Diagenetic barite-calcite-pyrite nodules in the Silurian Longmaxi Formation of the Yangtze Block, South China: A plausible record of sulfate-methane transition zone movements in ancient marine sediments

Zan, Bowen; Mou, Chuanlong; Lash, Gary G.; Yan, Jiaxin; Hou, Qian

doi:10.1016/j.chemgeo.2022.120789

Cited by 6 publications

(4 citation statements)

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“…Therefore, these evidences indicated that Ba in barite may be from seawater with hydrothermal activity ( [65,67], Figure 12). Moreover, the δ 34 S value of barites filling fractures of low-resistivity shale samples ranges from 19.8 ‰ to 24.6 ‰, lower than Early Silurian seawater [35]. Therefore, the δ 34 S‰ values of barites may be attributed to seawater mixed with hydrothermal fluids.…”

Section: Sulfatization Stagementioning

confidence: 94%

“…The test error was less than 1%. The specific sample handling process in this study followed Zan's steps [35].…”

Section: Elementary Geochemistry Analysismentioning

confidence: 99%

“…It is frequently considered an indicator of hydrothermal activity [62,68] because of its co-existence with barium-enriched hydrothermal fluids. A comparison of hyalophane from the Longmaxi low-resistivity shale and typical hydrothermal fluids in the world shows that they are similar in major elements (Figure 14, [35,46,62,63,68]). The existence of hyalophane has been believed to be related to the hydrothermally induced diagenetic transformation of K-feldspar, based on previous investigations on the relationship between hyalophane and surrounding minerals in ore deposits [35,65].…”

Section: Feldspathisation Stagementioning

confidence: 99%

“…A comparison of hyalophane from the Longmaxi low-resistivity shale and typical hydrothermal fluids in the world shows that they are similar in major elements (Figure 14, [35,46,62,63,68]). The existence of hyalophane has been believed to be related to the hydrothermally induced diagenetic transformation of K-feldspar, based on previous investigations on the relationship between hyalophane and surrounding minerals in ore deposits [35,65]. For instance, Zan observed the close relationship between hyalophane, K-feldspar, and barite at nodules and black shales of the Longmaxi Formation in the Northern Sichuan Basin, and they hypothesized that K-feldspar had been largely replaced by hydrothermal Ba 2+ with the following reaction [65]:…”

Section: Feldspathisation Stagementioning

confidence: 99%

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Influence of Low-Temperature Hydrothermal Events and Basement Fault System on Low-Resistivity Shale Reservoirs: A Case Study from the Upper Ordovician to Lower Silurian in the Sichuan Basin, SW China

Zhou,

Cai,

Mou

et al. 2023

Minerals

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High graphitization is responsible for low-resistivity shale development with poor reservoir quality. This paper provides an explanation of organic matter graphitization and determines the impact of high graphite content on low-resistivity shale reservoir quality at the Wufeng-Longmaxi Formation in the Southern Sichuan Basin. Fine veins are frequently developed at shale samples with Ro > 3.5%, graphitized organic matter > 25%, and resistivity < 5 Ω•m, which are dominated by three mineral assemblages: brunsvigite, barite-hyalophane-barium feldspar-potassium feldspar-anhydrite, and calcite-ankerite. These filling minerals are characterized by an Eu positive anomaly and high Ba, Fe, and Mn contents, suggesting that low-resistivity shale was modified by magmatic-related low-temperature hydrothermal fluid. Temperature measurements of brine inclusions and a semi-empirical geothermometer of chlorite show that low-temperature hydrothermal fluid experienced the chlorite stage (150–180 °C), the low-sulfidation stage (120–150 °C), and the low-temperature calcitization stage. Paleozoic fault systems and late Permian hydrothermal activities associated with the Emeishan mantle plume control the graphitization of low-resistivity shale. The water formation and seawater infiltrated into the deep crust along the Paleozoic basement faults under gravity, developing alkaline hot brine through mantle plume heating and then causing a water-rock reaction with basement rocks. They migrated upward along deep and large Paleozoic faults through convective thermal circulation in the Tiangongtang area, the Shuanglong-Luochang area, and the Xuyong area. Cation exchange and redox reactions occurred during the interaction between high-temperature hydrothermal fluid and cool wall rocks. The migration of alkaline hot brine via the Wufeng-Longmaxi shale introduced a subsequent water-rock reaction, resulting in the development of hydrothermal mineral assemblages that intricately filled fractures. It increased formation temperature and enhanced thermal maturity and graphitization of organic matter at the Wufeng-Longmaxi low-resistivity shale, resulting in a wide distribution of low-resistivity shale at the Changning Block.

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Section: Sulfatization Stagementioning

confidence: 94%

“…The test error was less than 1%. The specific sample handling process in this study followed Zan's steps [35].…”

Section: Elementary Geochemistry Analysismentioning

confidence: 99%