Abstract:The Late Silurian to Early Devonian potassic alkaline rocks on the northern margin of the North China Craton (NCC) is a key geological unit to understand the interaction processes of the Paleo-Asian Ocean and the NCC in the Paleozoic. In this paper, we report new zircon U-Pb age, mineral chemistry, whole-rock geochemistry and Sr-Nd isotopic compositions from the Late Silurian potassic Huangheshao (HHS) syenties on the northern margin of the NCC, and discuss its petrogenesis. Sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb dating has revealed a crystallization age of 417.6±4.7 Ma for the HHS pluton. Alkali-feldspar syenite is the main rock type; Aegirine-augite and sanidine (An₀Ab_2~5Or_95~98) are the major minerals, with subordinate albite (An₀Ab_95~100Or_0~5). Aegirine-augites locally transferred into winchite or magnesio-riebeckite. The HHS syenites have high total alkali contents (Na₂O+K₂O=12.79%~15.30%),high Rittmann index (σ=8.48~11.09), high K₂O contents (8.66%~13.78%), and high K₂O/Na₂O ratios (2.10~9.07), suggesting their alkaline, potassic-ultrapotassic affinity. High Sr abundances and radiogenic Sr isotopic compositions (initial ⁸⁷Sr/⁸⁶Sr=0.704 1~0.706 1) argue for an enriched subcontinental lithospheric mantle (SCLM) source for the HHS magmas,which was previously metasomatized by melts/fluids from the subducted sediments on the down-going oceanic crust. The development of the Late Silurian to Early Devonian potassic alkaline rocks on the northern margin of the NCC indicates that the Paleo-Asian oceanic slab had subducted beneath the NCC in the Early Pleozoic, and the subducted materials metasomatised the SCLM, forming a phlogopite/K-amphibole-bearing, fertile mantle source. During the end of the Late Silurian to Early Devonian, due to the accretion or collision of a microcontinent, the northern margin the NCC has entered into a temporary, post-collisional extension tectonic setting.

Abstract:This paper studies the formation age and geochemical characteristics of the volcanic rocks of the Manketouebo Formation in the Horqin Right-Front Banner area, Inner Mongolia. The LA-ICP-MS zircon U-Pb dating of two typical rhyolite samples reveals that the eruption occurred in the Late Jurassic (145.9±1.0 Ma and 146.0±1.3 Ma, respectively). The volcanic rocks of the Manketouebo Formation in the study area belong to the peraluminous, high-potassium calcium-alkaline series, with high SiO₂ (63.28%~77.40%, with average of 71.06%) and total alkalis (7.52%~10.14%, with average of 8.66%). The trace element patterns are characterized by enrichment of large ion lithophile elements (e.g., Rb, K) and depletion of high field strength elements (e.g., Nb, Ta, Ti, P), showing the typical characteristics of crust-derived magma. The rhyolite and trachyte in Manketouebo Formation have a good evolution trend in the major and trace elements. It is speculated that the crust-derived material was partially melted and erupted after different degrees of fractional crystallization. Besides, the volcanic rocks have similar geochemical characteristics of post-orogenic magmatism. Combined with the temporal and spatial distribution that the ages of the Manketouebo Formation in the Da Hinggan Mountains increase from southwest to northeast, it is proposed that the volcanism of this period is closely related to the post-orogenic extension after closure of the Mongol-Okhotsk Ocean.

Abstract:The Mesozoic granites, especially Late Jurassic, are widely distributed in Jiaobei terrane. To further understanding the formation age, genesis and geodynamic background of these granites has great significance to the crustal evolution of study area. In this paper, the major and trace elements, zircon U-Pb ages and O isotopes of the Jurassic granites in the eastern and northern Jiaobei terrane are reported. The results show that the zircon U-Pb ages of the granites studied in this paper are mainly distributed between 166 Ma and 156 Ma, representing the crystallization age of the granites. In addition, there are a large number of inherited zircons with age peaks of 3 650~3 294 Ma, 2 660~2 445 Ma, 770~600 Ma and 245~197 Ma. These granites shown adakite-like geochemical characteristics. The formation ages and geochemical characteristics of Jurassic granites in this study are similar to those of Linglong and Luanjiahe Jurassic granites from western Jiaobei terrane, indicating a similar source from partial melting of thickened continental lower crust. Furthermore, based on the variation of the U-Pb age and O isotope of inherited zircons from different samples, we concluded that the Jurassic granites in Jiaobei terrane have multiple sources, some of them derived from the thickened continental lower crust in Jiaobei terrane and the others from subducted Yangtze block. Then, the subduction of Paleo-Pacific or Izanagi plate might play a direct or indirect role in causing the partial melting of the thickened continental lower crust.

Abstract:The Jiangnan Orogen in Hunan is an important gold metallogenic belt. There are debates about the gold ore-forming ages and geological settings of the belt. According to the ages of magmatic rocks and deposits, as well as geological charateristics of deposits, metallogeny and ore-forming fluids and regional tectonic evolutions, the authors analysed the metallogenic ages of every major ore concentration area in the Jiangnan Orogen in Hunan, and then defined the gold mineralization events and their ages, probed into the tectonic settings of the events. The following preliminary ideas are put forward. There occurred mainly three gold mineralization events in Jiangnan Orogen such as Caledonian, late Indosinian and Yanshanian. The Caledonian gold deposits with ore-forming age of 430~410 Ma (late Silurian) were located in the three areas, such as the middle-southwestern segment of Xuefeng thrust-fault zone, the eastern segment of Xuefeng thrust-fault zone, and northeastern Central-Southeastern Hunan tectonomagmatic belt in the same time, with ore-bearing strata Banxi Group, Lengjiaxi Group and Lengjiaxi Group respectively. Gold mineralization in the first two areas was related with metamorphism, deformations and structural activation caused by Caledonian Movement, while in the last area was related with the thermal energy and hydrotherm provided by late Silurian granitic magmatism. The late Indosinian gold deposits with ore-forming age of 227~202 Ma (Late Triassic) took place mainly in southeastern Xuefeng tectonomagmatic uplift zone in Indosinian, and were related with the thermal energy and hydrotherm caused by post-collisional granitic magmatism. The Yanshanian gold deposits with ore-forming age of 152~130 Ma (Late Jurassic-initial Early Cretaceous) were mainly took place in east part of southeastern Xuefeng tectonomagmatic uplift zone in the same time, and were related with the granitic magmatism in extensional environment.

Abstract:The Pucheng district is located in Wuyi metallogenic belt, which is in the northern part of the northwest Fujian uplift zone, consisting of more than 30 fluorite mines (mineralization spots). We take Waiyang fluorite mine, Nanshanjian fluorite mine, Lichu fluorite mine, Longtouyang fluorite mine and Renfeng mineralization spot as the main research examples in this study. The geochemical analysis of fluorite and monzonitic granite hosting rocks were carried out. The fluorite ore has massive, banded, vein-like structure. It mainly includes fluorite-type ore and quartz-fluorite type ore. The ΣREE content of fluorite ranges from 12.22×10^-6 to 154.44×10^-6, the Y content is between 5.68×10^-6 and 114.90×10^-6, the ratio of LREE/HREE in fluorite ranges from 1.10 to 4.67, (La/Yb)_N ratio ranges from 0.85 to 5.04, δEu ratio ranges from 0.55 to 1.05, and δCe ratio ranges from 0.73 to 0.95. The ΣREE content of monzonitic granite ranges from 74.13×10^-6 to 340.42×10^-6, the Y content ranges from 15.37×10^-6 to 90.49×10^-6, LREE/HREE ratio in hosting rock ranges from 1.54 to 15.47, (La/Yb)_N ratio ranges from 0.85 to 42.51, δEu ratio ranges from 0.10 to 0.72, and the δCe ratio ranges from 0.36 to 1.64. The monzonitic granite is peraluminous with high-potassium calc-alkaline characteristic, and is enriched in large ionic lithophilic elements (Rb) and high field strength elements (U and Th), and depleted in high field strength elements (Zr). The REE normalized pattern shows a gentle right curve, and plots into plate granite (WPA). I-type granite has a strong relationship with the fluorite mineralization. Monzonitic granite is enriched in F, which is the main source of fluorite mineralization. The fluorite in the study area was formed in a hydrothermally-generating low-temperature reduction environment. The fluorite deposit occurred in the NE trending fault zone, which also has undergone at least two phases of fluorite mineralization.

Abstract:The magmatic system of large silicic volcanic eruptions (with ejected volumes of about 10²~10⁴ km³) extends through the crust, comprising complex generation, transport, storage, recharge and eruption processes. Critical aspect for understanding the evolution of silicic volcanic system is to reveal the magmatic processes from melt generation to eruption, such as crystal fractionation, crystal accumulation, crystal-melt segregation, crustal assimilation, magma recharge and mush rejuvenation. Zircon incorporates a variety of trace elements, such as Th, U, Ti, Hf and rare earth elements, and their abundances and variations are particularly sensitive to the composition, temperature, oxidation state, water content of the magma and the co-crystallized phases. Therefore, zircon has the outstanding capacity to record the evolution of silicic magmatic system. In general, as the falling temperature of the melt, the Hf concentration increases and the Ti concentration and Th/U, Eu/Eu^* and Zr/Hf ratios typically decreases, which are effective indicators of fractionated magmas. Zircon from porphyry intrusions associated with mineral deposits tends to have high Ce⁴⁺/Ce³⁺ and Eu/Eu^* ratios, indicating strong oxidized conditions and high water concentration. Zircon can show characteristics of multistage crystallization with a core-rim structure, including distinctly resorbed core and CL-bright rim. Compared to the zircon core, CL-bright rim commonly shows lower Hf and U and higher Ti and Eu/Eu^* ratios, indicating magma recharge event and the rejuvenation of crystal mush. Due to the mobility of smaller zircon relative to the larger crystals, zircon may continuously be mobilized in extracting melts recording a continuous compositional range of magma evolution, but may also remain in the crystal mushes indicating crystal-melt segregation events. Zircon trace element compositions integrated by high-precision zircon U-Pb geochronology can track the evolution of silicic volcanic system as a function of time. Metamictization, sector zoning and exotic mineral inclusions should be considered to screen magmatic trace element signatures and interpret the zircon trace element data. Careful examination of thin sections of rock to find zircon occurring and associated minerals is also important to track the multiple evolution of silicic volcanic system.

Abstract:As a link between the earth's surface and its deep interior, the subduction zone is the primary tool to bring surface carbon into the deep earth and the principal place to exchange surface and in-depth materials. Subduction can bring surface carbon into the deep earth in organic carbon or inorganic carbonate minerals and then return to the surface system through volcanism or degassing. The deep carbon cycle in the subduction zone controls the surface carbon flux, which is of great significance for studying global climate change and the earth's habitability. This paper discusses the mechanism of carbonation and decarbonation in the subduction zone. The decarbonation mechanism includes decarbonizing metamorphic reaction, carbon dissolution, and melting decarbonizing. Carbon bearing fluids released from the subducting plate may not always migrate back to the surface. Some of them will react with the surrounding rocks (carbonation) to form other solid carbon phases (carbonate, graphite, or diamond), sequestrated in the subducting plate and overlying mantle wedge. This process will affect the carbon fluxes in different reservoirs and should be considered when the carbon flux released from the subduction zone is calculated.

Abstract:Tufa has a scientific research value. There are wide distributions of the tufa mounds in the north, middle and southwest of Searles Lake, California, USA. The tufa mounds range from a few centimeters to 45 m in height, and most are 5 to 12 m high. There are four tufa facies can be identified from the mounds, including porous spongy tufa facies, nodular tufa facies, columnar tufa facies and finely-laminated crusts tufa facies. In terms of tempo-spatial distribution, there are two sequences of tufa deposition, including porous spongy tufa facies to nodular tufa facies to finely-laminated crusts tufa facies to porous spongy tufa facies and porous spongy tufa facies to columnar tufa facies to finely-laminated crusts tufa facies to porous spongy tufa facies. These tufa mounds mainly consist of calcite and aragonite. On the microscopic scale, these tufa facies dominantly make up nano-shperes and rod-like crystals, interpreted to be the activities of microorganism, such as bacterial. The values of δ¹³C in the tufa facies were measured, and the results were positive, proving that the tufa of Searles Lake is the thermogene tufa. The discussion on the main sedimentary types and genesis of tufa in Searles Lake can provide comparative reference for the study of tufa in China.

Abstract:Following the discovery of Luodian nephrite and Dahua nephrite, another nephrite mineral spot was also found in Bama, Guangxi, which also belongs to Qian-Gui area. Analysis methods, such as orthogonal polarization microscope, X-ray powder diffraction, electron probe microanalysis and artificial heavy concentrate, were employed to study petrographic characteristics, mineral composition, color-forming factors and the genesis. These studies show that the main mineral composition of Bama nephrite is microcrystalline tremolite or actinolite, and other minor minerals, such as talc, limonite, kaolinite, etc. Bama nephrite shows felty structure,bundle structure and structure of the pattern of aquatic plant. Spots of Mg/(Mg+Fe²⁺)-Si of Bama nephrite plot into tremolite or actinolite. The hardness of Bama nephrite is between 5.19~5.32, the denstity is between 2.81~3.00 g/cm³, the refractive index is about 1.61. Talc, auxiliary mineral of Bama nephrite, is the cause of lower hardness. According to the electron probe data, the relevant chemical formulas of Bama jade were calculated and compared and analyzed, we found that the green color of Bama nephrite is related to 0.08~0.67 a.p.f.u of Fe in C site in tremolite, which suggests that the increasing content of Fe in C site in Bama nephrite leads to change of the colors of nephrite from light purple to dark green. The data of X-ray powder diffraction show that goethite was in the structure of the pattern of aquatic plant, implying that the structure of the pattern of aquatic plant of Bama nephrite was formed on the surface of the earth. Through field observation, the comprehensively analysis of major elements, rare elements and rare earth elements, and comparison with related features of other mine point, the authors consider that the genetic type of Bama nephrite deposit is belongs to stratabound and contact metasomatic magmatic hydrothermal deposit, which is result-ed from the magmatic hydrothermal contact metasomatism induced by diabase intruding into carbonate rock. Bama nephrite is the same genetic type with Luodian and Dahua nephrite deposits in Qian-Gui area which have been found in previous study. They are belong to the same ore belt.

Abstract:Soil pollution by heavy metal has been gradually serious in facility agriculture. Due to the interaction of soil minerals, organic matter and microorganisms at natural condition, the combination mechanism between soil single component and heavy metal couldn't represent the reality of the translocation and transformation of heavy metal in the soil. In this research, mechanical mixture of montmorillonite and kaolinite (Mont:Kao=1:1), Gram-positive(Bacillus subtilis, B.s) and Gram-negative (Pseudomonas putida, P.p), and humic acid (HA) were selected as phyllosilicates mineral in vegetable greenhouse and farmland soil, organic matter and bacteria respectively. Cd²⁺ and Cu²⁺ were taken as the target compounds. The adsorption mechanism and interaction on the binding of Cd²⁺ and Cu²⁺ by the ternary composites of Mont/Kao-HA-bacteria were investigated by macroscopy sorption together with XRD, ATR-FTIR and SEM. The experimental results showed that heavy metal ions had the additivity of sorption on Mont/Kao-HA or Mont/Kao-bacteria system, while the antagonism between heavy metal ions and the ternary Mont/Kao-HA-bacteria system. The kinetics data of Cu²⁺ adsorption on mesoporous goethite fitted well the pseudo-second-order equation. The maximum Cu²⁺ adsorption capacities followed the order:B.s > P.p > Mont/Kao-B.s > Mont/Kao-P.p > Mont/Kao-HA-P.p > Mont/Kao-HA > Mont/Kao.

Abstract:The typical characteristics of Sichuan Basin atmosphere are high humidity and weak mobility, where haze is easily formed during the winter and spring seasons. Here, the interactions system of quartz and calcite nanoparticles with toluene and Cr³⁺ in low temperature and high humidity conditions were systematically investigated. Based on the changes in the Zeta potential, colloid size and aggregated morphology, hydrophilic and hydrophobic properties after the quartz and calcite particles coupling with toluene and Cr³⁺, we modeled that:① Since a significant inter-coupling effect between the toluene and Cr³⁺ with quartz and calcite, the presence of toluene and Cr³⁺ can greatly reduce the Zeta potential of quartz and calcite particles in high humidity environment, and results in the instability of quartz and calcite particles at low temperature; ② By its electrostatic force, Cr³⁺ can promote quartz and calcite particles to form agglomerated colloids with larger particle size in high humidity environment; ③ Toluene adsorbed on quartz and calcite particles can enhance their hydrophobicity, and thus weaken the disturbance of water on the stability of quartz or calcite particles-based colloids. The aforementioned findings could provide positive enlightening significance for understanding the mechanism of haze formation in Sichuan Basin from the angle of the inter-coupling of quartz and calcite particles with toluene and Cr³⁺.

Abstract:The Ashele Cu-Zn deposit in Xinjiang is a typical volcanic massive sulfide deposit. In recent years, mineral exploration has been extended to the depth and the periphery. The traditional geophysical and geochemical exploration methods are not effective in mineral exploration as the small thickness and large buried depth of the orebody. It is urgent to find a quick and effective mineral exploration method. This paper introduces the application of short wave infrared (SWIR) technique in the exploration of the Ashele Cu-Zn deposit. The results show that the muscovite closely related to orebody or mineralization has an Al—OH absorption peak position of less than 2 205 nm and is characterized by Al-rich; and that the chlorite closely related to orebody or mineralization has Fe—OH absorption peaks concentrating at 2 250 nm and shows Mg-rich characteristics. The crystallinity of muscovite increases gradually from the south to north, indicating that the hydrothermal fluid (mineralization center) was mainly from the north. The SWIR can identify the alteration minerals quickly and effectively, which is useful to determine the alteration mineral assemblages and reveal the regularity of alteration zoning. The wavelength of absorption peak of muscovite and chlorite and crystallinity of muscovite can be used as new prospecting symbols of the Ashele Cu-Zn deposit.