Characteristics and pore genesis of dolomite in Ordovician Yingshan Formation in Gucheng area, Tarim Basin

Wang, Shan; Cao, Yinghui; Du, Debin; Zhang, Yajin; Liu, Ce

doi:10.18654/1000-0569/2020.11.14

Cited by 12 publications

(6 citation statements)

References 20 publications

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“…In addition, previously published datasets on the northern slope of the Tazhong Uplift were analysed together to bring new constraints on the nature of diagenetic fluids. These published data include silicon isotopes of the cherts (Chen et al, 2015;Table S1), REE + Y results of siliceous limestones (Hong et al, 2018;Li, 2016;Table S2) and igneous rocks (Yu, 2009; Table S2), and carbon and oxygen isotope data of the dolomites (Guo et al, 2020;Wang, 2017;Wang et al, 2020; Table S3). The following three points need to be highlighted here: Firstly, these collected carbon and oxygen isotopes are considered comparable as all these data have reportedly been normalised to Vienna Pee Dee Belemnite (VPDB) with an accuracy of ±0.1‰; Secondly, the same computations for Ce and Eu anomalies are adopted in these references, which are otherwise recalculated before analysis; Thirdly, these published datasets are evaluated here to give new insights into diagenetic fluids, for example, solute transport mechanisms.…”

Section: Methodsmentioning

confidence: 99%

Volcanic events‐related hydrothermal dolomitisation and silicification controlled by intra‐cratonic strike‐slip fault systems: Insights from the northern slope of the Tazhong Uplift, Tarim Basin, China

et al. 2021

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Ordovician carbonate rocks on the northern slope of the Tazhong Uplift in the Tarim Basin are modified to varying degrees by hydrothermal fluids related to multiple tectonic-thermal events, but the nature, origin and circulation mechanisms of such hydrothermal fluids remain debated. In this article, in situ rare-earth elements and yttrium (REE + Y) concentrations, previously published geochemical datasets and petrographic investigations are integrated to develop a thermo-tectonic evolution model to improve understanding of silicification and dolomitisation occurring in the interior of the craton basin. δ 30 Si values, REE + Y ratios and fluid mixing models using modern black smoker fluid and seawater indicate that magma-sourced hydrothermal fluids, rather than basinal brine heated by magmatism, are responsible for the precipitation of cherts. Petrological and geochemical evidence suggests that deep-seated, ultramafic-derived hydrothermal fluids and/or magmatic fluids associated with Permian volcanism may have been involved in the formation of hydrothermal dolomites in the study area. Accompanying formation and reactivation of the strike-slip faults on the northern slope of the Tazhong Uplift, small volumes of hydrothermal fluids might have been triggered by seismic pumping. The early formed strike-slip fault systems may also have served as conduits for the subsequent large-scale transport of deep-seated, ultramafic-derived thermal fluids and/or Permian magmatic fluids, along which fluids were transported upwards at high flow rates. Carbonation of ultramafic rocks through interaction with deep-seated hydrothermal fluids rich in CO 2 may have served as a magnesium and silica source for dolomitisation and silicification. Trans-tensional troughs on NNE-trending strike-slip faults with positive flower structure are favourable locations for dolomitisation and silicification.

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Section: Methodsmentioning

confidence: 99%

Volcanic events‐related hydrothermal dolomitisation and silicification controlled by intra‐cratonic strike‐slip fault systems: Insights from the northern slope of the Tazhong Uplift, Tarim Basin, China

et al. 2021

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“…The δ 18 O of fine crystalline dolostone (−7.18‰ to −8.53‰) and meso-coarse crystalline dolostone (−7.26‰ to −8.35‰) in this study were more negative than that of limestone (average value of −6.92‰). However, the δ 18 O of hydrothermal dolostones in other basins is usually below −10‰ [56,57], the relatively heavier δ 18 O in the study might have been influenced by the high salinity. Strontium isotope could be used to identify the occurrence of hydrothermal fluids [8].…”

Section: Dolomitization Of Dolostone Formed By Hydrothermal Fluidsmentioning

confidence: 86%

The Diagenetic Alteration of the Carbonate Rocks from the Permian Qixia Formation as Response to Two Periods of Hydrothermal Fluids Charging in the Central Uplift of Sichuan Basin, SW China

Chen

Deng

et al. 2021

Minerals

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The hydrothermal fluid–carbonate rock reaction is frequently regarded to occur in deep-burial diagenesis, and the hydrothermal dissolution is usually distributed and takes place along the faults. Previous studies have suggested that there was hydrothermal fluid activity locally in the Permian Qixia Formation in Sichuan Basin, likely related to the Emeishan basalt eruption. However, the effect of hydrothermal fluids on the carbonate rocks of the Qixia Formation in the central uplift of Sichuan Basin is still unclear. Based on the characteristics and geochemical parameters of the diagenetic minerals, this study aims to reveal the diagenetic alteration related to the hydrothermal fluid–rock reaction in the Qixia Formation and reestablish the diagenetic evolution by using the timing of diagenetic mineral precipitation. The methods include petrographic observation; trace and rare earth element (REE) analysis; C, O and Sr isotope measurement; fluid inclusion temperature measurement and cathodoluminescence analysis. According to the petrographic characteristics, the dolostones are mainly of crystalline structure, namely fine-medium crystalline dolostone, meso-coarse crystalline dolostone, and coarse crystalline dolostone, with the cathodoluminescence color becoming brighter in that order. The limestones from the Qixia Formation are of the bioclastic limestone type, with no cathodoluminescence color. Compared with dolostones, limestones have higher Sr content, lower Mn content, and heavier oxygen isotopes. With the crystalline size of dolostone becoming coarser, the oxygen isotopes of dolostones tend to become lighter. The meso-coarse crystalline dolostone has the highest Mn content and negative carbon isotope. Both limestones and dolostones have an obvious positive Eu anomaly in the Qixia Formation. However, the REE patterns of fine-medium crystalline dolostones are very different from those of meso-coarse crystalline dolostones. It is credible that there were two periods of hydrothermal fluid charging, with different chemical compositions. The first period of hydrothermal fluids could laterally migrate along the sequence boundary. Fine-medium crystalline dolostones were almost completely distributed below the sequence boundary and were dolomitized during the shallow burial period. As products of the hydrothermal fluid–dolostone reaction, the saddle-shaped dolomites in the meso-coarse crystalline dolostones were the evidence of the second period of hydrothermal fluids. As a result, the dolomitization model was established according to the timing of diagenetic mineral precipitation, which can improve that the geological understanding of the effect of hydrothermal fluid activities on the carbonate rocks in the Qixia Formation.

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“…In general, dolomite ΣREEs are higher than limestone. The measured results were standardized for the Australian Post-Archean mean shale (PAAS) [34], and the standardized (SN) element anomalies were calculated using the following methods: δCe = 2 × Ce SN /(La SN + Pr SN ), δEu = 2 × Eu SN /(Sm SN +) [25]; if δCe and δEu are greater than 1.2, they are judged as positive anomalies; if δEu and δCe are less than 0.8, they are judged as negative anomalies. As can be seen from the standardized rare earth element partitioning pattern (Figure 7), both dolomites and limestone have the characteristics that the content of light rare earth elements (La~Eu) is smaller than that of heavy rare earth elements (Gd~Lu), showing no "tilt upward" pattern.…”

Section: Rare Earth Elementsmentioning

confidence: 99%

Petrological, Geochemical and Chronological Characteristics of Dolomites in the Permian Maokou Formation and Constraints to the Reservoir Genesis, Central Sichuan Basin, China

Bai,

Zheng,

Dai

et al. 2023

Minerals

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The Middle Permian Maokou Formation in the Sichuan Basin has huge resources and is an important target for natural gas exploration. In recent years, significant exploration breakthroughs have been made in the dolomite field of member Mao-2 in central Sichuan, and the gas production of several wells has exceeded 1 × 106 m3/d, indicating promising prospects for exploration. However, the origin of the dolomite reservoir in member Mao-2 remains ambiguous, which restricts the accurate prediction of favorable reservoirs. This study focuses on drilling in the Hechuan area as its research object, by using a detailed description of the cores from member Mao-2 of seven wells; samples were selected for tests of the degree of dolomite cation ordering, stable carbon and oxygen isotopic compositions, strontium isotopic composition, rare earth elements, LA-ICP-MS element mapping and U-Pb dating. It is clarified that: (1) The crystalline dolomite of member Mao-2 in the Hechuan area is the main reservoir rock, and the heterogeneous vugs and fractures are the main reservoir space. The dolomite in member Mao-2 has been characterized by a low degree of cation ordering value (avg. 0.59), with values of δ13C (avg. 3.87‰), δ18O (avg. −7.15‰) and 87Sr/86Sr (avg. 0.707474) having similar geochemical characteristics to Middle Permian seawater; the REEs normalized distribution patterns have similar characteristics to limestone; and the U-Pb age (261.0~262.0 Ma) corresponds to the age in the Capitanian stage of the Permian Guadalupian Series. (2) Petrological studies show that member Mao-2 has vertical karstification zonation characteristics; syngenetic karstification controls the formation of a large-scale fracture-cave system in the phreatic zone; the dolomitization of sediment in the fracture-cave system occurred during the penecontemporaneous period with locally restricted seawater. (3) The main controlling factors of the reservoir were syngenetic karstification, early dolomitization and hydrothermal dissolution related to Emei taphrogenesis. The research results are of great significance for dolomite reservoir prediction; the highlands of paleogeomorphology with syndepositional faults are favorable areas for dolomite reservoirs.

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Characteristics and pore genesis of dolomite in Ordovician Yingshan Formation in Gucheng area, Tarim Basin

Cited by 12 publications

References 20 publications

Volcanic events‐related hydrothermal dolomitisation and silicification controlled by intra‐cratonic strike‐slip fault systems: Insights from the northern slope of the Tazhong Uplift, Tarim Basin, China

Volcanic events‐related hydrothermal dolomitisation and silicification controlled by intra‐cratonic strike‐slip fault systems: Insights from the northern slope of the Tazhong Uplift, Tarim Basin, China

The Diagenetic Alteration of the Carbonate Rocks from the Permian Qixia Formation as Response to Two Periods of Hydrothermal Fluids Charging in the Central Uplift of Sichuan Basin, SW China

Petrological, Geochemical and Chronological Characteristics of Dolomites in the Permian Maokou Formation and Constraints to the Reservoir Genesis, Central Sichuan Basin, China

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