ni, V, Cr, Y, Zr, Sn, Ba, W, Au, Hg, and REE. The results obtained are consistent with the metamorphic–magmatic formation model of orogenic gold–quartz deposits within the Yana–Kolyma belt.     

Environmental assessment of the arsenic-rich,Rodalquilar gold–(copper–lead–zinc) mining district,SE Spain: data from soils and vegetation

The Rodalquilar mineral deposits (SE Spain) were formed in Miocene time in relation to caldera volcanic episodes and dome emplacement phenomena. Two types of ore deposits are recognized: (1) the El Cinto epithermal, Au–As high sulphidation vein and breccia type; and (2) peripheral low sulphidation epithermal Pb–Zn–Cu–(Au) veins. The first metallurgical plants for gold extraction were set up in the 1920s and used amalgamation. Cyanide leaching began in the 1930s and the operations lasted until the mid 1960s. The latter left a huge pile of ~900,000–1,250,000 m³ of abandoned As-rich tailings adjacent to the town of Rodalquilar. A frustrated initiative to reactivate the El Cinto mines took place in the late 1980s and left a heap leaching pile of ~120,000 m³. Adverse mineralogical and structural conditions favoured metal and metalloid dispersion from the ore bodies into soils and sediments, whereas mining and metallurgical operations considerably aggravated contamination. We present geochemical data for soils, tailings and wild plant species. Compared to world and local baselines, both the tailings and soils of Rodalquilar are highly enriched in As (mean concentrations of 950 and 180 μg g⁻¹, respectively). Regarding plants, only the concentrations of As, Bi and Sb in Asparagus horridus, Launaea arborescens, Salsola genistoides, and Stipa tenacissima are above the local baselines. Bioaccumulation factors in these species are generally lower in the tailings, which may be related to an exclusion strategy for metal tolerance. The statistical analysis of geochemical data from soils and plants allows recognition of two well-differentiated clusters of elements (As–Bi–Sb–Se–Sn–Te and Cd–Cu–Hg–Pb–Zn), which ultimately reflect the strong chemical influence of both El Cinto and peripheral deposits mineral assemblages.     

Geology,fluid inclusions,and geochemistry of the Zhazixi Sb–W deposit,Hunan, South China

The Zhazixi Sb–W deposit in the Xuefeng uplift, South China, exhibits a unique metal association of W and Sb, where the W orebodies are hosted by interlayer fractures and the Sb orebodies are contained within NW-trending faults. This study proposes that the W and Sb mineralization took place in two separate periods. The mineral paragenesis of the W mineralization reveals a mass of quartz, scheelite and minor calcite. The mineral assemblage of the Sb mineralization developed after W mineralization and consists of predominantly quartz and stibnite, and small amounts of native Sb, berthierite, chalcostibnite, pyrite, and chalcopyrite. Fluid inclusions in quartz and coexisting scheelite are dominated by two-phase, liquid-rich, aqueous inclusions at room temperature. Microthermometric studies suggest that ore-forming fluids for W mineralization are characterized by moderate temperatures (170–270 °C), low salinity (3–7 wt% NaCl equiv.), low density (0.75–0.95 g/cm³), and moderate to high pressure (57.2–99.7 MPa) and these fluids experienced a cooling and dilution evolution during W mineralization. Ore-forming fluids for Sb mineralization are epithermal types with low temperatures (150–230 °C), low salinity (4–6 wt% NaCl equiv.), moderate density (0.82–0.94 g/cm³), and high pressure (42.2–122.5 MPa) and these fluids display an evident decline in homogenization temperature during Sb mineralization. Laser Raman analyses of the vapor phase indicate that the ore-forming fluids for both W and Sb mineralization contain a small amount of CO₂.The ore-forming fluids for Sb mineralization are identified as predominantly originating from the continental crust, as suggested by the low ³He values (0.009 × 10⁻¹² cc.STP/g) and ³He/⁴He ratios (0.002–0.056 Ra) as well as high ³⁶Ar values (1.93 × 10⁻⁹ cc.STP/g) and ⁴⁰Ar/³⁶Ar ratios (909.5–2279.7). The source of S is identified to be the Neoproterozoic Wuqiangxi Formation, as traced by the δ³⁴S_V-CDT values of stibnite (3.1–9.4‰). The ²⁰⁸Pb/²⁰⁴Pb (37.643–40.222), ²⁰⁷Pb/²⁰⁴Pb (15.456–15.681), and ²⁰⁶Pb/²⁰⁴Pb (17.093–20.042) ratios suggest a mixture of lower crustal and supracrustal Pb sources.It is thus concluded that the ore genesis of the Zhazixi Sb–W deposit is related to the intracontinental orogeny during the early Mesozoic. Fluid mixing is considered to be the critical mechanism involved in W mineralization, whereas a fluid cooling process is responsible for Sb mineralization. Furthermore, the absence of Au is attributed to the low Σa_s content in Sb-mineralizing fluids.     

Se and In minerals in the submarine oxidation zone of a massive sulfide orebody of the molodezhnoe copper–zinc massive sulfide deposit,Southern Urals

For the first time, extremely high Se and In contents were determined for the pinches of massive sulfide orebodies that are composed of small-clastic layered sulfide sediments transformed during submarine supergenesis. Se (clausthalite and naumannite) and In (roquesite) minerals were found. Hydrothermal chalcopyrite, a significant amount of which is present in the clasts of paleohydrothermal black smoker chimneys, was the source of Se. Most of the amount of In was contributed during dissolution of clasts of hydrothermal sphalerite, which is unstable in the submarine oxidation zone in the presence of oxidized pyrite.     

Genesis of the Huangshannan high-Ni tenor magmatic sulfide deposit in the Eastern Tianshan,northwest China: Constraints from PGE geochemistry and Os–S isotopes

The Huangshannan magmatic Ni-Cu sulfide deposit is one of a group of Permian magmatic Ni-Cu deposits located in the southern Central Asian Orogenic belt in the Eastern Tianshan, northwest China. It is characterized by elevated Ni tenor (concentrations in recalculated 100% sulfide) in sulfide within ultramafic rocks (9–19 wt%), with values much higher than other deposits in the region. Sulfides of the Huangshannan deposit are composed of pentlandite, chalcopyrite, and pyrrhotite and the host rock is relatively fresh, indicating that the high-Ni tenor is a primary magmatic feature rather than formed by alteration processes. It is shown that sulfides with high-Ni tenor can be generated by sulfide-olivine equilibrium at an oxygen fugacity of QFM +0.5, for magmas containing 450 ppm Ni and 20% olivine. Ores with >10 wt% sulfur have relatively low PGE and Ni tenors compared to other ores, R factor (mass ratio of silicate to sulfide liquid) modeling of Ni indicates that they formed at moderate R values (150–600). Based on this constraint on R values, ores with <10 wt% sulfides in the Huangshannan deposit can be segregated from a similar parental magma with 0.05 ppb Os, 0.023 ppb Ir, and 0.5 ppb Pd at R values between 600 and 3000. This, coupled with the supra-cotectic proportions of sulfide liquid to cumulus silicates in the Huangshannan ores imply mechanical transport and deposition of sulfide liquid in a magma pathway or conduit, in which sulfides must have interacted with large volumes of silicate magma. Platinum and Pd depletion relative to other platinum group elements (PGEs) are observed in fresh and sulfide-rich samples (S > 4.5 wt%). As sulfide-rich samples are also depleted in Cu, and as interstitial sulfides in those samples are physically interconnected at a scale of several cms, the low Pt and Pd anomalies are attributed to solid Pt and Pd phases crystallization and retention with the monosulfide solid solution (MSS) and Cu-rich sulfide liquid percolation during MSS fractionation. This finding indicates that Pt anomalies in sulfide-rich rocks from magmatic Ni-Cu deposits in the Eastern Tianshan are the result of sulfide fractionation rather than a hydrothermal effect. ¹⁸⁷Os/¹⁸⁸Os_(278Ma) values of the lherzolite samples vary from 0.27 to 0.37 and γOs_(278Ma) values vary from 110 to 189, indicating significant magma interaction with crustal sulfides, rich in radiogenic Os. Well constrained γOs values and δ³⁴S values (−0.4 to 0.8‰) indicate that crustal contamination occurred at depth before the arrival of the magma in the Huangshannan chamber. Regionally, deposits with high-Ni tenor have not been reported other than the Huangshannan deposit; however, many intrusions with high-Ni contents in olivine are present in NW China, such as the Erhongwa, Poyi and Poshi intrusions. Those intrusions are capable of forming high-Ni tenor sulfides due to olivine-sulfide-silicate equilibrium and relative high-Ni content in parent magma, making them attractive exploration targets.     

Arsenite removal from water by electro-coagulation on zinc–zinc and copper–copper electrodes

Removal of arsenite from aqueous solution was carried out using electro-coagulation method. The experiments were conducted using copper–copper and zinc–zinc electrodes. The optimized experimental parameters were 2.0 mg/L initial concentration, 16.0-min processing time, 6.0 pH, 3.0-V applied voltage and 30 °C temperature for zinc–zinc electrodes while these values for copper–copper electrodes were 2.0 mg/L initial concentration, 20.0-min processing time, 7.0 pH, 5.0-V applied voltage and 30 °C temperature. The results demonstrated that zinc–zinc and copper–copper electrodes removed arsenite up to 99.89 and 99.56 %, respectively. The treated water was clear, colorless and odorless without any secondary contamination. There was no change in water quality after the removal of arsenite. The reported method is capable to remove arsenite from water at 6–7 pH range, which is a pH range of natural water. Therefore, this method may be the choice of arsenite removal from natural ground water.     

Geology,isotope geochemistry and ore genesis of the Shanshulin carbonate-hosted Pb–Zn deposit,southwest China

The Shanshulin Pb–Zn deposit occurs in Upper Carboniferous Huanglong Formation dolomitic limestone and dolostone, and is located in the western Yangtze Block, about 270 km west of Guiyang city in southwest China. Ore bodies occur along high angle thrust faults affiliated to the Weishui regional fault zone and within the northwestern part of the Guanyinshan anticline. Sulfide ores are composed of sphalerite, pyrite, and galena that are accompanied by calcite and subordinate dolomite. Twenty-two ore bodies have been found in the Shanshulin deposit area, with a combined 2.7 million tonnes of sulfide ores grading 0.54 to 8.94 wt.% Pb and 1.09 to 26.64 wt.% Zn. Calcite samples have δ¹³C_PDB and δ¹⁸O_SMOW values ranging from − 3.1 to + 2.5‰ and + 18.8 to + 26.5‰, respectively. These values are higher than mantle and sedimentary organic matter, but are similar to marine carbonate rocks in a δ¹³C_PDB vs. δ¹⁸O_SMOW diagram, suggesting that carbon in the hydrothermal fluid was most likely derived from the carbonate country rocks. The δ³⁴S_CDT values of sphalerite and galena samples range from + 18.9 to + 20.3‰ and + 15.6 to + 17.1‰, respectively. These values suggest that evaporites are the most probable source of sulfur. The δ³⁴S_CDT values of symbiotic sphalerite–galena mineral pairs indicate that deposition of sulfides took place under chemical equilibrium conditions. Calculated temperatures of S isotope thermodynamic equilibrium fractionation based on sphalerite–galena mineral pairs range from 135 to 292 °C, consistent with previous fluid inclusion studies. Temperatures above 100 °C preclude derivation of sulfur through bacterial sulfate reduction (BSR) and suggest that reduced sulfur in the hydrothermal fluid was most likely supplied through thermo-chemical sulfate reduction (TSR). Twelve sphalerite samples have δ⁶⁶Zn values ranging from 0.00 to + 0.55‰ (mean + 0.25‰) relative to the JMC 3-0749L zinc isotope standard. Stages I to III sphalerite samples have δ⁶⁶Zn values ranging from 0.00 to + 0.07‰, + 0.12 to + 0.23‰, and + 0.29 to + 0.55‰, respectively, showing the relatively heavier Zn isotopic compositions in later versus earlier sphalerite. The variations of Zn isotope values are likely due to kinetic Raleigh fractional crystallization. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of the sulfide samples fall in the range of 18.362 to 18.573, 15.505 to 15.769 and 38.302 to 39.223, respectively. The Pb isotopic ratios of the studied deposit plot in the field that covers the upper crust, orogenic belt and mantle Pb evolution curves and overlaps with the age-corrected Proterozoic folded basement rocks, Devonian to Lower Permian sedimentary rocks and Middle Permian Emeishan flood basalts in a ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb diagram. This observation points to the derivation of Pb metal from mixed sources. Sphalerite samples have ⁸⁷Sr/⁸⁶Sr_200 Ma ratios ranging from 0.7107 to 0.7115 similar to the age-corrected Devonian to Lower Permian sedimentary rocks (0.7073 to 0.7111), higher than the age-corrected Middle Permian basalts (0.7039 to 0.7078), and lower than the age-corrected Proterozoic folded basement (0.7243 to 0.7288). Therefore, the Sr isotope data support a mixed source. Studies on the geology and isotope geochemistry suggest that the Shanshulin deposit is a carbonate-hosted, thrust fault-controlled, strata-bound, epigenetic, high grade deposit formed by fluids and metals of mixed origin.     

Geochronology and geochemistry of the Wunugetushan porphyry Cu–Mo deposit in NE china,and their geological significance

The Wunugetushan porphyry Cu–Mo deposit is located in the Manzhouli district of NE China, on the southern margin of the Mesozoic Mongol–Okhotsk Orogenic Belt. Concentric rings of hydrothermal alteration and Cu–Mo mineralization surround an Early–Middle Jurassic monzogranitic porphyry. The Cu–Mo mineralization is clearly related to the quartz–potassic and quartz–sericite alteration. Molybdenite Re–Os and groundmass ⁴⁰Ar/³⁹Ar of the host porphyry dates indicate that the ore-formation and porphyry-emplacement occurred at 177.6 ± 4.5 Ma and 179.0 ± 1.9 Ma, respectively. Geochemically, the host porphyry of the deposit is characterized by strong LREE/HREE fractionation, enrichment in LILE, Ba, Rb, U, Th and Pb, and depletion of HFSE, Nb, Ta, Ti and HREE. The Sr–Nd–Pb isotopic compositions of the porphyry display an varied initial (⁸⁷Sr/⁸⁶Sr)_i ratio, a positive ε_Nd(t) values and high ²⁰⁶Pb/²⁰⁴Pb_t, ²⁰⁷Pb/²⁰⁴Pb_t and ²⁰⁸Pb/²⁰⁴Pb_t ratios. These data indicate that the magmatic source of the host porphyry comprised two end-members: lithospheric mantle metasomatized by fluids derived from the subducted slab; and continental crust. We infer that the primitive magma of the host porphyry was derived from crust–mantle transition zone. Based on regional geology and geochemistry of the host porphyry, the Wunugetushan deposit is suggested to form in a continental collision environment after closure of the Mongol–Okhotsk Ocean.     

Geochronology,geochemistry and Sr–Nd–Hf isotopes of the Haisugou porphyry Mo deposit,northeast China,and their geological significance

The Haisugou Mo deposit is located in the northern part of the Xilamulun Mo–Cu metallogenic belt in northeastern China. The Mo mineralization mainly occurs as quartz-molybdenite veins within the Haisugou granite, which was emplaced into rocks of the Early Permian Qingfengshan Formation. Zircon U–Pb dating by LA–ICP-MS of the granite yields a crystallization age of 137.6 ± 0.9 Ma, suggesting emplacement during the peak time of Mo mineralization in eastern China, broadly constrained to ca. 150–130 Ma, when tectonic stresses shifted from compression to extension. Whole-rock geochemical data suggest that the granite belongs to the high-K calc-alkaline series, and is characterized by relatively high LREE; low HREE; depletion of Ti, Ba, and Nb; and a moderate negative Eu anomaly. The zircon ε_Hf(t) and whole-rock ε_Nd(t) values for the intrusion range from +4.5 to +10.0 and +0.2 to +1.6, respectively, indicating that the magma originated from the juvenile lower crust source derived from depleted mantle, with some component of ancient continental crust. The granite is also characterized by initial (⁸⁷Sr/⁸⁶Sr)_i ratios ranging from 0.7040 to 0.7074, which suggest some contamination by the upper crust during the ascent of the primitive magma. Moreover, it can be recognized from the whole-rock major and trace element data that significant fractional crystallization occurred during magmatic evolution, with the separation of plagioclase and K-feldspar. Because Mo is an incompatible element and tends to concentrate in the melt during crystallization, fractionation processes likely played an important role in the formation of the Haisugou Mo deposit.     

Major and trace element geochemistry of the Bigadi? Borate deposit, Balikesir, Turkiye

This study investigates the major and trace element geochemistry of Bigadi borate deposits, the largest colemanite and ulexite deposits in the world. The known borate deposits of Turkiye were deposited in the lacustrine environment during Miocene when the volcanic activity occurred from Tertiary to Quaternary. All of the Turkish borate deposits are classified as volcanic related deposits. Boron ore deposits intercalated with claystone, mudstone, tufa and fine layered limestone show lens shape. Borate minerals formed in two zones. Tiilu and Acep-Simav open mines represented the lower and upper borate zones, respectively. Colemanite and ulexite are dominant minerals at all ore zones. The major elements of Bigadi borates contain Ca, Si, Mg, Al, Fe, S, Na, P and Mn at Tiilu, Ca, Na, Si, Mg, S, Al, P and Mn at Simav, and Ca, Na, Si, Mg, S, AI and Mn at Acep samples respectively. Except for Li, Mo, Sb, As, Sr and Se, concentrations of other trace elements are significantly lower than averages of earth crust and andesite at the three mines. With respect to averages of earth crust and andesite, Mo, Sr, As, Li and particularly Se are enriched significantly in the Bigadi. In examining depth-dependent variations of major and trace elements, four element groups at the Tiilu site and six element groups at the Simav and Acep sites were determined. Element abudances or element geochemical trends show differences at the Tülü, Simav and Acep mines. These differences can be explained by the diversity of physicochemical conditions in the deposition environment by the effect of differences at the recharge regime and source.