Slab window related magmatism as a probe for pyroxenite heterogeneities in the upper mantle

Malcolm Hole; Sally Gibson; Matthew Morris

doi:10.1130/G50687.1

Slab window related magmatism as a probe for pyroxenite heterogeneities in the upper mantle

Malcolm Hole, Sally Gibson, Matthew Morris

Geology and Geophysics

University of Cambridge

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

6 Downloads (Pure)

Abstract

New high-precision trace-element analyses of magmatic olivines point to a pyroxenite-dominated source for recent alkali basalts erupted above slab windows formed along the Antarctic Peninsula. Melting occurred at ambient mantle temperature and basalts have geochemical compositions that are indistinguishable from Ocean Island Basalts (OIB). We propose that the pyroxenite component originally resided in the upper mantle beneath the subducted slab; formation of a slab window allowed limited decompression and the generation of melts of garnet-pyroxenite, but little or no melting of mantle peridotite. The pyroxenite component in the mantle formed at ~550 Ma, an age that does not require long-term recycling of subducting slabs to the core-mantle boundary. E-MORB (mid-ocean ridge basalt) from the adjacent extinct Phoenix Ridge owes its enriched trace element compositions to mixing between small melt fractions of pyroxenite and peridotite during a period of decreased spreading rate prior to the death of the ridge at ~3.3Ma. It is likely that the variable trace-element enrichment seen in East Pacific Rise E-MORB distal from hotspots results from the same process of interactions between small melt fraction (

Original language	English
Pages (from-to)	268-272
Number of pages	5
Journal	Geology
Volume	51
Issue number	3
Early online date	20 Jan 2023
DOIs	https://doi.org/10.1130/G50687.1
Publication status	E-pub ahead of print - 20 Jan 2023

Bibliographical note

We are grateful to Rob Clarke for making the thin sections, and Iris Buisman and Jason Day for assistance with electron microprobe and LA-ICP-MS. The manuscript was improved by the comments of Derek Thorkelson and an anonymous reviewer.

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10.1130/G50687.1Licence: CC BY

Hole_etal_G_Slab_Window_Related_VoR
© 2023 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license https://creativecommons.org/licenses/by/4.0/
Final published version, 1.55 MBLicence: CC BY

Cite this

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title = "Slab window related magmatism as a probe for pyroxenite heterogeneities in the upper mantle",

abstract = "New high-precision trace-element analyses of magmatic olivines point to a pyroxenite-dominated source for recent alkali basalts erupted above slab windows formed along the Antarctic Peninsula. Melting occurred at ambient mantle temperature and basalts have geochemical compositions that are indistinguishable from Ocean Island Basalts (OIB). We propose that the pyroxenite component originally resided in the upper mantle beneath the subducted slab; formation of a slab window allowed limited decompression and the generation of melts of garnet-pyroxenite, but little or no melting of mantle peridotite. The pyroxenite component in the mantle formed at ~550 Ma, an age that does not require long-term recycling of subducting slabs to the core-mantle boundary. E-MORB (mid-ocean ridge basalt) from the adjacent extinct Phoenix Ridge owes its enriched trace element compositions to mixing between small melt fractions of pyroxenite and peridotite during a period of decreased spreading rate prior to the death of the ridge at ~3.3Ma. It is likely that the variable trace-element enrichment seen in East Pacific Rise E-MORB distal from hotspots results from the same process of interactions between small melt fraction (",

author = "Malcolm Hole and Sally Gibson and Matthew Morris",

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AU - Hole, Malcolm

AU - Gibson, Sally

AU - Morris, Matthew

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N2 - New high-precision trace-element analyses of magmatic olivines point to a pyroxenite-dominated source for recent alkali basalts erupted above slab windows formed along the Antarctic Peninsula. Melting occurred at ambient mantle temperature and basalts have geochemical compositions that are indistinguishable from Ocean Island Basalts (OIB). We propose that the pyroxenite component originally resided in the upper mantle beneath the subducted slab; formation of a slab window allowed limited decompression and the generation of melts of garnet-pyroxenite, but little or no melting of mantle peridotite. The pyroxenite component in the mantle formed at ~550 Ma, an age that does not require long-term recycling of subducting slabs to the core-mantle boundary. E-MORB (mid-ocean ridge basalt) from the adjacent extinct Phoenix Ridge owes its enriched trace element compositions to mixing between small melt fractions of pyroxenite and peridotite during a period of decreased spreading rate prior to the death of the ridge at ~3.3Ma. It is likely that the variable trace-element enrichment seen in East Pacific Rise E-MORB distal from hotspots results from the same process of interactions between small melt fraction (

AB - New high-precision trace-element analyses of magmatic olivines point to a pyroxenite-dominated source for recent alkali basalts erupted above slab windows formed along the Antarctic Peninsula. Melting occurred at ambient mantle temperature and basalts have geochemical compositions that are indistinguishable from Ocean Island Basalts (OIB). We propose that the pyroxenite component originally resided in the upper mantle beneath the subducted slab; formation of a slab window allowed limited decompression and the generation of melts of garnet-pyroxenite, but little or no melting of mantle peridotite. The pyroxenite component in the mantle formed at ~550 Ma, an age that does not require long-term recycling of subducting slabs to the core-mantle boundary. E-MORB (mid-ocean ridge basalt) from the adjacent extinct Phoenix Ridge owes its enriched trace element compositions to mixing between small melt fractions of pyroxenite and peridotite during a period of decreased spreading rate prior to the death of the ridge at ~3.3Ma. It is likely that the variable trace-element enrichment seen in East Pacific Rise E-MORB distal from hotspots results from the same process of interactions between small melt fraction (

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DO - 10.1130/G50687.1

M3 - Article

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JO - Geology

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ER -

Slab window related magmatism as a probe for pyroxenite heterogeneities in the upper mantle

Abstract

Bibliographical note

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