Schmidt, Max W. and Weidendorfer, Daniel (2018) Carbonatites in oceanic hotspots. Geology, 46 (5). pp. 435-438. ISSN 0091-7613. doi:10.1130/G39621.1. https://resolver.caltech.edu/CaltechAUTHORS:20180301-110809197
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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.
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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 discussions | ||||||||||||
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Issue or Number: | 5 | ||||||||||||
DOI: | 10.1130/G39621.1 | ||||||||||||
Record Number: | CaltechAUTHORS:20180301-110809197 | ||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20180301-110809197 | ||||||||||||
Official Citation: | Max W. Schmidt, Daniel Weidendorfer; Carbonatites in oceanic hotspots. Geology ; 46 (5): 435–438. doi: https://doi.org/10.1130/G39621.1 | ||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||
ID Code: | 85039 | ||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||
Deposited By: | Tony Diaz | ||||||||||||
Deposited On: | 01 Mar 2018 20:19 | ||||||||||||
Last Modified: | 15 Nov 2021 20:25 |
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