Nucleation and stabilization of Eocene dolomite in evaporative lacustrine deposits from central Tibetan plateau

Wen, Yixiong; Sánchez‐Román, Mónica; Li, Yalin; Wang, Chengshan; Han, Zehua; Zhang, Laiming; Gao, Yuan

doi:10.1111/sed.12744

Cited by 17 publications

(13 citation statements)

References 103 publications

(172 reference statements)

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“…Thirdly, the close attachment of dolomite (especially the ankerite crystals) to chlorite flakes in this study is another potent evidence supporting the primary genesis of dolomitization. Highly negative-charged clay minerals manage to catalyze the abiotic precipitation of dolomite at low temperatures [51]. The clay surface could facilitate the process of nucleation, by forming an electrostatic binding with Mg 2+ and Ca 2+ ions [52], a possible route for dolomitization in this study.…”

Section: Genesis Of Dolomite Nodulementioning

confidence: 78%

Multielement Imaging Reveals the Diagenetic Features and Varied Water Redox Conditions of a Lacustrine Dolomite Nodule

Liu

Zhang

et al. 2022

Geofluids

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The genesis of dolostone has long been puzzling for more than two centuries. Although much work has been done on investigating the process of dolomitization, little emphasis has been put on examining the diagenetic water redox condition with the wealthy geochemical information preserved in primary dolomite, which is believed to archive the aqueous environment as well as biotic and/or abiotic effects during formation. In situ interpretation with high resolution is a prerequisite in refined research of dolomite. Here, we reported the multielement imaging results of a lacustrine dolomite nodule with the host black shale from the Songliao Basin, northeast of China. Micro X-ray fluorescence (μ-XRF) with a spatial resolution down to 10 μm was used for in situ scanning. Two key parameter settings of the μ-XRF, including single-point exposure time and spatial resolution, were optimized to achieve a better result in a reasonable scanning time scale. The final imaging data graphically revealed dynamic variation of elemental distributions, including elements enriched in dolomite (e.g., Ca, Mg, Fe, and Mn), clastic quartz (Si), and clay minerals (e.g., Al and K) and redox-sensitive trace elements (e.g., Cr, Mo, V, and U). The well-preserved laminated structures inside the nodule and the features with a magnesium-rich core wrapped with an iron-concentric outer layer and a manganese-concentric shell together indicated its primary form as dolomite and a gradual transformation into ankerite as well as manganese-ankerite. The elemental variation indicates a varied bottom water redox condition, which involved from sulfidic to ferruginous and manganous zones. Here, we propose that the intermittent supplies of sulfate and Fe-/Mn-oxidized minerals interrupting the black shale deposition while favoring dolomitization might be brought by the oxidized and salted seawater. And this lacustrine dolomite is expected to be a potential fingerprint mineral in tracking the seawater intrusions to the Songliao Basin which happened 91 million years ago.

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Section: Genesis Of Dolomite Nodulementioning

confidence: 78%

Multielement Imaging Reveals the Diagenetic Features and Varied Water Redox Conditions of a Lacustrine Dolomite Nodule

Liu

Zhang

et al. 2022

Geofluids

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“…This phenomenon is in accordance with the scarcity of dolomite in modern marine deposits although seawaters are supersaturated with respect to ordered dolomite (Raudsepp et al ., 2022). The difficulty for low‐T dolomite formation mainly resides in the strong hydration of Mg 2+ ions (Zhang et al ., 2012; Shen et al ., 2014; Kaczmarek et al ., 2017; Wen et al ., 2020; Fang & Xu, 2022), which, however, seemed not to be a big constraint for the formation of other Mg‐rich minerals in alkaline environments. The direct precipitation of anhydrous Na‐Mg‐carbonate (eitelite) from lake waters, as well as the displacive diagenetic formation of northupite near the water–sediment interface, suggests that there were enough free Mg 2+ ions in the saline alkaline lakes of the Fengcheng Formation available for Mg‐Na‐carbonate formation.…”

Section: Discussionmentioning

confidence: 99%

“…Isolated dispersed dolomite is a common mineral component in saline lake siliciclastic sediments (Last, 1990) and it can be present in various lithofacies, such as deep‐water laminates and marginal‐playa mudstones. Genesis of such dolomite is generally controversial and suggested hypotheses include primary dolomite (Smith & Stuiver, 1979; Wen et al ., 2020), penecontemporaneous dolomite (Wolfbauer & Surdam, 1974), organogenic dolomite (Slaughter & Hill, 1991; Mazzullo, 2000), detrital dolomite (Eugster & Surdam, 1973) and hydrothermal primary dolomite (Wen et al ., 2013; Yang et al ., 2020). In the Fengcheng Formation, the isolated dispersed dolomite crystals show zoned cathodoluminescence (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Large, isolated dolomite crystals (20 to 70 μm) are also the major dolomite type in the saline alkaline lacustrine Wilkins Peak Member of the Green River Formation, which are much larger in size than the dolomite crystals of the overlying meromictic brackish lacustrine Laney Member (5 to 10 μm) (Murphy et al ., 2014). Since most reported primary dolomite (Ca‐rich dolomite or very high Mg‐calcite) crystals, that generated in microbial mats or on Mg‐clay mineral surfaces in environmental depositional settings (Casado et al ., 2014; Liu et al ., 2019; Wen et al ., 2020) occur at the nanometre scale (Sánchez‐Román et al ., 2008), the large dolomite crystals of the Wilkins Peak Member and Fengcheng Formation were interpreted to have undergone overgrowth on tiny primary nuclei. The zoned dark red to olive green cathode‐luminescence and zoned bright fluorescence suggest an anoxic, organic‐rich environment for dolomite growth in the shallow subsurface, a specific subsurface milieu that could continue supplying Mg 2+ , Ca 2+ and

{CO}_{3}^{2 -}

.…”

Section: Discussionmentioning

confidence: 99%

“…(Tosca & Wright, 2015; del Buey et al ., 2018; Pozo & Calvo, 2018; Tutolo & Tosca, 2018; Table 1). Diagenetic relationships between Mg‐clays and Ca‐Mg‐carbonates can be classified into the following. The existence of clays facilitates proto‐dolomite (non‐ordered Ca‐rich dolomite and/or very high Mg‐calcite) formation, by providing templates for dolomite nucleation or by keeping high alkalinity water in its clay structures (Díaz‐Hernández et al ., 2013; Casado et al ., 2014; Liu et al ., 2019; Wen et al ., 2020). At an early diagenetic stage, the formation of Mg‐rich clays via transformation of reactive detrital dioctahedral smectite or from authigenesis provides a sink for Mg 2+ in porewaters, limiting authigenic dolomite precipitation (Bristow et al ., 2012; Chase et al ., 2021).…”

Section: Introductionmentioning

confidence: 99%

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Constraints on dolomite formation in a Late Palaeozoic saline alkaline lake deposit, Junggar Basin, north‐west China

2023

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Alkaline lakes (pH > 9) are among the few modern sedimentary environments that are hydrochemically favourable for low‐temperature dolomite formation. While Mg‐clays and Mg‐evaporites also form more easily in alkaline environments, few studies have focused on how the kinetically inhibited dolomite wins the competition for Mg2+. Here, a basin‐wide survey of the distribution, paragenesis and stable C, O and Mg isotopes of main Mg‐rich minerals in the Late Palaeozoic saline alkaline lake deposit of the north‐west Junggar Basin, north‐west China, is conducted to study the influence of the formation and diagenesis of eitelite, northupite and Mg‐clays on dolomite formation. Large, isolated dolomite crystals (20 to 70 μm in diameter), show positive δ13C values (ranging from +1 to +7‰) and a restricted distribution in the mudstones of the lake‐transitional zone. These crystals have been interpreted as organogenic dolomite driven by methanogenesis via fermentation of organic substrates. The δ18O values of dolomitic mudstones (from −7.4 to +3.4‰), calcitic mudstones (from −15.1 to −3.3‰) and bedded Na‐carbonate evaporites (from +0.08 to +3.7‰), together with their Mg isotopic compositions, suggest that dolomite was not enriched in the most concentrated environments or during stages with most Mg sources, but in the organic‐rich deposits containing few other authigenic Mg‐rich minerals. Dolomite is at a competitive disadvantage for Mg2+ ions compared to Mg‐evaporite and Mg‐clay minerals due to its slow crystallization rates and the deficiency of micritic calcium carbonate precursors. However, it can nucleate and progressively grow into large crystals (>20 μm) if bacterial methanogenesis could effectively lower porewater pH (<8.5) and induce the dissolution of generated eitelite, northupite or Mg‐clays. These findings suggest that high salinity and/or high alkalinity are not always favourable conditions for dolomite formation and highlight the active role of pH fluctuations in inducing low‐temperature dolomite formation.

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Microbially-mediated formation of Ca-Fe carbonates during dissimilatory ferrihydrite reduction: Implications for the origin of sedimentary ankerite

Liu,

Cao,

Yang

et al. 2023

Sci. China Earth Sci.

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Nucleation and stabilization of Eocene dolomite in evaporative lacustrine deposits from central Tibetan plateau

Cited by 17 publications

References 103 publications

Multielement Imaging Reveals the Diagenetic Features and Varied Water Redox Conditions of a Lacustrine Dolomite Nodule

Multielement Imaging Reveals the Diagenetic Features and Varied Water Redox Conditions of a Lacustrine Dolomite Nodule

Constraints on dolomite formation in a Late Palaeozoic saline alkaline lake deposit, Junggar Basin, north‐west China

Microbially-mediated formation of Ca-Fe carbonates during dissimilatory ferrihydrite reduction: Implications for the origin of sedimentary ankerite

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