Surprises from the top of the mantle transition zone

Journal article


Rollinson, Hugh 2016. Surprises from the top of the mantle transition zone. Geology Today. https://doi.org/10.1111/gto.12130
AuthorsRollinson, Hugh
Abstract

Recent studies of chromite deposits from the mantle section of ophiolites have revealed a most unusual collection of minerals present as inclusions within the chromite. The initial discoveries were of diamonds from the Luobosa ophiolite in Tibet. Further work has shown that mantle chromitites from ophiolites in Tibet, the Russian Urals and Oman contain a range of crustal minerals including zircon, and a suite of highly reducing minerals including carbides, nitrides and metal alloys. Some of the minerals found represent very high pressure phases indicating that their likely minimum depth is close to the top of the mantle transition zone. These new results suggest that crustal materials may be subducted to mantle transition zone depths and subsequently exhumed during the initiation of new subduction zones—the most likely environment for the formation of their host ophiolites. The presence of highly reducing phases indicates that at mantle transition zone depths the Earth’s mantle is ‘super’-reducing.

Recent studies of chromite deposits from the mantle section of ophiolites
have revealed a most unusual collection of minerals present as inclusions
within the chromite. The initial discoveries were of diamonds from the
Luobosa ophiolite in Tibet. Further work has shown that mantle chromitites
from ophiolites in Tibet, the Russian Urals and Oman contain a range of
crustal minerals including zircon, and a suite of highly reducing minerals
including carbides, nitrides and metal alloys. Some of the minerals found
represent very high pressure phases indicating that their likely minimum
depth is close to the top of the mantle transition zone. These new results
suggest that crustal materials may be subducted to mantle transition zone
depths and subsequently exhumed during the initiation of new subduction
zones—the most likely environment for the formation of their host ophiolites.
The presence of highly reducing phases indicates that at mantle transition
zone depths the Earth’s mantle is ‘super’-reducing.

KeywordsMantle transition zone; Chromite
Year2016
JournalGeology Today
PublisherWiley Blackwell
ISSN2666979
Digital Object Identifier (DOI)https://doi.org/10.1111/gto.12130
Web address (URL)http://hdl.handle.net/10545/621588
hdl:10545/621588
Publication dates07 Mar 2016
Publication process dates
Deposited09 May 2017, 14:48
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ContributorsUniversity of Derby and University of Derby; Kedleston Road Derby DE22 1GB UK
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