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The Othris Ophiolite, Greece: A snapshot of subduction initiation at a mid-ocean ridge |
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| Authors: | Matthias G Barth Paul RD Mason Gareth R Davies Martyn R Drury |
| Institution: | aInstitut für Geowissenschaften, Universität Mainz, Becherweg 21, 55099 Mainz, Germany;bVening Meinesz Research School of Geodynamics, Departement Aardwetenschappen, Universiteit Utrecht, Budapestlaan 4, 3584 CD Utrecht, The Netherlands;cFaculteit der Aard-en Levenswetenschappen, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands |
| Abstract: | The mantle section of the Tethyan-type Othris Ophiolite, Greece, records tectono-magmatic processes characteristic of both mid-ocean ridges and supra-subduction zones. The Othris Ophiolite is a remnant of the Jurassic Neotethys Ocean, which existed between Eurasia and Gondwanaland. Othris peridotites range from fertile plagioclase lherzolites to depleted harzburgites. Abundances of Al2O3 and CaO show well-defined inverse linear correlations with MgO, suggesting that the Othris peridotites formed as residua from variable degrees of partial melting. Peridotites from the Fournos Kaïtsa and western Katáchloron sub-massifs are similar to abyssal peridotites and can be explained by a multistage model with some melting in the garnet stability field followed by moderate degrees of anhydrous near-fractional melting in the spinel stability field. In contrast, the peridotites from the Metalleio, Eretria, and eastern Katáchloron sub-massifs, and the Vourinos ophiolite are highly depleted and have extremely low concentrations of Al2O3 and heavy rare earth elements. These peridotites have enriched light REE contents compared to the middle REE. These residua are best modelled by hydrous melting due to a flux of slab-derived fluid to the mantle wedge during melting. The occurrence of both styles of melting regimes within close spatial and temporal association in the same ophiolite is explained by intra-oceanic thrusting and forced subduction initiation at (or near) a mid-ocean ridge. Thus, the Othris Ophiolite, and probably Tethyan-type ophiolites in general, represent a transient phase of plate tectonic reorganisation rather than quasi-steady state plate tectonics. |
| Keywords: | Ophiolite Peridotites Subduction initiation Partial melting |
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