Abstract:The Permian volcanic rocks widely distributed in the northern margin of the Tarim Basin are of great significance for understanding the late Paleozoic tectonic evolution of the Tianshan orogenic belt. The research object of this paper is the tuff of the Balikelike Formation in Halajun area, the geochemical, chronological and Lu-Hf isotope studies have been carried out, which show the tuff is rich in silicon (SiO₂=74.59%~76.18%), high alkali (7.48%~7.79%), low aluminum (Al₂O₃=13.80%~14.29%), belonging to calc-alkaline peraluminous rhyolites; enriched in LREE, relatively depleted in HREE, with weakly positive Eu, relatively enriched in large ionic lithophile elements (LILE) such as Rb and Th, and depleted in high field strength elements (HFSE) such as P, Nb, Ta, Ti, the average Nb/Ta ratio is 16.60, the average Sr/Y ratio is 2.42, and the average Mg^# value is 34.71. LA-ICP-MS zircon U-Pb geochronology shows that the crystallization age of the Balikelike Formation tuff is 280.47±2.58 Ma, the εHf(t) value is from -0.73 to 2.12, and the second-stage model age (t_DM2) is 1 318~1 145 Ma. Combined with the early Permian tectonic evolution, magmatic rocks and sedimentary distribution characteristics of the northern margin of Tarim, it is pointed out that the Balikelike Formation was deposited in the intraplate rift basin where the oceanic crust of the South Tianshan subducted to Tarim Basin, with non-orogenic intraplate magma, which is the partial melting of ancient crustal materials under the action of lithospheric mantle and mantle plume, inheriting the dual-source characteristics of crustal and mantle sources.

Abstract:The Hongnipo deposit is a large Cu deposit newly discovered in southwestern margin of Yangtze Block. In this study, fluid inclusion petrography, microthermometry, laser Raman and in-situ S isotope analysis of sulfide were carried out aiming to reveal the source of metallogenic materials, ore-forming fluid and mineral precipitation mechanism. The mineralization process includes volcano-sedimentary and hydrothermal stages. The fluid inclusions in the quartz from the quartz-calcite-polymetallic sulfide stage (I) include pure CO₂, aqueous-CO₂, aqueous-CO₂ with crystals, liquid-vapor aqueous with crystals and liquid-vapor. These inclusions are usually densely distributed, with a wide range of homogenization temperature (106~500℃) and salinity (8.8%~59.8%). The results of laser Raman spectrum analysis show the volatiles of ore-forming fluid are mainly H₂O, CO₂ and a little CH₄. Sulfides from the volcano-sedimentary stage have δ³⁴S values ranging from 9.18‰ to 9.34‰, suggesting the mixed derivation of sulfur from seawater sulfates and magmatic fluids. Sulfides from the hydrothermal stage have δ³⁴S values that range from 4.42‰ to 5.26‰, which implies a significant contribution of magmatic-sourced sulfur with minor stratal sulfur. Based on the geochronology, fluid inclusions and in-situ S isotopic composition of sulfides, it is considered that Paleoproterozoic volcano-sedimentary processes formed Fe and Cu containing source beds. In the Neoproterozoic, with the breakup of the Rodinia supercontinent, the magmatic hydrothermal fluid from the deep carrying a large number of ore-forming materials mixed with the metamorphic fluid of medium and low salinity and rich CO₂, which triggered the saturated precipitation of ore-forming materials and formed the industrial copper body of Hongnipo deposit.

Abstract:In order to study the pore structure characteristics of the Permian Dalong Formation shale in the Lower Yangtze area, the pore structure of the shale reservoir was studied by means of scanning electron microscopy, high-pressure mercury injection and N₂/CO₂ gas adsorption experiments. The results show that the pore types of the Permian Dalong Formation shale in the study area are mainly organic pores, intergranular pores, intragranular pores, dissolution pores and microfractures. The pore structure is multi-modal and multi-scale, and micropores, mesoporous and macropores are developed. The pores of all sizes contributed to the pore volume, and the micropores of 0.75~1.5 nm, mesoporous pores of 10~35 nm and macropores larger than 100 nm were the main ones. By fitting the correlation between pore volume, specific surface area and buried depth, TOC, maturity(R_O) and mineral content, it was found that the surface area of micropore was positively correlated with burial depth and TOC.The volume and surface area of micro-mesoporous pore were negatively correlated with R_O. Macropore volume is negatively correlated with burial depth, TOC, and Clay mineral content, while it is positively correlated with R_O. Macropore surface area is proportional to buried depth and inversely proportional to R_O. The research results show that the development of shale pore in the Dalong Formation of the Lower Yangtze area is mainly controlled by factors such as burial depth, TOC, R_O and clay mineral content.

Abstract:The basalt waste powder is a by-product of the crushing and processing of basalt stone. It has a fine grain size and is difficult to sell, and there is currently no widely adopted method for comprehensive utilization on a large scale. In this study, eight groups of basalt waste powder from different areas of Hainan Island were selected for analysis. The chemical and mineral composition of the basalt waste powder was determined by inductively coupled plasma emission spectrometer (ICP-OES) and X-ray diffractometer (XRD). The crystallization properties of the basalt waste powder were analyzed by differential scanning calorimeter (DSC), energy dispersive spectroscopy (EDS), and melting experiments. The surface morphology and crystal phase of the fibers prepared from the basalt waste powder were examined by scanning electron microscope (SEM) and XRD, and their properties were compared to those of standard fibers. The results revealed that the fiber prepared at a temperature of 1 450℃ tended to break frequently, and there was a significant presence of dendritic and acicular crystals on the fiber surface. These crystals were identified as wollastonite, quartz, melilite, and magnetite. After raising the temperature to 1 480℃ and maintaining it for 1 hour, continuous fiber was successfully obtained. However, the breaking strength of the fiber was slightly lower than that of standard fibers. Melilite and magnetite were also detected in the fiber. These results validate the feasibility of preparing continuous fiber from basalt waste powder from Hainan Island. This study offers practical guidance and a theoretical foundation for the treatment of basalt waste powder on Hainan Island.

Abstract:The impurity elements and their occurrence forms in magnetite have good environmental indication significance. Si is one of the common impurities in magnetite. Although there are great differences between Si and Fe in ionic radius, valency, energy effect of replacement and other aspects, both the in-situ composition data of magnetite and the wet chemical analysis data show that, magnetite contains a certain amount of Si (the mass fraction of SiO₂ of magnetite crystals generated in hydrothermal environment can reach 6.19%). In order to explore whether Si can statically exist in magnetite and its specific form, the first principles of density functional theory was used to calculate the formation energy of Si in different positions of magnetite crystal, and the stability of Si in magnetite crystal was studied. The results show that the doping formation energy of replacing octahedral Fe with Si in magnetite is -4.13 eV, and the doping formation energy of replacing Fe in the tetrahedron center is -3.85 eV. It is noteworthy that the formation energy of both the two Fe³⁺ (tetrahedron center) in a magnetite cell are replaced is -8.87 eV. From the perspective of doping formation energy, Si can exist in the center of tetrahedron and octahedron of magnetite, but the structure obtained by replacing all Fe³⁺ in the center of tetrahedron with Si is the most stable.

Abstract:The sedimentary and distribution characteristics of polyhalite in the Luobei Sag of Lop Nur Salt Lake were studied using section identification, XRD, SEM, and elemental geochemistry. The results show that polyhalite in the Luobei Sag mainly develops in the middle-upper part of the salt-bearing series. It occurs as either pure-layered polyhalite rocks or in association with glauberite, halite or blodite. There are two origin of polyhalite: replaced and primary. The former is the main type in the Luobei Sag and formed through evaporation of the Lop Nur sulfate salt-type salt lake during the middle and later stages of evolution, with replacement of glauberite or gypsum. The latter may be formed by the enrichment of potassium-magnesium salts due to the supply of calcium-rich brine. The distribution of polyhalite in the Luobei Sag shows a characteristic of thicker in the south and thinner in the north in the south-north direction, and thicker in the middle and thinner on both sides in the east-west direction. The corresponding KCl content also present a similar pattern with higher values in the southern and middle parts, and lower values in the northern and on both sides. These distribution characteristics are clearly controlled by regional tectonic activity, where tectonic-induced subsidence areas are favorable for polyhalite accumulation and mineralization. The shallow burial and large scale of polyhalite deposits in this area make them a potential reserve of potassium salt resources.

Abstract:As a phyllosilicate, illite could fix K⁺ within interlayers. Thus K-Ar, Ar-Ar and Rb-Sr dating methods could be used to investigate and constrain the ages of different geologic events accompanying the formation of authigenic illite. Currently, it is significant to utilize authigenic illite to study the thermal evolution history of sedimentary basins, hydrothermal activities, tectonic movements, and hydrocarbon migration. This paper discusses the possibility of dating formation ages of evaporites by using isotope dating of illites from potash deposits. Although most studies showed that the formation of authigenic illite is favoured in high temperature environment, some authigenic illites could be formed in the salt lake environment of surface temperature. In this case, the controlling factor of the formation of illite is fluid composition. It is the theoretical basis for the study of evaporite formation age by using isotope chronology of authigenic illite. However, many challenges remain in practical research, requiring further investigation.

Abstract:Through systematic sampling and analysis of brine and solids in the salt fields of mining areas Ⅰ and Ⅱ of Qarhan Salt Lake, it is found that the main and trace elements in the brine show different degrees of enrichment in the process of spreading in the salt fields. In addition to salt formation, there are also isomorphism, mother liquor entrainment and other phenomena. Among them, the enrichment rule of rubidium and cesium elements is related to the precipitation of carnallite. The XRD and TOF-SIMS analysis results show that rubidium exhibits a stronger positive correlation with potassium and a negative correlation with sodium, indicating the existence of isomorphism between rubidium and potassium elements. The phenomenon of isomorphism between cesium and potassium elements is not obvious, and it may mainly enter the salt sample through mother liquor entrainment. This research reveals the enrichment patterns and occurrence forms of rubidium and cesium elements in brine, which has certain reference significance for the comprehensive utilization and development of rubidium and cesium resources in salt lakes.

Abstract:In order to find the development position of high quality reservoir and determine the direction of later exploration and development in Weixinan Sag of Beibuwan Basin, this paper studied the location and type of abnormal clay mineral transformation in Weizhou Formation, Weixinan Sag, and identified the cause of abnormally high porosity and permeability zones based on the method of combining experimental analysis and thermodynamic calculation. The results show that, under the influence of thermal fluid activity, abnormal transformation of clay minerals is developed in the study area at the burial depth of 2 300~2 900 m, which can be divided into two types: chloritization and kaolinization. Thermodynamic calculation results also confirm that the chloritization of kaolinite and kaolinization of illite have thermal mechanical priority in Weixinan Sag, which is the important cause of high quality reservoir of the Weizhou Formation in Weixinan Sag. The abnormally high porosity and permeability zones are concentrated in two layers, where the the proportion of chlorite mass is more than 35% (the proportion of kaolinite mass is between 30% and 35%) and the proportion of kaolinite mass is more than 45% (the proportion of chlorite mass is between 10% and 20%). Among them, abnormal kaolinization is mainly developed within the depth range of 2 300~2 400 m and 2 500~2 700 m, abnormal chloritization is mainly developed within the depth range of 2 400~2 500 m and 2 700~2 900 m.

Abstract:Qaidam Basin contains abundant and highly prospective brine potassium-lithium resources. However, with the continuous expansion of production capacity and ongoing development, the easily accessible high-quality resources in the shallow part are decreasing, so it is inevitable to go deep mining. Compared to the shallow section, the brine reservoir in the deep part of the salt lake is relatively poor in quality, with weaker and more unstable water enrichment, so it is very difficult to exploit. In order to find out the characteristics of deep brine reservoir in Beletan section of Qarhan Salt Lake, the planar distribution and thickness variation of deep brine reservoir in Beletan section were studied by analyzing the lithology and physical property data of borehole. The results show that the southeastern part of the study area has the thickest reservoir and the highest quality of rock salt reservoir. Three-dimensional modeling of the brine reservoir shows that lithium-rich brine is mainly distributed in the middle and northern part of the study area, and the lithium content in the southern part is relatively low. The second ore-bearing layer on the plane has a large thickness of rock salt and fewer interbedded silt and clay layers in the central part, which is beneficial to the extraction of brine.

Abstract:Formation water is one of the significant factors affecting the development of gas fields. The presence of water in gas wells can decrease the gas phase permeability of the reservoir, leading to a rapid decline in gas production and severely restricting the improvement of well productivity. Furthermore, there is still some controversy regarding the sources of formation water in study area. In this study, through an investigation of the formation water system in 11 production wells in the Xinchang gas field, hydrochemical and strontium isotopic analyses were conducted to examine the major and trace elements, water-rock interactions, and strontium isotope characteristics. The results indicate that the formation water in the 2nd member of the Xujiahe Formation gas reservoirs exhibits characteristics of low total dissolved solids (ranging from 55 166.00 to 122 547.41 mg/L), high bromine (Br) and strontium (Sr) contents (ranging from 642.00 to 1 711.00 mg/L and 670.00 to 1 780.00 mg/L, respectively), and ⁸⁷Sr/⁸⁶Sr ratios (ranging from 0.715 27 to 0.721 77). These characteristics suggest that the source of strontium isotope in the formation water is different from that of marine carbonate rocks and is more consistent with sandstone weathering. The enrichment of calcium (Ca) in the formation water is primarily related to the dissolution of authigenic minerals in the sandstone reservoir. During deep water-rock interactions, strontium replaces calcium in a cation-exchange manner and acquires bromine from organic matter, leading to an enrichment of bromine. These findings provide a theoretical basis for predicting the water-bearing horizons of the reservoir in the future.

Abstract:The shallow section of Mahai Salt Lake in the Qaidam Basin holds significant reserves of low-grade solid potassium salt resources, which provide resource security for the production of 100 000 tons/year of potassium fertilizer through water-soluble mining and solid-liquid conversion methods. With the continuous progress of water-soluble mining operations, the grade of solid potassium ore in the northern part of the Mahai mining area has further decreased, which brings great challenges to the adjustment of salt field and mineral processing. In order to make full use of this resource, this paper systematically carried out the indoor ore dissolution simulation experiment based on the low-grade solid potash ore samples near the shallow ore layers of boreholes 9-13 and 9-3 in Mahai Salt Lake, with burial depths of 0~3 m. The experimental results show that: ① When the KCl grade of solid potassium ore is low, the degree of the solvent should be appropriately increased, which is conducive to the dissolution of K⁺ ions and the concentration of K⁺ in the dissolution solution. ② The concentration of Na+ in the solvent is too low to dissolve the salt layer skeleton, but the high concentration of Na⁺ will lead to the salt concentration. In the production, the Baume degree of the solvent should be adjusted according to the actual situation of the K⁺ content of the dissolution solution. ③ As the grade of solid potassium ore in the Mahai mining area continues to decrease, when the concentration of K⁺ reaches the production requirement of the salt field, the concentration of Na⁺ in the sodium brine pool will significantly increase. The relative concentration of SO^2-₄ in brine also increase accordingly, the precipitation of rock salt from the sodium brine pool stage will significantly increase, and the composition of the brine entering the mineralization pool will also undergo significant changes. This may have a significant impact on salt field production. The above experimental results can provide reference for the optimization of solvents in salt field production.

Abstract:The Caidian area in western Wuhan possesses abundant geothermal resources, with the heat source being the conductive heat from the earth's interior, primarily stored in the Paleozoic carbonate reservoir. Due to the limitations of various geophysical exploration methods in central Wuhan, the previous petroleum exploration and hydrological data from the Jianghan Oilfield were fully utilized. Combined with the data from the successful drilling of the Suohe1 geothermal well in April 2021, it is analyzed and concluded that the structural framework for heat and water storage in the Caidian area is mainly dominated by anticline structures and the thermal and water transmission channel is mainly fault. The main controlling factors of geothermal resources in the Caidian area are faults and Paleozoic carbonate karst reservoirs,and the karst reservoirs are moderately buried, indicating a good prospect for geothermal resource development. The favorable exploration target of geothermal resources in the Caidian area is various anticline structures associated with deep and large fault.