Pyrite morphology in the first member of the Late Cretaceous Qingshankou Formation, Songliao Basin, Northeast China

Wang, Pingkang; Huang, Yongjian; Wang, Chengshan; Feng, Zihui; Huang, Qinghua

doi:10.1016/j.palaeo.2012.09.027

Cited by 67 publications

(25 citation statements)

References 30 publications

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“…The euhedral pyrites, pyritic masses, infilled framboids, overgrown framboids, polyframboid aggregates and stratiform pyrites are formed during the diagenetic stage with more positive δ 34 S values [32][33][34]. (b) formation mechanism of early diagenetic pyrites under the oxic-dysoxic depositional conditions [22]; (c) formation mechanism of late diagenetic pyrites in the deep burial stage.…”

Section: Introductionmentioning

confidence: 99%

“…As a widely distributed mineral in marine shales [13,20], pyrite can be divided into syngenetic pyrite and diagenetic pyrite. Syngenetic pyrites are formed at the oxic-anoxic interface and then drop to the sediment surface when buoyancy cannot keep them suspended ( Figure 1a) [13,21,22]. The framboid is generally considered to be the unique structural feature of syngenetic pyrite [13,23,24].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, syngenetic pyrite can be used to reflect the redox process of shale in a sedimentary water environment [13,25,26]. According to the different formation mechanisms of diagenetic pyrite, early diagenetic pyrites are formed in the sediments' porewater when the location of the oxic-anoxic interface falls down to the sediment (the diameter of an early diagenetic framboid is larger than 5 µm with a broad size distribution) ( Figure 1b) [13,22,25,26]. With the burial of sediment, the microcrystals of the early diagenetic pyrites will over grow by the reaction between Fe and S from the porewater (Figure 1b).…”

Section: Introductionmentioning

confidence: 99%

“…This method could be used in an area with apparently variable framboid sizes. For example, the diameter of framboids varies broadly, ranging from 3 µm to 25 µm in the Late Cretaceous Qingshankou formation, Songliao Basin, Northeast China [22]. The size of the pyrite framboids is classified as presenting two populations, framboids < 15 µm and framboids in the range 60-220 µm in the Toarcian Oceanic Anoxic Event, South Iberian Paleomargin [17].…”

Section: Introductionmentioning

confidence: 99%

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Pyrite Morphology as an Indicator of Paleoredox Conditions and Shale Gas Content of the Longmaxi and Wufeng Shales in the Middle Yangtze Area, South China

et al. 2019

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Pyrite is the most common authigenic mineral preserved in many ancient sedimentary rocks. Pyrite also widely exists in the Longmaxi and Wufeng marine shales in the middle Yangtze area in South China. The Longmaxi and Wufeng shales were mainly discovered with 3 types of pyrites: pyrite framboids, euhedral pyrites and infilled framboids. Euhedral pyrites (Py4) and infilled framboids (Py5) belong to the diagenetic pyrites. Based on the formation mechanism of pyrites, the pyrites could be divided into syngenetic pyrites, early diagenetic pyrites, and late diagenetic pyrites. Under a scanning electron microscope (SEM), the syngenetic pyrites are mostly small framboids composed of small microcrystals, but the diagenetic pyrites are variable in shapes and the diagenetic framboids are variable in sizes with large microcrystals. Due to the deep burial stage, the pore space in the sediment was sharply reduced and the diameter of the late diagenetic framboids that formed in the pore space is similar to the diameter of the syngenetic framboids. However, the diameter of the syngenetic framboid microcrystals is suggested to range mainly from 0.3 µm to 0.4 µm, and that of the diagenetic framboid microcrystals is larger than 0.4 µm in the study area. According to the diameter of the pyrite framboids (D) and the diameter of the framboid microcrystals (d), the pyrite framboids could be divided into 3 sizes: syngenetic framboids (Py1, D < 5 µm, d ≤ 0.4 µm), early diagenetic framboids (Py2, D > 5 µm, d > 0.4 µm) and late diagenetic framboids (Py3, D < 5 µm, d > 0.4 µm). Additionally, the mean size and standard deviation/skewness values of the populations of pyrite framboids were used to distinguish the paleoredox conditions during the sedimentary stage. In the study area, most of the pyrite framboids are smaller than 5 µm, indicating the sedimentary water body was a euxinic environment. However, pyrite framboids larger than 5 µm in the shales indicated that the sedimentary water body transformed to an oxic-dysoxic environment with relatively low total organic carbon (TOC: 0.4–0.99%). Furthermore, the size of the framboid microcrystals could be used to estimate the gas content due to thermochemical sulfate reduction (TSR). The process of TSR occurs with oxidation of organic matter (OM) and depletes the H bond of the OM, which will influence the amount of alkane gas produced from the organic matter during the thermal evolution. Thus, syngenetic pyrites (d ranges from 0.35 µm to 0.37 µm) occupy the main proportion of pyrites in the Wufeng shales with high gas content (1.30–2.30 m3/t), but the Longmaxi shales (d ranges from 0.35 µm to 0.72 µm) with a relatively low gas content (0.07–0.93 m3/t) contain diagenetic pyrites. Because of TSR, the increasing size of the microcrystals may result in an increase in the value of δ13C1 and a decrease in the value of δ13C1-δ13C2. Consequently, the size of pyrite framboids and microcrystals could be widely used for rapid evaluation of the paleoredox conditions and the gas content in shales.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pyrite Morphology as an Indicator of Paleoredox Conditions and Shale Gas Content of the Longmaxi and Wufeng Shales in the Middle Yangtze Area, South China

et al. 2019

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“…Pyrite framboids are densely packed, generally spherical aggregates of uniform-sized euhedral microcrystals that have cubic, pyritohedral, octahedral, or spherulitic shapes (Wilkin et al, 1996;Wang et al, 2013). Framboids and euhedral crystals are the two dominant textural forms of pyrite in modern sediments as well as in ancient sedimentary rocks.…”

Section: Introductionmentioning

confidence: 99%

Enhanced framboidal pyrite formation related to anaerobic oxidation of methane in the sulfate-methane transition zone of the northern South China Sea

Wang

Algeo

et al. 2016

Marine Geology

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Sequence stratigraphy in post‐rift river‐dominated lacustrine delta deposits: A case study from the Upper Cretaceous Qingshankou Formation, northern Songliao Basin, northeastern China

et al. 2020

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The Upper Cretaceous Qingshankou Formation in the northern Songliao Basin was deposited in river‐dominated lacustrine delta systems. Three third‐order sequences and two types of sequence architecture were recognized using core observations, logging curve interpretations, and three‐dimensional (3‐D) seismic profiles in Qingshankou Formation. One type of sequence architecture was developed in a syndepositional flexural slope break, and the other was deposited on a gentle slope. The studied sequences were deposited in a high accommodation setting, which was due to the large rate of subsidence of the basin basement, and a tropical to semi‐tropical and a humid to semi‐humid climate. The episodic tectonic/thermal subsidence of the basin controlled the development of the sequence architecture. Turbidite bodies within transgressive systems tracts and early highstand systems tracts were deposited predominantly in the basinward part of the syndepositional flexural slope breaks, and they were favourable exploration targets, particularly for stratigraphic traps.

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Pyrite morphology in the first member of the Late Cretaceous Qingshankou Formation, Songliao Basin, Northeast China

Cited by 67 publications

References 30 publications

Pyrite Morphology as an Indicator of Paleoredox Conditions and Shale Gas Content of the Longmaxi and Wufeng Shales in the Middle Yangtze Area, South China

Pyrite Morphology as an Indicator of Paleoredox Conditions and Shale Gas Content of the Longmaxi and Wufeng Shales in the Middle Yangtze Area, South China

Enhanced framboidal pyrite formation related to anaerobic oxidation of methane in the sulfate-methane transition zone of the northern South China Sea

Sequence stratigraphy in post‐rift river‐dominated lacustrine delta deposits: A case study from the Upper Cretaceous Qingshankou Formation, northern Songliao Basin, northeastern China

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