Abstract:The Miao'ershan pluton in the western segment of the Nanling Mountains is mainly composed of Caledonian granites with minor Indosinian and Yanshanian granites. The Caledonian plutons are composed of early stage biotite granodiorite, middle stage porphyritic biotite monzogranite (principal part) and late stage fine-grained biotite/two-mica monzogranite, with all the rocks having massive structure. The authors carried out U-Pb zircon dating of a porphyritic biotite monzogranite sample and a fine-grained two-mica monzogranite sample and obtained weighted average ages of 428.5±3.8 Ma and 409±4 Ma respectively, suggesting two magmatic events that occurred in the late episode of Early Silurian and in the late episode of Silurian to the early stage of Devonian respectively. Geochemically, the middle stage rock body is a high-K calc-alkaline peraluminous granitic pluton and is characterized by higher SiO₂ (70.09%～76.59%), moderate Al₂O₃ (12.71%～14.72%), higher K₂O (4.48%～5.73%) and moderate alkali (Na₂O+K₂O=7.24%～7.91%) content as well as higher ASI (1.15 on average). The granite is depleted in Ba, Nb, Sr, P and Ti but enriched in Rb, (Th+U+K), (La+Ce), Nd, (Zr+Hf+Sm)and (Y+Yb+Lu). It displays moderate total REE content (ΣREE=179.8×10^-6～270.6×10^-6), enrichment of LREE [(Ka/Yb)_N=5.07～14.33] and negative Eu anomalies (δEu=0.15～0.46). It also has slightly higher I_Sr (0.706 60～0.720 82) but lower εNd(t) (-8.29～-7.94) with Nd model ages (t_2DM) being 1.81～1.84 Ga. The C/MF-A/MF diagram indicates that the Caledonian Miao'ershan granites came from mudstones and clastic rocks. All these geochemical characteristics point to S-type granitiod and suggest that the granites might have come from rocks of middle-upper crust. Multiple oxide and trace element diagrams for discrimination of structural environment show that the granites were formed in a post-collisional tectonic setting. Based on petrogenesis and discrimination of structural environment in combination with regional tectonic evolutional setting, the authors infer that the formation mechanism of Caledonian Miao'ershan granites should be as follows: the thickening of the crust in Caledonian movement caused the rise of the crust temperature, and later weakening of stress in a post-collisional tectonic setting resulted in the melting of middle-upprer crust, with the magma emplaced in a relative open environment. These results and regional geological data indicate that there occurred strong intracontinental compression and crust thickening in Miao'ershan area in Beiliu movement as well as in Guangxi movement.

Abstract:The Miaoling gold deposit is located in the Xiong'ershan-Waifangshan area on the southern margin of the North China Craton. Zircon U-Pb LA-ICP-MS dating of the granite porphyry in the Miaoling gold deposit yielded an age of 157 Ma. Chemically, the granite porphyry is peralumious and characterized by richness of silicon and alkaline, with SiO₂ equal to 75.06%～77.66% and Na₂O+K₂O equal to 7.05%～7.39%, and deficiency of iron, magnesium and calcium. Its REE values are relatively low, being 25.74×10^-6～32.63×10^-6, and display a significant fractionation between LREES and HREES (LREE/HREE=6.74～9.53), with moderate negative anomalies of Eu (δEu=0.51～0.71). The trace elements are characterized by enrichment of large ion lithophile elements (Rb, K, Pb, and Th, U), and depletion of high-field strength elements (Nb, Ta, Ti and Ba, Sr). The whole rock Sr-Nd compositions of the granite porphyry have the data (⁸⁷Sr/⁸⁶Sr)_i=0.706 207～0.711 774 and εNd(t)=-19.0～-17.8, with Nd model ages in the range of 2.39～2.49 Ga. Plotting of lead isotopes of the granite porphyry on the ²⁰⁷Pb/²⁰⁴Pb diagrams and ²⁰⁸Pb/²⁰⁴Pb versus ²⁰⁶Pb/²⁰⁴Pb evolution curves show that the lead might have come from the crust source area. Geochemistry and Sr-Nd-Pb isotopic compositions suggest that the granite porphyry in the Miaoling gold deposit was derived from an ancient continental crust (probably the Archaean Taihua Group).

Abstract:A high-pressure granulite unit was recognized in Dulan area at the eastern end of the North Qaidam UHP metamorphic belt. The HP granulite unit comprises mafic (felsic) HP granulite, granitic gneiss, pelitic schist (gneiss), garnet amphibolite and tonalite. Based on the petrographic features and metamorphic reaction, mineral chemistry and p-t calculations, the authors divided the paragneiss into four metamorphic stages: Stage Ⅰ, which is the pre-peak prograde metamorphic stage characterized by biotite, muscovite, plagioclase and quartz inclusions within the core of zoned garnet porphyroblasts; Stage Ⅱ, the peak HP granulite-facies metamorphic stage, which is characterized by the mineral assemblage of garnet + kyanite + ternary-feldspar + plagioclase + quartz, with peak p-t conditions of t=800～840℃ and p=1.4～1.6 GPa; Stage Ⅲ, the initial decompressional retrogression began at the high amphibolite-facies stage characterized by garnet + biotite + plagioclase + quartz; Stage Ⅳ, final retrogression under gre enschist-facies conditions was deve loped at shallow crustal levels, characterized by the existence of Ms+Pl±Zo and Mrg+Qtz±Ms±Pl assemblages around kyanite. Zircon LA-ICP-MS U-Pb dating yielded peak HP granulite-facies metamorphic age of 431 Ma. The combination of petrographic textures, mineral compositions and thermobarometric data defined a single clockwise p-t path for the Dulan paragneiss, similar to that of HP mafic granulite.

Abstract:LA-ICP-MS zircon U-Pb ages and geochemical data of the Mesozoic bimodal volcanic rocks from Nenjiang in the Da Hinggan Mountains were studied in this paper. U-Pb ages of zircons show that the Mesozoic bimodal volcanic rocks were formed at the late stage of the Early Cretaceous (about 127.5 Ma). The Baiyingaolao Formation acidic volcanic rocks are composed of rhyolites and rhyolitic crystal clastic tuffs. The Meletu Formation basaltic volcanic rocks are composed of trachybasalt, basaltic andesite and basaltic trachyte. Geochemical studies suggest that the late Early Cretaceous volcanic rocks display a bimodal volcanic rock association. The Meletu volcanic rocks belong to alkaline series, have low silicon and are rich in alkalis. The chondrite-normalized REE patterns indicate that the volcanic rocks are enriched in light rare earth elements (LREE) with significant fractionation between HREE and LREE and week Eu anomalies. The trace element geochemistry is characterized by enrichment of large ionic lithophile elements (K, Rb, Ba) and depletion of high field strength elements (Nb, Ta). These characteristics indicate that the volcanic rocks originated from the remelting and fractionation of metasomatized enriched subcontinental lithospheric mantle, probably mixed with a small amount of crustal materials. The alkaline basalt series was formed under the condition of an intraplate setting, most likely continental rift. The Baiyingaolao volcanic rocks are rich in silicon and alkalis, poor in calcium and magnesium and have characteristic FeO^T/MgO ratio. The chondrite-normalized REE patterns indicate that the volcanic rocks are enriched in light rare earth elements (LREE) with significant fractionation between HREE and LREE and strong negative Eu anomalies. The trace element geochemistry is characterized by enrichment of large ionic lithophile elements (K, Rb) and LREE, and depletion of high field strength elements (Nb, Ta, P, Ti). The trace element geochemistry characteristics of rhyolites show an affinity with the A-type granite, suggesting that the volcanic rocks should have been formed in an extensional setting. These characteristics imply that the low-Sr rhyolitic magma originated from enriched mantle plume that intruded into the lower crust, and made it partially melted. The bimodal volcanic rocks were probably formed in an extensional setting. Combined with spatial and temporal distribution of the Mesozoic volcanic rocks in Northeast China, it is suggested that the formation of the late Early Cretaceous bimodal volcanic rocks might be attributed to subduction of the Paleo-Pacific plate beneath the Eurasian continent.

Abstract:A curved belt consisting of terranes or blocks and associated Late Paleozoic-Early Mesozoic sutures features the southeastern part of the Tibetan Plateau. It is the Sanjiang (Three-Rivers) multiple orogenic and ore-forming belt. In spite of numerous studies, its Paleotethyan (Late Paleozoic to Early Mesozoic) tectonic evolution remains a topic of much controversy. Recently published geochronological and geochemical data derived from modern techniques have revealed several magmatic zones with variable tectonic affinity. However, the temporal and spatial distribution pattern of the magmatic rocks didn't appear, mainly due to the absence of high quality data from some regions. As the Lanping Basin is located in the middle portion of the Sanjiang orogenic belt, the time and tectonic affinity of the volcanic rocks in this basin play a significant role in revealing the connection between the magmatic zones in the southern and northern segments of the Sanjiang belt. This study focused on the volcanic rocks exposed on the western margin of the Lanping Basin where high-quality geochronological and geochemical data are rare. The volcanic rocks in western Lanping Basin consist of andesitic tuff in the lower segment, andesite in the middle segment, and basaltic lava at the top. This volcanic sequence is developed upon the Carboniferous terrigenous clastics. The basaltic lavas are interlayered with reddish mudstone. The content of mudstone increases upwards. Geochemical data demonstrate that these volcanic rocks are of calc-alkaline or high-K calc-alkaline series, characterized by high Al₂O₃ and very low TiO₂, MnO₂, and P₂O₅ content. The andesitic samples exhibit arc-like chondrite- or primitive-mantle-normalized trace element pattern, whereas the basaltic lava displays enriched-middle-oceanic-ridge-basalt pattern. These features, combined with the field relationship, suggest that these volcanic rocks were formed in a continental arc setting. New LA-ICP-MS zircon U/Pb dating results indicate that the bottom crystal tuff was formed at 238 Ma, the andesite of the middle segment at 233 Ma, and the basaltic lava at the top of the volcanic sequence erupted at 229 Ma. These new data suggest that, at the end of the subduction, the breakup of the subducted slab might have taken place which led to the uprising of asthenosphere and induced partial melting of the enriched mantle wedge. The new data obtained by the authors have filled the spatial gap of geochronological data in the Sanjiang orogenic belt. As a result, a large scale (with a length >2 000 km) successive arc-like volcanic belt along the entire Sanjiang belt has become clear. Such a large arc-volcanic belt should be affiliated to a large-scale subduction zone (suture). Synthesizing available geological, geochemical, and geochronological data, the authors hold that the eastward or northeastward subduction of the Paleotethys along the Longmu Co-Shuanghu(-Lancangjiang)-Changning-Menglian suture probably resulted in the formation of the large-scale volcanic belt.

Abstract:The petrological and geochemical characteristics of Permian Shanxi Formation mudstones in Beijing were investigated to determine the provenance, paleoenvironment and tectonic setting of the rocks, which are mainly composed of clay minerals and quartz, with carbonate and feldspar as minor components. The carbonate content of the rocks has good correspondence with content of CaO and MgO. The SiO₂, Na₂O and K₂O are depleted whereas Al₂O₃, TiO₂ and Fe₂O₃^T are enriched, reflecting a basic source. The mudstones show homogeneous REE content, relative enrichment of LREE and depletion of HREE, with most obviously negative Eu anomalies, less or no Eu positive anomalies, and almost no Ce anomalies. The REE distribution patterns show that they have the same source rocks composed of sedimentary rock, granite and alkaline basalt from the upper continental crust of the northern margin of North China, as is also shown by the ratios of trace elements. They were deposited in a reducing environment with relatively deep water. The tectonic settings of the source area are continental island arc and active continental margin.

Abstract:Systematic sampling and geochemical analysis of the oil shale member of Dingqinghu Formation show that SiO₂ are low, K₂O/Na₂O ratios are relatively high, Al₂O₃+Fe₂O₃ are in the range of 6.43%～10.28%, and Al₂O₃/(Na₂O+K₂O) values are between 1.7 and 4.91, indicating that the oil shale contains mafic components and more stable components. Chemical indexes of alteration (CIA) are between 65 and 85, and Th/U ratios are concentrated in the range of 0.97～3.38, suggesting that the provenances of oil shale had experienced relatively moderate weathering and were in a warm and humid climate environment. Sr/Ba ratios are between 0.45 and 0.82, V/(V+Ni) ratios are between 0.46 and 0.68, and Th/U ratios have an average of 0.59, indicating that the oil shale was formed in a fresh water and anoxic lacustrine environment. Warm and humid climatic conditions, abundant biological sources, fresh water and anoxic environment were important for the formation of Lunpola oil shale.

Abstract:Eulytite is an extremely rare bismuth silicate mineral. The natural eulytite reported in this paper is attached on the geodes or cracks of tremoilite fibers produced in the Chaobuleng skarn-type iron-polymetallic deposit in Dong Ujimqin Banner of Inner Mongolia. The eulytite commonly has the forms of tetrahedron {111} and trigonal tristetrahedron, crystal size of 0.07～0.15 mm, transparent light yellow color, glass luster, brittleness and colorless streak. Its Vickers microhardness is 487～583 kg/mm² (near 5 on the Mohs hardness scale), its calculated density and N are 7.11 g/cm³ and 2.15 respectively, and its mineral chemical formula is Bi₄Si₃O₁₂. The strongest reflections in the X-ray powder diffraction pattern [d(Å)(I)] are 4.26 (85), 3.29 (100), 2.77(79), 2.11(45) and 1.67(33), and the unit cell parameters are a=10.116(2) Å, V=1 035.2(7) ų,and Z=4. The genesis of eulytite is also discussed in this paper.

Abstract:Chloritization is one of the most important alteration types in the Longshoushan uranium deposit. Based on EPMA analysis and mineralogical study of the chlorites in the Longshoushan uranium deposit, the authors found that the chemical types of chlorite in Longshoushan area is mainly mafic chlorite, with a small amount of ripidolite. Based on the genesis or the relationship with coexisting minerals of chlorite, the authors divide the chlorites into four types, i.e., biotite alteration type, feldspar alteration type, pitchblende association type and accessory mineral association type. Argillaceous rock is the main protolith of chlorite, which is the product of multi-stage geological activities. Studies show that the uranium mineralization process of the Longshoushan alkali-metasomatic type uranium deposit experienced different temperatures at different stages: At first, the hydrothermal solution was of high temperature and resulted in the chloritization of biotite, and then the metasomatism of feldspar formed chlorite of feldspar alteration type. At the mineralization stage, the hydrothermal solution was of low temperature and formed chlorite closely associated with pitchblende. In the process of uranium mineralization, chlorite not only activated uranium in the granite but also offered a favorable deposition environment.

Abstract:The mafic rock is exposed in Gaoqiao area of the North Daba Mountains. It consists of diabase, gabbro-diabase, diabase-porphyrite, and pyroxene diorite, and the minerals mainly include clinopyroxene, plagioclase, hornblende and Fe-Ti oxide. The clinopyroxene, belonging exclusively to augite, was studied in detail using microprobe in this paper. The clinopyroxene has the evolution trend from Mg-richness to Fe-richness with the variation of the rock from diabase-porphyrite through gabbro-diabase to pyroxene diorite. The clinopyroxene shows high Al^Ⅳ(Al^Ⅳ=0.02～0.20, Al^Ⅳ/Al^Tot=85%～100%), and has the feature implying that the pyroxene was formed in the undersaturated alkaline basaltic magma, which is coincident with characteristics of the alkali series, as shown by the alkaline discrimination diagram of clinopyroxene and geochemistry of mafic rock. The temperature and pressure of clinopyroxene are 1 132～1 164℃ and 0.71×10²～9.30×10² MPa respective- ly, suggesting obvious deep-derived characteristics. The electric charge unbalance caused by the replacement of Si by Al is mainly compensated by Fe³⁺, Ti mainly forms titanaugite, and Al^Ⅵ enters the octahedra to form Ca(Mg,Al^Ⅵ). Because of the isomorphism of Ca²⁺ and Na⁺, the clinopyroxene has high Ca and low Na₂O. The geological background and geochemical characteristics of clinopyroxene indicate that mafic rock in Gaoqiao area is the product of extension in a back-arc basin.

Abstract:The Huoshibulake deposit, hosted in the late Paleozoic carbonate rocks, is an important Zn-Pb deposit in southwestern Tianshan Mountains, Xinjiang. The trace elements of main ore minerals (pyrite, galena and sphalerite) and hydrothermal calcite were analyzed by ICP-MS in this study. The results show that pyrite, galena, sphalerite and calcite have similar REE characteristics, positive Eu anomalies and faint Ce anomalies, indicating that the ore-forming fluids evolved from a relatively oxidizing environment to a reduction environment. The authors compared the REE patterns of sulfides, calcite, Huoshibulake rock granite and ore-bearing wall rocks, and found that they are partly coincident with recrystallized micritic limestone. In combination with previous researches on isotope geochemistry, the authors have reached the conclusion that the Tangaitaer carbonate supplied essential metallogenic materials and ore-forming fluids. The Ga/In ratios indicate that the ore-forming temperature was low. Sulfides have light REE enrichment characteristics, with the Th/La and Nb/La ratios less than 1, suggesting Cl-richness of the ore-forming fluids. Ratios of Y/Ho, Zr/Hf and Nb/Ta varying in narrow ranges indicate that the source of the ore-forming fluid at the main metallogenic stage was simple and stable, with no addition of other fluids.

Abstract:The Xiongcun porphyry copper_gold deposit consisting of three orebodies is a newly discovered deposit in southern Tibet. The total gold resources of No. 1 and No.2 orebody amount to 246 tons, which have higher exploration extent than No. 3 orebody, with the Au concentration of No. 1 ore body being the richest. Microscope, electron microprobe analysis and simulated analysis were used to study the gold distribution and its significance. The results show that the main gold_bearing mineral is electrum. Minor or trace kustelite, sulfur_bismuth gold mineral, and gold volynskite were also been found. Gold minerals are mainly distributed inside or along the margin of chalcopyrite, and pyrrhotite, pyrite and sphalerite also contain minor gold minerals, suggesting that gold was formed at the exsolution of sulfide. Some micro_fine gold minerals are distributed within silicate minerals in the oxidized zone due to secondary enrichment process. The sizes of gold minerals are plentifully variable. The biggest gold minerals are distributed within or along the margin of chalcopyrite while the smallest ones which are mostly less than 1μm occur near silicate minerals. The modes of occurrence of gold minerals indicate that most of gold minerals are distributed along the margin of chalcopyrite. According to the experiments of Simon, gold could be infinitely miscible in metal melt at high temperature and decreased with decreasing temperature, which implies that gold could migrate outward with decreasing temperature. The existence of gold minerals in pyrrhotite, pyrite, sphalerite and gold in northwest Dongga epithermal gold deposit may be also related to the above process.

Abstract:The chemical composition of kaolin in coal measures of Jinyang, Mengxi and Xuena is SiO₂ and Al₂O₃ with low content of K, Na, Ca and Mg and relatively high content of Fe and Ti. The mineral composition is mainly kaolinite with minor boehmite, quartz and montmorillonite. The XRD and IR analytical results reveal that kaolinite in Jinyang and Mengxi exhibits a highly ordered structure with HI index being 1.19 and 1.23, while kaolin from Xuena shows dispersed and low symmetry diffraction peaks, with HI index being only 0.56. On such a basis, kaolin_dimethyl sulfoxide and kaolin_formide intercalation composite was prepared. The XRD patterns indicate that dimethyl sulfoxide and formide can insert into the inter layer of kaolinite and increase the interplanar spacing. Kaolin from Jinyang has the best intercalation ratio, kaolin from Xuena takes the second place, and kaolin from Mengxi is the worst.

Abstract:In this paper, the order of addition in the preparation of aluminum salt modified bentonite process is changed as compared with the traditional method. The expansion performance in aluminum salt modified bentonite is enhanced, and the modified bentonite is characterized by SEM, XRD, particle size distribution and FTIR and compared with the raw material Na-bentonite to deduce the mechanism of modification. Finally, the appearance is observed and the performance of adsorption is investigated. It is shown that, compared with the traditional method, the preparation of aluminum salt modified bentonite is relatively simple, and the addition order is different from that in the traditional method in that the bentonite is first mixed in water and then the modified agent is added. The modified bentonite has an efficient effect on silicate removal which can reach up to 99%.

Abstract:Cobalt in 306 coal samples from Xinjiang was determined by inductively coupled plasma mass spectrometry (ICP-MS). The Co concentrations of coal in Xinjiang are obviously higher than Co concentrations both in China and abroad, and the cobalt content of the early-Jurassic coal is much higher than that of the middle-Jurassic coal in Xinjiang. Statistics show that Co is existent predominantly in the organic binding state in coals of Kubai and Musixiang within Yili, associated mainly with inorganic matter in coals of eastern and southern Junggar, and related to organic and inorganic matters in coals of other places in Xinjiang. The concentrations of cobalt in these coals are controlled by the groundwater table in swamp and the properties of parent rocks in the source area.

Abstract:In this paper, the authors conducted detailed researches on the rarely-reported nepheline jades in the aspects of petrography, mineral chemistry, Raman spectroscopy and X-ray powder diffraction, with a discussion on their petrogenesis. The jades in this study belong to the "floating blue flower" variety and are mainly composed of jadeite, nepheline and hornblende with minor Ba-aluminosilicates, assuming a tubular texture. Jadeites in these samples have two generations: the earlier ones are euhedral and show regular oscillatory zoning, indicating iterative replenishment of diagenetic fluids during the growth of jadeites; the earlier jadeites are partly replaced by later fine-grained jadeite ± amphibole, indicating the alteration caused by later fluids. On the basis of its modes of occurrence and compositions, nepheline can be divided into two types, i.e., K-poor nepheline and K-rich nepheline, in which the former occurs along the grain boundaries of the euhedral jadeites whereas the latter fills in the space between the euhedral jadeites. The textural features indicate that the nepheline jades were directly precipitated from fluids. The mineral assemblage and compositions suggest that the fluids were rich in Na, Al, Si, K, Ba with small amounts of such major elements as Ca, Fe and Mg, while the trace elements are characterized by enrichment of LREE, HFSE, Sr, etc. Combining the phase relations between the minerals in the samples with the results from previous studies, the authors hold that the crystallization p-t conditions for the jadeites should be confined to 6～14 GPa and 300～450℃. The nepheline in the jades represents the precipitation product of fluids after decompression.

Abstract:The study of geological fluids is a focus of earth science. The compositions of fluid inclusions are the key to understanding the geological fluids. In traditional methods, the anions of liquid ingredients are detected by single-channel ion chromatography, and the cations of liquid ingredients are detected by AAS or ICP-AES. The traditional methods can only analyze a few mineral species and requires a larger amount of mineral (over 3 g). The dual-channel ion chromatography was used in this study. After a number of condition experiments, the authors optimized the pre-treatment analysis method (such as burst and extraction), and identified the detectable ions in different minerals. The weight of the sample was reduced from 3 g to 300 mg by using the concentration method. Quartz, calcite, fluorite, sphalerite, garnet, magnetite and pyrite were analyzed for their liquid phase compositions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, F^-, Cl^-, Br^-, NO₂^-, NO₃^- and SO₄^2-). The new ion chromatographic analysis method established by the authors is characterized by such advantages as simple operation, rapidness, low cost, and requirement of only a small weight of sample, thus expanding the scope of analysis of mineral species. In addition, this method can provide more direct and effective information for the study of ore-forming fluids.