Mercury record of intense hydrothermal activity during the early Cambrian, South China

Zhu, Guangyou; Wang, Pengju; Li, Tingting; Zhao, Kun; Zheng, Wang; Feng, Xinbin; Shen, Jun; Grasby, Stephen E.; Sun, Guangyi; Tang, Shunlin; H, Yan

doi:10.1016/j.palaeo.2021.110294

Cited by 19 publications

(10 citation statements)

References 45 publications

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“…As a result, the contents of these elements in the sediments will be abnormally and radially distributed around the center of the hydrothermal fluid input channel. Thus, anomalous abundances of these elements are one of the most important geochemical characteristics of hydrothermal sediments and can be used to distinguish between hydrothermal sediments and normal sediments [26,[54][55][56]. In contrast to normal sediments, hydrothermal sediments are generally enriched in elements such as Si, Mn, P, Pb, Zn, Cu, Ba, Fe, Sr, and U, while they are depleted in elements such as Al, Ti, Mg, Cr, Th, Zr, and Rb.…”

Section: Hydrothermal Influencesmentioning

confidence: 99%

Depositional Environment and Organic Matter Enrichment of Early Cambrian Niutitang Black Shales in the Upper Yangtze Region, China

et al. 2022

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Natural gas generation is the result of organic matter degradation under the effects of biodegradation and thermal degradation. Early Cambrian black shales in the Upper Yangtze Region are rich in organic matter and have shown great shale gas potentiality in recent years. Nevertheless, the enrichment mechanism and distribution of organic matter in these black shales between different sedimentary settings, such as intra-platform basin, slope, and deep basin, are still poorly understood. In this paper, based mainly on elemental geochemistry, a comprehensive study of the marine redox conditions, primary productivity, sedimentation rate, terrigenous input, hydrothermal activity, and water mass restrictions was conducted on the Early Cambrian Niutitang black shale in the Upper Yangtze Region. Our data showed that an intra-platform basin received a higher terrigenous input and that it deposited under more restricted conditions than the slope and deep basin settings. The primary productivity in the slope and deep basin settings was higher than that in the intra-platform basin setting. In the intra-platform basin, the productivity increased from its inner part to its margin. For the slope and deep basin settings, the high paleoproductivity generated large amounts of organic matter and its preservation was synergistically affected by the redox conditions. In contrast to the slope and deep basin, the preservation of organic matter in the inner part of the intra-platform basin was mainly controlled by redox conditions because the paleoproductivity in it was much lower than in the slope and deep basin settings. The intra-platform basin margin was the most favorable area for accumulating organic matter.

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Section: Hydrothermal Influencesmentioning

confidence: 99%

Depositional Environment and Organic Matter Enrichment of Early Cambrian Niutitang Black Shales in the Upper Yangtze Region, China

et al. 2022

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“…At the Precambrian-Cambrian boundary, it is accompanied by frequent dynamic changes in marine redox conditions, − the rapid fluctuation of δ 13 C carb , long-term positive δ 34 S sulfate excursion and instantaneous anomaly of δ 95/97 Mo all record the frequent changes of marine environment, , in response to the change of atmospheric-ocean oxygenation after the Snowball Earth event . Many studies on the characteristics of mercury isotopes, molybdenum isotopes and rare earth elements show that there is obvious chemical stratification in the marine water from Ediacaran to early Cambrian, and the increase of atmospheric oxygen content drives the regional oxidation of the shallow sea. ,− During this period, a large-scale marine phosphorite deposited around the world, including two important metallogenic periods, namely, the Ediacaran (635–541Ma) and the early Cambrian (541–529Ma), which is widely distributed in Asia, Australia, Africa, and other regions . During this period, phosphate mineralization is closely related to the global carbon cycle, two Neoproterozoic oxidation events, and biological evolution, so the geochemical characteristics and paleo-marine environment of marine phosphorites in this period are ideal objects for in-depth analysis of the original geochemical information on seawater and the influence of paleo-marine environment on phosphorus mineralization.…”

Section: Introductionmentioning

confidence: 99%

Geochemical Characteristics of Trace Elements and Mineralization Model of the Ediacaran-Early Cambrian Phosphorites, South China

Zhang,

Zhu

2024

ACS Omega

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As a nonrenewable resource, phosphate rock is an important support for the development and survival of the national economy. The regional distribution and output of phosphate rock in China are extremely uneven, and the amount of high-quality ore resources is relatively poor, which seriously restricts the development and utilization of phosphate rock resources in China. This paper briefly summarizes the distribution characteristics of phosphate rock resources and summarizes the characteristics and research progress of Ediacaran-early Cambrian phosphorus mineralization types, geological characteristics, and deposit genesis of the Yangtze platform in South China. The Ediacaran-early Cambrian sedimentary phosphorite deposits in China are mainly distributed in Yunnan, Guizhou, Hubei, Sichuan and Hunan provinces of the Yangtze platform, in which the early Cambrian phosphate deposits are also rich in rare earth elements, associated with uranium, nickel, molybdenum, vanadium, and other beneficial metal elements. The increase of atmospheric oxygen content at the Ediacaran-Cambrian boundary may have promoted the extensive oxygenation of the late Neoproterozoic oceans, so the Ediacaran-early Cambrian oceans generally showed a reductive environment, and there may be dynamic chemical stratification of the oxidation zone-sulfide zone-iron zone. Up to the early Cambrian, the redox stratified structure of Precambrian seawater may still be inherited, showing that the surface water is an oxidizing environment, changing to a reduction environment, and even wedge-shaped sulfide water is developed at the bottom of the deep basin. The main phosphorus sources are deep phosphorus-rich seawater, continental weathering, and deep hydrothermal activity of Ediacaran-early Cambrian marine sedimentary phosphorite deposits in South China. The genetic mechanisms of phosphorite deposits in the Yangtze platform in South China are mainly biogenic, upwelling phosphorus-forming theory, mechanical mineralization, and syn-sedimentary hot water mixed genesis. In the future, it is still necessary to further explore the internal relationship between phosphorus deposits and major geological events, the in situ analysis of microstructure of phosphate rock ores, and the genetic mechanism of phosphate deposits and the reconstruction of paleo-marine environment.

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“…THg enrichment is also found in sediments under the influence of hydrothermal fluids (Cox & McMurtry, 1981; Lamborg et al., 2006). Therefore, some of the elevated THg/TOC ratio in geological records are attributed to past hydrothermal input (Jin et al., 2023; Zhu et al., 2021). However, the spatial scale of hydrothermal influence on sedimentary THg/TOC ratios is poorly constrained.…”

Section: Introductionmentioning

confidence: 99%

Coupling and Decoupling Between Sedimentary Mercury and Organic Carbon Preservation in the Oxygenated Marine Environment

Qu,

Zhong,

Liu

et al. 2024

Geochem Geophys Geosyst

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Mercury (Hg) enrichment relative to total organic carbon (TOC) in sedimentary records has been widely used as a volcanism proxy. However, the depositional and diagenetic effects on Hg burial are not well understood, limiting the reliability of the proxy. Here, we report a systematic investigation of Hg sedimentation under well‐oxygenated bottom water. Most of the studied cores show total mercury content (THg) to TOC ratio between 50 and 300 ppb/%, including northwest Pacific ODP Site 1208, East Equatorial Pacific ODP Sites 677 and 1241, the Antarctic Zone ODP Site 1094, and East China Sea sediment core EC2005. The consistent THg/TOC ratio confirms the strong coupling between Hg and particulate organic matter (POM) despite large differences in geographic locations, sedimentation rates, TOC content, POM sources, and early diagenetic environments. Nevertheless, the THg/TOC ratio is higher in sediments under well‐oxygenated bottom water than in those under oxygen‐depleted waters, probably as a result of a higher degree of organic matter degradation in oxygenated sediments during early diagenesis. The THg in the high TOC variability section at Site 1208 is abnormally high, resulting in decoupling between Hg and POM. Mercury in this section is still leachable by oxidizing solution and has a similar trend of variability with easily reducible iron content, implying that the metal oxide‐organic matter association might act as Hg bounding phase. We suggest that the enriched Hg is probably supplied by the neighboring high TOC sediment. Therefore, while THg/TOC > 300 ppb/% could be considered as distinct Hg enrichment in sedimentary records, the diagenetic mobilization effect should be first excluded as the possible cause as demonstrated by the records of site 1208. Our study therefore provides new insights into the Hg cycle in the modern ocean and the utilization of Hg enrichment as a volcanism proxy.

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Mercury record of intense hydrothermal activity during the early Cambrian, South China

Cited by 19 publications

References 45 publications

Depositional Environment and Organic Matter Enrichment of Early Cambrian Niutitang Black Shales in the Upper Yangtze Region, China

Depositional Environment and Organic Matter Enrichment of Early Cambrian Niutitang Black Shales in the Upper Yangtze Region, China

Geochemical Characteristics of Trace Elements and Mineralization Model of the Ediacaran-Early Cambrian Phosphorites, South China

Coupling and Decoupling Between Sedimentary Mercury and Organic Carbon Preservation in the Oxygenated Marine Environment

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