Activity of hydrothermal fluid at the bottom of a lake and its influence on the development of high-quality source rocks: Triassic Yanchang Formation, southern Ordos Basin, China

You, Jiyuan; Liu, Y.; Zhou, Dingwu; Zheng, Qi; Vasichenko, K.; Chen, Z.

doi:10.1080/08120099.2019.1612783

Cited by 24 publications

(15 citation statements)

References 42 publications

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“…High-quality source rocks have been developed in the Chang 7 Member of the Upper Triassic Yanchang Formation on the southern margin of the Ordos Basin. Previous studies 7 , 8 have also confirmed the occurrence of hydrothermal activity during the deposition of the source rocks. Based on research about modern hydrothermal deposition and submarine black chimneys, we study the morphology, material composition, structure, mineral characteristics, geochemical characteristics and formation stages of hydrothermal chimneys, and we compare them with chimney samples from modern ocean floors and continental hydrothermal activity and discuss their geological significance.…”

Section: Introductionsupporting

confidence: 60%

Triassic hydrothermal chimneys from the Ordos Basin of Northern China

You

Liu

Zhou

et al. 2021

Sci Rep

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Because few well-preserved hydrothermal chimneys have been found in terrestrial sedimentary rocks, research on paleo-thermal vents in geological history is relatively sparse. In this study, we present our original discovery of “hydrothermal chimneys” from the Chang 7 source rocks of the Triassic Yanchang Formation in the Ordos Basin, China, and provide the best evidence for deciphering hydrothermal activity preserved in the geological record (i.e., sedimentary rocks). Three possible chimney samples (i.e., samples 1551.6, 1551.6–2 and 1574.4) were collected for this study; they were interbedded with mudstones and oil shales, indicative of a deep-lake sedimentary environment. All three samples consist mainly of anhydrite, pyrite, and dolomite with the formation of mineral zoning across the walls of these structures, suggesting a sulfate-dominated stage and a carbonate-sulfide replacement stage. Moreover, their in situ geochemistry is characterized by high Eu, U, Th, Sr, Mn and U/Th ratios, which are typical indicators of hydrothermal vents. In addition, their S isotopes range from 7.89% to 10.88%, near the values of magma sulfur, implying a possible magmatic trigger for these hydrothermal vents. All this evidence shows that the Triassic sedimentary rocks of the Ordos Basin probably contain hydrothermal chimneys. Comparing ancient hydrothermal chimneys to modern hydrothermal chimneys, we should note the important implications of ancient chimneys; their formation mechanism may have been related to oil production, and they are possible indicators for future oil investigations. Further, they have great significance for studying the hydrothermal properties of primary dolomite.

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Section: Introductionsupporting

confidence: 60%

Triassic hydrothermal chimneys from the Ordos Basin of Northern China

You

Liu

Zhou

et al. 2021

Sci Rep

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“…High-quality source rocks have been developed in the Chang 7 Member of the Upper Triassic Yanchang Formation on the southern margin of the Ordos Basin. Previous studies [8,9,10,11,12] have also con rmed the occurrence of hydrothermal activity during the deposition of the source rocks. Based on research about modern hydrothermal deposition and submarine black chimneys, we study the morphology, material composition, structure, mineral characteristics, geochemical characteristics and formation stages of hydrothermal channels, and we compare them with chimney samples from modern ocean oors and continental hydrothermal activity and discuss their geological signi cance.…”

Section: Introductionmentioning

confidence: 84%

“…8b) [25] and the SiO 2 /(K 2 O + Na 2 O)-MnO/TiO 2 diagram (Fig. 8a) [26] are successfully applied to the identi cation of terrestrial hydrothermal deposition [10,27] . The study area in this paper is characterized by typical lacustrine hydrothermal deposition.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, during the Late Triassic, hydrothermal deposition at the bottom of the lake [8] , interlayers of tuff [16] , turbidites [17] , deposition of sandy debris ows [18] , deposits of seismite, extensive development of sandstone veins and mutations of sporopollen assemblages [13] accumulated that re ect the strong structural characteristics of the basin. In the context of strong tectonic activity in this region, basal ruptures may have been activated [10] , which created conditions for the development of LTHA in the basin.…”

Section: Regional Geological Backgroundmentioning

confidence: 99%

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Triassic Low Temperature Hydrothermal Activities(LTHA) From the Ordos Basin of Northern China

You¹,

Liu²,

Zhou³

et al. 2021

Preprint

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Because few well-preserved hydrothermal channels have been found in terrestrial sedimentary rocks, research on LTHA in geological history is relatively sparse. In this study, we present our original discovery of “hydrothermal channels” from the Chang 7 source rocks of the Triassic Yanchang Formation in the Ordos Basin, China, and provide the best evidence for deciphering LTHA preserved in the geological record (i.e., sedimentary rocks). Three possible LTHA samples (i.e., samples 1551.6, 1551.6-2 and 1574.4) were collected for this study; they were interbedded with mudstones and oil shales, indicative of a deep-lake sedimentary environment. All three samples consist mainly of anhydrite, pyrite, and dolomite with the formation of mineral zoning across the walls of these structures, suggesting a sulfate-dominated stage and a carbonate-sulfide replacement stage. Moreover, their in situ geochemistry is characterized by high Eu, U, Th, Sr, Mn and U/Th ratios, which are typical indicators of hydrothermal vents. In addition, their S isotopes range from 7.89% to 10.88%, the magmatic sulfur accounted for approximately 94.3%, implying a possible magmatic trigger for these hydrothermal channels. All this evidence shows that the Triassic sedimentary rocks of the Ordos Basin probably contain LTHA. Comparing ancient LTHA to modern hydrothermal chimneys, we should note the important implications of LTHA; their formation mechanism may have been related to oil production, and they are possible indicators for future oil investigations. Further, they have great significance for studying the hydrothermal properties of primary dolomite.

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“…Furthermore, syn-sedimentary hydrothermal activity at the lake bottom could facilitate the circulation of lake water and nutrients, such as phosphorus and nitrogen, making them available to organisms. Consequently, the biological productivity of the lake may be promoted, resulting in an increase in the organic carbon input to the sediments (Zhang et al 2010;Liu et al 2019;You et al 2019;Jiao et al 2020). The Lucaogou Formation in the Junggar Basin is thought to be one of the best source rocks in the world (Graham et al 1990;Carroll et al 1992).…”

Section: Geological Significancementioning

confidence: 99%

Hydrothermal-sedimentary dolomite — a case from the Middle Permian in eastern Junggar Basin, China

et al. 2020

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The Middle Permian Lucaogou Formation in the Jimusar Sag, eastern Junggar Basin, NW China, was deposited in a salt lake within an intracontinental rift basin with intense hydrothermal activity. Hydrothermal-sedimentary dolomite in the form of three types of dolostones, namely, analcime-feldspar dolostone (AFD), silicic dolostone (SD) and buddingtonite-albite dolostone (BAD), related to syn-sedimentary hydrothermal activity at lake bottom was discovered. The characteristics and formation mechanism of the dolomite were studied based on micron-scale petrographic and isotopic geochemical research. The syn-depositional formation of these dolostones was indicated by their rock-mineral features and syn-sedimentary deformation stage. The dolomite was composed of relatively poorly ordered proto-dolomite crystals with micron-sized spherical or sub-spherical morphology and coexisted with hydrothermal minerals, including analcime, buddingtonite, albite and chalcedony. Albite clasts were replaced by the dolomite, indicating high-temperature conditions during formation. The remarkably low strontium isotopic compositions of the dolostones (87 Sr/ 86 Sr with an average of 0.705687) indicated that mantle-derived materials might have involved in the ore-forming fluid. The dolostones had positive δ 13 C PDB values (with an average of 6.94‰) and negative δ 18 O PDB values (with an average of − 8.12‰). Based on the δ 18 O PDB values, the formation temperatures of the dolomite were at least~25°C higher than those of the penecontemporaneous dolomite in the Lucaogou Formation in the study area. It is concluded that the dolomite precipitated from hydrothermal fluid erupting at the lake bottom. The possible genetic models are described. We suggest that the hydrothermalsedimentary dolomite is an important genetic type, and this study may help increase the awareness of this understudied type of dolomite.

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Activity of hydrothermal fluid at the bottom of a lake and its influence on the development of high-quality source rocks: Triassic Yanchang Formation, southern Ordos Basin, China

Cited by 24 publications

References 42 publications

Triassic hydrothermal chimneys from the Ordos Basin of Northern China

Triassic hydrothermal chimneys from the Ordos Basin of Northern China

Triassic Low Temperature Hydrothermal Activities(LTHA) From the Ordos Basin of Northern China

Hydrothermal-sedimentary dolomite — a case from the Middle Permian in eastern Junggar Basin, China

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