Geological Significance of Rare Earth Elements in Marine Shale of the Upper Permian Dalong Formation in the Lower Yangtze Region, South China
by
Chaogang Fang
1,2,
Chengcheng Zhang
1,3,*,
Ning Huang
1,
Long Teng
1,
Chunhai Li
4,
Wei Shao
1 and
Min Zeng
2,* 1
Nanjing Center, China Geological Survey, Nanjing 210016, China
2
School of Earth Sciences, Yunnan University, Kunming 650500, China
3
Exploration Research Institute, Anhui Provincial Bureau of Coal Geology, Hefei 230088, China
4
Harbin Natural Resources Comprehensive Investigation Center, China Geological Survey, Harbin 150081, China
*
Authors to whom correspondence should be addressed.
Minerals 2023, 13(9), 1195; https://doi.org/10.3390/min13091195
Submission received: 20 August 2023
/
Revised: 5 September 2023
/
Accepted: 8 September 2023
/
Published: 12 September 2023
Abstract
:The rare earth elements (REEs) provide significant geological information and serve as a reliable indicator for predicting the paleoclimate, paleoenvironment, and paleotectonic evolution of sedimentary rocks. The REEs, major elements, and trace elements of 75 marine shale samples collected from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were analyzed. The results revealed that the major elements Al2O3, K2O, and TiO2 were primarily influenced by clay minerals associated with terrigenous detrital, whereas SiO2 and Na2O were not affected by clay minerals. The ΣREE values obtained from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region were found to be lower than those of the Post-Archean Average Shale (PAAS) (184.8 μg/g). The study of REE indicators related to the source, redox conditions, and tectonic settings led to the following conclusions: (a) ΣREE showed strong positive correlations with TiO2, Al2O3, K2O, and Na2O, but exhibited relatively weak correlations with Fe2O3 and P2O5, suggesting that REEs were mainly associated with clay minerals, but were also influenced by pyrite, phosphates, and other minerals; (b) The high values of Ce/Ce*, MoEF, UEF, and Corg/P were mainly concentrated in Stages I, II, III and V of the Dalong Formation at the FTS and PTL sections, and the corresponding strong anoxic environment was more conducive to the preservation of organic matter; (c) The diagram between La/Yb and ΣREE, Al2O3-TiO2, TiO2-Zr, and La/Th-Hf bivariate diagrams indicated that the provenance of the rocks from the Dalong formations was primarily felsic igneous rocks; (d) Discriminant-function diagrams and La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 triangular diagrams show that the clastic sediments of the Dalong formations were derived most likely from continental island arcs. This study corresponds to the background of the transition from continental margin to continental collision structure in South China during the Late Permian.
1. Introduction
Rare earth elements (REEs) constitute a set of very special elements. REEs which have good stability, are widely distributed in sedimentary rocks and are frequently used to infer sediment source areas, sedimentary tectonic background, paleoenvironment and paleoclimate, etc. [1,2]. In addition, REE geochemical data are simple and repetitive, and can be used in combination with other geological phenomena or parameters to effectively interpret and improve information on sedimentary environments and tectonic settings [3,4,5,6,7]. Therefore, it is crucial to determine the parameters of rare earth elements (REEs) in sedimentary rocks and clarify their characteristics.
The Upper Permian Dalong organic-rich shales, which are widely dispersed, serve as source rocks, particularly in the Yangtze region. These shales possess significant potential for shale gas development due to their high total organic carbon (TOC) content, considerable thickness, moderate to high thermal maturity, and abundant gas content [8,9]. Previous studies mainly analyzed the redox environment [10,11], input of terrigenous [12,13,14], paleogeographic and hydrographic environment [15] and inversion of paleoproductivity [16,17] through the contents of major elements, trace elements and the ratios of relevant elements of the Dalong Formation. However, the ultimate intention is to discuss the correlation between the TOC content and each of the above conditions [10,14,15,18], and to infer the enrichment principle of organic matter (OM) from the shales of the Dalong Formation in the Lower Yangtze region. The research on REEs in Dalong Formation shales is relatively limited, mainly concentrated in the middle Yangtze region. Liu et al. (2019) [9] determined by means of rare earth element content, partition model and relevant element ratio that the Upper Permian Dalong Formation in western Hubei was formed in an active continental margin environment, and the provenance has a felsic rock attribute. Wu et al. (2021) [17] described the REEs of the black shales at the bottom of the Dalong Formation as a continental margin sedimentary background, mainly from felsic and basic mixture in the middle Yangtze region. Their interpretations of REEs are always used as a supplement to the main and trace elements, ignoring the source characteristics, tectonic background, deposition rate, and a series of other information contained in the REEs [15,16,19,20,21,22,23]. Previous studies used major elements and trace elements to infer the enrichment principle of organic matter is the “trunk” of unconventional oil and gas theory, and the information such as provenance characteristics and structural background contained in REEs themselves as the “root” of the big tree. Only by objectively and accurately depicting the “production” conditions of the Dalong Formation shale, can we better discuss the enrichment mechanism of OM. Recently drilled shale gas wells (HY-1 and GD-1) in the Lower Yangtze region have demonstrated enormous potential of the Dalong Formation as a source of shale gas [24,25,26]. The REE geochemical research and data accumulation from the black shales of the Dalong Formation are seriously insufficient, and it is impossible to accurately and objectively comment on the conditions of “production” of the shale.
Two well-preserved sections of the Dalong Formation have recently been found in the Lower Yangtze region, taking advantage of quarrying activities. The two sections are located in the Chaohu and Tongling areas of Anhui Province, respectively, where there are many layers of well-preserved black shales, which provide favorable conditions for REEs’ study. Based on the characteristics and variation trends of REEs, major elements and trace elements in the Dalong Formation of the Permian in the Fantiansi (FTS) section and the Putaoling (PTL) section, sedimentary environment, provenance attribute and tectonic setting of the Dalong Formation black shale in the study area are interpreted, which is helpful to understand the formation mechanism of the Dalong Formation shale and provide a certain geological basis for the subsequent exploration and development of shale gas and even metal raw material in the Lower Yangtze region.
2. Geological Setting
The Lower Yangtze region was situated within the Yangtze platform, along the northeastern margin of the Yangtze block in South China (Figure 1a). During the Permian–Triassic Boundary (PTB), the region exhibited a NE–SW structural pattern and was connected to the Qinling paleoocean in the northwest and the Cathaysian Block in the southeast [27,28]. The Yangtze platform underwent a transformation from a continental marginal basin to a rift basin in the Late Permian. Influenced by the Emeishan mantle plume, the Yangtze platform experienced extensional subsidence and a large-scale transgression (Figure 1b) [29,30]. The sedimentary facies in the Lower Yangtze region transitioned from shallow delta plain facies during the Wuchiapingian stage to deep basin facies during the early Changhsingian stage, resulting in the formation of organic-rich black shale [31]. The late Changhsingian period witnessed a decrease in sea level, leading to the development of platform margin facies in the study area. These facies are characterized by a high-energy, shallow-water environment and an increased input of terrigenous debris [10,18].
The Fantiansi and Putaoling sections are located in different depositional environments of the Lower Yangtze region (Figure 1b). There is a significant difference in lithology between the two sections. Thin layers of bioclastic limestone are developed at the boundary between the Dalong Formation and Longtan Formation in the Putaoling section (Figure 1c), while the lithology at the boundary of the Fantianshi section transitions from sandy mudstone to siliceous rock (Figure 1d).
3. Samples and Methods
A total of 75 fresh and unweathered samples of black shales were collected from the Fantiansi section and the Putaoling section. All of these samples were pulverized to 200 mesh for geochemical analysis. Thirty-nine samples were from the Fantiansi section and 36 samples were from the Putaoling section.
Based on the outcrop descriptions and thin section observations, petrological and geochemical analyses were conducted. These analyses included the examination of total organic carbon (TOC), major, trace, and rare earth elements. The East China Mineral Resources Testing Center, which is affiliated with the Ministry of Natural Resources, was responsible for carrying out these analyses.
The major element analysis was conducted using an Axios mAX X-ray fluorescence spectrometer, which achieved an analytical precision of better than 1% for major element concentrations. The testing process adhered to the Chinese National Standards GB/T 14506.14-2010 and GB/T 14506.28-2010. For trace element and REEs analysis, an iCAP Q inductively coupled plasma mass spectrometer (ICP-MS) was employed, with a relative error in the data of less than 5%, following the Chinese National Standard GB/T 14506.30-2010. Total organic carbon (TOC) analysis was performed using a LECCO CS230 infrared carbon and sulfur meter at the Experimental Research Center of the East China Oil and Gas Branch of the China Petroleum and Chemical Corporation. Sample treatment for TOC analysis followed the Chinese National Standard GB/T19145-2003.
To eliminate the impact of artificial factors, the anomalies for cerium (Ce/Ce*), europium (Eu/Eu*), and praseodymium (Pr/Pr*) were calculated using established methods. Specifically, Ce/Ce* = 2 × CeN/(LaN + PrN) [34] was used for cerium, Eu/Eu* = 2EuN/(SmN + GdN) [35] for europium, and 2 × PrN/(CeN + NdN) for praseodymium [34]. In these equations, N refers to elemental concentrations normalized to Post-Archean Average Shale (PAAS) [35,36].
Paleoenvironmental conditions can be inferred from the variation in the elemental composition of certain reference materials [37]. The authigenic fraction of elemental abundances may be obfuscated by detrital input, which is why it is customary to normalize and compare the data by calculating enrichment factors (EFs). Enrichment factors are determined by dividing the ratio of the sample element to aluminum by the ratio of the standard element to aluminum. If the EF for a specific element is greater than 1, then that element is enriched relative to the reference material, while if it is less than 1, then it is depleted [37].
Two discriminant functions utilize major element diagrams to distinguish between different tectonic settings of siliciclastic sediments [38]. The diagrams classify sediments into two types based on their (SiO2)adj values: low-silica type (35%–63%) and high-silica type (63%–95%). All major oxides should be adjusted to 100% after excluding the LOI quantity, and are denoted as (X)adj, where X refers to the major oxides.
High silica type discriminant function equations are as follows: DF1(Arc-Rift-Col)m1 = (−0.263 × In(TiO2/SiO2)adj) + (0.604 × In(Al2O3/SiO2)adj) + (−1.725 × In(Fe2O3t/SiO2)adj) + (0.660 × In(MnO/SiO2)adj) + (2.191 × In(MgO/SiO2)adj) + (0.144 × In(CaO/SiO2)adj) + (−1.304 × In(Na2O/SiO2)adj) + (0.054 × In(K2O/SiO2)adj)+ (−0.330 × In(P2O5/SiO2)adj) + 1.588.
DF2(Arc-Rift-Col)m1 = (−1.196 × In(TiO2/SiO2)adj) + (1.604 × In (Al2O3/SiO2)adj) + (0.303 × In(Fe2O3t/SiO2)adj) + (0.436 × In(MnO/SiO2)adj) + (0.838 × In(MgO/SiO2)adj) + (−0.407 × In(CaO/SiO2)adj) + (1.021 × In(Na2O/SiO2)adj) + (−1.706 × In(K2O/SiO2)adj)+ (−0.126 × In(P2O5/SiO2)adj) − 1.068.
The subscript m1 in DF1 and DF2 denotes the high-silica diagram, which is based on the logarithmic ratios of major elements.
Low silica type discriminant function equations are as follows: DF1(Arc-Rift-Col)m2 = (0.608 × In(TiO2/SiO2)adj) + (−1.854 × In(Al2O3/SiO2)adj) + (0.299 × In(Fe2O3t/SiO2)adj) + (−0.550 × In(MnO/SiO2)adj) + (0.120 × In(MgO/SiO2)adj) + (0.194 × In(CaO/SiO2)adj) + (−1.510 × In(Na2O/SiO2)adj) + (1.941 × In(K2O/SiO2)adj) + (0.003 × In (P2O5/SiO2)adj) − 0.294.
DF2(Arc-Rift-Col)m2 = (−0.554×In(TiO2/SiO2)adj) + (−0.995 × In(Al2O3/SiO2)adj) + (1.765 × In(Fe2O3t/SiO2)adj) + (−1.391 × In(MnO/SiO2)adj)+ (−1.034 × In(MgO/SiO2)adj) + (0.225 × In(CaO/SiO2)adj) + (0.713 × In(Na2O/SiO2)adj) + (0.330 × In(K2O/SiO2)adj) + (0.637 × In(P2O5/SiO2)adj) − 3.631.
The subscript “m2” in DF1 and DF2 denotes the low-silica diagram that is based on the log ratios of major elements.
4. Result
4.1. Total Organic Carbon
The total organic carbon (TOC) content of marine shales is a crucial parameter for shale gas exploration. Analysis of samples from the FTS section of the Dalong Formation revealed a range in TOC content of 0.44% to 13.58% (average = 4.36%). The TOC content of samples from the PTL section was higher, ranging from 0.30% to 16.98% (average = 5.85%). The TOC variation trend in the FTS section was found to be similar to that observed in the PTL section (Table 1).
4.2. Major Elements
Table 1 presents the analytical results for major elements, revealing that the predominant compounds were SiO2, CaO, Al2O3, Fe2O3, K2O, and MgO. These major elements exhibited variations within the Dalong Formation at the FTS and PTL sections. To investigate the relationship between minerals and major elements, correlations among the major elements were examined.
Al and Ti were identified as potential indicators of clay minerals and terrigenous detrital due to their close association with clay minerals derived from terrigenous detrital sources [39,40]. The Dalong Formation in the FTS section can be divided into five phases based on the stratigraphic variation of Al2O3 content (Figure 2). During Stage I, the Al2O3 content in the FTS section is relatively low, ranging from 1.43% to 2.96%, with an average of 2.14%. In Stage II, the Al2O3 content starts to fluctuate rapidly, reaching multiple pulse-like peaks (up to 10.32%). Stage III is characterized by another episode with relatively lower Al2O3 content, with a variation range between 1.53% and 8.89%, and an average value of 4.81%. Stage IV exhibits a rapid rise in Al2O3 content, with the highest peak ranging from 7.34% to 11.88%, before decreasing to 3.74% in Phase V. Thus, the two episodes with the most significant terrestrial input enhancement are in Stages II and IV. The Al2O3 content of the Dalong Formation in the PTL section is significantly higher than that in the FTS section, with a varied range of 1.89%–16.31% (average = 10.35%) and is similarly divided into five stages (Figure 3). The Al2O3 content has a strong positive correlation with TiO2 and K2O, indicating that Al2O3 is mainly derived from clay minerals (see Figure 4a,b).
The content of TiO2 in the Dalong Formation of the FTS section is low, with a distribution range of 0.05%–0.67% (average 0.23%), and the change trend is similar to the Al2O3 content (Figure 2). Similarly, the TiO2 content of the Dalong Formation in the PTL section is significantly higher than the FTS section, ranging from 0.07%–0.57% (0.38% on average). The TiO2 content is strongly positively correlated with Al2O3 (Figure 4a) and K2O (Figure 4c), showing that the TiO2 content is mainly influenced by clay minerals.
The Stage II (0.84%–1.94%, 1.52% on average) and IV (1.20%–2.30%, 1.75% on average) of the Dalong formation at the FTS section has a higher K2O content than the Stage I (0.18%–0.57%, 0.30% on average), Stage III (0.17%–1.28%, 0.66% on average), and the Stage V (0.68%–1.93%, 1.22% on average), and the change trend is similar to the Al2O3 content. The content of K2O in the Dalong Formation at the PTL section is considerably greater than that in the FTS section, with a range of variation of 0.27% to 3.11% (average = 1.86%). A strong and positive correlation exists between the K2O content and that of the Al2O3 (Figure 4b) and TiO2 (Figure 4c), suggesting that K2O is mainly controlled by clay minerals.
The Na2O content of the Dalong Formation in the FTS section has 10 values less than 0.10% at Stage I, and the highest Na2O content is mainly distributed in the Stage II of the Dalong Formation (Table 1). The Na2O content of the Dalong Formation in the PTL section is generally higher than the FTS section (Table 1). The Na2O is weakly positively correlated with Al2O3 (Figure 4d) and TiO2 (Figure 4e), and Na2O is poorly correlated with K2O (Figure 4f) and SiO2(Figure 4g), showing the Na2O source is relatively complex. The SiO2 content of the Dalong Formation in the FTS section is relatively high (34.29%–94.16%, 74.27% on average), especially at Stage I where chert appears, with SiO2 content greater than 90% (Table 1). The SiO2 content of the Dalong Formation in the PTL section is 23.03%–86.69%, with an average of 64.04%. Overall, the SiO2 content in the FTS section was higher than that in the PTL section (Table 1). Additionally, the SiO2 content is weakly correlated with that of Na2O (Figure 4g), Al2O3 (Figure 4h), TiO2 (Figure 4i), and K2O (Figure 4j), indicating that SiO2 was not controlled by terrigenous detrital material.
4.3. Rare Earth Elements
The REE contents of 75 marine shale samples from the Dalong Formation are shown in Table 2, and Table 3 lists the calculation results of the special parameters and ratios of REEs. ΣREE values of the marine shale varied from the Dalong Formation at the FTS and the PTL sections. ΣREE values of the samples from the FTS section (15.2–151.2 μg/g, average = 77.3 μg/g) are lower than that of PAAS (184.8 μg/g). Additionally, the ΣREE values of the marine shale (31.8–201.4 μg/g, average = 122.0 μg/g) at the PTL section are also lower than that of PAAS (184.8 μg/g) except for some samples from the upper Dalong Formation.
The light REEs (LREEs)/heavy REEs (HREEs) (L/H) ratio can reflect the differentiation degree of LREEs and HREEs in the rocks. In the same type of rocks, a large ratio indicates that LREEs and HREEs have obvious differentiation. The L/H ratios of the marine shale from the Dalong Formation (2.90–17.12, average = 6.84) at the FTS section, and most L/H ratios were below that of PAAS (9.49), except for the samples from the upper Dalong Formation. In addition, the L/H ratios of the marine shale from the PTL section (4.70–12.24, average = 8.42) were similar to that of PAAS (9.49). To conclude, the marine shales in the PTL section of LREEs and HREEs have more obvious differentiation than the FTS section.
4.4. REE Distribution Patterns
The REE distribution patterns of the samples are normalized to the PAAS (Figure 5). The distribution patterns of each sample show minimal variation, except for Stage I at the FTS section. The curves are approximately parallel, and the overall fluctuation range is low, indicating that the material source is stable. The ratios of (La/Sm)N can represent the differentiation degree of LREEs and HREEs, respectively. The ratios of (La/Sm)N from the Dalong Formation (0.41–2.31, average = 0.93) show a significant vertical variation in the FTS section, similar to the trend of change in Al2O3. The ratios of (La/Sm)N of the samples from Stage II and Stage III are similar and higher than those of Stage I, Stage IV and Stage V, suggesting that the differentiation degree of the LREEs and HREEs of the samples from Stage II and Stage III are higher than that from Stage I, Stage IV and Stage Ⅴ. The ratios of (La/Sm)N of the samples from Stage I (0.71–1.51, average = 1.09), Stage IV (0.66–1.01, average = 0.88) and Stage Ⅴ (0.82–1.03, average = 0.93) were lower than those of Stage II (1.00–2.68, average = 1.58) and Stage III (0.94–1.85, average = 1.38) at the PTL section, suggesting that the differentiation degree of the LREEs and HREEs of the samples from Stage I, Stage IV and Stage Ⅴ were lower than Stage II and Stage III of the Dalong formations.
4.5. Data Validity Discrimination
Due to their relatively stable chemical properties, REEs can preserve numerous original geochemical features during deposition [1,2,5]. However, the content of some REEs is modified under the influence of diagenesis, resulting in changes in the distribution patterns of REEs, which may weaken the significance of ∑REE as an indicator of the original depositional environment, physical source, and tectonic setting [41]. During diagenesis, Ce/Ce* exhibits a strong correlation with Eu/Eu* and REE [42]. The poor correlation between Ce/Ce* and ΣREE (Figure 6a), and Eu/Eu* (Figure 6b), in marine shales of the Late Permian Dalong Formation in the Fantiansi and Putaoling sections of the Lower Yangzi region, suggests that the Ce anomaly remains practically unaffected by diagenesis. It is worth noting that positive La anomalies can lead to significant negative Ce anomalies when samples exhibit Pr/Pr* within the range of 0.95 to 1.05 [34,42]. Nearly all samples of the Dalong Formation exhibit Ce/Ce* < 1 and Pr/Pr* > 1 (Figure 6c), suggesting that the negative Ce/Ce* anomalies were not caused by La enrichment, but rather resulted from normal seawater deposition.
5. Discussion
5.1. REE Occurrence Mode
Condie (1991) [1] suggests that clay minerals are more significant in hosting HREEs and LREEs than zircon and other heavy minerals in craton shale. The detritus undergoes a complete mixing process during weathering and sediment transport, resulting in shale REE patterns reflecting the overall REE pattern of the sources. Although most elements have been affected by intense weathering, REEs, Th, and Sc are still regarded as immobile [2].
In this study (see Figure 7), the linear correlation between ΣREE and major compounds (SiO2, TiO2, Al2O3, Fe2O3, K2O, Na2O, and P2O5) was analyzed. The results revealed that TiO2, Al2O3, and K2O had a positive correlation with ΣREE, suggesting that the majority of REEs in marine shale from the Dalong Formation were primarily associated with clay minerals such as kaolinite and illite [15], which are commonly found in detritus at the FTS and PTL sections. Conversely, the correlation between ΣREE and Fe2O3, P2O5 was relatively weak, indicating that some REEs in marine shale might have occurred in pyrite and phosphates at the FTS and PTL sections [9].
5.2. Redox Conditions
The redox environment affects the circulation, differentiation, and enrichment of various elements in the water column. Environmental changes leave rich geochemical records in sedimentary rocks. Therefore, the relevant element indicators in rocks are important evidence for qualitative restoration of the ancient redox environment [43,44].
As a variable valence element, Ce can reflect the redox condition of the water column during deposition, because the depth of the water column controls the redox condition and the loss degree of Ce. Under oxidation conditions, Ce3 + is oxidized to insoluble Ce4 + and then depleted [45,46]. Therefore, the Ce anomaly (Ce/Ce*) can be used as a redox indicator. In addition, the larger the Ce/Ce*, the more reductive it is. Ce/Ce* > 0.78 implies anoxic conditions and Ce/Ce* < 0.78 denotes oxic conditions [47]. Trace elements such as Mo and U are recognized as redox-sensitive elements. Their sensitivity to oxygen availability at the bottom water and sediment interfaces has been widely utilized to reconstruct the redox state of ancient oceans [37,48,49]. The sedimentary organic carbon to phosphorus content ratio (Corg/P) can be utilized to investigate organic carbon and phosphorus burial and is a reliable indicator of redox conditions in bottom waters [48]. With the progress of sedimentation, the variation law of sediment-water medium is recorded in sedimentary rocks, therefore, the variation process of the relative oxidation–reduction state can be judged from the variation trend of Ce/Ce*, MoEF, UEF, and Corg/P.
The reduction intensity of marine shale from the Dalong formation at the FTS section (Ce/Ce* = 0.78–0.96, average = 0.91) show an anoxic condition of the water column (Figure 2), and the PTL section (Ce/Ce* = 0.79–0.98, average = 0.90) was the same (Figure 3). According to the vertical evolution (Figure 2), the high values of MoEF, UEF, and Corg/P were mainly concentrated in Stages I, II, III and V of the Dalong Formation, and the corresponding strong anoxic environment was more conducive to the preservation of organic matter. The average TOC content of Stages I, II, III and V is 5.14%, and the highest is 13.58%, while the average TOC content of Stage IV is 0.86%. The PTL section displays similar variation patterns to the FTS section, in which samples remains relatively higher MoEF, UEF, and Corg/P values of Stages I, II, III and V. In addition, Liao et al. (2019) [15] studied the redox state of the Dalong Formation in Xuancheng, Anhui province, and found that the lower part of the Dalong Formation presented a reduction state of hypoxia, and the middle and upper part formed in a weak reducing water column and were transformed into a euxinic environment again at the top of the Dalong Formation, which was consistent with the conclusions drawn in this paper.
5.3. Source of Detrital Minerals
REEs play a significant role in determining the source of detrital minerals in sedimentary rocks due to their stable geochemical properties and inheritance. Many geologists have studied the behavior of REEs in order to speculate on the mineral source in sedimentary rocks, and several models have been proposed [5,50], such as the widely used model that could identify the source of detrital minerals based on the relationship between La/Yb and REE [50]. In addition, various major oxide-based discrimination diagrams (e.g., Al2O3, K2O, TiO2) have traditionally been used in several studies on sedimentary rocks to identify the provenance [51,52]. Moradi et al. (2016) [53] have reported that the Al2O3/TiO2 ratios differ for various types of igneous rocks, ranging from 3 to 8 for mafic rocks, 8 to 21 for intermediate rocks, and 21 to 70 for felsic rocks. The composition of source rocks is identified using the TiO2–Zr diagram; TiO2/Zr ratios below 55 suggest felsic igneous rocks, while TiO2/Zr ratios ranging from 55 to 200 indicate intermediate rocks. High TiO2/Zr ratios above 200 are associated with mafic rocks [52]. Additionally, several trace elements’ concentrations and ratios, including Sc, La, Th, Zr, Hf, and Nb, are valuable in identifying the provenance as they are generally considered immobile during sedimentation [36,54,55].
The REE distribution pattern in Figure 8a clearly shows that all samples at the FTS and PTL profiles have the same characteristics for REEs, pointing to the same source of detrital minerals. In addition, the La/Yb and REE maps reveal that most of the marine shale samples from the Dalong Formation in the FTS and PTL sections are plotted on the sedimentary rock field, while others are plotted on the continental schist. Al2O3/TiO2 values of the samples at FTS (Al2O3/TiO2 = 9.67–44.89, average = 25.88) and PTL (Al2O3/TiO2 = 21.56–30.63, average = 26.94) sections suggest that the source rocks for the sediment in the Dalong formations are mostly intermediate-felsic igneous rocks (Figure 8b). Based on the TiO2 versus Zr plot, the sedimentary rocks from the Dalong formations are characterized by felsic igneous source rocks (Figure 8c). In the Hf diagram (Figure 8d), the majority of samples are located within the felsic source field or mixed felsic. According to the provenance discrimination diagrams, it can be concluded that the majority of the source rocks were felsic.
5.4. Tectonic Setting
Tectonic setting discrimination diagrams, which utilize major, trace, and rare earth elements, have become a common method for distinguishing the tectonic settings of sedimentary basins [5,50]. Verma and Armstrong-Altrin (2013) [38] introduced two discriminant functions utilizing major element diagrams to differentiate siliciclastic sediments originating from three primary tectonic settings: island or continental arcs, rifts, and collisions. For the high silica diagram (Figure 9a), most of the high silica samples from the Dalong formations are plotted on the island or continental arcs, with several samples plotted on the collisions. In the low silica diagram (Figure 9b), most of the samples were plotted on the island or continental arcs, with six samples plotted on the boundary between the island or continental arcs and collisions. These two discriminant-function diagrams reflect that the sediments from the Dalong formations probably originated from the island or continental arcs and collisions.
Bhatia and Crook studied the trace elements of five ancient graywacke with known tectonic environments in eastern Australia [55]. The results show that trace element fingerprints are also a good indicator of the tectonic environment and establish a discriminative map for the paleo-tectonic setting. From the triangular diagrams of La–Th–Sc, Th–Sc–Zr/10 and Th–Co–Zr/10 established by Bhatia and Crook, it could be seen that most samples were plotted onto the continental island arc setting and only a few samples were plotted onto the continental margin (Figure 10).
The contents of REEs in shale samples from FTS and PTL sections are compared with sandstones (Table 4). The results show that: REE values of the samples at FTS (REE = 15.2–151.2 μg/g, average = 77.3 μg/g) and PTL (REE = 32–201 μg/g, average = 121 μg/g) sections are close to the continental island arc (REE = 146 ± 20 μg/g). The average contents of La and Ce in the FTS section are 16.3 μg/g and 30.6 μg/g, which are between the oceanic island arc and the continental island arc. The average content values of La and Ce in the PTL section are 27.4 μg/g and 56.8 μg/g, which are close to the continental island arc. The average values of La/Yb and LREE/HREE are 9.3 and 6.8 in the FTS section, which is lower than the PTL section (La/Yb range from 5.0 to 15.6 with an average of 11.0, LREE/HREE ange from 4.70 to 12.24 with an average of 8.42), which are all close to the continental island arc (La/Yb = 11.0 ± 3.6, LREE/HREE = 7.7 ± 1.7). The average Eu values of FTS and PTL sections are 0.84 and 0.88, which are also close to the continental island arc (0.79 ± 0.13). Combined with the above interpretation, it is confirmed that the tectonic setting of the Dalong Formation shale provenance in the Lower Yangtze area, which belongs to the PTL and FTS sections, is continental island arc.
During the Late Devonian to Middle Triassic, after the Caledonian movement, the active continental margin subsidence areas on the north and south sides of the Lower Yangtze were closed and uplifted, the continental crust thickened, and the overall performance was a stable cratonic environment. With the partial closure of the Paleotethys Ocean, the Yangtze and North China plates continued to compress, and the seawater in the Lower Yangtze region was fully released at the end of the Middle Triassic [15]. At the end of the Late Permian–Early Triassic, the degree of aggregation of the Pangea supercontinent continued to deepen, and its periphery would continue to be subducted by the pan-Oceanic, thus forming a large amount of felsic volcanism in this area [53,57].
Gao et al. (2013) [58] determined that the tectonic setting of South China in the Late Permian was an environment where magma arcs converged at the continental margin and transformed into continental collisions, or a local post-collision environment, which is consistent with the conclusion of this study on continental island arcs.
6. Conclusions
Based on the major elements, trace elements and REEs analyses of marine shales from the Dalong formations (Late Permian) in the FTS and PTL sections, we conclude the following:
- The summation of rare earth elements (ΣREE) exhibited strong positive correlations with TiO2, Al2O3, K2O, and Na2O, but relatively weak correlations with Fe2O3 and P2O5. These observations suggest that REEs were primarily associated with clay minerals but may also have been influenced by pyrite.
- The elevated concentrations of Ce/Ce*, MoEF, UEF, and Corg/P are predominantly found in Stages I, II, III, and V of the Dalong Formation at the FTS and PTL sections, indicating a strong anoxic environment that facilitates the preservation of organic matter.
- The diagram between La/Yb and ΣREE, Al2O3–TiO2, TiO2–Zr and La/Th–Hf bivariate diagrams indicate that the provenance of the marine shale from the Dalong formations was primarily from felsic igneous rocks. In addition, discriminant-function diagrams and triangular diagrams of La–Th–Sc, Th–Co–Zr/10, and Th–Sc–Zr/10 suggest that the clastic sediments of the Dalong Formation were likely derived from continental island arcs.
Author Contributions
Conceptualization, C.F. and C.Z.; methodology, C.F. and M.Z.; formal analysis, C.F., C.Z. and N.H.; investigation, C.F., C.Z. and C.L.; writing—original draft preparation, C.F. and M.Z.; visualization, C.F. and C.Z.; project administration, L.T. and W.S. All authors have read and agreed to the published version of the manuscript.
Funding
This work is supported by the China Geological Survey Oil and Gas Program (DD 20221662) and the National Natural Science Foundation of China (42302124).
Data Availability Statement
The data presented in this study are available upon request from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
(a) Global paleogeographic map of the Permian–Triassic Boundary interval (ca. 252 Ma) (modified after Shen et al. 2012 [32]) (b) Paleogeographic reconstruction map of the Yangtze Platform in the Changhsingian stage (modified from Feng and Gu, 2002 [33]). (c) Stratigraphic columns of the Putaoling section. (d) Stratigraphic columns of the Fantiansi section.
Figure 1.
(a) Global paleogeographic map of the Permian–Triassic Boundary interval (ca. 252 Ma) (modified after Shen et al. 2012 [32]) (b) Paleogeographic reconstruction map of the Yangtze Platform in the Changhsingian stage (modified from Feng and Gu, 2002 [33]). (c) Stratigraphic columns of the Putaoling section. (d) Stratigraphic columns of the Fantiansi section.
Figure 2.
Vertical variations of TOC, Ce/Ce*, MoEF, UEF, Corg/P, ΣREE, Al2O3, TiO2, (La/Sm) N, and Eu/Eu* of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) section in the Lower Yangtze region.
Figure 2.
Vertical variations of TOC, Ce/Ce*, MoEF, UEF, Corg/P, ΣREE, Al2O3, TiO2, (La/Sm) N, and Eu/Eu* of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) section in the Lower Yangtze region.
Figure 3.
Vertical variations of TOC, Ce/Ce*, MoEF, UEF, Corg/P, ΣREE, Al2O3, TiO2, (La/Sm) N, and Eu/Eu* of the marine shale from the Late Permian Dalong Formation at the Putaoling (PTL) section in the Lower Yangtze region.
Figure 3.
Vertical variations of TOC, Ce/Ce*, MoEF, UEF, Corg/P, ΣREE, Al2O3, TiO2, (La/Sm) N, and Eu/Eu* of the marine shale from the Late Permian Dalong Formation at the Putaoling (PTL) section in the Lower Yangtze region.
Figure 4.
Relationships of (a) TiO2 vs. Al2O3, (b) Al2O3 vs. K2O, (c) TiO2 vs. Na2O, (d) Na2O vs. K2O, (e) Al2O3 vs. Na2O, (f) Na2O vs. K2O, (g) SiO2 vs. Na2O, (h) TiO2 vs. Al2O3, (i) SiO2 vs. TiO2, (j) SiO2 vs. K2O of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region.
Figure 4.
Relationships of (a) TiO2 vs. Al2O3, (b) Al2O3 vs. K2O, (c) TiO2 vs. Na2O, (d) Na2O vs. K2O, (e) Al2O3 vs. Na2O, (f) Na2O vs. K2O, (g) SiO2 vs. Na2O, (h) TiO2 vs. Al2O3, (i) SiO2 vs. TiO2, (j) SiO2 vs. K2O of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region.
Figure 5.
Distribution patterns of REEs for the marine shale from the Late Permian Dalong Formation at (a) the Fantiansi (FTS) section and (b) the Putaoling (PTL) section in the Lower Yangtze region.
Figure 5.
Distribution patterns of REEs for the marine shale from the Late Permian Dalong Formation at (a) the Fantiansi (FTS) section and (b) the Putaoling (PTL) section in the Lower Yangtze region.
Figure 6.
Relationships of (a) ΣREE vs. Ce/Ce*, (b) Eu/Eu* vs. Ce/Ce*, (c) Pr/Pr* vs. Ce/Ce* of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region. Field a: neither Ce nor La anomaly; Field a1: positive La anomaly causes apparent negative Ce anomaly; Field b1: negative La anomaly causes apparent positive Ce anomaly; Field a2: real positive Ce anomaly; Field b2: real negative Ce anomaly.
Figure 6.
Relationships of (a) ΣREE vs. Ce/Ce*, (b) Eu/Eu* vs. Ce/Ce*, (c) Pr/Pr* vs. Ce/Ce* of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region. Field a: neither Ce nor La anomaly; Field a1: positive La anomaly causes apparent negative Ce anomaly; Field b1: negative La anomaly causes apparent positive Ce anomaly; Field a2: real positive Ce anomaly; Field b2: real negative Ce anomaly.
Figure 7.
Relationships of (a) ΣREE vs. TOC, (b) ΣREE vs. SiO2, (c) ΣREE vs. TiO2, (d) ΣREE vs. Al2O3, (e) ΣREE vs. Fe2O3, (f) ΣREE vs. Na2O, (g) ΣREE vs. K2O, (h) ΣREE vs. P2O5, of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region.
Figure 7.
Relationships of (a) ΣREE vs. TOC, (b) ΣREE vs. SiO2, (c) ΣREE vs. TiO2, (d) ΣREE vs. Al2O3, (e) ΣREE vs. Fe2O3, (f) ΣREE vs. Na2O, (g) ΣREE vs. K2O, (h) ΣREE vs. P2O5, of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region.
Figure 8.
(a) ΣREE (μg/g) versus La/Yb bivariate diagram (modified from Allègre and Minster, 1978 [50]), (b) Al2O3 (%) versus TiO2 (%) diagram bivariate diagram (modified Hayashi et al., 1997 [52]), (c) TiO2 (%) versus Zr (μg/g) bivariate diagram (modified Hayashi et al., 1997 [52]), (d) La/Th versus Hf (μg/g) bivariate diagram (modified Floyd and Leveridge, 1987) [56] from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region.
Figure 8.
(a) ΣREE (μg/g) versus La/Yb bivariate diagram (modified from Allègre and Minster, 1978 [50]), (b) Al2O3 (%) versus TiO2 (%) diagram bivariate diagram (modified Hayashi et al., 1997 [52]), (c) TiO2 (%) versus Zr (μg/g) bivariate diagram (modified Hayashi et al., 1997 [52]), (d) La/Th versus Hf (μg/g) bivariate diagram (modified Floyd and Leveridge, 1987) [56] from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections in the Lower Yangtze region.
Figure 9.
(a) New discriminant function multi-dimensional diagram for high-silica clastic sediments from three tectonic settings (arc, rift and collision). (b) New discriminant function multi-dimensional diagram for low-silica clastic sediments from three tectonic settings (arc, rift and collision) (modified from Verma and Armstrong-Altrin, 2013 [38]).
Figure 9.
(a) New discriminant function multi-dimensional diagram for high-silica clastic sediments from three tectonic settings (arc, rift and collision). (b) New discriminant function multi-dimensional diagram for low-silica clastic sediments from three tectonic settings (arc, rift and collision) (modified from Verma and Armstrong-Altrin, 2013 [38]).
Figure 10.
(a) La–Th–Sc plot, (b) Th–Sc–Zr/10 plot and (c) Th–Co–Zr/10 plot of the shales from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections for tectonic discrimination. Dotted lines represent the dominant fields for sedimentary rocks from various tectonic settings (modified from Bhatia and Crook, 1986 [55]). A: oceanic island arc; B: continental island arc; C: active continental margin; D: passive margin.
Figure 10.
(a) La–Th–Sc plot, (b) Th–Sc–Zr/10 plot and (c) Th–Co–Zr/10 plot of the shales from the Late Permian Dalong Formation at the Fantiansi (FTS) and the Putaoling (PTL) sections for tectonic discrimination. Dotted lines represent the dominant fields for sedimentary rocks from various tectonic settings (modified from Bhatia and Crook, 1986 [55]). A: oceanic island arc; B: continental island arc; C: active continental margin; D: passive margin.
Table 1.
Total organic carbon (TOC) and major element contents of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region (%).
Table 1.
Total organic carbon (TOC) and major element contents of the marine shale from the Late Permian Dalong Formation at the Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region (%).
| Sample | Lithology | TOC | Al2O3 | CaO | Fe2O3 | K2O | MgO | MnO | Na2O | P2O5 | SiO2 | TiO2 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| FTS-1 | Carbonaceous shale | 4.07 | 8.85 | 11.54 | 5.24 | 1.93 | 0.89 | 0.04 | 0.47 | 0.13 | 53.34 | 0.33 |
| FTS-2 | Carbonaceous shale | 8.51 | 5.19 | 7.21 | 2.13 | 0.94 | 0.47 | 0.02 | 0.49 | 0.08 | 65.77 | 0.22 |
| FTS-3 | Calcareous shale | 3.44 | 3.74 | 30.24 | 1.68 | 0.68 | 0.40 | 0.01 | 0.27 | 0.15 | 34.29 | 0.14 |
| FTS-4 | Carbonaceous shale | 4.59 | 8.22 | 11.08 | 2.61 | 1.34 | 1.05 | 0.02 | 0.57 | 0.07 | 57.98 | 0.26 |
| FTS-5 | Calcareous shale | 0.44 | 8.22 | 10.10 | 1.94 | 1.36 | 3.69 | 0.09 | 0.45 | 0.07 | 57.53 | 0.28 |
| FTS-6 | Calcareous shale | 1.95 | 13.41 | 5.36 | 3.11 | 2.30 | 1.18 | 0.03 | 0.86 | 0.10 | 59.86 | 0.52 |
| FTS-7 | Calcareous shale | 0.69 | 10.90 | 3.18 | 3.29 | 1.86 | 0.88 | 0.02 | 0.92 | 0.07 | 66.10 | 0.43 |
| FTS-8 | Calcareous shale | 0.48 | 11.88 | 4.31 | 2.88 | 2.03 | 1.64 | 0.03 | 0.66 | 0.13 | 64.12 | 0.39 |
| FTS-9 | Calcareous shale | 0.61 | 11.14 | 3.67 | 2.34 | 1.74 | 1.59 | 0.03 | 0.65 | 0.09 | 67.91 | 0.31 |
| FTS-10 | Calcareous shale | 1.1 | 7.34 | 4.60 | 1.41 | 1.20 | 0.58 | 0.02 | 0.41 | 0.07 | 75.38 | 0.24 |
| FTS-11 | Calcareous shale | 0.72 | 5.79 | 16.72 | 1.37 | 0.77 | 1.31 | 0.04 | 0.71 | 0.27 | 55.30 | 0.18 |
| FTS-12 | Carbonaceous shale | 9.79 | 3.86 | 28.92 | 1.48 | 0.40 | 1.22 | 0.04 | 0.59 | 0.69 | 35.76 | 0.09 |
| FTS-13 | Carbonaceous shale | 1.67 | 6.32 | 3.22 | 1.62 | 0.97 | 1.24 | 0.02 | 0.46 | 0.04 | 75.14 | 0.24 |
| FTS-14 | Carbonaceous shale | 7.04 | 4.26 | 4.51 | 2.03 | 0.63 | 1.03 | 0.02 | 0.46 | 0.29 | 73.67 | 0.19 |
| FTS-15 | Carbonaceous shale | 1.77 | 7.02 | 5.12 | 2.26 | 0.90 | 1.59 | 0.03 | 0.87 | 0.36 | 67.61 | 0.22 |
| FTS-16 | Siliceous shale | 1.77 | 1.53 | 2.69 | 0.54 | 0.17 | 0.62 | 0.02 | 0.16 | 0.05 | 89.21 | 0.06 |
| FTS-17 | Siliceous shale | 6.26 | 1.90 | 0.90 | 0.76 | 0.24 | 0.19 | 0.02 | 0.11 | 0.02 | 90.41 | 0.07 |
| FTS-18 | Siliceous shale | 6.77 | 4.24 | 0.48 | 0.95 | 0.55 | 0.45 | 0.01 | 0.68 | 0.03 | 84.89 | 0.17 |
| FTS-19 | Siliceous shale | 11.42 | 3.55 | 1.33 | 1.03 | 0.42 | 0.94 | 0.01 | 0.65 | 0.02 | 83.71 | 0.15 |
| FTS-20 | Siliceous shale | 9.35 | 4.59 | 0.21 | 0.99 | 0.68 | 0.31 | 0.01 | 0.69 | 0.03 | 84.89 | 0.18 |
| FTS-21 | Siliceous shale | 4.13 | 4.65 | 0.69 | 0.98 | 0.66 | 0.59 | 0.01 | 0.72 | 0.05 | 85.92 | 0.17 |
| FTS-22 | Siliceous shale | 2.29 | 5.90 | 0.29 | 1.35 | 0.96 | 0.34 | 0.00 | 0.54 | 0.20 | 78.94 | 0.25 |
| FTS-23 | Siliceous shale | 4.2 | 8.89 | 0.18 | 11.96 | 1.28 | 0.39 | 0.00 | <0.1 | 0.06 | 70.81 | 0.67 |
| FTS-24 | Siliceous shale | 4.01 | 8.49 | 0.12 | 1.58 | 1.20 | 0.43 | 0.00 | 1.18 | 0.16 | 72.41 | 0.30 |
| FTS-25 | Siliceous shale | 13.58 | 10.32 | 0.53 | 1.86 | 1.66 | 0.56 | 0.00 | 1.30 | 0.55 | 62.61 | 0.39 |
| FTS-26 | Siliceous shale | 6.09 | 7.99 | 0.06 | 1.82 | 1.49 | 0.52 | 0.00 | 0.66 | 0.03 | 72.93 | 0.33 |
| FTS-27 | Siliceous shale | 6.64 | 8.80 | 0.11 | 2.46 | 1.81 | 0.53 | 0.00 | 0.32 | 0.26 | 72.18 | 0.33 |
| FTS-28 | Siliceous shale | 7.95 | 9.13 | 0.25 | 3.85 | 1.94 | 0.49 | 0.00 | 0.37 | 0.36 | 68.72 | 0.36 |
| FTS-29 | Siliceous shale | 4.95 | 5.06 | 0.07 | 2.91 | 0.84 | 0.32 | 0.01 | 0.18 | 0.23 | 79.83 | 0.20 |
| FTS-30 | Siliceous shale | 13.12 | 8.84 | 0.23 | 1.18 | 1.67 | 0.60 | 0.00 | 0.29 | 0.39 | 71.57 | 0.35 |
| FTS-31 | Chert | 2.71 | 2.56 | 0.13 | 0.69 | 0.39 | 0.18 | 0.02 | <0.1 | 0.16 | 91.21 | 0.09 |
| FTS-32 | Chert | 2.05 | 1.47 | 0.12 | 1.06 | 0.21 | 0.12 | 0.02 | <0.1 | 0.06 | 92.91 | 0.09 |
| FTS-33 | Chert | 1.69 | 1.64 | 0.12 | 1.16 | 0.24 | 0.14 | 0.03 | <0.1 | 0.07 | 93.08 | 0.08 |
| FTS-34 | Chert | 7.04 | 2.77 | 0.72 | 0.21 | 0.57 | 0.23 | 0.01 | <0.1 | 0.02 | 80.18 | 0.29 |
| FTS-35 | Chert | 2.25 | 2.12 | 0.08 | 0.50 | 0.34 | 0.17 | 0.01 | <0.1 | 0.05 | 92.95 | 0.10 |
| FTS-36 | Chert | 0.99 | 2.73 | 0.17 | 1.32 | 0.26 | 0.13 | 0.03 | <0.1 | 0.05 | 92.80 | 0.12 |
| FTS-37 | Chert | 2.07 | 1.56 | 0.09 | 0.64 | 0.18 | 0.10 | 0.02 | <0.1 | 0.06 | 94.07 | 0.08 |
| FTS-38 | Chert | 1.59 | 1.43 | 0.17 | 0.84 | 0.18 | 0.11 | 0.01 | <0.1 | 0.06 | 94.16 | 0.05 |
| FTS-39 | Siliceous shale | 0.58 | 2.96 | 0.26 | 1.43 | 0.37 | 0.19 | 0.01 | <0.1 | 0.16 | 90.22 | 0.14 |
| PTL-1 | Carbonaceous shale | 9.14 | 10.68 | 9.14 | 5.38 | 2.45 | 1.03 | 0.03 | 0.47 | 0.14 | 51.68 | 0.40 |
| PTL-2 | Calcareous shale | 0.67 | 1.89 | 36.25 | 1.14 | 0.27 | 2.60 | 0.07 | 0.31 | 0.12 | 24.29 | 0.07 |
| PTL-3 | Calcareous shale | 2.65 | 6.03 | 28.21 | 2.75 | 1.14 | 0.80 | 0.04 | 0.70 | 0.16 | 32.67 | 0.23 |
| PTL-4 | Carbonaceous shale | 9.81 | 8.59 | 4.15 | 4.34 | 1.72 | 0.75 | 0.01 | 0.56 | 0.15 | 62.01 | 0.32 |
| PTL-5 | Carbonaceous shale | 11.93 | 10.36 | 4.70 | 3.53 | 2.02 | 0.85 | 0.01 | 0.80 | 0.12 | 60.83 | 0.40 |
| PTL-6 | Calcareous shale | 9.35 | 10.75 | 7.24 | 5.45 | 2.08 | 1.04 | 0.02 | 0.91 | 0.16 | 52.01 | 0.40 |
| PTL-7 | Calcareous shale | 4.52 | 10.16 | 8.42 | 3.75 | 1.98 | 1.13 | 0.02 | 0.62 | 0.17 | 57.73 | 0.36 |
| PTL-8 | Carbonaceous shale | 3.57 | 11.24 | 6.60 | 3.31 | 2.14 | 1.36 | 0.02 | 0.74 | 0.12 | 61.19 | 0.39 |
| PTL-9 | Calcareous shale | 16.98 | 8.04 | 12.93 | 4.77 | 1.48 | 0.70 | 0.02 | 0.74 | 0.46 | 41.28 | 0.32 |
| PTL-10 | Shale | 0.47 | 16.31 | 2.09 | 3.78 | 3.21 | 1.76 | 0.05 | 0.60 | 0.13 | 63.26 | 0.57 |
| PTL-11 | Calcareous shale | 0.3 | 3.46 | 25.69 | 3.81 | 0.57 | 10.09 | 0.45 | <0.1 | 0.13 | 23.03 | 0.15 |
| PTL-12 | Shale | 0.85 | 14.78 | 4.22 | 4.25 | 2.73 | 1.59 | 0.07 | 0.92 | 0.10 | 59.71 | 0.50 |
| PTL-13 | Siliceous shale | 1.76 | 8.55 | 0.36 | 2.74 | 1.54 | 0.58 | 0.00 | 0.55 | 0.07 | 79.50 | 0.34 |
| PTL-14 | Carbonaceous shale | 5 | 15.89 | 0.17 | 3.88 | 3.11 | 1.23 | 0.00 | 0.76 | 0.11 | 64.02 | 0.55 |
| PTL-15 | Carbonaceous shale | 5.42 | 15.14 | 0.18 | 1.54 | 2.81 | 1.15 | 0.00 | 1.10 | 0.05 | 68.18 | 0.50 |
| PTL-16 | Carbonaceous shale | 4.75 | 9.06 | 0.14 | 1.06 | 1.57 | 0.60 | 0.00 | 0.99 | 0.03 | 78.92 | 0.35 |
| PTL-17 | Carbonaceous shale | 2.7 | 10.24 | 0.44 | 3.58 | 1.57 | 0.64 | 0.01 | 1.37 | 0.10 | 75.03 | 0.40 |
| PTL-18 | Carbonaceous shale | 3.23 | 10.97 | 0.20 | 2.24 | 1.94 | 0.78 | 0.01 | 0.84 | 0.06 | 75.40 | 0.39 |
| PTL-19 | Carbonaceous shale | 5.96 | 13.72 | 0.29 | 5.27 | 2.43 | 1.14 | 0.00 | 1.39 | 0.22 | 61.19 | 0.49 |
| PTL-20 | Siliceous shale | 4.03 | 13.19 | 0.29 | 4.84 | 2.41 | 0.99 | 0.00 | 1.09 | 0.19 | 64.67 | 0.45 |
| PTL-21 | Siliceous shale | 8.2 | 7.86 | 0.11 | 0.71 | 1.40 | 0.54 | 0.00 | 0.85 | 0.03 | 77.91 | 0.35 |
| PTL-22 | Siliceous shale | 1.84 | 8.28 | 0.13 | 0.93 | 1.33 | 0.54 | 0.00 | 1.06 | 0.03 | 82.05 | 0.30 |
| PTL-23 | Siliceous shale | 5.16 | 10.99 | 0.07 | 1.56 | 1.64 | 0.65 | 0.00 | 1.80 | 0.05 | 73.76 | 0.39 |
| PTL-24 | Siliceous shale | 11.8 | 12.98 | 0.06 | 1.50 | 2.25 | 0.90 | 0.00 | 1.36 | 0.04 | 63.85 | 0.52 |
| PTL-25 | Siliceous shale | 9.15 | 13.45 | 0.57 | 1.18 | 2.28 | 0.95 | 0.00 | 1.39 | 0.42 | 63.75 | 0.45 |
| PTL-26 | Siliceous shale | 10.83 | 14.24 | 0.12 | 0.99 | 2.46 | 1.01 | 0.00 | 1.63 | 0.05 | 63.67 | 0.57 |
| PTL-27 | Siliceous shale | 6.59 | 14.08 | 0.11 | 1.14 | 2.35 | 0.99 | 0.00 | 1.67 | 0.06 | 59.40 | 0.53 |
| PTL-28 | Siliceous shale | 5.58 | 13.93 | 2.32 | 2.61 | 2.59 | 1.06 | 0.00 | 0.87 | 1.74 | 57.95 | 0.52 |
| PTL-29 | Siliceous shale | 6.03 | 14.47 | 0.79 | 2.35 | 2.68 | 1.12 | 0.00 | 0.85 | 0.81 | 62.14 | 0.52 |
| PTL-30 | Siliceous shale | 5.82 | 7.25 | 0.18 | 1.51 | 1.17 | 0.47 | 0.01 | 0.81 | 0.05 | 79.86 | 0.30 |
| PTL-31 | Siliceous shale | 5.67 | 9.27 | 0.07 | 2.25 | 1.61 | 0.67 | 0.00 | 0.47 | 0.10 | 74.01 | 0.32 |
| PTL-32 | Siliceous shale | 6.24 | 5.88 | 0.12 | 1.31 | 0.88 | 0.40 | 0.01 | 0.56 | 0.06 | 83.51 | 0.19 |
| PTL-33 | Siliceous shale | 2.61 | 4.04 | 0.17 | 2.20 | 0.44 | 0.21 | 0.01 | 0.76 | 0.09 | 86.69 | 0.14 |
| PTL-34 | Chert | 13.2 | 7.95 | 0.41 | 1.81 | 1.46 | 0.62 | 0.00 | 0.46 | 0.06 | 76.19 | 0.32 |
| PTL-35 | Chert | 4.27 | 10.63 | 0.74 | 3.07 | 1.76 | 0.73 | 0.00 | 1.16 | 0.47 | 70.73 | 0.41 |
| PTL-36 | Siliceous shale | 4.58 | 8.37 | 2.69 | 1.55 | 1.53 | 0.60 | 0.01 | 0.65 | 1.84 | 73.37 | 0.39 |
Table 2.
Rare earth element (REE) contents of the marine shale from the Late Permian Dalong Formation at Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region (μg/g).
Table 2.
Rare earth element (REE) contents of the marine shale from the Late Permian Dalong Formation at Fantiansi (FTS) and Putaoling (PTL) sections in the Lower Yangtze region (μg/g).
| Sample | Lithology | La | Ce | Pr | Nd | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| FTS-1 | Carbonaceous shale | 22.0 | 42.2 | 5.0 | 18.3 | 3.4 | 0.7 | 3.4 | 0.6 | 3.0 | 0.6 | 1.9 | 0.3 | 2.1 | 0.3 |
| FTS-2 | Carbonaceous shale | 13.7 | 25.7 | 3.1 | 12.0 | 2.3 | 0.5 | 2.4 | 0.4 | 2.2 | 0.4 | 1.3 | 0.2 | 1.4 | 0.2 |
| FTS-3 | Calcareous shale | 9.0 | 16.6 | 2.0 | 7.2 | 1.3 | 0.3 | 1.3 | 0.2 | 1.2 | 0.3 | 0.8 | 0.1 | 0.9 | 0.1 |
| FTS-4 | Carbonaceous shale | 23.8 | 47.4 | 5.6 | 20.8 | 3.8 | 0.6 | 3.7 | 0.6 | 3.2 | 0.7 | 2.0 | 0.3 | 2.1 | 0.3 |
| FTS-5 | Calcareous shale | 26.0 | 51.6 | 5.8 | 20.9 | 3.8 | 0.7 | 3.8 | 0.7 | 3.6 | 0.7 | 2.4 | 0.4 | 2.8 | 0.4 |
| FTS-6 | Calcareous shale | 31.4 | 58.1 | 7.0 | 25.4 | 4.4 | 0.8 | 4.0 | 0.7 | 3.4 | 0.7 | 2.3 | 0.4 | 2.5 | 0.4 |
| FTS-7 | Calcareous shale | 21.1 | 42.4 | 4.9 | 17.1 | 3.0 | 0.5 | 2.8 | 0.5 | 2.5 | 0.5 | 1.6 | 0.3 | 1.8 | 0.3 |
| FTS-8 | Calcareous shale | 32.1 | 60.9 | 7.7 | 28.0 | 5.2 | 0.8 | 5.0 | 0.8 | 4.1 | 0.8 | 2.4 | 0.4 | 2.6 | 0.4 |
| FTS-9 | Calcareous shale | 26.0 | 48.8 | 6.1 | 22.4 | 4.5 | 0.5 | 4.2 | 0.7 | 3.8 | 0.8 | 2.4 | 0.4 | 2.5 | 0.4 |
| FTS-10 | Calcareous shale | 21.2 | 41.0 | 5.1 | 19.1 | 3.6 | 0.6 | 3.6 | 0.7 | 3.6 | 0.8 | 2.4 | 0.4 | 2.6 | 0.4 |
| FTS-11 | Calcareous shale | 28.5 | 53.1 | 6.5 | 24.6 | 5.9 | 0.8 | 6.2 | 1.1 | 5.8 | 1.2 | 3.4 | 0.5 | 3.5 | 0.5 |
| FTS-12 | Carbonaceous shale | 25.8 | 44.4 | 5.7 | 23.0 | 5.4 | 1.1 | 6.4 | 1.2 | 6.6 | 1.4 | 4.4 | 0.7 | 4.9 | 0.8 |
| FTS-13 | Carbonaceous shale | 12.4 | 23.2 | 2.4 | 6.7 | 0.8 | 0.2 | 0.9 | 0.2 | 1.1 | 0.3 | 0.9 | 0.2 | 1.3 | 0.2 |
| FTS-14 | Carbonaceous shale | 14.2 | 27.3 | 3.1 | 11.1 | 2.1 | 0.4 | 2.3 | 0.4 | 2.2 | 0.5 | 1.4 | 0.2 | 1.6 | 0.3 |
| FTS-15 | Carbonaceous shale | 19.9 | 41.6 | 5.0 | 19.0 | 3.9 | 0.6 | 4.1 | 0.7 | 3.7 | 0.7 | 2.2 | 0.3 | 2.3 | 0.3 |
| FTS-16 | Siliceous shale | 3.2 | 5.6 | 0.7 | 2.5 | 0.5 | 0.1 | 0.6 | 0.1 | 0.6 | 0.1 | 0.5 | 0.1 | 0.6 | 0.1 |
| FTS-17 | Siliceous shale | 3.5 | 6.8 | 0.9 | 3.2 | 0.6 | 0.1 | 0.7 | 0.1 | 0.6 | 0.1 | 0.4 | 0.1 | 0.4 | 0.1 |
| FTS-18 | Siliceous shale | 6.7 | 12.3 | 1.4 | 4.9 | 0.8 | 0.1 | 0.8 | 0.2 | 0.9 | 0.2 | 0.7 | 0.1 | 0.9 | 0.2 |
| FTS-19 | Siliceous shale | 7.6 | 14.2 | 1.7 | 6.0 | 1.1 | 0.2 | 1.0 | 0.2 | 1.1 | 0.3 | 0.8 | 0.2 | 1.1 | 0.2 |
| FTS-20 | Siliceous shale | 13.1 | 24.1 | 2.9 | 10.5 | 1.8 | 0.3 | 1.7 | 0.3 | 1.9 | 0.4 | 1.4 | 0.2 | 1.8 | 0.3 |
| FTS-21 | Siliceous shale | 14.0 | 27.6 | 3.4 | 12.6 | 2.6 | 0.4 | 2.4 | 0.4 | 2.0 | 0.4 | 1.2 | 0.2 | 1.3 | 0.2 |
| FTS-22 | Siliceous shale | 11.3 | 20.5 | 2.6 | 10.0 | 2.0 | 0.4 | 2.2 | 0.4 | 2.1 | 0.5 | 1.4 | 0.2 | 1.6 | 0.3 |
| FTS-23 | Siliceous shale | 31.8 | 58.3 | 6.8 | 23.2 | 2.9 | 0.5 | 2.3 | 0.3 | 1.5 | 0.3 | 1.1 | 0.2 | 1.3 | 0.2 |
| FTS-24 | Siliceous shale | 22.0 | 36.6 | 4.8 | 17.0 | 3.3 | 0.6 | 3.6 | 0.6 | 3.2 | 0.7 | 2.0 | 0.3 | 2.2 | 0.3 |
| FTS-25 | Siliceous shale | 29.2 | 53.7 | 6.8 | 25.3 | 4.9 | 0.9 | 4.9 | 0.8 | 4.5 | 0.9 | 2.9 | 0.5 | 3.4 | 0.5 |
| FTS-26 | Siliceous shale | 19.2 | 36.2 | 4.1 | 13.6 | 1.8 | 0.3 | 1.8 | 0.3 | 1.9 | 0.4 | 1.4 | 0.2 | 1.8 | 0.3 |
| FTS-27 | Siliceous shale | 16.2 | 29.1 | 3.3 | 11.2 | 1.8 | 0.4 | 1.9 | 0.3 | 1.9 | 0.4 | 1.4 | 0.2 | 1.8 | 0.3 |
| FTS-28 | Siliceous shale | 20.8 | 39.3 | 4.6 | 16.0 | 2.8 | 0.6 | 2.9 | 0.5 | 2.9 | 0.6 | 2.1 | 0.3 | 2.4 | 0.4 |
| FTS-29 | Siliceous shale | 13.0 | 25.1 | 3.1 | 12.3 | 2.7 | 0.5 | 2.9 | 0.5 | 2.4 | 0.5 | 1.4 | 0.2 | 1.5 | 0.2 |
| FTS-30 | Siliceous shale | 29.1 | 57.7 | 7.6 | 29.2 | 5.6 | 0.9 | 5.2 | 0.9 | 4.3 | 0.9 | 2.5 | 0.4 | 2.6 | 0.4 |
| FTS-31 | Chert | 6.1 | 12.0 | 1.5 | 6.3 | 1.9 | 0.4 | 1.8 | 0.3 | 1.2 | 0.2 | 0.7 | 0.1 | 0.7 | 0.1 |
| FTS-32 | Chert | 3.1 | 6.3 | 0.9 | 3.6 | 0.8 | 0.2 | 0.8 | 0.1 | 0.7 | 0.1 | 0.4 | 0.1 | 0.4 | 0.1 |
| FTS-33 | Chert | 5.3 | 10.6 | 1.4 | 5.4 | 1.4 | 0.2 | 1.4 | 0.2 | 1.2 | 0.3 | 0.8 | 0.1 | 0.8 | 0.1 |
| FTS-34 | Chert | 16.4 | 28.9 | 3.6 | 12.5 | 1.9 | 0.3 | 1.8 | 0.3 | 1.8 | 0.4 | 1.3 | 0.2 | 1.5 | 0.2 |
| FTS-35 | Chert | 5.8 | 11.0 | 1.4 | 5.3 | 1.2 | 0.2 | 1.2 | 0.2 | 1.1 | 0.2 | 0.7 | 0.1 | 0.8 | 0.1 |
| FTS-36 | Chert | 7.2 | 12.0 | 1.7 | 7.0 | 1.9 | 0.4 | 2.7 | 0.5 | 2.8 | 0.6 | 1.7 | 0.2 | 1.6 | 0.2 |
| FTS-37 | Chert | 5.0 | 8.2 | 1.1 | 4.1 | 0.9 | 0.2 | 0.9 | 0.2 | 0.9 | 0.2 | 0.5 | 0.1 | 0.5 | 0.1 |
| FTS-38 | Chert | 4.8 | 9.2 | 1.4 | 5.9 | 1.7 | 0.3 | 1.7 | 0.3 | 1.6 | 0.3 | 1.0 | 0.1 | 1.0 | 0.1 |
| FTS-39 | Siliceous shale | 13.2 | 22.6 | 3.2 | 12.4 | 2.4 | 0.5 | 2.6 | 0.4 | 2.4 | 0.5 | 1.4 | 0.2 | 1.4 | 0.2 |
| PTL-1 | Carbonaceous shale | 29.1 | 53.3 | 6.4 | 23.2 | 4.4 | 0.9 | 4.5 | 0.8 | 4.0 | 0.8 | 2.6 | 0.4 | 2.9 | 0.4 |
| PTL-2 | Calcareous shale | 6.7 | 11.7 | 1.4 | 5.6 | 1.2 | 0.3 | 1.3 | 0.2 | 1.2 | 0.3 | 0.8 | 0.1 | 0.8 | 0.1 |
| PTL-3 | Calcareous shale | 17.9 | 31.9 | 3.7 | 13.9 | 2.6 | 0.8 | 2.8 | 0.5 | 2.5 | 0.5 | 1.6 | 0.3 | 1.7 | 0.3 |
| PTL-4 | Carbonaceous shale | 23.1 | 44.7 | 5.4 | 20.2 | 3.9 | 0.6 | 3.8 | 0.6 | 2.9 | 0.7 | 2.0 | 0.3 | 2.2 | 0.3 |
| PTL-5 | Carbonaceous shale | 25.4 | 50.6 | 6.0 | 21.6 | 3.6 | 0.6 | 3.6 | 0.6 | 3.1 | 0.6 | 2.0 | 0.3 | 2.2 | 0.3 |
| PTL-6 | Calcareous shale | 26.3 | 49.0 | 6.0 | 21.5 | 4.0 | 0.7 | 3.8 | 0.6 | 3.3 | 0.7 | 2.1 | 0.3 | 2.3 | 0.4 |
| PTL-7 | Calcareous shale | 28.3 | 53.0 | 6.4 | 23.1 | 4.2 | 0.8 | 4.2 | 0.7 | 3.6 | 0.7 | 2.3 | 0.4 | 2.5 | 0.4 |
| PTL-8 | Carbonaceous shale | 26.7 | 51.9 | 6.3 | 22.3 | 3.9 | 0.6 | 3.6 | 0.6 | 3.0 | 0.6 | 1.9 | 0.3 | 2.2 | 0.3 |
| PTL-9 | Calcareous shale | 27.2 | 47.2 | 6.0 | 23.2 | 4.8 | 1.0 | 5.2 | 0.9 | 4.7 | 1.0 | 2.8 | 0.4 | 2.9 | 0.4 |
| PTL-10 | Shale | 39.2 | 74.4 | 8.9 | 32.2 | 5.9 | 0.9 | 5.7 | 1.0 | 5.2 | 1.0 | 3.2 | 0.5 | 3.6 | 0.5 |
| PTL-11 | Calcareous shale | 10.0 | 18.8 | 2.3 | 9.4 | 2.2 | 0.7 | 2.1 | 0.4 | 1.9 | 0.4 | 1.0 | 0.2 | 1.0 | 0.2 |
| PTL-12 | Shale | 36.9 | 67.0 | 8.4 | 29.9 | 5.3 | 1.0 | 5.1 | 0.8 | 4.3 | 0.9 | 2.8 | 0.4 | 3.0 | 0.5 |
| PTL-13 | Siliceous shale | 24.4 | 44.0 | 5.6 | 20.3 | 3.5 | 0.7 | 3.6 | 0.6 | 3.3 | 0.7 | 2.1 | 0.3 | 2.4 | 0.4 |
| PTL-14 | Carbonaceous shale | 38.5 | 70.8 | 8.2 | 27.1 | 3.6 | 0.6 | 3.3 | 0.6 | 3.0 | 0.7 | 2.2 | 0.4 | 2.7 | 0.4 |
| PTL-15 | Carbonaceous shale | 40.7 | 76.1 | 8.6 | 27.8 | 3.2 | 0.5 | 3.2 | 0.5 | 2.9 | 0.7 | 2.2 | 0.4 | 2.6 | 0.4 |
| PTL-16 | Carbonaceous shale | 21.6 | 40.8 | 4.5 | 14.7 | 1.9 | 0.3 | 1.8 | 0.3 | 1.7 | 0.4 | 1.3 | 0.2 | 1.6 | 0.3 |
| PTL-17 | Carbonaceous shale | 26.4 | 50.3 | 6.2 | 22.3 | 4.1 | 0.7 | 3.8 | 0.7 | 3.4 | 0.7 | 2.2 | 0.4 | 2.4 | 0.4 |
| PTL-18 | Carbonaceous shale | 27.1 | 51.0 | 5.9 | 20.7 | 3.2 | 0.5 | 3.0 | 0.5 | 2.7 | 0.6 | 1.9 | 0.3 | 2.3 | 0.4 |
| PTL-19 | Carbonaceous shale | 32.6 | 57.2 | 6.4 | 20.5 | 3.1 | 0.7 | 3.1 | 0.5 | 3.0 | 0.7 | 2.1 | 0.4 | 2.6 | 0.4 |
| PTL-20 | Siliceous shale | 34.2 | 63.2 | 7.4 | 24.5 | 3.8 | 0.6 | 3.4 | 0.5 | 2.9 | 0.6 | 2.0 | 0.3 | 2.4 | 0.4 |
| PTL-21 | Siliceous shale | 21.1 | 39.3 | 4.6 | 15.3 | 2.1 | 0.4 | 2.1 | 0.4 | 2.2 | 0.5 | 1.7 | 0.3 | 2.1 | 0.3 |
| PTL-22 | Siliceous shale | 21.7 | 41.3 | 4.8 | 16.7 | 2.5 | 0.3 | 2.2 | 0.4 | 1.9 | 0.4 | 1.4 | 0.2 | 1.7 | 0.3 |
| PTL-23 | Siliceous shale | 22.8 | 43.5 | 4.9 | 16.1 | 1.9 | 0.3 | 1.8 | 0.3 | 1.7 | 0.4 | 1.4 | 0.2 | 1.7 | 0.3 |
| PTL-24 | Siliceous shale | 29.8 | 54.1 | 6.4 | 20.7 | 2.4 | 0.4 | 2.3 | 0.4 | 2.2 | 0.5 | 1.8 | 0.3 | 2.5 | 0.4 |
| PTL-25 | Siliceous shale | 32.4 | 61.4 | 7.3 | 25.8 | 4.2 | 0.8 | 4.2 | 0.7 | 4.0 | 0.9 | 2.8 | 0.5 | 3.3 | 0.5 |
| PTL-26 | Siliceous shale | 33.0 | 62.3 | 7.6 | 25.5 | 3.1 | 0.5 | 2.7 | 0.5 | 2.6 | 0.6 | 2.1 | 0.4 | 2.7 | 0.4 |
| PTL-27 | Siliceous shale | 31.4 | 52.8 | 5.3 | 16.1 | 1.7 | 0.4 | 1.8 | 0.3 | 1.8 | 0.4 | 1.7 | 0.3 | 2.6 | 0.4 |
| PTL-28 | Siliceous shale | 41.1 | 72.9 | 9.0 | 32.4 | 6.0 | 1.4 | 6.0 | 1.1 | 5.8 | 1.2 | 3.8 | 0.6 | 4.0 | 0.6 |
| PTL-29 | Siliceous shale | 36.1 | 63.9 | 7.8 | 26.8 | 4.6 | 0.9 | 4.5 | 0.8 | 4.4 | 1.0 | 3.1 | 0.5 | 3.8 | 0.6 |
| PTL-30 | Siliceous shale | 16.6 | 32.2 | 3.6 | 11.9 | 1.6 | 0.3 | 1.8 | 0.3 | 1.7 | 0.4 | 1.2 | 0.2 | 1.6 | 0.2 |
| PTL-31 | Siliceous shale | 25.9 | 49.7 | 5.9 | 20.8 | 3.2 | 0.5 | 3.2 | 0.6 | 3.2 | 0.7 | 2.2 | 0.3 | 2.3 | 0.4 |
| PTL-32 | Siliceous shale | 15.2 | 28.7 | 3.4 | 12.3 | 2.0 | 0.4 | 2.1 | 0.4 | 2.2 | 0.5 | 1.6 | 0.3 | 1.9 | 0.3 |
| PTL-33 | Siliceous shale | 7.3 | 13.5 | 1.6 | 6.3 | 1.5 | 0.3 | 1.5 | 0.3 | 1.3 | 0.3 | 0.8 | 0.1 | 1.0 | 0.2 |
| PTL-34 | Chert | 20.1 | 36.8 | 4.4 | 15.5 | 2.6 | 0.5 | 2.6 | 0.5 | 2.4 | 0.5 | 1.7 | 0.3 | 1.9 | 0.3 |
| PTL-35 | Chert | 44.0 | 80.7 | 9.8 | 34.0 | 5.8 | 0.8 | 6.0 | 1.0 | 6.3 | 1.4 | 4.6 | 0.8 | 5.4 | 0.8 |
| PTL-36 | Siliceous shale | 44.1 | 66.6 | 8.8 | 34.0 | 7.3 | 1.2 | 8.0 | 1.5 | 8.6 | 1.9 | 6.0 | 0.9 | 6.5 | 1.0 |
Table 3.
Geochemical parameters associated with rare earth elements (REEs) of the marine shale from the Late Permian Dalong Formation at Fantiansi (FTS) and Putaoling (PTL) sections in Lower Yangtze region.
Table 3.
Geochemical parameters associated with rare earth elements (REEs) of the marine shale from the Late Permian Dalong Formation at Fantiansi (FTS) and Putaoling (PTL) sections in Lower Yangtze region.
| Sample | Lithology | REE (μg/g) | L/H | La/Yb | Ce/Ce* | Eu/Eu* | (La/Sm)n | (Gd/Yb)n |
|---|---|---|---|---|---|---|---|---|
| FTS-1 | Carbonaceous shale | 104 | 7.51 | 10.48 | 0.93 | 0.94 | 0.94 | 0.98 |
| FTS-2 | Carbonaceous shale | 66 | 6.71 | 9.79 | 0.91 | 0.96 | 0.87 | 1.04 |
| FTS-3 | Calcareous shale | 41 | 7.44 | 10.34 | 0.90 | 1.01 | 1.01 | 0.90 |
| FTS-4 | Carbonaceous shale | 115 | 7.91 | 11.33 | 0.95 | 0.71 | 0.91 | 1.07 |
| FTS-5 | Calcareous shale | 124 | 7.35 | 9.29 | 0.97 | 0.80 | 0.99 | 0.82 |
| FTS-6 | Calcareous shale | 141 | 8.89 | 12.56 | 0.90 | 0.85 | 1.04 | 0.97 |
| FTS-7 | Calcareous shale | 99 | 8.73 | 11.72 | 0.96 | 0.83 | 1.02 | 0.94 |
| FTS-8 | Calcareous shale | 151 | 8.18 | 12.35 | 0.89 | 0.76 | 0.90 | 1.16 |
| FTS-9 | Calcareous shale | 123 | 7.16 | 10.40 | 0.89 | 0.57 | 0.84 | 1.02 |
| FTS-10 | Calcareous shale | 105 | 6.31 | 8.15 | 0.91 | 0.73 | 0.86 | 0.84 |
| FTS-11 | Calcareous shale | 142 | 5.37 | 8.14 | 0.90 | 0.63 | 0.70 | 1.07 |
| FTS-12 | Carbonaceous shale | 132 | 4.00 | 5.27 | 0.84 | 0.87 | 0.69 | 0.79 |
| FTS-13 | Carbonaceous shale | 51 | 9.00 | 9.54 | 0.98 | 0.92 | 2.31 | 0.44 |
| FTS-14 | Carbonaceous shale | 67 | 6.59 | 8.88 | 0.95 | 0.85 | 0.98 | 0.87 |
| FTS-15 | Carbonaceous shale | 104 | 6.24 | 8.65 | 0.96 | 0.75 | 0.74 | 1.08 |
| FTS-16 | Siliceous shale | 15 | 4.79 | 5.71 | 0.88 | 1.07 | 0.93 | 0.59 |
| FTS-17 | Siliceous shale | 18 | 6.13 | 8.14 | 0.90 | 1.03 | 0.82 | 0.91 |
| FTS-18 | Siliceous shale | 30 | 6.69 | 7.36 | 0.93 | 0.78 | 1.23 | 0.51 |
| FTS-19 | Siliceous shale | 36 | 6.41 | 6.91 | 0.91 | 0.72 | 1.00 | 0.55 |
| FTS-20 | Siliceous shale | 61 | 6.53 | 7.28 | 0.90 | 0.67 | 1.06 | 0.57 |
| FTS-21 | Siliceous shale | 69 | 7.50 | 10.77 | 0.92 | 0.75 | 0.78 | 1.12 |
| FTS-22 | Siliceous shale | 55 | 5.43 | 7.06 | 0.87 | 0.85 | 0.82 | 0.83 |
| FTS-23 | Siliceous shale | 131 | 17.12 | 24.46 | 0.91 | 0.82 | 1.59 | 1.07 |
| FTS-24 | Siliceous shale | 97 | 6.51 | 10.00 | 0.82 | 0.79 | 0.97 | 0.99 |
| FTS-25 | Siliceous shale | 139 | 6.55 | 8.59 | 0.88 | 0.84 | 0.87 | 0.87 |
| FTS-26 | Siliceous shale | 83 | 9.22 | 10.67 | 0.94 | 0.78 | 1.55 | 0.61 |
| FTS-27 | Siliceous shale | 70 | 7.47 | 9.00 | 0.92 | 0.91 | 1.31 | 0.64 |
| FTS-28 | Siliceous shale | 96 | 6.92 | 8.67 | 0.93 | 0.95 | 1.08 | 0.73 |
| FTS-29 | Siliceous shale | 66 | 5.93 | 8.67 | 0.91 | 0.85 | 0.70 | 1.17 |
| FTS-30 | Siliceous shale | 147 | 7.63 | 11.19 | 0.89 | 0.79 | 0.75 | 1.21 |
| FTS-31 | Chert | 33 | 5.46 | 8.36 | 0.91 | 0.97 | 0.47 | 1.49 |
| FTS-32 | Chert | 17 | 5.74 | 7.95 | 0.89 | 1.11 | 0.55 | 1.23 |
| FTS-33 | Chert | 29 | 4.91 | 6.39 | 0.90 | 0.70 | 0.55 | 1.02 |
| FTS-34 | Chert | 71 | 8.47 | 10.93 | 0.87 | 0.76 | 1.25 | 0.73 |
| FTS-35 | Chert | 29 | 5.56 | 7.34 | 0.89 | 0.86 | 0.70 | 0.92 |
| FTS-36 | Chert | 41 | 2.91 | 4.50 | 0.79 | 0.86 | 0.55 | 1.02 |
| FTS-37 | Chert | 23 | 5.89 | 9.43 | 0.81 | 0.95 | 0.85 | 1.05 |
| FTS-38 | Chert | 29 | 3.80 | 4.95 | 0.81 | 0.75 | 0.41 | 1.06 |
| FTS-39 | Siliceous shale | 63 | 5.95 | 9.43 | 0.80 | 0.86 | 0.80 | 1.12 |
| PTL-1 | Carbonaceous shale | 134 | 7.14 | 10.03 | 0.90 | 0.93 | 0.96 | 0.94 |
| PTL-2 | Calcareous shale | 32 | 5.58 | 8.07 | 0.88 | 1.27 | 0.81 | 0.95 |
| PTL-3 | Calcareous shale | 81 | 7.02 | 10.53 | 0.90 | 1.39 | 1.00 | 1.00 |
| PTL-4 | Carbonaceous shale | 111 | 7.62 | 10.50 | 0.92 | 0.71 | 0.86 | 1.05 |
| PTL-5 | Carbonaceous shale | 121 | 8.44 | 11.55 | 0.95 | 0.78 | 1.03 | 0.99 |
| PTL-6 | Calcareous shale | 121 | 7.97 | 11.43 | 0.90 | 0.88 | 0.96 | 1.00 |
| PTL-7 | Calcareous shale | 131 | 7.85 | 11.32 | 0.91 | 0.87 | 0.98 | 1.02 |
| PTL-8 | Carbonaceous shale | 124 | 8.91 | 12.14 | 0.92 | 0.75 | 0.99 | 0.99 |
| PTL-9 | Calcareous shale | 128 | 5.98 | 9.38 | 0.85 | 0.93 | 0.82 | 1.09 |
| PTL-10 | Shale | 182 | 7.80 | 10.89 | 0.92 | 0.75 | 0.97 | 0.96 |
| PTL-11 | Calcareous shale | 50 | 6.18 | 10.00 | 0.90 | 1.62 | 0.66 | 1.27 |
| PTL-12 | Shale | 166 | 8.34 | 12.30 | 0.88 | 0.88 | 1.01 | 1.03 |
| PTL-13 | Siliceous shale | 112 | 7.34 | 10.17 | 0.87 | 0.88 | 1.01 | 0.91 |
| PTL-14 | Carbonaceous shale | 162 | 11.29 | 14.26 | 0.92 | 0.81 | 1.55 | 0.74 |
| PTL-15 | Carbonaceous shale | 170 | 12.24 | 15.65 | 0.94 | 0.72 | 1.85 | 0.74 |
| PTL-16 | Carbonaceous shale | 91 | 11.09 | 13.50 | 0.95 | 0.81 | 1.65 | 0.68 |
| PTL-17 | Carbonaceous shale | 124 | 7.92 | 11.00 | 0.91 | 0.88 | 0.94 | 0.96 |
| PTL-18 | Carbonaceous shale | 120 | 9.31 | 11.78 | 0.93 | 0.76 | 1.23 | 0.79 |
| PTL-19 | Carbonaceous shale | 133 | 9.45 | 12.54 | 0.91 | 1.07 | 1.53 | 0.72 |
| PTL-20 | Siliceous shale | 146 | 10.66 | 14.25 | 0.92 | 0.81 | 1.31 | 0.86 |
| PTL-21 | Siliceous shale | 92 | 8.66 | 10.05 | 0.92 | 0.80 | 1.46 | 0.61 |
| PTL-22 | Siliceous shale | 96 | 10.35 | 12.76 | 0.93 | 0.64 | 1.26 | 0.78 |
| PTL-23 | Siliceous shale | 97 | 11.51 | 13.41 | 0.95 | 0.79 | 1.74 | 0.64 |
| PTL-24 | Siliceous shale | 124 | 10.93 | 11.92 | 0.90 | 0.82 | 1.80 | 0.56 |
| PTL-25 | Siliceous shale | 149 | 7.82 | 9.82 | 0.92 | 0.87 | 1.12 | 0.77 |
| PTL-26 | Siliceous shale | 144 | 11.05 | 12.22 | 0.91 | 0.80 | 1.55 | 0.61 |
| PTL-27 | Siliceous shale | 117 | 11.48 | 12.08 | 0.93 | 0.94 | 2.68 | 0.42 |
| PTL-28 | Siliceous shale | 186 | 7.05 | 10.28 | 0.87 | 1.09 | 1.00 | 0.91 |
| PTL-29 | Siliceous shale | 159 | 7.51 | 9.50 | 0.88 | 0.91 | 1.14 | 0.72 |
| PTL-30 | Siliceous shale | 74 | 8.91 | 10.38 | 0.96 | 0.80 | 1.51 | 0.68 |
| PTL-31 | Siliceous shale | 119 | 8.25 | 11.26 | 0.93 | 0.73 | 1.18 | 0.84 |
| PTL-32 | Siliceous shale | 71 | 6.70 | 8.00 | 0.92 | 0.80 | 1.10 | 0.67 |
| PTL-33 | Siliceous shale | 36 | 5.65 | 7.60 | 0.91 | 0.94 | 0.71 | 0.95 |
| PTL-34 | Chert | 90 | 7.88 | 10.58 | 0.90 | 0.90 | 1.12 | 0.83 |
| PTL-35 | Chert | 201 | 6.66 | 8.15 | 0.90 | 0.61 | 1.10 | 0.67 |
| PTL-36 | Siliceous shale | 196 | 4.70 | 6.78 | 0.78 | 0.73 | 0.88 | 0.74 |
Ce/Ce* = anomalies for cerium, Eu/Eu* = europium.
Table 4.
The comparison of REE characteristic parameters with those from sandstones in different settings.
Table 4.
The comparison of REE characteristic parameters with those from sandstones in different settings.
| Tectonic Setting | La(μg/g) | Ce(μg/g) | REE(μg/g) | La/Yb | LREE/HREE | Eu/Eu* | Data Source |
|---|---|---|---|---|---|---|---|
| Oceanic island arc | 8 ± 1.7 | 19 ± 3.7 | 58 ± 10 | 4.2 ± 1.3 | 3.8 ± 0.9 | 1.04 ± 0.11 | Bhatia and Crook, 1986 [55] |
| Continental island arc | 27 ± 4.5 | 59 ± 8.2 | 146 ± 20 | 11.0 ± 3.6 | 7.7 ± 1.7 | 0.79 ± 0.13 | |
| Active continental margin | 37 | 78 | 186 | 12.5 | 9.1 | 0.6 | |
| Passive margin | 39 | 85 | 210 | 15.9 | 8.5 | 0.56 | |
| FTS (n = 39) | 16.27 (3.1–32.1) | 30.57 (5.6–60.9) | 77 (15–151) | 9.25 (4.5–24.26) | 6.84 (2.91–17.12) | 0.84 (0.57–1.11) | This study |
| PTL (n = 36) | 27.35 (6.7–44.1) | 56.82 (43.5–80.7) | 121 (32–201) | 11 (4.95–15.65) | 8.42 (4.7–12.24) | 0.88 (0.61–1.62) |
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Fang, C.; Zhang, C.; Huang, N.; Teng, L.; Li, C.; Shao, W.; Zeng, M. Geological Significance of Rare Earth Elements in Marine Shale of the Upper Permian Dalong Formation in the Lower Yangtze Region, South China. Minerals 2023, 13, 1195. https://doi.org/10.3390/min13091195
AMA Style
Fang C, Zhang C, Huang N, Teng L, Li C, Shao W, Zeng M. Geological Significance of Rare Earth Elements in Marine Shale of the Upper Permian Dalong Formation in the Lower Yangtze Region, South China. Minerals. 2023; 13(9):1195. https://doi.org/10.3390/min13091195
Chicago/Turabian StyleFang, Chaogang, Chengcheng Zhang, Ning Huang, Long Teng, Chunhai Li, Wei Shao, and Min Zeng. 2023. "Geological Significance of Rare Earth Elements in Marine Shale of the Upper Permian Dalong Formation in the Lower Yangtze Region, South China" Minerals 13, no. 9: 1195. https://doi.org/10.3390/min13091195
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