Garnet-controlled very low velocities in the lower mantle transition zone at sites of mantle upwelling

Nagel, Thorsten J.; Duesterhoeft, Erik; Schiffer, Christian

Abstract

Deep mantle plumes and associated increased geotherms are expected to cause an upward deflection of the lower–upper mantle boundary and an overall thinning of the mantle transition zone between about 410 and 660 kilometres depth. We use subsequent forward modelling of mineral assemblages, seismic velocities and receiver functions to explain the common paucity of such observations in receiver function data. In the lower mantle transition zone, large horizontal differences in seismic velocities may result from temperature‐dependent assemblage variations. At this depth, primitive mantle compositions are dominated by majoritic garnet at high temperatures. Associated seismic velocities are expected to be much lower than for ringwoodite‐rich assemblages at undisturbed thermal conditions. Neglecting this ultra‐low‐velocity zone at upwelling sites can cause a miscalculation of the lower–upper mantle boundary on the order of 20 kilometres.

Citation

Nagel, T. J., Duesterhoeft, E., & Schiffer, C. (2018). Garnet-controlled very low velocities in the lower mantle transition zone at sites of mantle upwelling. Terra Nova, 30(5), 333-340. https://doi.org/10.1111/ter.12348

• Journal Article Type: Article
• Acceptance Date: Jul 1, 2018
• Online Publication Date: Jul 30, 2018
• Publication Date: Oct 1, 2018
• Deposit Date: Jul 10, 2018
• Publicly Available Date: Jul 30, 2019
• Journal: Terra Nova
• Print ISSN: 0954-4879
• Electronic ISSN: 1365-3121
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 30
• Issue: 5
• Pages: 333-340
• DOI: https://doi.org/10.1111/ter.12348
• Public URL: https://durham-repository.worktribe.com/output/1321900