Next Article in Journal
Geochemical Characteristics and Metallogenic Significance of the X03 Vein Tourmaline in the Jiajika Rare Metal Deposit, West Sichuan
Next Article in Special Issue
Magmatic Evolution and Rare Metal Mineralization in Mount El-Sibai Peralkaline Granites, Central Eastern Desert, Egypt: Insights from Whole-Rock Geochemistry and Mineral Chemistry Data
Previous Article in Journal
The Role of Stereological Assumptions in Bubble Size Estimations and Their Implications for Assessing Critical Coalescence Concentrations
Previous Article in Special Issue
The Paleoproterozoic Evolution of Basement Rocks of the Taebaeksan Basin, Korean Peninsula, and Their Correlation to Those of the Paleoproterozoic Massifs in the Korean Peninsula
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Genesis and Geological Significance of Siderite in the First Member of the Nantun Formation of Dongming Sag, Hailar Basin

School of Earth Sciences, Key Laboratory of Mineral Resources in Western China (Gansu Province), Lanzhou University, Lanzhou 730000, China
Research Institute of Petroleum Exploration & Development–Northwest, PetroChina, Lanzhou 730020, China
Yanchang Oil Field Co., Ltd., Yan’an 718600, China
Author to whom correspondence should be addressed.
Minerals 2023, 13(6), 804;
Submission received: 9 April 2023 / Revised: 5 June 2023 / Accepted: 10 June 2023 / Published: 13 June 2023


Multiple siderite beds developed in the first member of the Lower Cretaceous Nantun Formation (K1n1) in the basin. The results show that the siderites in K1n1 of the study area are mostly stratiform or massive, with three micromorphological features (dense micronized crystals, bands, and paragenesis with quartz and calcite). The siderite beds are mainly composed of siderite, clay, quartz, calcite, and feldspar. Under the microscope, charcoal, algal fossils, granular pyrite crystals, vein-like siliceous bands, etc., were observed. The oxides in the siderite beds include Fe2O3, SiO2, Al2O3, etc. The trace elements are typically characterized by high Mn and Be contents; low Sr/Ba, Th/U, and Al/Ti ratios; and high V/Cr ratios. These indicate weakly reducing, freshwater depositional paleoenvironments. The δ13Cv-PDB and δ18Ov-PDB values of siderite are −0.20–1.11‰ (mean: 0.62‰) and −18.22‰ to −10.14‰ (mean: −14.23‰), respectively, which shows that the carbon in siderite came mainly from carbonate dissolution. The Fe-bearing rocks in the source area migrated to the basin after undergoing physical and chemical weathering, and when the resultant Fe2+ concentration reached saturation, Fe2+ combined with CO32− in the water bodies to form authigenic siderite.

1. Introduction

Siderite is an important iron-bearing carbonate mineral often found in marine or lacustrine settings, with FeCO3 as its main component [1,2,3,4]. Siderite (FeCO3, density 3960 kg/m3; Hurlbut, 1971) is a brownish translucent mineral crystallizing in the same hexagonal (rhombohedral) lattice as calcite [5]. Large amounts will rarely be attained in an ore deposit because Fe carbonates tend to have a wide range of substitution of Mn, Mg, and Ca for bivalent Fe [6]. In recent years, scholars worldwide have carried out many studies on the characteristics, genetic mechanism, and formation environment of siderite. The genetic mechanism of siderite has long been the focus of debate [1,4,5,6,7,8,9,10,11,12,13,14,15,16]. Tu [17] believed that siderites are of either sedimentogenesis or hydrothermal genesis. Sedimentary siderites are commonly found in shale, clay, and coal beds, often in oolitic and nodular forms, and coexist with oolitic hematite, oolitic chlorite, and goethite. However, although hydrothermal siderites are often found in metalliferous veins, there can be a separate siderite vein or one associated with ankerite, galena, sphalerite, chalcopyrite, magnetite pyrite, and other deposits. Xie et al. [4] analyzed the petrography of different types of siderites and concluded that siderites of different forms correspond to three genetic processes: authigenesis, eodiagenesis (early diagenesis), and telodiagenesis (late diagenetic). They also concluded that siderites derived from different genetic processes have different significance to paleoenvironmental restoration. Frederichs et al. [5] believes that siderite is an authigenic mineral in a number of sedimentary settings. It is restricted to anoxic non-sulfidic methanic environments, and occurs in rapidly accumulating, fine-grained, organic-rich sediments, where CO2 is produced as a result of oxidation of organic matter, partly by reduction of Mn and Fe oxyhydroxides. Köhler et al. [10] suggested that siderite was formed during dissimilatory iron reduction during the early diagenetic stage. Dill pointed out that siderite in clay rock and coal-bearing sandstone related to coal seams is usually produced as spherosiderite, a microcrystalline rhodochrosite. Moreover, near the edge of freshwater lakes, colloidal siderite is often produced in temperate climate [5]. Usually, its formation depends mainly on the Eh and pH conditions in the basin, which determine the variation of iron-bearing minerals from calcareous hematite, magnetite, and rhodonite to siliceous iron ore, and even pyrite. Siderite precipitates at an Eh below 0 (volt) and in the pH range 7 to 9, depending on the activities of the dissolved species Fe and C. Siderite disappears with decreasing activity of HCO3 at log aHCO3 = −3 and increasing activity of HPO42− at log aHPO4 = −3 [Burger et al.]. Zhang et al. [16] believed that the formation of siderites with different micromorphological features is closely related to sea-level fluctuation, which manifests as a cyclical change controlled by the sequence-stratigraphic framework. Additionally, Dill mentioned that a stratiform siderite ore deposit at Arzberg, Germany, intercalated with argillaceous metasediments is a product of post volcanic and microbiological processes [5]. Some scholars believe that siderite was transformed by organic matter reduction under reducing conditions [14,15,16,17,18,19,20]. Siehl and Thein [21] hold that siderite may be converted from silica-rich ferric oxides during diagenesis in a reducing environment. Burkhalter et al. [22] believed that microbial activity probably played also a key role during Fe accumulation in the near-shore environments. Other mechanisms, such as bacterial sulfate reduction, anaerobic oxidation of methane, and thermal decarboxylation of organic matter, can also provide carbon for the formation of siderite [23,24,25]. Despite the complex genesis of siderite, it is generally believed that authigenic siderite is typically formed when soluble, reducing Fe2+ is combined with HCO3/CO32− in an oxygen-deficient, iron-rich, low-sulfate environment. The formation of authigenic siderite is closely related to biological activities [3,26] and can directly indicate a high atmospheric CO2 concentration [4]. The formation of diagenetic siderite mainly reflects the active iron cycle process between water and sediments but cannot directly reflect the atmospheric CO2 concentration [4,18,19]. In continental petroliferous sedimentary basins, carbonate minerals such as calcite and dolomite have a greater impact on the hydrocarbon generation of source rocks [27,28,29,30,31].
Little research has been conducted to clarify whether siderite affects the hydrocarbon generation of source rocks. Nigam et al. [32] pointed out that the formation of siderite is very complex, and the diagenesis associated with siderite formation occurs at the same temperature as the transformation of organic matter to oil and gas. Milesi et al. [11] believed that the hydrogen derived from complete or partial oxidation or dissolution of highly mature kerogen in the heated source rocks reduces siderite to form methane and that the hydrocarbon gas generation from the decomposition of economically viable hydrothermal fluids with siderite may be widespread in petroliferous basins with high thermal stress. Zhang et al. [33,34] performed thermogravimetric experiments to study the effect of siderite on the pyrolysis of organic matter in source rocks of the Dameigou Formation in the northern margin of the Qaidam Basin and concluded that siderite can promote the pyrolysis of organic matter in source rocks. He mentioned that siderite would undergo thermal decomposition at high temperature of about 450~600 °C [33,34].
The present study meticulously analyzes the sedimentary environment and the petrological, geochemical, and isotopic characteristics of siderite developed in the source rocks of the first member of the Nantun Formation (K1n1) in the Dongming sag, Hailar Basin. On this basis, we explore the formation environment and genetic mechanisms of siderite and the influence of siderite on the hydrocarbon generation of source rocks in petroliferous basins, aiming to provide a theoretical basis for oil and gas exploration in this area.

2. Geological Setting

The Hailar Basin is located at the junction of the Erguna block and the Xing’an block in the eastern Xingmeng orogenic belt. To the south, it is integrated with the Tamuchag Basin in northeastern Mongolia. The interior of the basin can be divided into five first-order structural units (three depressions and two uplifts), consisting of sixteen sags [35] (Figure 1a). The basement of the basin is composed of pre-Paleozoic and Paleozoic epimetamorphic rocks. The sedimentary strata of the basin are composed of Mesozoic (Jurassic and Cretaceous) and Cenozoic strata, totaling a thickness of approximately 6000 m. The Mesozoic stratum contains, from bottom to top, the Upper Jurassic Tamulangou Formation (J3tm), the Lower Cretaceous Tongbomiao Formation (K1t), the Nantun Formation (K1n), the Damoguaihe Formation (K1d), the Yimin Formation (K1y), and the Qingyuangang Formation (K2q) [33,34,36,37] (Figure 1c). In this, J3tm is interbedded with volcanic rocks and clastic rock; K1t is mainly composed of sandstone and conglomerate. K1n is composed of sand and mudstone interbedded in shallow lake facies; K1d and K1y are mainly composed of mudstone; K2q is mainly composed of conglomerate. At present, oil and gas exploration in the Hailar Basin is mainly concentrated in the Wuerxun and Beier sags, two oil-rich sags in the central fault zone. Breakthroughs in oil and gas exploration have been made in the Huhehu, Bayanhushu, and Hongqi sags in the Hailar basin, and good hydrocarbon indications have been found in the Yimin and Dongming sags. However, overall, no large-scale hydrocarbon reserves have been formed in the basin. The lacustrine source rocks of the Lower Cretaceous Nantun Formation in the Hailar Basin are dominated by dark mudstones. This set of source rocks has good hydrocarbon generation potential and is the main source rock series in the Hailar Basin. The Dongming sag (the study area) is in the northeastern Hailar Basin. It is a graben-shaped sag that is faulted in the south and overlapped in the north, with an area of 665 km2, showing a structural patten of segmentation in the east–west direction and zonation in the south–north direction (Figure 1b). Well MD2 revealed that the first member of the Nantun Formation (K1n1) contains multiple siderite beds.
Well MD2 is located in the gentle slope zone in the northern Dongming sag, with a drilling depth of 799 m. The well has been contiguously cored from 81.47 m to 798.94 m, with a cumulative core length of 602.63 m and a core recovery rate of 83.4%. The whole-well core revealed the Damoguaihe Formation (K1d), Nantun Formation (K1n), and Tongbomiao Formation (K1t) (not drilled through), from top to bottom. The Damoguaihe Formation (K1d) and the first member of the Nantun Formation (K1n1) are made of semi-deep lacustrine and deep lacustrine dark mudstones, the second member of the Nantun Formation (K1n2) is made of sand–mudstone interbedded delta-front and prodelta deposits, and the Tongbomiao Formation is made of variegated-glutenite braided river deposits with thin coal interbeds [33,34,37]. The siderite beds are concentrated in K1n1, and a small number of siderite beds are present in K1n2 and the first member of the Damoguaihe Formation (K1d1). The results of regional sedimentary studies show that both the steep and gentle slopes of the Dongming sag receive abundant supply from the source area. The tectonic subsidence of K1n1 was intense during the depositional period. Fan delta deposits developed in the southern steep slope zone, braided river delta deposits developed in the northern gentle slope zone, littoral shallow–semi-deep lacustrine deposits developed in the center of the lake basin, and sub-lacustrine fans developed locally. The strong tectonic subsidence led to the rise of the lake level. During this period, shore shallow lake semi-deep lake dark mudstone was deposited, which is the main source rock in the study area. K1n1 in well MD2 is mainly made up of thick black-dark gray mudstone, containing sandstone, and siltstone bands with varying thicknesses.

3. Samples and Methods

In this study, gray-dark gray mudstone and gray-black silty mudstone cores and detrital samples were sampled in the Dongming sag. In total, 23 samples were subjected to total organic carbon determination, rock-eval analysis, Ro determination, and kerogen microcomponent analysis (Table 1). This experimental analysis was performed by the laboratory of the Institute of Organic Geochemistry, PetroChina Daqing Oilfield Co., Ltd., Daqing, China.
In addition, based on the observation of the whole-well core of well MD2, fresh core samples were collected from dark mudstone and siderite beds of the well in K1n1 for systematic analysis of carbonate content, X-ray diffraction, major and trace element analysis, carbon and oxygen isotope analysis, thin-section analysis, scanning electron microscopy (SEM), cathodoluminescence, and energy-dispersive spectroscopy. Specifically, thin-section analysis and core description were used to observe the macromorphological and micromorphological characteristics of siderite. Elemental analysis and carbon and oxygen isotope analysis were used to identify the depositional paleoenvironment of the source rocks and siderite beds in K1n1. The above experimental analyses were all performed by the State Key Laboratory of Oil and Gas Reservoir Geology and Development, Chengdu University of Technology.

4. Experimental Results

4.1. Macroscopic Development Characteristics of Siderite Beds

Based on the core observation of well MD2, there are 23 siderite beds in the dark mudstone of K1n1, including 20 yellow-brown beds and 3 gray-brown beds (Figure 2a). From the logging curve, the anomalous values of the lower peak value in both GR and AC, but higher peak value in LLD are observed, which is the result of siderite enrichment. The macroscopic appearance of the siderite beds is similar to that of the mudstone beds, but the density of siderite is significantly higher than that of the surrounding mudstone. The thickness of a single siderite bed varies from 2 to 60 cm, and the cumulative thickness of siderite bed reaches 3.45 m. Dropping cold hydrochloric acid onto a siderite bed does not cause bubbling. The siderites in the mudstone are mostly irregular blocks, with a long axis almost parallel to the stratum and clear boundaries with the overlying and underlying surrounding rocks. Some siderites are lenticular, lamellar, or nodular, with unclear boundaries with the surrounding rocks (Figure 2b,d). Fractures filled with white bentonite can be observed in some siderite beds (Figure 2c). The characteristics of the siderite give important hints about its genetic mechanism, and stratiform or massive occurrence can be used as one of the hallmarks of authigenic siderite [4]. In addition, 10 well-stratified thin layers of tuff were observed in well MD2 (Figure 2e), with thicknesses ranging from 4 mm to 2 cm. These tuff layers coincide well with the strong regional volcanic activity during the depositional period of the K1n1 of the Hailar Basin [38]. After the Early Jurassic (approximately 197 Ma), northeast China was in an extensional tectonic environment (mantle uplift, crust extension, and thinning) and had a high-temperature geological background (created by strong magmatic activity) due to the subduction of the Kura-Pacific plate and the extension and closure of the Okhotsk–Mohe–Mongolian Ocean [39]. During the Early Cretaceous, there were two periods of volcanism in the Hailar Basin: from the Late Jurassic to the early Early Cretaceous (152–138 Ma) and in the late Early Cretaceous (128–117 Ma) [40], depositing mainly rhyolite-fused tuff, sedimentary breccia, and sedimentary tuff, followed by tuffaceous conglomerate and sandstone, and a small amount of andesite and andesitic tuff [41].

4.2. Micromorphological Characteristics of the Siderite Beds

The thin-section analysis and cathodoluminescence results of samples collected from well MD2 show that siderite appears yellow-brown under plane-polarized light and brown under cross-polarized light. According to its micromorphological characteristics, siderite can be divided into three occurrence forms: (1) dense micronized crystals with distinct crystal grains and associated calcite (Figure 3a); (2) banded distribution, two veins of calcite and siderite, and good stratification (Figure 3b); (3) paragenesis with quartz and calcite, an obvious Maltese-cross extinction pattern under cross-polarized light, and terrestrial plant debris observable under the microscope (Figure 3c,d). Under the SEM, clay mineral aggregates, charcoal, algal fossils, granular pyrite crystals, silicate bands, and other mineral types are observed in the siderite samples, which are intercalated with feldspar crystals, schistose mica, book-like kaolinite, and a few micropores (Figure 4).

4.3. Petromineralogical Characteristics of Siderite Beds

To further understand the mineral composition of the deposits of K1n1, a total of 20 samples were collected from the mudstone, siltstone, sandy conglomerate, and siderite beds for X-ray diffraction analysis (Table 2). In addition to quartz, feldspar, and clay minerals, all mudstone samples collected from K1n1 contain 2% to 10% siderite. The siltstone and sandy conglomerate samples do not contain siderite. The siderite samples have siderite as a main mineral component (content: 10% to 62%), followed by clay minerals, quartz, and feldspar, and two siderite samples are quartz-free (Figure 5a). Hou et al. [40] analyzed the minerals in K1n1 in well MD2 and noted that the content of siderite in some beds reached 90% and that some samples contained a small amount of ankerite and pyrite.

4.4. Characteristics of Main and Trace Elements

The contents and related parameters of major and trace elements are shown in Table 3 and Table 4. Major elements can be used to judge the original sedimentary fabric and the allochem percentage in sedimentary grains [42]. The oxides in the siderite beds in well MD2 include Fe2O3 (highest proportion, 14.33% to 57.67%; mean: 43.79%), SiO2, Al2O3, and oxides of Ca, Na, K, and Mg (generally less than 1%). The dark mudstone mainly consists of SiO2 and Al2O3 and generally contains less than 5% other oxides. The trace elements in the siderite beds are typically characterized by high Mn contents (which exceed 10,000 μg/g in all but one sample). Because Mn has a tendency to be enriched in the mudstone, it is hypothesized that the same depositional period brought an adequate supply of Mn from terrestrial sources of debris, along with a stronger solubility in reducing waters. In addition, besides the Be content in siderite beds being slightly higher than that of dark mudstone, the contents of other elements in siderite beds are equivalent to or slightly lower than that of dark mudstone. Be is a high-temperature mineralizing element, and its enrichment has good mineralization specificity with igneous rocks. Due to the background of volcanic activity, Be enrichment is thought to be related to volcanism.

4.5. Characteristics of Carbon and Oxygen Isotopes

Table 5 shows the results of carbon and oxygen isotopes measured in this study. The carbonate minerals in the siderite beds are enriched with heavy carbon isotopes. The range of δ13Cv-PDB (−0.20–1.11‰; mean: 0.62‰) is narrow, while the range of δ18Ov-PDB (−18.22‰ to −10.14‰; mean: −14.23‰) is wide. Compared with the siderite beds, the dark mudstone exhibits lighter carbon isotopic compositions (−1.98 to −3.28‰) and heavier oxygen isotopic compositions (−7.59 to −10.25‰).

5. Discussion

5.1. Restoration of the Paleoenvironment during the Depositional Period of K1n1

Sr and Ba contents and Sr/Ba ratios can be used to qualitatively reflect paleosalinity [42,43,44,45,46,47]. Generally, the concentration of Sr in saltwater is 800–1000 μg/g, and the concentration of Sr in fresh water is 100–300 μg/g. Sr/Ba > 1.0 indicates a saltwater (marine, saline lacustrine) medium; Sr/Ba < 0.6 indicates a terrestrial freshwater medium; and Sr/Ba between 0.6 and 1.0 indicates transitional brackish water deposits [46,47]. The Sr/Ba ratios of the siderite beds in well MD2 are 0.21–0.40 (mean: 0.29), and the Sr/Ba ratios of the dark mudstone are 0.28–0.38 (mean: 0.34). This suggests that the water in the lake basin was fresh water during the depositional period of K1n1.
As a redox-sensitive element, Ni is often precipitated in the form of sulfide under anoxic conditions and dissolved under oxidative conditions [44,46,48]. Elements such as U, V, and Cr in the depositional environment are easily soluble in oxidative conditions, insoluble in reducing environments, authigenically enriched in oxygen-deficient environments, and hardly migratable during diagenesis [38]. Th/U > 1.30 and V/Cr > 4.25 indicate a strong reducing environment, 0.8 < Th/U < 1.30 and 2.00 < V/Cr < 4.25 indicate a weak reducing environment, and Th/U < 0.8 and V/Cr < 2 indicate an oxidizing environment. The Th/U and V/Cr ratios of the siderite beds in well MD2 range from 3.25 to 6.25 (mean: 4.13) and from 0.99 to 4.85 (mean: 2.85), respectively. The Th/U and V/Cr ratios of dark mudstone range from 3.07 and 4.18 (mean: 3.84) and from 1.18 to 3.74 (mean: 2.92), respectively. Both the Th/U and V/Cr ratios of the two types of rocks indicate a reducing environment.
Under relatively stable tectonic conditions, climatic conditions control the temperature, pH, and paleosalinity of the depositional environment [47]. In this study, the chemical index of alteration (CIA) was used to judge the degree of chemical weathering and paleoclimate in the source area [47]. A CIA value between 50 and 65 (50 < CIA < 65) indicates weak chemical alteration, a CIA value between 65 and 85 (65 < CIA < 85) indicates moderate chemical alteration, and a CIA value between 85 and 100 (85 < CIA < 100) indicates strong chemical alteration:
CIA = 100 × Al2O3/(Al2O3 + CaO* + Na2O + K2O)
The CIA values of the siderite beds in well MD2 range from 64.50 to 79.42 (mean: 74.20), and the CIA values of the dark mudstone range from 54.72 to 87.10 (mean: 76.05). These results indicate that the chemical weathering during this period was moderate to strong and that the climate was semiarid to humid.
The Al/Ti ratios of the siderite beds and dark mudstone are both low, ranging from 0.20 to 0.34. Low Al/Ti ratios may indicate the input of a large amount of terrigenous detritus into the water bodies in the lake basin from faraway sources and the lake basin overall being in a relatively deep-water environment. In addition, the fractures developed in the siderite beds are filled with white bentonite. The magnesium-rich alkaline medium is an indispensable condition for the generation and maintenance of bentonite, whereas the exogenous alkaline medium, the warm and humid paleoclimate, and the formation of humic acid due to mass reproduction of plants cause silicate minerals (feldspar, mica, etc.) to release alkali metal ions, resulting in a weakly alkaline aqueous medium [49]. Therefore, the presence of bentonite reflects the warm and humid paleoclimate at that time.
In summary, the deposits of K1n1 were formed in the depositional environment of a freshwater lake basin with deep water bodies.

5.2. Characteristics of Carbon and Oxygen Isotopes in Siderite Beds and Identification of Carbon Sources

Theoretically, enough Fe2+ and CO32− is the prerequisite for siderite formation. The δ13Cv-PDB values of terrestrial lacustrine organic matter in Cretaceous or older sediments are approximately −25‰ to −24‰ [49], and the δ13Cv-PDB values of atmospheric freshwater, atmospheric CO2, and carbonate deposits are −4‰ to −1‰, approximately −7‰, and approximately 0‰, respectively [24,49]. The δ18Ov-PDB values of natural oxygen compounds, atmospheric O2, and atmospheric CO2 are approximately −55‰ to −11‰, −25‰ to −22‰, and −42‰ to −40‰, respectively. The oxygen isotope compositions of water in lakes (δ18Owater) are mainly controlled by local precipitation from both rain and snowfall, inflowing water from both rivers and groundwater, and evaporation [50,51]. The δ18O of precipitating carbonates depends on the temperature of formation and the isotopic composition of the water. The δ18O value has a positive dependence of approximately 0.28‰/°C [52]. Relatively light oxygen isotopic compositions indicate freshwater characteristics. Compared with the dark mudstone, the siderite beds in the deposits of K1n1 have a distinct heavy carbon isotopic composition, which is similar to that of lacustrine carbonate (Figure 6) and is hardly affected by the HCO3- released by organic matter degradation. These findings indicate that the siderite beds formed in a deep-water, strongly reducing environment. The sources of CO2 in crustal fluids include sedimentary organic matter, carbonates, and magma–mantle [46]. There are two main sources of organic carbon in lacustrine sediments: one is the terrestrial organic debris brought by water flowing into lake basins, and the other is the aquatic organisms in lakes. K1n1 is composed of thick, dark mudstone beds deposited against the background of a lake level rise. In addition, the atmospheric CO2 concentration was high during the depositional period, which dissolved in lake water to form HCO3, making for a CO2 (atmosphere)–HCO3 (solution)/CO32− (carbonate) homeostasis system. According to the carbon and oxygen isotopic characteristics of the siderite beds in the study area, the source of CO32− for the formation of siderite might be mainly related to the dissolution of authigenic carbonates in the basin and the exchange of CO2 between the atmosphere and lake water.

5.3. Genetic Mechanism of Siderite

Xie et al. [4] believed that stratiform or massive siderites may be authigenic or early-diagenetic. The siderite beds in the study area have a carbon isotopic composition close to that of the lacustrine carbonates, which is not affected by the degradation of sedimentary organic matter, so the siderite in the first member of the Lower Cretaceous Nantun Formation (K1n1) of the Dongming sag, Hailar Basin, was authigenic in a deep-water lacustrine reducing environment. The Cretaceous was one of the typical greenhouse periods in geological history, in which the paleoclimate strongly controlled the development and distribution of paleontological groups and sediment types [18,19,53]. Notably, the Early Cretaceous was in a process of overall warming, the temperature peaking in the mid-Cretaceous. The Cretaceous greenhouse climate might be closely related to the high atmospheric CO2 concentrations [53,54,55], which were 2 to 4 times higher than the current atmospheric CO2 concentrations [53], and the temperature at that time was higher than the current temperature [54,55,56,57]. As an important environmental indicator mineral, siderite is usually formed in closed and anoxic lacustrine environments with relatively weak hydrodynamic conditions. The provenance of the Dongming sag in the Hailar Basin mainly comes from the southern steep slope and the northern gentle slope zone. The northern gentle slope zone has developed braided river delta deposits, with inputs of terrigenous detritus from faraway sources. During transportation, its Fe was oxidized to Fe3+ by weathering, then transported through surface runoff and rivers, enriched in lake areas with weak hydrodynamics, and buried in the form of Fe(OH)3 along with the organic matter deposited on the bottom of the lake. The warm and humid climate was suitable for plant growth, the vegetation around the lake basin was prosperous, and a large amount of greenhouse gases such as CO2 were dissolved in lake water, which further promoted chemical weathering. The increased supply of various mineral elements accelerated the formation of authigenic minerals. Furthermore, during the depositional period of K1n1, the lake basin subsided rapidly, and the lake water level rose continuously. The warm lake water was conducive to the growth of organisms and the decay of organic matter, resulting in a sharp increase in oxygen consumed by the lake. After the volcanic eruption, the ash fell in the lake basin, which had the effect of increasing nutrients, not only made the microorganisms in the water body grow wildly in a short period of time, but also increased the salinity of the water body, resulting in the formation of stratification of the water body and bottom reduction environment [58,59]. The increased oxygen consumption and the anoxic water environment jointly promoted the formation of the reducing lacustrine environment. When the supply of Fe3+ is high enough, organic matter reduces Fe3+ to Fe2+, and the dissolution of carbonate and atmospheric CO2 can provide abundant CO32− for the formation of siderite. Under these conditions, Fe2+ combines with CO32− to form siderite (Figure 7).

5.4. Discussion on the Relationship between Siderite and Source Rocks

The geochemical analysis of the source rocks in K1n1 of the study area showed that the total organic carbon of the mud-source rocks of K1n1 is 0.93% to 6.70% (mean: 2.61%). The potential of hydrocarbon generation (S1 + S2) is 0.27 to 13.07 mg/g (mean: 4.57 mg/g). The kerogen is mainly of type II [58]. Microscopic examination showed algal fossils, sporophyte fossils, and vitrinites. The hydrocarbon source material is mainly from terrestrial higher plants. According to the Geochemistry Evaluation Method for Land Facies Hydrocarbon Source Rock (SY/T 5735-1995), this set of source rocks has high organic matter abundance and high hydrocarbon generation potential. The conventional geochemical characteristics and the depositional paleoenvironment indicated by the siderite evince excellent organic matter storage conditions and high hydrocarbon generation potential. Zhang et al. [33,34] concluded that the presence of siderite can promote the pyrolysis of organic matter in source rocks by increasing the pyrolysis rate and decreasing the temperature at which most organic matter is pyrolyzed by reducing the activation energy of the pyrolysis of organic matter. Compared with the source rocks with no siderite deposits in the Hongqi and Yimin sags of the Hailar Basin, the source rocks in K1n1 of the Dongming sag in the study area have higher main frequency activation energy to generate liquid hydrocarbons [60]. Preliminary analysis suggested that this may be related to the selection of kerogen samples for the simulation of hydrocarbon generation kinetics without considering the influence of mineral components such as siderite on the kerogen.

5.5. Recommendation for Future

Therefore, regarding the relationship between siderite and source rocks in the study area, there are still three issues that need to be studied and explored in depth. First, thin layers of tuff were found in the dark mudstone in the study area, but whether regional volcanic activity was involved in the formation of siderite beds, that is, whether the source of Fe in siderite was related to magma, needs further confirmation. Second, since the diagenesis related to the complex process of siderite formation occurs at the same temperature as the transformation temperature of organic matter into hydrocarbons [34,35,36], siderite has a certain influence on the process, stage, mechanism, and scale of hydrocarbon generation. However, the underlying mechanism needs further theoretical exploration. Third, regional comparative studies are needed to clarify whether there are differences in the hydrocarbon generation potential and evolution of source rocks with and without siderite and whether the presence of siderite can be used as a sign of the presence of high-quality source rocks.

6. Conclusions

  • The siderites in K1n1 are mostly stratiform or massive in the cores. There are three micromorphological features: dense micronized crystals, bands, and paragenesis with quartz and calcite, respectively. As the main mineral, the content of siderite exceeds 50%, followed by clay minerals, quartz, and feldspar. Under the microscope, a variety of mineral types, such as charcoal, algal fossils, granular pyrite crystals, and vein-like siliceous bands, were observed, which were intercalated with feldspar crystals, schistose mica, book-like kaolinite, and a small number of micropores.
  • The oxides in the siderite beds include Fe2O3 (highest proportion), SiO2, Al2O3, etc. The trace elements were characterized by a high Mn and Be contents; low Sr/Ba, Th/U, and Al/Ti ratios; and high V/Cr ratios. This indicates that the study area was a semiarid–humid, weakly reducing, freshwater depositional paleoenvironment during the depositional period of K1n1.
  • The siderite has distinct characteristics of heavy carbon and light oxygen isotopic compositions, which are similar to the characteristics of carbon and oxygen isotopes of lacustrine carbonate and atmospheric CO2. Hence, the carbon required for siderite formation mainly came from dissolution of carbonates and atmospheric CO2.
  • In the dynamic equilibrium system of CO2 (atmosphere) and HCO3 (solution)/CO32− (carbonate) in water bodies of the lake basin, the Fe supplied by the source area underwent physical and chemical weathering. When the resultant Fe2+ concentration reached saturation, authigenic siderite was formed when Fe2+ combined with CO32−.

Author Contributions

Conceptualization, M.X. and F.M.; methodology, M.X., G.C. and C.Z.; validation, M.X., G.C. and C.Z.; formal analysis, M.X.; investigation, X.Z.; data curation, R.X.; writing—original draft preparation, M.X.; writing—review and editing, M.X. and X.Z.; supervision, C.Z.; project administration, F.M. All authors have read and agreed to the published version of the manuscript.


This work was supported by the National Natural Science Foundation of China [grant number 42072119]; and Science and Technology Project of PetroChina [grant number 101017kt1604003x20].

Data Availability Statement

The authors confirm that the data supporting the findings of this study are available within the article.


The authors are indebted to all reviewers for their insightful comments and suggestions, which have significantly improved the manuscript. The authors are very grateful to Daqing Oilfield Exploration and Development Research Institute, PetroChina, for their data support.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Ohmoto, H.; Watanabe, Y.; Kumazawa, K. Evidence from massive siderite beds for a CO2-rich atmosphere before ~1.8 billion years ago. Nature 2004, 429, 395–399. [Google Scholar] [CrossRef] [PubMed]
  2. Bekker, A.; Slack, J.F.; Planavsky, N.; Krapez, B.; Hofmann, A.; Konhauser, K.O.; Rouxel, O.J. Iron formation: The sedimentary product of a complex interplay among mantle, tectonic, oceanic, and biospheric processes. Econ. Geol. 2010, 105, 467–508. [Google Scholar] [CrossRef] [Green Version]
  3. Wittkop, C.; Teranes, J.; Lubenow, B.; Dean, W.E. Carbon- and oxygen-stable isotopic signatures of methanogenesis, temperature, and water column stratification in Holocene siderite varves. Chem. Geol. 2014, 389, 153–166. [Google Scholar] [CrossRef]
  4. Xie, B.Z.; Sun, L.F.; Fang, H.; Shi, X.Y.; Tang, D.J. Siderite in banded iron formation of the Neoarchean Baizhiyan Formation, Shanxi Province: Genesis and palaeoenvironmental implications. J. Palaeogeogr. 2021, 23, 175–190. [Google Scholar] [CrossRef]
  5. Frederichs, A.T.; Dobeneck, T.V.; Bleil, U.; Dekkers, M.J. Towards the identification of siderite, rhodochrosite, and vivianite in sediments by their low-temperature magnetic properties. Phys. Chem. Earth Parts A/B/C 2003, 28, 669–679. [Google Scholar] [CrossRef]
  6. Dill, H.G. The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium. Earth-Sci. Rev. 2010, 100, 1–420. [Google Scholar] [CrossRef]
  7. Ward, C.R. Analysis and significance of mineral matter in coal seams. Int. J. Coal Geol. 2002, 50, 135–168. [Google Scholar] [CrossRef]
  8. Ward, C.R. Analysis, origin and significance of mineral matter in coal: An updated review. Int. J. Coal Geol. 2016, 165, 1–27. [Google Scholar] [CrossRef]
  9. Johnson, C.M.; Ludois, L.M.; Beard, B.L.; Beukes, N.J.; Heimann, A. Iron formation carbonates: Paleoceanographic proxy or recorder of microbial diagenesis? Geology 2013, 41, 1147–1150. [Google Scholar] [CrossRef] [Green Version]
  10. Köhler, I.; Konhauser, K.O.; Papineau, D.; Bekker, A.; Kappler, A. Biological carbon precursor to diagenetic siderite with spherical structures in iron formations. Nat. Commun. 2013, 4, 1741. [Google Scholar] [CrossRef] [Green Version]
  11. Zhang, K.; Zhu, X.K. Genesis of siderites in the Xiamaling formation of Jixian section and its paleoceanic significance. Acta Geol. Sin. 2013, 87, 1430–1438. [Google Scholar]
  12. Milesi, V.; Guyot, F.; Brunet, F.; Richard, L.; Recham, N.; Benedetti, M.; Dairou, J.; Prinzhofer, A. Formation of CO2, H2 and condensed carbon from siderite dissolution in the 200–300 °C range and at 50MPa. Geochim. Cosmochim. Acta 2015, 154, 201–211. [Google Scholar] [CrossRef]
  13. Milesi, V.; Prinzhofer, A.; Guyot, F.; Benedetti, M.; Rodrigues, R. Contribution of siderite–water interaction for the unconventional generation of hydrocarbon gases in the Solimões basin, north-west Brazil. Mar. Pet. Geol. 2016, 71, 168–182. [Google Scholar] [CrossRef]
  14. Wang, N.; Dai, S.; Nechaev, V.P.; French, D.; Graham, I.T.; Zhao, F.; Zuo, J. Isotopes of carbon and oxygen of siderite and their genetic indications for the Late Permian critical-metal tuffaceous deposits (Nb-Zr-REY-Ga) from Yunnan, southwestern China. Chem. Geol. 2022, 592, 120727. [Google Scholar] [CrossRef]
  15. Tu, G. Collection of Tu Guangchi’s Academic Works; Science Press: Beijing, China, 2010. [Google Scholar]
  16. Zhang, Y.J.; Shen, Y.L.; Yang, T.Y.; Zhao, Y.; Tong, G.C. Development characteristics of siderite in the constraint of sequence frame: A case study of Late Permian coal measures in Panguan area. J. China Coal Soc. 2020, 45, 976–985. [Google Scholar] [CrossRef]
  17. Chen, Z.; Yu, J.; Hou, K. Genesis of siderite in Xuanlong area in northwest Hebei province. Chin. J. Geol. 1982, 17, 395–402. [Google Scholar]
  18. Liu, J.; Liu, J.; Gu, X. Basin fluids and their related ore deposits. Acta Petrol. Mineral. 1997, 16, 54–65. [Google Scholar]
  19. Liu, M.; Chen, Z.; Chen, Q. The role of organic matter in the genesis of siderite from the Xuanlong area. Acta Sedimentol. Sin. 1997, 15, 98–104. [Google Scholar] [CrossRef]
  20. Dill, H.G. A geological and mineralogical review of clay mineral deposits and phyllosilicate ore guides in Central Europe—A function of geodynamics and climate change. Ore Geol. Rev. 2020, 119, 103304. [Google Scholar] [CrossRef]
  21. Siehl, A.; Thein, I. Minette-type ironstones. Br. Geol. Soc. Spec. Publ. 1989, 46, 175–193. [Google Scholar] [CrossRef]
  22. Burkhalter, R.M. Ooidal ironstones and ferruginous microbialites: Origin and relation to sequence stratigraphy (Aalenian and Bajocian, Swiss Jura mountains). Sedimentology 1995, 42, 57–74. [Google Scholar] [CrossRef]
  23. Santelli, C.M.; Welch, S.A.; Westrich, H.R.; Banfield, J.F. The effect of Fe-oxidizing bacteria on Fe-silicate mineral dissolution. Chem. Geol. 2001, 180, 99–115. [Google Scholar] [CrossRef]
  24. Shen, Y.; Qin, Y.; Li, Z.; Jin, J.; Wei, Z.H.; Zheng, J.; Zhang, T.; Zong, Y.; Wang, X. The sedimentary origin and geological significance of siderite in the Longtan Formation of western Guizhou Province. Earth Sci. Front. 2017, 24, 152–161. [Google Scholar] [CrossRef]
  25. Yang, X.; Zhang, X. The genesis of Ediacaran siderite-rich iron formations in North Qilian, and its constraints on ancient oceanic conditions. Chin. Sci. Bull. 2021, 66, 3032–3044. [Google Scholar] [CrossRef]
  26. Huang, Y.; Wang, C. Progress of reactive iron burial in the marine and terrestrial sediments with its implications to the genesis of source rock in Songliao Basin. Chin. J. Nat. 2015, 37, 79–85. [Google Scholar]
  27. Tannenbaum, E.; Kaplan, I.R. Low-Mr hydrocarbons generated during hydrous and dry pyrolysis of kerogen. Nature 1985, 317, 708–709. [Google Scholar] [CrossRef] [PubMed]
  28. Tannenbaum, E.; Huizinga, B.J.; Kaplan, I.R. Role of minerals in thermal alteration of organic matter-II: A material balances. AAPG Bull. 1986, 70, 1156–1165. [Google Scholar] [CrossRef]
  29. Zhao, W.Z.; Wang, Z.Y.; Wang, H.J.; Zecheng, W.; Shuichang, Z.; Wang, Z.; Zhang, Q.C. Cracking conditions of oils existing in different modes of occurrence and forward and backward inference of gas source rock kitchen of oil cracking type. Geol. China 2006, 33, 952–965. [Google Scholar]
  30. Cai, Y.; Zhang, S.; He, K.; Mi, J.; Zhang, W.; Wang, X.; Wang, H.; Wu, C. Effects of inorganic minerals in source rocks on hydrocarbon generation from organic matter. Pet. Geol. Exp. 2017, 39, 253–260. [Google Scholar] [CrossRef]
  31. Jin, Z.; Yuan, G.; Cao, Y.; Liu, K.; Wang, Y.; Sun, J.; Hao, X.; Zhou, L.; Wei, Y.; Wu, S. Interactions between hydrocarbon-bearing fluids and calcite in fused silica capillary capsules and geological implications for deeply-buried hydrocarbon reservoirs. Sci. China Earth Sci. 2022, 65, 299–316. [Google Scholar] [CrossRef]
  32. Nigam, A.N.; Tripathi, R.P.; Singh, H.S.; Gambhir, R.S. Source rock evaluation of some wells in Jaisalmer Basin (India) using Mössbauer spectroscopy. Fuel 1991, 70, 262–266. [Google Scholar] [CrossRef]
  33. Zhang, X.; Jia, Z.; Li, J.; Hou, Y.; Peng, W.; Zhang, H.; Chen, H.; Shen, W.; Liu, Z.; Chen, H. Controlling action of the tectonic evolution on the hydrocarbon accumulation in Hongqi Sag of Hailar Basin. Pet. Geol. Oilfield Dev. Daqing 2019, 38, 117–125. [Google Scholar] [CrossRef]
  34. Zhang, Y.; Zhou, S.; Li, J.; Ma, Y.; Li, Y.; Chen, K.; Zhang, C.; Sun, Z. Effect of siderite on pyrolysis of organic matters in source rocks. Geochimica 2019, 48, 502–510. [Google Scholar] [CrossRef]
  35. Meng, Q.A.; Wan, C.B.; Zhu, D.F.; Zhang, Y.L.; Ge, W.C.; Wu, F.Y. Age assignment and geological significance of the “Budate Group” in the Hailar Basin. Sci. China Earth Sci. 2013, 56, 970–979. [Google Scholar] [CrossRef]
  36. Feng, Z.; Zhang, X.; Ren, Y.; Wu, H.; Li, C.; Dong, W. Hydrocarbon reservoir forming characteristics and distribution rule of Hailar Basin. Pet. Geol. Oilfield Dev. Daqing 2004, 23, 16–19. [Google Scholar]
  37. Chen, G.; Li, J.; Wu, H.; Peng, W.; Li, J.; Xie, M.; Zhang, B.; Shi, X. Sedimentary characteristics, identification mark and formation mechanism of the slumping deepwater gravity flow in fault lacustrine basin: A case study on the consecutive coring Well of Ming D2 in Dongming sag, Hailar Basin. Acta Pet. Sin. 2018, 39, 1119–1129. [Google Scholar]
  38. Hou, Y.; Ren, Y.; Li, S.; Zhang, H.; Wu, H.; Peng, W.; Li, J. Analysis of Cretaceous sedimentary characteristics and environment from well MD2 in Dongming depression, Hailar Basin. Glob. Geol. 2020, 39, 332–343. [Google Scholar]
  39. Cui, J.; Zhao, J.; Ren, Z.; Jin, W.; Xing, L.; Wang, Y. Geochemical characteristics of lower cretaceous source rocks and thermal history in the Huhehu Depression, Hailar Basin. Earth Sci. 2020, 45, 238–250. [Google Scholar]
  40. Chen, C.; Gao, Y.; Wu, H.; Qu, X.; Liu, Z.; Bai, X.; Wang, P. Zircon U-Pb chronology of volcanic rocks in the Hailar basin, NE China and its geological implications. Earth Sci. 2016, 41, 1259–1274. [Google Scholar]
  41. Wang, H.; Liu, L.; Gao, Y.; Zhang, X. Discussion of diageneses of volcaniclastic rocks of Nantun Formationin Beier sags, Hailar Basin. Glob. Geol. 2005, 24, 219–224. [Google Scholar]
  42. Fan, Q.; Fan, T.; Li, Y.; Zhang, J.; Gao, Z.; Chen, Y. Paleo-environments and development pattern of high-quality marine source rocks of the early Cambrian, Northern Tarim platform. Earth Sci. 2020, 45, 285–302. [Google Scholar] [CrossRef]
  43. Deng, H.; Qian, K. Sedimentary Geochemistry and Environmental Analysis; Gansu Science and Technology Press: Lanzhou, China, 1993. [Google Scholar]
  44. Tribovillard, N.; Algeo, T.J.; Lyons, T.; Riboulleau, A. Trace metals as paleoredox and paleoproductivity proxies: An update. Chem. Geol. 2006, 232, 12–32. [Google Scholar] [CrossRef]
  45. Cao, H.; Hu, J.; Xi, D.; Peng, P.; Lei, Y. Geochemical characteristics of hydrocarbon source rock and paleoenvironment reconstruction in Houjingouprofile of Songliao Basin. Acta Sedimentol. Sin. 2015, 33, 1043–1052. [Google Scholar]
  46. Zhang, T.; Sun, L.; Zhang, Y.; Cheng, Y.; Li, Y.; Ma, H.; Lu, C.; Yang, C.; Guo, G. Geochemical characteristics of the Jurassic Yan’an and Zhiluo formations in the Northern margin of Ordos basin and their paleoenvironment implications. Acta Geol. Sin. 2016, 90, 3454–3472. [Google Scholar]
  47. Shi, J.; Zou, Y.; Yu, J.; Liu, J. Paleoenvironment of organic-rich shale from the Lucaogou formation in the Fukang sag, Junggar basin, China. Nat. Gas Geosci. 2018, 29, 1138–1150. [Google Scholar]
  48. Algeo, T.J.; Maynard, J.B. Trace-element behavior and redox facies in core shales of Upper Pennsylvanian Kansas-type cyclothems. Chem. Geol. 2004, 206, 289–318. [Google Scholar] [CrossRef]
  49. Xiang, F.; Song, J.; Luo, L.; Tian, X. Distribution characteristics and climate significance of continental special deposits in the Early Cretaceous. Earth Sci. Front. 2009, 16, 48–62. [Google Scholar]
  50. Talbot, M.R. A review of the palaeohydrological interpretation of carbon and oxygen isotopic ratios in primary lacustrine carbonates. Chem. Geol. Isot. Geosci. Sect. 1990, 80, 261–279. [Google Scholar] [CrossRef]
  51. Chivas, A.R.; De Deckker, P.; Cali, J.A.; Chapman, A.; Kiss, E.; Shelley, J.M.G. Coupled stable-isotope and trace-element measurements of lacustrine carbonates as paleoclimatic indicators. In Climate Change in Continental Isotopic Records; Swart, P.K., Lohmann, K.C., McKenzie, J., Savin, S., Eds.; American Geophysical Union: Washington, DC, USA, 1993; pp. 113–121. [Google Scholar]
  52. Rozanski, K.; Araguás-Araguás, L.; Gonfiantini, R. Isotopic patterns in modern global precipitation. In Climate Change in Continental Isotopic Records; Swart, P.K., Lohmann, K.C., Mckenzie, J., Savin, S., Eds.; American Geophysical Union: Washington, DC, USA, 1993; pp. 1–36. [Google Scholar]
  53. Xi, D.; Wan, X.; Li, G.; Li, G. Cretaceous integrative stratigraphy and timescale of China. Sci. China Earth Sci. 2019, 62, 256–286. [Google Scholar] [CrossRef]
  54. Huber, B.T.; Norris, R.D.; MacLeod, K.G. Deep-sea paleotemperature record of extreme warmth during the Cretaceous. Geology 2002, 30, 123–126. [Google Scholar] [CrossRef]
  55. Wang, Y.; Huang, C.; Sun, B.; Quan, C.; Wu, J.; Lin, Z. Paleo-CO2 variation trends and the Cretaceous greenhouse climate. Earth-Sci. Rev. 2014, 129, 136–147. [Google Scholar] [CrossRef]
  56. Sellwood, B.W.; Valdes, P.J. Mesozoic climates: General circulation models and the rock record. Sediment. Geol. 2006, 190, 269–287. [Google Scholar] [CrossRef]
  57. Hay, W.W. Toward understanding Cretaceous climate—An updated review. Sci. China Earth Sci. 2017, 60, 5–19. [Google Scholar] [CrossRef]
  58. Wu, H.; Ren, Y.; Li, J.; Liu, H.; Deng, H.; Zhang, H. Developed characteristics and genetic mechanism of high-quality source rocks in Wuerxun-Beier sags. Pet. Geol. Oilfield Dev. Daqing 2014, 33, 154–161. [Google Scholar]
  59. Xie, M.; Ma, F.; Chen, G. Petroleum generation kinetics and geological implications for Jurassic hydrocarbon sources rocks, Hongqi depression, Hailar basin, Norgheast China. Acta Geol. Sin. 2023, 97, 548–561. [Google Scholar] [CrossRef]
  60. Xie, M.; Chen, G.; Li, J.; Ma, F.; Song, X. Hydrocarbon generation kinetics of source rocks of the first member of Nantun Formation in peripheral sags of Hailar Basin. Lithol. Reserv. 2020, 32, 24–33. [Google Scholar]
Figure 1. Structural units (a) and the top structural map of the first member of the Nantun Formation (K1n1) of the Dongming sag (b), and synthetic histogram (c) of the Hailar Basin (modified from reference [33,34,35,36]).
Figure 1. Structural units (a) and the top structural map of the first member of the Nantun Formation (K1n1) of the Dongming sag (b), and synthetic histogram (c) of the Hailar Basin (modified from reference [33,34,35,36]).
Minerals 13 00804 g001aMinerals 13 00804 g001b
Figure 2. The stratigraphic profile of K1n1 in well MD2 and photographs of typical siderite and tuff cores. (a) stratigraphic profile of K1n1 in well MD2, including the location of (be); (b) lenticular siderite with unclear boundaries with the surrounding rocks; (c) fractures filled with white bentonite can be observed in some siderite beds; (d) layered siderite; (e) well-stratified thin layers of tuff.
Figure 2. The stratigraphic profile of K1n1 in well MD2 and photographs of typical siderite and tuff cores. (a) stratigraphic profile of K1n1 in well MD2, including the location of (be); (b) lenticular siderite with unclear boundaries with the surrounding rocks; (c) fractures filled with white bentonite can be observed in some siderite beds; (d) layered siderite; (e) well-stratified thin layers of tuff.
Minerals 13 00804 g002
Figure 3. Microscopic lithofacies characteristics of the siderite beds in K1n1 in well MD2: (a) micronized crystals; (b) stratiform occurrence, replacement of calcite by siderite; (c,d) paragenesis with quartz and calcite and the presence of plant debris. Qz = quartz, Sd = siderite, Cal = calcite, CL = cathodoluminescence, (+) = cross-polarized light, (−) = plane-polarized light.
Figure 3. Microscopic lithofacies characteristics of the siderite beds in K1n1 in well MD2: (a) micronized crystals; (b) stratiform occurrence, replacement of calcite by siderite; (c,d) paragenesis with quartz and calcite and the presence of plant debris. Qz = quartz, Sd = siderite, Cal = calcite, CL = cathodoluminescence, (+) = cross-polarized light, (−) = plane-polarized light.
Minerals 13 00804 g003
Figure 4. Mineral composition of the siderite beds in K1n1 in well MD2: (a) charcoal suspended in siderite; (b) algal fossils interspersed with platelet clay minerals; (d) granular pyrite crystals in banded distribution; (e) quartz veinlets; (g) feldspar crystals and micropores; (h) interbeds of schistose mica and book-like kaolinite; “+” in (b,e,h) is the location of energy-dispersive spectra; (c,f,i) energy-dispersive spectra.
Figure 4. Mineral composition of the siderite beds in K1n1 in well MD2: (a) charcoal suspended in siderite; (b) algal fossils interspersed with platelet clay minerals; (d) granular pyrite crystals in banded distribution; (e) quartz veinlets; (g) feldspar crystals and micropores; (h) interbeds of schistose mica and book-like kaolinite; “+” in (b,e,h) is the location of energy-dispersive spectra; (c,f,i) energy-dispersive spectra.
Minerals 13 00804 g004
Figure 5. Mineral content (a) and relative content of clay minerals (b) measured using X-ray diffraction for different lithologies in K1n1 in well MD2.
Figure 5. Mineral content (a) and relative content of clay minerals (b) measured using X-ray diffraction for different lithologies in K1n1 in well MD2.
Minerals 13 00804 g005
Figure 6. δ13Cv-PDB18Ov-PDB diagram of the carbonate minerals in well MD2.
Figure 6. δ13Cv-PDB18Ov-PDB diagram of the carbonate minerals in well MD2.
Minerals 13 00804 g006
Figure 7. Conceptual model of siderite formation in K1n1 of the Dongming sag.
Figure 7. Conceptual model of siderite formation in K1n1 of the Dongming sag.
Minerals 13 00804 g007
Table 1. TOC, Rock-Eval, and Ro data of the black mud and coal samples in Dongming Sag.
Table 1. TOC, Rock-Eval, and Ro data of the black mud and coal samples in Dongming Sag.
WellDepth/mSampleTOC/%Tmax/°C(S1 + S2)/(mg/g)Ro/%
M22780.00 Coal chips62.74 497.00 41.51 1.55
M31567.00 Coal chips62.04 440.00 120.95 0.79
M31587.00 Coal chips59.68 439.00 161.93 0.79
M31647.00 Coal chips64.56 438.00 190.24 0.80
M31750.00 Mud1.62 440.00 2.69 0.80
M31912.00 Coal chips65.20 404.00 29.90 0.80
M32248.00 Mud1.88 442.00 1.69 0.81
M32342.00 Mud3.96 439.00 2.43 0.81
M31452.43 Coal36.07 444.00 44.32 0.76
BD1510.85 Mud2.87 434.00 1.49 0.49
BD1548.75 Coal46.25 429.00 24.12 0.48
BD1700.70 Mud2.02 439.00 1.81 0.63
BD1744.60 Mud2.13 442.00 9.44 0.65
BD1779.85 Mud1.50 438.00 1.76 0.68
BD1818.45 Mud6.70 445.00 4.92 0.69
BD1873.20 Mud2.10 439.00 6.31 0.78
BD1909.60 Mud1.93 454.00 1.54 0.82
BD1970.15 Mud2.24 442.00 2.70 0.87
BD1990.35 Mud0.93 427.00 0.27 0.89
M1557.06 Mud2.48 429.00 2.45 0.46
M1977.78 Mud2.99 432.00 12.68 0.52
M11033.29 Mud3.35 433.00 13.07 0.52
M11425.39 Mud3.09 438.00 7.93 0.55
Table 2. Major element contents of the samples from well MD2.
Table 2. Major element contents of the samples from well MD2.
Sample IDLithDepth
Total Clay Content
Clay Minerals/%
Z38Black mud623.0013.00 8.00 25.00 3.00 51.00 12.00 43.00 29.00 16.00
Z37Siltstone623.5546.00 9.00 15.00 30.00 17.07 7.33
Z36Sandy conglomerate624.0548.00 10.00 19.00 23.00 68.00 30.00
Z35Sandy conglomerate624.3048.00 9.00 20.00 23.00 2.00 32.00
Z33Black mud625.6025.00 12.00 21.00 4.00 38.00 4.00 90.00 4.00 4.00
s12Black mud625.6023.00 8.00 18.00 2.00 49.00 12.00 41.00 30.00 17.00
ZB10Siderite626.75 22.00 6.00 53.00 19.00 2.00 89.00 7.00 2.00
s11Gray siltstone627.4529.00 12.00 22.00 37.00 8.00 63.00 17.00 12.00
Z31Black mud627.7018.00 10.00 20.00 2.00 50.00 32.00 40.00 23.00 5.00
Z30Siltstone628.0022.00 15.00 24.00 2.00 36.00 3.00 71.00 17.00 9.00
Z29Black mud629.0526.00 17.00 19.00 3.00 35.00 7.00 43.00 44.00 6.00
s10Black mud631.1025.00 15.00 19.00 3.00 38.00 5.00 70.00 13.00 12.00
s9Black mud634.7726.00 15.00 22.00 2.00 35.00 13.00 36.00 51.00
s41Black mud636.9724.00 18.00 20.00 2.00 36.00 2.00 77.00 11.00 10.00
ZB9Siderite640.00 22.00 6.00 50.00 22.00 6.00 70.00 19.00 5.00
s39Black mud640.1022.00 19.00 11.00 8.00 40.00 11.00 61.00 19.00 9.00
s40Black mud641.5722.00 20.00 24.00 10.00 34.00 1.00 89.00 6.00 4.00
ZB8Siderite647.4720.00 15.00 16.00 10.00 39.00 4.00 76.00 10.00 10.00
s38Black mud649.7023.00 13.00 21.00 4.00 39.00 7.00 58.00 23.00 12.00
ZB1Siderite703.4225.00 62.00 13.00 15.00 18.00 42.00 24.00
Table 3. Major element contents of the samples from well MD2.
Table 3. Major element contents of the samples from well MD2.
Sample IDLithElement Content/%
Z27Black mud6.188.3874.2513.92.22.462.830.561.2368.96
Z29Black mud5.045.8373.3515.810.791.625.130.491.6667.58
Z31Black mud12.6816.6155.9213.363.9214.563.170.941.7560.17
Z33Black mud7.358.5263.5620.
Z35Sandy conglomerate8.7310.0264.318.271.293.993.270.681.6674.59
Z36Sandy conglomerate5.5510.0176.813.674.462.054.820.422.0354.72
Z38Black mud8.689.9661.3820.141.282.932.370.821.978.39
s15Black mud12.2612.8853.0822.960.625.342.360.560.786.22
s14Sandy mudstone9.4010.2559.5322.420.853.172.740.70.8783.39
s1Black mud11.9412.6659.2318.890.723.051.980.710.9183.97
s3Black mud9.8310.9762.816.881.144.951.940.780.9480.77
s4Black mud9.0010.0166.6916.731.002.912.290.831.0479.43
s5Black mud9.1210.1567.5416.491.032.443.090.961.3875
s6Black mud8.639.2268.4715.860.591.912.560.681.1478.72
s8Black mud9.3910.1669.2713.780.772.
s10Black mud8.939.5465.5218.380.611.803.500.561.2177.56
s11Gray siltstone9.139.9663.5518.070.832.392.810.771.4977.88
s9Black mud9.5610.0165.0318.280.462.053.410.581.377.95
s13Black mud10.8911.5557.4421.530.663.121.750.540.7987.1
s28Black mud9.8311.5760.121.041.742.81.930.590.8782.26
s30Black mud9.6510.8364.3817.591.172.822.440.871.2678.32
s32Black mud8.549.0967.4216.230.552.762.270.661.0780.66
s34Black mud40.640.9243.356.60.320.750.840.190.4280.71
s36Gray mud8.949.8066.8316.10.862.363.090.861.3775.17
s29Black mud11.8812.4867.3911.730.603.202.400.640.9574.85
s31Black mud11.3814.9761.6516.833.594.051.590.71.1172.8
s35Black mud8.989.7566.2916.920.772.182.920.721.3976.89
s37Black mud10.0210.8765.0616.250.853.522.450.661.1278.61
s38Black mud8.489.1367.8714.910.642.282.570.731.376.74
s39Black mud29.6430.668.82.461.0255.610.210.480.1763.68
Note: Chemical index of alteration CIA = 100 × Al2O3/(Al2O3 + CaO + Na2O + K2O).
Table 4. Trace element contents of the samples from well MD2.
Table 4. Trace element contents of the samples from well MD2.
Sample IDLithElement Content/(10−6 μg·g−1)
ZB1Siderite26.51 5.24 2135.98 16.41 87.21 25.30 10,520.39 8.76 8.98 8.94 61.15 43.65 121.12 290.60 327.09 17.16 17.27 2.76
ZB2Siderite33.84 5.97 3294.97 10.03 83.73 33.72 7126.65 10.22 11.23 12.70 166.81 90.94 223.14 354.76 560.61 33.66 15.57 4.29
ZB3Siderite21.60 6.53 1482.99 6.13 100.35 20.69 16,159.48 6.25 6.84 4.55 43.22 40.48 106.35 212.80 376.61 12.09 6.57 1.98
ZB4Siderite13.55 5.61 781.79 4.13 50.15 23.96 24,242.81 3.77 4.95 4.57 63.12 17.62 63.87 97.49 260.73 6.77 4.06 0.90
ZB5Siderite13.28 1.63 646.49 2.63 15.90 16.00 44,902.11 1.78 3.85 7.48 13.77 12.85 60.82 78.48 259.40 2.12 3.09 0.76
ZB6Siderite11.71 8.74 490.80 4.93 72.20 20.87 24,762.04 2.03 3.73 3.74 21.11 9.04 45.77 82.59 165.28 10.85 3.20 0.67
ZB7Siderite16.35 6.55 1133.99 7.49 66.63 34.76 13,058.05 7.66 8.39 9.41 25.35 43.97 75.76 225.97 363.02 11.20 7.50 2.18
ZB8Siderite19.67 7.38 1459.99 5.54 61.67 22.62 17,625.92 6.68 8.04 5.62 52.84 31.25 91.78 225.40 289.46 15.18 7.29 2.25
ZB9Siderite11.35 3.86 614.29 3.01 29.83 23.55 20,802.19 1.83 3.81 4.92 23.21 12.45 108.90 99.08 339.61 8.86 3.74 0.96
s4Black mud41.71 3.59 3714.96 11.43 113.86 38.96 171.42 7.63 12.73 17.49 80.84 106.47 236.50 523.41 631.49 19.34 19.59 5.02
s5Black mud30.47 3.79 3186.97 13.09 112.77 36.32 139.90 9.45 14.30 19.74 51.58 143.32 197.75 491.49 599.69 23.46 20.18 4.95
s6Black mud36.98 3.42 3287.97 11.72 117.41 31.77 170.74 9.87 11.74 15.32 60.63 117.20 193.41 413.53 547.97 18.28 16.16 4.04
s11Gray siltstone35.71 3.35 4108.96 11.67 90.00 29.18 214.66 14.17 13.61 21.73 68.58 116.84 259.82 554.42 692.26 26.44 19.23 4.60
s28Black mud52.20 4.00 3548.97 14.20 100.79 28.14 261.89 12.05 12.88 14.37 88.98 99.33 268.99 613.34 573.70 29.75 25.00 5.40
s30Black mud42.11 4.02 4221.96 13.20 114.52 39.07 175.35 14.08 16.83 21.14 125.20 116.44 278.42 612.22 736.60 22.18 21.32 5.49
s32Black mud37.93 3.56 3616.96 11.73 106.22 28.36 404.67 11.55 12.80 16.73 70.80 111.72 212.41 493.06 654.18 20.23 17.75 4.73
s34Black mud24.67 5.10 1556.98 4.12 32.58 18.87 92.24 2.82 4.85 7.70 21.67 37.38 83.75 210.01 252.94 5.08 8.61 2.29
s36Gray mud36.81 3.60 3671.96 12.98 116.57 41.43 342.01 13.22 14.52 17.35 100.18 140.96 254.12 506.00 708.89 26.15 18.90 5.04
s29Black mud31.22 3.58 3020.97 10.59 145.08 39.44 135.86 20.99 19.71 21.06 123.71 122.30 155.16 409.50 553.41 26.70 16.21 5.28
s38Black mud33.54 3.19 3193.97 11.31 98.35 30.23 273.72 6.98 9.82 16.05 72.79 117.70 212.67 445.68 628.28 22.27 16.69 4.42
s39Black mud10.37 2.49 579.90 2.25 21.61 18.38 21,865.95 1.85 4.16 5.50 21.78 12.57 92.30 83.60 311.33 6.87 3.26 0.80
Table 5. Carbon and oxygen isotope data of the Mbr 1 of the Nantun formation from well MD2.
Table 5. Carbon and oxygen isotope data of the Mbr 1 of the Nantun formation from well MD2.
Sample IDLithDepth/mδ13C‰ (VPDB)δ18O‰ (VPDB)
Measured ValueStandard DeviationMeasured ValueStandard Deviation
Z27Black mud655.97−3.280.10−10.250.30
Z30Gray silty mudstone628.00−1.980.08−7.590.03
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Xie, M.; Ma, F.; Chen, G.; Zheng, X.; Xiao, R.; Zhang, C. Genesis and Geological Significance of Siderite in the First Member of the Nantun Formation of Dongming Sag, Hailar Basin. Minerals 2023, 13, 804.

AMA Style

Xie M, Ma F, Chen G, Zheng X, Xiao R, Zhang C. Genesis and Geological Significance of Siderite in the First Member of the Nantun Formation of Dongming Sag, Hailar Basin. Minerals. 2023; 13(6):804.

Chicago/Turabian Style

Xie, Mingxian, Feng Ma, Guangpo Chen, Xi Zheng, Rong Xiao, and Chengjun Zhang. 2023. "Genesis and Geological Significance of Siderite in the First Member of the Nantun Formation of Dongming Sag, Hailar Basin" Minerals 13, no. 6: 804.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop