Characteristics and controlling factors of LORS from the Chang 7–3 section of the Triassic Yanchang Formation in the Ordos Basin

You, Jiyuan; Liu, Yiqun; Song, Shanshan; Zhou, Dingwu; Yong-ming, Yang

doi:10.1016/j.petrol.2020.108020

Cited by 10 publications

(5 citation statements)

References 30 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 [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%

“…A total of 48 sets of data were completed for in situ trace element and rare earth element experiments, which were completed at the State Key Laboratory of Continental Dynamics, Northwest University. using an Agilent 7500 ICP-MS instrument attached to a 193 nm excimer laser ablation system (Geolas 2005) [12] . All measurements were performed in time-resolved mode with helium as the carrier gas.…”

Section: Analysis Methodsmentioning

confidence: 99%

“…In the Late Triassic, the sedimentary environment on the southern margin of the Ordos Basin produced a deep lake facies (Fig. 9), with reducing conditions and low oxygen fugacity [12,14] . The hydrothermal uid was weakly acidic uid with a low pH value [8] with sulfur mainly in the form of H 2 S.Therefore, the d34S value of pyrite in the study area can approximately represent the sulfur isotope composition of the hydrothermal uids.…”

Section: Abnormalities Of In Situ S Isotopes Of Pyritementioning

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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Section: Introductionmentioning

confidence: 84%

Section: Analysis Methodsmentioning

confidence: 99%

Section: Abnormalities Of In Situ S Isotopes Of Pyritementioning

confidence: 99%

See 1 more Smart Citation

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

You¹,

Liu²,

Zhou³

et al. 2021

Preprint

Self Cite

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“…For instance, during the Chang 7 3 interval, the redox state of the bottom water near the study area (wells Y56 and Feng75) was weakly oxic-suboxic, rather than strongly anoxic [16,23,30,51]. In contrast, the southeast and southwest regions of the lake basin usually presented a redox state of strong reduction or even euxinic, indicating that the lake water was stratified [52][53][54][55]. In this scenario, the sedimentary organic matter would be well preserved, causing the TOC content in the deep lake area to remarkably increase compared with that in the Mahuangshan area.…”

Section: Geofluidsmentioning

confidence: 99%

“…Therefore, it is one of the most critical factors for controlling organic matter enrichment. Currently, the paleo-productivity proxies (Ba bio and P bio ; [55]) of the black rock series in the Chang 7 3 sub-member are mostly qualitative descriptions [15], which cannot be well compared at the basin-scale. Müller and Suess [69] provided the following equation to quantitatively characterize paleo-productivity using organic carbon: R = C × p s × 1 − φ 0:0030 × S 0:30 : ð1Þ R, C, p s , φ, and S represent paleo-productivity (g/m 2 •a), organic carbon content (%), porosity (g/cm 3 ), sediment density (%), and sedimentation rate (cm/1000a), respectively.…”

Section: Paleosalinitymentioning

confidence: 99%

Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Liao

Chen

et al. 2022

Geofluids

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The 7th member of the Late Triassic Yanchang Formation is the most important Mesozoic source rocks and shale oil reservoir in the Ordos Basin. The hydrocarbon potential and organic matter enrichment mechanism of this organic-rich member are questioned because of the high heterogeneity of continental sediments. In particular, the lack of drilling in the Chang 73 sub-member of the western Ordos Basin (central Tianhuan Depression) hinders this understanding and the progress of shale oil exploration in this region. In this study, 87 samples were collected from the well DP1 in the Tianhuan Depression, western Ordos Basin, and analyzed for sedimentology and geochemistry to unravel the paleoenvironment, paleo-productivity, and hydrocarbon potential of the Chang 73 sub-member. The results show that the Chang 73 shale is characterized by ultra-high organic matter abundance (up to 10.60%), type II kerogen, and good hydrocarbon generation potential. An intermediate chemical weathering intensity suggests that this set of organic-rich shale was deposited in a warm and humid paleoclimate setting. Extreme organic matter enrichment in study area may be attributed to ultra-high productivity (hypereutrophic lake), superimposed terrigenous organic matter input, and transgression, rather than volcanism and anoxic bottom water. This model is different from those of Chang 73 interval with higher organic matter content in the central and southern parts of the Ordos Basin. Therefore, this study proposes that the Chang 73 shale in the central Tianhuan Depression is not a good target layer for shale oil exploration and that the favorable area may be located in an undisturbed deep lake with higher organic matter abundance (e.g., southwestern Ordos Basin).

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Origin, transport, and diagenesis of tuffs in organic-rich lacustrine mudstone: An example from the lower part of the Middle–Late Triassic Chang7 Member, Ordos Basin (NW China)

Yong-ming¹,

Liu²,

Šegvić³

et al. 2023

Applied Clay Science

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Characteristics and controlling factors of LORS from the Chang 7–3 section of the Triassic Yanchang Formation in the Ordos Basin

Cited by 10 publications

References 30 publications

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

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

Extremely High Primary Productivity and Organic Matter Enrichment in Lacustrine Sediments: Late Triassic Chang 73 Sub-Member, Western Ordos Basin

Origin, transport, and diagenesis of tuffs in organic-rich lacustrine mudstone: An example from the lower part of the Middle–Late Triassic Chang7 Member, Ordos Basin (NW China)

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