Hydrothermal activities and seawater acidification in the Late Devonian F-F transition: Evidence from geochemistry of rare earth elements

Abstract

Rare-earth elements (REE) in limestones were measured by ICP-MS from the Yangdi section across the Frasnian-Famennian (F-F) transition in Guilin, Guangxi of South China. The average ΣREE contents of measured samples are 33.32 ppm. The average LREE/HREE ratio is 6.35. Data show LREE-enriched REE distribution pattern in the Yangdi section. Most of samples are characterized by positive Eu anomaly with average of 1.13, and there are two maxima of Eu anomaly just below the F-F boundary. Almost all analytical samples show obvious tetrad effects. Remarkable M-shaped tetrad effects are observed in these samples with positive Eu anomaly. The characters of REE and some relative elements (Fe, Mn, Al, etc.) indicate that hydrothermal activities occurred and resulted in seawater acidification in Upper and Lower Kellwasser horizons of the Late Devonian. The changes of marine environment caused by hydrothermal activities, such as seawater acidification, heavy metal pollution, and eutrophication, would destroy the neritic ecosystem and finally result in the F-F mass extinction. Devonian, mass extinction, REE, hydrothermal activities, tetrad effects, seawater acidification Citation:Zeng J W, Xu R, Gong X M. Hydrothermal activities and seawater acidification in the Late Devonian F-F transition: Evidence from geochemistry of rare earth elements.

Carbon isotopic evidence for the associations of decreasing atmospheric CO2level with the Frasnian‐Famennian mass extinction

“…The cause of this bioevent remains a subject of intensive debate with both external (bolide impact) and internal (e.g., increased hydrothermal‐volcanic activities, climate changes) mechanisms invoked [ McGhee , 1996; Racki , 2005]. Most mechanisms are involved in a δ 13 C carb positive excursion around the F‐F boundary [ McGhee , 1996; Joachimski et al , 2002; Ma and Bai , 2002; Racki et al , 2002; Goddéris and Joachimski , 2004; Riquier et al , 2006; van Geldern et al , 2006; Xu et al , 2008; John et al , 2010; Zeng et al , 2011]. The δ 13 C carb positive excursion, together with organic rich horizons known as the Upper Kellwasser horizons in biostratigraphy [ Schindler , 1990; Walliser , 1996], is interpreted as the result of increased carbon burial [ McGhee et al , 1986; Joachimski et al , 2002 ; Ma and Bai , 2002; Racki et al , 2002; Xu et al , 2008].…”

The coal-forming environment during mass extinction in the latest permian: Evidence from geochemistry of rare Earth elements

“…As a special organic sedimentary rock, coal may also be affected by the abovementioned factors during the coal-forming process, which could affect REEs fractionation and enrichment. For instance, δCe value easily changes due to diagenesis, which then leads to a significantly positive correlation between δCe and δEu, a significantly negative correlation between δCe and (Dy/Sm) N , and a significantly positive correlation between δCe and REE (Shields et al, 2001;Zeng et al, 2011;Qu et al, 2018). To confirm the influence of diagenesis on samples from seam C 1 , the above three correlation coefficients are calculated as -0.10, 0.15 and 0.18, respectively (Figure 4).…”

Lipid biomarkers recording marine microbial community structure changes through the Frasnian‐Famennian mass extinction event

“…The extrinsic causal mechanism for the mass extinction remains a topic of ongoing debate, with rapid afforestation, volcanism, global cooling, and transgression among the most speculated triggers (Algeo et al, 1995;Bond & Wignall, 2008;Joachimski & Buggisch, 2002;Lu et al, 2019;Racki et al, 2018). Ongoing discussion also continues around the direct kill mechanism, bringing forward multiple hypotheses such as sulfide poisoning (Chen et al, 2013) and ocean acidification (Kabanov et al, 2023;Zeng et al, 2011). However, there is a broad consensus that the Late Devonian marine environment is overall reducing, leading to prolonged oxygen stress that is considered to be a significant contributing factor to taxonomic and ecological turnovers of marine organisms (Boyer et al, 2021;Carmichael et al, 2019;Lu, Lu, Ikejiri, Sun, et al, 2021).…”