Search Results (42)

The Huoqiu Group is located in the southern margin of the North China Craton and is considered an Archean geologic body. Its supracrustal rocks are divided into the Huayuan, Wuji, and Zhouji formations in ascending order. The Wuji and Zhouji formations contain large BIF-type iron deposits. The BIFs show geological and geochemical features of Paleoproterozoic Lake Superior-type rather than Archean Algoma-type. The study of the formation ages and evolutionary history of the Huoqiu Terrane will provide significant guidance for the mineralization and exploration of the Huoqiu iron deposits. In this paper, we collected all available isotopic ages and Hf isotopic compositions obtained from the Huoqiu Terrane and reassessed their accuracy and geological meanings. We conclude that the Wuji and Zhouji formations were not older than 2343 Ma. Therefore, the BIFs hosted in the Wuji and Zhouji formations must be of Paleoproterozoic age. The magmatic zircons from the TTG gneisses and granite yield U-Pb ages of Neoarchean Era, indicating that the Wuji and Zhouji formations of the Huoqiu Group were deposited on an Archean granitic basement that mainly comprises the trondhjemite-tonalite-granodiorite (TTG) gneisses and granites of the “Huayuan Formation”. The Early Precambrian crystalline basement in the Huoqiu area can be divided into the Huayuan Gneiss Complex and the Huoqiu Group, comprising the Wuji and Zhouji formations. The tectonic scenario of granitic complexes overlain by supracrustal rocks in the Huoqiu Terrane has been recognized in the Songshan, Zhongtiao, Xiaoshan, and Lushan Early Precambrian terranes in the southern margin of the North China Craton. As indicated by the zircon U-Pb ages and εHf(t) data, the crustal growth of the Huoqiu Terrane occurred mainly at ~2.9 Ga and ~2.7 Ga. Based on the sedimentary age, environment, and rhythm, the BIFs in the Huoqiu region are considered to be of Lake Superior type and of great potential for Fe ore exploration. Full article

The Luanchuan Neoproterozoic gabbroic intrusions are located at the southern margin of the North China Craton (NCC), intruding into the marble and schist from the Nannihu and Meiyaogou Formations of the Neoproterozoic Luanchuan Group. The gabbroic rocks consist of plagioclase (30%–50%) and amphibole (40%–60%), with minor ilmenite (2%–5%), biotite (1%–3%), and titanite (~1%). Based on the occurrence and mineral chemistry, two types of biotites were identified. The first type of biotite (Bt I) is brown, with a fine- to micro-grained anhedral texture, occurring around the magmatic ilmenite and coexisting with titanite. Bt I is characterized by high TiO₂ and FeO contents, with TiO₂ > 2 wt% (2.03 wt%–3.15 wt%) and FeO ranging from 19.94 wt% to 22.08 wt%. The other type of biotite (Bt II) is light grayish-brown to dark reddish-brown, with a medium- to coarse-grained euhedral texture, coexisting with grayish-green amphibole. Bt II exhibits lower TiO₂ (1.40 wt%–1.90 wt%) and FeO contents (18.03 wt%–21.42 wt%). The K₂O (7.56 wt%–9.32 wt%) and SiO₂ (34.49 wt%–37.04 wt%) contents of Bt I are slightly lower than those of Bt II (8.28 wt%–9.73 wt% and 35.18 wt%–37.52 wt%, respectively). Despite the low Ti content in biotites, the mineral occurrence indicates that both types of biotite yield a magmatic origin, resulting from the reactions between early crystallized minerals and residual magma. Bt I originated from the reaction between ilmenite and residual magma, while Bt II resulted from the production of the reaction between clinopyroxne and residual magma. Ilmenite exhibits low MgO and Fe₂O₃ contents but high FeO and MnO contents, suggesting genetic similarities to the Skaergaard and Panzhihua intrusions. Both types of biotites record consistent temperatures (T = 766 to 818 °C), pressures (P = 5.30–8.80 kbar), and oxygen fugacities (log fO₂ = −12.35 to −14.06), aligning with those of the Fanshan complex and the Falcon Island intrusion. The mineralogy of ilmenite and biotite indicates that the Luanchuan gabbroic intrusions formed in a continental rift setting, which is considered to be associated with the breakup of the Rodinia supercontinent. Full article

This study investigates the provenance of the Permian Shihezi Formation (Fm) siliciclastic sediments in the Luonan area, southern margin of the North China Block, which constrain the sediment sources and tectonic evolution of the basin. Our research investigates the heavy mineral characteristics, geochemical features, detrital zircon U-Pb geochronology, and Lu-Hf isotope tracing the provenance characteristics of the Shihezi Fm in this region. Zircon yielded three distinct U-Pb age groups as follows: 320–300 Ma, 1950–1850 Ma, and 2550–2450 Ma. The ε_Hf(t) values of zircons ranged from −41 to 50, and the two–stage Hf model’s ages (T_DM2) values are concentrated between 3940 Ma and 409 Ma, suggesting that magmatic sources likely derive from Early Archaean–Devonian crustal materials. The heavy mineral assemblages are primarily composed of zircon, leucoxene, and magnetite. Further geochemical analyses of the rocks indicate a diverse provenance area and a complex tectonic evolution. Taken together, these results suggest that the provenance of the Shihezi Fm is from the North China Block, with secondary contributions from the Qinling Orogenic Belt and the North Qilian Orogenic Belt. The provenance of Luonan shares similarities with the southern Ordos Basin. Investigating the provenance of the Luonan area along the southern margin of the North China Craton provides critical supplementary constraints for shedding light on the Late Paleozoic tectonothermal events in the Qinling Orogenic Belt. Full article

North China Craton (NCC) formed the world’s largest karstic bauxite belt in the Late Carboniferous, with significant variations in metallogenic sources and conditions, which affect the overall understanding of karstic bauxite genesis. The Xiangcaowa bauxite deposit in the southern NCC is a large deposit of uncertain provenance and genesis. This study employed geological, mineralogical, and chronology analysis to investigate the sources and genesis of Xiangcaowa bauxite, further contributing to a full understanding of the origin of bauxite throughout the NCC. Xiangcaowa ore-bearing rock series is composed of bauxite and claystone layers. The composition of bauxite ore encompasses diaspore, kaolinite, anatase, pyrite, zircon, and rutile. Widely developed mineral assemblages, such as diaspore–anatase–pyrite, indicate that bauxite is mainly formed in reducing and alkaline karstic depressions. Detrital zircons, aged ~450, ~520, ~950, and ~1100 Ma, predominantly originate from igneous rocks in the North Qinling Orogenic Belt (NQOB), and the ~1650 and ~2400 Ma zircon age populations are primarily from the southern margin of the NCC. Detrital rutiles, which are concentrated in 800–510 Ma, are primarily from the metamorphic rocks of the South Qinling Orogenic Belt (SQOB); rutiles aged ~1500–910 Ma are primarily from metamorphic rocks in the NQOB. These results confirm that the principal sources of the bauxite are the igneous and metamorphic rocks within the NQOB, along with the metamorphic rocks of the SQOB, while the basement rocks of the NCC contribute only minorly to its formation. A large karstic bauxite deposit was formed by the transport of large amounts of weathered material into extensive karstic depressions where reducing and alkaline conditions favoured diaspore deposition. Full article

Critical metals in coal-bearing strata have recently emerged as a frontier hotspot in both coal geology and ore deposit research. In the Upper Carboniferous coal-bearing “Si–Al–Fe” strata (Benxi Formation) of the North China Craton (NCC), several critical metals, including Li, Ga, Sc, V, and rare earth elements and Y (REY or REE + Y), have been discovered, with notable mineralization anomalies observed across northern, central, and southern Shanxi Province. However, despite the widespread occurrence of outcrops of the “Si–Al–Fe” strata in the northeastern Qinshui Basin of eastern Shanxi, there has been no prior report on the critical metal content in this region. Traditionally, the “Si–Al–Fe” strata have been regarded as a primary source of clastic material for the surrounding coal seams of the Carboniferous–Permian Taiyuan and Shanxi Formations, which are known to display critical metal anomalies (e.g., Li and Ga). Given these observations, it is hypothesized that the “Si–Al–Fe” strata in the northeastern Qinshui Basin may also contain critical metal mineralization. To evaluate this hypothesis, new outcrop samples from the “Si–Al–Fe” strata of the Benxi Formation in the Yangquan area of the northeastern Qinshui Basin were collected. Detailed studies on critical metal enrichment were assessed using petrographic observations, mineralogy (XRD, X-ray diffractometer), and geochemistry (XRF, X-ray fluorescence spectrometer, and ICP-MS, inductively coupled plasma mass spectrometer). The results indicate that the siliceous, ferruginous, and aluminous rocks within the study strata exhibit varying degrees of critical metal mineralization, mainly consisting of Li and REY, with minor associated Nb, Zr, and Ga. The Al₂O₃/TiO₂, Nb/Y vs. Zr/TiO₂, and Nb/Yb vs. Al₂O₃/TiO₂ diagrams suggest that these critical metal-enriched layers likely have a mixed origin, comprising both intermediate–felsic magmatic rocks and metamorphic rocks derived from the NCC, as well as alkaline volcaniclastics associated with the Tarim Large Igneous Province (TLIP). Furthermore, combined geochemical parameters, such as the CIA (chemical index of alteration), Sr/Cu vs. Ga/Rb, Th/U, and Ni/Co vs. V/(V + Ni), indicate that the “Si–Al–Fe” strata in the northeastern Qinshui Basin were deposited under warm-to-hot, humid climate conditions, likely in suboxic-to-anoxic environments. Additionally, an economic evaluation suggests that the “Si–Al–Fe” strata in the northeastern Qinshui Basin hold considerable potential as a resource for the industrial extraction of Li, REY, Nb, Zr, and Ga. Full article

The newly discovered Erdaodianzi gold deposit in southern Jilin Province, Northeast China, is located in the eastern segment of the northern margin of the North China Craton (NCC). It is a large-scale gold deposit with reserves of 38.4 tons of gold. Gold mineralization in the ore district primarily occurs in gold-bearing quartz–sulfide veins. The gold ore occurs mainly as vein, veinlet, crumby, and disseminated structures. The hydrothermal process can be divided into three stages: stage I, characterized by quartz, arsenopyrite, and pyrite; stage II, featuring quartz, arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite, and native gold; and stage III, consisting of quartz, pyrite, sphalerite, galena, electrum (a naturally occurring Au–Ag alloy), and calcite. Electrum and native gold primarily occur within the fissures of the polymetallic sulfides. To determine the enrichment mechanism of the Au element and the genetic types of ore deposits in the Erdaodianzi deposit, sourcing in situ trace element data, element mapping and sulfur isotope analysis were carried out on sphalerites from different stages using LA-ICP-MS. Minor invisible gold, in the form of Au–Ag alloy inclusions, is present within sphalerites, as revealed by time-resolved depth profiles. The LA-ICP-MS trace element data and mapping results indicate that trivalent or quadrivalent cations, such as Sb³⁺ and Te⁴⁺, exhibit a strong correlation with Au. This correlation can be explained by a coupled substitution mechanism, where these cations (Sb³⁺ and Te⁴⁺) replace zinc ions within the mineral structure, resulting in a strong association with Au. Similarly, the element Pb exhibits a close relationship with Au, which can be attributed to the incorporation of tetravalent cations like Te⁴⁺ into the mineral structure. The positive correlation between Hg and Au can be attributed to the formation of vacancies and defects within sphalerite, caused by the aforementioned coupled substitution mechanism. A slight positive relationship between Au and other divalent cations, including Fe²⁺, Mn²⁺, and Cd²⁺, may result from these cations simply replacing Zn within the sphalerite lattice. The crystallization temperatures of the sphalerite, calculated via the Fe/Zn ratio, range from 238 °C to 320 °C. The δ³⁴S values are divided into two intervals: one ranging from −1.99 to −1.12‰ and the other varying from 10.96 to 11.48‰. The sulfur isotopic analysis revealed that the ore-forming materials originated from magmatic rock, with some incorporation of metamorphic rock. Comparative studies of the Erdaodianzi gold deposit and other gold deposits in the Jiapigou–Haigou gold belt have confirmed that they are all mesothermal magmatic–hydrothermal lode gold deposits formed at the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate during the Middle Jurassic. The Jiapigou–Haigou gold belt extends northwest to the Huadian area of Jilin province. This suggests potential for research on gold mineralization in the northwest of the belt and indicates a new direction for further gold prospecting in the region. Full article

Stromatolites, distinctive fossil records within Precambrian strata, are essential for investigating the depositional environments of early Earth and the geological settings conducive to hydrocarbon formation. The Luonan area is located in Shaanxi Province, China, where a large number of stromatolites have been discovered within the Mesoproterozoic Erathem, providing new perspectives on paleoenvironment and reservoir spaces. This study analyzes the morphology of stromatolites, associated microorganisms, mineralogy, and cathodoluminescence from the carbonate rocks of the Jixian System. Carbon and oxygen isotope analyses help reconstruct paleosalinity and climate, enhancing understanding of their petroleum geological significance. Combining carbon and oxygen isotope analysis with the fine observation and description of stromatolite can better reconstruct the paleoenvironmental features of the Mesoproterozoic Era. The results indicated a narrow range of carbon isotope values (δ¹³C: −5.81‰ to −2.43‰; mean: −4.03‰) and oxygen isotope values (δ¹⁸O: −9.06‰ to −5.64‰). The Longjiayuan Formation is characterized by high CaO and MgO content, with low SiO₂ and minimal terrigenous input, in contrast with the Fengjiawan Formation, which exhibits elevated SiO₂ and greater terrigenous material. The Luonan stromatolites display prominent rhythmic laminations, primarily composed of dolomite, indicating a potential for hydrocarbon source rocks. Stromatolite morphologies, including layered, columnar, and wavy forms, reflect varied depositional microfacies. The alternating bright and dark laminae, rich in CaO and CO₂ but differing in Ca²⁺ and Mg²⁺ concentrations, signify seasonal growth cycles. These Mesoproterozoic stromatolites developed in a warm, humid, and stable climatic regime, within a marine anoxic-to-suboxic setting, typically in intertidal or supratidal zones with low hydrodynamic energy. In the southern margin of the North China Craton, stromatolites from the Mesoproterozoic Era are extensively developed and exhibit distinct characteristics. Due to the biogenic alteration of stromatolites, the porosity of the rock increased. These stromatolites have altered the physical properties of the host rocks to some extent, suggesting the possibility of becoming effective hydrocarbon reservoirs. This has significant implications for deep oil and gas exploration, providing valuable guidance for future prospecting efforts. Full article

The Xiong’ershan district is situated on the southern margin of the North China Craton (NCC) and located within the Qinling–Dabieshan Orogen’s orogenic zone. It is adjacent to the XiaoQinling mining district and exhibits very favorable geological conditions for mineralization, as the district contains numerous gold deposits, positioning it as one of the key gold-producing areas of China. The Miaoling gold deposit is a hydrothermal deposit and is controlled by the Mesozoic nearly NS-trending fault. The ore bodies are hosted in the Mesoproterozoic Xiong’er Group of the Changcheng System of volcanic rocks, with reserves reaching large-scale levels. Pyrite is the main gold-bearing mineral and can be classified into four generations: early-stage fine- to medium-grained euhedral to subhedral cubic pyrite (Py1); medium- to coarse-grained euhedral to subhedral cubic granular pyrite in quartz veins (Py2a); fine-grained subhedral to anhedral disseminated pyrite in altered rocks (Py2b); and late-stage anhedral granular and fine-veinlet pyrite in later quartz veins (Py3). Through in situ trace element analysis of the pyrite using LA-ICP-MS, a positive correlation between Au and As was observed during the main mineralization stage; gold mainly exists as a solid solution within the pyrite lattice, and the ablation signal curve reflecting the intensity of trace element signals showed that gold also occurs as micron-scale mineral inclusions. The trace element content suggested a gradual increase in oxygen fugacity from Stage 1 to Stage 2, followed by a decrease from Stage 2 to Stage 3. The Co/Ni values in the pyrite (0.56 to 62.02, with an average of 12.34) exhibited characteristics of magmatic hydrothermal pyrite. The in situ sulfur isotope analysis of the pyrite using LA-MC-ICP-MS showed δ³⁴S values of 4.24‰ for Stage 1, −6.63‰ to −13.79‰ for Stage 2, and −4.31‰ to −5.15‰ for Stage 3. Considering sulfur isotope fractionation, the δ³⁴S value of the hydrothermal fluid during the main mineralization stage was calculated to be between 0.31‰ and 2.68‰. Full article

The Early Cretaceous intermediate intrusive rocks have important significance in understanding the crust–mantle interaction, iron mineralization, and tectonic evolution in the western Shandong Peninsula. In this study, we present new zircon U–Pb ages, and Hf isotope, whole-rock geochemistry, Sr–Nd isotopes, and the mineral chemistry of the diorite-porphyrite in the southern Xintai area, mid-western Shandong Peninsula. The diorite-porphyrite formed at ca. 125 Ma. They have intermediate SiO₂ (59.57–62.29 wt.%) and MgO (2.78–3.58 wt.%) contents, high Mg# values (53–56), high Sr (589–939 ppm) and low Y (9.2–10.8 ppm) contents, and high Sr/Y ratios (54–94), showing adakitic affinity. The diorite-porphyrite exhibits lower zircon ε_Hf(t) values (−30.1 to 7.5) and whole-rock ε_Nd(t) values (−3.5 to −6.0), with (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.70514–0.70567. We suggest that the diorite-porphyrite was derived from the partial melting of the local delamination of lower continental crust and then by the interaction with the enriched lithospheric mantle. The genesis of diorite-porphyrite may be related to the rollback process of the Paleo-Pacific slab in the Early Cretaceous. This geodynamic process induced the melting of the enriched lithospheric mantle, subducted oceanic crust, and local delamination of lower continental crust, which produced different types of adakitic magmatism in the western Shandong Peninsula. Full article

The Ordos Basin is located in the western part of the North China Craton. The Upper Paleozoic Shihezi Formation, particularly the He 8 Member, is one of the main gas-bearing strata. However, the source areas for the north and south sections have not been clearly distinguished, which has constrained oil and gas exploration to some extent. Therefore, understanding the source rock evolution of He 8 Member in both the south and north basins will provide a favorable theoretical basis for oil and gas exploration. The provenance of the He 8 Member of the Shihezi Formation in the Ordos Basin has not been well defined until now. Seven wellbore sandstone samples and three field outcrop sandstone samples from the He 8 Member in the Ordos Basin were analyzed. Based on zircon U–Pb dating and Lu–Hf isotope analyses, zircon assemblages of 520–386 Ma and 350–268 Ma in the southern Ordos Basin might have originated from the North Qinling Orogenic Belt (NQinOB) and the North Qilian Orogenic Belt (NQiOB); the 350–268 Ma age group of zircons from the NQinOB, and a large number of ~320–260 Ma detrital zircons supplied to the southern Ordos Basin by the NQinOB suggest that NQinOB magmatic and/or metamorphic events may have occurred in the NQinOB during the ~320–260 Ma period. From ~320–260 Ma, the NQinOB might have experienced significant tectonic activity that has not been fully revealed thus far. The zircons from 2600–2300 Ma, 2000–1600 Ma, and 450–300 Ma in the northern Ordos Basin might have been derived from the Trans-North China Orogenic Belt (TNCO), the Khondalite Belt, the Yinshan Belt, and the Alxa Belt. The paleocurrent and heavy mineral analyses determined that there are certain differences between the northern Ordos Basin and southern Ordos Basin, with unstable minerals such as barite and pyrite, as well as moderately stable minerals such as garnet, showing an increasing trend from south to north. There are also differences in the dominant paleocurrent directions between the south and north parts of the basin, and the Hf isotope data in the Ordos Basin show two-stage Hf model ages (T_DM2) ranging from 918 Ma to 3574 Ma. As a result, the He 8 Member deposits in the southern Ordos Basin and northern Ordos Basin had different sources. The southern Ordos Basin might have derived from the NQinOB, the NQiOB, and the TNCO, and the northern Ordos Basin might have derived from the TNCO, the Khondalite Belt, the Yinshan Belt, and the Alxa Belt. Full article

The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau. Full article

The thermal structure of the lithosphere is key to understanding its thickness, properties, evolution, and geothermal resources. Cratons are known for their low heat flow and deep lithospheric roots. However, present-day cratons in East China have geothermal characteristics that are highly complex, with variable heat flow values, diverging from the typical thermal state of cratons. In this study, we conducted a detailed analysis of the geothermal geological background of the cratons in East China, summarizing the thermal state and tectono-thermal processes of different tectonic units, calculating the temperature at various depths, and discussing differences in temperature and thermal reservoirs at different depths. The observed lithospheric thermal thickness within the North Jiangsu Basin and the Bohai Bay Basin is notably reduced in comparison to that of the Jianghan Basin and the Southern North China Basin. The phenomenon of craton destruction during the Late Mesozoic emerges as a pivotal determinant, enhancing the geothermal resource prospects of both the Bohai Bay Basin and the North Jiangsu Basin. Our findings contribute significantly to the augmentation of theoretical frameworks concerning the origins of heat sources in global cratons. Furthermore, they offer invaluable insights for the methodical exploration, evaluation, advancement, and exploitation of geothermal resources. Full article

The Huayangchuan U-polymetallic deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit on the southern margin of the North China Craton (NCC) in Central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area and is lacking analysis on the reasons for these situations; however, its ages, petrogenesis, and relationship with uranium mineralization are not well constrained. Zircon U–Pb ages for the hornblende-bearing granite porphyry and medium-fine-grained biotite granites in close proximity to carbonatite rocks are 229.8 ± 1.1 and 135.3 ± 0.6 Ma, respectively. High-K calc-alkaline series and weakly peraluminous Triassic hornblende-bearing granite porphyry are slightly enriched in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns, enriched in Ba and Sr, and depleted in Nb, Ta, P, and Ti, i.e., geochemical characteristics similar to those of adakite-like rocks. The Early Cretaceous medium-fine-grained biotite granites are characterized by LREE enrichment and flat HREE patterns, which belong to high-K calc-alkaline series, and metaluminous belong to weakly peraluminous I-type granite, with U and large ion lithophile element (LILE) enrichment and high field strength element depletion. The high initial ⁸⁷Sr/⁸⁶Sr ratios and enriched Nd (ε_Nd(t) = −10.7 to −9.5 and −19.9 to −18.9, respectively) and Hf (ε_Hf(t) = −21.8 to −13.0 and −30.5 to −19.0, respectively) isotopes revealed that both granitic rocks from the Huayangchuan deposit mainly originated from lower crustal materials, generated by partial melting of the ancient basement materials of the Taihua Group. Triassic hornblende-bearing granite porphyry is significantly different from the mantle origin of the contemporaneous U-mineralization carbonatite. In combination with tectonic evolution, we argue that the Qinling Orogenic Belt was affected by the subduction of the North Mianlian Ocean during the Late Triassic. The ongoing northward subduction of the Yangtze Craton resulted in crustal thickening, forming large-scale Indosinian carbonatites, U-polymetallic mineralization, and contemporaneous intermediate-acid magmatism. Additionally, due to the tectonic system transformation caused by Paleo-Pacific Plate subduction, intracontinental lithosphere extension and lithospheric thinning occurred along the southern NCC margin in the Early Cretaceous. Intense magma underplating of the post-orogeny created a large number of magmatic rocks. The tremendous heat could have provided a thermal source and dynamic mechanism for the Yanshanian large-scale U-polymetallic mineralization events. Full article

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg^# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg^# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg^# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg^# = 88.4), rind II (high-Ti-Cr, Mg^# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere. Full article

The DL deposit is a typical tabular-shaped U deposit hosted in sandstones of the Upper Cretaceous Yaojia Formation in the southwestern Songliao Basin, northeast China. Owing to its recent discovery, the origin of the deposit remains unclear. In this study, mineralogical and geochemical data were used to constrain the genesis of the DL deposit. Two sources of U were recognized: (1) pre-ore U enrichment in the Yaojia Formation during diagenesis; and (2) the provenance of the Yaojia Formation, which comprises late Permian–Early Cretaceous granitic rocks from the southern Great Xing’an Range and northern margin of the North China Craton, rather than the oils and diabase dikes in the study area. Mineralogical and geochemical characteristics indicate that organic matter (OM) in the Yaojia Formation was derived mainly from plant debris and hydrocarbons. In situ S isotope data for pyrite from the ore-bearing sandstones show that most of the pyrite has similar δ³⁴S values (−43.8‰ to −20.6‰) to those of pyrite associated with bacterial sulfate reduction (BSR). The pyrite is often typically replaced and/or overgrown by pitchblende, which has a high P₂O₅ content (0.07–1.64 wt.%), indicative of a genetic relationship between BSR and U mineralization. The geological, mineralogical, and geochemical features suggest that the U mineralization in the DL deposit was mainly associated with BSR. Full article