Abstract:The Yiwulüshan metamorphic core complex (MCC) within the northern margin of the North China Craton is a typical representative of large-scale Mesozoic extensional deformation in Northeast Asia continent. Many studies including the fabric characteristics, shear-sense indicators, strain, kinematic vorticity and deformation age have been intensively conducted. However, some problems concerning geochemistry, isotopic characteristics and genesis of the granite within the core of this MCC remain unanswered. The granite of the core within the MCC is composed of biotite monzogranite and granodiorite. Based on previous research, together with the major elements,trace elements and Sr-Nd isotopic data, the paper presents the results of the data and discusses the genesis and geological significance. According to the results obtained, the granite of Yiwulüshan MCC granite is characterized by high silicon and alkali content (SiO₂ =61.17%~75.21%, K₂O+ Na₂O=7.34%~9.03%), thus belonging to metaluminous and peraluminous (A/CNK=0.96~1.08) and can be assigned to genetic type of high-k-calc-alkaline series, suggesting characteristics of I type granites; most granites have weak negative Eu anomaly (δEu=0.71~1.63), enrichment of large ion lithophile elements (e. g., Rb, Ba and Sr) and light rare earth elements, depletion of high field strength elements (e. g., Nb,Ta and Ti) and heavy rare earth elements, high Sr (308×10^-6~1 414×10^-6, averaging 709×10^-6), low Y (3.17×10^-6~13.30×10^-6, averaging 7.86×10^-6) and Yb (0.45×10^-6~1.32×10^-6, averaging 0.78×10^-6), showing the characteristics of adakitic rocks; isotopic data show that the early co-emplacement granites have a wide range of (⁸⁷Sr/⁸⁶Sr)_i values (0.695 966 ~ 0.707 869) and a lower εNd(t) values (-21.72~-18.32) and were derived from ancient crust and attributed to the partial melting of the thickened lower crust under the background of regional extension; the isotopic data of the later post-emplacement granites range from 0.705 909 to 0.706 774, and have negative εNd(t) values (-20.60~-16.99), which indicates that the post-emplacement granite resulted from the North China Craton extension thinning during the Late Mesozoic.

Abstract:The petrogenesis of high Ti basalts is a hot issue in the study of the Emeishan large igneous province (ELIP). Due to the spatial differences in geochemical characteristics of high Ti basalts, there is no consensus on the petrogenesis. In this paper, the authors systematically collected geochemical data of high Ti basalts and CA-ID-TIMS U-Pb dating results of zircons in the ELIP, respectively, and subsequently carried out integrated data processing, analysis and simulation. The research results show that the ELIP was formed in 259~258 Ma and the Emeishan high Ti basalts are distributed all over the ELIP. From west to east, the age of rocks shows no remarkable change, and the distribution of rocks changes from thick to thin. The high Ti basalts with little crustal contamination originated from mantle plume with the characteristics of enriched mantle. They experienced a low degree of partial melting with the possibility of the mixture of some lithospheric mantle components, and fractional crystallization was dominated by clinopyroxene. There was an asymmetric mantle plume at the depth of the ELIP. From west to east, the original depth and temperature of high Ti basaltic magma decreased, the melting depth and pressure decreased, resulting in the increase in melting degree. Simulation shows that the melting degree of garnet phase and spinel phase in the source area is 0.5%~2% and 5% respectively, the melting ratio of garnet phase decreases from 90% to 40% and that of spinel phase increases from 10% to 60% from west to east.

Abstract:The Gejiu alkaline complex is composed of alkaline feldspar syenite in border facies and nepheline syenite in central facies. The whole-rock geochemical analysis shows that the alkaline complex has the characteristics of high alkalinity, rich potassium, rich iron, low magnesium, and highly differentiated alkaline-peralkaline rocks, with the late stage more enriched in alkali metal elements. LREE/HREE=20~59, (La/Sm)_N=8~50, and (Sm/Yb)_N=1.2~5.0. It is rich in light rare earth elements. The fractionation degree of the light rare earth elements is higher than that of the heavier rare earth elements. It has Eu negative anomaly. The Gejiu alkaline complex is depleted in such elements as Ti, Nb, P, K, and Sr, and rich in such elements as Zr, Hf, Th, La, Ce, Nd, U and Rb. All these characteristics indicate that the magma source is related to mantle derived materials. Alkali syenite and nepheline syenite have similar characteristics of trace elements and rare earth elements, and have the characteristics of homologous magmatic differentiation and evolution. The ratios of Rb/Sr, Nb/Ta, and Zr/Hf are all higher than or close to the corresponding values of the original mantle. CIPW standard mineral calculations show that perilla pyroxene, cone pyroxene, and olivine appear in the alkali syenite in marginal facies. Olivine appears in the nepheline syenite in central facies. Combined with the characteristics of the ratios of (Th/Nb)_N and Nb/La and the research results of previous Sr-Nd isotope, it is considered that the magma of Gejiu alkaline complex was derived from partial melting of enriched mantle subjected to metasomatism and limited crustal contamination, which was formed in the extensional environment of the post-collision. In the late period of alkaline magama evolution, alkali was richer, and the higher degree of crystallization differentiation constituted an important factor for the abnormal enrichment of REE, Nb, Ga and Zr.

Abstract:The highly fractionated high-silica rhyolite is a potential host of the rare earth elements (REE) deposits. The Tarim large igneous province (T-LIP) is characterized by a high proportion of felsic rocks; nevertheless, the potential capacity of the REE mineralization remains unclear. In this study, ignimbrite from well S42 in Northern Tarim Uplift was studied, and several Fe-P-REE enriched mineral assemblages were recognized: ① the lithoclast consisting of quartz rim and magnetite+monazite+alkali feldspar core; ② the magnetite+monazite+rutile+apatite in the groundmass; ③ the monazite+pyrite in the quartz phenocryst. Further analysis of quartz SIMS oxygen isotopes in situ showed that the δ¹⁸O_V-SMOW values of lithic quartz range from 11.15‰ to 14.60‰, while those of the quartz phenocrysts are from 7.23‰ to 7.84‰, consistent with the bulk-rock oxygenic composition (5.00‰~7.21‰). A titanium thermometer of quartz shows that the formation temperature of quartz phenocryst was 756~815℃, and that of lithic quartz was 566~645℃. In addition, trace elemental compositions of magnetite associated with quartz in the lithoclast also show consistency with those of the hydrothermal origin. The above evidence indicates that the Fe-P-REE mineral assemblage in the lithoclast was derived from the late hydrothermal fluids. On the other hand, the occurrence of Fe-P-REE mineral aggregates in the groundmass of the ignimbrite and quartz phenocryst indicates that REE were sufficiently concentrated in magma and then REE minerals were crystallized in the late stage of evolution. Therefore, the Fe-P-REE enriched mineral aggregates in the ignimbrite were mainly related to the magmatic fractional crystallization and the late hydrothermal fluids. Their recognition provides an important implication for the REE mineralization of felsic rocks in the T-LIP.

Abstract:The India-Eurasia collision led to the formation of an orthogonal collisional belt and an oblique collisional belt, which are the Tibet-Himalaya and the Sanjiang orogenic belts, respectively, and are now separated by the east Himalaya syntax. The Eocene Jianchuan basin is located in the southernmost region of the oblique collisional belt. Detailed sedimentary study of four profiles along the western margin of the Jianchuan basin revealed two stages of the basin infilling process, which were separated by the 37～34 Ma potassic volcanism. The earlier stage infillings were sourced from the southwest, and displayed upper and middle fan, and/then delta plain facies. The later stage infillings were derived from the northwest regions of the basin, which formed upper fan facies. Combined with the Eocene structures of the basin's basement, the authors hold that the Jianchuan basin is an Eocene foreland one. The Eocene Jianchuan foreland basin, along with its numerous equivalents in eastern and central Tibet, likely was previously located in the orthogonal collisional belt. The boundary between the orthogonal and oblique collisional belts might have been located in the south of the Jianchuan basin during the Eocene. The changes in tectonic location of the Jianchuan foreland basin indicate the successive northward growth of the oblique collisional belt due to the continuous northward indenting of the India continent into Eurasia.

Abstract:A set of meta-argillaceous rocks mainly composed of biotite plagioclase gneiss have been newly discovered in Caojian, Yunlong County, western Yunnan Province, which are existent in the form of structural lenses, with small outcrops and well-developed medium-high metamorphic minerals, which is obviously different from the feature of surrounding rocks. Petrographic study shows that gneiss has obvious mineralogical records of subduction-exhumation, and there is also a paragenetic mineral assemblage of kyanite+aluminum amphibole, and the corresponding metamorphic pressure should have reached 1.0 GPa or higher. The metamorphic temperature and pressure of rocks calculated by GBP average temperature and pressure meter method are 566~623℃ and 0.36~0.53 GPa respectively. In addition, there is a small amount of siliceous muscovite minerals in gneiss. According to the p-T visual profile of phase equilibrium simulation and the characteristics of its maximum silicon atomic weight of 3.23, it is inferred that the rock belongs to blueschist. According to the comprehensive study, the biotite plagioclase gneiss belongs to high-pressure metamorphic rocks (the minimum metamorphic pressure in peak period is about 1.60 GPa), and these data provide new information in search for high-pressure metamorphic rocks in the northern part of Changning-Menglian junction zone, and also show that Changning-Menglian junction zone is a continuous high-pressure and ultrahigh-pressure metamorphic zone.

Abstract:Scanning electron microscope, X-ray spectroscopy,XRD, MLA mineral detection software were used to study the material composition, modes of occurrence, embedded properties, particle size and dissociation characteristics of a copper mine. The results show that the main valuable metal in the ore is copper, possessing 1.05%, which mainly occurs in chalcopyrite, bornite, chalcocit and malachite. The gangue minerals mainly include quartz and feldspar, followed by calcite and chlorite. The grain size of the main minerals is less than 20 μm, and the metal content of -9.6 μm is 0.3%. The degree of liberation is low. Moreover, the main copper minerals have close association with gangue minerals, reaching more than 40%. It is difficult to achieve a good economic index only by flotation. Based on the results of process mineralogy research, the authors adopted one roughing process- two cleaning processes- two scavenging flotation intensification processes to carry out closed-circuit test for part of the scheme of centralized treatment of middle ore. The copper grade and recovery of copper concentrate are 19.12% and 79.16%.

Abstract:Graphitic carbon is mainly transformed from organic compounds or carbonate minerals in nature, and can exist stablly in sedimentary rocks, magmatic rocks and metamorphic rocks. With the development of research on the carbon cycle in subduction zones, graphitic carbon, which usually occurs as accessory mineral in metamorphic rocks, has increasingly attracted attention. Graphitic carbon can be stable in subduction zones as carbon sinks due to its low solubility with respect to carbonate and the low mobility with respect to carbonic fluids. However, graphitic carbon can be reactive under some special geological conditions (e.g., with the presence of aqueous fluids in open systems), and becomes active and migrates. Therefore, graphitic carbon is one of the key subjects to trace carbon cycle in subduction zones. Based on previous studies, this paper provides an overview of the properties, formation, and decomposition of graphitic carbon in subduction zones, and comprehensively discusses the abiotic genesis, the stability and the release of them, which can be a key participant in the carbon cycle in subduction zones. There are three main genetics mechanisms of graphitic carbon in subduction zones: graphitization of biological organic matter, precipitation of saturated carbonic fluid, and reduction of carbonate minerals. Graphitic carbon in subduction zones can be released through degassing and fluid-mediated dissolution. Subduction and weathering erosion are the two main processes in the global cycle of graphitic carbon, with subduction having a greater impact on the internal circulation of graphitic carbon.

Abstract:During the service of the high-level radioactive waste repository, low-carbon steel serves as a candidate metal material for the disposal tank, but iron corrosion products infiltrate into the buffer barrier, resulting in mineral phase transformation and performance variation, which threatens the long-term safety and stability of the multiple barrier system. This paper reviews the chemical and low-medium temperature field in the deep reduction environment of the repositories. It is believed that the above factors can cause the release of Fe²⁺ in the disposal tank. Fe²⁺ causes montmorillonite mineral phase transformation: Fe²⁺ replaces Al³⁺ and Mg²⁺ in the octahedral lattice of montmorillonite, reduces Fe³⁺ or directly occupies the vacancy to generate secondary minerals; Fe²⁺ exchanges Na⁺, K⁺ and Ca²⁺, converted to iron-based montmorillonite. Mineral phase transition can induce buffer barrier performance variation or even degradation. Based on the concept of "resisting mineral transformation", the research direction of the mineral phase transformation of the buffer material in the next stage is proposed, which provides a scientific basis for the selection of carbon steel in underground laboratories, the design of the verification test of the buffer barrier and the safety evaluation of the barrier system.

Abstract:The low molecular organic sodium commonly existed in the environment can affect the biomineralized products (schwertmannite and jarosite) of Acidithiobacillus ferrooxidans (A. ferrooxidans), which can lead to changes in the migration and transformation of toxic heavy metals in the environment. This paper discussed the influence of low molecular organic sodium salts on the bacterially metabolized iron minerals during the growth process of A. ferrooxidans HX3, and also characterized and analyzed the iron minerals by XRD, FTIR, FESEM and EDS. The study results showed that the addition of low molecular organic sodium salts at the lower concentrations had unobvious effects on the Fe²⁺ oxidation, but it could accelerate the formation of jarosite. Addition of sodium malate was conducive to the transformation of schwertmannite to jarosite, compared with addition of sodium citrate or sodium oxalate. Addition of the low molecular organic sodium salts at the higher concentration (i.e. 20, 40 and 40 mmol/L for sodium malate, sodium citrate and sodium oxalate, respectively) inhibited the oxidation of Fe²⁺ during bacterial cultivation process. The sequence of inhibitory effects from large to small was following: sodium malate>sodium citrate>sodium oxalate. These results could provide a theoretical reference for the formation and transformation of iron minerals in acid mine wastewater containing iron bacteria such as A. ferrooxidans, and their biomineralization mechanism.

Abstract:To explore the stabilization effect of palygorskite activated by different concentrations of H₂SO₄ solution on Cd in soil, the authors carried out acid activation of palygorskite by using H₂SO₄ solutions with concentrations of 5%, 7.5%, 10%, 12.5% and 15%, respectively. Stabilization experiments and pot experiments were carried out with the addition of Cd contaminated soil. The results showed that the active Cd content of soil was significantly reduced by applying palygorskite activated by different concentrations of H₂SO₄ solution, and that the stabilization effect of 10% H₂SO₄ activated palygorskite was the most significant. The extracted Cd content of toxic leaching (TCLP) and diethylene triamine pentacetic acid (DTPA) decreased by 31.11% and 37.33%, respectively. The results of continuous extraction by the European Community Reference Agency (BCR) showed that palygorskite modified by acid can significantly reduce the content of acid-soluble state and reduction state of Cd in soil. The palygorskite modified by acid could significantly inhibit the absorption of Cd in soil and the transfer of underground part to the aboveground part. The content of Cd in the surface part of maize decreased by 26.99%~43.97% compared with the control group, and the content of Cd in the underground part of maize decreased by 15.36%~27.40% compared with the control group. Palygorskite modified by acid has obvious stabilization effect on Cd in soil.

Abstract:In order to study the heterogeneous oxidation mechanism of SO₂ on γ-Al₂O₃ (110) surface by HONO, the authors calculated the adsorption and oxidation mechanism of SO₂ and HONO on γ-Al₂O₃ (110) surface by the first principles based on density functional theory (DFT). The results showed that SO₂ was adsorbed on the perfect/defect γ-Al₂O₃ (110) surface in the form of molecules, while HONO existed only on the perfect surface in the form of molecules. The existence of oxygen vacancies on the surface not only enhanced the adsorption strength of SO₂ and HONO, but also induced the decomposition of HONO on the oxygen defect surface (HONO→NO + ·OH). The analysis of partial density of states (PDOS) and Mulliken charge distribution showed that the decomposition of HONO follows the Haber-Weiss mechanism. It is found that SO₂ and HONO were adsorbed on the oxygen defect surface, and the OH radicals generated by HONO decomposition oxidized SO₂ to form HOSO₂ cluster molecules. This study not only helps to understand the role of HONO in the oxidation of SO₂ on the surface of mineral oxides, but also provides a theoretical basis for explaining the formation of atmospheric sulfate aerosols.

Abstract:Based on the fact that multi-stage fluid activities play an important role in the interaction between jadeitite and symplectitic coronas, the authors focused on the study of the composition and the mode of occurrence of water in the symplectitic coronas of amphibole + chromite jadeite + jadeite in Myanmar amphibolite jadeitite from the micro scale point of view. The results show that the fluid composition involved in the formation of symplectitic coronas is complex and the formation process is of multi-stage. The paragenetic minerals of symplectitic coronas are different, the chemical composition zone of amphibole+ chromite jadeite + jadeite is widely developed in amphibolite jadeitite. In addition, the structural hydroxyl content of amphibole is more uniform in the core of symplectitic coronas, and from the edge of chromite jadeite to jadeite the structural hydroxyl content increases regularly. The change regularity of structural hydroxyl content further indicates that the formation environment of the symplectitic coronas in Myanmar jadeitite is relatively stable, which is dominated by multi-stage fluid metasomatism, without large-scale dynamic metamorphism. The evolution of the composition and water content of symplectitic coronas in Myanmar jadeitite is helpful to understanding the interaction trajectory of the fluids in the subduction zone in this area and providing some evidence for the diagenetic mechanism of Myanmar jadeitite.

Abstract:The petrological characteristics of Sangpiyu tremolite jade from Xiuyan County of Liaoning Province were studied using polarizing microscope and electron probe microanalysis (EPMA). The zircon and titanite grains which are separated from Sangpiyu tremolite jade were dated by secondary ion mass spectrometry (SIMS). The results show that Sangpiyu tremolite jade is mainly composed of tremolite, and its secondary minerals mainly include apatite, calcite, chlorite, graphite, limonite, zircon and titanite. Under polarized light microscope, the main textures of Sangpiyu tremolite jade are felt-like fiber interweaving texture, micro-fine crystalline texture and fibrous metamorphic texture. The main structure is massive structure. The main chemical components of Sangpiyu tremolite jade are SiO₂, MgO and CaO. The ratio of Mg²⁺/(Mg²⁺+Fe²⁺) ranges from 0.964 to 0.971. The zircon ²⁰⁶Pb/²³⁸U age of Sangpiyu tremolite jade is 1 851±7 Ma, and the titanite²⁰⁷Pb/²⁰⁶Pb age is 1 848±17 Ma. The Sangpiyu tremolite jade was formed in the dolomite during the period of palao-Proterozoic regional metamorphism.