Depositional Setting and Enrichment Mechanism of Organic Matter of Lower Cretaceous Shale in Ri-Qing-Wei Basin in the Central Sulu Orogenic Belt

Zhou, Tengfei; Zhou, Yaoqi; Zhao, Hanjie; Li, Manjie; Mu, Hongyu

doi:10.3389/feart.2021.808916

Cited by 10 publications

(8 citation statements)

References 39 publications

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“…Hence, an increase in the V/(V+Ni) ratio may be indicative of increased hypoxia. A V/Cr ratio of <2, 2-4.25, and >4.25 respectively denote an oxic environment, a dysoxic environment, and an anoxic environment (Rimmer, 2004;Zhou et al, 2018). The V/(V + Ni) values of the upper Qing1 Member were recorded between 0.67 and 0.89 (average: 0.77), indicating a weakly reducing environment.…”

Section: Paleoredox Conditionsmentioning

confidence: 99%

“…As the stratification of water bodies is mostly related to high salinity, the relative abundance of gammacerane indicates the salinity and stratification characteristics of sedimentary water bodies (Zhou et al, 2018). The gammacerane index (Ga/C 30 H) of the lower part of the Qing1 Member varied in a range of 0.22 and 0.65 (with an average of 0.45) and that of the upper part ranged between 0.11 and 0.42 (with an average of 0.25).…”

Section: Paleosalinity Conditionsmentioning

confidence: 99%

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Depositional environment variations and organic matter accumulation of the first member of the Qingshankou formation in the southern Songliao Basin, China

Ma,

Jinlai

2023

Front. Earth Sci.

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The organic-rich shale in the first member of the Qingshankou Formation, which is located in the southern Songliao Basin, is regarded as a high-quality source rock in East China. Geochemistry parameters were utilized to illustrate the formation and preservation conditions of the Qing1 Member in the Changling Sag, southern Songliao Basin. In the present study, from longitudinal continuity, the samples of organic geochemistry and elemental geochemistry were collected and systematically analyzed. This aims at determining the paleosalinity, paleoclimate, paleoredox conditions, and paleoproductivity and reconstructing its depositional paleoenvironment. According to total organic carbon (TOC) content, the Qing1 Member in the Changling Sag can be classified into two intervals, which are the lower part and the upper part, with high TOC content and low TOC content, respectively. It can be proved from the results of geochemical indicators that under warm and humid climatic conditions the relatively lower part was generated in the anoxic environment. Terrigenous input brought nutrients to the water body of the lake, made algae flourish, and had a relatively high paleoproductivity of the lake, which imposed a vigorous impact on the accumulation of organic matter. The upper part is mainly deposited under weakly oxidizing conditions, with gradually enhanced oxidation and reduced productivity. In contrast to the lower shale, the terrigenous inflow is relatively low. TOC content in the Qing1 Member has a positive relevance with the paleoredox conditions, as well as the paleosalinity conditions, indicating that good preservation is favorable for the accumulation of organic matter. A depositional model is proposed for the organic matter accumulation of this shale. The upper part was in a relatively hot and dry paleoclimate, with a low degree of organic matter enrichment, whereas the lower part had a warm and humid paleoclimate, with the input of terrestrial organic matter into the primary productivity of the lake basin and a high degree of organic matter enrichment.

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Section: Paleoredox Conditionsmentioning

confidence: 99%

Section: Paleosalinity Conditionsmentioning

confidence: 99%

Depositional environment variations and organic matter accumulation of the first member of the Qingshankou formation in the southern Songliao Basin, China

Ma,

Jinlai

2023

Front. Earth Sci.

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“…Element enrichment factors were used to see the enrichment or depletion of an element by comparing it with a selected standard value. In this study, the trace elemental compositions of the samples were compared with the composition of PAAS [50] through Al-normalization to identify significant deviations [51]. Element enrichment factors of X (X EF ) were calculated by X EF = (X/Al) Sample /(X/Al) PAAS .…”

Section: Trace and Rare Earth Elementsmentioning

confidence: 99%

“…Element enrichment factors of X (X EF ) were calculated by X EF = (X/Al) Sample /(X/Al) PAAS . X EF > 1 represents that element X was relatively enriched in the sample compared with X in PAAS, while X EF < 1 represents the situation of depletion [51]. The X EF values of Cr, Co, Ni, Sc, Pb, Th, Sr, Zr, and Hf were larger than 1, showing these trace elements were more enriched in the samples than in PAAS, while the X EF values of Li and Rb were much lower than 1, indicating these elements were depleted.…”

Section: Trace and Rare Earth Elementsmentioning

confidence: 99%

Geochemistry, Detrital Zircon U-Pb Geochronology, and Lu-Hf Isotopes of the Metasedimentary Rocks (Xinghongpu Formation, Late Devonian) in the Central South Qinling Orogenic Belt: Implications for Provenance and Tectonics

Zhang

Zhou

et al. 2023

Minerals

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The Xinghongpu Formation is very important for understanding the Devonian tectonic evolution of the South Qinling orogenic belt. Geochemical, detrital zircon U-Pb-Hf isotopic studies were carried out on the Late Devonian metasedimentary rocks of the Xinghongpu Formation to constrain the depositional age, the provenance, and the tectonic setting. The detrital zircon U-Pb dating results revealed that the depositional age of the Xinghongpu Formation of the Late Devonian was not earlier than 363.2 Ma. The whole-rock geochemistry suggested that (1) this suite of metasedimentary rocks was mainly derived from quartzose sediments of mature continental provenance, with a small contribution from mafic and intermediate igneous provenance, and (2) the metasedimentary sandstone of the Xinghongpu Formation from the Late Devonian was deposited in an active continental margin to continental arc setting. The detailed detrital zircon U-Pb dating showed that the age spectra of detrital zircon could be divided into four groups: (1) 416–480 Ma, accounting for about 23%; (2) 740–850 Ma, accounting for about 19%; (3) 889–1017 Ma, accounting for about 19%; and (4) 1072–1146 Ma, accounting for about 12%. It also contained a group of Early Proterozoic zircons. The age and Hf isotope of the detrital zircons suggested that the clastic sediment deposited in the Xinghongpu Formation mainly came from the South Qinling Orogenic Belt and the North Qinling Orogenic Belt. The detrital zircon Lu-Hf isotopes indicated that most zircons were the products of the ancient crustal remelting, and the mantle-derived magmatic sources contributed to the provenance. The Xinghongpu Fm. formed in an oceanic basin in a continental margin environment with arc systems.

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“…Preliminary exploration results in the basin show some prospects for shale gas resources [9]. However, affected by regional thermal uplift in the late Early Cretaceous and ancient deep burial, the source rock of well LK-1 are all in the overmature stage [10]. At present, the degree of oil and gas exploration in the basin is generally low.…”

Section: Introductionmentioning

confidence: 97%

Geochemical Characteristics and Evaluation Criteria of Overmature Source Rock of the Laiyang Formation in Well LK-1, Riqingwei Basin, Eastern China

Chen

Zhou

et al. 2023

Energies

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Total organic carbon (TOC) and hydrocarbon generation potential (Pg) are essential parameters for the qualitative evaluation of source rock and the basis for evaluating hydrocarbon resources in petroliferous basins. However, there will be some deviations in evaluating hydrocarbon resources of overmature source rock by using TOC and Pg. The super-thick overmature source rock of the Early Cretaceous Laiyang Formation was found in well LK-1, the Riqingwei Basin. To accurately understand the oil and gas potential of the Riqingwei Basin, this paper conducted a systematic organic geochemical analysis of the overmature source rock of the Early Cretaceous Laiyang Formation found in well LK-1. Combined with the results of previous thermal simulation tests on hydrocarbon generation of low-maturity samples in the Jiaolai Basin, the original total organic carbon (TOC0) content of source rock in well LK-1 was recovered and the evaluation criteria of overmature source rock was established. Results: (1) The average TOC content of well LK-1 source-rock samples is 1.25 wt.%, and the average Pg content is 0.11 mg/g. The type of organic matter is mainly type II2, including a small amount of type II1 and type III. The average reflectance of vitrinite (Ro) is 4.35%, which belongs to overmature source rock of a poor–fair level and mixed kerogen. (2) After recovery calculation, these samples’ original hydrocarbon generation potential (Pg0) contents ranged from 0.63 to 108.1 mg/g, with an average value of 6.76 mg/g. Furthermore, the TOC0 contents of the analyzed source-rock samples ranged from 0.62 to 30.6 wt.%, with an average value of 2.01 wt.%. It belongs to fair–good source rock, showing better hydrocarbon generation potential. (3) According to the relationship between the Pg0, Pg and TOC content, the evaluation standard for overmature source rock in well LK-1 was established. Under the evaluation standard of overmature source rock, a source rock with a TOC content exceeding 0.6% and a Pg content greater than 0.1 mg/g can be identified as a good source rock. This paper provides a foundation for the fine classification and evaluation of the overmature source rock of the Riqingwei Basin.

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Depositional Setting and Enrichment Mechanism of Organic Matter of Lower Cretaceous Shale in Ri-Qing-Wei Basin in the Central Sulu Orogenic Belt

Cited by 10 publications

References 39 publications

Depositional environment variations and organic matter accumulation of the first member of the Qingshankou formation in the southern Songliao Basin, China

Depositional environment variations and organic matter accumulation of the first member of the Qingshankou formation in the southern Songliao Basin, China

Geochemistry, Detrital Zircon U-Pb Geochronology, and Lu-Hf Isotopes of the Metasedimentary Rocks (Xinghongpu Formation, Late Devonian) in the Central South Qinling Orogenic Belt: Implications for Provenance and Tectonics

Geochemical Characteristics and Evaluation Criteria of Overmature Source Rock of the Laiyang Formation in Well LK-1, Riqingwei Basin, Eastern China

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