Abstract:The Luanjiagou borate deposit is located in the Paleoproterozoic Jiao-Liao-Ji orogenic/active belt of the North China Craton. The strata in the area are mainly the Lieryu Formation and the Gaojiayu Formation of the Proterozoic Liaohe Group. The tectonic framework is composed of a series of folds and faults. The magmatic rocks are not developed. There are more than 10 lenticular and lenticular ore bodies, and the wall rock alteration such as serpentinization and chloritization is widely developed. The typical structural features and tectonic systems of the Luangougou borate deposit are systematically studied by geomechanical method, the results showed that the direction of the principal compressive stress in the study area has evolved and transformed from northsouth compression to northwestwest-southeasteast compression-torsion. The mineralization tectonic evolution process can be divided into five stages: “sedimentation→metamorphism→fold-controlled mineralization→fracture-destructive mineralization→final shaping”. The analysis results of the tectonic-mineralization relationship show that the interlayer sliding zones developed in the core, two wings, and hinge zone of the overturned folds, as well as the structural void spaces such as fracture fracture zones and joint-fissure zones, provide key locations for the enrichment and emplacement of ore-forming materials and are favorable sites for borate mineralization. Based on the comprehensive tectonic evolution laws, structural ore-controlling characteristics, combined with orebody geological parameters such as orebody shape, thickness, and grade, the deep prospecting potential prediction was carried out. It is indicated that the area west of the 176 exploration line has good potential for borate resource replacement, and it is recommended to deploy drilling projects in this target area for deep resource verification.

Abstract:In the Yecheng area of the southwestern Tarim Basin, the Well Yutang-1 encountered Nanhua System source rocks for the first time. The zircon ages of core samples were measured at 695±77 Ma and 794±79 Ma, corresponding to the bottom Bolong Formation of the Nanhua System. The total organic carbon (TOC) content ranges from 0.71% to 1.29%, with an average of 0.87%, representing a medium-quality source rock with certain hydrocarbon generation potential. The development and distribution of the source rocks were controlled by the rift trough that formed during the Nanhua Period. During the syn-rift stage, rapid subsidence coupled with a deep-water anoxic environment provided ideal conditions for source rock development, resulting in the deposition of thick succe-ssions of dark mudstone, shale, and marl, which laid the material foundation for forming medium- to high-quality source rocks. The organic matter is predominantly of sapropelic type with high hydrocarbon generation potential; however, due to prolonged deep burial, the thermal maturity is generally high, and the source rocks are mainly in the gas generation stage. The distribution of the source rocks is highly heterogeneous, controlled by the rift trough, and they are primarily enriched in the center of the depression. Together with the dolomite reservoir of the overlying Sinian Kezisuhumu Formation, they form a complete source-reservoir-caprock assemblage of the “lower source rock and upper reservoir” type. The rift trough profoundlly controls hydrocarbon generation-accumulation efficiency through the “trinity” mechanism consisting of syn-rift control source, post-rift thermal subsidence control heating, and late-stage tectonic activation control migration. This study provides important theoretical guidance and practical value for defining exploration directions in the deep ultra-deep Precambrian strata of the Tarim Basin and for selecting “sweet spot” areas.

Abstract:Phosphorite-type uranium deposit represents one of the most important occurrences of global uranium resources. A large-scale uranium-bearing phosphorite has been discovered in the Yankong area of Jinsha, Guizhou, demonstrating significant uranium metallogenic potential. However, the co-existence mechanism of phosphorus and uranium in this area remains poorly understood. Therefore, this study selected three sections located near Yankong Subdistrict (Jinsha County, Bijie City), Minxing Subdistrict (Jinsha County, Bijie City), and Panshui Town (Zunyi City). Sixteen uranium-bearing phosphorite samples were systematically collected to conduct whole-rock major, trace, and rare earth element (REE) geochemical analyses, aiming to reconstruct the paleo-sedimentary environment and determine the material sources. Concurrently, to investigate the microscopic occurrence state of uranium within francolite (carbonate-fluorapatite) in the phosphorite, α-track etching, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were employed. The results indicate that the samples exhibit high V/(V+Ni), U/Th, Ni/Co and V/Cr ratios, suggesting that the metallogenic period occurred in an extremely anoxic, sulfidic, and strongly reducing environment. The REE partitioning patterns display significant negative Ce anomalies, MREE enrichment, and weak positive Eu anomalies. Combined with the Zn-Ni-Co discrimination diagram, it is inferred that the metallogenic materials originated from a mixture of phosphorus-rich seawater brought by upwelling ocean currents and deep seafloor hydrothermal fluids. Uranium distribution within the francolite is non-uniform and shows a significant positive correlation with phosphorus. Most of the uranium enters the francolite crystal lattice through the isomorphous substitution of U⁴⁺ for Ca²⁺, while a minor portion exists as nanoscale inclusions on the surface of the apatite, achieving phosphorus-uranium co-existence. By studying the metallogenic environment, material sources, and microscopic occurrence states of uranium-bearing phosphorite in the study area, a three-stage metallogenic model consisting of “upwelling synergistic with seafloor hydrothermal injection supplying uranium and phosphorus—hydrothermal convective circulation enrichment—reducing environment precipitation mineralization" for the uranium-phosphorus co-existence deposit in the Yankong area has been established.

Abstract:To clarify the spatial distribution characteristics of major potash minerals in low-grade solid potash ores and their implications for water-solution mining performance in the Bieletan mining area of the Qarhan Salt Lake, this study used drill core samples obtained from the 2022 reserve verification project. X-ray diffraction analysis was conducted, and chemical analysis data from both the general survey stage (1967 data) and the reserve verification stage were integrated to investigate the distribution patterns of major potash minerals, such as carnallite and polyhalite, as well as the variation characteristics of KCl content in the ore beds. The results show that halite is the overwhelmingly dominant mineral in the study area, while carnallite and polyhalite are the main potassium-bearing minerals, with the average content of polyhalite being higher than that of carnallite. Significant differences occur in the distribution of potash minerals between the upper and lower ore beds. Carnallite is mainly enriched in the northwestern part of the study area, whereas polyhalite is generally closely associated with carnallite and, in the southeastern part of the upper ore bed, shows spatial correlation with gypsum and clay minerals. Comparison between the general survey and reserve verification data indicates that, after large-scale solid-liquid conversion mining, the distribution of high-grade solid potash ores in the study area has become more dispersed. In the upper ore bed, the average KCl content has decreased and spatial dispersion has increased, whereas in the lower ore bed, KCl content has increased locally and its spatial distribution has become relatively smoother. Comprehensive analysis suggests that carnallite is the principal mineral preferentially dissolved during the solid-liquid conversion process, while the formation of polyhalite may be related to the mixing of K⁺- and Mg²⁺-rich brines released by dissolution with Ca²⁺- and SO^2-₄-rich brines or solvents. The results provide a geological basis for the efficient development, dynamic monitoring, and optimization of solution-mining engineering of low-grade solid potash ores in the Bieletan mining area.

Abstract:The East Tianshan Bogda (back-arc rift basin) Cu-Zn-B-oil shale-P metallogenic belt possesses favorable metallogenic conditions for prospecting marine volcanic-type boron deposits. The Xixiertake-Yikedaban boron deposit of the study area is located in the central section of the Bogda mineralization belt. High-precision magnetic survey and rock-cutting geochemical profile surveys were carried out to analyze the effectiveness of integrated geophysical and geochemical prospecting information for mineral exploration， and explore an effective combination of exploration techniques for boron ore prospecting in the study area. As a result, one △T positive magnetic anomaly was identified in the area of Xixiertake-Yikedaban, and one large boron deposit was discovered. This indicates that the intergration of regional geological background with B₂O₃ geochemical anomalies, high-precision magnetic positive anomalies, and other geophysical and geochemical information has a good effect on the exploration and evaluation of marine volcanic rock-type boron deposits. This technical method can guide the exploration and prospecting of marine volcanic rock-type boron deposits in the East Tianshan Mountains.

Abstract:The Quaternary strata in the Lop Nur region contain abundant brine resources. Through systematic analyses of the hydrochemical characteristics, hydrogen, oxygen and strontium isotopic compositions of brines from the Lop Nur and its surrounding areas, and comparison with the isotope data of the Lop Nur brines obtained in 1995, it is confirmed that the brines are mainly recharged by surrounding rivers. The sulfur and potassium components in the brine primarily originate from the Mesozoic-Cenozoic gypsum layers and glauberite deposits distributed in the southern Tianshan Mountains and the northwestern and southwestern margins of the Tarim Basin, as well as from ancient formation brines. During the Quaternary, the western Tarim Basin experienced uplift while the eastern Lop Nur area subsided. Surface water dissolved and carried these materials during flow, eventually converging in the Lop Nur depression. This process resulted in elevated background concentrations of potassium and sulfur in the regional water system, promoting potassium enrichment when the brine underwent evaporation and concentration to the glauberite precipitation stage. Comparison of hydrogen and oxygen isotope data with those from 1995 indicates that evaporation intensity in the Lop Nur region has continued to increase over the past three decades, suggesting an intensified trend of regional aridification.

Abstract:A stratigraphically continuous marine sedimentary phosphorus-bearing rock series assemblage developed in the Early Cambrian of Dongchuan, Yunnan, provides an excellent carrier for mineralogical studies. This paper focuses on the Meishucunian phosphorus-bearing rock series in Bailongtan, Dongchuan, Yunnan, and conducts a systematic mineralogical study using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that the minerals in the phosphorus-bearing rock series within the area are mainly authigenic minerals such as carbonate-fluorapatite, dolomite, and quartz, accompanied by more volcanic ash that shows a significant negative correlation with phosphorus content, with scarce terrigenous clastics and hydrothermal minerals mostly attributed to later hydrothermal filling. The sedimentary sequence of the phosphorus-bearing rock series completely record the sedimentary environmental evolution from transgression to regression. The formation of phosphorite is highly temporally coupled with the Meishucunian transgression event, indicating that the phosphorus-rich deep-sea water carried by upwelling currents during the transgression was the main phosphorus source. Carbonate fluorapatite mainly occurs within the shells of algae and small shelly fossils, and is almost absent in cements, revealing that phosphorus was enriched through the dense accumulation and burial of organic remains. In addition, the banded phosphorite has a P₂O₅ content of up to 32.90%, with a few micrometre-scale argillaceous laminae, and formed in a low-hydrodynamic-energy environment. In summary, under a transgressive setting, the phosphorus-rich deep-sea water carried by upwelling currents was the main phosphorus source for the phosphorite in the study area. The formation of phosphorite was dominated by biochemical processes, while cement content, detrital input, and hydrodynamic conditions constrained sedimentary preservation and ore grade. This study provides mineralogical constraints on the source of ore-forming materials and metallogenic theories for the Early Cambrian marine phosphorites in South China.

Abstract:The long-debated palaeogeographic pattern of the Doushantuo Period in the northeastern Sichuan-western Hubei region has constrained the understanding of phosphorite metallogenic regularity and exploration planning in this area. To address this issue, this study focuses on the sandstones of the Doushantuo Formation in the northeastern Sichuan-western Hubei region. Through systematic analysis of detrital material sources employing methods such as detrital zircon U-Pb geochronology and lithofacies analysis, combined with seismic reflection profiles, we infer the existence of several small-scale palaeo-uplifts during the depositional period of the Doushantuo Formation. These palaeo-uplifts, composed of glacial diamictite of the Nantuo Formation and trending SW-NE, supplied detrital materials to their peripheries, resulting in the formation of the Doushantuo clastic rocks. Furthermore, based on the distribution of carbonate rocks and mudstones/shales, we deduce that several deep-water depositional areas representing rift troughs, also with a SW-NE trend, developed in the study area. Consequently, a new palaeogeographic framework characterized by an alternating pattern of “palaeo-uplifts and rift troughs” for the Doushantuo Period in the northeastern Sichuan-western Hubei region is proposed. Integrated with studies on phosphate distribution patterns, this study suggests that the carbonate platform margin around the aulacogen in the northeastern Sichuan- western Hubei region is the most favorable zone for phosphate enrichment. This conclusion provides a basis for the prediction of regional phosphate prospectivity.

Abstract:The Cambrian Wusonggeer Formation in the Tarim Basin is a significant subsurface brine reservoir with substantial resource potential due to its enrichment in potassium. Based on an integrated analysis of thin-section petrography, X-ray diffraction, image logging, and comprehensive well-log interpretation, and combined with data from multiple wells and field sections in the northwestern Tarim Basin, this study systematically investigates the res- ervoir characteristics and their primary controlling factors of the Wusonggeer Formation. The results indicate that the formation developed various sedimentary microfacies, including dolomitic mud flat, dolomitic flat, bioclastic shoal, grain shoal, gypsum-bearing dolomitic flat, and mixed siliciclastic-carbonate dolomitic flat. The reservoirs are predominantly composed of algal-related grain dolostones, with a high grain content indicative of a grain-shoal sedimentary environment favorable for reservoir development. The reservoir spaces are diverse, encompassing intragranular pores, intergranular pores, intercrystalline pores, intercrystalline dissolution pores, and fractures. Fractures are notably well-developed in typical wells. Vertically, the reservoirs of the Wusonggeer Formation are concentrated in grain-shoal dolostone intervals with thicknesses ranging from 12 to 51 m, where porosity predominantly falls between 1.2% and 4.3%. Laterally, the Keping outcrop area exhibits locally enhanced porosity of 3% to 5% due to superimposed supergene dissolution, collectively defining a high-quality reservoir characterized by strong heterogeneity and a “fracture-vug” pore system. The fracture network provides effective conduits for fluid migration and is a key controlling factor for reservoir development. The new perspective of the Wusonggeer Formation as a potassium-rich brine reservoir challenges its traditional view primarily as a hydrocarbon reservoir or regional seal, thereby expanding its application potential in the field of potash salt mineralization in saline lake systems.

Abstract:Phosphate rock is a critical strategic non-metallic mineral resource in China. Accurate delineation of deep concealed orebodies requires reducing the ambiguity of individual geophysical methods, which depends on understanding the intrinsic physical-property contrasts between phosphate-bearing strata and surrounding rocks. In this study, 392 core samples were collected from six boreholes in the Bailongtan and Laocunzi phosphate deposits, two representative deposits in the eastern Yunnan phosphogenic belt. Density, electrical resistivity, chargeability, magnetic susceptibility, and wave velocity were measured and integrated with quantitative whole-rock mineralogy determined by X-ray powder diffraction (XRD), establishing a multidimensional petrophysical response framework for concealed phosphate deposits. The phosphorite exhibits a distinctive combination of high density, extremely low resistivity, high chargeability, moderately low wave velocity, and weak magnetism. Its mean density, resistivity, and chargeability are 2.76 g/cm³, 245.40 Ω·m, and 3.67%, respectively. These properties differ significantly from those of the carbonate and clastic rocks in the roof and floor (p<0.001), producing pronounced gravity and electrical contrasts. Mineralogical and microstructural analyses indicate that abundant dense fluorapatite is primarily responsible for the high density. The coupled low-resistivity-high-chargeability response arises mainly from a conductive and electrical double-layer polarization network formed by fine-grained semiconductive pyrite preserved during diagenesis, residual organic matter, and highly mineralized pore fluids within micropores and fractures. Abundant primary pores and a weakly cemented framework account for the low wave velocity and strong attenuation of high-frequency acoustic waves. Finite-difference forward modeling using the measured geoelectrical parameters confirms that electrical resistivity tomography can penetrate the resistive overburden and reliably detect deep, low-resistivity ore layers. We therefore propose an integrated exploration strategy for concealed sedimentary phosphate deposits in eastern Yunnan: gravity surveying for regional screening and target delineation, electromagnetic methods for locating low-resistivity zones, induced polarization for identifying highly chargeable, high-grade orebodies, and seismic and magnetic methods for supplementary constraints. These results provide robust petrophysical evidence and a theoretical basis for exploring deep concealed phosphate resources in the region.

Abstract:Characteristics and hydrogen-oxygen isotopic compositions of halite fluid inclusions in the Hongze sag of the Subei Basin were analyzed to reconstruct the paleoenvironment during salt formation and investigate the supply mechanisms of salt-forming materials. The results reveal that primary halite fluid inclusions in the fourth member of the Funing Formation from SB18 exhibit two distinct types: cumulate and chevron crystals, frequently coexisting within the same strata, indicating an shallow water environment during deposition. The hydrogen-oxygen isotopic composition of these fluid inclusions shows significant deviation from the meteoric water line, clustering in the lower right quadrant. Combined with homogenization temperature data and sedimentary sequences, this pattern reflects intense evaporative conditions during the salt formation process. The sources of salt-forming materials in ancient salt lakes mainly include the weathering and leaching of surface rocks, residual water from marine transgressions, and the lateral infiltration of seawater. Furthermore, the basin's unique “high mountain-deep basin” topography, developed under specific tectonic conditions, provided favorable paleo-environmental settings and accumulation spaces for the concentration of salt-forming materials.

Abstract:The potential boron resources in the Laguo Co salt lake, Xizang, are immense. However, previous studies have primarily relied on geochemical and hydrogeological approaches focused on the lake's interior, resulting in a lack of understanding regarding the equally prospective solid boron-bearing sedimentary rocks on the lake margins and deep paleo-brines. Surface-to-borehole resistivity imaging has been widely applied in the exploration of brine-type minerals due to its ability to fully utilize boreholes, offering high vertical resolution and enhanced resolution of anomalies adjacent to the borehole. Although numerous arrays exist for this method, significant disparities in imaging effectiveness remain, and research regarding the influence of various surface-to-borehole observation parameters is currently insufficient. To address these issues, this study first established a geological-geophysical model of the periphery of Laguo Co salt lake based on field geological and hydrological data. By calculating the sensitivity of various surface-to-borehole arrays and performing inversion tests on theoretical model response data, the response characteristics of different observation arrays to deep boron-bearing brine layers were compared and analyzed. Furthermore, the influence of observation parameters—specifically the number of boreholes, in-borehole electrode spacing, and borehole casing material—on imaging resolution was investigated. The results indicate that a superimposed configuration comprising the Wenner array, BN-AM array, and A-MNB array can effectively recover the geometric dimensions, burial depth, and resistivity values of boron-bearing brine layers. In particular, the utilization of three boreholes penetrating the boron-bearing brine layer achieves superior imaging accuracy. Additionally, increasing the number of boreholes and reducing the in-borehole electrode spacing both enhance the resolution capability for boron-bearing brine layers. The imaging effect is optimal when the borehole is an open-hole completion.

Abstract:The Paleogene period was a critical period of global climate transition. As a low-latitude inland basin, the Lanping Basin is located in the middle of the Tethys Ocean metallogenic belt, featuring diverse mineral species and abundant mineral resources. Currently, studies on the geochemical signatures and paleoclimate of this basin remain insufficient. The coupled evolution of tectonic activity and sediment supply during the Paleogene directly modulated paleoenvironmental frameworks and paleoclimatic evolutionary patterns, which bears great significance for constraining mineralization in this region. Taking the Paleogene clastic rocks of the Lanping Basin as the research object, through geochemical analysis of major elements, using weathering indices such as CIA and ICV and various structural-provenance discrimination charts, this paper systematically conducts research on Paleogene paleoenvironment and paleoclimate evolution, provenance attributes, and tectonic background in the source area. Results show that compared to PAAS, the major elements in the clastic rocks of the study area exhibit generally higher SiO₂ content, lower Al₂O₃ content, and significant differentiation in CaO, K₂O and Na₂O contents; Paleogene sources mainly come from the collision of the recycling orogenic belt; The tectonic background of the Yunlong Period was dominated by continental island arcs, with passive continental margin sources beginning to mix in during the Guolang Period, and completely transforming into passive continental margin by the Baoxiangsi Period; The chemical weathering effect of the Yunlong and Guolang Periods was weak, while the degree of weathering in the Baoxiangsi Period was significantly enhanced; The Paleogene climate evolved from arid conditions to a gradual transition between dry and wet climates, and finally to frequent seasonal dry-wet fluctuations under an overall arid background. The paleolake evolved from closed saline lake via semi-open alternating brackish-fresh lake to open freshwater fluvial-lacustrine facies. Co-evolution of paleoclimate, paleoenvironment, provenance and tectonics background supplies geochemical support for exploring metallogenic environment constraints on Yunlong Formation gypsum and Jinding Pb-Zn deposits.

Abstract:The formation of Sr-rich mineral water in magmatic rock-fault systems cannot be attributed solely to leaching from a single lithology, but is jointly controlled by Sr-rich source rocks, fracture-flow systems, and hydrochemical conditions favorable for Sr preservation. Taking the Shilingxiu mineral-water source area in Xiahuayuan, Zhangjiakou, as a case study, this study integrates shallow geophysical surveys, hydrochemical and rock geochemical analyses, and hydrogeochemical modeling using the PHREEQC software to elucidate the role of the fault-syenite contact zone in controlling Sr release, migration, and enrichment. The results show that the upper 300 m of the study area contains a heterogeneous bedrock-fracture system composed of shallowly buried syenite, fractured andesite, Mg-type water in which Sr occurs predominantly as free Sr²⁺. Celestite is markedly undersaturated, indicating that the prevailing hydrochemical conditions favor the migration and preservation of Sr in dissolved form. Calcite is near equilibrium, whereas dolomite is supersaturated, suggesting that carbonate mineral precipitation may constrain further Sr enrichment. Syenite porphyry has an average Sr content of 764×10^-6 and represents an important potential source rock for groundwater Sr enrichment. Faulting controls the shallow burial of syenite, the distribution of contact zones, and fracture connectivity, thereby locally coupling silicate weathering, carbonate dissolution, and valley-controlled discharge boundaries. The Sr-rich mineral water in the Shilingxiu source area is therefore classified as low-temperature, leaching-derived bedrock-fracture groundwater controlled by the fault-syenite contact zone.