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Open AccessArticle

The Formation of Dunite Channels within Harzburgite in the Wadi Tayin Massif, Oman Ophiolite: Insights from Compositional Variability of Cr-Spinel and Olivine in Holes BA1B and BA3A, Oman Drilling Project

1
Department of Earth Sciences, Università degli Studi di Milano, via Mangiagalli 34, 20133 Milan, Italy
2
Department of Applied Geological Sciences and Geophysics, University of Leoben, A-8700 Leoben, Austria
3
Dipartimento di Scienze della Terra dell'Ambiente e della Vita (DISTAV), University of Genova, Corso Europa, 26, I-16132 Genova, Italy
*
Author to whom correspondence should be addressed.
Oman Drilling Project Science Team: https://www.omandrilling.ac.uk.
Minerals 2020, 10(2), 167; https://doi.org/10.3390/min10020167
Received: 23 December 2019 / Revised: 3 February 2020 / Accepted: 5 February 2020 / Published: 13 February 2020
(This article belongs to the Special Issue Mineral Deposits Related to Mantle Rocks)
Holes BA1B and BA3A were drilled into the Wadi Tayin Massif, southern ophiolite complex of Oman, a fragment of the Tethyan oceanic lithosphere obducted onto the Arabian continent. Within the sequence, we have studied a portion of the shallow mantle, composed mainly of strongly serpentinised harzburgite that embeds dunitic levels, the biggest being over 150 m thick. The formation of thick dunitic channels, already approached via published structural and mathematical models, is here investigated with a mineral chemistry approach. We focused on Cr-spinel, the only widespread phase preserved during serpentinization, whose TiO2 content displays a wide variability from low in harzburgite, (TiO2 < 0.25 wt. %), typical of non-metasomatised ophiolite mantle, to moderately high in dunite (TiO2 < 1.10 wt. %) characterizing a rock/melt interactions. The high variability of TiO2, accompanied by similar patterns of Cr# and Mg# is observed, in a fractal pattern, at all scales of investigation, from the whole channel scale to the single thin section, where it affects even single grain zonings. Our results suggest that the over 150 m thick dunite channel here investigated was formed by coalescence of different scale melt channels and reaction zones with different sizes, confirming the published structural model.
Keywords: Oman Drilling Project; harzburgite; dunite channel; rock/melt reaction Oman Drilling Project; harzburgite; dunite channel; rock/melt reaction
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MDPI and ACS Style

Cocomazzi, G.; Grieco, G.; Tartarotti, P.; Bussolesi, M.; Zaccarini, F.; Crispini, L.; Science Team, O.D.P. The Formation of Dunite Channels within Harzburgite in the Wadi Tayin Massif, Oman Ophiolite: Insights from Compositional Variability of Cr-Spinel and Olivine in Holes BA1B and BA3A, Oman Drilling Project. Minerals 2020, 10, 167.

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