Volatiles in Basaltic Glasses from the Easter‐Salas y Gomez Seamount Chain and Easter Microplate: Implications for Geochemical Cycling of Volatile Elements

Authors

Kyla Simons, University of Miami
Jacqueline Dixon, University of MiamiFollow
Jean‐Guy Schilling, University of Rhode Island
Richard Kingsley, University of Rhode Island
Robert Poreda, University of Rochester

Document Type

Article

Publication Date

7-2002

Keywords

Easter, mantle plume, volatiles, water, chlorine, basalt

Digital Object Identifier (DOI)

https://doi.org/10.1029/2001GC000173

Abstract

We present H₂O, CO₂, and Cl concentrations in 66 basaltic glasses from the Easter Microplate (EMP) and Easter‐Salas y Gomez Seamount Chain (ESC) system in the southeastern Pacific. The EMP‐ESC system is characterized by binary mixing between a depleted mid‐ocean ridge basalt (MORB) mantle source (DMM) and an incompatible element and radiogenic isotope enriched source, the Salas y Gomez mantle plume (SyG). Plume material is channeled toward the ridge crest centered at ∼27°S on the east rift of the microplate. Water concentrations on the EMP are highest on the east rift at ∼27°S and become progressively lower to the north and south, following the spatial pattern of other geochemical tracers. EMP basalts have not lost H₂O to degassing but have assimilated variable quantities of a Cl‐rich hydrothermal component. In contrast, some seamount basalts have lost water by shallow degassing, but very few have gained Cl, indicating little assimilation of Cl‐rich materials. Several ESC seamount glasses may have assimilated a hydrous component, for example, serpentinized harzburgite, during magma ascent through the lithosphere. On the basis of samples unaffected by shallow processes, the main plume component has H₂O/Ce of ∼210 ± 20 and is neither preferentially enriched nor depleted in H₂O relative to other similarly incompatible elements. The depleted MORB source has H₂O/Ce of ∼150 ± 10. Estimated mantle volatile concentrations are 750 ± 210 ppm H₂O and 40 ± 11 ppm Cl for the SyG source, 120 ± 27 ppm H₂O and 4.5 ± 1.4 ppm Cl for an average EPR source, and 54 ± 12 ppm H₂O and 1.7 ± 0.4 ppm Cl for the DMM source. The coupled behavior of H₂O and Cl with similarly incompatible elements, coupled with elevated ³He/⁴He ratios, suggests that the volatiles are dominantly juvenile, representative of a component common to mantle plumes, with minor contribution from recycled lithospheric components.

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Citation / Publisher Attribution

Geochemistry, Geophysics, Geosystems, v. 3, issue 7, p. 1-29

Copyright 2002 by the American Geophysical Union.

Scholar Commons Citation

Simons, Kyla; Dixon, Jacqueline; Schilling, Jean‐Guy; Kingsley, Richard; and Poreda, Robert, "Volatiles in Basaltic Glasses from the Easter‐Salas y Gomez Seamount Chain and Easter Microplate: Implications for Geochemical Cycling of Volatile Elements" (2002). Marine Science Faculty Publications. 1326.
https://digitalcommons.usf.edu/msc_facpub/1326