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Article

Discussion on the Geochemical Characteristics and Enrichment Process of Li-Rich Layers in Xian’an Coalfield, Guangxi Province, China

by
Li Zhang
1,2,3,
Degao Zhang
2,3,4,
Fuqiang Zhang
5,
Zhongyue Lin
4,
Jie Sun
2,3,
Xiaoyun Yan
2,3,*,
Huiheng Xu
5,
Shaobo Di
2,3,
Shaoqing Huang
2,3,
Xiaotao Xu
2,3 and
Zhuo Zou
2,3
1
College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), D11 Xueyuan Road, Beijing 100083, China
2
General Prospecting Institute of China National Administration of Coal Geology, Beijing 100039, China
3
Key Laboratory of Transparent Mine Geology and Digital Twin Technology, National Mine Safety Administration, Beijing 100039, China
4
China National Administration of Coal Geology, Beijing 100036, China
5
Guangxi Bureau of Coal Geology, General Administration of Coal Geology, Guilin 530299, China
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(4), 404; https://doi.org/10.3390/min15040404
Submission received: 11 March 2025 / Revised: 7 April 2025 / Accepted: 10 April 2025 / Published: 11 April 2025
(This article belongs to the Special Issue Mineralization Mechanism and Geochemical Characteristics of Coals and Associated Minerals)
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Versions Notes

Abstract

:
As a rare metal, lithium plays a pivotal role in strategic critical metal mineral resources and is one of the critical metals for developing the contemporary social economy. The Li-rich layers in the Xian’an coalfield in Guangxi Province were taken as a typical study area in this research, the material sources of Li-rich strata were discussed, and the enrichment process of Li-rich layers was revealed through geochemical research methods. The coal seams in this area have abnormal enrichment points with high lithium content, but there is a certain inhomogeneity in the plane and longitudinal distribution. This research studies the causes and material sources around the multi-layer lithium-extruded layers in the longitudinal distribution of coal-based strata. Through mineralogy and geochemical research methods, this research shows that Li-rich mineralization results from the combined action of terrigenous material and volcaniclastic source inputs, water–rock processes, and fluid inputs. The Li-bearing rocks formed over three periods, which are the weathering, sedimentation, and diagenesis stages. Based on factors such as provenance and geological processes, this study analyzes the genesis of Li-rich layers and provides a theoretical basis for the future prospecting of lithium ore deposits.

1. Introduction

Coal-bearing strata can enrich critical metals (lithium, gallium, rare earth elements, etc.) to form coal-based critical metal deposits under specific geological and geochemical conditions [1,2,3]. As an important strategic metal resource, lithium plays a vital role in the field of new energy technology. At present, the lithium deposits developed and utilized in the industry mainly include brine and granitic pegmatite lithium deposits, and lithium in coal measures has great potential for independent mineralization or comprehensive utilization of associated resources. It has been shown that lithium in coal is mainly found in clay minerals (e.g., chlorite, kaolinite) [4,5,6,7]; independent minerals of lithium, such as tourmaline [8] and cookeite [4]; and bauxite minerals such as boehmite [7,9]. Finkelman suggested that 80% of lithium in high-rank coal and 60% of lithium in low-rank coal are related to aluminosilicates [10]. Dai (2021) suggested that the occurrence of lithium in coal mainly consists of silicate (mainly clay minerals, followed by mica and tourmaline), phosphate, and organic states [9].
Lithium is a new energy material and strategic resource, and according to the type of deposit, global lithium resources are generally divided into three categories: pegmatites, brines, and clays (or unusual lithium deposits) [11]. Among them, clay-type lithium deposits were discovered relatively late, and their formation is mostly closely related to volcanic activity. At present, the main clay-type lithium deposits discovered are the Kings Valley lithium mine in the McDermitt crater in Nevada, USA [12], the montmorillonite lithium mine in Egypt [13], the Sonora lithium mine in Mexico, and the Jadar lithium mine in Serbia.
Global lithium resources are mainly distributed in Argentina, the United States, Bolivia, Chile, Canada, China, Germany, Australia, and the Democratic Republic of the Congo (DRC). According to the U.S. Geological Survey, the global lithium resources were 115 million tonnes (metal volume) in 2024, including 23 million tonnes in Bolivia, 23 million tonnes in Argentina, 11 million tonnes in Chile, 8.7 million tonnes in Australia, and 6.8 million tonnes in China, with these five countries accounting for 68% of the world’s total (U.S Geological Survey, 2024). At present, the degree of development and utilization of sedimentary lithium deposits is low; except for the Jadar deposit in Serbia and the McDermitt lithium mine in the United States (2.0 mt, Li2O grade 0.29%), the vast majority of the deposits are limited by the impact of lower grades and have not been mined on a large scale.
The occurrence states of lithium are complex in coal, and lithium could be enriched in fly ash after coal is burned and utilized [14]. Meanwhile, some scholars are exploring the migration and distribution laws of lithium and rare earth elements during coal washing and selection [15]. Through some low-cost conventional separation methods (particle size classification, gravity separation, magnetic separation, flotation, etc.), lithium and rare earth elements in coal can be enriched in a specific product [16].
The Late Permian is an important coal-forming period in Guangxi, and the coalfields are located on the carbonate platform. In addition, most of the coal contains high sulfur content, and some of the coal is classified as ultra-high organic sulfur coal [17]. Related research has shown that these coals are highly enriched in some critical metal elements, such as rare earth elements and yttrium (REY), U, Mo, Se, and V, and the sources and enrichment processes have been studied. For example, Shao et al. (2003) studied the petrology and geochemistry of high-sulfur coal in the Suhe Coal Mine and the Lilan Coal Mine and found that these coals were rich in most trace elements, especially Mo, U, and W, and proposed that the marine transgression affected the enrichment of these elements during the peat accumulation stage [17]. Zeng et al. (2005) concluded that the enrichment of V, Cr, Zn, Mo, Ni, Rb, and sulfur was controlled by the paleosoil layer under peat, while the leaching of overlying carbonates also led to local enrichment of some elements (e.g., Cl, F, Sr, and Ca) [1,18,19,20,21]. Based on the study of mineralogy and geochemical characteristics in Fusui, Heshan, and Yishan coalfields, it is concluded that the enrichment of trace elements such as F, V, Se, Mo, and U is controlled by sediment source areas and multi-phase hydrothermal fluids, and the influence of seawater is not the main controlling factor. Zhang et al. (2021) concluded that the high concentration of rare earth elements in the Xian’an coalfield in Guangxi Province is controlled by the input of volcanic ash and the influence of water–rock interaction [22].
Although previous works have studied the mineralogy and geochemical characteristics of Late Permian coal in Guangxi, there are different views on whether the detrital material in the coal is terrigenous detrital or volcaniclastic rock. The Late Permian coal-bearing basin in Guangxi was developed on isolated and confined carbonate plateaus. It was previously believed that the Yunkai Paleocontinent was an important clastic source area in the Late Permian coal-bearing basin in Guangxi. Still, it is unclear how the terrigenous detritus crossed the interplatform trough and entered the higher carbonate plateau. In addition, during the formation of the Late Permian coal-bearing basin in Guangxi, southern China was experiencing complex tectonic–magmatic–volcanic activities. The volcanic activities caused by the mantle plume of Emeishan and the volcanic activity of the Yuebei island arc were frequent, which provided an important material basis for the formation of the Upper Permian bauxite in western Guangxi, and whether they provided volcanic materials for the formation of the Upper Permian coal measures in central and southwestern Guangxi still needs to be studied.

2. Geological Setting and Sampling

The coal-bearing strata in the study area are the Upper Permian Heshan Formation (Figure 1). The Heshan Formation is in parallel unconformity contact with the Lower Middle Permian Maokou Formation and is in integrated contact with the overlying Dalong Formation. The lithology of the coal-bearing rocks of the Heshan Formation is dominated by carbonate rocks, interbedded with carbonaceous mudstone, mudstone, marl, and coal seams, and locally interbedded with siltstone (Figure 2). The samples were taken from the lithium-enriched strata at the upper part of the Maokou Formation, which helped to reveal the longitudinal distribution of lithium, including the limestone of the top and bottom plates of the K5 coal seam.
According to the lithologic composition and sedimentary characteristics, the coal-bearing rocks of the Heshan Formation can be divided into two sections: the lower section is the K5 coal seam, and the upper section is the K4, K3, K2, and K1 coal seams. Based on the different coal-bearing and lithological assemblages, and fossils and their assemblages, the Heshan Formation was divided into the upper section (P3h2) and the lower section (P3h1) by the K4 coal seam floor. The lower section of the Heshan Formation is in parallel unconformity contact with the Maokou Formation, and is usually composed of iron aluminum rock, clay, coal, and carbonaceous mudstone from bottom to top (Figure 2), and the mineralized layer is developed between the Maokou and Heshan Formation. The ferro-aluminite section is missing in some locations, which is related to the paleokarst topography of the Maokou Formation. It usually develops in the low-lying karst areas and is lacking in the uplift area. Claystone is generally developed, grayish-white in the outcrop profile, contains a large number of automorphic crystalline pyrite particles or nodules, and the diameter can reach several centimeters.
The coal-bearing strata are the Permian Upper Heshan Formation (P3h), and the coal seams are mainly concentrated in the middle and lower part of the Heshan Formation. The lithology is gray to dark gray limestone, chert limestone, and gray-white to light gray dolomitic limestone. The thickness of the formation is 95–265 m; the average is 165 m. The coal seam (K5) has a minimum thickness of 0.30 m, a maximum thickness of 6.24 m, and an average of 2.41 m.

3. Analytical Methods

The sample was collected from one drill core of the study area in the Xian’an coalfield; the sampling location is shown in Figure 1 and Figure 2. Samples QK-01 and QK-06 are the limestone samples from Heshan Formation and Maokou Formation. Samples QK-02, QK-03, QK-04, and QK-05 are the mineralized samples (Figure 2). The XRD analysis was carried out using a conventional XRD system (Rigaku Miniflex II, Cu-Ka radiation) with 0.02° step and a scanning time of 1 s/step, within 2–70° of 2θ range, and the mineral fraction was quantitatively calculated by the self-cleaning method. In this method, the main diffraction peaks (d value and intensity) were comprehensively compared with the standard card using JADE 6.5 software, and the main mineral phase composition was determined according to the matching degree (optimal), using the formula “ωA = (IA/RA)/(IA/RA + IB/RB + IC/RC + ...... × 100%” for semi-quantitative calculation, where ωA is the mass fraction of the mineral phase to be measured. IA and RA were the strongest peaks and RIR values of phase A of the mineral to be measured, respectively. IB and RB were the strongest peaks and RIR values of the mineral phase B to be measured, respectively. IC and RC were the strongest peaks and RIR values of phase C of the mineral to be measured, respectively. The main element determination was determined by fused disc X-ray fluorescence spectrometry (XRF), and the instrument used was Shimadzu XRF-1800 (Rigaku, Tokyo, Japan), with a test accuracy of better than 5%. The trace element content of the whole rock was analyzed by the dissolution method and the Thermo Element XR-ICP MS (Agilent 7700e, Agilent, Santa Clara, CA, USA), and the international standards OU-6, AMH-1, and GBPG-1 were used for analysis and quality monitoring, with an analysis error of less than 10%; the detailed analysis method is shown in Liang et al., 2000 [23].

4. Results

4.1. X-Ray Diffraction Analysis

The results of the X-ray diffraction analysis showed that the main constituent minerals of mineralized layers (QK-02, QK-03, QK-04, and QK-05) were kaolinite, illite, chlorite, quartz, gypsum, anatase, and pyrite (Table 1). The limestone (QK-01 and QK-06) is mainly composed of calcite and quartz. According to XRD analysis, the cookeite in this mineralized layer has a good diffraction peak (Figure 3). The samples are mainly composed of clays, such as QK-03, QK-04, and QK-05, which show higher contents of kaolinite, chlorite, and corrensite. In sample QK-02, it has a lower content of clay minerals, and the main clay mineral is illite (Table 1). From the XRD results, it can be seen that the occurrence of lithium is closely related to the clay mineral content. QK-03, QK-04, and QK-05 were found to contain higher lithium and higher clay content. Among them, QK-03 has the highest lithium content, and the corresponding clay mineral content is also the highest, while QK-03 has the highest content of kaolinite and chlorite, indicating that the enrichment of lithium is closely related to the clay minerals.
The types and assemblages of minerals in coal are comprehensively controlled by a variety of geological factors, such as source rock properties, volcanic activity, weathering and transport conditions, sedimentary conditions, diagenesis, and hydrothermal activity [24,25]. The same coal seam often exhibits similar mineral assemblage styles [26], revealing similar geological control factors.

4.2. Geochemistry

4.2.1. Major Elements

The top overlying Heshan Formation limestone (QK-01) has a SiO2 content of 13.43% (in wt.%), Al2O3 content of 0.23%, MgO content of 0.76%, Na2O content of 0.08%, K2O content of 0.05%, TiO2 content of 0.02%, and CaO content of 53.13%. Mineralized layer samples (QK-02, QK-03, QK-04, and QK-05) have a SiO2 content of 40.55%–46.55%, with an average of 44.19%; Al2O3 content of 28.68%–39.44%, with an average of 35.56%; MgO content of 0.27%–0.71%, with an average of 0.46%; Na2O content of 0.29%–1.44%, with an average of 0.88%; K2O content of 0.51%–4.02%, with an average of 1.87%; TiO2 content of 1.04%–1.66%, with an average of 1.37%; and CaO content of 0.32%–0.40%, with an average of 0.35%. The limestone (QK-06) of the lower Maokou Formation at the bottom contained a SiO2 content of 18.41%, Al2O3 content of 4.86%, MgO content of 0.58%, Na2O content of 0.39%, K2O content of 0.4%, TiO2 content of 20.18%, and CaO content of 40.82%. Except for the overlying and underlying limestone, the average chemical weathering index of the mineralized samples is CIA = 91.72 (Table 2), which is the product of strong chemical weathering, indicating that the cookeite in the clays should be transformed from other minerals during diagenesis rather than self-generation [27].

4.2.2. Trace Elements

The lithium content in the mineralized layer ranged from 185.38 to 1319.83 μg/g with an average of 878.87 μg/g (Table 3). The corresponding samples of the limestone layer, weathered crust, claystone layer, and carbonaceous mudstone layer were collected from bottom to top. According to the results of major and trace element analysis (Table 2 and Table 3), the lithium content gradually increased from bottom to top, and the enrichment of lithium in the K5 layer reached 1319.83 ppm (QK-03). The QK-03 sample had the highest Li content, corresponding to the highest content of Al2O3 and Gd, and highest CIA value. The QK-02 mineralized sample had the lowest Li content, corresponding to the highest contents of SiO2, MgO, Na2O, K2O, Fe2O3, Mn, Rb, Sr, Sn, Cs, Ba, W, Tl, Pb, and Th. In the study of the enrichment of trace elements in the Li-rich layer, the upper crust is used as the reference value to reveal the enrichment degree of the elements. The degree of element enrichment is expressed in terms of concentration coefficients (sample/upper crust), where CC < 0.5, 0.5–2, 2.0–5.0, 5.0–10, 10–100, and >100 indicate depletion, similarity, slight enrichment, enrichment, and significant enrichment, respectively [28]. The average values of QK-02, QK-03, QK-04, and QK-05 were compared with the abundance of trace elements in the upper crust (Figure 4), in which Li (43.94) and Cr (10.63) were significantly enriched; Mo (9.46) and U (7.55) were enriched; and Ti (2.55), V (4.15), Ni (2.37), Zr (3.08), Nb (2.16), Hf (2.96), W (2.15), Pb (2.13), and Th (2.63) were slightly enriched. The contents of Be (1.21), Sc (1.43), Co (0.63), Cu (0.79), Ga (1.63), Y (1.34), Sn (1.42), Cs (3.87), La (1.24), Ce (1.58), Pr (1.33), Nd (1.36), Sm (1.53), Eu (1.09), Gd (1.54), Tb (1.69), Dy (1.81), Ho (1.64), Er (1.60), Tm (1.83), Yb (1.82), Lu (1.79), Ta (1.64), and Tl (1.65) were similar to those of the upper crust, while the contents of Mn (0.03), Zn (0.49), Rb (0.47), Sr (0.27), and Ba (0.28) showed depletion. The concentration of Li ranges from 185.38 to 1319.83, with an average value of 878.87; Cr ranges from around 36.29 to 498.68, with an average value of 372.16; Mo ranges from around 3.78 to 23.40, with an average value of 14.19; and U ranges from around 11.52 to 28.16, with an average value of 21.14. Except for Gd, the values of Cr, Mo, and U also have a certain correlation with lithium enrichment.

5. Discussion

The material sources of the Upper Permian Li-rich layers in Guangxi have long been controversial, and include the following theories: (1) the clastic source is the Maokou Formation limestone [26]; (2) the detrital material is derived from the eruptive volcanic rocks of the Emeishan mantle [19,29]; (3) the detrital material originated from a volcanic arc formed by the splicing of the North Vietnamese Massif and the South China Plate [5,30]; and (4) the detrital material originated from the Yunkai Paleocontinent [4,31]. Based on the previous research, the material sources in the study area were discussed according to the geochemical parameters.

5.1. Material Sources

Many inactive elements such as Al, Ti, Zr, Nb, Hf, Ta, Th, Sc, and rare earth elements have been widely used in the prediction of source rocks. Because these elements have low oxide and hydroxide solubility, and they hardly change with weathering, transport, and deposition. Therefore, they are almost recorded in sedimentary strata [32,33]. In the diagenetic process of sedimentary rocks, the ratios of inactive elements have no obvious changes, and the chemical composition and ratios of inherited parent rocks are still stable and unchanged under geological processes, so they are reliable geochemical parameters for source tracing. The Zr and Hf (Figure 5) and Nb and Ta (Figure 6) of Li-rich samples and the limestone of the Maokou Formation showed a very significant positive correlation (R2 = 0.99, R2 = 0.99), indicating that the source of the detrital material in the study samples is related to the limestone of the underlying the Maokou Formation, which provides part of the source of the study area.
Both the Li-rich samples and the underlying limestone sample show light rare earth enrichment (LaN/LuN > 1), and the negative anomaly of Eu is presented. Mineralized layer samples show positive anomalies of Ce while underlying limestone shows negative Ce-anomalies (Figure 7). Mafic and ultramafic rocks usually have weak or no negative Eu anomalies, while acidic rocks have strong negative Eu anomalies, and these features can be preserved in sedimentary rocks, so they can be used for provenance tracing of sedimentary rocks. The biggest difference in the composition of REE in the upper and lower middle and middle layers of the mineralized layer is that the upper part shows a mild positive anomaly of Eu and a clear negative anomaly of Eu in the lower part, revealing significantly different material sources or modification effects of hydrothermal fluids [34].
The probable sources of clastic material are analyzed by the Al2O3/TiO2 vs. Nb/Yb diagram, instead of Nb/Y [36]. As shown in Figure 8, the Al2O3/TiO2 vs. Nb/Yb diagram indicates the Emeishan alkaline rocks of the probable provenances.
Recent studies have indicated the material sources based on the zircon U-Pb dating methods, as well as whole-rock mineralogy and geochemical parameters [46]. The results show that the clastic sources of the Upper Permian coal-bearing rocks are mainly derived from the remnants above the Daxin Paleocontinent. The residue includes the limestone of the Maokou Formation, the volcanic ash of Emeishan, and the magmatic arc volcanic ash of the Yuebei massif. In addition, the Yunkai Paleocontinent provides a small number of detrital sources.

5.2. Lithium Enrichment Process

At present, the degree of development and utilization of sedimentary lithium ore deposits is limited by the influence of their low grade, and they have not yet been mined on a large scale, but due to the large total amount of sedimentary lithium ore resources and high potential economic value, they have gradually attracted extensive attention from scholars and industry. The exploration of sedimentary lithium deposits has made breakthroughs globally but is mainly concentrated on the west coast of North America. In terms of quantity, pegmatite-type lithium deposits are the dominant type and are mainly concentrated in Africa and Western Australia [47].
The enrichment of lithium is controlled by the supply of volcanic and terrigenous clastic materials, hydrothermal fluid inputs, and water/lithogenesis in the syngeneic–diagenetic stages. During the Middle to the Late Permian, under the influence of the Tungwu movement, the carbonate platform was uplifted, weathered, and denuded in the study area, and a set of remnants accumulated on the Daxin Paleocontinent. The CIA index can identify the degree of chemical weathering in the source area, and reflect the degree of weathering of aluminosilicate minerals to clay minerals [48,49]. Weathering is an important factor in metamorphism and magmatic activity, which causes changes in minerals and chemical elements and affects material cycling and geochemical processes. As can be seen from the Chemical Index of Alteration (CIA), these residues have undergone strong chemical alteration (CIA values range from 83 to 97) (Figure 9), during which active elements (Na, K, Ca, etc.) are highly leachable, and inactive elements (Al, Ti, Ga, REY, Zr, Li, etc.) remain in the residues. There was a good positive correlation between Li and CIA (Figure 9) in the study samples, indicating that chemical weathering leaching contributed to the enrichment of inactive elements. The leaching of alkali metals during the weathering process is accompanied by the formation of clay minerals, which have a strong adsorption effect on lithium, and adsorb them to be enriched into minerals such as cookeite. The source of lithium in lithium-rich coal is controlled by the material properties of the erosion source area and the geological tectonic evolution of the sedimentary basin, and the input of felsic detrital materials in the erosion source area and the hydrothermal activity are the main controlling factors for the enrichment of lithium in coal [50,51,52]. The positive correlation between lithium and cookeite in some coal indicates that cookeite is also an important carrier of lithium in coal.
The clastic materials of the coal-bearing rocks in the study area are mainly derived from terrigenous clastic materials and volcaniclastic materials induced by the mantle plume of Emeishan. The terrigenous clastic material came from the bauxite and clayey residues; its parent material is partly from the limestone of the Maokou Formation, and partly from the volcaniclastic material of Emeishan that erupted during the Middle to the Late Permian, which has suffered long-term weathering and leaching, and then accumulated a set of residues on the top of the Maokou Formation, which provides important terrigenous clastic materials for the formation of the Late Permian coal-bearing rock series. The volcaniclastic material consists of alkaline volcanic ash provided by the Late Permian Emei mantle plume, which was transported through the atmosphere to the coal-bearing basin and provides important volcaniclastic material for the enrichment of elements such as lithium and rare earth elements.

6. Conclusions

Mineralogical and geochemical studies on the Xian’an coalfield in Guangxi Province showed that the clastic materials of the coal-bearing rocks in the study area mainly came from the volcanic debris near the source area. The chemical weathering index CIA = 91.65 of the lithium-bearing ore layer in the Heshan Formation is the product of strong chemical weathering. The formation of the Permian lithium-bearing rocks in Guangxi has gone through three stages, weathering–sedimentation–diagenesis, with the volcaniclastic material weathering in the continental environment, the later crust descending, the seawater inundating the platform and depositing carbonate rocks, and the lithium-bearing rocks entering the compaction and diagenesis stages.

Author Contributions

Conceptualization, L.Z., D.Z. and X.Y.; methodology, S.H. and X.X.; software, S.D.; investigation, F.Z.; resources, J.S.; project administration, Z.L.; data curation, H.X.; writing-original draft preparation, L.Z.; writing-review and editing, X.Y.; visualization, Z.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by The National Key R&D Program of China (2021YFC2902005, 2023YFC2906404), the National Natural Science Foundation of China (No.42472242, 42272207), and the China Coal Geological Administration Carbon Neutral Special Project (ZMKJ-2023-JBGS03-01).

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors would like to give their sincere thanks to the Guangxi Bureau of Coal Geology for assistance during sampling. We are grateful to editors and anonymous reviewers for the valuable and constructive comments on the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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Minerals 15 00404 g001
Figure 1. (A) A map of China. (B) Location and geological maps of Xian’an coalfield, Guanxi Province.
Figure 1. (A) A map of China. (B) Location and geological maps of Xian’an coalfield, Guanxi Province.
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Minerals 15 00404 g002
Figure 2. The stratigraphic column and the outcrop section of Xian’an coalfield, Guangxi Province.
Figure 2. The stratigraphic column and the outcrop section of Xian’an coalfield, Guangxi Province.
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Figure 3. XRD patterns of representative samples.
Figure 3. XRD patterns of representative samples.
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Figure 4. Concentration coefficients of trace elements of mineralized samples.
Figure 4. Concentration coefficients of trace elements of mineralized samples.
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Figure 5. Plot of Zr-Hf of the Li-rich samples and underlying limestone sample.
Figure 5. Plot of Zr-Hf of the Li-rich samples and underlying limestone sample.
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Figure 6. Plot of Nb-Ta of the Li-rich samples and underlying limestone sample.
Figure 6. Plot of Nb-Ta of the Li-rich samples and underlying limestone sample.
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Figure 7. The chondrite-normalized REE patterns of the Li-rich samples and underlying limestone sample. Chondrite normalization values from Taylor and McLennan (1985) [35].
Figure 7. The chondrite-normalized REE patterns of the Li-rich samples and underlying limestone sample. Chondrite normalization values from Taylor and McLennan (1985) [35].
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Minerals 15 00404 g008
Figure 8. Comparison of the studied and probable source rocks using Al2O3/TiO2-Nb/Yb diagrams. Modified from Zheng et al., 2020 [36]. The plots of the probable source rocks are based on the data from Anh et al. (2011) [37], Gong et al. (2018) [38], He et al. (2007, 2014) [39,40], He et al. (2010) [41], Liao et al. (2016) [42], Shellnutt and Zhou (2007) [43], Shellnutt and Iizuka (2012) [44], and Wang et al. (2015) [45]; LIP, Large Igneous Province; TTG, tonalite–trondhjemite–granodiorite. The red spots are represent the Li-riched samples (QK-02, 03, 04 and 05).
Figure 8. Comparison of the studied and probable source rocks using Al2O3/TiO2-Nb/Yb diagrams. Modified from Zheng et al., 2020 [36]. The plots of the probable source rocks are based on the data from Anh et al. (2011) [37], Gong et al. (2018) [38], He et al. (2007, 2014) [39,40], He et al. (2010) [41], Liao et al. (2016) [42], Shellnutt and Zhou (2007) [43], Shellnutt and Iizuka (2012) [44], and Wang et al. (2015) [45]; LIP, Large Igneous Province; TTG, tonalite–trondhjemite–granodiorite. The red spots are represent the Li-riched samples (QK-02, 03, 04 and 05).
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Figure 9. Plot of Li-CIA of the Li-rich samples and underlying limestone sample.
Figure 9. Plot of Li-CIA of the Li-rich samples and underlying limestone sample.
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Table 1. Whole rock mineral content and relative content of clay minerals.
Table 1. Whole rock mineral content and relative content of clay minerals.
SampleWhole Rock Mineral ContentRelative Content of Clay Minerals
GypsumAnataseQuartzCalcitePyriteClaysIlliteKaoliniteChloriteCorrensite
QK-06--3.396.7------
QK-020.50.910.6-5.881.3420--
QK-030.60.40.5-2.396.32.963.410.88.6
QK-041.70.90.8-1.195.518.941.59.38.1
QK-051.51.74.8-0.691.515.544.910.05.8
QK-01-0.110.880.0-9.0395--
Table 2. Major element contents of mineralized samples and limestone samples (wt.%) in Xian’an coalfield, Guangxi.
Table 2. Major element contents of mineralized samples and limestone samples (wt.%) in Xian’an coalfield, Guangxi.
SampleSiO2Al2O3MgONa2OK2OP2O5TiO2CaOTFe2O3MnOLOICIA
QK-063.430.230.760.080.050.010.0253.130.120.0141.4252.74
QK-0246.5528.680.741.444.020.021.130.355.080.0012.3683.14
QK-0340.5539.440.270.290.510.021.040.401.900.0116.1497.31
QK-0444.3937.330.410.801.410.021.660.321.010.0112.6993.63
QK-0545.2736.790.421.001.520.021.650.340.910.0012.1292.79
QK-0118.414.860.580.390.400.020.1840.821.140.0232.7780.34
Table 3. Trace element contents of mineralized samples and limestone samples (μg/g) in Xian’an coalfield, Guangxi.
Table 3. Trace element contents of mineralized samples and limestone samples (μg/g) in Xian’an coalfield, Guangxi.
SampleLiBeScTiVCrMnCoNiCuZnGaRbSrYZrNbMoSnCsBa
QK-060.940.481.3571.58 11.55 64.64 63.39 0.649.428.394.070.681.35989.9923.486.800.460.430.170.1012.70
QK-02185.383.1518.31 6281.66118.3436.29 32.70 7.8210.448.0513.4427.76115.10 236.6424.71510.9125.073.788.9717.39353.92
QK-031319.833.528.385579.9592.30 83.94 19.83 6.9433.9423.6324.1423.7712.9121.1824.94362.7133.316.957.388.7830.96
QK-041001.223.8921.49 9418.01418.82798.6811.365.3376.3824.0967.6132.8440.7655.3537.71729.5980.1923.407.9015.64121.48
QK-051009.043.9414.55 9284.82366.16569.7210.36 4.9369.1023.3633.8926.7342.8659.0630.37740.0777.2522.646.9515.51117.11
QK-0111.13 0.818.40 1153.6358.31 104.53161.070.558.096.1512.835.3510.341535.3532.91130.0610.161.431.532.5543.55
SampleLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaWTlPbThU
QK-069.3713.27 2.069.471.87 0.472.440.402.200.501.430.191.130.170.170.060.120.021.120.595.34
QK-0226.8062.24 6.2722.884.17 0.613.600.805.381.163.380.563.890.5515.191.955.411.5843.4435.2111.52
QK-0337.56110.11 10.1739.127.69 1.026.471.025.411.123.120.503.200.4511.922.413.481.3342.8120.6416.76
QK-0443.40115.50 11.0141.558.46 1.197.331.387.971.634.500.744.870.7020.455.104.150.9842.0830.0628.16
QK-0540.99115.60 10.3438.157.29 1.035.961.116.511.353.710.614.070.5921.224.974.181.0541.8826.6528.13
QK-0151.9872.40 11.8045.157.95 1.156.121.005.301.052.830.412.590.343.650.660.360.075.018.176.90
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Zhang, L.; Zhang, D.; Zhang, F.; Lin, Z.; Sun, J.; Yan, X.; Xu, H.; Di, S.; Huang, S.; Xu, X.; et al. Discussion on the Geochemical Characteristics and Enrichment Process of Li-Rich Layers in Xian’an Coalfield, Guangxi Province, China. Minerals 2025, 15, 404. https://doi.org/10.3390/min15040404

AMA Style

Zhang L, Zhang D, Zhang F, Lin Z, Sun J, Yan X, Xu H, Di S, Huang S, Xu X, et al. Discussion on the Geochemical Characteristics and Enrichment Process of Li-Rich Layers in Xian’an Coalfield, Guangxi Province, China. Minerals. 2025; 15(4):404. https://doi.org/10.3390/min15040404

Chicago/Turabian Style

Zhang, Li, Degao Zhang, Fuqiang Zhang, Zhongyue Lin, Jie Sun, Xiaoyun Yan, Huiheng Xu, Shaobo Di, Shaoqing Huang, Xiaotao Xu, and et al. 2025. "Discussion on the Geochemical Characteristics and Enrichment Process of Li-Rich Layers in Xian’an Coalfield, Guangxi Province, China" Minerals 15, no. 4: 404. https://doi.org/10.3390/min15040404

APA Style

Zhang, L., Zhang, D., Zhang, F., Lin, Z., Sun, J., Yan, X., Xu, H., Di, S., Huang, S., Xu, X., & Zou, Z. (2025). Discussion on the Geochemical Characteristics and Enrichment Process of Li-Rich Layers in Xian’an Coalfield, Guangxi Province, China. Minerals, 15(4), 404. https://doi.org/10.3390/min15040404

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