Abstract:Numerous volcanic rocks crop out along eastern and western marginal areas of the Lanping basin in the middle segment of the Sanjiang multiple orogenic and metallogenic belt in western Yunnan Province. However, copper deposits are developed exclusively on the western margin of the basin, which form a vein-type copper metallogenic belt about 150 km in length. Most vein-like copper orebodies are hosted in volcanic and strongly deformed sedimentary rocks. However, the age of the ore-hosting rocks remains unclear. Detailed field study and zircon U/Pb analysis of andesitic pyroclastic rocks were conducted in the Dazong copper ore deposit located in north-central segment of the western Lanping copper metallogenic belt. The lithology of two zircon U-Pb dating samples is crystal and vitric tuff, volcanic breccia-bearing tuff respectively, which represented the first and second rhythm of the volcano-eruptive sedimentary cycle. Some conclusions have been reached: ① the ore-hosting volcanic rocks have a thickness of 1 904 meters consisting of three volcanic sequences;② the ²⁰⁶Pb/²³⁸U weighted average age of magmatic zircons of the first rhythm tuff layer is 247.2±4.4 Ma (n=21,MSWD=2.7), and the ²⁰⁶Pb/²³⁸U weighted average age of magmatic zircons of the second rhythm tuff layer is 243.8±6.4 Ma (n=9, MSWD= 1.5),suggesting that the volcanism took place in 244~247 Ma,which belongs to Early to Middle Triassic; and ③ the strongly deformed sedimentary rocks were overlain by the Early Triassic volcanic rocks, and thus should belong to the Upper Permian. Therefore, the ore-hosting volcanic-sedimentary assemblage in the Dazong copper orefield formed during the Late Paleozoic to Early Mesozoic, and might have resulted from the Paleo-Tethyan orogenic movement. According to the difference of the ore-hosting rocks, the Dazong Early to Middle Triassic volcanic rocks-hosted copper sulfide mineralization is only one type of many vein-type copper deposits in the western margin vein-type copper metallogenic belt of the Lanping basin. These vein-type copper deposits or ore occurrences all have no obvious strata or lithologic specificity, and should be classified as a strong tectonic deformation controlled and post-filling hydrothermal deposit.

Abstract:The Suoerbasitawu quartz diorite in the Yemaquan area of East Junggar, Xinjiang, has a zircon U-Pb age of 442.5±5.6 Ma. The quartz diorite has the data SiO₂=63.75%~65.40%, Al₂O₃=17.07%~18.00%, Na₂O/K₂O=5.28~6.82, and MgO=1.11%~1.35%. They are characterized by enrichment of large ion lithophile elements (LILEs, such as K, Rb, Ba, and Sr), and depletion of high field strength elements (HFSEs, such as Ta, Nb, Zr, and Ti) and P. They also have the data Sr=783×10^-6~1 030×10^-6, Y=8.10×10^-6~10.80×10^-6, Yb=0.84×10^-6~1.04×10^-6, and Sr/Y=82.59~112.32, showing typical characteristics of adakitic rocks. The rocks have relatively low (⁸⁷Sr/⁸⁶Sr)_i (0.703 77~0.704 04) and high εNd(t) (+6.9~+7.2), and relatively high zircon εHf(t) (+10.7~+13.7), indicating that the magma was probably derived from an depleted juvenile mantle, similar to the adakitic rocks formed by the partial melting of subducted oceanic crust. In combination with the regional geological background, the authors hold that the Suoerbasitawu quartz diorite was formed by the partial melting of subducted oceanic slab edge heated by the asthenospheric mantle, which was the magmatic arc formed by the southward subduction of the Paleo-Asian oceanic crust in the early Silurian period.

Abstract:The Yamansu Formation, outcropped along the Aqishan-Yamansu belt, is a Late Paleozoic stratigraphic unit that hosts many important iron metallogenetic deposits in eastern Tianshan orogenic belt, Xinjiang. The Yamansu Formation consists of intercalated volcanic and sedimentary rocks. LA-ICP-MS U-Pb analyses of zircons from dacite in the upper part of the Yamansu Formation and syenite cutting across the skarns and iron orebodies in the Yamansu iron deposit area yielded weighted mean ²⁰⁶Pb/²³⁸U ages of 334.4±1.7 Ma (MSWD=0.67) and 325.5±1.7 Ma (MSWD=0.34), respectively. These ages indicate that the Yamansu Formation was formed during the early Carboniferous and the Yamansu iron orebodies and mineralizations preferentially occurred between 334 and 325 Ma. Geochemically, the dacite displays typical arc-like magmatic rocks characteristics, e.g., enrichment of large ion lithophile elements (LILE) and light rare earth element (LREE), strong negative anomalies of Nb, Ta and Ti with positive εHf(t) values (+3.0 to +8.0), and relatively young Hf crustal model ages. They were probably derived from the dehydration melting of juvenile crustal materials with minor mantle melting and underwent fractional crystallization during the upward migration of magma. The basalts resemble dacites in enrichment of LREE, U and Sr and depletion of Nb, Ta, Zr and Hf, and were probably derived from depleted mantle and mantle wedge modified by fluids from subducted materials. The regional geology and geochemical evidence indicate that the Yamansu Formation volcanic rocks were formed during the early Carboniferous in an active continental margin arc tectonic setting, indicating that the Paelo-Asia Ocean had not been closed. The Yamansu Fe deposit hosted in the Yamansu Formation was formed during 334~325 Ma, closely associated with Late Paleozoic volcanism.

Abstract:The gabbroic intrusions are situated along the Cenxi-Wuzhou fault zone in Xindi-Anping area, southeastern Guangxi. Petrographic studies indicate that these rock bodies intruded into the Lower Paleozoic or Sinian strata, and were covered by Cretaceous. The gabbroic intrusions are mainly composed of amphibolite gabbro, hypersthene-amphibolite gabbro and minor plagioclase-bearing pyroxenite, gabbro-diorite and diabase (-porphyry). LA-MC-ICP-MS zircon U-Pb dating results yielded a weighted mean ²⁰⁶Pb/²³⁸U age of 249.1±2.8 Ma (MSWD=0.44) for the amphibolite gabbro, suggesting an emplacement of Early Triassic. Geochemical analysis shows that the gabbroic intrusions are characterized by relatively low MgO (2.13%~3.59%) values and relatively high Fe₂O₃^T (16.42%~33.53%), P₂O₅ (0.58%~1.18%) and TiO₂ (1.52%~2.31%) values, and that the intrusions are relatively enriched in large ion lithophile elements (LILE: Ba, Rb and U) and relatively depleted in high field strength elements (HFSE: Nb-Ta, Zr-Hf and Ti). Such signatures display geochemical characteristics of typical subduction-related arc volcanic rocks, which suggests that the gabbros were formed in an active continental margin (continental arc) setting. In combination with the regional tectonic evolution, the authors consider that there existed a Paleozoic paleo-ocean basin in the southwestern segment of joint belt between Yangtze and Cathaysia plates (so-called Qinzhou-Hangzhou joint belt), and the oceanic basin had not been closed until the Indosinian orogeny in middle Triassic. The continental arc gabbro in the region was an important record of this oceanic lithosphere subduction during the Paleozoic period.

Abstract:Blueschist sporadically occurs as lenses within Lancangjiang metamorphic complex. The combined studies of petrography, geochemistry, genetic mineralogy and phase equilibrium modeling for blueschists within Xiaoheijiang-Shangyun area provide a significant insight into protoliths and metamorphic evolution. Geochemical features show that they have similar rare-earth elements(REE) patterns, with slight Eu anomalies. REE and trace elements compositions have an affinity to those of oceanic island basalts(OIB),suggesting that their protoliths were OIB-type basalts. Petrological studies show that blueschists contain two distinct mineral assemblages characterized by glaucophane+albite+phengite+chlorite+epidote+titanite, glaucophane+albite±actinolite+chlorite+epidote+titanite which record a peak blueschist phase, a greenschist phase. Calculated pseudosection in the system Na₂O-CaO-FeO-MgO-Al₂O₃-SiO₂-H₂O-O yielded pressure conditions of around 0.95 GPa, 0.40 GPa, respectively.

Abstract:The Lietinggang deposit is a newly discovered typical large-sized polymetallic deposit in the Fe-Mo-Cu-Pb-Zn ore concentration area of the Linzhou basin. There are mainly three types of magnetites in this mining area, i.e., massive, disseminated and veined magnetite. On the basis of detailed geological survey and systematic mineralogical studies, the metallogenic period of this deposit can be divided into two periods, i.e., skarn period and hydrothermal and supergene period, which include five ore-forming stages: early skarn stage, degradation and alteration stage, early hydrothermal stage, quartz-sulfide stage and carbonatization stage. The massive magnetite mainly formed at the degradation and alteration stage, whereas both the disseminated and veined magnetites formed at the early hydrothermal stage. In this study, the authors selected the magnetites as the main object of study and used electron microprobe analysis (EPMA) and rare earth trace elements ICP-MS experiments to gain an insight into the geochemical characteristics and minerageny of magnetites. The results show that three different types of magnetites (massive, veined and disseminated magnetites) contain Ti, Si, Ca and other minor elements such as Na, K, Cr, Ni, Co, Pb, Ba, Sn. In addition, a variety of trace elements like Sr, Sb and Cu can be detected. There are mainly Al, Mg and Mn replacing the other elements. Combining TiO₂-Al₂O₃-MgO, TiO₂-Al₂O₃-(MgO+MnO) and (Ca+Al+Mn)-(Ti+V), Ni/(Cr+Mn)-(Ti+V), and other discrimination diagrams with orefield geological characteristics, the authors have reached the conclusion that the magnetites of the Lietinggang deposit belong to hydrothermal magnetite. The massive magnetite has obvious positive Eu anomaly, the disseminated and veined magnetites show negative Eu anomaly, and they all have no significant Ce anomalies. The massive magnetites might have been formed in an environment of high oxidation and temperature with the fluids rich in Eu. At the hydrothermal stage, the fluids were gradually transformed into a low temperature and oxidation which could contribute to the formation of disseminated, veined magnetites and a large quantity of sulfides. Moreover, the main sources of iron materials were related to granodiorite and porphyry granite.

Abstract:LA-ICP-MS analyses of rutile and titanite from eclogites and veins from high pressure-ultrahigh pressure (HP-UHP) metamorphic belt of southwestern Tianshan Mountains in Xinjiang were carried out for testing the Zr content and calculating the Zr-in-rutile and Zr-in-titanite thermometers. Rutile inclusions in garnet mantle, coexisting with omphacite, have a narrower range of Zr values of 10~20 μg/g. The Zr content of matrix rutiles is higher than that of rutile inclusions in garnet, with Zr values being 30~50 μg/g. Titanite is the retrograde product of rutile. Zr values of titanite are homogeneous between individual grains, even among different samples, concentrated between 3 μg/g and 5 μg/g. The Zr concentrations in rutile from the veins are equivalent to those from the eclogites, or even higher. The Zr concentrations of rutile in vein are 30~60 μg/g. Rutile inclusions in garnet mantle grow in the peak pressure metamorphic stage and Zr-in-rutile thermometers gave the estimated temperature of 480~540℃ at 2.7~3.0 GPa. Matrix rutiles can re-equilibrate easily along with the increase of temperature during retrogression, and record the peak temperature condition of 530~590℃, 2.4~2.7 GPa. Rutiles in high pressure veins grow in eclogite facies metamorphism stage, and the growth temperature of vein rutile is 540~580℃, 1.5~2.1 GPa. Titanite in eclogite is the secondary product of rutile, and reaches equilibrium at about 1.0 GPa. Zr-in-titanite thermometry gave the estimated temperature of 540~560℃, recording the further isothermal decompression process. Combined with the analytical results above, the authors constructed a relatively complete clockwise p-T path, which is consistent with the result of phase equilibrium modeling. Zr in rutile from eclogites and veins can serve as a pressure indicator that suggests that the pressure has a significant effect on the Zr-in-rutile thermometry. In the specific case, combined with detailed petrographic observation and consideration of the pressure, the activity of TiO₂ and SiO₂, diffusion rate, retrograde metamorphism and fluid effect, Zr-in-rutile and Zr-in-titanite thermometers can give an accurate p-T estimate and p-T path.

Abstract:The discovery of the Duobuza copper deposit is a major breakthrough of geological prospecting work in Tibet. Previous studies have done a lot of research, but failed to explain the formation process of the deposit. The reason is mainly because of the controversy in the understanding of the source of ore-forming materials and ore-forming fluids. In this study, the authors pointed out the problems existing in the understanding of the genetic mechanism of the Duobuza copper deposit, and investigated the sulfur and lead isotopic compositions of rocks and minerals. It is shown that, in the ore-forming and rock-forming process, the major source of sulfur in magma, mantle-derived magma and fluid experienced component evolution resulting from magmatic crystallization and rock metasomatism, thus triggering the contamination of the crust and the mantle. Lead isotope was characterized by the subduction zone lead formed by the magma activity of the crust and the mantle, which was accompanied by the increase of the ore-bearing mantle fluid and led to the change of lead isotopic composition of the Duobuza copper deposit. Comprehensive analysis shows that the ore-forming material and the ore-forming fluid were mainly derived from the mantle, the metallogenic dynamics was mainly from deep geological process, and the formation of the ore deposits was related to mantle fluid metasomatism.

Abstract:The Wangjiazhuang copper deposit in Zouping is an important porphyry copper and molybdenum deposit in Shandong Province. It is located in Mesozoic continental volcanic basin in western Shandong. Recently, through the detailed observation under microscope, SEM and EPMA analysis, the uranium mineral and platinum group minerals (PGM) were descovered for the first time in cryptoexplosive breccia type and quartz vein type ores. They include palladium mineral A(AgPdTe₂), kotulskite[Pd(Te, Bi)], merenskyite (PdTe₂), and zeunerite[Cu(UO₂)₂(AsO₄)₂·(10~16)H₂O]. PGM generally is wrapped in aikinite with complicated composition and smaller particle size. Zeunerite is accompanied by azurite, covelline and other copper oxides in the oxidation zone. Combined with geochemical data, the authors investigated the ore-forming material sources and mechanism of migration and concentration of platinum group elements (PGE) and U, and concluded that the ore-forming materials were derived from the mantle and the formation of this deposit was related to mantle uplift, crust thinning and deep fault activity. In addition, the migration of PGE and U might have been associated with high salinity hydrothermal solution, and the precipitation conditions should be the gas loss and decomposition of the complex from severe changes of temperature and pressure caused by cryptoexplosive.

Abstract:Investigation of the structural stability and modification of carbonates under mantle conditions contribute to understanding the Earth's carbon cycle. In the present work, synchrotron radiation X-ray diffraction and Raman spectroscopy were employed to investigate the structural stability and elastic properties of single-crystal rhodochrosite in diamond anvil cell device. The results demonstrate that rhodochrosite maintains stable up to ~10 GPa and exhibits anisotropy with c-axis being more compressible than a-axis. Isothermal equation of state parameters of rhodochrosite was obtained as V₀=308.8(2)ų, K₀=104(1) GPa and K'₀=4(fixed). The symmetrical stretching band (ν₁) and in-plane vibration band (ν₂) of [CO₃]^2- were observed at 1 087.9 cm^-1 and 720.5 cm^-1, respectively, and the external (ν₃) at 293.8 cm^-1, all of which present linear positive relationships with pressure, and the external mode is more sensitive to compression. Mode Grüneisen parameters of internal mode (γ_ν1=~0.29 and γ_ν2=~0.26) are lower than that of the external mode (γ_ν3=~1.57), indicating that the bulk compression is largely due to the contraction of [MnO₆] rather than that of [CO₃]^2-. Elastic properties of calcite-type carbonates are discussed in consideration of previous reports.

Abstract:This paper aims at revealing the effect of particle size in the dissolution process of serpentine with the participation of native fungus Talaromyces flavus. Serpentine minerals of four different particle sizes were chosen for fungal leaching experiments: 150~300 μm, 100~150 μm, 75~100 μm and 45~75 μm. The pH meter, ICP-OES, FTIR, XRD and SEM were used to characterize the samples. The results show that the final dissolution rate of Mg in each group with fungus was higher than other two controls without fungus. With the decrease of serpentine particle size from 100 μm~150 μm to 100μm, the ratio of Mg increased conspicuously from 21.56% to 35.91%, and this is considered to be related to the increase of specific surface area and the strengthening of bio-leaching action. Meanwhile, the increase of ratio became inconspicuous with further decrease of particle sizes, suggesting that 100 μm is a valuable particle size for industrial application of the fungus-serpentine system. SEM images and the analysis of fungus-mineral aggregates showed that, during the process of reaction, serpentine particles were wrapped by hyphae which caused destruction of lattices and change of mineral phases. These results can provide theoretical basis and references for further industrial application of leaching serpentine by related fungus.

Abstract:In this study, the experiments employed two kinds of reduced microbial, Acidiphilumcryptum JF-5 and sulfate reducing bacteria (SRB), which can reduce Fe³⁺ and SO₄^2- in acid mining drainage (AMD) respectively. When reduction was done, they were mixed to form nano FeS, and then it was coated onto the particle limestone to improve the capability of removing arsenic through limestone permeable reactive barriers (PRBs). Batch adsorption experiments were conducted to explore the static adsorption mechanism of As(Ⅴ) and column experiments were performed for dynamic adsorption and migration of As(Ⅴ) in FeS-coated limestone. Some conclusions were reached: ① The coated biological FeS was of nanometer size and assumed crystalline form, which effectively improved the surface area of the limestone and the capacity for adsorbing arsenic. Infrared absorption spectrum showed that the main adsorption mechanism was chemical adsorption. ② The maximum adsorption amount of limestone coated with bio-nano FeS, was 187.46 μg/g, which was 30 times that of the adsorption amount of pristine limestone (6.64 μg/g). ③ The retentive capability of JF-5 and SRB coated limestone was better than that of the SRB and Fe(Ⅱ), and both of them were much better than the retentive capability of pristine limestone.