Deposits In China Research Articles

Determining rainwater dissolved organic carbon to reveal atmospheric carbon deposition in China's karst city: Variations, origins, and deposition flux

A large amount of organic carbon (OC) in the atmosphere are transferred to the Earth's surface through dry (40%) and wet (60%) deposition. Therefore, wet deposition is an important physical pathway for the removal of atmospheric OC. Identifying the variations of DOC in wet deposition (rainwater) is essential for clarifying the earth-surface C balance. The present study detected the DOC content in 96 daily rainwater samples collected over an entire year in a karst city, with abundant rainfall in Southwest China. The DOC concentrations varied between 1.03–37.7 mg C L−1, while the VWM value stood at 2.76 mg C L−1, which is similar to the worldwide and Asian averages. The yearly DOC wet deposition flux was calculated as 2.88 g C m−2 yr−1. Both the VWM concentration and flux of rainwater DOC exhibit pronounced seasonal variations and regional differences, primarily controlled by precipitation and the external input of OC. The sources of rainwater DOC were multifaceted, including urban waste emission, agricultural activities, and fossil fuel combustion (especially coal combustion), while the contribution from natural sources was limited. Additionally, the C: N (2.08) ratio of rainwater is significantly lower than the Redfield ratio (6.625), indicating the importance of considering the impact of nutrient components in rainfall on the material cycling of surface water ecosystems. This work will benefit the knowledge of the present status of rainwater DOC and its deposition flux on the karst regional scale and further on a global scale, and contribute to a better understanding of the C geochemical cycle on the territorial system.

Generalized Yang Chizhong filtering and interpolation method without stationarity assumption

The stationarity assumption of geostatistical methods is difficult to satisfy in practice. To overcome this limitation, this study proposed a geometric and statistical coupling strategy for modeling spatial dependence structures and developed a generalized Yang Chizhong filtering and interpolation (GYangCZ) method without the assumption of stationarity. In this work, we theoretically prove the effectiveness of Yang Chizhong filtering in fitting spatial dependence structures from a geometric perspective, and develop an orientation-constrained Yang Chizhong filtering to fit the local and discontinuous spatial dependence structures. To measure nonstationary spatial dependence structure, we define a local statistical indicator (i.e., fundamental variation function) by comparing the variance of the original data and the fitted geometric surfaces obtained under different filtering radii. The fundamental variation function is used as the kernel function to obtain the approximate best linear unbiased estimators at unobserved locations. We theoretically demonstrate that when only a linear drift exists in local areas, GYangCZ does not require the stationarity assumption. GYangCZ was used to estimate the gold grade of the Xiadian gold deposit in China. The results show that GYangCZ outperformed ordinary kriging, moving window kriging, and kriging convolution networks. GYangCZ is easy to implement with wide applications in geoscience.

Influence of Reservoir Microstructure on the State of Residual Oil According to Nuclear Magnetic Resonance (NMR) Spectroscopy

The influence of core properties on the state of residual oil in the process of oil displacement by water at the micro level is investigated. The pore size distribution, core permeability, dynamics and morphology of residual oil were studied. The analysis of the available experimental approaches to the study of the properties of the core and residual oil in the core samples showed that the existing methods do not provide complete information about the studied parameters. To solve these problems, it is proposed to use a combination of innovative relaxation-diffusion spectroscopy technology of nuclear magnetic resonance with traditional technology. A combination of mercury injection and nuclear magnetic resonance is used to measure the pore size distribution. The core permeability was determined using the nuclear magnetic resonance method. Two-dimensional nuclear magnetic resonance spectroscopy makes it possible to study the microscopic state of residual oil in an undisturbed core during the displacement process. With the help of the proposed methodology, a core study of the Shengli deposit in China was carried out. Pore size distributions were obtained, permeability and residual oil saturation at different stages of displacement were studied. Four types of residual oil are distinguished: strip-shaped (island), film, mesh, continuous. The influence of permeability on the fraction content of different types of residual oil in the process of displacement is shown. The research results demonstrate the influence of the pore space structure and wettability on the state of residual oil.

Petrogenesis of the alkaline complex in the Weishan REE deposit, Luxi Block, eastern North China Craton: Implications for REE mineralization

The Weishan REE deposit is one of the largest LREE deposits in China, which is hosted by the Weishan alkaline complex (WSAC) and late Archean gneisses. Two types of mineralization including vein-type and disseminated-type occur in this deposit, of which the former is characterized by large quartz-sulfate-calcite-REE mineral veins cutting all kinds of wallrocks, while the latter is featured by REE minerals disseminated in the alkaline rocks. The vein-type mineralization commonly occurs at shallow depths and has been numerously studied. The disseminated-type mineralization typically occurs at deeper depths, which was newly discovered by drilling exploration and has been poorly studied. In this contribution, zircon U-Pb dating and Hf isotopic analysis as well as whole-rock geochemistry and Sr-Nd isotopic analyses were conducted on the deeply drilled alkaline rocks, combined with molybdenite Re–Os dating on the disseminated ore, with the aim to unravel the petrogenesis of the alkaline rocks and their contributions to the REE mineralization. Zircon U–Pb dating suggests an intrusive age of 119.9 ± 0.9 Ma for the WSAC, which is quite consistent the Re–Os age of 120.0 ± 1.8 Ma for the disseminated ore, corroborating their close genetic correlation. The studied alkaline rocks show enrichment of LILEs, depletion of HFSEs and strong fractionation between LREEs and HREEs, indicating a crustal involvement in the magmas or a metasomatized mantle source. They are characterized by higher Hf (εHf(t) = -6.7 to −12.2) and Nd (εNd(t) = -8.8 to −9.7) isotopic compositions compared with those of the contemporaneous subcontinental lithospheric mantle (SCLM). Based on the above features, it is inferred that the parental magmas of the WSAC were mainly derived from an enriched SCLM with some involvement of asthenospheric mantle-derived materials. The mantle source was likely metasomatized by the subducted Paleo-Pacific oceanic plate, leading to the enrichment of REE and carbonate. Rollback of the oceanic slab during the early Cretaceous resulted in an extensional setting in the study region, which was favorable for partial melting of the metasomatized mantle and thus generated the REE-rich alkaline magmas.

Temporal-spatial characteristics and sources of heavy metals in bulk deposition across China

With the rapid development of industries, agriculture, and urbanization (including transportation and population growth), there has been a significant alteration in the emission and atmospheric deposition of heavy metal pollutants. This has consequently given rise to a range of ecological and environmental health issues. In this study, we conducted a comprehensive two-year investigation on the temporal and spatial distribution characteristics of heavy metals in atmospheric deposition across China based on the Nationwide Nitrogen Deposition Monitoring Network (NNDMN). The atmospheric bulk deposition of Lead (Pb), Arsenic (As), Nickel (Ni), Selenium (Se), Chromium (Cr) and Cadmium (Cd) were 6.32 ± 1.59, 4.49 ± 0.57, 1.31 ± 0.21, 1.05 ± 0.16, 0.60 ± 0.06 and 0.21 ± 0.03 mg m−2 yr−1, respectively, with a large variation among the different regions of China. The order for atmospheric deposition flux was Southwest China > Southeast China > North China > Northeast China > Qinghai-Tibet Plateau and rural area > urban area > background area. The concentrations of heavy metals in bulk deposition exhibit seasonal variation with higher levels observed during winter compared to summer and spring, which are closely associated with anthropogenic activities. The Positive Matrix Factorization (PMF) results indicated that combustion, industrial emissions and traffic are the primary contributors to atmospheric deposition of heavy metals. The single factor pollution index (Pi) of heavy metals is consistently below 1, and the composite pollution index (Ni) is 0.16 across China, indicating that atmospheric heavy metal deposition is at a pollution-free level. The comprehensive potential ecological risk index of heavy metals is 11.8, with Cd exhibiting the highest single factor potential ecological risk index at 7.09, suggesting that more attention should be paid to Cd deposition in China. The present study reveals the spatial-temporal distribution pattern of atmospheric heavy metals deposition in China, identifying regional source characteristics and providing a theoretical foundation and strategies for reducing emissions of atmospheric pollutants.

Geochemical Characteristics of Trace Elements and Mineralization Model of the Ediacaran-Early Cambrian Phosphorites, South China.

As a nonrenewable resource, phosphate rock is an important support for the development and survival of the national economy. The regional distribution and output of phosphate rock in China are extremely uneven, and the amount of high-quality ore resources is relatively poor, which seriously restricts the development and utilization of phosphate rock resources in China. This paper briefly summarizes the distribution characteristics of phosphate rock resources and summarizes the characteristics and research progress of Ediacaran-early Cambrian phosphorus mineralization types, geological characteristics, and deposit genesis of the Yangtze platform in South China. The Ediacaran-early Cambrian sedimentary phosphorite deposits in China are mainly distributed in Yunnan, Guizhou, Hubei, Sichuan and Hunan provinces of the Yangtze platform, in which the early Cambrian phosphate deposits are also rich in rare earth elements, associated with uranium, nickel, molybdenum, vanadium, and other beneficial metal elements. The increase of atmospheric oxygen content at the Ediacaran-Cambrian boundary may have promoted the extensive oxygenation of the late Neoproterozoic oceans, so the Ediacaran-early Cambrian oceans generally showed a reductive environment, and there may be dynamic chemical stratification of the oxidation zone-sulfide zone-iron zone. Up to the early Cambrian, the redox stratified structure of Precambrian seawater may still be inherited, showing that the surface water is an oxidizing environment, changing to a reduction environment, and even wedge-shaped sulfide water is developed at the bottom of the deep basin. The main phosphorus sources are deep phosphorus-rich seawater, continental weathering, and deep hydrothermal activity of Ediacaran-early Cambrian marine sedimentary phosphorite deposits in South China. The genetic mechanisms of phosphorite deposits in the Yangtze platform in South China are mainly biogenic, upwelling phosphorus-forming theory, mechanical mineralization, and syn-sedimentary hot water mixed genesis. In the future, it is still necessary to further explore the internal relationship between phosphorus deposits and major geological events, the in situ analysis of microstructure of phosphate rock ores, and the genetic mechanism of phosphate deposits and the reconstruction of paleo-marine environment.

Testibiopalladite, PdSbTe: A Valid Mineral and Sb-Analogue of Michenerite

Abstract Testibiopalladite was reported from two unnamed deposits in China by Anonymous (1974) to be ideally PdSbTe. The description of the mineral included an indexed X-ray powder diffraction pattern, space group determination, electron probe micro-analyses, reflectance, and micro-indentation hardness measurements. This description was published without prior submission to the IMA, which was the norm at the time before China became a member. It is unknown as to why the Commission for New Minerals and Mineral Names (CMNMN) did not examine and vote on the mineral as had been done for all other Chinese mineral descriptions published at the time. It is surprising because the chairman of the CMNMN at the time had reviewed the mineral (Fleischer et al. 1976) and concluded it was a valid species, i.e., the Sb analogue of michenerite (PdBiTe). Further, the same article included a description of “hexastibiopanickelite” which was voted on and rejected by the CMNMN in 1976. From 1981 to 2021 there were many papers published reporting testibiopalladite from several deposits in different countries (e.g., Hudson et al. 1978, Chen et al., 1993, Stepanets et al. 2019, 2020), as well as a single-crystal structure analysis of synthetic PdSbTe which confirmed the assigned space group (Foecker & Jeitschko 2001). The published data (e.g., Barkov et al. 2002, Liang et al. 2019, 2023) suggest that testibiopalladite is a valid mineral species, ideally PdSbTe, and is the Sb analogue of michenerite, PdBiTe, both crystallizing in space group P213. Both the name testibiopalladite and the mineral, ideally PdSbTe, were approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (CNMNC-IMA), Nomenclature Voting Proposal 23-H. Liang et al. (2019, 2023) studied samples from the type locality (Yangliuping deposit, PRC) that are to be considered as a neotype.

Giant Rare Earth Element Accumulation Related to Voluminous, Highly Evolved Carbonatite: A Microanalytical Study of Carbonate Minerals From the Bayan Obo Deposit, China

Abstract The giant Bayan Obo deposit in China represents the largest rare earth element (REE) resource in the world, but the mechanisms for its highly anomalous REE enrichment have long been controversial. The central debate concerns the nature and origin of the ore-hosting dolomite. In this study, a texturally constrained microanalytical study of carbonate minerals from the Bayan Obo ore-hosting dolomite is presented to resolve this controversy. The dolomite rocks contain two major components: the early-stage coarse-grained dolomite (CD) and the late-stage fine-grained dolomite (FD). The CD dolomite grains have C-O isotope ratios (δ13CVienna-PeeDee Belemnite (V-PDB): –4.8 to –3.3‰; δ18OVienna-standard mean ocean water (V-SMOW): 7.1 to 11.9‰) plotting in or adjacent to the primary igneous carbonatite field, with a narrow range of low 87Sr/86Sr ratios (0.70262–0.70327). The mantle-like C-O and Sr isotopes indicate that the coarse-grained dolomite rocks are magmatic in origin. Dolomite grains from the FD have experienced extensive hydrothermal alteration related to both REE mineralization and post-ore metamorphism of the Bayan Obo deposit. The domains of primary unaltered dolomite have high SrO and MnO contents that clearly distinguish them from sedimentary carbonates. The 87Sr/86Sr ratios of unaltered dolomite domains range from 0.70271 to 0.70473, with the majority lower than 0.7035, contrasting with higher 87Sr/86Sr ratios of Mesoproterozoic sedimentary carbonates globally. Thus, the primary unaltered fine-grained dolomite, the precursor to the FD, is also proposed to be a carbonatite. Compared with dolomite grains from the CD, most of the unaltered dolomite domains within the FD are more enriched in FeO and MnO and have higher δ13CV-PDB (-4.9 to 0.3 ‰) and δ18OV-SMOW (9.4 to 17.1 ‰) values. In addition, the FD contains abundant REE- and volatile-rich hydrothermal minerals and Fe-Mg carbonates, which are rare in the CD. The geochemical and mineralogical data in conjunction indicate that the melts forming the late-stage FD were much more evolved than those forming the early-stage CD. It is noteworthy that the unaltered dolomite domains within the FD have a wider range of 87Sr/86Sr ratios than those within the CD, which implies that the CD and FD, at least a proportion of them, are unlikely to have crystallized from the same progenitor magmas. Some FD was possibly the product of fractionation of less-evolved carbonatitic magma that generated the CD, whereas other FD crystallized from new pulses of magmas that were highly fractionated at depth. When compared with other carbonatite complexes, the Bayan Obo carbonatite suite is notable for having a large surface area (~48 km2 in outcrop) and containing an anomalously large proportion of highly evolved components. The voluminous evolved carbonatite clearly provided a basis for the accumulation of significant ore metals. Therefore, the giant-sized REE deposit is proposed to be associated with large-volume, highly evolved carbonatite at Bayan Obo.

Enrichment Factors and Metallogenic Models of Critical Metals in Late Permian Coal Measures from Yunnan, Guizhou, and Guangxi Provinces

The Late Permian coal measures in eastern Yunnan, western Guizhou, and central Guangxi are significantly enriched in critical metals that could serve as important supplements to conventional critical metal deposits in China. This study collected previous geochronological and geochemical data from the Late Permian coal measures to evaluate the distribution characteristics and enrichment factors of critical metals. Moreover, metallogenic models for critical metals were also developed. The results showed that Late Permian coal measures in Yunnan, Guizhou, and Guangxi provinces exhibited abnormal enrichment in Nb, Zr, and rare earth elements (REY, or REE if Y is excluded). The Emeishan mafic rocks and intermediate-felsic volcanic ash from the Truong Son orogenic belt underwent chemical weathering, with Nb and Zr selectively preserved in situ in the form of heavy minerals (e.g., rutile, zircon, and anatase), which subsequently led to the enrichment of Nb and Zr in bauxite and Al-claystone at the bottom of the Late Permian coal measures. Intermediate-felsic volcanic ash from the Emeishan large igneous province (ELIP) and the Truong Son orogenic belt supplied Nb, Zr, and REY for the middle and upper parts of the Late Permian coal measures. The intermediate-felsic mineral material of the coal measures in the intermediate zone, outer zone, and outside zone of ELIP are derived mainly from the ELIP, the mixture from ELIP and the Truong Son orogenic belt, and the Truong Son orogenic belts, respectively. Nb, Zr, and REY were leached by acidic aqueous solutions and from the parting and roof into underlying coal seams, where they deposited as authigenic minerals or adsorbed ions on organic matter during early coalification.

Genesis of Pb–Zn Mineralization in the Pulang Cu Polymetallic Deposit in Yunnan Province, China: Insights from Analyses of Geology, Fluid Inclusions and C–H–O–S Isotopes

The Pulang super-large porphyry Cu polymetallic deposit, located in the Sanjiang area of Yunnan Province, is one of the largest Cu deposits in China. This deposit hosts Cu resources of ~5 × 106 t and other ore-forming elements, such as Mo, Au, Ag, Pb, Zn, Pt and Pd. Recently, obvious hydrothermal vein-type Pb–Zn mineralization, with a Pb + Zn resource of ~0.4 × 106 t, has been detected in the North Ore Section of the deposit. However, the genesis of these Pb–Zn ore bodies, especially their relationship to the major Cu ore bodies in the South Ore Section, remains controversial. We conducted geologic description, fluid inclusion petrography and microthermometry, and C, H, O and S isotope studies to uncover the genesis of Pb–Zn vein-type mineralization in North Pulang. As a result, three types of Pb–Zn veins were identified: a quartz–pyrrhotite–chalcopyrite–sphalerite–galena vein, a quartz–pyrrhotite–sphalerite–galena vein, and a calcite–quartz–pyrrhotite–galena vein. All fluid inclusions in the quartz from different veins are liquid-rich inclusions, with homogenization temperatures in the range of 184 °C–235 °C and salinities between 10.4 wt.% and 17.8 wt.% NaCl eq., indicating that the Pb–Zn ore-forming fluid was a single-phase fluid with a low temperature and low-to-medium salinity. Hydrothermal quartz in different stages displays δDwater values ranging from −46.9‰ to −120.0‰ (V-SMOW), and the calculated δ18Owater values range from 2.4‰ to 4.3‰ (V-SMOW), implying that the mineralization fluids likely originated from magma, with a minor involvement of meteoric water. The δ13CCal values (−2.3‰ to −7.9‰ V-PDB) of calcite indicate that C likely originated from a deep-seated source. The δ34S values of chalcopyrite, pyrite, pyrrhotite and sphalerite reveal that S was possibly derived from magmatic rocks. Based on the above data, it is suggested that the Pb–Zn mineralization in North Pulang was the result of the northward migration of ore-forming fluids that originated from South Pulang along the NE-trending structural fractures. A strong water–rock interaction occurred during the migration process. However, the involvement of meteoric water and accompanied cooling of fluids were most likely responsible for the precipitation of galena and sphalerite.

The world-class carbonate-hosted Fankou Zn-Pb deposit in China. Part III. Critical metal Ga is enriched in late stage and low temperature sphalerite

Gallium (Ga), one of the critical metal elements, is commonly refined as a by-product of sphalerite. Previous studies recognized that Ga is extremely enriched in the Fankou Zn-Pb deposit that is a world-class, carbonate-hosted Zn-Pb deposit, but the tempo-spatial distribution of Ga remains unclear. Its stratiform, stratabound orebodies are strictly hosted in Devonian to Carboniferous carbonate sequences along a series of thrust faults, analogous to a Mississippi Valley-type (MVT) deposit. Herein, we carried out an integrated petrographic, Electron microprobe analyses (EPMA), and Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS) study on the sphalerite in the Fankou deposit, to clarify the concentration variations and occurrences of Ga and associated elements, as well as their substitution mechanism. Three types of sphalerites with different mineral associations and mineralogical characteristics were identified, that is, the earlier-crystalized, darker-colored Sp1a and Sp1b, and the later-crystalized, lighter-colored Sp2, respectively. Median values of Ga in the three sphalerite generations display an increasing trend, i.e., 12.76 ppm for Sp1a, 93.40 ppm for Sp1b, and 156.79 ppm for Sp2, respectively. Furthermore, trace elements mapping via LA-ICP-MS also shows that Sp1b in the grain rim is enriched in more Ga, Cu, and Ag contents. Further GGIMFis thermometers obtained a contrasting decreasing trend from early 203 °C to late 185 °C. Collectively, we conclude that Ga prefers to be enriched in the later-staged, light-colored, lower-temperatured sphalerite in the Fankou Zn-Pb deposit. This new study may shed light on the enrichment mechanism and exploration strategies of critical metal Ga in the global MVT Zn-Pb deposit.

Molecular transformations of heteroatomic organic compounds in crude oils caused by biodegradation and subsequent thermal maturation: Insights from ESI FT-ICR MS

The Tarim and Junggar basins are major petroliferous sedimentary deposits in China. Some oil reservoirs in these basins experienced superimposed secondary alterations including early biodegradation followed by thermal maturation/alteration (SSA-B&M). Heteroatomic polar organic compounds in crude oil are significantly influenced by SSA-B&M, which play a vital role in understanding the evolutionary history of oil reservoir. However, research on such alterations is limited. The present study employed negative and positive ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to investigate the molecular transformations of heteroatomic organic compounds in crude oils resulting from SSA-B&M. The findings indicate that biodegradation leads to an enrichment of naphthenic acids, while subsequent cyclization, aromatization and thermal cracking reactions enhances the aromaticity of the pyrolysis products of all the oil samples with varying degree of biodegradation. Notably, highest aromaticity was observed for the crude oil that has been most severely altered by biodegradation. During early and moderate stages of biodegradation, the abundances of O2 compounds (molecules contain two oxygen atoms) representing carboxylic acids were continuously increasing. However, at severe biodegradation levels, fatty acids with 1 double bond equivalents (DBE) underwent degradation, while the naphthenic acids were further enriched. Subsequently, during maturation, O2 compounds with 1 to 5 DBE experienced a steady decline in abundance. The naphthenic acids mainly experienced aromatization, while the fatty acids were partly decarboxylized and cracked thereby forming new n-alkanes. Biodegradation led to modification in neutral nitrogen compounds with 3 to 4 condensed rings (DBE = 9–12) and long alkyl side chains, while the impact on basic nitrogen compounds was relatively minimal. After subsequent thermal maturation, both neutral and basic nitrogen compounds with long alkyl side chains underwent cracking, while those with shorter alkyl side chains and higher degrees of condensation tended to remain relatively unchanged. Finally, two new indices were defined and tested to correctly evaluate the maturation and biodegradation level for crude oils that have experienced SSA-B&M.

In situ illite Rb-Sr dating indicates the coevality of Carlin-type gold deposits inside and around the isolated carbonate platform in western Guangxi, China

The western Guangxi is a crucial component of the Guizhou–Yunnan–Guangxi “Golden Triangle”(hereafter referred to as the Golden Triangle) of South China. The most discovered Carlin-type gold deposits in this region are primarily situated at the periphery of isolated carbonate platforms. The ore bodies are vein-like in form controlled by faults, and the wall rock are Triassic carbonate-bearing terrigenous clastic rocks. Recently, some gold deposits have been discovered in the interior of isolated carbonate platforms. The ore bodies are primarily stratiform hosted in sedimentary unconformities. The mineralized strata span from the Cambrian to the Permian, and the host rock include sandy and muddy dolostones, as well as a combination of sandstone, mudstone, tuff, and chert. The geological and geochemical characteristics suggest that these stratiform deposits in the interior of isolated carbonate platforms share common characteristic with Carlin-type gold deposits in China and USA. However, it remains uncertain whether these deposits are products of the one mineralization system and are coeval with those vein deposits at the periphery of the isolated platforms. To address this question, we conducted geological and isotopic dating studies on the Longhuo gold deposit and the De'e gold occurrence in the interior of isolated platforms. The Longhuo stratiform gold deposit occurs along a parallel unconformity in the Carboniferous/Devonian composed of sandstone, shale, tuff, and chert. Hydrothermal illite, quartz and auriferous pyrite fill along joints and fissures, implying that illite formed during the main ore-forming stage and its age could represent the age of gold mineralization. The stratiform orebodies of De'e gold occurrence are hosted in Cambrian sandy and muddy dolostones. Gold occurs as invisible Au in zoned pyrite and arsenopyrite, with a dominant alteration assemblage of silicification, carbonate alteration, and illitization. Hydrothermal quartz, illite and dolomite often aggregate with zoned auriferous pyrite and arsenopyrite in the most intensely altered zones, suggesting that illite formed during the main ore-forming stage and its age could also represent the age of gold mineralization. Illite LA-ICP-MS Rb-Sr dating was performed on both deposits, yielding ages of 184.16 ± 3.14 Ma for the Longhuo gold deposit and 191.21 ± 6.76 Ma for the De’e gold occurrence.Previous studies have indicated that Carlin-type gold deposits in the Golden Triangle exhibits two distinct age clusters, one ranging from 184 to 235 Ma and the other from 134 to 148.4 Ma. These dual age clusters suggest the potential occurrence of two mineralization events. The obtained ∼ 190 Ma mineralization ages for the Longhuo and De'e gold deposits in this study indicate that the Carlin-type gold mineralization within the isolated platform took place during the Early Jurassic. This aligns with the early mineralization event of gold deposits along the platform's edge, implying that gold deposits inside and around the isolated carbonate platform are products of the same mineralization system, influenced by post-Indosinian extensional events. The interior of the isolated carbonate platform holds substantial exploration potential, making it a novel direction for prospecting Carlin-type gold deposits in western Guangxi.

Iron isotope systematics of the Jiajika granite-pegmatite lithium deposit, Sichuan, China

The Jiajika deposit in western Sichuan is the largest pegmatite-type lithium deposit in China, but the mechanism of rare metal element enrichment in this giant deposit remains a topic of debate. This study presents a comprehensive Fe isotope study of granites, aplites, pegmatites, metamorphic rocks, and associated mineral separates from the 3211 m long deep Jiajika scientific drilling core (JSD-1) to constrain the magmatic-hydrothermal processes in the Jiajika deposit. Aplites and pegmatites have variable δ56Fe values that range from –0.12 ± 0.02 ‰ to 0.38 ± 0.02 ‰, by contrast, two-mica granite samples show limited variation in δ56Fe compositions (0.11 ± 0.04 ‰ to 0.21 ± 0.04 ‰). The Fe isotope data of the coexisting Fe-bearing minerals can impose critical constraints on crystal fractionation. Garnet shows the lightest δ56Fe compositions (–0.19 ± 0.06 ‰ to –0.06 ± 0.02 ‰) and tourmaline has the highest δ56Fe values (0.15 ± 0.01 ‰ to 0.22 ± 0.02 ‰) among all the investigated minerals, whereas the δ56Fe values of biotite range from 0.06 ± 0.02 ‰ to 0.18 ± 0.02 ‰. According to the compositional homogeneity of minerals and the relatively consistent offsets in δ56Fe between the three Fe-bearing mineral pairs, the co-existing Fe-bearing minerals in the Jiajika granitic pegmatites are interpreted to be in Fe isotope equilibrium. Additionally, based on the differences in mineral composition and geochemistry of bulk-rock samples at different observation depths, as well as the modeling results, the significant Fe isotope variation in Jiajika deposit reflect the combined results of biotite fractionation, hydrothermal alteration (tourmalinization), and garnet accumulation during multistage magmatic-hydrothermal processes. Spodumene-bearing pegmatites located in the upper portion of the drill core exhibit enrichment in heavy Fe isotopes (0.18 ± 0.04 ‰ and 0.30 ± 0.03 ‰) which can be attributed to their higher degree of magma evolution and the most abundant magmatic fluids related to enrichment and migration of rare metals. Furthermore, we conducted a comprehensive statistical analysis on the available Fe isotope data of granitic pegmatites, providing new insights into granite-pegmatite systems and related rare-metal mineralization processes from a Fe isotope perspective.

Architectural Characteristics and Distribution Patterns of Gravity Flow Channels in Faulted Lake Basins: A Case Study of the Shahejie Formation in the Banqiao Oilfield, China

Internal depositional architecture and sand body distribution are the main challenges faced in the development of gravity flow channel deposits in China. Despite significant progress in the exploration and development of gravity flow deposits in recent years, our understanding of the internal architecture of composite sand bodies within gravity flow channels is still limited. Gravity flow channels represent a widely developed sedimentary type in the Shahejie Formation of the Banqiao Oilfield, Huanghua Depression. The lack of understanding of the spatial stacking relationship of gravity flow channel sand bodies hinders further development and remaining oil recovery within the oilfield. Through this study, we aimed to dissect the composite channels (5th architectural units) and single channels (4th architectural units) at the study area, using a combination of well logs and seismic data. We explored the identification criteria and spatial distribution characteristics of internal architectural elements within gravity flow channel reservoirs, based on abundant drilling data, well density grids, and 3D seismic data. By identifying and delineating single channels, we were able to summarize six identification criteria for single channels, including relative elevation differences, curve shapes, and the number of interbeds. We obtained the sand body scale and aspect ratio of single channels and established three depositional architectural patterns, i.e., isolated, lateral migration, and vertical accretion, thus revealing the differences in the spatial stacking relationships of sand bodies in different structural locations (blocks). This work provides new insights into the depositional architectural patterns of gravity flow channel deposits in the Banqiao Oilfield, Huanghua Depression.

Mineralogy and element geochemistry of the Bayan Obo (China) carbonatite dykes: Implications for REE mineralization

The Bayan Obo deposit in China is the world's largest rare earth element (REE) deposit. However, its genesis remains highly debated. It is considered to have a close genetic association with carbonatites because of the presence of nearby carbonatite dykes and the geochemical similarities between these dykes and the orebody. However, the evolution of these dykes and associated REE mineralization remain poorly understood, hindering the origin interpretation of the deposit. This study provides new insights into the petrography, mineralogy, and major- and trace-element geochemistry of these carbonatite dykes and rock-forming minerals to reconstruct the magmatic evolution and REE enrichment of the deposit. The dykes evolved from dolomite- to calcite-dominated (i.e., calcite and fenitized calcite) carbonatites, and their REE content remarkably increased, with the latter developing strong REE mineralization. The dolomites and minor calcites within the dolomite carbonatites exhibit a steep negative slope with high light REE (LREE) enrichment and heavy REE (HREE) depletion, similar to the whole rock. In contrast, the calcites from the calcite-dominated carbonatites exhibit flat REE patterns with HREE enrichment. Combined with previous isotopic data and our petrology, mineralogy, and geochemistry study, we propose that these rocks are derived directly from the low-degree melting of the underlying mantle source. REE mineralization may be related to the progressive crystallization of rock-forming calcites of calcite-dominated carbonatites. Monazite, bastnäsite, parisite, and huanghoite are the dominant REE minerals and exhibit intimate associations with barite and alkaline silicate minerals such as aegirine, biotite, K-feldspar, and albite. This assemblage indicates that the REE were primarily transported via REE–sulfate and REE–alkali complexes, with the latter favoring HREE, and the precipitation of alkaline silicate minerals destabilized these REE complexes, facilitating REE mineralization.

Genesis of the Supergiant Shuangjianzishan Ag–Pb–Zn Deposit in the Southern Great Xing’an Range, NE China: Constraints from Geochronology, Isotope Geochemistry, and Fluid Inclusion

The supergiant Shuangjianzishan (SJS) Ag–Pb–Zn deposit, located in the southern Great Xing’an Range (SGXR), is the largest Ag deposit in China. The SJS deposit can be divided into two ore blocks: the Shuangjianzishan ore block and the Xinglongshan ore block. Given the importance of the Xinglongshan ore block in the SJS deposit, our work is focused on the Xinglongshan ore block. The vein orebodies in the Xionglongshan ore block mainly occur in the NW-, NNW-, and NNE-trending fault zones, and its mineralization is mainly related to a deep concealed syenogranite. Here, we present new geochronology, isotope geochemistry, and fluid inclusion data for the Xinglongshan ore block and provide additional insights into the metallogenic mechanism of the deposit. The dating results show that the syenogranite related to the mineralization formed at approximately 137 Ma, which is coherent with some previous age determinations in sulfides from the ore deposit. The mineralization of the Xinglongshan ore block can be divided into four stages: sphalerite–arsenopyrite–pyrite–chalcopyrite–quartz stage (stage I), sphalerite–galena–pyrite–silver-bearing mineral–quartz stage (stage II), sphalerite–galena–silver-bearing mineral–quartz–calcite stage (stage III), and weakly mineralized quartz–calcite stage (stage IV). Four types of fluid inclusions (FIs) have been identified within quartz and calcite veins: liquid-rich, gas-rich, pure-liquid, and pure-gas FIs. The homogenization temperatures in the four stages exhibit a gradual decrease, with stage I ranging from 253 to 302 °C, stage II from 203 to 268 °C, stage III from 184 to 222 °C, and stage IV from 153 to 198 °C, respectively. The salinity for stages I, II, III, and IV falls within the ranges of 3.4–6.6 wt% NaCl eqv., 2.6–7.2 wt% NaCl eqv., 2.9–7.0 wt% NaCl eqv., and 1.2–4.8 wt% NaCl eqv., respectively, indicative of a low-salinity ore-forming fluid. The δ18Owater and δD values of the ore-forming fluid span from −13.9‰ to 7.4‰ and −145‰ to −65‰, with δ13CV-PDB values between −11.0‰ and −7.9‰. These values suggest that the ore-forming fluid predominantly originated from a mixture of magmatic and meteoric water. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of sulfides range from 18.278 to 18.361, 15.530 to 15.634, and 38.107 to 38.448, respectively. These ratios imply that the ore-forming material was primarily derived from the Early Cretaceous granitic magma, which resulted from the mixing of depleted mantle- and crustal-derived magmas. The fluid mixing was the dominant mechanism for mineral precipitation. The Xinglongshan ore block belongs to a magmatic-hydrothermal vein-type deposit related to the Early Cretaceous syenogranite, and the Shuangjianzishan ore block belongs to an intermediate sulfidation epithermal deposit related to coeval subvolcanic rocks. The Ag–Pb–Zn mineralization at Shuangjianzishan is genetically related to the Early Cretaceous volcanic–intrusive complex.

Multiple mineralization events recorded in the Dahenglu Cu[sbnd]Co deposit, eastern North China Craton: Constraints from Re[sbnd]Os and U[sbnd]Pb geochronology

The formation of sediment-hosted CuCo deposits remains controversial, in part due to the lack of a precise age for CuCo mineralization. The Dahenglu deposit is located in the eastern part of the Jiao–Liao–Ji Belt (JLJB), one of the famous sedimentary–metamorphic-type CuCo deposits in China, that is mainly hosted within Palaeoproterozoic epimetamorphic rocks. The orebodies occur as stratoid, lenticular and veined forms in conformity with the carbonaceous sericite phyllite. In this study, we present new ReOs and monazite UPb geochronological data for carbonaceous sericite phyllite, and zircon UPb geochronological data for diorite porphyry associated with the deposit. The ReOs geochronology on carbonaceous rocks from the Dalizi Formation provides a direct and reliable depositional age of 1967 ± 23 Ma. The UPb analyses of metamorphic monazite intergrown with cobaltite yield an age of 1812 ± 8 Ma. Magmatic zircon UPb dating from ore-bearing diorite porphyry yields a weighted mean age of 121.8 ± 0.8 Ma. These results constrain three periods of mineralization in the Dahenglu deposit. Syngenetic sedimentary mineralization and metamorphic mineralization occurred during the Palaeoproterozoic, and magmatic–hydrothermal mineralization occurred during the Early Cretaceous. We suggest that ReOs and UPb geochronology on carbonaceous-bearing epimetamorphic rock and metamorphic monazite can serve as robust chronometers to establish the age and temporal evolution of sedimentary hosted CuCo mineralization.

In situ precise determination of stable Mo isotope ratios in molybdenite by femtosecond LA-MC-ICP-MS

We developed a new method for in situ measurement of Mo stable isotope ratios using femtosecond laser ablation coupled with MC-ICP-MS. Additionally, experiments were conducted on nine natural molybdenite samples from different ore deposits in China.

Granite-type lithium deposits in China: Important characteristics, metallogenic conditions, and genetic mechanism

Granite-type lithium deposits in China: Important characteristics, metallogenic conditions, and genetic mechanism