Impact of diagenesis on the microbial reservoirs of the terminal Ediacaran Dengying Formation from the Central to Northern Sichuan Basin, SW China

Xu, Zhehang; Lan, Caijun; Zhang, Benjian; Hao, Fang; Lu, Chaojin; Tian, Xiaobo; Zou, Huayao

doi:10.1016/j.marpetgeo.2022.105924

Cited by 12 publications

(2 citation statements)

References 163 publications

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“…Undoubtedly, carbonate minerals formed by fluids other than the depositional fluids (such as hydrothermal carbonate minerals) inevitably bear the imprint of the associated fluids, serving as valuable clues for tracing their origins. Previous studies on the grape-like structures of the Ediacaran Dengying Formation in the Sichuan Basin proposed various genetic mechanisms, including depositional, quasi-syngenetic, epigenetic karst, and shallow burial diagenesis origins [48][49][50][51].…”

Section: Source Of Hydrothermal Fluidsmentioning

confidence: 99%

U–Pb Dating of Fibrous Dolomite in the Hydrothermal Dolostone of the Dengying Formation, Central Sichuan Basin, and Its Response to Supercontinent Breakup

Zheng,

Wen,

et al. 2023

Minerals

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Super-deep drilling in the central Sichuan Basin encountered volcanic rocks of the Suxiong Formation, which are overlain by multiple hydrothermal alterations within the upper section of the Ediacaran Dengying Formation. This provides an excellent research opportunity to understand the pre-Cambrian hydrothermal activity and geological evolution of the western margin of the Yangtze Craton. Observations revealed the development of a series of hydrothermal dolomite aggregates characterized by the presence of brown sphalerite within fractures and pores of the carbonate rock. Microscopically, the dolomite exhibited fibrous columnar crystallization, forming radial bands with a gradual decrease in crystallization intensity from the center to the periphery. Cathodoluminescence analysis revealed the presence of approximately eight dolomite bands within the aggregate. U–Pb dating from the inner to outer bands yielded isotopic ages of 781 ± 12 Ma for the second band, 683 ± 12 Ma for the fifth, 562 ± 12 Ma for the sixth, and 545.4 ± 6.9 Ma for the seventh. The in situ rare earth element (REE) distribution patterns of the 781 and 683 Ma dolomite bands exhibited similarities. They both showed low total REE content (∑REE), with significant fractionation between light and heavy REEs. Additionally, they exhibited negative anomalies in cerium (Ce) and europium (Eu), while heavy REEs were relatively enriched. The dolomite bands at 562 and 545 Ma also exhibited similar REE characteristics, with low ∑REE and weak fractionation between light and heavy REEs. They also displayed distinct negative anomalies in Ce and Eu, indicating similar distribution patterns. These findings suggested that formation of the banded hydrothermal dolostone occurred during different tectonic events, and the presence of heavy REE-enriched hydrothermal fluids suggested a deep-seated origin. This study has provided preliminary evidence that the Dengying Formation, previously considered to be of the Ediacaran age, has undergone multiple episodes of deep-seated fluid infiltration and alteration since the Mesoproterozoic Era. Importantly, these events coincide with the rifting of the Rodinia and Pannotia supercontinents, aligning with their respective timeframes. This finding raises questions regarding the stratigraphic division and correlation of the formations in the deeply buried core area of the basin.

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Section: Source Of Hydrothermal Fluidsmentioning

confidence: 99%

U–Pb Dating of Fibrous Dolomite in the Hydrothermal Dolostone of the Dengying Formation, Central Sichuan Basin, and Its Response to Supercontinent Breakup

Zheng,

Wen,

et al. 2023

Minerals

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“…Davies et al, 2006;Gale et al, 2007;Chen, 2010;Wang et al, 2014). Leaching of meteoric water during the penecontemporaneous diagenetic period (Xu et al, 2022) and regional exposure karstification during the long subaerial diagenetic period (Xia et al, 2022;Yan et al, 2022;Gu et al, 2023) were the origins of the reservoir in the Sinian Dengying Formation. However, the sedimentary structure of microbialite rocks could influence the distribution of the dissolved pores.…”

Section: Introductionmentioning

confidence: 99%

Diagenesis and reservoir quality of Neoproterozoic dolomitized microbialites following multi-stage diagenetic fluid activity: a case study of the Sinian Dengying Formation, China

Dong

Song

et al. 2023

Front. Earth Sci.

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Neoproterozoic marine microbialites have been targets for exploration and hydrocarbon reservoir development. The original depositional fabric and diagenesis control the pore systems of microbialites, leading to the complicated origin of microbialite reservoirs. This study aimed to reveal the origin of microbialite reservoirs following multi-stage diagenetic fluid activity in the fourth Member of the Dengying Formation in the central Sichuan Basin in southwestern China. The fourth Member of the Sinian Dengying Formation developed dolomitized microbialites, mainly including stromatolites, laminates, and thrombolites. Based on the background of tectonic movement, petrology and geochemistry examinations were executed to analyze the origin of the microbialite reservoir. Based on the cathodoluminescence and the homogenization temperature of the brine inclusions, it is credible that there were four stages of diagenetic fluid activities in the burial diagenesis. In the first stage, the microbialite reservoir was charged by oil in the Silurian period, with evidence from residual asphalt around the pores. In the second stage, dolomite precipitated to incompletely fill the pore spaces. In the third stage, the silica-rich diagenetic fluid with high temperature resulted in the precipitation of authigenic quartz. In the last stage, the oil charged again during the Triassic period, followed by siliceous filling, with residual asphalt filling the pore spaces. There were two stages of subaerial emergence, which occurred in two episodes of the Sinian-Early Cambrian Tongwan movement. The evidence for the two tectonic events includes two phases of dolomites with meteoric water origin, two cycles of V, Sr, and Na element profiles, two instances of negative excursion δ18O isotope, and two cavity layers. By comparison, the karstification of reservoirs in the Tongwan III episode could generate a higher quality of reservoir than that in the Tongwan II episode. As a result, the quality of the microbialite reservoir from the fourth Member of the Dengying Formation was mainly improved by the subaerial exposure in the Tongwan III episode and then was partly destroyed by the siliceous filling. The identification of multi-staged diagenetic fluid charging can illustrate the evolution of the reservoir quality of Neoproterozoic microbialites.

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Depositional framework and reservoir characteristics of microbial carbonates in the fourth member of the middle Triassic Leikoupo Formation, western Sichuan Basin, South China

Yang

Zhu

et al. 2023

Marine and Petroleum Geology

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Impact of diagenesis on the microbial reservoirs of the terminal Ediacaran Dengying Formation from the Central to Northern Sichuan Basin, SW China

Cited by 12 publications

References 163 publications

U–Pb Dating of Fibrous Dolomite in the Hydrothermal Dolostone of the Dengying Formation, Central Sichuan Basin, and Its Response to Supercontinent Breakup

U–Pb Dating of Fibrous Dolomite in the Hydrothermal Dolostone of the Dengying Formation, Central Sichuan Basin, and Its Response to Supercontinent Breakup

Diagenesis and reservoir quality of Neoproterozoic dolomitized microbialites following multi-stage diagenetic fluid activity: a case study of the Sinian Dengying Formation, China

Depositional framework and reservoir characteristics of microbial carbonates in the fourth member of the middle Triassic Leikoupo Formation, western Sichuan Basin, South China

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