Metallogenic Conditions Research Articles

Geochronology and petrogenesis of Early Mesozoic Rb-mineralized granitic rocks from the Liuzhangshan Rb, West Qinling Orogen Belt, China

ABSTRACT The newly discovered Liuzhangshan (LZS) Rb deposit is a large granite-type deposit in the West Qinling Orogenic Belt (WQOB), spatially associated with biotite monzogranite. Previous research has focused on the geological characteristics and metallogenic conditions of the LZS Rb deposit; however, its geochronology and petrogenesis remain unclear. In this study, monazite U-Pb dating of biotite monzogranite in the LZS deposit yielded a U-Pb age of 200.8 ± 0.9 Ma via laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Combined with the age of magmatic rocks in the WQOB, we propose a potential mineralization event related to Rb around 200 Ma in the WQOB. The biotite monzogranite belongs to weakly peraluminous, high-K calc-alkaline serious, containing high SiO2, Na2O, K2O, and low FeO, MgO, CaO, and P2O5. Compared with primitive mantle and relatively unfractionated granodiorites found in the WQOB, the biotite monzogranite enriched in Rb, Th, U, and Pb, deleted in Ba, Sr, and Ti, and showed negative Eu anomalies, a high Rb/Sr ratio, and a low K/Rb ratio, an ∑REE of 31.3 ppm, an LREE/HREE ratio of 6.48, a LaN/YbN ratio of 2.59, an Mg# of 4.15, and a crystallization temperature of 760°C, the biotite monzogranite also had a high differentiation index (DI = 98.2), apparent tetrad effect (TE 1,3 = 1.12 ~ 1.15), characteristic of highly fractionated I-type granite. Monzoite from the biotite monzogranite in the LZS deposit has negative εNd(t) values ranging from −12.45 to −11.17, and TDM1 of 1569 ~ 2018 Ma, indicating that the LZS biotite monzogranite originated from the partial melting of a Mesoproterozoic ancient basement material, with a minor contribution from mantle-derived melts. Highly differentiated, low Sr and Yb contents, Sr/Yb ratios, and low crystallization temperature magma facilitated the enrichment of Rb.

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

Mineralogical characteristics and fluid inclusions of the Dashuixiabei crystalline graphite deposit in the Dunhuang block

AbstractGraphite is a strategic mineral resource of the world. The Dashuixiabei (DSXB) crystalline graphite deposit is located in the Dongbatu area in the Altyn crystalline graphite metallogenic belt. This study presents data from x‐ray diffraction (XRD), scanning electron microscopy (SEM), laser Raman spectroscopy, and fluid inclusions analysis conducted on the DSXB crystalline graphite deposit. The graphite is flake shaped, with a diameter of 0.1–0.4 mm. A group of extremely complete cleavage was observed under SEM, and the overall distribution was a flake. The C content in graphite is greater than 90 wt%, followed by N, O, and so on. The results of XRD analysis show that the lattice parameters of the DSXB crystalline graphite is a = 0.246–0.2465 nm, c = 0.6714–0.6715 nm, and V = 0.03519–0.03532 nm3. The degree of graphitization ranges from 0.8490 to 0.8519, indicating that the graphite crystal structure is relatively intact, the average metamorphic temperature is 552°C, and the content of 3R polytypes ranges from 13.16% to 13.25%. It is concluded that the metamorphic rocks of the DSXB crystalline graphite deposit have undergone medium‐grade metamorphism. The Raman spectral peaks show that DSXB crystalline graphite has a high degree of crystallinity. The DSXB crystalline graphite ore is dominated by hydrothermal fluids with medium‐low temperature and medium‐low salinity, and the vapor phase of the fluid inclusions is composed of CH4. There may be a superposition of the main and secondary mineralization stages. The crystalline graphite from the DSXB deposit shows high quality and stable ore quality, which has good metallogenic conditions and development and utilization prospects.

Correlation between fractal characteristics of fault structures and metallogenic density in the Nanling area, South China

As fault structures exert a significant effect on metallogenic processes and mineralization, their proper characterization can assist in the determination of target areas for exploration. In this study, we apply the fractal theory on the interpretation of remote sensing images of the Nanling area, South China, to determine the relationship between fault structures and regional mineralization. Our results show that the fractal dimension (D) of fault structures in the Nanling area is 1.72, which is much higher than the regional average (1.35) for southern China. This difference reflects a strong geological tectonic activity in this region. Besides, we find that well-developed faults have a complex spatial distribution, and therefore this region is characterized by favorable metallogenic conditions with good prospecting prospects. Our results indicate the presence of a close relationship between the fractal dimension (D) and the spatial distribution of mineral deposits. Specifically, a higher D value generally corresponds to a dense distribution of ore deposits. Finally, based on regional structural and metallogenic characteristics as well as spatial coupling relationships, two target mineralization areas are identified as potential candidates for further exploration.

A Study on The Tectonic Control and Metallogenic Regularity of The Sanjiang Sanjiang Metallogenic Belt Cobalt Deposit in Yunnan Province

The Sanjiang region of Yunnan is rich in minerals, especially known for gold, copper, lead zinc, and iron ore deposits. There are many genetic types of ore deposits, and most of the ore deposits (points) and anomalies are controlled by the northwest north-south structural belt. The regional tectonic activity is strong and the metallogenic conditions are superior. In this paper, the structural ore-controlling effect and metallogenic regularity of Sanjiang Metallogenic Belt cobalt deposit in Yunnan Province are further studied. The mineralization of the ore belt is most closely related to the Caledonian submarine hydrothermal sedimentation, and after mineralization, it was obviously transformed by Indosinian metamorphism and hydrothermal superposition. Some scholars have carried out relevant research on the geological and geochemical characteristics and genesis of the deposit, and think that the deposit is stratabound-reformed, jet sedimentary, hydrothermal sedimentary-tectonic reformed, etc. However, the chemical properties of ductile rocks are inactive and the permeability is poor, which makes the ore-forming fluid difficult to lose, which is beneficial to the full water-rock reaction between minerals in hydrothermal solution and surrounding rocks flowing through carbonate rocks, resulting in a large number of minerals precipitation and enrichment. When the soft and hard rocks alternate with each other, it is beneficial to form bedding detachment structure to become ore storage space, and it is also beneficial to the precipitation of minerals along the chemical interface and the enrichment of minerals.

Geochronology, pyrite trace elements, and sulfur isotope geochemical characteristics of the Saibagou gold deposit in the eastern part of the northern Qaidam Basin

Introduction: The Saibagou gold deposit, located in the eastern part of the tectonic belt of the northern Qaidam Basin in western China, has its gold ore bodies strictly controlled by the regional fault system. Despite this understanding, there remain controversies surrounding the deposit’s metallogenic epochs, sources of ore-forming materials, and properties of ore-forming fluids. To address these controversy, the metallogenic process of the Saibagou gold deposit can be further determined by analyzing the U-Pb ages of hydrothermal zircons in the gold-bearing quartz veins and investigating the trace element and sulfur isotope compositions of pyrite in the gold deposit.Methods: This study does not focus on the mineral characteristics susceptible to interference by the metallogenic condition in gold ore bodies. Instead, it offers a detailed discussion on stable associated minerals and their indicative markers formed in the process of gold mineralization.Results: The results of this study showed that the metallogenic process of the gold deposit can be categorized into the following stages: 1) quartz–pyrite veins, 2) milky-white quartz—pyrite—native gold veins, 3) hoary quartz—native gold—polymetallic sulfide veins. As indicated by the U-Pb ages of hydrothermal zircons in the gold-bearing quartz veins, the Saibagou gold deposit has two metallogenic ages, namely, 423.91 ± 4.5 Ma (the Silurian) and 470.18 ± 4.92 Ma (the Ordovician).Discussion: The Silurian metallogenic age, predominates and nearly aligns with the expansion of the regional NWW-trending brittle-ductile shear zone, followed by the Ordovician metallogenic age. Data on the trace elements and sulfur isotopes of pyrite, show that the Saibagou gold deposit has similar pyrite compositions in the three metallogenic stages. Gold in the deposit primarily occurs as native gold or minor petzite inclusions and has a very low lattice gold concentration. As indicated by the concentrations of elements such as Co, Ni, and as in the pyrite, as well as the variation range of δ34S values, the ore-forming fluids were derived from low-temperature arsenic-bearing acidic magmas. In addition, the primary ore-forming materials appear to encompass mantle-derived materials from the deep earth.

Occurrence State and Properties of Gold Minerals from the Gold Deposits on the North China Platform

By studying both the microscopic physical and chemical typomorphic characteristics of gold minerals associated with representative gold deposits on the north-central margin of the North China Platform, this paper seeks to identify macroscopic metallogenic mechanisms of gold deposits. The majority of the gold minerals from the gold deposits are native gold with minor electrum and calaverite. The form and grain size of gold minerals from the representative gold deposits reflect the metallogenic properties of medium-deep and medium-high temperature deposits. The projected gold fineness of the Xiaoyingpan gold mine all falls in the medium-temperature area in the figure and tends to be in the high-temperature area, while that of the Zhangquanzhuang gold mine mostly falls in the middle-temperature area, showing the difference in the metallogenic conditions of the two deposits. Both Xiaoyingpan and Zhangquanzhuang gold deposits show the following rules: poor in Zn, Pb, Sb and Se, but rich in Cu, Fe without Mn, indicating that both deposits are of medium-deep origin. The three representative gold deposits all show high gold fineness characteristics, and the general rules are as follows: Dongping-type gold deposit (934.8-969.7) > Xiaoyingpan-type gold deposit (900.0) > Zhangquanzhuang type gold deposit (824.0), showing that the representative gold deposits were formed at higher temperature and deeper depth, and the gold in the ores inherited the characteristics of high gold fineness originating from the Archean metamorphic rock series, which implying that the metallogenic material originated from the ancient metamorphic rock series; the long metallogenic period and multiple metallogenic stages made gold fully transformed, purified and enriched. There are three main occurrence states of gold minerals in the study area, from primary to secondary, they are respectively inclusion gold, gold minerals between other mineral crystals and those filled in the fractures of other minerals.

Occurrence Characteristics of Magnetite and Aeromagnetic Prospecting Northeast of Hebei Province

The occurrence characteristics of magnetite and the methods to quickly and effectively explore are important topics for ore prospecting in the new era. Taking northeast of Hebei Province of China as an example, this article aimed at an important strategic mineral of magnetite, then discussed its distribution characteristics and aeromagnetic exploration methods of it. First of all, we discuss the occurrence characteristics of sedimentary metamorphic and magmatic magnetite. Then, using the latest high-precision aeromagnetic data, combined with the geological outcrops, known iron deposits, ground magnetic surveys, and verification, we studied the relationship between the aeromagnetic anomalies and iron deposits through potential field conversion processing of the reduction to the pole, vertical derivative, upward continuation and residual anomaly, and the forward modeling and inversion methods of 2.5 D optimization fitting. Next, we summarize the metallogenic conditions and attributes of aeromagnetic prospecting and make magnetite predictions. In addition, it has suitable magnetite prospecting potential in the Laochenjia, Dabai, Jiuwuying, Beierying, Sidaogoumen, and Wuyingzi aeromagnetic anomaly regions. In conclusion, these regions have aeromagnetic anomalies with high amplitudes, large scales, and favorable metallogenic backgrounds for magmatic rocks, strata, and structures caused by concealed magnetite. In addition, they have great prospecting potential. Eventually, we hope this research method in this article can provide a reference for magnetite exploration in other areas with similar geological conditions.

Mesozoic Magmatic and Geodynamic Evolution in the Jiaodong Peninsula, China: Implications for the Gold and Polymetallic Mineralization

The intrusive age ranges of Linglong, Guojialing, Weideshan, and Laoshan granites in the Jiaodong Peninsula are 155–154 Ma, 131–130 Ma, 118–111 Ma, and 116 Ma, respectively. Together with the Shidao granite (227–200 Ma), five phases of magmatism can be classified by the time, all of which have different degrees of gold and polymetallic mineralization. The type of granites evolved from A–, S–type to I–, A–type from the Late Triassic to the Early Cretaceous, thus reflects the evolution of geodynamics in the Mesozoic, indicating the switch from North China Craton (NCC)–Yangtze Craton (YC) collision to subduction of the Paleo–Pacific Plate (PPP), with crustal thickening switching to lithospheric thinning and a compressional tectonic setting changing to an extensional setting. It directly leads to a series of extensional structures evolving in the Jiaodong Peninsula and demonstrates affinity for the extensive mineralization in the Early Cretaceous. The key markers of Jiaodong gold and polymetallic mineralization are magmatism, fluid activity and extensional structure. Extensive magmatic uplift and extensional structures in the Early Cretaceous formed the extensional tectonic system. During the formation process, a large proportion of crust and mantle materials exchanged and mixed, and the fluid interaction was highly active, resulting in a magmatic fluid metallogenic system, which provided favorable metallogenic conditions for gold and nonferrous metal hydrothermal deposits. Thus, a large-scale explosive mineralization occurred in Jiaodong in the middle and late Early Cretaceous.

Age, Genesis and Tectonic Setting of the Sayashk Tin Deposit in the East Junggar Region: Constraints from Lu–Hf Isotopes, Zircon U–Pb and Molybdenite Re–Os Dating

The Sayashk tin (Sn) deposit is located within the southern part of the Eastern Junggar orogenic belt in Xinjiang Province and forms part of the Kalamaili alkaline granite belt. There are many Sn polymetallic deposits in the area. To constrain the age, genesis, and tectonic setting of the Sayashk tin deposit in the East Junggar region, we conducted a bulk-rock geochemical analysis of the granite porphyry (SR1) and medium- to fine-grained granite (SR2) hosts of the deposit, LA-ICP-MS zircon U–Pb dating and Lu–Hf isotopic analysis, as well as molybdenite Re–OS dating and combined our results with the metallogenic conditions and other geological characteristics of the deposit. The results show that the Sayashk Sn deposit is indeed spatially, temporally, and genetically closely related to the granite porphyry and medium-fine-grained granite. Both zircon U–Pb ages are 308.2 ± 1.5 Ma and 310.9 ± 1.5 Ma, respectively. The isochron age of molybdenite is 301.4 ± 6.7 Ma, which represents the crystallization age of the granite porphyry and medium-fine-grained granite. Therefore, all of them formed in the late Carboniferous epoch. The medium-fine-grained granites and granite porphyry are characteristically rich in Si and alkali, poor in Ca and Mg, rich in high field-strength elements (HFSE, e.g., Zr, Hf) and Ce, and deficient in Ba, Sr, Eu, P, and Ti. They are typical A-type granites, showing the characteristics of a mixed crustal mantle source. The εHf(t) values of the zircon from the granite porphyry (SR1) range from 10.27 to 16.17 (average 13.71), εHf(t) values of the zircon from the medium-fine-grained granites (SR2) are between 5.72 and 9.21 (average 7.08), and the single model ages (TDM1) and two-stage model ages (TDM2) of the granite porphyry (SR1) fall within the ranges of 319~535 Ma and 339~644 Ma. The single model ages (TDM1) and two-stage model ages (TDM2) of the medium-fine-grained granites (SR2) fall within the ranges of 346~479 Ma and 309~557 Ma. There is little difference between their two-stage model ages and zircon U–Pb ages, indicating that the Sayashk granite may be the product of partial melting of juvenile crustal. Combined with previous research results, the Sayashk Sn deposit formed in a post-collision extensional tectonic setting after the late Carboniferous in the Kalamaili area.

Research on Metallogenic System and Deposit Genesis: With Zhacun Goldmine in Weishan County of Yunnan as an Example

This paper mainly takes Zhacun goldmine as the research object and carries out research on the metallogenic system and genesis of the deposit in the area. The research methods are as follows: according to the geological characteristics of the metallogenic mining area in the Zhacun goldmine, combined with the comparative analysis of the metallogenic age, alteration characteristics and lithology between the Zhacun goldmine and the Lianhuashan alkali rich rock mass, and the analysis of the isotopic data in the Zhacun goldmine, this paper demonstrates that the magmatic activity of the Lianhuashan quartz monzonite porphyry plays an important role in the mineralization of this area, which is both an important ore source and fluid source. It is also the main heat source driving the circulation of ore-forming fluid. On this basis, through the analysis of the metallogenic elements in the area, the metallogenic system model of Zhacun goldmine is constructed. It is considered that under the action of long-term horizontal compressive stress, the atmospheric precipitation infiltrated into the formation continued to penetrate along the fractures and fissures to deep crust and finally mixed with the magmatic water sealed in the thick formation. During this period, a series of shallow and ultrashallow porphyry mass intruded, providing heat source and part of the ore-forming materials and resulting in incomplete homogenization under high temperature and high pressure, which formed highly mineralized mixed water. Under the combined action of long-term compressive stress and various deep thermal dynamics, these mineral fluids migrated along the buried deep faults near the core of the duplex anticline to the upper part of the crust. When the metal elements in these ore fluids migrated over long distances to the nappe fault zone of the gold-bearing fracture zone, the gold began to precipitate, and the native gold and the coarse-grained pyrite and quartz formed at the same time or earlier started to fill the fracture zone along the fissures and accumulate into minerals. Then, through the analysis of metallogenic conditions, gold mineralization process, and genetic mechanism of the deposit, it is proposed that the genetic type of the ore deposit in this area is magmatic mesothermal-epithermal gold deposit. The establishment of metallogenic system model in Zhacun goldmine will provide theoretical and practical guidance for deep and peripheral prospecting prediction in the area, carry out targeted and reasonable prediction, and improve prospecting effectiveness.

PSO-Based ANN for Studying on Carrying Capacity of Iron Ore Resources-Economy-Environment in Southern Shaanxi, China

The southern Shaanxi Province, China, has abundant iron ore resources due to local ideal metallogenic conditions. The development and utilization of iron ore resources and other related industries serve as important pillars of the regional economy. In this paper, principals and methodology of system dynamics are adopted to develop a system model of interactions of development and utilization of mineral resources, social economy, and ecological environment, using the iron ore reserves in the southern Shaanxi region as a resource base, the regional GDP as a benchmark of regional economic development, and the environmental treatment expenditure as the measurement of the regional environmental protection efforts. The model is performed based on an optimized neural network by the particle swarm optimization algorithm. Through setting variables and parameters for the system and model simulation as well as comparative research, this paper analyzes the interconnectivity and interaction of the three subsystems and explores associated relationships among mineral resources, social economy, and environmental carrying capacity in the southern Shaanxi region. In addition, the present study also proposes advice on the development and utilization of iron ore resources, ecological protection, and high-quality development of the economy in the southern Shaanxi region based on the research results.

The ore prospecting prediction model for the Huili copper orefield in Sichuan Province, China

The prediction theory and methodology of ore prospecting were developed from an in-depth study of 129 typical deposits in China. It has been verified to be an effective method that is particularly suitable for the initial ore prospecting. In this method, the internal and external factors of metallogenesis are combined together to construct a geological model of prospecting prediction, which consists of metallogenic geological body, metallogenic structure, metallogenic structural plane and metallogenic characteristics. The Huili area is located in the western margin of the Yangtze Plate, where the regional metallogenic geological conditions are superior, and a series of unique iron-copper deposits were formed. In recent years, great breakthroughs and progress have been made in the deep and peripheral areas of the Huili copper orefield. Herein, we take the Huili copper orefield as a typical example to illustrate the specific application of this method in deep ore prospecting of hydrothermal deposits. The metallogenic geological body is the ore-hosting volcanic rocks (albitite in the Hekou Group), and the main metallogenic structure and structural planes are interfaces between basic (intermediate) volcanic rocks and sedimentary rocks and the possible volcanic vent. Combined with the summary of metallogenic characteristics, we constructed a geological model for ore prospecting in the Huili copper orefield.

Metallogenic model of the Shuangjianzishan Ag-Pb-Zn district, Northeast China: Revealed from integrated geophysical investigation

The Shuangjianzishan deposit in Inner Mongolia is a typical Ag-Pb-Zn deposit of the southern Great Xing’an Range. Proven reserves of Ag, Pb, and Zn in this deposit have reached the scale of super-large deposits, with favorable metallogenic conditions, strong prospecting signs, and high metallogenic potential. This paper reports a study involving integrated geophysical methods, including controlled-source audio-frequency magnetotelluric, gravity, magnetic, and shallow-seismic-reflection methods, to determine the spatial distribution of ore-controlling structures and subsurface intrusive rock for a depth range of <2000 m in the Shuangjianzishan ore district. The objective of this study is to construct a metallogenic model of the ore district and provide a scientific basis for the exploration of similar deposits in the deep and surrounding regions. We used three-dimensional inversion for controlled-source audio-frequency magnetotelluric data based on the limited memory quasi-Newton algorithm, and three-dimensional physical-property inversion for the gravity and magnetic data to obtain information about the subsurface distribution of ore-controlling structures and intrusive rocks. Under seismic reflection results, regional geology, petrophysical properties, and borehole information, the geophysical investigation shows that the Dashizhai group, which contains the main ore-bearing strata in the ore district, is distributed within a depth range of <1239 m, and is thick in the Xinglongshan ore block and the eastern part of the Shuangjianzishan ore block. The mineralization is spatially associated with a fault system characterized by NE-, NW-, and N-trending faults. The magnetic and electrical models identify large, deep bodies of intrusive rock that are inferred to have been involved in mineralization, with local shallow emplacement of some intrusions. Combining the subsurface spatial distributions of ore-bearing strata, ore-controlling faults, and intrusive rock, we propose two different metallogenic models for the Shuangjianzishan ore district, which provide a scientific basis for further prospecting in the deep regions of the ore district and surrounding areas.

Variable Modes of Formation for Tonalite–Trondhjemite–Granodiorite–Diorite (TTG)-related Porphyry-type Cu ± Au Deposits in the Neoarchean Southern Abitibi Subprovince (Canada): Evidence from Petrochronology and Oxybarometry

Abstract Most known porphyry Cu ± Au deposits are associated with moderately oxidized and sulfur-rich, calc-alkaline to mildly alkalic arc-related magmas in the Phanerozoic. In contrast, sodium-enriched tonalite–trondhjemite–granodiorite–diorite (TTG) magmas predominant in the Archean are hypothesized to be unoxidized and sulfur-poor, which together preclude porphyry Cu deposit formation. Here, we test this hypothesis by interrogating the causative magmas for the ~2·7 Ga TTG-related Côté Gold, St-Jude, and Clifford porphyry-type Cu ± Au deposit settings in the Neoarchean southern Abitibi subprovince. New and previously published geochronological results constrain the age of emplacement of the causative magmas at ~2·74 Ga, ~2·70 Ga, and ~ 2·69 Ga, respectively. The dioritic and trondhjemitic magmas associated with Côté Gold and St-Jude evolved along a plagioclase-dominated fractionation trend, in contrast to amphibole-dominated fractionation for tonalitic magma at Clifford. Analyses of zircon grains from the Côté Gold, St-Jude, and Clifford igneous rocks yielded εHf(t) ± SD values of 4·5 ± 0·3, 4·2 ± 0·6, and 4·3 ± 0·4, and δ18O ± SD values of 5·40 ± 0·11 ‰, 3·91 ± 0·13 ‰, and 4·83 ± 0·12 ‰, respectively. These isotopic signatures indicate that, although these magmas are mantle-sourced with minimal crustal contamination, for the St-Jude and Clifford settings the magmas or their sources may have undergone variable alteration by heated seawater or meteoric fluids. Primary barometric minerals (i.e. zircon, amphibole, apatite, and magnetite–ilmenite) that survived variable alteration and metamorphism (up to greenschist facies) were used for estimating fO2 of the causative magmas. Estimation of magmatic fO2 values, reported relative to the fayalite–magnetite–quartz buffer as ΔFMQ, using zircon geochemistry indicates that the fO2 values of the St-Jude, Côté Gold, and Clifford magmas increase from ΔFMQ –0·3 ± 0·6 to ΔFMQ +0·8 ± 0·4 and to ΔFMQ +1·2 ± 0·4, respectively. In contrast, amphibole chemistry yielded systematically higher fO2 values of ΔFMQ +1·6 ± 0·3 and ΔFMQ +2·6 ± 0·1 for Côté Gold and Clifford, respectively, which are consistent with previous studies that indicate that amphibole may overestimate the fO2 of intrusive rocks by up to 1 log unit. Micro X-ray absorption near edge structure (μ-XANES) spectrometric determination of sulfur (i.e. S6+/ΣS) in primary apatite yielded ≥ΔFMQ −0·3 and ΔFMQ +1·4–1·8 for St-Jude and Clifford, respectively. The magnetite–ilmenite mineral pairs from the Clifford tonalite yielded ΔFMQ +3·3 ± 1·3 at equilibrium temperatures of 634 ± 21 °C, recording the redox state of the late stage of magma crystallization. Electron probe microanalyses revealed that apatite grains from Clifford are enriched in S (up to 0·1 wt%) relative to those of Côté Gold and St-Jude (below the detection limit), which is attributed to either relatively oxidized or sulfur-rich features of the Clifford tonalite. We interpret these results to indicate that the deposits at Côté Gold and Clifford formed from mildly (~ΔFMQ +0·8 ± 0·4) to moderately (~ΔFMQ +1·5) oxidized magmas where voluminous early sulfide saturation was probably limited, whereas the St-Jude deposit represents a rare case whereby the ingress of externally derived hydrothermal fluids facilitated metal fertility in a relatively reduced magma chamber (~ΔFMQ +0). Furthermore, we conclude that variable modes of formation for these deposits and, in addition, the apparent rarity of porphyry-type Cu–Au deposits in the Archean may be attributed to either local restriction of favorable metallogenic conditions, and/or preservation, or an exploration bias.

Sphalerite as a record of metallogenic information using multivariate statistical analysis: Constraints from trace element geochemistry

In this study, the dominant geological factor that influences the element distribution in sphalerite was determined and the behaviors of the elements under a single factor were investigated (e.g., temperature). To this end, two multivariate statistical analysis methods, namely, principal component analysis (PCA) and factor analysis (FA), were performed on a published sphalerite dataset containing 1336 analysis points from 52 deposits. The PCA produced five element clusters, which were each controlled by the five dominant factors identified by the FA (including magmatic-derived materials, temperature, pH, element remobilization, and dynamic recrystallization). Furthermore, the influence of temperature on the trace element composition of sphalerite was quantitatively expressed based on the corresponding homogenization temperature of fluid inclusions from 27 deposits, i.e., TFAS (°C) = (32.22 ± 1.88) × FAS + (245.49 ± 3.79) (Ra2 = 0.918). The above research was then applied to the sphalerite from the Baoshan Cu-Pb-Zn deposit to reveal its metallogenic conditions. The results indicate that from the central-western mining districts to the northern mining districts, the contributions of the magmatic-derived materials, temperature, and fO2 decrease, whereas the contributions of the basement-derived hydrothermal fluid and pH increase.

Genesis of the Bieyesamas Monzogranite of the Altay Mountain, Xinjiang, Northwestern China, and Its Rare Metal Resource Potential

Lying in the Altay Orogenic Belt in Xinjiang, Northwestern China, the Bieyesamas monzogranite pluton is located in the North Altay Terrane. It is one of the important granitic batholiths with a large amount of rare metal pegmatite dikes. According to LA-ICP-MS zircon U-Pb isotopic dating, the 206Pb/238U weighted average age of the Bieyesamas monzogranite is 451.1 ± 5.1 Ma ( MSWD = 6.0 ), indicating the formation age of Late Ordovician. The Bieyesamas monzogranite has secondary minerals such as garnet and tourmaline. The geochemical analysis shows that the pluton is characterized by high SiO2 (70.45%~75.44%), Al2O3 (14. 04%~17.14%), potassium and alkaline ( K 2 O = 4.20 % ~ 4.78 % , N a 2 O + K 2 O = 7.90 % ~ 8.99 % ), A/CNK (1.16~1.28), and high corundum (2.33%~5.08%) being found in CIPW standard minerals, belonging to high-K calc-alkaline peraluminous series. The pluton is enriched in LREE, depleted in HREE ( LREE / HREE = 5.99 ~ 9.65 ), with obviously negative Eu anomaly ( δ Eu = 0.44 ~ 0.60 ), while the trace elements are characterized by Rb, K, Nb, Ta, Hf, and U enrichment and Ba, Sr, Ti, and Zr depletion, as well as with high differentiation index ( DI = 93.24 % ). Zircon ε Hf t values range from 2.89 to 7.69, with the corresponding two-stage model ages ( T DM 2 ) of 941~1257 Ma. The mineral assemblage, geochemical characteristics, and zircon Hf isotope indicate the pluton experienced the highly fractionated process and belongs to highly fractionated S-type granite, which was formed by partial melting of the Meso- to Neoproterozoic crustal material. In the Bieyesamas monzogranite, the average contents of rare metals are obviously higher ( Li = 550 × 10 − 6 , Be = 10.18 × 10 − 6 , Nb = 18.91 × 10 − 6 , Ta = 2.14 × 10 − 6 , Rb = 500 × 10 − 6 , and Cs = 149.9 × 10 − 6 ) than the other rocks and Clark values of crust, which indicates that the Bieyesamas pluton has the enrichment potential of rare metals. The metallogenic geological conditions are superior in the Bieyesamas area of the Altay Mountain, and rare metal deposits and ore spots are widely distributed. In particular, the newly discovered rare metal deposits are characterized by large-scale mineralization, high grade and industrial utilization value, etc. It is preliminarily predicted that they have reached the medium-scale deposits. Therefore, the Bieyesamas area is one of the key areas for rare metal prospecting breakthroughs in the future, with great potential for rare metal mineral resources.

Petrogenesis and metallogenic potential of the early devonian Yugusayi mafic-ultramafic complex in Qimantagh, East Kunlun orogeic belt

ABSTRACT The Yugusayi mafic-ultramafic complex, located in the Qimantagh area, East Kunlun orogenic belt, consists of harzburgite, olivine orthopyroxenite, hornblende pyroxenite, and hornblende gabbro, which were once considered to be a part of the Early Palaeozoic ophiolite suite. However, the Yugusayi mafic-ultramafic rocks are characterized by thermal emplacement, accompanied by Cu-Ni sulphide mineralization, which is different from typical ophiolite suite. The LA-ICP-MS zircon U-Pb dating yields a 405 ± 2.8 Ma age for the hornblende gabbro, which belongs to the Early Devonian. All rocks are enriched in LREE but depleted in HREE, with a characteristic of ferrous mafic-ultramafic rocks. The εHf(t) values of the zircons from hornblende gabbro are 5.6–14.8, the εNd(t) values of whole rocks are from −4.27 to 0.08, and the δ34S values of sulphide are 1.36–8.72‰, indicating that the magma originated from the depleted mantle and contaminated by continental crust material during the ascending process. Based on the regional geological background, it is reasonable that the rocks formed in the post-collision extension stage after the closure of the Proto-Tethys Ocean and the continental collision, which represents an important metallogenic period for Cu-Ni sulphide deposits in the East Kunlun oregenic belt. Early Devonian magmatic mafic-ultramafic intrusions are developed in the early Palaeozoic ophiolitic tectonic melange belt of Qimantagh area. Combined with good metallogenic conditions and remarkable mineralization characteristics, it is believed that the Qimantagh area is a potential area for the prospecting of magmatic Cu-Ni sulphide deposits.

Characteristics and significance of aegirine and arfvedsonite in Boziguoer Nb-Ta-Zr-Rb-REE deposit related to alkaline granite, Xinjiang

碱性造岩矿物能够记录碱性岩源区特征、岩浆演化以及晚期成矿的重要信息，是开展碱性岩成岩成矿研究的有效手段。波孜果尔碱性花岗岩型铌-钽-锆-铷-稀土矿床位于塔里木北缘-中亚南天山晚古生代造山带，是塔里木地块北缘铌成矿带中典型的碱性岩型矿床。本文通过对含矿岩体中的霓石和钠铁闪石开展矿物学研究，结合全岩成分揭示波孜果尔稀有-稀土金属矿床含矿岩体的岩石类型、演化特征、构造背景及成矿条件。研究发现，含矿碱性岩体由霓石钠铁闪石碱长花岗岩、霓石钠铁闪石石英碱长正长岩、霓石钠铁闪石碱长正长岩组成。不同岩相岩石均表现出相似的稀土和微量元素配分模式，以富集轻稀土元素和高场强元素，亏损大离子亲石元素和重稀土元素为特征，具有显著的负Eu异常，指示三种岩石类型是同源岩浆演化的产物。含矿岩体中的辉石为霓石-霓辉石，角闪石为钠铁闪石。霓石和钠铁闪石稀土和微量元素配分模式相似且含量都较低，富集重稀土、亏损轻稀土，具有显著的负Eu异常，并富集Zr、Hf等高场强元素，亏损Ba、Sr等大离子亲石元素。霓石和钠铁闪石微量元素特征指示三个岩相单元的演化程度由低到高依次为霓石钠铁闪石碱长花岗岩→霓石钠铁闪石石英碱长正长岩→霓石钠铁闪石碱长正长岩，且结晶分异作用控制了岩体的形成。同时，早期霓石钠铁闪石碱长花岗岩的钠铁闪石呈现Ce正异常，晚期岩相中则无异常，指示演化的早期阶段氧逸度较高，随着磁铁矿等氧化物的结晶熔体趋于还原。波孜果尔含矿岩体成矿元素除Rb外分布并不均匀，表现为演化早期的岩相富集Nb，而演化晚期的岩相更富集稀土和Zr。进一步研究发现，塔里木北缘碱性岩带发育的铌、稀土、钽、锆、铷、铀等稀有稀土金属矿化与地幔柱引起的幔源岩浆底侵有关，其构造背景可能为地幔柱对造山带的叠置。;Alkaline minerals can record the important information of source area characteristics, magmatic evolution and late mineralization of alkaline rocks, which is an effective means for the study of diagenesis and mineralization of alkaline rocks. Boziguoer Nb-Ta-Zr-Rb-REE deposit is a typical deposit related to alkaline rocks, which is located in the Late Paleozoic orogenic belt of the southern Tianshan-the northern margin of Tarim block. Based on mineralogical study of aegirine and arfvedsonite in the ore-bearing intrusion, combining with its whole rock compositions, this paper reveals the rock types, evolution characteristics, tectonic setting and metallogenic conditions of the intrusion in the Boziguer rare-earth metal deposit. The rock types of ore-bearing intrusion are aegirine arfvedsonite alkali feldspar granite, aegirine arfvedsonite quartz alkali feldspar syenite and aegirine arfvedsonite alkali feldspar syenite. All of the three types of rocks show similar REE and trace element distributions, with enriched LREE and HFSE, depleted HREE and LILE, and a significant negative Eu anomaly, indicating that they are the products of homologous magmatic evolution. The pyroxene group minerals are aegirine, and the amphibole group minerals are arfvedsonite. Aegirine and arfvedsonite show similar distribution patterns of trace and rare earth elements, which are characterized by enriched HREE and depleted LREE with a significant Eu negative anomaly. They all show enrichment in HFSE (Zr, Hf), depletion in LILE, such as Ba and Sr. Trace element and REE distributions of these minerals indicate that the degree of their evolution from low to high is: aegirine arfvedsonite alkali feldspar granite→aegirine arfvedsonite quartz alkali feldspar syenite→aegirine arfvedsonite alkali feldspar syenite, showing the formation of the intrusion is controlled by crystallization and differentiation. The arfvedsonite of aegirine arfvedsonite alkali feldspar granite shows a positive anomaly of Ce, indicating a high oxygen fugacity environment at the early stages of its evolution. The crystallization of magnetite in the early lithofacies make the evolution environment of the melt tend to be reduced. The Rb in all rock types is equally distributed, and the rocks of early evolution stage is more enriched in Nb, while that of the late-stage more enriched in REE and Zr. The mineralization of rare earth metals such as Nb, REE, Ta, Zr, Rb and U developed in the alkaline rock belt in the northern margin of Tarim basin is related to the mantle magma underplating caused by mantle plume, and its tectonic setting may be the superposition of mantle plume to orogenic belt.

Characteristics of Uranium Mineralization in Red Clastic Formations in the Southwestern Margin of the Ordos Basin

AbstractIn the southwestern margin of the Ordos Basin, uranium mineralization is primarily hosted by predominantly oxidative red clastic formations in the Lower Cretaceous. The main target layers for uranium exploration are the Madongshan and Liwaxia formations of the Liupanshan Group, followed by the Jingchuan Formation of the Zhidan Group. The host rocks (medium‐fine feldspar quartz sandstone), which are bleached to a light grayish white color, contain a minor organic matter component and pyrite. Uranium mineralization changes from surficial infiltration or phreatic oxidation in the upper part to interlayer oxidation in the lower part. Uranium ore bodies are mostly lenticular or tabular in shape, locally shaped like crescent rolls. Individual ore bodies are typically small and shallow. Uranium predominantly manifests as pitchblende and coffinite. Coffinite is usually short and columnar or granular in habit, whereas pitchblende occurs as an irregular colloidal covering on the surface or in fissures of ferric oxide, silicate, clay or carbonate. Secondary uranium minerals are torbernite, uranophane, and uranopilite. Minerals associated with uranium are mainly pyrite, chalcopyrite and, to a minor extent, arsenopyrite and fluorite. The associated elements are Mo, V, Se, Co, Ni, and Mn, the host sandstone being high in Cu and Ba. Overall, the red clastic formations in the southwestern margin of the Ordos Basin are characterized by ‘five multiples but one low’ which means multiple target layers, multiple stages of mineralization, multiple ore body shapes, multiple kinds of uranium minerals, multiple associated elements, but low organic matter. This implies an overall complex uranium metallogenic environment and mineralization process. It is recommended that future uranium exploration should take into consideration regional metallogenic conditions and mineralization features, with target layers in the wide‐smooth synclinal slope being focused on. Most uranium deposits are small to medium in size, and the main type of uranium mineralization can vary by target layer.