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

Panagiotis Pomonis,Andreas Magganas

doi:10.3390/geosciences7010010

Panagiotis Pomonis, Andreas Magganas

Open Access

https://doi.org/10.3390/geosciences7010010

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Journal: Geosciences	Publication Date: Mar 3, 2017
Citations: 7	License type: CC BY 4.0

Affiliation: National and Kapodistrian University of Athens

Abstract

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.

Highlights

Chromian spinel is a common mineral in peridotites of ophiolite complexes
Since the chemical composition of spinels depends on several petrogenetic factors and physical conditions of the host peridotites, e.g., [2,3,4], they can be correlated with different tectonic settings, e.g., [1,2,4,5,6,7,8,9,10,11]
We present for the first time petrographical and mineral chemical data of four dismembered ophiolite slices, Ypato, Alyki, Tragana and Megaplatanos, located in the Beotia and Lokris area of central Greece

Summary

Introduction

Chromian spinel is a common mineral in peridotites of ophiolite complexes. It has a wide range in composition and serves as an important petrogenetic indicator for ultramafic and related rocks [1].Since the chemical composition of spinels depends on several petrogenetic factors (e.g., crystallization from melt, residue after partial melting with variable degrees, crystallization via melt–peridotite interaction) and physical conditions (pressure, temperature, oxygen fugacity) of the host peridotites, e.g., [2,3,4], they can be correlated with different tectonic settings, e.g., [1,2,4,5,6,7,8,9,10,11]. Chromian spinel is a common mineral in peridotites of ophiolite complexes. It has a wide range in composition and serves as an important petrogenetic indicator for ultramafic and related rocks [1]. Since the chemical composition of spinels depends on several petrogenetic factors (e.g., crystallization from melt, residue after partial melting with variable degrees, crystallization via melt–peridotite interaction) and physical conditions (pressure, temperature, oxygen fugacity) of the host peridotites, e.g., [2,3,4], they can be correlated with different tectonic settings, e.g., [1,2,4,5,6,7,8,9,10,11]. The Cr# [= Cr/(Cr + Al) atomic ratio] of chromian spinel is an important geochemical parameter for the estimation of the degree of partial melting and provenance of peridotites [24]

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