Origin and characteristics of grain dolomite of Ordovician Ma55 Member in the northwest of Ordos Basin, NW China

Zhang, Xi; Zhang, Tingshan; Lei, Bianjun; Zhang, Jingxuan; Ji, Zhiming; Zhao, Zhenjiang; Yong, Jinjie

doi:10.1016/s1876-3804(19)60272-7

Cited by 10 publications

(6 citation statements)

References 13 publications

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“…Precursor calcites forming sucrosic dolomites are commonly deposited in subtidal high-energy zones in the open seas, while biogenic dolomites are formed in a restricted marine environment with a temperature of 30~45 °C, salinity of 3.5~10%, and pH value greater than 8.5 (Zhang et al, 2019). In the studied interval, discernable gypsum and halite molds are observed (Figure 2D), which are typical characteristics of the exposure zone in the supratidal environment.…”

Section: Origin Of Sucrosic Dolomitesmentioning

confidence: 89%

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Dolomite Origins of the Carbonate Successions From the Chihsia Formation, South China: A Case Study From the Pingdingshan Section

et al. 2022

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The carbonate successions from the Chihsia Formation play an important role for hydrocarbon exploration in the South China. However, the dolomites occurring in the upper section of the Chihsia Formation have been enigmatic, which confined further understanding of the depositional and/or diagenetic fluids and hydrocarbon prediction. In this study, the Pingdingshan section was investigated as a typical outcrop of Chihsian carbonates. On the basis of lithofacies/mineralogic observation of hand specimens and thin-sections, three types of dolomites were classified according to their crystal sizes, that is, micritic dolomite, sucrosic dolomite, and saddle dolomite. Comprehensive, micro-area geochemical proxies, including homogenization temperatures of fluid-inclusions, carbon and oxygen isotopes, and trace and rare-earth elements, were analyzed on different types of dolomites and matrix calcites. The results revealed that the selected samples were representative of temporal seawater and were not contaminated by terrestrial input. The temperatures and salinities of fluid-inclusions, combined with carbon and oxygen isotopic values, revealed that sucrosic dolomites originated from penecontemporaneous micritic dolomites, which had been crystallized and altered into fine- to medium-sized dolomite clusters during the later-stage burying process. In contrast, the saddle dolomites occurring in carbonate matrix or fractures were formed in a hydrothermal environment with a dolomitizing fluid temperature higher than 170°C. This inference is consistent with evidence from rare-earth elements and carbon and oxygen isotopes. Our findings provide new clues for the origin elucidation of dolomitizing fluids in the Chihsia Formation, South China.

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Section: Origin Of Sucrosic Dolomitesmentioning

confidence: 89%

“…The detection limits range from 0.001 to 1 ppm with respect to different elements, and the accuracy is better than ±5%. The specific workflow was conducted referring to Zhang et al (2019).…”

Section: Methodsmentioning

confidence: 99%

Dolomite Origins of the Carbonate Successions From the Chihsia Formation, South China: A Case Study From the Pingdingshan Section

et al. 2022

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“…The Majiagou Formation is the Paleozoic Ordovician strata, which corresponds to the Floian, Dapingian, and Darriwilian in the international strata. The Majiagou Formation in the Ordos Basin can be divided into six members from M 1 to M 6 , of which the M 5 member can be subdivided into M 5 1 to M 5 10 (Figure 2) [27,[44][45][46]. The Ordovician Majiagou sedimentary period was a shallow carbonate platform environment, mainly developing tidal flat facies and shoal facies deposits.…”

Section: Geological Settingmentioning

confidence: 99%

Dolomitization Controlled by Paleogeomorphology in the Epicontinental Sea Environment: A Case Study of the 5th Sub-Member in 5 Member of the Ordovician Majiagou Formation in Daniudi Gas Field, Ordos Basin

et al. 2021

Minerals

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The 5th sub-member in 5 Member Ordovician Majiagou Formation in Daniudi Gas Field, Ordos Basin, is deposited in an environment consisting of an ancient epicontinental sea, where very fine crystalline dolostone reservoir has developed. In this study, based on the petrological and geochemical characteristics, the genesis of the dolomite developed in M55 were studied by analyzing the properties and sources of the dolomitization fluids, and the influence of the paleogeomorphology differences on the distribution of dolostone was also discussed in order to clarify the distribution of the dolostone developed in the lime flat of the epicontinental sea. The dolostone of the M55 had a crystal structure, mainly including microcrystalline and very fine crystalline. The content of MgO and CaO in dolomite was negatively correlated, indicating that it was the result of replacement. The dolomite was dark red under cathode luminescence, and the distribution mode of rare earth elements showed the negative anomaly of Ce and Eu, indicating that the dolomitization fluid was sea-sourced fluid. The δ13C, δ18O, and 87Sr/86Sr isotope range of limestone was similar to that of Ordovician seawater in the study area, whereas the δ13C, δ18O, and 87Sr/86Sr of dolostone were obviously more positive than that of limestone. The substitute index of the salinity (Z) of the dolomitization fluid was higher than 122, which is higher than limestone (Z = 120.5), indicating that the dolomitization fluid was slightly evaporated seawater. The wormholes observed on the core and the gypsum in the penecontemporaneous period observed in the thin sections indicated that the dolostone was formed in a period when the sea level was relatively low, and it was the result of seepage–reflux dolomitization. By analyzing the correlation between the thickness of dolostone and the paleogeomorphology of the M55 of the sedimentary period, it was found that the thickness of dolostone at relatively high altitude was significantly larger than that of other areas. The development of dolostone was controlled by sea level, and the local paleogeomorphology controls the distribution of dolostone during the period of low sea level. There were many more limestone–dolostone cycles and larger cumulative thicknesses of dolostone at relatively higher topography. This study provides a theoretical basis for the prediction of the distribution of dolostone reservoirs in the carbonate tidal flat environment dominated by lime flats under the background of the ancient epicontinental sea.

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“…4d). Some crystals of dolomite commonly have ring-banded luminescence, reflecting changes in fluid composition during the growth of dolomite (Liu et al 2010;Zhang et al 2019).…”

Section: Characteristicsmentioning

confidence: 99%

“…Therefore, it is necessary to analyze the diagenetic alteration intensity of the elements. Previous studies have shown that samples with Mn/Sr (ratio of Mn to Sr) less than 2~3 are generally believed to have experienced weak burial diagenetic alteration (He et al 2014;Zhang et al 2019). During the process of burial and diagenesis, rocks with a significant correlation between δCe and Dy N / Sm N are strongly affected by diagenetic fluids (Wang et al 2018a, b).…”

Section: Alteration Strength Of Elementsmentioning

confidence: 99%

Geochemical characteristics and genesis of lower Paleozoic dolomites in the central Bohai Sea

Song

Qin

et al. 2021

Arab J Geosci

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Dolomite diagenesis is a key issue in the evolution of dolomite reservoirs. Hence, lower Paleozoic carbonate samples from the Bonan Low Uplift are analyzed. Data collected from thin sections, cathodoluminescence, X-ray diffraction, major and trace elements, rare earth elements, isotopes, and other experimental work to determine the types, diagenetic environment, and fluid characteristics of dolomite, are used to determine its genesis. Three main dolomite types are identified: D1 with a very good original structure, D2 without an original structure, and D3 with a poorly preserved original structure. The concentrations of many geochemical indicators follow the order of D1>D2>D3. The ratios of MnO to TiO 2 in both D2 and D3 are >0.5, and the Rb concentration of D2 is greater than that of D3. δCe shows that D1 and D2 are partially oxidized, while D3 is not. The D1, D2, and D3 diagenetic temperatures are 49.28, 54.96, and 50.23°C, respectively. The order degrees of D1 and D2 are 0.56 and 0.75, respectively, while that of D3 ranges widely. Comprehensive data show that D1 originated from evaporative dolomitization in the syndiagenetic period, and the diagenetic fluid was sea-sourced fluid mixed with terrestrial fluids. D2 was generated by seepage reflux dolomitization, which occurred in the penecontemporaneous-shallow burial period, and its high-salinity diagenetic fluid is inherited from sea-sourced fluids, with the participation of pore fluids. D3 was formed in shallow burial dolomitization, and its diagenetic fluid inherited from sea-sourced fluids and pore fluids is characterized by low salinity.

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Origin and characteristics of grain dolomite of Ordovician Ma55 Member in the northwest of Ordos Basin, NW China

Cited by 10 publications

References 13 publications

Dolomite Origins of the Carbonate Successions From the Chihsia Formation, South China: A Case Study From the Pingdingshan Section

Dolomite Origins of the Carbonate Successions From the Chihsia Formation, South China: A Case Study From the Pingdingshan Section

Dolomitization Controlled by Paleogeomorphology in the Epicontinental Sea Environment: A Case Study of the 5th Sub-Member in 5 Member of the Ordovician Majiagou Formation in Daniudi Gas Field, Ordos Basin

Geochemical characteristics and genesis of lower Paleozoic dolomites in the central Bohai Sea

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