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Carbonatites in oceanic hotspots

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.

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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
Funding AgencyGrant Number
ETH Zurich34-11-1
Swiss National Science Foundation (SNSF)P2EZP2_162274
Issue or Number:5
Record Number:CaltechAUTHORS:20180301-110809197
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Official Citation:Max W. Schmidt, Daniel Weidendorfer; Carbonatites in oceanic hotspots. Geology ; 46 (5): 435–438. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85039
Deposited By: Tony Diaz
Deposited On:01 Mar 2018 20:19
Last Modified:15 Nov 2021 20:25

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