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. 2021 Feb 25;11(1):4561.
doi: 10.1038/s41598-021-83415-6.

Palaeoenvironmental evolution of formation of Bayanjargalan oil shale: evidence from trace elements and biomarkers

Youhong Sun  1   2   3 , Demchig Tsolmon  1   2   3 , Xuanlong Shan  4 , Wentong He  1   2   3 , Wei Guo  5   6   7
Affiliations

Palaeoenvironmental evolution of formation of Bayanjargalan oil shale: evidence from trace elements and biomarkers

Youhong Sun et al. Sci Rep. .

Abstract

The genetic type of the Bayanerhet Formation oil shale in the Bayanjargalan mine area is an inland lacustrine oil shale deposit. Inorganic element analysis and organic geochemical testing of oil shale samples collected in three boreholes show that the Bayanerhet Formation oil shale has relatively high organic contents, e.g., average TOC values of 6.53, 7.32 and 8.84 (corresponding to oil contents of 5.49%, 6.07% and 7.50%) in boreholes BJ3807, BJ3405 and BJ3005, respectively. Analysis of organic matter sources with biomarkers indicates that lower aquatic organisms such as algae contribute more to the organic matter than higher plants do. According to research on the values of Fe2O3/FeO, Rb/Sr and w (La) n/w (Yb)n in cores from the three boreholes, the Bayanjargalan oil shale is inferred to have formed in a humid paleoclimate with a relatively high sedimentation rate. In research on the evolution of the paleoaquifer in which the oil shale formed, the values of Fe3+/Fe2+, V/V + Ni, Ni/V, Ceanom and δCe are applied as sensitive indicators of the redox conditions in the aqueous medium. These values indicate that the Bayanjargalan oil shale formed in a water body with a weak redox environment. Moreover, the values of Ca/(Ca + Fe) and Sr/Ba and the values of gammacerane/αβC30 hopane in biomarkers show that the oil shale was formed in a saltwater environment. Analysis of Mo and U shows high endogenous lake productivity, corresponding to high TOC, which suggests that the lacustrine productivity played an important role in organic matter enrichment. The Lower Cretaceous Bayanerhet Formation (K1bt) in the Bayanjargalan mine area encompasses a complete sequence and was formed during lowstand, transgression, highstand and regression periods. The dominant oil shale deposits were formed in the transgression system tract and high stand system tract, and these oil shales have a high oil content and stable occurrence. A large set of thick, high-TOC and high-oil-content oil shales in the second member of the Bayanerhet Formation was deposited under such conditions. The abundant terrigenous supply under warm and humid conditions significantly promoted the primitive biological productivity, and the weak redox saltwater environment had relatively high productivity. All the favorable conditions promoted the formation of high-quality oil shale.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Geological map of the Bayanjargalan Basin.
Figure 2
Figure 2
Stratigraphic subdivision of the Bayanjargalan Basin.
Figure 3
Figure 3
Total ion current.
Figure 4
Figure 4
MS with m/z = 217.
Figure 5
Figure 5
Mass spectrum of m/z = 191.
See this image and copyright information in PMC

References

    1. Jie Lu. Depositional characteristics of oil shale in the lower cretaceous Bayanerhet formations in Bayanjargalan Basin. South. Land Resour. 2012;10:25–26.
    1. Gromet LP, Dymek RF, Haskin LA, et al. The “North American Shale Composite”: Its compilation, major and trace element characteristics. Geochim. Cosmochim. Acta. 1984;48:2469–2482. doi: 10.1016/0016-7037(84)90298-9. - DOI
    1. Li J, Sang S, Lin H, et al. REE characteristics and its geological significance of the Permo-Carboniferous in Bohaiwan Basin. Acta Sedimentol. Sin. 2007;25(4):589–596.
    1. Bechtel A, Reischenbacher D, Sachsenhofer RF, Gratzer R, Lücke A, Püttmann W. Relations of petrographical and geochemical parameters in the middle Miocene Lavanttal lignite (Austria) Int. J. Coal Geol. 2007;70:325–349. doi: 10.1016/j.coal.2006.07.002. - DOI
    1. Bray EE, Evans ED. Distribution of n-paraffins as a clue to recognition ofsource beds. Geochim. Cosmochim. Acta. 1961;22:2–15. doi: 10.1016/0016-7037(61)90069-2. - DOI