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Article

Genesis of the Beizhan Iron Deposit in Western Tianshan, China: Insights from Trace Element and Fe-O Isotope Compositions of Magnetite

by
Yan Li
1,2,
Zongsheng Jiang
1,*,
Dachuan Wang
3,
Zuoheng Zhang
4 and
Shigang Duan
1
1
MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
2
School of Gemmology, China University of Geosciences, Beijing 100083, China
3
Institut für Mineralogie, Leibniz Universität Hannover, 30167 Hannover, Germany
4
Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China
*
Author to whom correspondence should be addressed.
Minerals 2024, 14(3), 304; https://doi.org/10.3390/min14030304
Submission received: 4 February 2024 / Revised: 25 February 2024 / Accepted: 28 February 2024 / Published: 14 March 2024
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Abstract

:
The Beizhan iron deposit (468 Mt at an average grade of 41% Fe) is the largest iron deposit in the Awulale iron metallogenic belt of Western Tianshan, northwest China. The high-grade magnetite ores are hosted in the Carboniferous volcanic rocks with extensive development of skarn alteration assemblages. While considerable progress has been made in understanding the characteristics of Beizhan and its genetic association with volcanic rocks, the genetic models for ore formation are poorly constrained and remain controversial. This study combines detailed petrographic investigations with in situ LA-ICP-MS analyses of trace elements and Fe-O isotope compositions of magnetite to elucidate the origin of magnetite and the conditions of ore formation. The trace element concentrations in magnetite unveil intricate origins for various ore types, implying the precipitation of magnetite from both magmatic and hydrothermal fluids. The application of the Mg-in magnetite thermometer (TMg-mag) reveals a notable temperature divergence across different magnetite varieties, spanning from relatively higher temperatures in magmatic brecciated magnetite (averaging ~641 and 612 °C) to comparatively lower temperatures in hydrothermal platy magnetite (averaging ~552 °C). The iron isotopic composition in massive and brecciated magnetite grains, characterized by lighter δ56Fe values (ranging from −0.078 to +0.005‰ and −0.178 to −0.015‰, respectively), suggest a magmatic or high-temperature hydrothermal origin. Conversely, the heavier δ56Fe values observed in platy magnetite (+0.177 to +0.200‰) are attributed to the influence of pyrrhotite, signifying late precipitation from low-temperature hydrothermal fluids. Additionally, the δ18O values of magnetite, ranging from +0.6 to +4.6‰, provide additional evidence supporting a magmatic–hydrothermal origin for the Beizhan iron deposit. Overall, the identified genetic associations among the three magnetite types at Beizhan provide valuable insights into the evolution of ore-forming conditions and the genesis of the deposit. These findings strongly support the conclusion that the Beizhan iron deposit underwent a process of magmatic–hydrothermal mineralization.

1. Introduction

The Awulale iron metallogenic belt (AIMB) in Western Tianshan, NW China, hosts several large-tonnage magnetite deposits that are closely associated with the coeval Carboniferous calc-alkaline volcanic and plutonic rocks (Figure 1) [1]. These deposits collectively have a total resource exceeding 1200 million metric tons (Mt) of Fe [2] with a significant proportion of high-grade ores, providing attractive targets for the exploration and exploitation of iron in China. As a group, these deposits share many geological, mineralogical, and geochemical similarities with the volcanic-hosted iron oxide–apatite (IOA) deposits and magnetite-only deposits in, for example, the Chilean iron belt [3,4,5,6,7,8] and Southeast Missouri, USA [9,10,11]. Although the genetic link between volcanic processes and ore deposit formation seems to be unequivocal, the large variability of mineralogical characteristics found in these deposits has resulted in several disagreements regarding their origin and classification [12].
The Beizhan iron deposit, with a total resource of 468 Mt at 41% Fe [16], ranks among the largest iron deposits in the AIMB. It was previously considered to be a submarine volcanic-hosted iron deposit [2] or an iron skarn deposit [13,16,17]. Pan et al. [18] proposed that the iron ores in the carbonate rocks at Beizhan are sedimentary in origin and overprinted by later hydrothermal mineralization. More recently, Li et al. [19] identified coexisting IOA and iron skarn ores proximal to a dioritic–granitic intrusion and suggested that the IOA ores likely formed from high-temperature hydrothermal fluids from the dioritic intrusion, while the iron skarn ores originated from a relatively low-temperature and more evolved hydrothermal fluid. These varying interpretations highlight the complexity of the iron mineralization at Beizhan and emphasize the need for a better understanding of the ore-forming processes.
In this study, we investigated the chemistry of magnetite by using an electron probe micro analyzer (EPMA) and laser ablation inductively coupled mass spectroscopy (LA-ICP-MS) to classify compositional types of magnetite and unravel the genesis of iron mineralization at Beizhan. The formation temperatures of magnetite were obtained by applying the Mg-in magnetite thermometer (TMg-mag) [20], which further gives key insights into the ore-forming processes. Furthermore, we use the Fe and O isotopes of magnetite to fingerprint the source of metals and ore fluids in the deposit.

2. Geological Background

2.1. Geologic Setting of Western Tianshan

Western Tianshan represents the western segment of the Tianshan orogenic belt, which forms part of the southwestern margin of the Central Asian Orogenic Belt (CAOB) [15]. It is subdivided, from north to south, into four tectonic terranes—the North Tianshan Accretionary Complex, the Yili Block, the Central Tianshan Arc Terrane, and the South Tianshan Accretionary Complex—each separated from the other by major suture zones and regional-scale strike–slip faults (Figure 1a) [21,22,23,24].
The Yili Block is underlain by a Precambrian basement, which comprises Proterozoic gneisses, schists, carbonates, and clastic rocks [14,21,24]. Granitic gneisses with U–Pb zircon ages of 1609 ± 40 Ma [25] and 919 ± 6 Ma [26] were reported in the northern margin of the Yili Block and represent the oldest magmatic events in Western Tianshan. These basement rocks are overlain by Mesoproterozoic to Phanerozoic marine sedimentary and volcanic sequences and intruded by numerous Neoproterozoic to Permian granitoids [14,24]. The closure of three Paleozoic oceans (the Terskey, South Tianshan, and North Tianshan oceans) during the Neoproterozoic to Paleozoic led to the amalgamation of the Yili Block with other terranes and the eventual formation of the Tianshan orogenic belt [24,27,28].
A large variety of mineral deposits are associated in space and time with the Late Paleozoic volcanic and subvolcanic rocks (Figure 1a), including porphyry Cu–(Mo) deposits, epithermal Au deposits [29], and volcanic-hosted iron oxide deposits [2,30].

2.2. Iron Mineralization in Western Tianshan

In the eastern section of Western Tianshan, a cluster of iron oxide deposits constitute an approximately 250 km long and 20 km wide iron belt, referred to as the Awulale iron metallogenic belt (Figure 1a). The AIMB has a collective resource of 1200 Mt [2] and represents one of the most substantial accumulations of high-grade iron ore in China [31].
These iron deposits primarily occur within the Carboniferous volcanic rocks of the Dahalajunshan Formation. Most iron deposits, such as Zhibo, Beizhan, and Chagangnuoer, are dominated by Ti-poor magnetite as the only economically extractable metal, except for the Dunde deposit, where significant zinc and gold mineralization occur around the magnetite ore bodies. Magnetite mineralization in these deposits was accompanied by extensive alteration, primarily involving Ca, Na, and K metasomatism, but differ in terms of alteration assemblages [32,33,34,35,36], possibly related to the differences in chemical composition of host rocks and ore-forming fluids. Several proposed genetic models for these deposits include skarn, volcanic–hydrothermal, hydrothermal replacement of volcanic rocks, and exhalative–sedimentary in origin [13,16,37,38]. Based on in situ trace element and Fe isotope analysis of magnetite from the Zhibo and Chagangnuoer deposits, Günther et al. [12] proposed that most massive ores have an ortho-magmatic origin, while re-precipitated skarn-type iron ore is of hydrothermal origin.
The distribution of these deposits appears to be controlled by several volcano-hydrothermal centers in the region. Iron ore mineralization in lavas is typically observed in close proximity to the volcanic vent, while in pyroclastic–sedimentary rocks, it tends to occur at a more distal location [39]. Radiometric dates, including the Ar-Ar ages of muscovite, the Re-Os ages of pyrite, the Sm-Nd ages of garnet, and the U-Pb ages of titanite, demonstrate that iron mineralization mainly occurred around 330–300 Ma [33,36,40,41], overlapping ages for the host volcanic rocks [42,43,44,45]. The close spatial and temporal association, coupled with geological and geochemical evidence, strongly support a genetic link between the ore deposit and the host volcanic rocks [41].

3. Geology of the Beizhan Iron Deposit

The Beizhan iron deposit is situated on the northern limb of the Gongnaisi synclinorium, located in the eastern sector of the AIMB (Figure 1b) [32,40]. The deposit has undergone significant folding and faulting, resulting in complex crustal structures (Figure 2). Nine major compressional faults have been identified within the deposit. The presence of a volcano in the deposit is evidenced by effusive eruptions of andesitic lavas, explosive eruptions of tuff units, and the development of caldera structures, which are associated with the development of ring faults and dikes [46].
The Carboniferous Dahalajunshan Formation that hosts the deposit comprises basaltic andesite, andesite, dacite, rhyolite, limestone, basaltic tuff, and andesitic–rhyolitic tuff (Figure 2). Zircon U-Pb dating of the basaltic andesite and dacite has provided ages of 320.6 ± 2.2 Ma and 329.1 ± 1.0 Ma [49,50]. The volcanic rocks have been intruded by Late Carboniferous K-feldspar granite, diabase dike, and diorite. The geochemical and geological features of these igneous rocks suggest that the volcanic suites erupted in a continental arc setting, while the Late Carboniferous granites, diabase, and diorite dikes formed in an extensional setting [51].
The Beizhan deposit comprises six magnetite orebodies (L1–L6) that are generally concordant with the wall rocks. L3 is the dominant orebody and contains ~99% of the total ore resources of the deposit. The total iron content (TFe) of the ore body varies from 23% to 64.3%, with an average of 40.5%. The orebody is lensoid, veined, and stratiform, strikes northwest, and dips 37° to 40° to the north (Figure 2c). It extends over a strike length of about 880 m and a vertical extent of over 300 m, with a thickness up to 295 m in the deeper levels.
The magnetite mineralization dominantly occurs as massive, disseminated, brecciated, and vein ores (Figure 3 and Figure 4). The massive ores represent the high-grade component of the mineralization and are composed predominantly of euhedral to subhedral granular magnetite with interspersed pyrite and silicate minerals (Figure 3a–c and Figure 4a,b). Disseminated ores are widespread in the mineralization zones but commonly occur in proximity to massive ores or in the host rock surrounding the veins (Figure 3d,e). In disseminated ores, magnetite occurs as disseminated subhedral to anhedral grains intergrown with gangue minerals (Figure 4c). Platy magnetite is also present in disseminated ores in association with platy pyrrhotite (Figure 3f). The brecciated ores are defined by subangular fragments of volcanic rocks embedded in a magnetite matrix, with locally observed potassic and silicic alteration in the host rock fragments (Figure 3g,h and Figure 4d). Locally, magnetite occurs as veins and fracture fillings in altered country rocks (Figure 3i).
The gangue minerals are predominantly composed of calcite, ankerite, chlorite, serpentine, tourmaline, epidote, actinolite, and phlogopite with minor garnet, diopside, forsterite, titanite, and apatite. Pyrrhotite and pyrite are the most common sulfides, while chalcopyrite is typically present in trace amounts (Figure 4e,f).
The paragenetic sequence of the Beizhan iron deposit was subdivided into four stages based on field and petrographic observations (Figure 5). The skarn stage (I) is characterized by the development of skarn minerals, including garnet, diopside, and forsterite. The magnetite stage (II) represents the primary stage of magnetite mineralization, accompanied by minor precipitation of hematite, apatite, actinolite, and tremolite. The sulfide stage (III) is marked by veins of sulfide minerals such as pyrrhotite, pyrite, sphalerite, and chalcopyrite, often closely associated with magnetite ore. The chlorite-carbonate stage (IV) is represented by the formation of carbonate, chlorite, and serpentine, along with small quantities of magnetite and hematite.

4. Analytical Methods

4.1. Electron Microprobe Analyses

Major element analyses of magnetite were conducted utilizing a JEOL JXA-8230 electron microprobe at the Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing. The analytical parameters were set with an acceleration voltage of 15 kV, a beam current of 20 nA, and a defocused electron beam diameter of 5 μm. Calibration standards included both natural and synthetic minerals, including Woll MAC (Si and Ca), jadeite (Na), kyanite (K), and synthetic TiO2, Fe2O3, MgO, and Mn3O4. Data reduction was executed through the ZAF correction method of the JEOL microprobe system. Analytical precision is better than 0.01%.

4.2. In Situ Magnetite Trace Element Analyses

In situ trace element analyses of magnetite were completed using a high-mass-resolution Agilent 7500a ICP-MS, coupled with a New Wave UP 193SS laser ablation system at the LA-ICP-MS laboratory, China University of Geosciences, Beijing. The laser ablation system utilized a beam spot of 50 μm and an energy beam of 8.5 J/cm2. Helium was employed as the carrier gas with a flow rate of 0.8 L/min, while argon served as the make-up gas with a flow rate of 1.15 L/min. Nitrogen gas was introduced at a flow rate of 15 L/min into the central gas flow (Ar + He) of the argon plasma to enhance detection limits and improve precision. Standard analyses were performed three times before and after each run of ten analyses to ensure accuracy and reliability. The preferred element concentration values for the USGS reference glasses were derived from the GeoReM database. External calibration was achieved using the NIST SRM 612 standard glass, while internal standardization was based on Fe. The raw data obtained from the ICP-MS instrument were exported and processed using the Glitter 4.4 software. The detection limits for most elements were considerably below 0.1 ppm.

4.3. Magnetite Thermometry Calculation

Canil and Lacourse [18] established a method for quantitatively estimating temperature based on the trace element concentrations of magnetite. This method, known as magnetite thermometer (TMg-mag), utilizes Mg and Fe concentrations to express temperature as follows:
TMg-Mag (°C) = −8344 (±320)/[ln XMg − 4.13 (±0.28)] − 273
where
XMg = Mg/(Mg + Fetotal)
The error associated with this temperature calculation is ±50 °C. The calibration is based on the analysis of magnetite in equilibrium with fluid-saturated and undersaturated silicate melts in over 300 experiments from 27 different phase equilibrium studies, encompassing compositions ranging from basalt to granite.

4.4. Fe-O Isotope Analyses

Iron isotopes in magnetite were analyzed at the Iron Isotope Laboratory of the University of Science and Technology of China. Dissolution of separated magnetite crystals was carried out using 0.8 mL of high-purity hydrofluoric acid (HF) and 0.4 mL of high-purity nitric acid (HNO3). The analytical procedure was described in detail by Huang et al. [52]. Iron isotopic compositions were calculated using the International Atomic Energy Agency reference material IRMM-014, with the formula as follows:
δ56Fe = [(56Fe/54Fe) sample/(56Fe/54Fe) IRMM-014 − 1] × 1000 (‰)
The average standard deviation of sample measurements (2σ) was 0.04‰.
Oxygen isotopes in magnetite were analyzed at the Key Laboratory of Isotope Geology, Ministry of Land and Resources, using a Finnigan MAT-253 mass spectrometer. Oxygen extraction followed the BrF5 analytical method as described by Clayton and Mayeda [53]. The liberated oxygen was then reacted with a hot platinized graphite rod at 700 °C, producing CO2. Oxygen isotopic compositions were determined by analyzing the CO2 gas using a mass spectrometer. Reference materials GBW 04409 and NBS-28 were used as standards. The analytical precision for δ18O values was reported as ±0.2‰ (2σ). All the oxygen isotopic data were reported relative to the Vienna Standard Mean Ocean Water (V-SMOW) reference standard, following this formula:
δ18O = [(18O/16O) sample/(18O/16O) VSMOW − 1] × 1000 (‰)

5. Results

5.1. Mineral Chemistry of Magnetite

The major element compositions of the three magnetite types are presented in Table 1. The FeOTotal content exhibits a general decreasing trend from platy magnetite and brecciated magnetite to massive magnetite, with average values of 93.53 wt.%, 93.26 wt.%, and 91.74 wt.%, respectively. In contrast, the content of Al2O3; and MgO display an opposing trend, progressively increasing from platy magnetite (averaging 0.15 wt.% and 0.11 wt.%) to brecciated magnetite (averaging 0.33 wt.% and 0.30 wt.%) and finally to massive magnetite (averaging 0.79 wt.% and 0.33 wt.%). Other minor elements such as TiO2 and Cr2O3 had low concentrations, typically less than 0.1 wt.%.
The trace element compositions of magnetite are presented in Table 2 and illustrated in Figure 6. Notably, the content of Ti and V in brecciated magnetite is about 1990 ppm and 87 ppm, respectively, which is around four times higher than those in the other two magnetite types. Likewise, the Cr, Co, and Zn contents exhibited notable enrichment in brecciated magnetite, approximately two times higher relative to those in the other magnetite varieties.
In contrast, platy magnetite displayed the highest Cu content, while the Sr content was predominantly enriched in massive magnetite. For the remaining trace elements, no significant differences were observed among the various magnetite types. The rare earth element content across the different magnetite types was relatively modest; however, brecciated magnetite showed a narrow concentration range, while platy magnetite exhibited slightly greater variability. Massive magnetite demonstrated the most extensive variations compared to the other two magnetite types.

5.2. Precipitation Temperature of Magnetite

The precipitation temperatures of various magnetite types from the Beizhan deposit are illustrated in Figure 7a. Additionally, the average concentrations of Ti, V, and Ga in these magnetite types are plotted in Figure 7b. The calculated temperatures for magnetite precipitation in the Beizhan deposit span a range from approximately 403 °C to 723 °C. Specifically, the massive and brecciated magnetite yield a similar temperature range, spanning approximately 566 to 678 °C (with an average of 612 °C) and 519 to 723 °C (with an average of 641 °C), respectively, both higher than those of platy magnetite, ranging from approximately 403 to 581 °C, with an average of 552 °C (except for an erratic value of 403 °C).

5.3. Fe-O Isotopic Composition of Magnetite

The Fe-O isotopic compositions of various magnetite types from the Beizhan iron deposit are provided in Table 3 and Figure 8a,b. For the brecciated ores, the δ56Fe values range from −0.178‰ to −0.015‰, with an average value of −0.073‰. The massive ores exhibited δ56Fe values of −0.078‰ to +0.005‰, with an average value of −0.049‰. Platy ores displayed δ56Fe values of +0.177‰ to +0.200‰, averaging at +0.189‰.
The δ18O values of magnetite exhibited notable variations, ranging from +0.6‰ to +4.6‰. Specifically, the δ18O values of three brecciated magnetite samples were +1.2‰, +2.4‰, and +4.5‰, with an average value of +2.7‰. The δ18O values of four massive magnetite samples were +1.5‰, +2.4‰, +2.5‰, and +4.6‰, with an average of +2.8‰. Platy magnetite samples exhibited δ18O values of +0.6‰ and +2.7‰, with an average of +1.7‰.

6. Discussion

6.1. Origin of the Beizhan Magnetite

The magnetite in the Beizhan deposit contains significantly lower contents of TiO2, Cr2O3, and V2O5 compared to iron deposits formed through magmatic processes, such as Kiruna-type and Chilean-type iron ore deposits. In the Al+Mn vs. Ti+V diagram (Figure 9a,c) [60], the massive magnetite samples predominantly cluster within the skarn magnetite deposit region, revealing constrained contents of Ti, V, Al, and Mn [61]. Conversely, in the case of platy ores, magnetite more closely aligns with IOCG-type and skarn-type magnetite deposit regions. These platy magnetite grains exhibit lower trace element contents, the incorporation of which into the magnetite structure appears to be temperature-dependent. This observation implies that the genesis of this magnetite type may be associated with lower-temperature hydrothermal processes [61].
Magnetite in the brecciated ores exhibit a broad distribution, suggesting a more complex and diverse origin. Similarly, in the Ni/(Cr+Mn) vs. Ti+V diagram (Figure 9b), the measured points of magnetite grains show relatively low Ti+V concentrations and low Ni/(Cr+Mn) values, indicating a skarn type. These characteristics align with hydrothermal genetic features, which are further corroborated in the Ti vs. V diagram (Figure 10a). In the Ti vs. Ni/Cr diagram (Figure 10b), the magnetite data extend across both hydrothermal and magmatic origin fields, implying that the magnetite in the Beizhan deposit carries information related to both hydrothermal and magmatic origins.
The higher concentrations of Ti and Cr observed in brecciated magnetite are indicative of early crystallization compared to the other two types of magnetite, as both Ti and Cr are considered compatible elements within magnetite (Figure 11a). In addition, in magmatic deposits, there is typically a coupling relationship between Ni and Cr, with Ni/Cr ratios mostly being ≤1. These patterns in the element distribution characteristics within the magnetite suggest that the formation of magnetite in the Beizhan deposit is not solely the result of magmatism (Figure 11b). Instead, it is likely that the genesis of magnetite is linked to magmatic–hydrothermal fluid processes.
Furthermore, the content of Sn can serve as an additional petrogenetic indicator, with Sn and Ga concentrations having been proposed for distinguishing between low- and high-temperature hydrothermal and magmatic magnetite [64,67]. The magnetite plots within the hydrothermal regions, specifically across the Ag-Pb-Zn hydrothermal and skarn hydrothermal fields, are shown in the Sn vs. Ga diagram (Figure 11c). This further underscores a hydrothermal source for the magnetite. Taken together, these findings collectively suggest a complex origin for the Beizhan deposit, one that involves the interaction of magmatic and hydrothermal fluids in its formation.
The trace element distribution characteristics, particularly the low Ti content, in magnetite from the Beizhan iron deposit exhibit significant distinctions from typical magnetite deposits formed by magmatic processes, such as Fe-Ti-V deposits and Fe-Ti-P deposits. However, these characteristics bear a resemblance to those of hydrothermal deposits, specifically IOA-type and Porphyry-type deposits (Figure 12). A comparison of the element distribution characteristics in Beizhan deposit magnetite with those found in hydrothermal deposits reveals a consistent trend. Magnetite in the Beizhan iron deposit is notably enriched in immobile elements like Zr, Hf, Zn, Co, Sc, and others, elements commonly associated with hydrothermal fluids. Conversely, the magnetite displays depletion in highly incompatible elements like Si, Ca, and so forth, which are typically linked with magmatic magnetite deposits.
These findings further support the interpretation that the Beizhan deposit has undergone a hydrothermal overprint. The enrichment of immobile elements and the depletion of incompatible elements in the magnetite provide evidence that the formation of the Beizhan iron deposit is closely linked with hydrothermal processes, rather than being solely attributed to a magmatic origin.

6.2. Thermal Evolution of the Mineralization

Application of the Mg-in magnetite thermometer (TMg-mag) reveals a substantial temperature discrepancy among different magnetite types within the Beizhan deposit. Specifically, it indicates that massive and brecciated magnetite crystallized at higher temperatures, with averages of approximately 641 °C and 612 °C, respectively, while platy magnetite exhibits a relatively lower crystallization temperature, averaging around 552 °C (Figure 7a, Table 1). This decreasing temperature trend correlates with trace element concentrations such as Ti, V, and Ga. These elements demonstrate elevated levels in deposits with a predominantly hydrothermal origin, while they exhibit comparatively reduced levels in deposits associated with magmatic or magmatic–hydrothermal sources (Figure 7b). The Al+Mn vs. Ti+V diagram (Figure 9c) further reflects this changing trend in the formation temperature of magnetite, with magnetite plots consistent with the gradual decrease in temperatures from brecciated and massive to platy magnetite.
A combination of magmatic and hydrothermal processes, as revealed by TMg-mag, helps elucidate the thermal evolution of the Beizhan deposit (Figure 13). The earlier brecciated magnetite and the following massive magnetite exsolved in stage 2 and stage 3 (at temperatures around 800 to 600 °C and below 600 °C, respectively) as a result of cooling alongside the Fe-rich magmatic–hydrothermal fluid. The latest platy magnetite precipitated from low-temperature hydrothermal fluids in stage 3 (<600 °C), which mostly occurs with the injection of fluids, leading to complex magnetite growth and pervasive replacement horizons [69].
In summary, the thermal evolution of the Beizhan deposit can be reconstructed by the magnetite thermometry (TMg-mag), which provides a quantitative estimation of cooling trends in variable types of ores. It delineates a transition from magmatic or magmatic–hydrothermal conditions (massive and brecciated ore) to purely hydrothermal conditions (platy ore).

6.3. Source of Ore Components

Previous studies have demonstrated that the iron isotopic system is susceptible to isotopic fractionation during the Earth’s magmatic processes [71,72,73,74]. During the partial melting of the mantle, iron isotopes tend to be incompatible and are concentrated in silicate minerals and magmas [75,76]. Knipping et al. [3] suggested that light Fe isotopes are predominantly enriched in fluid, while heavy Fe isotopes are enriched in magmatism. The marked variation in Fe isotopic compositions of magnetite from the Beizhan deposit indicates substantial fractionation of Fe isotopes during the formation of magnetite ores. The δ56Fe values of massive (−0.078 to +0.005‰) and brecciated (−0.178 to −0.015‰) magnetites closely resemble those of Fe-skarn magnetites found in hydrothermal Fe deposits, such as the Dannemora (−0.43 to +0.01‰) [77], Xinqiao (−0.37 to +0.13‰) [78], and Chagangnuoer deposits (−0.40 to +0.10‰) [12] and the Zankan Fe deposit (−0.30 to +0.50‰) [79]. This suggests a similar lighter magmatic–hydrothermal fluid source for the massive and brecciated magnetite ores.
In contrast, the Fe isotopic composition of platy (+0.177 to +0.200‰) magnetite, which is interpreted as having a low-T hydrothermal crystallization history based on its trace element behavior and magnetite thermometry, significantly deviates from the δ56Fe range of magmatic/high-T origin (Figure 14). Mineral assemblages and paragenetic relationships suggest that sulfides formed after magnetite precipitation. Platy magnetite often occurs together with pyrrhotite, which possesses the lightest Fe isotope composition in Fe skarn deposits [80]. The precipitation of pyrrhotite causes the fluid to become enriched in heavy Fe isotopes, and the subsequently precipitated platy magnetite thus has a heavier Fe isotopic composition. The formation of hydrothermal magnetite in skarn deposits is commonly associated with the dissolution–reprecipitation process [81,82]. During such a process, the primary magnetite may exchange Fe isotopes with the fluid, whose Fe isotopic composition is influenced by the pathways of pyrrhotite formation.
Considerable research has focused on the variability in δ18O values of magnetite from different ore types of iron deposits, indicating the potential for using δ18O values to distinguish deposit types and infer their genesis [17,56,59,85,86]. Magnetite formed through magmatism typically exhibits a relatively narrow range of δ18O values, usually falling between +1‰ and +4‰ [5,59,70,83,87]. Oxygen isotope analyses of magnetite samples extracted from different types of iron ore in the Beizhan iron deposit (massive, brecciated, and platy type) predominantly yield δ18O values ranging from +0.6 to +4.6‰, which are highly consistent with those of magnetites found in the iron oxide deposits in the AIMB (Zhibo, Chagangnuoer, and Songhu iron deposits) [35,36]. Furthermore, these δ18O values closely resemble those observed in the El Laco and Kiruna deposits (Figure 15) [5,7,8,10,70,87].
Magnetite samples with δ18O values ranging between +0.9 and +4.0‰ are typical for magnetite that is in equilibrium with intermediate to felsic magmas or magmatic fluids at high temperatures (~800–1000 °C; i.e., ortho-magmatic magnetite), while values below +0.9% are indicative of hydrothermal fluids at low temperatures [12,87]. Most of the magnetite samples from the Beizhan deposit, except for one massive magnetite with a δ18O less than +0.9‰ and two magnetite samples (brecciated and platy magnetite) with values greater than +4.0‰ that exhibit δ18O values between +0.9‰ and +4.0‰, classifying them as ortho-magmatic magnetite. This suggests that they were in equilibrium with magmas or magmatic fluids at high temperatures. The prevalence of hydrothermal alterations in the Beizhan iron deposit supports the superposition of low-temperature hydrothermal fluids in the late stage, contributing to the modification of the magnetite formed in the early stage.
The δ18O data strongly support the idea of a magmatic–hydrothermal origin with a dominance of hydrothermal processes. This hypothesis is further reinforced by the trace element signature of the magnetite and the extensive evidence of hydrothermal alterations within the Beizhan iron deposit. The prevalence of low-temperature hydrothermal fluids in the late stage appears to have played a significant role in modifying the magnetite formed during the early stages of deposit formation.

7. Conclusions

The in situ LA-ICP-MS magnetite trace element composition in the Beizhan deposit suggests a complex origin involving the interaction of both magmatic and hydrothermal fluids. The trace element distributions, particularly Ti, V, Sn, Ga, Ni, Cr, etc., coupled with the enrichment of immobile elements and depletion of incompatible elements, indicates the involvement of magmatic–hydrothermal processes in the formation of the Beizhan deposit.
Utilizing magnetite thermometry (TMg-mag) to determine crystallization temperatures for the three ore types, our findings reveal a significant temperature difference between the relatively higher-temperature brecciated magnetite (average ~641 and 612 °C, respectively) and the relative lower-temperature platy magnetite (average ~552 °C). This temperature discrepancy indicates a cooling trend and signifies a transition from magmatic or magmatic–hydrothermal conditions (as observed in massive and brecciated ore) to purely hydrothermal conditions in the case of platy ore.
Stable Fe and O isotope values of magnetite from the Beizhan deposit shed light on the source of ore-forming materials. The δ56Fe values for brecciated and massive magnetite fall within the ranges −0.178 to +0.005‰, indicating a magmatic–hydrothermal reservoir. However, the δ56Fe values (+0.177 to +0.200‰) for platy magnetite reveal a magmatic source, contrary to the low-T hydrothermal origin inferred from in situ trace element data. This inconsistency is proposed to be reconciled by considering the magmatic source associated with crystallized pyrrhotite, known for its lightest Fe isotope composition. Furthermore, the δ18O values of magnetite (+0.6 to +4.6‰) in the Beizhan deposit suggest that low-temperature hydrothermal fluids in the late stage may have modified the magnetite formed in the early stage.

Author Contributions

Conceptualization, Y.L. and D.W.; methodology, Y.L. and D.W.; software, Y.L.; validation, D.W.; formal analysis, Y.L. and D.W.; investigation, D.W. and Z.J.; resources, Z.Z. and Z.J.; data curation, D.W. and Y.L.; writing—original draft preparation, Y.L. and D.W.; writing—review and editing, Y.L., D.W. and Z.J.; visualization, Y.L.; supervision, D.W., Z.J., S.D. and Z.Z.; project administration, D.W. and Z.J.; funding acquisition, Z.J. and Z.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (grant 42172104), the National Scientific and Technological Supporting Key Project (2011BAB06B02) and the Project of China Geological Survey (DD20230040).

Data Availability Statement

All data are contained within this article.

Acknowledgments

We kindly thank Li Su for assistance with the LA ICP-MS analyses of magnetite and data reduction, and Zhenyu Chen for assistance with the EPMA analyses. The Third Geological Team of XBGMR is acknowledged for access to data and support with fieldwork. We are very grateful to the editor and reviewers for their thorough and constructive comments, which greatly improved the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Geological map of the Western Tianshan region in NW China showing the Awulale iron metallogenic belt and the major volcanic-hosted iron deposits (simplified from [13,14]). Inset map shows the location of Western Tianshan within the Central Asian Orogenic Belt (modified from [15]). (b) Geological map of the eastern part of the Awulale iron metallogenic belt showing the location of the Beizhan iron deposit (modified from [13]).
Figure 1. (a) Geological map of the Western Tianshan region in NW China showing the Awulale iron metallogenic belt and the major volcanic-hosted iron deposits (simplified from [13,14]). Inset map shows the location of Western Tianshan within the Central Asian Orogenic Belt (modified from [15]). (b) Geological map of the eastern part of the Awulale iron metallogenic belt showing the location of the Beizhan iron deposit (modified from [13]).
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Figure 2. (a) Geological sketch map of the Beizhan iron deposit (modified from [47]). (b) Close-up geological map showing the main magnetite orebodies in the Beizhan iron deposit (modified from [16,48]). (c) Selected cross section of the Beizhan iron deposit (modified from [17,40]).
Figure 2. (a) Geological sketch map of the Beizhan iron deposit (modified from [47]). (b) Close-up geological map showing the main magnetite orebodies in the Beizhan iron deposit (modified from [16,48]). (c) Selected cross section of the Beizhan iron deposit (modified from [17,40]).
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Figure 3. Photographs of the different ore types in the Beizhan iron deposit. (a) Massive magnetite (Mag) ores at the contact between altered host rock and marble. (b) Massive magnetite ore. (c) Massive magnetite ore with fracture infill of garnet (Grt) skarn. (d) Disseminated magnetite in garnet–epidote (Ep) skarn. (e) Disseminated magnetite in calcite (Cal)–epidote veins in proximity to massive ores. (f) Platy magnetite in association with platy pyrrhotite (Po). (g) Contact between host volcanic rock and magnetite ore, where volcanic breccias are cemented by magnetite. (h) Volcanic breccias in the magnetite matrix. (i) Veins of magnetite in the epidote skarn.
Figure 3. Photographs of the different ore types in the Beizhan iron deposit. (a) Massive magnetite (Mag) ores at the contact between altered host rock and marble. (b) Massive magnetite ore. (c) Massive magnetite ore with fracture infill of garnet (Grt) skarn. (d) Disseminated magnetite in garnet–epidote (Ep) skarn. (e) Disseminated magnetite in calcite (Cal)–epidote veins in proximity to massive ores. (f) Platy magnetite in association with platy pyrrhotite (Po). (g) Contact between host volcanic rock and magnetite ore, where volcanic breccias are cemented by magnetite. (h) Volcanic breccias in the magnetite matrix. (i) Veins of magnetite in the epidote skarn.
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Figure 4. Photomicrographs showing magnetite from the Beizhan deposit. (a) Euhedral to subhedral magnetite (Mag) in massive ore. (b) Massive magnetite with interstitial phlogopite (Phl). (c) Fine-grained disseminated magnetite in calcite (Cal) veins. (d) Volcanic breccias cemented by magnetite. (e) Magnetite with interstitial pyrrhotite (Po) and pyrite (Py). (f) Magnetite that is replaced by pyrrhotite and chalcopyrite (Ccp).
Figure 4. Photomicrographs showing magnetite from the Beizhan deposit. (a) Euhedral to subhedral magnetite (Mag) in massive ore. (b) Massive magnetite with interstitial phlogopite (Phl). (c) Fine-grained disseminated magnetite in calcite (Cal) veins. (d) Volcanic breccias cemented by magnetite. (e) Magnetite with interstitial pyrrhotite (Po) and pyrite (Py). (f) Magnetite that is replaced by pyrrhotite and chalcopyrite (Ccp).
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Figure 5. Paragenetic sequence of the Beizhan iron deposit.
Figure 5. Paragenetic sequence of the Beizhan iron deposit.
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Figure 6. Bulk continental crust-normalized multielement plots of magnetite from the Beizhan iron deposit. Bulk continental crust values are from [54]; the order of elements is in accordance with the increasing compatibility with magnetite [55].
Figure 6. Bulk continental crust-normalized multielement plots of magnetite from the Beizhan iron deposit. Bulk continental crust values are from [54]; the order of elements is in accordance with the increasing compatibility with magnetite [55].
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Figure 7. (a) Calculated temperatures and (b) median concentrations of selected trace elements in magnetite from the Beizhan iron deposit. Temperatures were calculated using the TMg-mag thermometer. Uncertainties (error bar) in TMg-mag are at ±50 °C.
Figure 7. (a) Calculated temperatures and (b) median concentrations of selected trace elements in magnetite from the Beizhan iron deposit. Temperatures were calculated using the TMg-mag thermometer. Uncertainties (error bar) in TMg-mag are at ±50 °C.
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Figure 8. Comparison of (a) Fe isotopic and (b) O isotopic compositions for magnetite from the Beizhan deposit with other iron deposits in the AIMB. Also included are δ56Fe values [56] and δ18O values (gray diamonds) [17] for magnetite from the Beizhan deposit. The δ56Fe ranges for the Zhibo and Chagangnuoer iron deposits are from [12,56]. The δ18O ranges for the Dunde, Zhibo, Chagangnuoer, and Songhu iron deposits are from [17,33,35,36,57,58,59].
Figure 8. Comparison of (a) Fe isotopic and (b) O isotopic compositions for magnetite from the Beizhan deposit with other iron deposits in the AIMB. Also included are δ56Fe values [56] and δ18O values (gray diamonds) [17] for magnetite from the Beizhan deposit. The δ56Fe ranges for the Zhibo and Chagangnuoer iron deposits are from [12,56]. The δ18O ranges for the Dunde, Zhibo, Chagangnuoer, and Songhu iron deposits are from [17,33,35,36,57,58,59].
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Figure 9. Discrimination diagram of (a,c) Al + Mn vs. Ti + V and (b) Ni/(Cr + Mn) vs. Ti + V for magnetite from the Beizhan iron deposit (after [60] and modified by [62]). The different fields of temperature are adapted from [63,64].
Figure 9. Discrimination diagram of (a,c) Al + Mn vs. Ti + V and (b) Ni/(Cr + Mn) vs. Ti + V for magnetite from the Beizhan iron deposit (after [60] and modified by [62]). The different fields of temperature are adapted from [63,64].
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Figure 10. Discrimination diagram of (a) Ti vs. V and (b) Ni/Cr vs. Ti for magnetite from the Beizhan iron deposit. Fields of magmatic and hydrothermal magnetite are from [62,65,66].
Figure 10. Discrimination diagram of (a) Ti vs. V and (b) Ni/Cr vs. Ti for magnetite from the Beizhan iron deposit. Fields of magmatic and hydrothermal magnetite are from [62,65,66].
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Figure 11. Binary diagrams of (a) Cr vs. Ti, (b) Ni vs. Cr, (c) Sn vs. Ga for magnetite from the Beizhan iron deposit, the different types magnetite from the typical porphyry (magmatic), porphyry (hydrothermal), skarn, Ag-Pb-Zn (hydrothermal), and BIF-iron ore (hydrothermal–metamorphic) [64,67].
Figure 11. Binary diagrams of (a) Cr vs. Ti, (b) Ni vs. Cr, (c) Sn vs. Ga for magnetite from the Beizhan iron deposit, the different types magnetite from the typical porphyry (magmatic), porphyry (hydrothermal), skarn, Ag-Pb-Zn (hydrothermal), and BIF-iron ore (hydrothermal–metamorphic) [64,67].
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Figure 12. Bulk continental crust-normalized multielement plots of magnetite from the Beizhan iron deposit. Data fields are taken from [68]. Bulk continental crust values are from [54].
Figure 12. Bulk continental crust-normalized multielement plots of magnetite from the Beizhan iron deposit. Data fields are taken from [68]. Bulk continental crust values are from [54].
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Figure 13. Thermal evolution of the Beizhan iron deposit. Reference temperatures of magnetite from various volcanic rocks and deposits, and magmatic to hydrothermal stages are from [70] and [69].
Figure 13. Thermal evolution of the Beizhan iron deposit. Reference temperatures of magnetite from various volcanic rocks and deposits, and magmatic to hydrothermal stages are from [70] and [69].
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Figure 14. δ56Fe vs. δ18O diagram for magnetite from the Beizhan iron deposit (modified from [6]). The orange box denote the isotope ranges of magmatic or high-T origin [68,70,77,83,84].
Figure 14. δ56Fe vs. δ18O diagram for magnetite from the Beizhan iron deposit (modified from [6]). The orange box denote the isotope ranges of magmatic or high-T origin [68,70,77,83,84].
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Figure 15. Comparison of δ18O values for magnetite from the Beizhan iron deposit with other volcanic-hosted iron deposits. Also included are δ18O values (gray diamonds) for magnetite from the Beizhan deposit [17]. Data of Zhibo, Chagangnuoer, and Songhu iron deposits are from [17,33,35,36,38,57]. Data of Chilean iron belt, El Laco, Kiruna, and Grängesberg, are from [7,87]. Range of plutonic material, volcanic material, and low-T hydrothermal magnetite are from [70]. The cutoff line at δ18O = +0.9‰ demarcates magnetite derived from silicate magma or magmatic–hydrothermal fluid [7,8]. The yellow box (+1 to +4‰) is typical δ18O values for ortho-magmatic magnetite [10,68].
Figure 15. Comparison of δ18O values for magnetite from the Beizhan iron deposit with other volcanic-hosted iron deposits. Also included are δ18O values (gray diamonds) for magnetite from the Beizhan deposit [17]. Data of Zhibo, Chagangnuoer, and Songhu iron deposits are from [17,33,35,36,38,57]. Data of Chilean iron belt, El Laco, Kiruna, and Grängesberg, are from [7,87]. Range of plutonic material, volcanic material, and low-T hydrothermal magnetite are from [70]. The cutoff line at δ18O = +0.9‰ demarcates magnetite derived from silicate magma or magmatic–hydrothermal fluid [7,8]. The yellow box (+1 to +4‰) is typical δ18O values for ortho-magmatic magnetite [10,68].
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Table 1. Electron microprobe major element data of magnetite from the Beizhan iron deposit.
Table 1. Electron microprobe major element data of magnetite from the Beizhan iron deposit.
SampleTiO2Al2O3TFeOMnOMgOCaOCoOZnOCr2O3NiOV2O3P2O5TotalTMg-MagType
ZK41-03-0100.1592.880.120.1000.1500.0500.02093.46~529Platy
ZK41-03-020.140.1393.290.080.1100.120.020.0800.01093.99~537Platy
ZK41-04-030.100.1494.040.090.1900.030.310.0200094.91~581Platy
ZK41-04-040.060.1694.190.040.1300.160.020.06000.0394.85~552Platy
ZK41-05-030.020.1993.330.060.1500.080.010.0500.040.0193.93~560Platy
ZK41-05-040.110.1493.4700.0100.1700.04000.0193.95~403Platy
ZK42-01-010.030.1193.510.070.2600.0300.0600.060.0194.14~612Brecciated
ZK42-01-0200.0793.160.120.1900.120.200.0200093.87~582Brecciated
ZK42-01-030.070.2493.670.030.3400.160.14000.01094.67~637Brecciated
ZK42-02-010.401.0490.530.250.7300.020.130.0300.03093.14~723Brecciated
ZK42-02-020.020.2394.370.140.2100.090000095.06~590Brecciated
ZK42-02-030.010.1193.720.010.2100.080.110.0600094.31~592Brecciated
ZK42-02-0400.6293.230.060.3500.020000094.29~641Brecciated
ZK42-04-010.121.0892.660.110.6700.130.180.0100.010.0594.99~710Brecciated
ZK42-04-020.080.8692.670.060.4100.060.060.0400094.23~656Brecciated
ZK42-06-010.040.0894.670.100.0900.190.110.0700.090.0295.45~519Brecciated
ZK42-07-0100.1593.600.040.1500.1500.0200.02094.13~565Brecciated
ZK42-07-0200.0592.970.100.1500.120.08000.05093.51~564Brecciated
ZK42-07-030.020.1193.110.010.2000.1000.0200.06093.63~587Brecciated
ZK42-07-040.070.0793.720.040.1300.1000.0300.02094.17~550Brecciated
ZK42-07-0500.1393.290.050.3800.1100.0300.06094.05~648Brecciated
ZK31-02-0100.8591.900.070.330.090.100.060.0400093.45~636Massive
ZK31-02-0200.9492.370.090.380.120.030.060.030.0200.0394.06~649Massive
ZK31-02-030.031.0090.4000.420.180.1100.0100092.16~663Massive
ZK31-03-010.080.1592.750.060.230.020.140.090.0500.01093.56~600Massive
ZK31-03-020.030.1193.580.060.1600.140.080.0600.03094.23~566Massive
ZK31-04-010.021.2191.030.160.490.220.070.160.05000.0293.41~678Massive
ZK31-04-020.011.0591.630.050.370.170.1100.0200093.42~648Massive
ZK31-05-010.040.0194.750.04000.070.110.05000.0195.08/Massive
ZK31-05-020.030.9391.260.020.310.070.080.060.0300.020.0192.83~631Massive
ZK31-05-030.081.0990.090.080.470.150.200.250.0400.05092.49~673Massive
ZK31-06-010.031.1189.330.020.460.150.050.190.04000.0191.37~672Massive
ZK31-06-020.080.9791.8300.340.080.060.100.04000.0193.50~639Massive
Table 2. LA-ICP-MS trace element data of magnetite from the Beizhan iron deposit.
Table 2. LA-ICP-MS trace element data of magnetite from the Beizhan iron deposit.
SampleScTiVCrCoNiCuZnGaZrNbMoSnHfTaType
ZK41-03-010.64282.467.659.385.602.200.26418.039.701.220.960.206.820.380.07Platy
ZK41-03-020.53176.537.457.717.282.930.30697.6011.050.360.990.258.130.260.09Platy
ZK41-03-030.44336.3910.1410.896.522.850.34941.9013.820.470.830.237.340.370.08Platy
ZK41-04-010.53421.5330.4138.456.822.810.29613.1711.600.430.460.205.430.240.10Platy
ZK41-04-020.47466.0229.536.815.862.350.24136.2110.380.180.310.262.800.200.07Platy
ZK41-04-030.33442.8925.7419.5073.7135.00517.0226.698.920.110.140.212.120.180.06Platy
ZK41-05-010.39473.0412.403.3010.792.100.29882.6410.870.530.500.267.130.350.11Platy
ZK41-05-020.50662.3034.764.564.171.750.3749.589.810.340.740.243.910.310.10Platy
ZK41-05-030.46730.1741.724.144.351.401.21616.7210.070.380.720.285.650.350.11Platy
ZK41-06-010.51571.1220.533.249.972.130.37128.2710.230.310.480.225.280.250.07Platy
ZK41-06-020.29428.3211.614.745.302.110.30922.9610.200.570.480.247.640.230.07Platy
ZK41-06-030.48555.7913.2413.546.892.131.45152.0317.230.501.000.275.690.320.10Platy
ZK42-02-010.341146.4772.5219.776.132.040.75635.5416.081.350.120.5312.010.540.11Brecciated
ZK42-02-020.381736.2796.887.266.591.349.91502.3515.210.900.120.357.150.460.18Brecciated
ZK42-02-030.371018.2765.965.497.231.390.641133.6316.241.370.340.3510.800.480.17Brecciated
ZK42-02-040.403603.95101.8947.0910.751.490.672262.2719.761.120.760.5613.750.430.13Brecciated
ZK42-02-050.393189.08118.267.677.541.930.54277.5413.230.840.580.298.170.510.13Brecciated
ZK42-04-010.442983.2787.77184.77134.201.684.95634.5813.390.860.450.269.190.270.10Brecciated
ZK42-04-020.271786.3980.9415.5218.701.611.99593.4013.500.560.410.229.310.380.09Brecciated
ZK42-04-030.482044.4679.236.3236.131.620.58501.8313.390.540.250.256.970.360.09Brecciated
ZK42-07-010.331210.0685.4619.069.091.959.59202.7011.930.470.220.317.510.360.11Brecciated
ZK42-07-020.442053.2692.6713.088.021.500.48784.5312.840.410.210.349.000.570.10Brecciated
ZK42-07-030.571217.7593.5922.266.551.304.93107.0212.360.970.410.3311.210.500.14Brecciated
ZK42-07-040.431744.0378.7727.959.711.590.541068.6314.670.760.280.5310.680.480.19Brecciated
ZK42-08-010.281284.9473.943.676.861.3227.21904.3713.370.990.530.289.800.320.08Brecciated
ZK42-08-020.433415.5190.623.259.702.6098.65643.3913.274.034.150.2620.100.390.30Brecciated
ZK42-08-030.342035.4593.643.347.821.890.381013.8313.440.580.300.279.640.300.08Brecciated
ZK42-08-040.291377.2678.735.539.181.9229.14925.3513.230.630.280.2810.020.350.10Brecciated
ZK31-02-010.51458.749.843.393.143.590.39287.807.164.691.480.1710.610.380.07Massive
ZK31-02-020.41389.335.772.785.073.420.24836.377.675.291.420.1812.140.240.07Massive
ZK31-02-030.50366.195.523.274.804.120.27829.077.404.671.470.2112.220.330.06Massive
ZK31-02-040.41334.477.113.723.764.040.44403.969.294.692.090.3016.030.300.09Massive
ZK31-03-011.19592.4422.445.421.840.650.2326.544.836.996.780.1613.790.240.09Massive
ZK31-03-020.80528.5120.1638.632.700.790.6949.776.537.136.560.1516.320.160.17Massive
ZK31-03-030.26316.1424.045.793.020.770.2925.734.230.990.920.244.750.260.09Massive
ZK31-03-040.76811.6648.7310.254.171.791.0646.3810.174.902.370.4912.120.560.17Massive
ZK31-04-010.64271.969.263.032.894.090.37193.319.526.683.140.2121.330.270.09Massive
ZK31-04-020.32183.617.273.763.674.070.35649.999.141.921.410.2414.370.270.10Massive
ZK31-04-032.33848.0126.1112.0410.4410.731.10990.7432.2614.377.710.7161.430.990.28Massive
ZK31-04-040.37136.426.792.574.463.170.28244.208.373.951.610.1615.320.280.07Massive
ZK31-05-010.38968.2148.695.1311.803.730.9470.6413.301.350.110.357.010.400.09Massive
ZK31-05-020.21584.1927.251.816.201.600.27184.037.270.300.380.115.590.110.05Massive
ZK31-05-030.18465.3121.583.025.431.710.4950.427.201.160.140.142.700.160.06Massive
ZK31-05-040.31501.0942.543.783.991.360.2567.356.413.030.520.194.750.180.06Massive
ZK31-05-050.25516.8025.825.632.141.550.9381.816.814.000.260.184.460.190.06Massive
ZK31-06-010.31348.2913.234.772.622.830.19285.455.522.090.580.127.670.220.04Massive
ZK31-06-021.27566.7724.7410.7910.4210.150.82212.5225.4514.485.170.5743.150.840.22Massive
ZK31-06-030.2181.936.332.583.693.590.22294.737.742.071.200.1512.270.230.08Massive
ZK31-06-040.2885.206.162.913.943.110.29603.867.334.051.670.2515.060.220.06Massive
Table 3. Iron and oxygen isotope compositions of magnetite from the Beizhan iron deposit.
Table 3. Iron and oxygen isotope compositions of magnetite from the Beizhan iron deposit.
Sampleδ56FeIRRM-014 (‰)δ57FeIRRM-014 (‰)δ18OV-SMOW‰Ore TypeData Source
ZK34−0.015−0.0011.2Brecciated magnetiteThis study
ZK-35−0.178−0.2602.3Brecciated magnetiteThis study
ZK-28−0.025−0.0774.5Brecciated magnetiteThis study
ZK-33−0.074−0.1002.4Massive magnetiteThis study
ZK-310.005−0.0262.5Massive magnetiteThis study
ZK-40−0.078−0.1224.6Massive magnetiteThis study
14WBZ-14−0.047−0.1601.5Massive magnetiteThis study
ZK-390.2000.2830.6Platy magnetiteThis study
ZK-410.1770.2892.7Platy magnetiteThis study
bei10−0.065−0.096-Vein magnetiteWang [56]
bei14−0.120−0.177-Vein magnetiteWang [56]
bei15−0.121−0.178-Vein magnetiteWang [56]
bei190.0180.027-Massive magnetiteWang [56]
bei20−0.061−0.090-Massive magnetiteWang [56]
11BZ-32−0.181−0.267-Vein magnetiteWang [56]
ZK702-278.5--5.2-Yang et al. [17]
BZ-001--5.0-Yang et al. [17]
BZ-8t-1--4.9-Yang et al. [17]
BZ-1t-1--5.3-Yang et al. [17]
ZK005-655.2--2.4-Yang et al. [17]
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Li, Y.; Jiang, Z.; Wang, D.; Zhang, Z.; Duan, S. Genesis of the Beizhan Iron Deposit in Western Tianshan, China: Insights from Trace Element and Fe-O Isotope Compositions of Magnetite. Minerals 2024, 14, 304. https://doi.org/10.3390/min14030304

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Li Y, Jiang Z, Wang D, Zhang Z, Duan S. Genesis of the Beizhan Iron Deposit in Western Tianshan, China: Insights from Trace Element and Fe-O Isotope Compositions of Magnetite. Minerals. 2024; 14(3):304. https://doi.org/10.3390/min14030304

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Li, Yan, Zongsheng Jiang, Dachuan Wang, Zuoheng Zhang, and Shigang Duan. 2024. "Genesis of the Beizhan Iron Deposit in Western Tianshan, China: Insights from Trace Element and Fe-O Isotope Compositions of Magnetite" Minerals 14, no. 3: 304. https://doi.org/10.3390/min14030304

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