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Systematics of halogen elements and their radioisotopes in thermal springs of the Cascade Range, Central Oregon, Western USA

Earth and Planetary Science Letters
By: , , , and 
https://doi.org/10.1016/j.epsl.2005.04.029

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Abstract

This study quantifies the cycling of halogen elements through the Cascadia subduction zone based on the chemistry of thermal springs in the Central Oregon Cascade Range and of a mineral spring in the forearc (Willamette Valley). Considerations based on mass balances, element ratios, and 36Cl/Cl and 129I/I ratios suggest that halogens discharged through the thermal springs in the Cascade Range are probably derived from magma degassing. Our results indicate that < 35% of the subducted Cl and < 20% of the subducted Br and I could be transported through arc volcanism and the thermal springs, a considerably lower percentage than estimated for other volcanic arcs along the Pacific Rim. A likely explanation for this difference is that a large fraction of the halogens is released from the slab at shallow depths into the serpentinized sub-forearc mantle because of the relatively high temperatures in the subducting Juan de Fuca plate. The small fraction of halogens subducted to depth probably also indicates a low rate of water transport, which is consistent with the observation that the Cascade Range sub-arc mantle is relatively dry and has a low degree of volcanic vigor, compared with other arcs.

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Publication type Article
Publication Subtype Journal Article
Title Systematics of halogen elements and their radioisotopes in thermal springs of the Cascade Range, Central Oregon, Western USA
Series title Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2005.04.029
Volume 235
Issue 3-4
Year Published 2005
Language English
Publisher Elsevier
Description 15 p.
First page 700
Last page 714
Country United States
State Oregon
Other Geospatial Cascade Range
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