Document Type

Article

Peer Reviewed

1

Publication Date

3-24-2017

Journal/Book/Conference Title

Scientific Reports

DOI of Published Version

10.1038/srep45186

Start Page

45186

Abstract

We present new ²³⁸U-²³⁰Th-²²⁶Ra-²¹⁰Pb and supporting data for young lavas from southwest Pacific island arcs, Eyjafjallajökull, Iceland, and Terceira, Azores. The arc lavas have significant ²³⁸U and ²²⁶Ra excesses, whereas those from the ocean islands have moderate ²³⁰Th and ²²⁶Ra excesses, reflecting mantle melting in the presence of a water-rich fluid in the former and mantle melting by decompression in the latter. Differentiation to erupted compositions in both settings appears to have taken no longer than a few millennia. Variations in the (²¹⁰Pb/²²⁶Ra)₀ values in all settings largely result from degassing processes rather than mineral-melt partitioning. Like most other ocean island basalts, the Terceira basalt has a ²¹⁰Pb deficit, which we attribute to ~8.5 years of steady ²²²Rn loss to a CO₂-rich volatile phase while it traversed the crust. Lavas erupted from water-laden magma systems, including those investigated here, commonly have near equilibrium (²¹⁰Pb/²²⁶Ra)₀ values. Maintaining these equilibrium values requires minimal persistent loss or accumulation of ²²²Rn in a gas phase. We infer that degassing during decompression of water-saturated magmas either causes these magmas to crystallize and stall in reservoirs where they reside under conditions of near stasis, or to quickly rise towards the surface and erupt.

Keywords

OAfund, 210Pb, 226Ra, basalt, andesite, dacite, rhyolite, U-series

Journal Article Version

Version of Record

Published Article/Book Citation

Scientific Reports volume 7, Article number: 45186 (2017) https://doi.org/10.1038/srep45186

Rights

© The Authors 2017

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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URL

https://ir.uiowa.edu/geology_pubs/249