Composition, melting and evolution of the upper mantle beneath the Jurassic Pindos ocean inferred by ophiolitic ultramafic rocks in East Othris, Greece

Magganas, Andreas; Koutsovitis, Petros

doi:10.1007/s00531-014-1137-z

Cited by 26 publications

(32 citation statements)

References 116 publications

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“…However, the current observed differences can be attributed to different degrees of partial melting and melt impregnation of the mantle in the two areas, suggesting the occurrence of a large mantle inhomogeneity. This interpretation is consistent with previous works, which have shown that the west Othrys ophiolite is related with an extension regime (back-arc basin or MORB; [23,24,30]), while the east Othrys ophiolite is strongly associated with a supra-subduction zone setting (SSZ; [24,31]). …”

Section: Petrogenetic Implicationssupporting

confidence: 93%

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

et al. 2016

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Platinum-group minerals were concentrated using superpanning from two composite chromitite samples, which were collected from two old mines within the Othrys ophiolite. This method allows for the recovery of a broad spectrum of these rare and fine-grained minerals, and helps to better identify them and interpret their origin. Major differences between the east and west Othrys ophiolites were determined, probably as a result of their different origin and evolution. Primary Os-, Ir-, and Ru-bearing platinum-group minerals (IPGM)-alloys and the Rh-, Pt-and Pd-bearing platinum-group minerals (PPGM) occur only in the east Othrys chromitite, indicating an evolution from initially low f S2 conditions at shallower mantle levels with the subsequent implication of a S-saturated ascending fluid. In contrast, the absence of primary IPGM-alloys in west Othrys chromitite indicates that S saturation had been attained. The presence of erlichmanite suggests that sulphur fugacity eventually increased significantly in both suites. Substantial fluctuations of a fluid phase, likely related to serpentinising fluids, modified the platinum-group minerals (PGM) assemblage of west Othrys, and resulted in a large diversity of secondary PGM minerals. The limited number of secondary species developed in the east Othrys indicate that secondary processes were also different in the two suites.

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Section: Petrogenetic Implicationssupporting

confidence: 93%

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

et al. 2016

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“…The mantle section of many ophiolites contains clearly compositionally heterogeneous peridotites, e.g., [60][61][62], which display mineralogical, textural and compositional evidence for complex, multi-phase melting, depletion and enrichment processes in their petrogenetic history [63,64]. Moreover, the studied Cr-spinels hosted in the harzburgite and dunite resemble those occurring in ultramafic rocks from Pindos and Othris ophiolites, while the Cr-spinels from Alyki resemble those occurring in lherzolites from Iti, Kallidromon, Othris and Koziakas ophiolites that have been interpreted as being formed (entirely or partially) in SSZ settings [32][33][34][35][36][37][38][39]44,65], thus pointing to a similar origin. [2]; (b) Binary diagram of TiO2 (wt.…”

Section: Partial Melting and Geotectonic Settingmentioning

confidence: 99%

“…Fields for mid-ocean ridge basalts (MORB) and island arc volcanics (IAV), as well as MOR and supra-subduction zone (SSZ) peridotites according to [7]. Field for spinels from Iti, Othris and Koziakas peridotites are according to [35][36][37][38][39]. Legend as in Figure 5a.…”

Section: Partial Melting and Geotectonic Settingmentioning

confidence: 99%

Petrogenetic Implications for Ophiolite Ultramafic Bodies from Lokris and Beotia (Central Greece) Based on Chemistry of Their Cr-spinels

Pomonis

Magganas

2017

Geosciences

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Cr-spinels from ultramafic rocks from Lokris (Megaplatanos and Tragana), and Beotia (Ypato and Alyki) ophiolitic occurrences were studied. These rocks comprise principally harzburgite with minor dunite. Small amounts of clinopyroxene-rich harzburgite and lherzolite have been observed along with the harzburgite in Alyki. The Cr# in the studied spinels displays a wide variability. The spinels hosted in harzburgite and cpx-rich harzburgite display low Cr# (<0.6), typical for oceanic (including back-arc basins) ophiolites, whereas the spinels hosted in dunite with Cr# (>0.6) characterize arc-related ophiolitic sequences. Cr-spinels from Alyki indicate a moderate fertile character and are analogous to those from abyssal peridotites. The dunitic and harzburgitic spinel-olivine pairs are consistent with a Supra-Subduction Zone origin. The relatively large range in spinel Cr# and Mg# may have been resulted from a wide range of degrees of mantle melting during the evolution of the host peridotites.

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“…Subduction-related and subduction-unrelated ophiolites [1] form in a variety of tectonic settings including oceanic spreading centres, backarc and forearc basins, arcs and other extensional magmatic settings including those in association with plumes [2][3][4][5][6]. The chemical composition of ophiolitic rocks is commonly used for recognising a variety of different tectonic settings, as well as the nature of mantle sources.…”

Section: Introductionmentioning

confidence: 99%

New Occurrence of Pyroxenites in the Veria-Naousa Ophiolite (North Greece): Implications on Their Origin and Petrogenetic Evolution

et al. 2017

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Abstract:The Veria-Naousa ophiolite represents a dismembered unit in north Greece, which includes variably serpentinised lherzolite and harzburgite, locally intruded by a sparse network of dykes or thin layers of websterite and olivine-orthopyroxenite composition. The websterite and the olivine-orthopyroxenite show abundant petrographic and geochemical evidence (relic olivines with mantle affinities, Cr-rich spinels, low Al 2 O 3 , depletions in incompatible elements, and concave upwards rare earth element patterns) that they comprise replacive bodies from refractory subarc mantle precursors. The occurrence of these pyroxenites in dykes implies that channelled percolation of melts account for their replacive character. High CaO/Al 2 O 3 , low Zr and crystallisation of diopside suggest that a melt of ankaramitic/carbonatitic composition percolated in lherzolite replacing porphyroclastic olivine and forming the pyroxenes in the websterite. At a shallower level, harburgites were impregnated by boninitic melts (inferred by U-shape rare earth element patterns and very rich in Cr spinels) triggering the replacement of porphyroclastic olivine by orthopyroxene for the formation of olivine-orthopyroxenite. These peritectic replacements of olivine commonly occur in a mantle wedge regime. The peculiar characteristics of the Veria-Naousa pyroxenites with LREE and compatible elements enrichments resemble the subarc pyroxenites of Cabo Ortegal implying a similar environment of formation. Whole-rock and mineralogical (spinel and clinopyroxene) compositions are also in favour of a backarc to arc environment. It is recommended that the evolution of the Veria-Naousa pyroxenites record the evolution of the subarc region and the opening of a backarc basin in a broad SSZ setting in the Axios Zone of eastern Greece.

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Composition, melting and evolution of the upper mantle beneath the Jurassic Pindos ocean inferred by ophiolitic ultramafic rocks in East Othris, Greece

Cited by 26 publications

References 116 publications

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

Petrogenetic Implications for Ophiolite Ultramafic Bodies from Lokris and Beotia (Central Greece) Based on Chemistry of Their Cr-spinels

New Occurrence of Pyroxenites in the Veria-Naousa Ophiolite (North Greece): Implications on Their Origin and Petrogenetic Evolution

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