Carbonatites in oceanic hotspots
- Creators
- Schmidt, Max W.
- Weidendorfer, Daniel
Abstract
An analysis of the global array of ocean island volcanics shows that carbonatites only form in those hotspots that have the lowest Si- and highest alkali-contents among their primitive melts, such as the Cape Verde and Canary (Islands) hotspots. Fractionated melts from these two hotspots reach, at any given SiO_2, several wt% higher total alkali contents than for ocean islands without carbonatites. This is because their strongly silica-undersaturated primitive melts fractionate at low SiO_2 to high alkali contents, driving the evolving melt into the silicate-carbonatite miscibility gap. Instead, moderately alkaline magmas fractionate toward the alkali-feldspar thermal divide and do not reach liquid immiscibility. Low SiO_2 and high alkalis are the combined result of comparatively deep and low-degree mantle melting, the latter is corroborated by the highest high-field-strength and rare earth element concentrations in the Cape Verde and Canary primitive melts. CO_2 in the source facilitates low melt SiO_2, but enrichment in CO_2 relative to other hotspots is not required. The oceanic hotspots with carbonatites are among those with the thickest thermal lithosphere supporting a deep origin of their asthenospheric parent melts, an argument that could be expanded to continental hotspot settings.
Additional Information
© 2018 Geological Society of America. Manuscript received 15 August 2017; Revised manuscript received 16 February 2018; Manuscript accepted 16 February 2018. We acknowledge ETH grant 34–11–1 and Swiss National Science Foundation grant P2EZP2_162274. Peter Ulmer and Oli Jagoutz are thanked for discussionsAttached Files
Supplemental Material - 2018136.pdf
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Additional details
- Eprint ID
- 85039
- DOI
- 10.1130/G39621.1
- Resolver ID
- CaltechAUTHORS:20180301-110809197
- 34-11-1
- ETH Zurich
- P2EZP2_162274
- Swiss National Science Foundation (SNSF)
- Created
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2018-03-01Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field