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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. 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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1130/G39621.1DOIArticle
https://pubs.geoscienceworld.org/gsa/geology/article/529021/Carbonatites-in-oceanic-hotspotsPublisherArticle
http://www.geosociety.org/datarepository/2018/2018136.pdfRelated ItemData
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
Funders:
Funding AgencyGrant Number
ETH Zurich34-11-1
Swiss National Science Foundation (SNSF)P2EZP2_162274
Issue or Number:5
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:03 Oct 2019 19:26

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