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The Tieshanlong ore field is an important part of the Nanling Range, which is famous worldwide for its W‐Sn mineralization. Notably, the mineralization age of the Tieshanlong ore field is not well constrained, and our field investigation reveals that granitic emplacement occurred at different stages. However, previous studies have not distinguished these multiple stages of magmatism. The Tieshanlong granite complex is closely related to the Huangsha quartz vein‐type W‐Sn deposit and Tongling skarn‐type Cu‐W‐Sn deposit in this field. Through field investigations and isotopic age analyses, this work studies the relationship between multistage magmatic activity and mineralization in the Tieshanlong ore field. LA‐ICP‐MS zircon U‐Pb isotope analyses revealed that the first‐ and second‐staged granites formed at 154.2 ± 0.6 Ma (MSDW = 1.4) and 151.2 ± 0.4 Ma (MSDW = 1.5), with zircon εHf(t) values ranging from ‐13.1 to ‐10.5 and from ‐14.7 to ‐11.1, respectively. These data suggest that the Tieshanlong granite complex was derived from the partial melting of ancient crustal material. LA‐ICP‐MS U‐Pb dating of wolframite and cassiterite reveals that W‐Sn mineralization occurred at 160–150 Ma, which agrees well with the U‐Pb dating results of the second‐staged granite within analytical errors. The magmatic activity in this ore field can be divided into three stages: 175–154 Ma, 154–150 Ma and 150–145 Ma. The quartz vein‐ and skarn‐type W‐Sn mineralization is closely related to second‐staged fine‐grained two‐mica granite, and formed earlier than skarn‐type Cu‐ mineralization. This study establishes a metallogenic model for the Tieshanlong ore field, and this model has important practical significance for identifying concealed W‐Sn(‐Cu) deposits around other granitic complexes in the Nanling Range. [ABSTRACT FROM AUTHOR]

The Yangchang phosphate deposit is a large-buried shallow marine carbonate stratified phosphorite deposit discovered in the Meishucun Formation (∈1 ms) of the Lower Cambrian recently. The understanding of its sedimentary environment and enrichment mechanism is still limited. Representative borehole cores were selected to carry out systematic sedimentary facies cataloguing. By means of sedimentary (microfacies) analysis, mineralogy acand mineral chemistry tracing, the characteristics of rock and mineral (assemblage), sedimentary (microfacies) types, sedimentary environment and spatial and temporal distribution of each lithologic section of the Meishucun Formation are analyzed. We also studied the sedimentary environment evolution, the source, migration and enrichment mechanism of phosphorus, and its metallogenic model. The comparative analysis shows that the ore-bearing strata exhibits the nearshore tidal flat facies sedimentary environment with transgression-regressive sequence vertically, 6 microfacies types in 3 subfacies namely supratidic flat, intertidal flat and subtidal flat are identified. Su-pratidic flat is divided into supratidic flat and supratidic carbonate flat. The intertidal flat is divided into intertidal carbonate flat, intertidal flat and storm current. The subtidal flat developed a low energy subtidal flat. The favorable phosphorus formation environment is the high energy intertidal flat in intertidal flat. Repeated action of tides and waves in the shallow water environment for a long time is conducive to the winnowing, enrichment and reconstruction of phosphorous rich particles, thus forming a phosphorous rock deposit with rich and thick beds in the northwest and poor and thin beds in the southeast of the mining area. To sum up, the ore forming process of the Yangchang phosphate deposit can be divided into three stages, namely: (1) initial accumulation and precipitation mineralization stage (phosphorus source carried by upwelling ocean current); (2) biochemical deposition and accretion mineralization stage (migration and enrichment driven by microbial decomposition, transformation and compound); (3) winnowing enrichment and re-enrichment mineralization stage (precipitation and enrichment driven by multi-stage wave and tidal action). This new points provides an important basis for prospecting and exploration in the mining area and peripheral areas. [ABSTRACT FROM AUTHOR]

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[Objective] Jiaojia-type gold deposit is a new type of gold mine discovered by Shandong geologists in northwestern Jiaodong in the 1960s, and its output is controlled by regional tectonic fracture zones. Pyrite sericitized alteration generally occurred during the ore-forming period, which is characterized by a large scale, distinct alteration zones, concentration of mineralization, simple morphology of the ore body, relatively uniform grade, and simple mineral combinations. The deposit has gone through 12 years of exploration and scientific research, from discovery to establishment. [Methods] This new type of gold deposit has been rapidly promoted since its establishment and has achieved fruitful prospecting results in China. Deep exploration achievements of the Jiaojia-type gold deposit have been coming up in the Jiaodong area since the 21st century. [Results] The accumulated gold resource reserves submitted have been 3617.12 tons by 2020, which has helped the Jiaodong area become the third largest gold cluster in the world, and gold reserves of China have risen to the second rink in the world. Research on the Jiaojia-style gold mine has also made considerable progress, with the age of mineralization accurately limited to 126~120 Ma and formation occurring under a strong regional extension background. The source of mineralization material has multiple origins, with the Archean tholeiite being the initial source rock of gold-bearing minerals. The ore-forming process is divided into four stages, and the “thermo-extension”metallogenic theory and the step metallogenic model are proposed. The metallogenic depth is about 5~10 km, and the post-metallogenic denudation thickness is 5.2±1.2 km, with the deposits well preserved. [Conclusion] The metallogenic prediction study concluded that the total gold resources in the three major metallogenic zones of Sanshandao, Jiaojia, and Zhaoping in the northwestern Jiaozhou area were 7258~10150 tons of metal at a depth of 5000 m, which demonstrates the immense potential of the deeper part of the Jiaojia-type gold deposits for exploration. A set of key exploration techniques was summarized for different exploration stages, from shallow to deep. [Significance] These studies enriched the metallogenic theory of the Jiaojia-type gold deposit, making the metallogenic prediction results highly accurate, reliable, and effective in guiding the gold exploration in the Jiaodong peninsula.

The eastern Liaoning-southern Jilin metallogenic belt is the leading site of hard rock-type boron deposit in China. Based on the previous research results of Precambrian geology, Jiao-Liao-Ji orogenic belt, as well as metallogenesis, the paper summarizes the coupling relationship between Paleoproterozoic orogeny and boron metallogenic events in eastern Liaoning region, and establishes the metallogenic model of boron deposits in eastern Liaoning-southern Jilin metallogenic belt. With the field survey on the typical boron deposits of Houxianyu, Wengquangou and Zhuanmiao-Yangmugan, the previous B and Mg isotopic data of the deposits are summarized and drawn for analysis. The results show that the boron deposits have experienced three main processes, i.e. early enrichment, mineralization during Paleoproterozoic orogeny and later reformation. Mg-rich marble and initially enriched B are the main ore-forming material sources. The basic and ultrabasic rocks play an important role in trapping B-rich fluids during orogenic metamorphism and contribute some ore-forming materials. The late metamorphism destroys orebody and partially improves the grade of ores. Finally, the paper also analyzes the main factors restricting boron prospecting in eastern Liaoning region, suggests that more attention be paid on the Paleoproterozoic formation and structure mapping, structural analysis and choice of suitable exploration means. The idea of further boron ore prospecting is also discussed. [ABSTRACT FROM AUTHOR]

This is an article in the field of earth sciences. Xidamingshan polymetallic ore concentration area is critical mineral prospecting district in Guangxi. With the promotion of the large-scale mineral breakthrough work, the Xidamingshan mineral exploration, the Nongtun large-scale Pb-Zn deposit has been newly discovered. However, the understanding of the metallogenic characteristics of the deposit, especially the genesis of the deposit, is still at the superficial stage. Based on detailed field geological investigations and previous work, this paper systematically summarizes the regional metallogenic geological background, mining area and geological characteristics, and analyzes the genesis of the Nongtun lead-zinc deposit to find out the metallogenic mechanism. The study shows the Nongtun Pb-Zn deposit is related-magmatic hydrothermal deposit, the ore-forming fluids originated from magmatic, and later mixed with meteoric water. The fluids extracted Pb and Zn ore-forming elements from the strata during long-distance transport, and combined with S of magmatic fluids to synthesize [HS]-ligand that converged in the fracture zone and transported to the shallow part, thus forming Pb-Zn ore vein. The above research results have established the metallogenic model of the Nongtun Pb-Zn deposit, which provides a good guidance for prospecting prediction and exploration.

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. [ABSTRACT FROM AUTHOR]

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Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective Copper is an important strategic metal resource for national economic and social development. Therefore, the exploration and resource assessment of copper mines are of great significance. Methods Based on collected geological profiles and drilling data, this study constructed a three-dimensional geological model for a copper ore deposit in western Yunnan, which was applied to estimate the resource reserve in the mining area. Results The ore resource is estimated to be 48.93 million tons, including 0.543 million tons of copper. Through comparative analysis, the model and resource estimation established by our newly proposed three-dimensional geological modelling system shows high credibility, in which multiple analysis modules and dynamic update function have a wide range of applications and it can be used for future drilling engineering and resources estimation. Conclusion This study provides the basis for further exploration work in this region, and it can also be applied to the exploration and mining of related polymetallic deposits.

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The Dahai Pb-Zn mining area is located in the northwestern Pb-Zn district in northeastern Yunnan Province in the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic triangle (SYGT), east of the Xiaojiang fault. Numerous Pb-Zn deposits (spots) occur in clastic rocks in this area. In this study, the Maliping, Laoyingqing, and Jinniuchang Pb-Zn deposits, representative clastic rocks in the Dahai mining area, were selected as research objects. The results of H-O-S-Sr-Pb isotope analyses show that the three deposits mainly formed through the mixing of a basinal brine with a hydrothermal fluid derived from deep within the underlying (deformed) basement, and brines leached organic matter from wall rocks. The δ34S values range from −2.62–30.30‰. The S isotope results show two different sources of reduced S: one in the Laoyingqing deposit derived from the S reduction generated by the pyrolysis of sulfur-bearing organic matter in the carbonaceous slate of the Kunyang Group, and the second in the Maliping and Jinniuchang deposits derived from the S reduction generated by the thermochemical sulfur reduction (TSR) of seawater sulfate in the Lower Cambrian Yuhucun Formation and Sinian Dengying Formation. The Pb isotope results show that the Pb sources of the three deposits are derived from basement rocks (Kunyang Group) with a small portion derived from Devonian–Permian carbonate rocks and Dengying Formation dolomite, both of which have undergone homogenization during mineralization. The Sr content varied from 0.09629 to 0.2523 × 10−6, and the study shows that the main source of Sr is a mixture of ore-forming fluid flowing through basement rocks (Kunyang Group) and through sedimentary cover. However, most of the Sr in the Maliping deposit is derived from marine carbonate, and in the Laoyingqing deposit, it is provided by basement rocks (Kunyang Group). Based on a comparative study of the deposits, the Pb-Zn deposits in the clastic rocks of the Dahai mining area and the SYGT belong to the same metallogenic system and were formed under the same metallogenic geological background. Finally, a unified metallogenic model of the two types of fluid migration and mixed mineralization of the Pb-Zn deposit in clastic rocks of the Dahai mining area is proposed. The metallogenic model provides a basis for the study of the Pb-Zn metallogenic system and guidance for deep and peripheral prospecting in this area. [ABSTRACT FROM AUTHOR]

The Qiandongshan–Dongtangzi large Pb-Zn deposit is located in the Fengxian–Taibai (abbr. Fengtai) polymetallic orefield. The ore bodies primarily occur within and around the contact surface between the limestone of the Gudaoling Formation and the phyllite of the Xinghongpu Formation, which are clearly controlled by anticline and specific lithohorizon. Magmatic rocks are well developed in the mining area, consisting mainly of granitoid plutons and mafic–felsic dikes. Previous metallogenic geochronology studies have yielded a narrow range of ages between 226 and 211 Ma, overlapped by the extensive magmatism during the Late Triassic period in this region. The ω(Co)/ω(Ni) ratio of pyrite in lead–zinc ore ranges from 4.44 to 15.57 (avg. 8.56), implying that its genesis is probably related to volcanic and magmatic-hydrothermal fluids. The δD and δ18O values (ranging from −94.2‰ to −82‰, and 18.89‰ to 20.72‰, respectively,) of the ore-bearing quartz indicate that the fluids were perhaps derived from a magmatic source. The δ34S values of ore-related sulfides display a relatively narrow range of 4.29‰ to 9.63‰ and less than 10‰, resembling those of magmatic-hydrothermal origin Pb-Zn deposits. The Pb isotopic composition of the sulfides from the Qiandongshan–Dongtangzi Pb-Zn deposit (with 206Pb/204Pb ratios of 18.06 to 18.14, the 207Pb/204Pb ratios of 15.61 to 15.71, and 208Pb/204Pb ratios of 38.15 to 38.50) is similar to that of the Late Triassic Xiba granite pluton, suggesting that they share the same Pb source. The contents of W, Mo, As, Sb, Hg, Bi, Cd, and other elements associated with magmatic-hydrothermal fluids are high in lead–zinc ores, and the contents of Sn, W, Co, and Ni are also enriched in sphalerite. The contents of trace elements and rare earth elements in the ore are similar to those in the Xiba granite pluton, and they maybe propose a magmatic-hydrothermal origin as well. As a result of this information, the Qiandongshan–Dongtangzi large Pb-Zn deposit may be classified as a magmatic hydrothermal stratabound type, with the Si/Ca contact area being the ore-forming structural plane. Thus, a mineralization model has been proposed based on a comparative analysis of the geological and geochemical properties of the lead–zinc deposit in the Fengtai orefield. It is considered that the secondary anticlines developed on both wings of the Qiandongshan–Dongtangzi composite anticline are the favorable sites for Pb-Zn deposition. Accordingly, the Si/Ca plane and secondary anticline are the major ore-controlling factors and prospecting targets. The verification project was first set up on the north wing of the composite anticline, and thick lead–zinc ore bodies were found in all verification boreholes, accumulating successful experience for deep exploration of lead–zinc deposits in this region. [ABSTRACT FROM AUTHOR]

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Since 2019, major breakthroughs have been made in the prospecting of the Lower Cretaceous sandstone-type uranium deposits in the northern Ordos Basin. The Lower Cretaceous sandstone layer is expected to become another important sandstone-type uranium prospecting target after the Middle Jurassic. Establishing the metallogenic model of the Lower Cretaceous provides a better guide for prospecting work. Based on previous regional geological, drilling cores, and analytical data, the authors systematically summarized the basic geological characteristics of uranium mineralization in the Lower Cretaceous in this area and preliminarily established the uranium metallogenic model of the Lower Cretaceous.The results suggest the six Lower Cretaceous rock types can be divided into three geochemical types. Uranium mineralization mainly occurs in the brown-gray sandstone, which is the transition zone from brown-red sandstone to green sandstone. The green sandstone is formed by oxidation first and then reduction.The metallogenic type is dominated by interlayer oxidation, supplemented by phreatic oxidation in the Late Cretaceous. The Lower Cretaceous "secondary oxidation" uranium metallogenic model can be divided into three stages: first oxidation mineralization stage, large-scale reduction mineralization stage, and second oxidation mineralization stage.These research results can provide a new idea for uranium exploration in new strata of Ordos Basin.

The Middle and Lower Reaches of the Yangtze River metallogenic belt (MLYMB) is one of the most important Fe‐Cu polymetallic belts in China. However, the mechanism and deep geodynamical process for the formation of this belt are still controversial. Here, we obtain the crustal and the uppermost mantle structures using ambient noise data from a dense seismic profile. A low velocity zone is revealed beneath the Moho of MLYMB, interpreted as the source of the deep mineralization materials. In addition, a low velocity layer (LVL) and a high velocity layer (HVL) are observed in the crust of the southern segment of the profile. The LVL is interpreted as a tectonic detachment layer between the upper and the lower crust, and the HVL is interpreted as the aggregation zone for mineralizing melts or crystallized magma chambers. Based on the observed velocity features, we propose a three‐stage model for the formation of ore deposits in MLYMB. Our model suggests that an upwelling of asthenosphere triggered by the delamination of a previously thickened lithosphere leads to the partial melting of upper mantle rocks, which eventually ponders under the Moho. The magma then infiltrates through the ductile lower crust and reaches a depth of ∼7–13 km, forming a minerals‐enriched magma chamber. Minerals‐rich hot fluids originating from the magma chamber continue to move upward along the pre‐existent faults and the minerals finally precipitate in dense veinlets when reaching shallow depths, forming the ore deposits in and around the MLYMB. Plain Language Summary: The formation of large‐scale mineral deposits is closely related to the lithosphere structure. The Middle and Lower Reaches of the Yangtze River metallogenic belt (MLYMB) is an ideal place to study the mineral system, as it is one of the most important Fe‐Cu polymetallic metallogenic belts in Eastern China and contains more than 200 ore deposits. Yet the mechanism and deep geodynamical process for the formation of this belt are still controversial. In this study, we construct a high‐resolution seismic model of the crust and the uppermost mantle using ambient noise data from a dense seismic profile. Our result reveals velocity features closely related to the metallogenic process in this region. Based on the observed velocity features, we propose a three‐stage model for the formation of the ore deposits in MLYMB, which is of great importance for the development of "mineral system" approaches to the exploration of minerals worldwide. Key Points: We obtain a fine Vs structure of the crust and uppermost mantle beneath the MLYMBWe observe velocity features closely related to the metallogenic process of MLYMBWe propose a three‐stage metallogenic process for the origin of the MLYMB [ABSTRACT FROM AUTHOR]

The lower Cambrian Maidiping formation in the Mabian area of southern Sichuan is a crucial ore-bearing horizon for Kunyang-style phosphate ores. The sedimentary paleoenvironment controls the distribution of phosphate ore. Based on the field section measurements and borehole core observations of the phosphorus-bearing strata of the Maidiping formation in the Huangjiaping area of Mabian, the characteristics of the sedimentary phases, phosphate massifs, and the mode of phosphate ore genesis of the Maidiping formation were studied in detail. The study shows that the Maidiping formation has developed carbonate tidal flat sedimentary facies, and six micro-phases can be identified in three subphases: supratidal flat, strand flat, and subtidal flat. The supratidal flat includes supratidal beach and supratidal dolomite flat; the strand flat includes tidal channel, intertidal beach, and intertidal limestone flat; the subtidal flat is only developed with the low-energy subtidal flat, showing a sedimentary evolution sequence of sea recession and sea erosion in the vertical direction. Based on the finding, we established the bay–tidal flat depositional model in the Maidiping formation. The sedimentary facies strictly controls the enrichment of phosphorite, and the intertidal beach and tidal channel with high energy hydrodynamics in the strand flat is the most favorable environment for phosphorite formation. The sand–gravel phosphorite is the most widely developed phosphorite type in the Mabian area. The mineralization mode of phosphate deposits is that the rising ocean current brings phosphorus-rich seawater into the tidal flat environment of the bay, and the phosphorus condenses and accumulates in the form of colloid-chemical, by biological and chemical interactions, forming semi-solidified and weakly-solidified phosphate sediments, which are then subjected to water scouring, crushing, transporting, and precipitation again, and then formed into high-grade phosphate masses after compaction and consolidation.

Xianglushan Ore Field is a component of the Jiuling W-Mo-Sn-Cu-Au polymetallic fluorite and kaolin metallogenic sub-belt in the eastern part of the Jiangnan Metallogenic Belt, and is also one of the important tungsten polymetallic ore fields in northern Jiangxi.In recent years, the ore field has successively discovered tungsten deposits such as Xingping, Zhangtianluo, and Dayanxia.Based on the latest exploration and research results, this paper has studied the metallogenic factors and laws of tungsten in Xianglushan Ore Field.It is believed that the Upper Sinian-Cambrian strata contain carbon, silicon, and argillaceous rocks that are closely related to metallogenesis, and the superposition and intersection of NEE-trending anticline with the NE-trending secondary structure obviously restrict the ore-forming location of the deposit; the ore body location is controlled by the interlayer fracture zone of the lithologically variant difference surfaces of the ore-bearing strata and the contact position between the fine-grained biotite granite and the charcoal, siliceous and argillaceous rock types, and the superposition and intersection are favorable to the formation of rich and thick ore bodies; the main ore bodies occur in the diopside-biotite metamorphic zone, and are related to the alteration such as greisenization; the Rb-Sr isochron age of the late Yanshannian S type fine-grained biotite granite is 126.2 Ma±2.6 Ma, indicating that the Sm-Nd isochron age of the scheelite（121 Ma±11 Ma）of Xianglushan Tungsten Deposit is in an obvious coupling relationship with the time when the fine-grained biotite granite magma emplacement occurred in the area, indicating that the metallogenesis is related to the granite magmatism in the late Yanshannian, and the fine-grained biotite granite body is more closely related to the tungsten metallogenesis.On this basis, the metallogenic model and integrated prospecting model of tungsten metallogenesis in Xianglushan Ore Field are established. [ABSTRACT FROM AUTHOR]

A succession of Permian bauxite deposits are concentrated in Wuchuan, Zheng'an and Daozhen counties of northern Guizhou, South China. These deposits overlie contrast bedrocks, which are discriminated from the other bauxites of karst type in South China. Horizons of these bauxites are typified by sandwiched constructure, the upper and the lower layers of bauxitic claystone interbedded by the ore layer, and by abundant pyrite occurring in the ore and the lower layers. A geochemical study was carried out on samples from two boreholes of bauxitic profiles with claystone and carbonate bedrocks, respectively. It shows that the diverse profiles illustrate contrast mobility of elements. The profile overlying clayey bedrock is depleted in most elements including REE but variously enriched in HFSE, Pb, Mo, and half mass of Al2O3 was leached out; the profile overlying carbonatic bedrock is highly enriched in REE and moderately in HFSE and Pb, its Al2O3 mass was basically preserved. Both horizons are extremely enriched in alkali of Li and variously in Ce. A new genetic model is suggested accordingly. Tropic climate, coastal plain and frequent transgression and regression during the Permian caused a transition of weathering profiles from laterization to bauxitization in northern Guizhou. Massive pyrite in the horizons formed under reducing environment during the transgression through combining of iron enriched in the laterite profile and sulfur from the soaking and penetrating seawater; during the regression, oxidation of pyrite caused strong acid medium and induced the bauxitization. [ABSTRACT FROM AUTHOR]

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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.

Southwestern Guizhou province is one of China's most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit, based on which we proposed the metallogenic model. Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline (Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT (the product of tectonic slippage and hydrothermal alteration) between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline (Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline, Erlongqiangbao anticline, and their transition areas all show good metallogenic elements (Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit: (1) related to the Emeishan mantle plume activity; (2) source from the Emeishan basalt; (3) metamorphic fluid mineralization; (4) basin fluid mineralization; (5) related to deep concealed magmatic rocks; of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO2 and CH4. The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined; this is of great significance for regional mineral exploration and studying the genesis of gold deposits. [ABSTRACT FROM AUTHOR]

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The Dahai Pb-Zn mining area is located in the northwestern Pb-Zn district in northeastern Yunnan Province in the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic triangle (SYGT), east of the Xiaojiang fault. Numerous Pb-Zn deposits (spots) occur in clastic rocks in this area. In this study, the Maliping, Laoyingqing, and Jinniuchang Pb-Zn deposits, representative clastic rocks in the Dahai mining area, were selected as research objects. The results of H-O-S-Sr-Pb isotope analyses show that the three deposits mainly formed through the mixing of a basinal brine with a hydrothermal fluid derived from deep within the underlying (deformed) basement, and brines leached organic matter from wall rocks. The δ34S values range from −2.62–30.30‰. The S isotope results show two different sources of reduced S: one in the Laoyingqing deposit derived from the S reduction generated by the pyrolysis of sulfur-bearing organic matter in the carbonaceous slate of the Kunyang Group, and the second in the Maliping and Jinniuchang deposits derived from the S reduction generated by the thermochemical sulfur reduction (TSR) of seawater sulfate in the Lower Cambrian Yuhucun Formation and Sinian Dengying Formation. The Pb isotope results show that the Pb sources of the three deposits are derived from basement rocks (Kunyang Group) with a small portion derived from Devonian–Permian carbonate rocks and Dengying Formation dolomite, both of which have undergone homogenization during mineralization. The Sr content varied from 0.09629 to 0.2523 × 10−6, and the study shows that the main source of Sr is a mixture of ore-forming fluid flowing through basement rocks (Kunyang Group) and through sedimentary cover. However, most of the Sr in the Maliping deposit is derived from marine carbonate, and in the Laoyingqing deposit, it is provided by basement rocks (Kunyang Group). Based on a comparative study of the deposits, the Pb-Zn deposits in the clastic rocks of the Dahai mining area and the SYGT belong to the same metallogenic system and were formed under the same metallogenic geological background. Finally, a unified metallogenic model of the two types of fluid migration and mixed mineralization of the Pb-Zn deposit in clastic rocks of the Dahai mining area is proposed. The metallogenic model provides a basis for the study of the Pb-Zn metallogenic system and guidance for deep and peripheral prospecting in this area.

A series of sandstone-type copper deposits and occurrence distribute in the Kuqa basin, Xinjiang. We carried out a research into the sedimentary environment and metallogenic model of the copper deposits in the Kangcun area based on field surveys. The relationship between the sedimentary environment/facies in the area and the copper mineralization were summarized so as to explore the genesis of mineralization and the metallogenic model. We identified main sedimentary facies types of alluvial fans, fan deltas, and lakes in the Neogene strata, and further identification of five subfacies and seven microfacies were made. Our research results reveal that the genesis of sandstone-type copper mineralization is related to the sedimentary environment, and the mineralized bodies are mainly distributed in fan delta plain facies and fan delta front facies. Detrital zircon dating results of two samples are 427.4±6.6 Ma, 387.3±3.3 Ma and 424.6±2.3 Ma, 279.9±6.8 Ma respectively. It indicates that the source of the copper-bearing sandy conglomerate in the Miocene Jidike Formation (N1j) is mainly from the strata and magmatic rock products formed by the geological evolution during the Late Silurian to Early Permian. The mineralization in the Kangcun area belongs to the sandstone-type copper mineralization. The deep copper enrichment is TSR-type mineralization, and the surface mineralization is caused by the surficial and underground brine. The copper mineralization in the Kangcun area was formed after the diagenesis of Neogene sandstone. It is epigenetic enrichment, and is mainly controlled by fault structure and epigenetic brine in the Late Neogene.

The Hongqiling magmatic Cu–Ni sulfide deposit is one of the most important deposits in the easternmost segment of the Central Asian Metallogenic Belt, northeast China. However, the existence or non-existence of magmatic chambers is still not been determined, which is the key to decipher the formation of Hongqiling Cu–Ni deposit. Therefore, this study proposes to adopt long-period magnetotellurics method to image the deep-seated metallogenic system in Hongqiling Cu–Ni deposit. Two-dimensional (2D) nonlinear conjugate gradient inversion technology allows us to describe entire magma plumbing system, including the mantle-derived magma channels (banded low-resistivity anomalies), deep separated chamber (low-resistivity anomaly C2), and shallow magma conduits (low-resistivity anomaly C1). These results indicated that the mantle-derived primitive magma gave rise to the parental magma for the mafic–ultramafic intrusions in Hongqiling Cu–Ni deposit and triggered the segregation of Cu–Ni sulfides in the shallow chamber. By combining the experimental simulation, geochemistry, geochronology, and geotectonics data in the study area, we suggest that the partial melting processes which produced the large magma plumbing system probably have been triggered by lithospheric delamination.

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Hydrothermal vein-type fluorite deposits are the most important metallogenic type of fluorite deposits in South China, most of which are closely related to granitoid in space; however, the genetic relationship between granitoid and fluorite mineralization remains controversial. The Shuanghuajiang fluorite deposit in northern Guangxi of South China is a typical vein-type fluorite deposit hosted in a granite pluton, with the orebodies occurring within brittle faults. Zircon U-Pb dating of the hosting Xiangcaoping granite yields an emplacement age of 228.04 ± 0.76 Ma (MSWD = 0.072). Fluorite Sm-Nd dating yields an isochron age of 185 ± 18 Ma. The new age data indicate that the fluorite deposit was precipitated significantly later than the emplacement of the hosting Xiangcaoping granite pluton. The fluorite and granite exhibit similar rare earth element (REE) patterns with negative Eu anomalies, suggesting that fluorine (F) was derived from the granite. The fluorite fluid inclusions show a homogeneous temperature mainly ranging between 165 °C and 180 °C. Salinity is typically less than 1% NaCl eqv, while the δ18OV-SMOW and δDV-SMOW values are between −5.2‰–−6.1‰ and −17.35‰–−23.9‰, respectively. These indicate that the ore-forming fluids were a NaCl-H2O system with medium-low temperature and low salinity, which is typical for meteoric water. Given the combined evidence of geochronology, REE, and fluid geochemistry, the mineralization of the Shuanghuajiang fluorite deposit is unrelated to magmatic-hydrothermal activity but achieved via hydrothermal circulation and leaching mechanisms. Our study presents a genetic relationship between the fluorite deposit and granitoids based on an example of northern Guangxi, providing a better understanding of the genesis of hydrothermal vein-type fluorite deposits in granitoids outcropping areas. [ABSTRACT FROM AUTHOR]

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The Qiandongshan–Dongtangzi large Pb-Zn deposit is located in the Fengxian–Taibai (abbr. Fengtai) polymetallic orefield. The ore bodies primarily occur within and around the contact surface between the limestone of the Gudaoling Formation and the phyllite of the Xinghongpu Formation, which are clearly controlled by anticline and specific lithohorizon. Magmatic rocks are well developed in the mining area, consisting mainly of granitoid plutons and mafic–felsic dikes. Previous metallogenic geochronology studies have yielded a narrow range of ages between 226 and 211 Ma, overlapped by the extensive magmatism during the Late Triassic period in this region. The ω(Co)/ω(Ni) ratio of pyrite in lead–zinc ore ranges from 4.44 to 15.57 (avg. 8.56), implying that its genesis is probably related to volcanic and magmatic-hydrothermal fluids. The δD and δ18O values (ranging from −94.2‰ to −82‰, and 18.89‰ to 20.72‰, respectively,) of the ore-bearing quartz indicate that the fluids were perhaps derived from a magmatic source. The δ34S values of ore-related sulfides display a relatively narrow range of 4.29‰ to 9.63‰ and less than 10‰, resembling those of magmatic-hydrothermal origin Pb-Zn deposits. The Pb isotopic composition of the sulfides from the Qiandongshan–Dongtangzi Pb-Zn deposit (with 206Pb/204Pb ratios of 18.06 to 18.14, the 207Pb/204Pb ratios of 15.61 to 15.71, and 208Pb/204Pb ratios of 38.15 to 38.50) is similar to that of the Late Triassic Xiba granite pluton, suggesting that they share the same Pb source. The contents of W, Mo, As, Sb, Hg, Bi, Cd, and other elements associated with magmatic-hydrothermal fluids are high in lead–zinc ores, and the contents of Sn, W, Co, and Ni are also enriched in sphalerite. The contents of trace elements and rare earth elements in the ore are similar to those in the Xiba granite pluton, and they maybe propose a magmatic-hydrothermal origin as well. As a result of this information, the Qiandongshan–Dongtangzi large Pb-Zn deposit may be classified as a magmatic hydrothermal stratabound type, with the Si/Ca contact area being the ore-forming structural plane. Thus, a mineralization model has been proposed based on a comparative analysis of the geological and geochemical properties of the lead–zinc deposit in the Fengtai orefield. It is considered that the secondary anticlines developed on both wings of the Qiandongshan–Dongtangzi composite anticline are the favorable sites for Pb-Zn deposition. Accordingly, the Si/Ca plane and secondary anticline are the major ore-controlling factors and prospecting targets. The verification project was first set up on the north wing of the composite anticline, and thick lead–zinc ore bodies were found in all verification boreholes, accumulating successful experience for deep exploration of lead–zinc deposits in this region.

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The cross-gradient joint inversion of gravity and magnetic data is a commonly used way, which requires dividing the subsurface into closely arranged cells with structured or unstructured grids to solve the physical properties of the discrete subsurface. Unstructured grids can more effectively fit undulating terrain and irregular geological bodies than structured grids. However, the existing cross-gradient joint inversion method with structured grids cannot be used to complete the inversion with unstructured grids. We proved that the second-order Taylor formula is more suitable for calculating the cross-gradients of unstructured grids; therefore, we first proposed and implemented the second-order Taylor formula cross-gradient (2-TCG) method for the cross-gradient joint inversion of gravity and magnetic data with unstructured grids, which can calculate the cross-gradient item more easily than other ways because the first few coefficients of Taylor formula are gradient items. The model tests showed that the 2-TCG joint inversion method can accurately achieve the 3-D joint inversion of gravity and magnetic data with unstructured grids, and this method can better describe the detailed information of irregular geological bodies in complex terrain. To explore the minerals and analyze the metallogenic model in the Huanggang–Ganzhuermiao metallogenic belt of the southern Greater Khingan Range, Inner Mongolia, we measured gravity and magnetic data on a scale of 1:10000. We estimated the mineral distributions with 150–280 m depth by 2-TCG joint inversion. We analyzed the relationship between ore bodies and faults, and we established a mixed metallogenic model of the skarns and hydrothermal veins in the survey area. [ABSTRACT FROM AUTHOR]

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Many theoretical results on sandstone-type uranium mineralization in northern China obtained by the uranium research team of the Tianjin Center of Geological Survey in recent years are presented. From the source sink system of uranium-producing basins, sedimentary environment of uranium-bearing rock series, ore-forming fluid information, evolution of tectonic events, basin formation and development, we redefine and classify uranium orebodies, redox zoning, and ore-controlling structural styles. We then systematically propose a theoretical system of sandstone-type uranium deposits in northern China. We conclude that sandstone-type uranium deposits in northern China are mainly found in sedimentary environments such as rivers, deltas, and alluvial fans in the Mesozoic and Cenozoic lowstand systems tract and in gray sandstone layers in the vertical redox zoning. The orebodies are controlled by the tectonic slope belt, which is in the shape of a strip on the plane, and spreads in a layer or plate on the section. Vertical (ups and downs) tectonic movement triggers large-scale phreatic flow in the basin, which is the real driving force for controlling the ore-forming fluid. The theoretical system of sandstone-type uranium deposits in northern China should be based on global tectonic movement and environmental changes and take into account factors such as basins as a unit to study mineralization background, ore concentration areas as objects to study mineralization, and the correlation between regional tectonic movement and metallogenic process as a breakthrough point to study tectonic events and metallogenic events. It should also be based on different basin types to establish metallogenic models. The innovative research results and ideas are summarized with the aim of promoting the continuous improvement of sandstone-type uranium mineralization theory in northern China. [ABSTRACT FROM AUTHOR]

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The Qianjiadian uranium deposit is located in the Kailu Depression of Songliao Basin. It is a large-scale in-situ leachable uranium deposit of sandstone type and provides a typical case of the uranium deposits in the Songliao Basin. Here we analyze the impact of oil and gas on reduction alteration, and factors including low grade mineralization. The Qianjiadian uranium deposit is characterized as a typical roll-type deposit with interlayers in oxidized zone. The occurrence of reductive low-permeability sandstone in uranium reservoirs controls the morphology of the uranium-rich orebody. We propose a metallogenic model involving multi-stage superposition characterized by “primary sediment enrichment - interlayer oxidation - superimposed transformation”. Our model would be helpful for formulating guidelines in the exploration for sandstone-type uranium deposits in the Songliao Basin.

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The Xucun uranium deposit is located in the Luzong ore concentration area of the Middle and lower reaches of the Yangtze River metallogenic belt. It belongs to a middle-low temperature hydrothermal type uranium deposit which is related to Huangmeijian A-type granite in late Yanshanian period. The main ore types are feldspathic sandstone-type uranium ores and a few are quartz syenite type uranium ores. Based on the detailed field exploration and research work in recent years, this paper summarizes the metallogenic geological background and geological characteristics of the uranium deposits, discusses the mechanism of uranium mineralization. It is considered that the morphology and structural development of the rock-stratum contact interface are the decisive factors to control the spatial distribution of uranium ore body. The inner and outer contact zones of rock mass are the most favorable ore-bearing sites. Uranium mineralization is closely related to the intrusion of magmatic rocks in the late Early Cretaceous. In addition, the metallogenic mechanism of the deposit is further discussed and the metallogenic model of Xucun uranium deposit is established. That has important reference for enriching the theory of hydrothermal uranium mineralization related to A-type granite. At the same time, it also provides the basis for further exploring the uranium mineralization, metallogenic types and ore-prospecting potential of the NE-trending A-type granite belt in Huangmeijian area and even in Luzhou Basin. [ABSTRACT FROM AUTHOR]

The genetic relationship of massive and disseminated ores of Cu-Ni sulfide deposits in Baotan area of the northern Guangxi is highly debated, which is of great significance for acknowledgement of the genesis of Cu-Ni sulfide deposits and mineral exploration in the future. The characteristics of platinum group elements ( PGE) of ores and barren rocks from Cu-Ni sulfide deposits were analyzed to constrain the genesis of Mandong Cu-Ni sulfide deposit in Baotan area. The results show that total contents of PGE of the disseminated and massive ores as well as barren rocks are quite low and well positively correlated with the content of sulfide, the PGE are significantly depleted relative to Cu and Ni; the primitive mantle-normalized PGE spider diagram of ores and barren rocks is weakly differentiated with variable Pt contents, and the ratios of Pd/Ir are 0. 93-15. 41; the massive ore shows a negative Pt pattern, while the disseminated ore has a bit positive Pt anomaly, and the barren rocks have no anomaly; the ratios of Cu/Pd of ores and barren rocks range from 10. 38 X 10³ to 1 830. 00 X 10³, much higher than that of primitive mantle (6 500), implying the occurrence of sulfide segregation in the deep of Mandong Cu-Ni sulfide deposit, which results in PGE depletion of the newly formed ores and barren rocks in the shallow intrusions; minerals rich in Pt directly crystallize from the sulfide melt prior to monosulfide solid solution (MSS) crystallization, and then the sulfide melts migrate away from the minerals rich in Pt along structural fractures and form the massive ores, which result in Pt depletion of the massive ores. [ABSTRACT FROM AUTHOR]

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[Display omitted] • The magmatic-hydrothermal system of Yangla skarn Cu deposit is relatively reduced. • The barren quartz porphyry was also originated from reduced magmas and thus less fertile for porphyry Cu formation. • Intense fluid-carbonate rocks interaction and fluid focusing could be the key to formation of the reduced Yangla Cu deposit. In the Paleo-Tethyan orogenic belt, reduced mineralization systems result in extensive saturation and segregation of magmatic sulfide phases, which in turn leads to the loss of chalcophile elements and hinders the precipitation of large amounts of copper. As a result, porphyry Cu deposits are rare within the belt. In this contribution, we investigate the composition of zircons from the granodiorite, fluid inclusions and hydrothermal scheelite from orebodies of the Yangla Skarn Cu deposit, and assess the magmatic-hydrothermal redox state of the system. The igneous zircons from ore-causative granodiorite have negative Eu anomalies (Eu N /Eu N * = 0.27 ± 0.03, n = 11) and the calculated ΔFMQ values are -0.23 ± 0.31 (n = 11). The ore-forming fluids in the pre-ore stage was rich in CH 4 , and precipitating hydrothermal scheelite in the syn -ore stage with low Mo contents (Mo = 17.4 to 149 ppm, mean 57.7 ppm) and positive Ce anomalies (Ce N /Ce N * = 1.14 ± 0.06, n = 29). The geochemistry suggests that the magmatic-hydrothermal system at Yangla is relatively reduced, consistent with the abundant development of pyrrhotite in the ore body. In addition, we have carried out zircon SIMS U-Pb dating and trace analysis of the barren quartz porphyry in the Yangla ore field, which gives an emplacement age of 227 Ma and is also derived from reduced magmas (ΔFMQ = -1.27 ± 0.55; Eu N /Eu N * = 0.32 ± 0.10, n = 7) that were less fertile for porphyry Cu formation. By comparing with the barren quartz porphyry, we suggest that the key control of the skarn ore body may have been that the low-permeability of carbonate units seal the mineralizing fluids, enhancing fluid-carbonate reactions and concentrating the sulfides in a relatively small area. Without these processes, it can only form barren porphyry system. We highlight that, unlike typical porphyry Cu deposits, intense fluid-carbonate rocks interaction and fluid focusing could result in skarn Cu formation, even though in relatively reduced magmatic-hydrothermal conditions. [ABSTRACT FROM AUTHOR]

Hydrothermal vein-type fluorite deposits are the most important metallogenic type of fluorite deposits in South China, most of which are closely related to granitoid in space; however, the genetic relationship between granitoid and fluorite mineralization remains controversial. The Shuanghuajiang fluorite deposit in northern Guangxi of South China is a typical vein-type fluorite deposit hosted in a granite pluton, with the orebodies occurring within brittle faults. Zircon U-Pb dating of the hosting Xiangcaoping granite yields an emplacement age of 228.04 ± 0.76 Ma (MSWD = 0.072). Fluorite Sm-Nd dating yields an isochron age of 185 ± 18 Ma. The new age data indicate that the fluorite deposit was precipitated significantly later than the emplacement of the hosting Xiangcaoping granite pluton. The fluorite and granite exhibit similar rare earth element (REE) patterns with negative Eu anomalies, suggesting that fluorine (F) was derived from the granite. The fluorite fluid inclusions show a homogeneous temperature mainly ranging between 165 °C and 180 °C. Salinity is typically less than 1% NaCl eqv, while the δ18OV-SMOW and δDV-SMOW values are between −5.2‰–−6.1‰ and −17.35‰–−23.9‰, respectively. These indicate that the ore-forming fluids were a NaCl-H2O system with medium-low temperature and low salinity, which is typical for meteoric water. Given the combined evidence of geochronology, REE, and fluid geochemistry, the mineralization of the Shuanghuajiang fluorite deposit is unrelated to magmatic-hydrothermal activity but achieved via hydrothermal circulation and leaching mechanisms. Our study presents a genetic relationship between the fluorite deposit and granitoids based on an example of northern Guangxi, providing a better understanding of the genesis of hydrothermal vein-type fluorite deposits in granitoids outcropping areas.

Based on the geological conditions and characteristics of mineralization present, three‐dimensional geological modelling is used in conjunction with previous deep research results, in order to discuss the process of deep mineralization in the Tongling ore district. The structural analysis shows that surface deformation is strong, deep deformation is weak, the surface has mainly experienced brittle deformation, with the possibility of a large number of deep ductile deformations. There is a thrust nappe between the Tongling uplift and the Nanling basin, that is the boundary of the Tongling block, which has resulted in the southwest uplift of the Tongling block. Combined with the deep exploration data, the three‐dimensional shape of the main rock masses is interpreted, with three‐layer structures in the deep magma chamber. The spatial distribution of magmatic rocks is mainly controlled by the structure. The movement of magmatic hydrothermal fluid is dominated by mesoscale seepage in the deep part and 'dike' type upwelling in the shallow part. There is a certain coupling relationship between the ore‐forming rock mass and the surrounding rock. The ore‐forming age is dominated by the Yanshanian period. Based on the distribution, types and metallogenic characteristics of the deposits, the metallogenic model of 'layer coupling' in the Tongling ore district is summarized, with the 'one body, two belts and a multilayer metallogenic system' is established, which is significant for the future direction of deep prospecting in the Tongling area. [ABSTRACT FROM AUTHOR]

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The metallogenic environment of the Irtysh gold belt in Xinjiang is studied in detail. The metallogenic geological background, metallogenic conditions and ore-controlling factors of the gold deposits in eastern, central and western regions of the metallogenic belt are compared. The metallogenic structure of the Irtysh tectonic belt has the characteristics of diverging to the west and converging to the east. Composite ore controlling by ductile shearing and magmatic activity in Irtysh gold belt result in zoned and segmented distribution of gold mineralization. Through the fluid inclusion research and H-O-S isotope analysis, the evolution regularity of gold ore-forming fluids in the region was analyzed. Synchrotron radiation X-ray fluorescence was used to analysis the concentration of metal elements in a single fluid inclusion, explaining the occurrence and migration process of Au in hydrothermal fluid. The source of ore forming minerals in western gold deposit is more closely related to magmatic activity, and the structural metamorphism of eastern gold deposit has greater influence on mineralization. Metallogenic fluids of gold deposits are characterized by metamorphic water (and magmatic water) in the early stage and mixed with meteoric water in the late stage. And the metallogenic elements are enriched in CO2 rich fluid. The Au is mainly activated, migrated and enriched with the mixed fluid of magmatic hydrothermal, metamorphic hydrothermal and atmospheric precipitation in the medium-low temperature, shallow to medium-deep environment. [ABSTRACT FROM AUTHOR]

In order to investigate the metallogenic genesis and potential of sandstone-type uranium deposit of the lower member of Yimin Formation in Kelulun sag of Inner Mongolia, the key ore-controlling conditions, such as inner and external uranium sources, tectonic setting, characteristics of lithology-lithofacies, epigenetic oxidation, and characteristics of uranium mineralization, were summarized. Moreover, the ages of uranium mineralization and target strata were determined, which can be used to build a reasonable sandstone-type uranium metallogenic model. The results show that the main exploration target in Kelulun sag is the lower member of Yimin Formation; meanwhile, the uranium contents of Jurassic intermediate-acid volcanic rocks, Hercynian granitoids, Lower Cretaceous Yimin Formation and groundwater are relatively high, indicating that inner and external uranium sources are abundant in the area; the target strata mainly develop fan delta-shore shallow lake sedimentary system during the fault-depression transition period, and are characterized by(underwater)distributary channel grey sand bodies; the lithology is mainly composed of gravel-bearing coarse sandstone and glutenite with loose structure and well permeability; the primary sandstone has a high reduction capacity owing to abundant charcoal and plant stems, which is a good ore-bearing construction; the sand bodies generally develop strong brownish yellow planar paleophreatic epigenetic oxidation with paleophreatic-interlayer oxidation locally, which significantly control the formation and shape of the orebodies; correspondingly, the discovered orebodies with a burial depth of less than 150 m and a uranium content of 0.46-1.00 kg·m-2, mainly have lenticular and stratoid shapes; furthermore, the isochron metallogenic ages of(67.1+5.9)Ma and(63.7+5.2)Ma are obtained by whole-rock U-Pb isotope dating with different grades of uranium-mineralized sandstones; finally, a four-stage paleophreatic-interlayer oxidation uranium metallogenic model is established based on tectonic evolution history, including preparatory stage of uranium-rich formation in early Early Cretaceous, development stage of ore-bearing target strata in middle-late Early Cretaceous, main metallogenic stage in Paleogene, and metallogenic cessation and preservation stage in Neogene. In general, there is a favorable potential for the formation of paleophreatic-interlayer oxidation zone type of sandstone uranium deposit in the deep part(<500 m)of the study area. [ABSTRACT FROM AUTHOR]

The Wulong gold district (WGD) is located at the northeastern margin of the North China Carton (NCC) on the Liaodong Peninsula, China. The results of early mineral exploration, mining, and metallogenic modeling research show that gold deposition was associated with lithospheric thinning of the NCC and the emplacement of voluminous Early Cretaceous intrusions. In this study, multi-source information on the ore formation and geology (including geophysical, geochemical, and remote sensing data) was used to construct two-dimensional (2D) prospectivity maps at multiple levels (surface (0 m), − 500 m, − 1000 m, − 1500 m, − 2000 m, − 2500 m, and − 3000 m) for subsurface mineral exploration in the WGD. The methodology employed consists of four steps. Firstly, three-dimensional (3D) geological and geophysical models were constructed using UBC-GIF and SKUA-GOCAD software. 3D geophysical modeling included 3D gravity and magnetic inversions, and 3D resistivity models were based on 2D magnetotelluric (MT) inversion. Secondly, multi-source, ore-forming, and geoscientific data were integrated using radial basis function link net modeling technology within ArcGIS-SDM. Thirdly, multiple-level 2D prospectivity maps were integrated using the discrete smooth interpolation method within the SKUA-GOCAD software to produce 3D prospecting models. Finally, posterior probabilities were classified to delineate 3D exploration targets using the concentration–volume fractal method (GeoCube software, v. 2.0). The results suggest that: (1) the Early Cretaceous intrusions are key ore-forming and ore-controlling objects within the WGD, and a potential target is the western part of the Sanguliu intrusion at depths from 1000 to 3000 m, in the zone where the Wulong and Yangjia gold deposits cross; (2) there are potential targets within 2500 m of the Wulong gold deposit; however, (3) there are no potential targets from 1000 to 3000 m in the Sigdaogou gold deposit. [ABSTRACT FROM AUTHOR]

Sandstone-type U mineral resources are among the important sources for nuclear energy. The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium Mega-Province. Two types of mineralizations are recognized in this basin: "phreatic permeable type" and "interlayer permeable type", both exhibiting features equivalent to roll-front subtypes. The "interlayer permeable type" is widely accepted as the dominant mineralization type for sandstone-type uranium deposits within large-scale basins, also designated as the "interlayer oxidation zone type", based on the horizontal color zoning model representing changing redox conditions. Here we synthesize data from several drill holes within the Ordos Basin, which suggest that major Mesozoic tectonic movements controlled the evolution of the sedimentary system in the basin. These tectonic movements contributed to the formation of three angular unconformities and four parallel unconformities as inferred from the stratigraphic relationships. In addition, other features such as vertical color zoning, paleo-channel controlled tabular or lentoid ore bodies (without roll-type) and a group interlayer horizontal zoning of altered minerals are also documented. Sequence stratigraphic analysis indicates that the Ordos Basin generally witnessed four cycles of water level variations during Mesozoic. During the variations, three high water level and three low water level events were recorded. Biological characteristics imply that the Ordos Basin went through multiple arid to humid climatic evolutions during Mesozoic. Combining the newly documented features with some novel concepts on the hydrodynamic mechanism for supergene ore-forming fluids, we propose a metallogenic model which invokes the importance of tectonic movements and water level fluctuations to explain the genesis of uranium deposits along the northern margin of the Ordos Basin. Image 1 • Rock colors display vertical zoning and correspond to the evolution of sedimentary environments. • The water fluctuation mainly influenced by large-scale water transgression and regression. • The formation of sandstone-type U occurred through tectonic movements induced repeated uplift and subsidence, and alternated anoxic and oxic conditions. [ABSTRACT FROM AUTHOR]