Genesis mechanism and Mg isotope difference between the Sinian and Cambrian dolomites in Tarim Basin

Zhu, Guangyou; Li, Xi; Li, Tingting; Zhou, Lei; Wu, Yuxuan; Shen, Bing; Ning, Meng

doi:10.1007/s11430-021-1010-6

Cited by 14 publications

(4 citation statements)

References 139 publications

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“…Some researchers believe that in the late Ediacaran there existed "dolomite seas" in which primary dolomite was easily precipitated [73]. Thus, coeval seawater, microorganisms, and sedimentary organic matter jointly provided Mg 2+ , and large-scale dolomitization occurred via microbial induction [16]. In this study, MD-2 consists of a large number of well-preserved microbial fabrics, and its formation may have been related to the early activities of microbial mats [74].…”

Section: Primary or Secondary Dolomitization?mentioning

confidence: 65%

“…In previous studies, microbial dolomitization [16] and seepage-reflux dolomitization [17] have been proposed to interpret the pervasive early-formed matrix dolomites in the Qigebrak Formation. Some researchers believe that in the late Ediacaran there existed "dolomite seas" in which primary dolomite was easily precipitated [73].…”

Section: Primary or Secondary Dolomitization?mentioning

confidence: 99%

“…Deeper exploration in the Tarim Basin led to a significant breakthrough in 2020 (well Luntan-1) with the discovery of dolomite reservoirs in the Upper Ediacaran Qigebrak Formation, indicating a broad exploration potential [13], and the pervasive earlyformed dolomites are well developed [14]. However, there are still different views on the large-scale dolomitization mechanism of the Qigebrak Formation, and the focus of the controversy is whether the formation of these matrix dolomites occurred via primary precipitation [15,16] or secondary replacement [17]. Studying the origin of these earlyformed dolomites can not only provide an insight into the early dolomitization process during fluid-rock interactions but can also lead to a better understanding of the genesis of related dolomite reservoirs and hence further improve exploration strategies.…”

Section: Introductionmentioning

confidence: 99%

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Early Dolomitization Mechanism of the Upper Ediacaran Qigebrak Formation, Northwestern Tarim Basin: Evidence from Petrography, Rare Earth Elements, and Clumped Isotope

Tang,

Chen,

et al. 2023

Minerals

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The deeply buried Upper Ediacaran Qigebrak Formation dolostones in the Tarim Basin are promising future hydrocarbon exploration targets in China. However, the origin of these pervasive matrix dolomites is not well understood, which hampers further hydrocarbon exploration. In this study, petrographic, isotopic (C, O, and Sr), rare earth element (REE), and clumped isotope analyses were performed to unravel the mechanisms of early dolomitization. Petrographic investigations indicate that the Qigebrak Formation carbonates were completely replaced by three distinct types of dolomites: (1) dolomicrite (MD-1), (2) fabric-preserving dolomite (MD-2), and (3) fabric-destructive dolomite (MD-3). Despite different crystal textures, these three dolomite types have a narrow range of δ13C and 87Sr/86Sr values similar to those of coeval seawater. Furthermore, their seawater-normalized REE compositions display a seawater-like REE pattern with positive Ce anomalies. These findings suggest that the dolomitization fluids were seawater derived. From the clumped isotope temperature (TΔ47 ≈ 60 °C) and the δ18O water values of the dolomitization fluids, it can be inferred that the main mechanism for the formation of matrix dolomites was seepage-reflux dolomitization by mesosaline to penesaline seawater in the evaporative environment. MD-1 and MD-2 precipitated from mesosaline to penesaline seawater in slightly evaporated settings. MD-3 was likely formed via recrystallization of MD-1 and/or MD-2 at a greater depth. This study provides an insight into early dolomitization processes related to mesosaline to penesaline seawater, which may make the origins of dolomite reservoirs with similar geological backgrounds better understood.

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Section: Primary or Secondary Dolomitization?mentioning

confidence: 65%

Section: Primary or Secondary Dolomitization?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Early Dolomitization Mechanism of the Upper Ediacaran Qigebrak Formation, Northwestern Tarim Basin: Evidence from Petrography, Rare Earth Elements, and Clumped Isotope

Tang,

Chen,

et al. 2023

Minerals

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“…where SD m and SD o are the interannual standard deviations of the CMIP6 model runs and observed data, respectively [34,35]. Estimating future changes in population exposure to extreme precipitation events is key to understanding future vulnerability.…”

Section: Methodsmentioning

confidence: 99%

Predictive Study on Extreme Precipitation Trends in Henan and Their Impact on Population Exposure

Wang,

Wu,

et al. 2023

Atmosphere

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This study employs precipitation data sets from historical trials on 20 CMIP6 global climate models and four shared socioeconomic pathway scenario trials (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) to predict trends in extreme precipitation changes in Henan Province quantitatively, while ascertaining the risk of population exposure to extreme precipitation in this area. The capacity of the CMIP6 models to simulate extreme precipitation indices from 1985 to 2014 is assessed using CN05.1 daily precipitation observational data. The correlation coefficients of the multi-model ensemble median’s simulation of the extreme precipitation indices are approximately 0.8, with a standard deviation ratio closer to 1 compared with the single models, demonstrating superior modeling ability. Analyses using the multi-model ensemble median demonstrate an overall increase in the total amount, frequency, and intensity of extreme precipitation in Henan throughout this century, particularly in its southern regions; in the mid-century high-emission scenario (SSP5-8.5), the maximum increase in annual total precipitation exceeds 150 mm, and it can be over 250 mm in the late-century period. For the entire province, the maximum five-day precipitation increase relative to the historical period is nearly 25 mm in the late-century SSP5-8.5 scenario. The spatiotemporal concentration of precipitation will significantly increase, heightening the risk of flood disasters. Comparative analysis reveals that, under the same population prediction, the total population exposure will be higher in high radiative forcing scenarios than in low radiative forcing scenarios, especially in Kaifeng City, where the total population exposure in SSP1 and SSP5-8.5 exceeds that in SSP1-2.6 by 2 million person-days. However, in the same radiative forcing scenario, the total population exposure in the development pathway dominated by traditional fossil fuels (SSP5) will not be significantly higher than that in the sustainable development pathway (SSP1), indicating that population activity in this century will not be the main contributor to changes in total exposure. Overall, for Henan, in the same population forecast scenario, population exposure to extreme precipitation will gradually rise with global warming.

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Genesis and reservoir preservation mechanism of 10 000‐m ultradeep dolomite in Chinese craton basin

Zhu,

Li,

Zhao

et al. 2024

Deep Underground Science and Engineering

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The 10 000‐m ultradeep dolomite reservoir holds significant potential as a successor field for future oil and gas exploration in China's marine craton basin. However, major challenges such as the genesis of dolomite, the formation time of high‐quality reservoirs, and the preservation mechanism of reservoirs have always limited exploration decision‐making. This research systematically elaborates on the genesis and reservoir‐forming mechanisms of Sinian–Cambrian dolomite, discussing the ancient marine environment where microorganisms and dolomite develop, which controls the formation of large‐scale Precambrian–Cambrian dolomite. The periodic changes in Mg isotopes and sedimentary cycles show that the thick‐layered dolomite is the result of different dolomitization processes superimposed on a spatiotemporal scale. Lattice defects and dolomite embryos can promote dolomitization. By simulating the dissolution of typical calcite and dolomite crystal faces in different solution systems and calculating their molecular weights, the essence of heterogeneous dissolution and pore formation on typical calcite and dolomite crystal faces was revealed, and the mechanism of dolomitization was also demonstrated. The properties of calcite and dolomite (104)/(110) grain boundaries and their dissolution mechanism in carbonate solution were revealed, showing the limiting factors of the dolomitization process and the preservation mechanism of deep buried dolomite reservoirs. The in situ laser U‐Pb isotope dating technique has demonstrated the timing of dolomitization and pore formation in ancient carbonate rocks. This research also proposed that dolomitization occurred during the quasi‐contemporaneous or shallow‐burial periods within 50 Ma after deposition and pores formed during the quasi‐contemporaneous to the early diagenetic periods. And it was clear that the quasi‐contemporaneous dolomitization was the key period for reservoir formation. The systematic characterization of the spatial distribution of the deepest dolomite reservoirs in multiple sets of the Sinian and the Cambrian in the Chinese craton basins provides an important basis for the distribution prediction of large‐scale dolomite reservoirs. It clarifies the targets for oil and gas exploration at depths over 10 000 m. The research on dolomite in this study will greatly promote China's ultradeep oil and gas exploration and lead the Chinese petroleum industry into a new era of 10 000‐m deep oil exploration.

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Genesis mechanism and Mg isotope difference between the Sinian and Cambrian dolomites in Tarim Basin

Cited by 14 publications

References 139 publications

Early Dolomitization Mechanism of the Upper Ediacaran Qigebrak Formation, Northwestern Tarim Basin: Evidence from Petrography, Rare Earth Elements, and Clumped Isotope

Early Dolomitization Mechanism of the Upper Ediacaran Qigebrak Formation, Northwestern Tarim Basin: Evidence from Petrography, Rare Earth Elements, and Clumped Isotope

Predictive Study on Extreme Precipitation Trends in Henan and Their Impact on Population Exposure

Genesis and reservoir preservation mechanism of 10 000‐m ultradeep dolomite in Chinese craton basin

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