Abstract:Huaying Pianyanzi area is located in the middle-east of Sichuan Basin. The newly discovered Pianyanzi Late Permian basalt is between Maokou Formation (underlying) and Longtan Formation (overlying), which can be compared with Emeishan basalt. The study of petrology, mineralogy and geochemistry suggests that Pianyanzi basalts belong to the high-Ti alkaline series, and the rare earth element (REE) and trace element patterns are similar to those typically found in ocean island basalts (OIB). The basalts have not undergone any significant crustal contamination. The crystallization temperature of clinopyroxene is estimated to be 1 405~1 439℃, suggesting anomalously thermal inputs from a mantle source and a possible plume-head origin. The REE simulation result su-ggests that Pianyanzi basalts were produced by small degree of partial melting of Emeishan mantle plume within the garnet-spinel transition region. In general, the Pianyanzi Late Permian basalt is very similar to the Emeishan basalt, especially the basalt in the east of Emeishan Large Igneous Province (ELIP), which is an integral part of ELIP.

Abstract:Large-scale crustal extension happened in Northeast Asia continent during the Late Mesozoic, represented by metamorphic core complex and asymmetric granite domes. The extensional shearing mechanism has always been one of the important issues in tectonic research. Three asymmetric extensional granitic domes, including Hanwula, Nalan and Baoder, are spread along the southeast section of the China-Mongolia boundary in the NE direction. The main body of these domes are the Late Mesozoic granitic intrusions. Ductile shear (mylonitic) zones are developed in the northwest margin of these domes, which are confined by the later high-angle normal faults. According to the structural relationships between the strongly deformed medium coarse-grain K-feldspar granite (133±1 Ma) and the weakly deformed fine-grain granite (128±2 Ma) in the ductile shear zone of the Hanwula dome and their zircon U-Pb ages, it is inferred that these granites may be syn-extensional intrusions, and the timing of ductile extension is after 133 Ma and lasts to 128 Ma or later, which is the same as the development time of other domes in the NE Asia. We use R_f/ф method to measure the finite strain axial rates of feldspar in mylonites from the three ductile shears, Hsu diagram shows that the strain type is plane-flattening strain type (average k=0.5). Polar Mohr circle method, the rigid particle network method and the C-axis quartz fabric method are used to estimate the long-term deformation processes of ductile shearing. The methods gave average kinematic vorticity values of 0.68~0.74 of mylonites, which indicated that the ductile shearing of these domes was dominated by general shear with nearly equal pure shear and simple shear components. Kinematic vorticity values of the later stage of ductile deformation obtained by the quartz diagonal strip method are 0.87~0.99 with an average value of 0.93, which indicated that the ductile deformation converted from general-shear-dominated to simple-shear-dominated. However, kinematic vorticity values obtained by the C' (stretch fold cleavage) method are 0.53~0.74 with an average of 0.68, which indicated that the latest incremental strain in progressive deformation process is mainly pure shear. The results show that the ductile shear detachment zones of these domes are mainly formed by general shear. In the early stage, the simple shear component gradually increased. In the later stage,the simple shear component decreased due to the processes of magma upwelling and overall exhumation. The shear deformation is dominated by pure shear. Compared with other extensional domes and metamorphic core complexes in NE Asia at the same period, this kind of shearing pattern may be general significance.

Abstract:Mantle xenoliths, with minor garnets, have been found in the Quaternary volcanic rocks in Da Hinggan Mountains. Reaction rims, documenting significant records of mantle dynamic evolution, are common in most of the garnets. Optical photomicrographs and BSE pictures demonstrate three types of reaction rims of garnets, ① coronal rims, a thin layer of 0.1~1 mm enclosing the relic garnet, with a typical mineral assemblage of Opx+Glass, Cpx+Glass or Grt+Sp; ② vein rims, vein-like strips in several 100 μm in width and several millimeter in length, with a typical mineral assemblage of Opx+Glass; ③ microfracture rims, very thin reaction rims of several to several ten micrometers thick along microfractures in garnet, with a typical mineral assemblage of Sp+Glass. On the aspect of petrogenesis, these reaction rims were divided into two types, ① origin of magma/melt reaction with garnet:Some reaction rims have quite different bulk chemical composition from the precursor garnets. For example, K₂O and Na₂O compositions in garnet reaction rims are one or two orders of magnitude higher than those in precursor garnets, indicating that compositions from mantle melts or alkaline magmas were induced to the mineral assemblages of reaction rims; ② origin of isochemical breakdown of garnet:The other reaction rims have nearly the same bulk chemical compositions as the precursor garnet, indicating isochemical breakdown of garnet without any significant chemical compositions from mantle melts or other minerals, especially the vein rims and microfracture rims. Hence two types of garnet reaction rims with quiet different origins were found in Quaternary volcanic rocks in Da Hinggan Mountains. These garnet reaction rims provide evidences of K₂O- and Na₂O-rich melt reactions and mantle refertilizing processes, as well as evidences of evolution of mantle p-T conditions. Studies on garnet reaction rims may light on further understanding on chemical evolution and thermal history of lithospheric mantle in Da Hinggan Mountains.

Abstract:Lenghu uranium deposit is a newly discovered in recent years and have industrial value sandstone-type uranium deposit in the northern part of the Qaidam Basin. In order to study the classification, occurrence and mineralization of uranium minerals in this area,this paper conducted the mineralogical, electron probe, backscatter electron imaging analysis of the altered minerals in Xiaomeigou Formation of Lower Jurassic on the basis of field investigation. These studies found that the ore types of Xiaomeigou Formation in Lenghu are mainly composed of complex sandstone-type and carbonaceous sandstone-type, which have occurred overall epigenetic alteration. It is found that the main uranium minerals are uranite, pitchblende and minor of lead selenite, which is closely associated with clay minerals, organic matter, and pyrite, and lie in the intergranular space of quartz, feldspar and other altered lithic mineral grains or in cleavage joints of altered minerals occurs in fine columnar, gel-like or irregular sawtooth shape. In late multiple fluid processes, U⁶⁺ occurred reduction-precipitation-adsorption uranium mineralization in the reduction environment provided by Fe²⁺. Based on the analysis of high Y and low Y-types uranium minerals, alteration sequence and environmental characteristics, it is inferred that uranium in uranium minerals was the residual of original uranium minerals, which is enriched and mineralized by multi-stage transformation of fluids with no Y element or very low Y element.

Abstract:A suit of metamorphosed sandstones of the Wutai Group in the Wutai Complex, North Central North China Craton was recognized recently. Their provenance and tectonic setting are vital for further understanding on the Late Neoarchean crust evolution in this area. The metamorphosed sandstones are mainly composed of quartz, feldspar and clay cement. The petrographic characteristics show that they are greywackes, which is consistent with the result distinguished by their major and trace elements compositions. The geochemical features show that they have relatively large variation of SiO₂ content (64.51%~71.80%), and relatively low maturity (SiO₂/Al₂O₃=3.98~4.73). Their chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) are 60~76, 63~91 and 61~89, respectively, which indicate that the protolith of the metamorphosed sandstones was formed by rapid transportation and deposition of near-source weathered clasts. Compared with ratios of immobile elements (such as Th/La, Sm/La, Zr/Hf, Y/Ho) of the potential source rocks, the provenances of metamorphosed sandstones are mainly from acidic volcanic rocks. This result is highly similar to those of sedimentary materials of the continental island arc which were mainly derived from acidic volcanic rocks. The discrimination results of trace elements on tectonic setting also show that the characteristics of the sandstones assemble those of the continental island arc. Consequently, we consider that the metamorphosed sandstones of the Wutai Group, North China Craton, were formed in a continental island arc setting in the Late Neoarchean.

Abstract:In recent years, the Paleogene deep exploration of Pearl River Mouth Basin has gained repeated breakthroughs, and the economic basement has been gradually lowered to more than 4 000 meters. Exploration practices show that Paleogene reservoirs of Lufeng area and Huizhou area display significant diversity and that the Paleogene reservoir in Lufeng area is better than in Huizhou area. To clarify the difference of the Paleogene reservoir between these two areas, the diagenesis of reservoir is studied by using thin section, scanning electron microscope, X-ray diffraction and physical properties analysis. According to the dissolution characteristics and dissolution products of rocks in the secondary pore development zone, the corresponding relationship between them and reservoir physical properties is established and then the pore evolution models of different types of reservoirs are restored. The research reveals that Wenchang Formation sandstone in Lufeng area, which is obviously influenced by Mesozoic sedimentary rocks,is characterized by high contents of quartz and low contents of feldspar, and mainly primary pores of pore types, develops low porosity and medium permeability or medium-high porosity and medium-high permeability reservoirs. Wenchang Formation sandstone in Huizhou area, which is obviously influenced by Mesozoic granite sources, is characterized by low contents of quartz and high contents of feldspar, mixed pores of primary pores and dissolution pores of pore types, develops medium porosity and low permeability reservoirs which could be changed into medium porosity and medium permeability reservoir refer to strong hydrodynamic force. Comprehensive study shows that the nature of parent rock determines the inherent advantages of reservoir, and that sedimentary rebuild improves the original physical property of reservoir, diagenesis difference affects the quality of reservoir. Understanding the development conditions and formation mechanism of high-quality reservoirs is of great significance for the Paleogene reservoir dessert prediction in different areas.

Abstract:Paleoclimate fluctuations directly or indirectly change ecosystem, and sediment composition, which leaded to that the change of hydrocarbon generation potential of sedimentary rocks. Lacustrine rift basin, one important type of petroliferous basin, has currently been recognized to be an important tight oil exploration area. However, study on co-variation between climate fluctuation and hydrocarbon generation potential is absent. Dongpu Depression, developed on Paleozoic-Mesozoic basement, is a Cenozoic lacustrine rift basin, whose sedimentary records were mainly controlled by short-term climate fluctuations during tectonic quiescent period. In this study, compilation and comparison of mineralogy, micropaleontology and organic geochemistry data from Wengu 4 well in Dongpu Depression were used to reveal the genetic relationship between paleoclimate fluctuations and hydrocarbon generation potential. The results suggest that the Paleogene Shahejie Formation (third member 8~10) was formed in overall dry-hot climate, with several times of climate fluctuations between relatively dry and relatively humid, which correspond to the waning and waxing of organic content. Co-variation of climate and organic content from Shahejie Formation indicate a genetic relationship between paleoclimate fluctuations and hydrocarbon generation potential, humid climate is more beneficial for the accumulation of organic matter.

Abstract:The Miaoliang gold deposit is located in the center of the Southern Qinling Zhashui-Shanyang ore concentration area. In order to find out the characteristics of ore-forming fluids, the precipitation mechanism of gold and genesis of the Miaoliang gold deposit, the fluid inclusions in gangue minerals at different metallogenic stages of the deposit were studied in detail by petrography, microthermometry, laser Raman spectroscopy, comparing with the characteristics of typical surrounding gold deposits. The results show that the deposit is rich in types of inclusions. The early stage of mineralization is mainly H₂O-NaCl type inclusions (type Ⅱ), part of H₂O-CO₂ type inclusions (type Ⅲ) and a small amount of pure CO₂ type inclusions (type Ⅰ); the main metallogenic stage is mainly H₂O-NaCl type inclusions (type Ⅱ) and H₂O-CO₂ type inclusions (type Ⅲ); the late mineralization stage is mainly H₂O-NaCl type inclusions (type Ⅱ). Microscopic temperature measurements show that from the early stage to the late stage, the fluid properties evolve from medium and high temperature, medium salinity, low density, CO₂-rich fluid to medium and low temperature, medium-low salinity, medium density and CO₂-poor fluid. Laser Raman analysis shows that the gas phase of inclusions contains a certain amount of CH₄ and H₂S in addition to CO₂. Comprehensive study concluded that gold migrates in the form of Au(HS)₂^- complex in the fluid under the reduction environment of low oxygen fugacity, and that immiscibility due to the decrease of temperature and pressure is the main mechanism of gold precipitation in the process of fluid upward migration.

Abstract:The paper is a systematic collection of 137 new minerals approved by the Commission on New Minerals,Nomenclature and Classification(CNMNC) of the International Mineralogical Association(IMA) in 2013, by listing mineral name, crystallochemical formula, crystal structure data, physical and optical properties, locality of origin and occurrence, relationship with other minerals, source of mineral names, chemical reaction and spectroscopic characteristics.It's very meaningful that Chinese names of 137 new minerals have been examined and revised under the authority of Chinese Commission of New Minerals and Mineral Names. As a part of the comprehensive introduction to discovery and research of new minerals in the world,this paper will provide reference for the work of discovering, researching and naming new minerals in China and promote the standardization of Chinese names of mineral species.

Abstract:It has been found that siderite (FeCO₃) could directly hydrolyze microcystin -LR (MC-LR) under anaerobic conditions in previous studies. However, oxygen (O₂) could not be completely avoided during application process. Therefore, it is urgent to study the effect of dissolved oxygen content (DOC) on the degradation efficiency of MC-LR by siderite. The results showed that the degradation rate of MC-LR under O₂ conditions (DOC=1.62~21.87 mg/L) is higher than that under anaerobic conditions (k₀=0.030 16 mg·L^-1·h^-1), and its degradation rate increased with the increase of O₂ content. When the volume of O₂ added was 1.0 mL (DOC=21.87 mg/L), siderite showed the highest degradation rate of MC-LR (0.083 34 mg·L^-1·h^-1), which was 2.76 times higher than that without O₂. According to humic acid (HA) additions and radical capture experiments, it indicated that siderite could directly activate O₂ to produce superoxide radical (·O₂^-), facilitating the oxidation of MC-LR. However, the addition of HA inhibits the selective hydrolysis of MC-LR by FeCO₃. Finally, the LC-ESI/MS analysis of MC-LR degradation intermediates showed that under aerobic conditions, the hydrolysis sites of MC-LR occurred in Mdha-D-Ala and Adda-L-Arg peptides. Bond, under the oxidation of (·O₂^-) produced by the activation of O₂ by Fe^Ⅱ on the FeCO₃ surface, the hydrolyzed product continues to undergo hydroxylation and decarboxylation reactions, and is finally converted into small molecular aldehydes.

Abstract:The geochemical characteristics and abnormal sources of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil of Southern Xuancheng were analyzed and studied by using the 1:250 000 land quality geochemical survey data. It is found that the geological background is the main controlling factor for the content of soil elements, and that the spatial distribution characteristics of heavy metal elements in the surface and deep soil in the area are significantly consistent with the geological background and sedimentary environment. The high content of heavy metal in the soil parent rock geological background (Hetang Formation, Piyuancun Formation and Lantian Formation, etc) is the main influencing factor for the high anomaly of soil heavy metal elements. In addition, mining and atmospheric dry and wet deposition are also one of the factors affecting high anomaly of heavy metals in soil. It is found that Pb, Hg, Cd and Cr in soil have input sources of atmospheric dry and wet deposition. The main impact index of heavy metal in soil pollution risk in the survey areas was Cd. The proportion of samples that soil Cd exceeded the control value of soil pollution risk of agricultural land was 2.56%. The morphological analysis results show that soil Cd is mainly in ion-exchange state. Combined with crops investigation, it is found that there is a certain ecological risk in the area with high abnormal soil Cd.