Abstract:Recent advances in Meso-Neoproterozoic chronostratigraphic research in China have yielded critical datasets and candidate sections for establishing standardized stratigraphic frameworks. This study presents new chronostratigraphic findings from the southern margin of the North China Craton. Zircon U-Pb dating reveals that tuff interbeds in the Longjiayuan Formation from Luonan County (1 526±16 Ma, MSWD=0.43, n= 8) and Qishan County (1 535±11 Ma, MSWD=0.68, n=12), Shaanxi Province, constrain these deposits to ca. 1.53~1.52 Ga. SHRIMP U-Pb ages of tuffaceous siltstone interbeds in the Duguan Formation further indicate an age older than 1 385±46 Ma (MSWD=1.07, n= 6). Integrating these results with prior studies, we propose a revised Mesoproterozoic chronostratigraphic framework for North China, addressing the stratigraphic void within the Unnamed System and advancing the standardization of the Qingbaikou System. High-precision tuff-zircon ages from the Luoyukou Formation, Longjiayuan Formation, and Duguan Formation enhance regional correlations between the Changcheng System and Jixian System, supporting their establishment as continuous, complete stratigraphic units and strong candidates for global geostratigraphic standards. Nevertheless, the discontinuous distribution of the Unnamed System and Qingbaikou System in North China, coupled with insufficient geochronological constraints, presents challenges for reconstructing the 1.3~0.8 Ga stratigraphic column and formalizing these systems as standardized geostratigraphic units in the near term.

Abstract:The study of structures along the margins of tectonic units is crucial for exploring the interactions between blocks or plates. The analysis of structural styles near the Zhulazaga ore district on the eastern margin of the Alxa Block not only helps to understand the process of structurally controlled ores, but also can reveal the interaction between the Alxa Block and the North China Plate. The strata in Zhulazaga area is mainly composed of the Mesoproterozoic Zenglongchang Formation and the overlying Agulugou Formation. Results of geological survey show that they are in parallel unconformity contacts. The specific structural styles are: ① the strata form an open anticlinorium, with the axis plunges towards the east and the hinge gently dipping towards the SSE or SSW. During the folding, a series of secondary folds and bedding-cleavage structures are widely developed due to interlayer shearing; ② In the western limb of the fold, the Zenglongchang Formation is thrust over the Agulugou Formation, causing the northeast-verging of folds within the Zenglongchang Formation, which is different from the occurrence of Zenglongchang Formation within the main fold. This is resulted from the top-to-the northeast thrust in the late stage. The formation age of undeformed granite within the folds is 274±3 Ma, which constrains the end time of the regional deformation and is consistent with the mineralization age. Referring to the planar graph and exploration profiles, it is believed that the anticlinorium and fault in the core controlled the mineralization, and the ore bodies were distributed in the transition area from the eastern limb of the anticline to the hinge zone. Based on regional geological data, it is suggested that the anticlinorium formed under the compression associated with the southward subduction of the Paleo-Asian Ocean in the late Paleozoic, followed by the plunging of the hinge related to the sinistral shearing of the Bayan Ul Mountains. The northeastward thrusting is due to the remote effect of the compression in the Tibetan plateau during the Cretaceous. The structural style of rocks near the Zhulazaga area reflects the shortening of the crust and the accompanying shearing during the orogenic process, which is an important example for studying the interaction between blocks or plates.

Abstract:There are abundant brine-type lithium resources hosted in the Upper Cretaceous Zhoutian Formation of the Jitai Basin, Jiangxi Province. However, its sedimentary evolution and depositional model remain controversial. On the basis of previous studies, through the detailed description of the cores of five boreholes in Meigang area of the Jitai Basin, combined with petrology, mineralogy and sulfur isotopes of gypsum, the lithofacies associations were analyzed, sedimentary facies types and sedimentary characteristics were identified, and the sedimentary evolutionary processes of the Zhoutian Formation were summarized. According to the lithofacies associations and sedimentary structures, the sedimentary system of the Zhoutian Formation can be divided into shore-shallow lake sedimentary system in the lower part and salt lake sedimentary system in the upper part. In the early deposition stage of the Zhoutian Formation, the depositional center was located between Taihe and Zhixia areas in the southeast basin, and was mainly composed of conglomerate, fine sandstone, muddy siltstone and silty mudstone. The alluvian-fluvial facies developed at the edge of the lake basin, transitioning to delta facies in the intra-basin, and to the sedimentary center of the lake basin, shore-shallow lake facies. In the late deposition period of the Zhoutian Formation, the climate gradually became arid, and a salt lake environment was formed by the continuous evaporation of the lake water. The rhythmic deposition of mudstone and gypsum rocks was developed, indicating the periodic salinization and desalination process of the lake water. The δ³⁴S value of gypsum is of 8.0‰~15.4‰, mainly concentrated in the range of 10.1‰~12.8‰, indicating that the gypsum was formed in an open salt-forming environment, and almost unaffected by the bacterial reduction process. In the Meigang area, the salt-bearing strata thicken towards the northwest, with well-developed fractured reservoirs, presenting a promising prospect for lithium brine-type deposit exploration.

Abstract:In order to investigate the sedimentary environment, controlling factors and formation pattern of the shale of Longtan Formation of the Upper Permian in eastern Sichuan Basin, systematic tests of organic petrology, organic geochemistry and elemental geochemistry were conducted on the shale samples from Huayingshan profile as the research object. The results indicated that the source rock of the Longtan Formation shale in the studied area is complex. Diagrams of Co/Th-La/Sc, La/Yb-ΣREE and TiO₂-Al₂O₃/TiO₂ suggested that the source rocks of the Longtan Formation shales are mainly Emeishan basalt with high Ti content and intermediate acidic volcanic rocks. The trigonometric diagrams of Th-Sc-Zr, Th-Co-Zr and La-Th-Sc showed that the source rocks were mainly formed in the tectonic background of passive continental margin environment. The average chemical alteration index (CIA) of the Longtan Formation shale was 80.64, indicating moderate to high intensity weathering; the Sr/Cu values ranged from 0.48 to 8.08, with an average of 2.22, and the MgO/CaO values ranged from 0.62 to 52.58, with an average of 14.36, reflecting warm and humid climate condition during the sedimentation period of the Longtan Formation overall. The Sr/Ba values ranged from 0.37 to 1.86 and 100 MgO/Al₂O₃ values ranged from 3.27 to 5.45, indicating a semi-saline transitional sedimentary environment. The mean value of Zr/Al was 7.97×10^-3 and that of 100 Mn/Fe was 0.68, indicating that the sedimentary water in the Longtan period of the Huayingshan area was relatively shallow and was also consistent with the geological background of shallow continental shelf reported by previous studies. The V/(V+Ni) values ranged from 0.62 to 0.98, averaged 0.89, Ni/Co values ranged from 0.47 to 13.81, averaged 5.49, and Ce_anom values had averaged value of 0.03, suggesting that the sedimentary water of the Longtan Formation was mainly in a weakly reductive to reductive environment. In terms of sedimentary environment, organic matter characteristics and geological background, it could be inferred that the organic-rich shale of the Longtan Formation was formed in a warm and humid climate environment. In the background of strong weathering, after the death, the higher plants entered the water body accompanied with the numerous input of terrestrial debris formed by basalt and intermediate acidic volcanic rocks, and high plants rapidly deposited, buried, and effectively preserved under the background of the condition of rapid deposition, and finally that high-quantity source rock with inclined kerogen type was formed.

Abstract:Catastrophic events contain important geological information, and their relics have economic and scientific value. Discovering and studying catastrophic events is one of the methods to solve geological problems and also a way to improve the understanding of geological science. This article lists the main catastrophic events of the Permian bauxite rock series in western Guangxi basing on field investigations, microscopic feature studies, and analysis of heavy metal elements in the bauxite-bearing rock series, and explains their formation. The main catastrophic events in bauxite-bearing rock formations are volcanic ash season, heavy metal anomalies and earthquake episode. The duration span of volcanic ash deposition can extend to 10 Ma, and the lithology of volcanic ash varies from basic to acidic, showing the arc-related calc-alkaline magma series. Compared to bauxite ore concentration areas in the North China and North Guizhou, the bauxite-bearing rock series in studied sections of western Guangxi is strongly enriched in Cr, with an average value of 400×10^-6 to 900×10^-6, whereas Ni is strongly enriched in some sections, with an average value of 300×10^-6~600×10^-6, Cd is enriched in most sections, but Co is enriched in few sections. In addition, Sb and As are greatly enriched in the rocks with felsic volcanic ash. Six elements including Cr, Ni, Cd, Sb, As, and Co constitute heavy metal anomalies. The seismic relics include soft deformation, seismic turbidite, and small graben, etc. The triggering factors for volcanic ash fall and seismic episode were probably the subduction of the Indosinian plate beneath the southwestern margin of the South China plate, which formed island arc magmas and volcanic eruptions, meanwhile the back arc basin tension caused earthquakes. Volcanic ash not only provides substances such as aluminium and iron for bauxite-bearing rock series, but also heavy metals which generated to heavy metal anomalies

Abstract:The Paleocene to Early Eocene was an important climate transition period in the Cenozoic Era, with multiple extreme heat events leading to a weakening of the earth's surface carbon sink capacity and fluctuations in sea levels. Since the Eocene epoch, marine sediment has been recorded in only three areas in China, and the Karatal Formation in southwest Tarim retains a complete record of marine transgression during this period, making it an important stratum for studying the Cenozoic paleoclimate and the evolution of the paleo-Tethys Ocean. This article focuses on the study of extreme climate sedimentary characteristics recorded by the Karatal Formation. The results show that: ① the Karatal Formation records a reliable astronomical cycle, with a depositional duration of 6.6 Ma, consistent with the Lutetai Stage; ② Five components of the storm sequence, namely grain sequence bedding, parallel bedding, mound cross bedding, wavy bedding and massive mudstone, observed in the Kalatal Formation, indicating that the Tarim Basin was in the tropical-subtropical low-latitude area where storms frequently occurred during the sedimentary period; ③ Affected by differences in sedimentary facies and hydrodynamics, 10 types of ooids have developed, including radial ooid, concentric ooid, superficial ooid, complex ooid, elliptical ooid, and eccentric ooid of primary sedimentary origin, as well as micritic ooid, deformed ooid, negative ooid, and dolomitized ooid of secondary alteration origin. In the middle Eocene, abnormal climate events pushed up sea level and seawater entered the Tarim Basin, which lasted until the end of the Lutetai Stage. During the sedimentation period, under the control of greenhouse effect, storms occurred frequently, CO₂ concentration increased, seawater evaporation increased, and continental weathering intensified. The long-term deterioration of the environment resulted in opportunistic selection characteristics of biological fossils. This article supplements the research on abnormal climate in the Cenozoic era in China with evidence from marine profiles.

Abstract:Xiangshan ore field in Jiangxi Province is a representative hydrothermal uranium ore field in China.Describing the evolution of uranium metallogenic hydrothermal fluid in Xiangshan ore field and exploring its formation mechanism is of great significance for promoting innovation and breakthroughs in the theory of hydrothermal ore deposit mineralization, and advancing the development of ore deposit studies.However, due to the lack of deep understanding of the mineralization stage and mineralization dynamics mechanism, the evolution of uranium metallogenic hydrothermal fluid in Xiangshan ore field has been a weak link in the study.This paper discusses the hydrothermal process from filling mineralization to metasomatism mineralization in Xiangshan ore field by redeveloping existing ore analysis data and re-observing the macro and micro phenomena, with hydraulic fracturing uranium mineralization as the main focus. The study shows that the main hydrothermal uranium veins in Xiangshan ore field are composed of filling type mineralization and metasomatism type mineralization.Filling type mineralization has high grade and small scale, with K₂O content of 0.88%~7.03% (average 4.03%) and Na₂O content of 0.12%~1.09% (average 0.35%), complex associated components, small apatite particles, and fast mineralization rate. Metamorphic type mineralization is low grade and widely distributed, with K₂O content of 0.09%~4.50% (average 1.15%), Na₂O content of 1.91%~10.01% (average 6.07%), few associated components, good crystallization of apatite, and slow mineralization rate. Uranium mineralization begins with filling type mineralization and ends with metasomatism type mineralization. The temperature of uranium mineralization does not change much, and the ore-forming pressure and redox potential show a gradual increase process. The ore-forming hydrothermal fluid evolves towards an increase in alkalinity.

Abstract:The Boluositanmiao Complex in the eastern part of the Alxa Block, is one of the high-grade metamorphic complexes, which has important geological significance for the late Paleozoic tectonic evolution of the Alxa Block. In this paper, a combined study of detailed geological investigation, petrography, LA-ICP-MS monazite U-Pb dating and phase equilibrium modeling, were carried out for felsic gneisses of the Boluositanmiao Complex, which is used to reveal their metamorphic evolution and tectonic implications. Felsic gneisses are mainly composed of garnet-bearing biotite-plagioclase gneiss and biotite-plagioclase gneiss. The garnet-bearing biotite-plagioclase gneiss samples ALS2202 and ALS2204 record peak mineral assemblage of garnet+biotite+muscovite+ilmenite+plagioclase+K-feldspar+quartz+melt. Combined with phase equilibrium modeling, the peak p-t conditions of two samples were constrained at 727~751℃/820~1 030 MPa and 730~751℃/930~1 070 MPa, respectively. In addition, the garnet-biotite-plagioclase-quartz (GBPQ) geothermobarometry yields relatively low metamorphic p-t conditions of 629~672℃/410~490 MPa and 620~657℃/330~400 MPa, which correspond to the retrograde cooling. Based on the above results, a clockwise p-t evolution was obtained for the garnet-bearing biotite-plagioclase gneiss samples ALS2202 and ALS2204. LA-ICP-MS monazite U-Pb analyses obtained the weighted mean ²⁰⁶Pb/²³⁸U ages of 268±4 Ma and 255±2 Ma for the garnet-bearing biotite-plagioclase gneiss sample ALS2207 and the biotite-plagioclase gneiss sample ALS2210, respectively, which may represent the timing of peak metamorphism or anatexis. Based on the mineral assemblage, it suggests that the protolith of these felsic gneisses should be sedimentary rocks. Combined with the clockwise p-t path and previously published data in the region, this indicates a significant crustal thickening process in the middle and late Permian, which may be related to the closure of the Paleo-Asian Ocean.

Abstract:The Longshan Complex located in the Qinling-Qilian junction zone is the key to understanding the tectonic evolution of this junction. This study conducted petrographic observations, phase equilibrium modeling and monazite U-Pb dating, to better discuss the tectonic implication. Based on petrographical observation and mineral composition analysis, the garnet biotite plagioclase gneisses sample 21LS30-1 of the Longshan Complex display two metamorphic mineral assemblages: the prograde stage (M₁) (biotite + plagioclase + quartz + rutile + ilmenite) and the peak stage (M₂) (biotite + garnet + plagioclase + quartz + rutile + ilmenite + melt). Sample 21LS37 exhibits two sets of metamorphic minerals during different formation stages: the prograde stage (M₁) (biotite+sillimanite+plagioclase+quartz) and the peak stage (M₂) (biotite+sillimanite+garnet+K-feldspar+plagioclase+quartz+ilmenite+melt). Phase equilibrium modeling constrained the peak p-t conditions of the two samples to be 813~821℃, 1.08~1.1 GPa and 815~819℃, 0.93~0.97 GPa, reaching the medium-pressure granulites facies metamorphism. LA-ICP-MS monazite data from the garnet biotite plagioclase gneisses show ²⁰⁶Pb/²³⁸U ages of 451~425 Ma, 455~431 Ma, 415~395 Ma and 415~394 Ma, respectively. The Longshan Complex and the North Qinling Orogenic Belt underwent similar tectonic processes during the Paleozoic. We preliminarily proposed that the Longshan Complex belongs to the western extension of the North Qinling orogenic belt and has experienced Paleozoic continental-continental collisional orogeny.

Abstract:The Hongshangou porphyry copper-gold deposit is a typical deposit in the Hongshan polymetallic metallogenic area. It is located in the Wu'an depression of Shanxi fault uplift in the southern margin of the central North China Craton. The ore body mainly occurs in the Hongshan syenite porphyry. Muscovite and chlorite are well developed in the mineralization center and periphery. In order to discuss the diagenesis and mineralization significance of muscovite and chlorite in Hongshangou copper-gold deposit, electron probe microanalysis (EPMA) was used to analyze muscovite and chlorite in different occurrences and metallogenic stages of the deposit. The results show that the distribution characteristics of chlorite in the mining area can be divided into three categories: chlorite associated with metal minerals (Chl-1), chlorite altered from hornblende (Chl-2) and chlorite altered from biotite (Chl-3). The three chlorites are all Fe chlorites, indicating that they were formed in a reducing environment. The replacement of Fe to Mg and the replacement of Si to Al^Ⅳ in the structure indicate that the formation of chlorites is affected by Fe- and Mg-rich ore-forming fluids. The formation temperature of chlorite calculated by geological thermometer is between 112~272℃, which belongs to the range of medium-low temperature hydrothermal alteration, LA-ICP-MS results show that the completely altered chlorite is richer in Cu, Sn, Rb, Zn, Ti, Li, Sr, V, Co, Ni and Sn. Muscovite mainly includes primary muscovite (Ms-1) and secondary muscovite (Ms-2), which belong to ordinary muscovite and polysilicic muscovite respectively. The muscovite closely related to mineralization has the characteristics of high Si, Fe and low Al, LA-ICP-MS results show that the muscovite formed in the reducing environment is richer in V and W than the muscovite formed in the oxidizing environment, suggesting the mixing of meteoric water in the later stage of the fluid. Based on the research results of this paper, the ore-forming fluid of Hongshangou copper-gold deposit is acidic in the early stage and gradually changes to neutral in the later stage. The ore-forming environment of copper-gold deposit is near neutral and reduced medium-low temperature environment. The ore-forming fluid is rich in Fe, Mg and poor in Si.

Abstract:In order to find out the distribution characteristics of rare elements, the genesis of pegmatite and deep prospecting potential of Lijiagou spodumene deposit in Jinchuan County, Sichuan Province, statistical analysis of rare elements from ore-bearing pegmatite, barren pegmatite and wall rock in exploration trenches and drill holes on No.2, 5, 9 and 11 from exploration lines from east to west in the largest No.Ⅰ vein of Lijiagou spodumene deposit, and in situ crystallization simulation calculation was conducted on the Ke'eryin two-mica granite and the ore-bearing pegmatite of No.Ⅰ vein. The analysis results show that the main rare element in No.Ⅰ vein is Li, accompanied with Be, Rb, Sn, Nb and Ta, which have similar characteristics to the rare element in the Jiajika X03 vein. The metallogenetic elements distribution regularity of the No.Ⅰ vein from top to bottom is that Li is enriched in the upper part, Be is enriched in the middle part, Nb and Rb are enriched in the lower part, while Nb and Rb in the Jiajika X03 vein are relatively enriched in the upper part of the ore body. The in situ crystallization simulation calculation indicated that the No.Ⅰ vein of Lijiagou was not formed by crystallization differentiation of a set of magma systems that formed Ke'eryin two-mica granite. The petrogenesis mechanism of the pegmatite of Lijiagou spodumene deposit may be that the first step is the low degree partial melting of the metamorphic sedimentary rock to generate relatively Li rich melt, followed by further enrichment of the melt through crystallization differentiation to form Li saturated melt, and finally crystallization to form spodumene pegmatite.

Abstract:Niobium is a rare metal and strategic resource that plays an important role in modern industry. The Bayan Obo Nb-REE-Fe deposit is a super-large niobium deposit with 2.2 Mt Nb₂O₅ resources at an average grade of 0.13%. Therefore, it is very important to find out the occurrence and distribution characteristics of niobium. The niobium mineral in the Bayan Obo deposit has the features of fine, scattered and thin, which is difficult to find by polarizing microscope, so it is impossible to achieve the research purpose. On the basis of petrography and EDS analysis, the occurrence and distribution characteristics of niobium in deep aegirine-rich Nb-REE-Fe ores in the Bayan Obo main mine were studied by means of AMICS and EPMA. The results show that the average content of Nb₂O₅ in the ores is 0.15%. Niobium mainly occurs in columbite, pyrochlore, aeschynite, baotite and ilmenorutile, the total mineral content of 5 niobium minerals in aegirine-rich ores is 0.40%. The particle size of niobium mineral is fine, < 90 μm accounts for more than 88.16%, and it is a subhedral or anhedral grain. The results of EPMA show that the average content of Nb₂O₅ in columbite, pyrochlore, aeschynite, baotite and ilmenorutile is 73.46%, 63.42%, 28.43%, 16.03% and 15.81%, respectively. Niobium is mainly occurred in the form of independent niobium minerals, and a few occurred with other minerals in the form of isomorphism and inclusion. Niobium minerals are scattered and mainly distributed among aegirine, monazite and apatite or aegirine, barite and bastnäsite particles, often associated with aegirine, fluorite, monazite, bastnäsite, barite, apatite and other minerals. The chemical composition of niobium minerals is considerably complex, and the phenomenon of isomorphic substitution is common. The chemical formula of 5 kinds of niobium minerals is calculated and quite complex. There are obvious correlations between Nb and some elements in niobium minerals, and there are selective substitution of Ca²⁺ and Th⁴⁺ ions in aeschynite, this further indicates that complex isomorphic substitution of niobium minerals occurs during the formation process. Nb₂O₅ has the highest occupancy rate in pyrochlore and the lowest in baotite, the former is nearly 32 times of the latter. The total occupancy rate of 5 niobium minerals was 90.51%. Pyrochlore, columbite, ilmenorutile and aeschynite are the main industrial minerals for extracting niobium. This study provides a basis for the mineral processing of niobium in order to make full use of the niobium resources in Bayan Obo.

Abstract:The newly discovered high-quality green jadeite in Guatemala is comparable to the high-end green jadeite from Myanmar, gradually becoming an important source of high-quality green jadeite jewelry materials in the domestic jewelry market. However, research on its petromineralogy and typomorphic characteristics remains relatively weak. This study selects a large number of Guatemalan high-quality green jadeite materials and jewelry that have appeared in the Chinese market as research subjects. Through microscopic observation, laser Raman spectroscopy, EMPA, and other testing methods, a systematic analysis of their mineral assemblages and compositional characteristics was conducted. The research findings indicate that the high-quality Guatemalan green "Mayan Green" jadeite materials appearing in the market are primarily composed of omphacite minerals, with secondary minerals including phlogopite, phengite, zoisite. Omphacite can be classified into three different formation stages, Omp-Ⅰ, II, and III, based on its mineral assemblages and their interrelationships. Among them, the high-quality Guatemalan green jadeite jewelry are mainly composed of omphacite formed in the Omp-Ⅲ stage, characterized by relatively low Mg (average 7.59%) and Fe (average 1.57%) contents, relatively high Cr content (average 0.24%), and a jadeite component X_jd>0.5 (average 0.53). Existing research indicates that the jadeites in different segments of the Motagua Fault System in Guatemala possess distinct mineral assemblages. However, the high-quality green jadeite jewellerys studied in this paper exhibit a relatively uniform mineral composition in the domestic market, primarily composed of pure omphacite. They may contain two specific metal mineral inclusions, chalcocite and nickeline. The endmember composition and mineralogical characteristics show significant differences compared to other sources of high-quality green jadeite, enabling effective differentiation between high-quality Guatemalan green jadeite, traditional Myanmar green jadeite, and high-quality green jadeite from other origins by providing essential reference characteristics in petrology and mineralogy.

Abstract:The Manono region of the DRC is rich in pegmatite-type lithium, tin, niobium and tantalum resources. In the historical production process, only tin and niobium tantalum minerals were recovered, while lithium-containing minerals were discharged with tailings and stored until now. To determine the occurrence characteristics of lithium-containing minerals in tailings, the process mineralogy of lithium-containing minerals in tailings samples was studied by particle size analysis, X-ray fluorescence spectroscopy (XRF), chemical multi-element analysis, X-ray diffraction, scanning electron microscopy, and other comprehensively methods. The results indicate that the Li₂O grade of the lithium-containing tailings sample is 1.05%, and 95.04% of the lithium element in the ore is distributed in spodumene. The mineral content of spodumene in the raw tailing ore sample is 13.1%. Spodumene is mainly distributed in medium-coarse grains and has a simple association with other minerals, with low weathering degree. The Li₂O content in spodumene is 7.9%. Through the study of process mineralogy of lithium-containing minerals, it has been determined that the lithium-containing tailings belong to the spodumene-type (tailings) deposit, with good mineralogical indicators for mineral processing, providing a technical basis for the recovery of spodumene from tailings.