Significant advances have been made in the geochemical study of barium (Ba) isotopes over the past decades, demonstrating considerable potential for their application in tracing crust-mantle interactions, crust recycling in subduction zones, granite differentiation, magmatic-hydrothermal fluids and mineralization processes, as well as marine productivity. This paper systematically reviews the current progress in Ba isotope studies related to high-temperature geological processes. Recent research has preliminarily established the range of Ba isotope variations in different geological reservoirs, revealing distinct Ba isotopic compositions between crustal materials of various origins (such as sediments and altered oceanic crust) and the depleted mantle. Theoretical calculations, experimental studies, and observations from geological samples indicate that Ba isotope fractionation among Ba-bearing minerals is limited under high-temperature equilibrium conditions. However, processes such as dehydration of hydrous minerals during metamorphism, exsolution of magmatic-hydrothermal fluids, and fluid-rock interactions can lead to significant Ba isotope fractionation. Finally, this paper presents research progress and case studies on the use of Ba isotopes to investigate crustal-material recycling, granite evolution, and mineralization, highlighting the application potential of Ba isotope in tracing high-temperature geological processes.
Sulfur is a volatile element that is prone to mass-dependent fractionation of sulfur isotopes (MDF-S) during shallow magmatic processes (e.g., fractional crystallization and magma degassing), which limits us to constrain the properties of major mantle chemical reservoirs. The mass-independent fractionation of sulfur isotopes (MIF-S) is a phenomenon in which the fractionation behavior of sulfur isotopes deviates from the mass dependent relationship. MIF-S is mainly produced through photochemical reactions of sulfur-containing molecules under high-energy ultraviolet radiation, and its fractionation mechanism is closely related to the atmospheric evolution on early Earth. It is worth noting that MIF-S signals are commonly preserved in Archean sedimentary rocks, but they disappeared after the Great Oxidation Event (GOE). MIF-S does not rely on mantle redox states and high-temperature processes (such as partial melting, fractional crystallization, magma degassing), and can effectively avoid MDF-S driven by shallow magma processes. And so, MIF-S is crucial for understanding the onset of plate tectonics, mantle redox states, and deep material cycling. On the basis of a brief introduction to the theories of MDF-S and MIF-S, this review summarizes the sulfur isotope composition of major mantle chemical reservoirs, and focuses on the important progress in mantle heterogeneity and onset of plate tectonics recorded by MIF-S in the past two decades.
Columbite-tantalite, characterized by high closure temperature, high uranium content, and low common lead, is an ideal mineral for U-Pb dating. Its isotopic chronology provides critical constraints on the genetic mechanisms of rare-metal granites and pegmatites. The main U-Pb dating methods for columbite-tantalite include isotope dilution-thermal ionization mass spectrometry (ID-TIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). This paper systematically reviews the basic principles, development history, technical advantages, and existing challenges of these three dating techniques, with a focus on summarizing recent application advancements in constraining ore-forming epochs and deciphering metallogenic processes of rare-metal deposits. The study reveals that it remains the current technical bottleneck and future research priority to achieve high-precision and accurate U-Pb age determinations for columbite-tantalite across polyphase mineralization events due to the complex and variable end-member compositions of columbite-tantalite and the pervasive matrix effects inherent in commonly used in-situ dating methods (LA-ICP-MS/SIMS). Future studies should focus on developing mineral compositional reference materials and optimizing analytical protocols to overcome these limitations.
Accurate and high-precision analysis of Cd isotope composition in geological and environmental samples is of great significance for the study of marine primary productivity, paleoenvironmental changes, traceability of heavy metal Cd pollution, genesis of sulfide deposits, and marine Cd cycles. However, the low Cd content and complex matrix of environmental and geological samples pose challenges to high-precision Cd isotope analysis. For geological and environmental samples, this study developed an efficient and reliable two-column Cd chromatographic separation procedure and a high-precision Cd isotope determination method. In the first column of AG-MP-1M anion exchange resin, a large amount of the matrix, including ≥99% ratio of Sn, was removed first, then Cd and a small amount of Sn were rapidly eluted using 4 mL of 1M HNO3 solution. Unlike the traditional second-column separation of Cd using TRU, Spec, UTVEA and BPHA extraction resins, in addition to Mo, Sn and Zr elements, TOPO resin can further separate other potential residual matrix elements such as Mg, Fe, Pb, Ti, V, Ag, Cu and Zn, etc., without causing problems with resin-derived organic matter. Cadmium isotope ratio was conducted on Neptune Plus MC-CP-MS, using double spike method (111Cd-113Cd) for instrumental mass discrimination correction. The long-term external reproducibility for two standard solutions (NIST SRM 3108 and Spex Cd) was better than ±0.05‰ (2SD).Geological and environmental standard samples processed by the presented two-column Cd chromatographic separation procedure and then determined the δ114/110CdNIST 3108 values are consistent with the values reported in the literature within uncertainty, confirming the accuracy, reliability and efficiency of this method. Furthermore, the Cd isotope compositions of the domestic geological standard samples GSR-2 and GSR-3, and soil standard sample GSS-6a are reported for the first time, which are beneficially for evaluating the analytical capabilities between different laboratories and data quality control. Overall, this study will provide efficient and convenient new technique for the accurate and high-precision Cd isotope analysis of geological and environmental samples.
The rare earth element (REE) resources are rich in China, among which the ion-adsorbed REE deposit in South China is unique. Its spatial and temporal distribution characteristics indicate that its formation is closely related to the Mesozoic granites in South China, but the internal genetic relationship is still not deeply understood. A comprehensive study on the Bankeng granite in the Nanling (the ore-forming parent rock of Bankeng REE deposit) has been carried out, including petrography, zircon and apatite chronology, lithogeochemistry, zircon Hf isotopes and whole-rock Sr⁃Nd⁃Li isotopes. The U⁃Pb dating of magmatic zircon and magmatic apatite in the Bankeng granites yield ages of 185.5-194.0 Ma and 189.2 Ma respectively, indicating that the emplacement occurred in the Early Jurassic. They are mainly composed of felsic minerals (Q+Ab+Or≥95%), with only a small amount of biotite (< 5%) in the mafic dark minerals. Their geochemical characteristics show high SiO2 (75.93%-77.48%), rich K2O (5.27%-5.55%), low MgO (0.09%-0.14%), and poor MnO (0.02%-0.03%), as well as a high zircon saturation temperature (801-847 ℃), high Zr+Nb+Ce+Y content (360×10‒6-534×10‒6), and a 10 000×Ga/Al ratio (3.2-4.2), which are similar to the highly differentiated A-type granites. The Sr⁃Nd⁃Hf⁃Li isotopic characteristics ((87Sr/86Sr)i=0.704 477-0.712 715, εNd(t)=-5.0-(-5.2), εHf(t)=-6.8-(+1.4), δ7Li=-0.88‰-6.65‰) indicate that the magma source may be REE-rich igneous rocks from Mesoproterozoic recycled ancient crust that was intruded into the shallow crust. The Bankeng granites exhibits A2-type granite properties (Y/Nb=1.21-2.09), combined with the regional contemporaneous bimodal intrusive rocks, volcanic rock suites and A-type granitoids, indicating they formed in the Early Jurassic extensional tectonic setting. Combined with the genetic understanding of A-type granite in the Nanling at the same time as Bankeng granites, this paper suggests that the thermal anomaly generated by the upwelling of deep asthenosphere in the Early Jurassic caused partial melting of REE-rich rocks in the crust-mantle magmatic source area to form more REE-enriched A-type granitic melt, which may be one of the important mechanisms for the petrogenesis of ore-forming parent rocks of the ion-adsorbed light REE deposits in South China. The genetic correlation between the LREE-riched Bankeng granites and the HREE-riched Zudong granites shows that the petrogenesis of the LREE-type ore-forming parent rocks is mainly related to their magma source region and extensional tectonic setting, while the degree of magma crystallization differentiation and the external fluid metasomatism are more critical for the petrogenesis of the HREE-type ore-forming parent rocks.
The Dabaoshan deposit is a large-sized polymetallic deposit within the Qin-Hang Metallogenic Belt, and it is still controversial whether there has been submarine exhalative sedimentation. In this study, we conducted isotopic dating and in-situ elemental analysis of various sulfides in the deposit, having obtained Re-Os isochron age of (366±33) Ma for pyrrhotites and Rb-Sr isochron age of (166.3±2.5) Ma for sphalerite, respectively. The pyrrhotite is characterized by low concentrations of Co and Te, and high concentrations of Ni and Se, with Co/Ni ratios predominantly below 1, indicating a sedimentary origin. Additionally, sphalerite is relatively enriched in elements such as Fe, Mn, Cd, Ga, In, and Sn, exhibiting relatively low Zn/Cd and Cd/Fe ratios, low Co content, and high Sn content, indicating a sedimentary exhalative origin. Generally, the Dabaoshan polymetallic deposit experienced mineralization through Devonian exhalative sedimentation mineralization, followed by Jurassic magmatic-hydrothermal superimposition. The Re-Os isotope system of sulfides remained stable at a mineralization temperature around 400 ℃, preserving the in-situ geochemical signatures of the initial sedimentary processes. The findings provide valuable insights into the genesis of massive sulfide deposits in South China.
Extremely negative inorganic carbon isotope values (δ13CV‒PDB<‒40‰) from the Ediacaran Doushantuo cap dolostone in East Yangtze Gorges were taken as key evidence for a methane release event, but the origin of the cap dolostone remain contested. Here we investigated carbon, oxygen, sulfur, and strontium isotopes, and major and trace element compositions in both authigenic carbonates and dolostones from the Doushantuo cap dolostone at the Jiulongwan Section. Authigenic carbonates show extremely negative inorganic carbon isotope values, remarkably wide ranges of sulfur isotope values for sulfates and pyrites, a positive δ18O(CAS, Brt)-δ34S(CAS, Brt) correlation with a low slope, and a distinctly negative Δ33Spyrite-δ34Spyrite correlation, which indicates that the extremely 13C-depleted carbonates were deposited from seawater via anaerobic oxidation of methane coupled to microbial sulfate reduction (AOM-MSR) at paleo-marine cold seeps. Redox-sensitive elements reveal that the authigenic carbonates (JF1 and JF2) were deposited in an anoxic condition, while the whole cap dolostone was deposited in transitional conditions of suboxic-anoxic-suboxic-anoxic-suboxic. Paleodepth indicators imply that the sea level in the Jiulongwan area dropped during the JF1 and JF2 stages, respectively. Results of major and trace elements and strontium isotopes demonstrate that the input of terrigenous weathered materials increased during the JF1 and JF2 stages. In Early Ediacaran Epoch, two regressions in the Jiulongwan area resulted in an anoxic environment and altered hydrochemical conditions, which is an important origin for the extremely negative inorganic carbon isotopes observed in the cap dolostone in this area.
The main marine reptiles spread over the eastern Paleotethys and western Panthalassa Ocean during the biotic recovery in the Early Triassic. The Nanzhang-Yuan'an fauna is one of the earliest marine reptiles in the Early Triassic. However, the specific survival time of this fauna and the fossil-bearing Jialingjiang Formation is still not well defined. Here, it conducted litho-stratigraphy and isotopic dating on the Nanzhang-Yuan'an fauna in the Nanzhang-Yuan'an area of Hubei Province. The fauna is documented in the laminated limestone of the upper Jialingjiang Formation, with a SHRIMP Ⅱ U-Pb age of 247.8±1.2 Ma. The stratigraphic framework for the upper part of the Jialingjiang Formation was established, proving that the Nanzhang-Yuan'an fauna lived in the late Spathian stage of the Early Triassic.
As a product of collision orogenic belt, leucogranites are not only closely related to rare metal mineralization, but also have great significance to orogenesis and plateau uplift mechanism. The petrogenesis of leucogranites is still controversial. Earlier studies suggested that leucogranites were generated by low-degree in-situ partial melting of metasedimentary rocks, but in recent years, more scholars have pointed out that they may be highly fractionated granites, and the magma had undergone an intensive fractional crystallization. In order to explore the petrogenesis of leucogranites, we collected Lalong leucogranites and their sedimentary surrounding rocks (marbles and slates) in the eastern Himalayan orogenic belt to analyze the major and trace elements, Sr-Nd isotopes and monazite U-Th-Pb dating. Lalong leucogranites are located in the core of the Lalong dome, where two-mica granites, muscovite granites and albite granites are exposed in turn from inside to outside. The dating results show that these three leucogranites have similar emplacement ages (22-23 Ma). Generally, the leucogranites show high SiO2 (73.0%-75.7%), high K2O (3.50%-6.53%), low MgO (0.03%-0.22%) and peraluminum (A/CNK=1.05-1.24). From two-mica granites through muscovite granites to albite granites, the negative Eu anomalies became intensified, Rb, Rb/Sr and Y/Ho gradually increased, while Sr, Ba, K/Rb and Zr/Hf gradually decreased. In addition, these leucogranites have consistent Sr-Nd isotopic compositions: (87Sr/86Sr)i=0.736 456-0.737 929, εNd(t)=-12.4 to -12.1, which are more depleted than that of the surrounding rocks (εNd(t)=-16.9 to -15.1). Two-mica granites have consistent Sr-Nd isotopic compositions with the higher Himalayan crystallines, the high CaO/Na2O ratio values (0.33-0.42) and Al2O3/TiO2 ratio values (197-459), indicating that their source region is dominated by clastic rocks. The spatial distribution characteristics in the field and data results show that the Lalong leucogranites may have originated from muscovite dehydration melting of metagreywacks in higher Himalayan crystallines, which had undergone certain degree of fractional crystallization rather than generated by in-situ partial melting of metasedimentary rocks. The trace element Rayleigh fractionation modeling results also prove that when two-mica granite is used as the initial melt, it could generate muscovite granites and albite granites after fractional crystallization of about 70% and about 90%, respectively. Considering the overlapping relationship between the South Tibetan Detachment System and the Lalong leucogranites, this paper considers that the South Tibetan Detachment System may have triggered partial melting of the leucogranites source region by decompression and provided space for the flowage differentiation of the leucogranites.
To understand the Mesoproterozoic geotectonic evolution of the northern margin of the Yangtze Craton, the U-Pb dating of detrital zircons from the sedimentary strata of the Kuangshishan, Shicaohe, and Taizi formations within the Shennongjia Group has been conducted. The results reveal prominent detrital zircon age peaks at ~1.60 Ga, 2.00-2.10 Ga, and 2.50-2.70 Ga, with minor populations at 2.20-2.30 Ga and rare zircons older than 2.80 Ga. The age distributions suggest that the Shennongjia Group was deposited between 1.10 and 1.60 Ga.Comparative analysis of detrital zircon age spectra from Mesoproterozoic strata across the Yangtze Craton and its continental nucleus indicates distinct age distributions between the western and northern margins, implying relatively independent tectonic evolutionary processes during the Mesoproterozoic. While the Shennongjia Group and the Dagushi Group exhibit similar age spectra, their differing peak ages in the 1.40-1.60 Ga interval suggest divergent evolutionary histories during this period. Integrating the findings with those of the previous studies, we propose that the Yangtze Craton likely comprised multiple independent microcontinents before the Mesoproterozoic, which were progressively amalgamated into the cratonic basement during Paleoproterozoic to Mesoproterozoic tectonic events.
The late Archean (3.0-2.5 Ga) is a pivotal period when the composition of the continental crust and the tectonics style significantly changed. Abundant Mesoarchean granitoids, including TTG gneisses and potassic granitoids, occur in the Wengmen complex within the southern Dabie Orogen, part of the North Yangtze Block. Here, it presents major and trace elements, zircon U-Pb ages and Lu-Hf isotopes of these granitoids, which were integrated to determine their petrogenesis and constrain the crustal evolution of the Yangtze Block. The TTG gneisses and potassium granite veins have similar emplacement ages from 2 927 Ma to 2 917 Ma. The TTG gneisses can be divided into two types: low-HREE type and high-HREE type. Compared with the typical Archean TTGs, the low-HREE TTGs have moderate SiO2 and Na2O content, lower Mg#, Ni, Cr contents and Sr/Y ratio, showing the characteristics of low pressure TTGs. The high-HREE TTGs have lower Mg#, Ni, Cr contents and a very low Sr/Y ratio, which should belong to the transitional TTGs. The potassic granite veins are characterized by high SiO2, K2O, high K2O/Na2O (0.81-1.09) and iron-rich, exhibiting a left-leaning "V-type" seagull-type rare earth distribution pattern, indicative of highly differentiated granites. Their magmatic oxygen fugacity and water content resemble those of modern arc magmas. Zircons from the TTG gneisses gave εHf(t) values of -3.7-+1.5 and Hf crustal model ages (TDMC) of 3.56-3.23 Ga, whereas those from the potassic granites show εHf(t) values of -4.3-+0.2 and TDMC ages of 3.58-3.31 Ga. The coeval occurrence of TTGs and K-rich granitoids of the Wengmen complex within the southern Dabie Orogen marks the development of plate tectonics, the maturation of the continental crust and initial cratonization of the North Yangtze Block during the Mesoarchean.
Granite related lithium deposits are generally characterized by high radiogenic heat productions. However, the genetic relationship between the high heat producing granites (HHP) and Li mineralization is poorly understood. In the study, the newly discovered giant Yifeng-Fengxin granite related lithium ore field in West Jiangxi Province was selected to further constrain the relationship between the HHP and Li mineralization. Petrology and major and trace elemental geochemistry were carried out on Li-related granites, including biotite granite, two-mica granite, muscovite granite, and lepidolite granite. The results show that all the granites roughly belong to strongly peraluminous and high-K calc-alkaline series with obvious enrichments of SiO2, Al2O3, Na2O, K2O, and P2O5, but depletions of CaO, TiO2, MgO, and FeO*. Low Nb/Ta and Zr/Hf ratios and high 10 000×Ga/Al ratios indicate that they could be highly fractionated S-type granites. From biotite granite, two-mica granite, to muscovite granite and lepidolite granite, they underwent distinct fractional crystallization of quartz, feldspar, mica, monazite, allanite and zircon with gradually increased differentiation degree. Biotite granite exhibits the highest radiogenic heat production among all granite types due to the concentration of U and Th, and can be regarded as HHP. The high heat production of biotite granite may be inherited from its source region with some mantle magma injection. With the increase of evolution degree, the radiogenic heat production of different types of granites generally decreased while the lithium content increased gradually. In conclusion, the control of HHP on Li mineralization may be reflected in two aspects: (1) HHP and its parental magma provide the dominant source of lithium metal; and (2) radiogenic heat released by the decay of heat producing elements considerably prolongs the suprasolidus lifetime of granitic magmas, and the fractional crystallization and/or the diffusion of Li (and other metals) from melt to hydrothermal can be allowed to proceed more completely before the solidus is reached. Thus, radiogenic heat production may be another thermal drive mechanism for the rare metal mineralization of highly differentiated granite in South China. The study of HHP will enhance the understanding of the mineralization of granite-type lithium deposits and the metallogenetic relationship between Li, W-Sn, Nb-Ta, U and other metal deposits, which is expected to bring enlightenment for the prospection and exploration of these metals.
Porphyry-skarn Cu deposits are frequently characterized by high contents of dispersed elements, which exhibit significantly diversified enrichment between them. However, the regularity of the diversified enrichment remains insufficiently understood. In this study, the primary ore minerals present in the Chengmenshan deposit were investigated, using the optical microscope and scanning electron microscopy. Additionally, correlation analysis, cluster analysis, and fractal analysis were employed to explore the relationships between the dispersed elements (Te, Se, Ga, Ge, Cd, In, and Tl) and Bi contents in the drill cores. The results reveal that Te is predominantly hosted by independent minerals, with only a minor fraction incorporated into sulfides. In contrast, other dispersed elements are incorporated by at least two types of sulfide. The distribution patterns of the dispersed elements at Chengmenshan exhibit multifractal patterns, except for Tl, which follows a simple fractal distribution due to its complex occurrence. The enrichment pattern of these dispersed elements at Chengmenshan is characterized by a sequential separation and spatial dislocation. The pattern is likely influenced by metallogenic factors such as temperature, pH, fS2, and fO2, along with the distinctive geochemical properties of the dispersed elements. This research demonstrates that an understanding of the diversified enrichment regularity of these dispersed elements could be instrumental in identifying independent deposits of these elements. Furthermore, a primary halo distribution model for the dispersed elements in the Chengmenshan deposit has been developed, which may serve as a valuable reference for studying the genesis of associated dispersed element deposits and for the prospecting and exploration of deeply buried targets.
In 2021, the research group discovered the Mesoproterozoic lithium-rich sedimentary series in eastern Hebei Province. This is the first lithium-rich sedimentary record found in the Precambrian strata in China. A total of 33 lithium-rich layers were found in the exploration area, with a thickness of 1.09-5.59 m, an average thickness of 2.32 m, Li2O grade of 0.1%-0.42%, and an average grade of 0.16%. The target layer has wide distribution, huge thickness, stable horizon, and huge lithium resource potential, so it has a huge potential for lithium resources. Lithium-rich sedimentary rocks are developed in the Mesoproterozoic Wumishan Formation. Mineralogical and geochemical analyses show that dolomite is the dominant mineral with subordinate quartz, illite/smectite mixed layer, and illite. The lithium-rich rocks are characterized by high CaO, MgO and low Al2O3 contents. At room temperature and pressure, the reaction of argillaceous dolomite with dilute hydrochloric acid in a closed container can produce > 77% lithium leaching. Compared with the Late Paleozoic lithium-rich sedimentary rocks in South China, this type of lithium-rich rocks in North China has significant differences in metallogenic age, ore-bearing succession, lithology, mineral composition, major and trace elements and occurrence state. And it is also different from the former, which requires effective leaching of lithium under heating conditions. These differences are likely related to the likely derivation of the ore-forming materials of lithium-rich rocks in the study area from the weathering of Shanhaiguan ancient land and the deposition in a dry carbonate tidal flat-lagoon environment. Therefore, the formation of the lithium-rich rocks in the Wumishan Formation is different from the previously proposed carbonate clay-type lithium deposits, indicating a new lithium enrichment mechanism. The exact mechanism of lithium enrichment in this rock series still needs to be further studied.
As one of the four most famous carving stones in China, Shoushan stone is mainly produced in the Fuzhou volcanic basin and formed by alteration between acidic volcanic rocks and hydrothermal fluids. The characteristics of ore-forming fluid are the key to understanding the mineralization and exploration model. The hydrothermal quartz from Shoushan stone deposit was sampled for the experiment of fluid inclusions and H-O isotopes. The thermodynamic tool is also adopted to quantify the conditions for the formation of Shoushan stone containing kaolinite group minerals. All fluid inclusions in quartz consist of volatile-liquid phases. The homogenization temperatures are 197 ℃ and 211 ℃ for samples from Liuping sample, and 245 ℃ for that from Gaoshan. The δ18OV-SMOW values of quartz are 8.3‰ and 8.4‰, and the δDV-SMOW values of quartz are -61‰ and -83‰. Combined with the H-O isotope results of kaolinite from previous research, the H-O isotope of fluid is calculated theoretically under different temperatures (150 ℃, 200 ℃ and 250 ℃), which demonstrates that the ore-forming fluid is a mixture of magmatic and meteoric water. By the addition of meteoric water, the temperature, salinity and pH of magmatic-hydrothermal fluids, hydrothermal fluids are made more suitable for the formation of clay minerals. Then, the long-term water-rock reaction leads to the sufficient alternation of acidic volcanic rocks, forming a variety of Shoushan stones. This study improves the mineralization model of Shoushan stone and provides insights into the exploration of metallic and non-metallic deposits caused by epithermal hydrothermal alteration.
Phosphorus (P) and aluminum (Al) are respectively recognized as a critical nutrient limiting element for biological processes and a significant metallic element. Within the near-surface environment, rock weathering is the predominant mechanism facilitating the release of these elements. Basalt, featuring abundance of phosphate mineral minerals (including basaltic glass and apatite) and aluminosilicate minerals (such as feldspar and pyroxene), constitutes a substantial rock reservoir for both P and Al elements. Despite the importance of these elements, a comprehensive understanding of the behavior of P and Al during basalt weathering remains an area ripe for further investigation. To enhance the understanding of the chemical weathering process of basalt, this study undertook a detailed examination of the weathering profile within the Emeishan Large Igneous Province(ELIP), employing mineralogical, geochemical, and phosphorus form analyses. Additionally, by integrating published data on basalt weathering profiles, the study explores the control mechanisms of physical erosion on the weathering leaching of P and Al elements and analyzes the weathering-deposition mineralization effects related to the Late Permian period.The basal section of Heishi weathering profile is characterized by a semi-weathered layer that is rich in primary minerals, including a substantial quantity of feldspar. Relative to the basaltic parent rock, this layer exhibits a markedly enhanced degree of chemical weathering, as indicated by Chemical Index of Alteration (CIA) values of 40 for the parent rock and a range of 72 to 83 for the semi-weathered layer. The upper section of the profile comprises a soil layer that incorporates quartz, hematite, and various clay minerals, reflecting an advanced stage of weathering, with CIA values that extend from 90 to 92. Utilizing the stability of Ti and normalization to the parent rock for calculating the mobility of elements, the results indicate that there is a varying degree of loss of Na, Ca, Mg, P, and Eu from the bottom up. Fe, K, and Ce show significant depletion in the semi-weathered layer but are relatively enriched in the soil layer. Al is relatively depleted in the soil layer, while Zr is relatively enriched.The soil layer, characterized by high quartz content and a low Ti/Zr ratio, likely indicates the influence of aeolian input from feldspathic dust.A binary mixing curve was constructed based on the composition of the weathered black stone protolith and aeolian dust, revealing that the weathering profiles have relatively low P/Ti ratios, while the Al/Ti ratio only shows a decreasing trend in the soil layer. This pattern suggests that P is significantly (> 50%) leached during the early stages of weathering, and the state of phosphorus in the residual soil undergoes a transition from dissolved phosphorus in the protolith to weakly adsorbed phosphorus and then to strongly adsorbed phosphorus. Under extreme weathering conditions, Al can be partially (> 20%) mobilized and lost through the percolation and leaching of acidic fluids, Al-rich clay minerals, or complexes. The degree of weathering at the surface is contingent upon the relative rates of physical erosion and chemical weathering. When erosion rates are high, a greater exposure of weakly weathered rocks occurs, which favors the weathering and leaching of P. Conversely, when erosion rates are low, a more extensive development of intensely weathered soil layers takes place, which favors the weathering and leaching of Al. Integrating the weathering trends of Late Permian basaltic mudstones in the western South China, it is posited that the weathering and erosion conditions of the ELIP are significant factors controlling the weathering-deposition enrichment of P and Al.
The magmatic activities in the Early Paleoproterozoic are of great significance for understanding the tectonic evolution history and geodynamic processes of the Trans-North China Orogen (TNCO) in the North China Craton (NCC). In this study, the Early Paleoproterozoic diabase-gabbro was discovered for the first time in the Luobuqigou area of southern Chifeng at the northern end of the TNCO, and detailed petrography, whole rock geochemistry and zircon U-Pb-Hf isotope geochemistry studies were carried out. Zircon U-Pb isotopic dating reveals that the intrusion age of diabase-gabbro is 2 332 Ma. The geochemical characteristics indicate that the diabase-gabbro belongs to the tholeiitic basalt series. It shows positive anomalies of Rb, Ba, U and Pb, and negative anomalies of Sr, Nb, Th and Y. It has a relatively gentle right-dipping REE distribution pattern, with a weak enrichment of LREE relative to HREE, and the Eu anomaly is not obvious. Zircon εHf(t) value ranging from -4.4 to -0.8, and the single-stage Hf model age tDM1 range from 2 722 Ma to 2 873 Ma. Petrogenetic studies have shown that the diabase-gabbro magma originated from the enriched subcontinent lithosphere mantle with the participation of the asthenospheric mantle. The enriched mantle source is a 10% to 20% partially melted spinel- and garnet-bearing lherzolite mantle. Its magma evolution is dominated by the fractional crystallization of clinopyroxene, followed by olivine and plagioclase, and the influence of crustal contamination was limited. The comprehensive study shows that the ~2.33 Ga diabase-gabbro in the Luobuqigou area of southern Chifeng at the northern end of the TNCO during the Early Proterozoic tectono-magmatic lull (TML) period, might beformed in a back-arc extensional rift environment. The study area might have experienced the geodynamic process of asthenosphere upwelling and lithosphere thinning caused by plate rollback. Our research results provide constraints and references for the tectonic evolution of the northern end of the TNCO in the NCC during the Early Paleoproterozoic.
The Late Paleozoic is the key period of ocean basin evolution in South Tianshan. By studying the Late Paleozoic sedimentary records, we can restore Late Paleozoic paleogeography and reveal tectonic evolution history of the South Tianshan. The Devonian strata are well preserved in the Biedieli area of Southwest Tianshan, as an important carrier for the study of the early Late Paleozoic tectonic evolution of the South Tianshan. In this paper, in order to reveal their source and geological significance, we study the geochemical characteristics, heavy mineral characteristics and geochronological data of sandstone in Lower Devonian Apadalkan Formation. The CIA and ICV of sandstone are 63.1 and 1.19, respectively, showing that the sandstone belongs to intermediate weathering and has experienced sorting and recycling. The heavy minerals are mainly zircon, apatite, rutile, etc., and their sorting and roundness are poor. The ATi and ZTR index is 20.0-47.2 and 20-60, respectively, indicating the volcanic rocks in the source area of the Apadalkan Formation were abundant, and their transportation distance was relatively short. The geochemical provenance analysis diagram and heavy mineral characteristics indicate that the source rock is mainly felsic magmatic rocks, followed by recycled ancient sediment components. According to the LA-ICP-MS U-Pb ages of detrital zircon grains, the source rocks of Apadalkan Formation are derived from terrains with five different geological periods, mostly 407-486 Ma and 669-959 Ma, and subordinately 1 190-1 476 Ma, 1 782-2 094 Ma and 2 300-3 660 Ma, indicating that source rocks are mostly derived from Early Paleozoic and Neoproterozoic, followed by Neoarchean, Paleoproterozoic and Mesoproterozoic. They are equivalent to magmatic event on the northern margin and the Precambrian basement of the Tarim. It also indicates that the materials of Apadalkan Formation are mainly derived from the northern margin of Tarim. The Tectonic discriminant diagrams show that the Apadalkan Formation is a product of an active continental margin environment.
The India-Eurasia collision and the uplift of the Tibetan Plateau have profoundly changed the topography and climate patterns of Asia, triggering reorganization of large river systems. Recently, the evolution of large rivers on the northern South China Sea has become a frontier and hot issue in geoscience research. Offshore oil and gas exploration and the implementation of the International Ocean Drilling Program (IODP) have provided continuous and accurately dated sedimentary records for reconstructing the evolution of major rivers in South China. This paper reviews the sedimentary provenance investigations of the Cenozoic basins in the northern South China Sea in the past two decades, and discusses the progress in the evolution of major rivers in South China, such as the Red and Pearl Rivers. Provenance research in the Yinggehai Basin shows that the Red River has been the main supplier since the Late Eocene; and there are differences in provenance signals between the Yinggehai and large rivers of the Tibet Plateau (including the Nujiang, the Lancang and the Yangtze Rivers, indicating that they have not flowed into the Yinggehai Basin since the Late Eocene. During the Eocene to Early Oligocene, the Pearl River Mouth Basin was mainly supplied by the South China, indicating that the Pearl River was relatively small. Driven by the opening of the South China Sea in the Late Oligocene, the Pearl River expanded westward to the southeastern Tibetan Plateau. Cenozoic stratigraphy in Taiwan records that the ancient Minjiang River expanded westward to the Wuyi Mountain in the Late Oligocene. This evidence shows that the opening of the South China Sea controlled the evolution of the large rivers in South China.
The initiation time, the duration and the magnitude of oxygen increase of the Neoproterozoic Oxygenation Event (NOE) are controversial. The sequence and causal relationship between the NOE and the Snowball Earth also need to be clarified. This review analyzes previous studies of fossils, geochemical data and models in the Tonian, suggesting a hypothesis of possible linkages between the NOE and the Snowball Earth. The NOE may have occurred earlier than the Snowball Earth, and the end of Snowball Earth further promoted an increase of oxygen content. Specifically, eukaryotic algae were widely present during the Tonian and constructed a basis for high productivity. Rifting of the Rodinia supercontinent triggered intense continental weathering, leading to a large amount of nutrients such as phosphorus into seawater. Consequently, enhanced primary production elevated the burial of organic matter, and sufficient oxygen was released to the ocean and atmosphere, indicating the onset of the oxygenation event. On the other hand, abundant O2 and intense continental weathering consumed greenhouse gases such as CH4 and CO2, causing a decrease of temperature and driving the Snowball Earth. During the interglacial and postglacial periods of the Snowball Earth, glacier melting caused strong physical weathering and enhanced nutrient supply, improving organic carbon burial and O2 level. To clarify the interactions between the NOE and the Snowball Earth, it is necessary to further study chronology, paleontology and geochemistry of the Tonian in the future.
Devonian is one of the key intervals in the Earth history and a critical period of many geological events, including great changes of climate system of the Earth, more than 25 global sea-level fluctuations, mass extinction/turnover events, closure and subduction of the Paleo-Asian Ocean, bidirectional subduction of paleo-Tethys ocean etc. Thus, it is of great significance to establish the Devonian tectonic-stratigraphic realms and lithostratigraphic framework in China. Based on the analyses of the reconstruction of global ocean and continent, ocean plate sequence distribution and characteristics of subordinate suture zone and main suture zone of orogenic belt, integrity and contact relation of striatigraphic sequence, paleobiogeographic province, tectonic-lithofacies paleogeographic framework etc., the Devonian tectonic-stratigraphic realm in China is divided into 12 super-realms and 47 realms, and the diagram of Devonian tectonic-stratigraphic realms was made. The 12 super-realms of the Devonian respectively are: Altai-Xing'an-Mongolian super-realm, Jiamusi-Xingkai super-realm, Irtysh-Xar Moron super-realm, Tianshan-Junggar super-realm, South Tianshan-Mazongshan super-realm, Tarim-North China super-realm, Qilian-Qinlin super-realm, West Kunlun-Buqingshan-Mianlue super-realm, Qiangtang-Sanjiang suoper-realm, Bangonghu-Shuanghu-Changning-Menglian super-realm, Gangdese-Himalaya super-realm and South China super-realm. On the adequately gathered data of the stratigraphic sequence, the lithostratigraphic framework or each tectonic-stratigraphic realm is established.
As oil and gas exploration extends into deep and ultra-deep areas, well logging is faced with great technical challenges such as ultra-high temperature and high pressure, harsh wellbore environment and low signal-to-noise ratios. Addressing difficulties in logging evaluation of deep/ultra-deep carbonate reservoir, this paper focuses on four key technical problems that restrict the exploration and development of deep and ultra-deep carbonate fields in China: lithology and lithofacies identification, characterization of effective fracture-cave reservoirs, fluid property identification and evaluation of subsurface fracture-cave reservoirs. In order to solve these problems, based on the core-calibrated image logging, the key image features corresponding to different rocks are identified, and the logging lithofacies identification method under the core constraint is formed. Based on in-depth analysis of typical logging response characteristics of effective fracture-cavity reservoirs, a method for identifying and quantitatively characterizing fractures and solution holes is established. For the high-resistivity background formation, the accurate identification of reservoir fluid properties under oil-based mud conditions is realized by re-processing the array induction logging data. The acoustic reflection imaging technology was used to identify the hidden fracture-cave reservoirs within 3-50 m of the borehole, expanding the radial detection scope Consequently, a technical framework for logging evaluation of deep/ultra-deep carbonate reservoirs⁃centered on imaging logging technologies has been developed, which reflects the innovation and development of logging evaluation technology.
This study aims to reveal the development characteristics and controlling factors of deep favorable reservoirs in the Lower Third Member of the Shahejie Formation (Es3L) in the Yangwuzhai Block of the Raoyang Sag, Jizhong Depression, Bohai Bay Basin. The reservoir heterogeneous properties and the genetic mechanisms are investigated by an integrated approach combining sedimentological and diagenetic analysis, thin section petrography, scanning electron microscopy (SEM), cathodoluminescence (CL), and porosity-permeability measurements. The results indicate that the Es3L reservoirs are dominated by lithic arkose, with average porosity and permeability values of 10.8% and 8.79 mD, respectively, which are generally classified as low-porosity and ultra-low-permeability reservoirs. The reservoirs are at the middle diagenetic stage A2, with complex diagenetic processes including compaction, cementation, and dissolution. Three main reservoir types were identified: (1) tightly cemented reservoirs with strong carbonate cementation, (2) dissolution-enhanced reservoirs with secondary porosity, and (3) primary pore-preserved reservoir. The tightly cemented reservoirs are mainly developed in thin, sheet-like sand bodies of lobe microfacies, characterized by frequent interbedding of sand and shale, with intense carbonate cementation. The dissolution-enhanced reservoirs occur in thin-bedded sand bodies associated with distributary channels of gravity flows, showing a diagenetic sequence of moderate compaction followed by intense dissolution. These reservoirs exhibit high porosity but poor permeability, owing to weak late-stage hydrocarbon charging and limited carbonate dissolution. In contrast, the primary pore-preserved reservoirs are developed in the middle parts of thick sand bodies within gravity flow channel microfacies, and exhibit diagenetic features of chlorite grain-coating, moderate compaction and weak carbonate cementation. Strong late-stage hydrocarbon charging inhibited further carbonate cementation, resulting in relatively favorable reservoir quality. These findings provide valuable insights for deep hydrocarbon exploration in the Yangwuzhai area and other regions with similar geological settings.
To enhance the fundamental scientific understanding of fine-grained sedimentation in saline lacustrine basins and to expedite shale oil exploration in China, this study focuses on the Eocene saline lacustrine sediments (the upper member of the Lower Ganchaigou Formation) within the Qaidam Basin, summarizing previous research insights regarding the development mechanism of high-quality source rock and the enrichment process of shale oil and discussing existing deficiencies that require urgent attention. The Qaidam Basin is a saline lacustrine basin situated within a mountainous plateau, characterized by a complex hydrocarbon-generating organism composition that includes three primary categories: algae, bacteria, and higher plants. Notably, Botryococcus braunii blooms under conditions marked by intermittent warm-humid climates and nutrient-rich diluted water column, demonstrating a clear responsive relationship with high-quality source rock development. The "relatively eutrophic", "moderate salinity", and "appropriately anoxic" environments promote elevated primary productivity alongside suitable preservation conditions that collectively enhance organic matter accumulation within the saline lacustrine basin.Saline lacustrine source rocks exhibit a characteristic "two-stage" hydrocarbon generation process; soluble organic matter generates oil during immature stages while kerogen produces oil during mature stages, thereby establishing a material foundation for shale oil enrichment from a sourcing perspective. Well-developed layered calcareous dolomite with favorable physical properties ensures large-scale shale oil accumulation from a reservoir standpoint. Diverse source-reservoir combinations dictate differential enrichment patterns of shale oil; specifically, integrated-type shale oils accumulate through self-generation and self-storage processes exhibiting high hydrocarbon contents, whereas differentiated-type shale oils rely on micro-migration for accumulation but display lower overall hydrocarbon contents despite possessing higher light component content.The sub-salt zone within the upper member of the Lower Ganchaigou Formation represents an essential stratum for developing high-quality source rock and serves as a critical layer for contemporary shale oil exploration and production. However, its thickness exceeds 1 200 meters, and it has become a focus of research to further pinpoint the sweet spot of shale oil. The distinctive formation background of the Qaidam Basin serves as a paradigmatic case for researching the development mechanism of source rocks and the enrichment process of shale oil under extreme water body circumstances. Numerous scientific challenges necessitate comprehensive investigation, including cycling pattern of lake nutrient elements under the condition of high-salinity water medium, the differential enrichment mechanism of organic matter in diverse salinization stages, the synergistic variation patterns between biological systems and environment and their influence on the quality of source rocks, the hydrocarbon generation process and reservoir formation model within extremely thick shale sequences and their dissimilarities, as well as the occurrence and enrichment mechanisms of shale oil associated with diverse source-reservoir combinations, etc. All these are of significant importance for further clarifying the development mechanism of shale sequences in the Qaidam Basin and facilitating the increase of reserves and production of shale oil.
The sound velocity of deep-sea sediments is fundamental for constructing the acoustic field of the marine environment. This article tests and analyzes parameters such as longitudinal wave velocity, wet density, porosity, and median particle size of sediment column samples obtained from the deep waters of 4 818-6 630 m in the West Philippine Sea. It elucidates the basic characteristics and vertical variations of acoustic and physical parameters of seabed sediments in the study area, explores the relationship between physical parameters and sound velocity, compares measured data with empirical equation predictions, and proposes four typical sound velocity structures of seabed sediments in the study area. The results show that the longitudinal wave velocity distribution of sediment ranges from 1 460 to 1 674 m/s, the porosity ranges from 62.07% to 69.54%, the wet density varies from 1.34 to 1.62 g/cm3, and the median particle size varies from 7.75 to 8.40 Φ. The sediment parameters in the study area vary with depth, and density has a better effect on sound velocity than porosity and median particle size. By comparing the sound velocity of the bottom seawater, the sound velocity profile within the same layer, and the sound velocity of the lower surface of the upper seabed sediment, four types of sound velocity structure models were established in the research area, involving low velocity surface-low velocity layer-sound velocity reduction type (GMI1), low velocity surface-high velocity layer-sound velocity increase type (GMI2), high velocity surface-low velocity layer-sound velocity rreduction type (GMII1), and high velocity surface-high velocity layer-sound velocity increase type (GMII2).There are significant differences in the acoustic characteristics and sound velocity gradient changes of sediments in the southern (Zone A) and northern (Zone B) regions of the Central Rift Valley. Zone A can be divided into GMII1 and GMII1-GMI1 types, while Zone B can be divided into GMI2 and GMI1-GMII2 types.
Underground Karst formations pose significant safety risks to the design, construction, and safe operation of land transportation projects. To investigate the development of underground karst, comprehensive multi-source heterogeneous survey data were utilized, including remote sensing interpretation, engineering geological mapping, drill hole data, and the results from electrical resistivity tomography and transient electromagnetic methods. These data were unified in terms of temporal and spatial coordinates and standards to achieve data-level fusion of adverse karst geological bodies. Based on this foundation, a recognition framework for underground karst geological bodies was established. A method for assigning initial basic probability assignment (BPA) functions to underground spatial point domain was developed, and a modified Dempster-Shafer (DS) evidence theory algorithm based on Kendall's correlation coefficient was employed for multi-source data fusion to obtain karst evaluation indices. After 3D spatial interpolation, 3D imaging of karst features was plotted. The results indicate that the improved DS algorithm effectively solves the conflicts among comprehensive survey evidence, enabling intelligent decision-making regarding karst targets. The improved DS algorithm facilitated the integration of karst geological information features from comprehensive survey results. The 3D imaging of the integrated results enhanced the reliability and accuracy of underground karst geological body investigations, increasing work efficiency by 30% or more, and providing methodological guidance and evaluation tools for engineering design, construction, and operation.
