The content discusses the geochemical analysis of the 2021 and 2022 Fagradalsfjall eruptions in Iceland. The key insights are:
The earliest 2021 Fagradalsfjall lavas show highly anomalous osmium (Os) isotope ratios (187Os/188Os ≤ 0.188) and platinum (Pt)/iridium (Ir) ratios (≤ 76), indicating significant crustal contamination, likely from mid-ocean-ridge gabbros and older basalts underlying the Reykjanes Peninsula.
The elevated Os isotope ratios persisted throughout the 2021 eruption, suggesting a continued but diluted presence of crustal contaminants.
In contrast, the 2022 Fagradalsfjall lavas showed no evidence of crustal assimilation, with Os isotope ratios (187Os/188Os = 0.131) and Pt/Ir ratios (30) typical of Icelandic basalts.
The authors propose that the initiation of the 2021 Fagradalsfjall eruptions involved pre-eruptive stalling, fractional crystallization, and crustal assimilation of the earliest lavas. However, an established magmatic conduit system in 2022 enabled efficient magma transit to the surface without significant crustal contamination.
The study demonstrates the value of time-series geochemical analysis of active basaltic eruptions, which can provide insights into mantle composition and eruption processes.
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by James M. D. ... 於 www.nature.com 07-31-2024
https://www.nature.com/articles/s41586-024-07750-0深入探究