Mineralogy and partial melt textures within an ultramafic-mafic body,Greece |
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Authors: | Martin Menzies |
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Institution: | (1) Department of Mineralogy and Petrology, Downing Place, Cambridge |
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Abstract: | Ultramafic-mafic rocks from Makrirrakhi, Central Greece exhibit features of an original ophiolite sequence which contains depleted mantle material, ultramafic containing partial melt textures and possibly the mafic pluton which resulted from the coalescing of these partial melt segregations. Considerable mineralogical variation exists: unzoned olivine crystals range in composition from Fo78–84 (mafics) to Fo88–92 (ultramafics), plagioclases An64–79 (mafics) to An80–90 (ultramafics) and spinel varies from a chromian spinel (ultramafics) to a more aluminous-titaniferous spinel (mafics). Pyroxenes from the ultramafics display a limited range: En89–92 Fs9–8 Wo0–2 (orthopyroxene) and En48–54 Fs1–10 Wo38–50 (clinopyroxene). Mafic rocks display a greater range being richer in ferrosilite En36–65 Fs3–20 Wo33–51. Pyroxenes from within the partial melt segregations have chemical affinities with those from the gabbrotroctolite series. A model of partial melt within the upper mantle, and, a set of criteria to distinguish partial melt textures from cumulate textures, are developed from analytical data and textural evidence. |
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