Mineralogy, geochemistry and geotectonic significance of harzburgites from the southern Dramala upper mantle suite, Pindos ophiolite complex, NW Greece

Abstract

The Dramala massif, located in the Dinarides–Hellenides orogenic belt, forms the mantle section of the Neotethyan Pindos ophiolite complex in NW continental Greece. Its southern domain is comprised mainly of voluminous harzburgite masses with variable clinopyroxene and olivine modal abundances, ranging from clinopyroxene‐bearing to typical and olivine‐rich harzburgites. The harzburgite varieties are characterized by elevated Cr# [Cr/(Cr + Al)] in Cr‐spinel (0.43–0.79), high forsterite (Fo) content in olivine (0.90–0.93), low Al2O3 content in clinopyroxene (≤1.77 wt.%) and poor whole‐rock abundances of Al2O3 (≤0.68 wt.%), CaO (≤0.68 wt.%), Sc (≤11 ppm) and REE, which are indicative of their refractory nature. In terms of fO2 values, the southern Pindos harzburgites plot between the FMQ‐2 (Fayalite–Magnetite–Quartz) and FMQ + 2 buffers. Simple batch and fractional melting models are not sufficient to explain their depleted composition. Their Ni/Yb ratios vs. Yb bulk‐rock abundances can be reproduced by up to 22–31% closed‐system non‐modal dynamic melting of an assumed spinel‐bearing lherzolite source. Cr‐spinel chemistry data suggest that the southern Dramala harzburgites were formed in an oceanic centre and then were reworked in the mantle wedge above a subducted slab. Combined petrographic and compositional data indicate that the studied harzburgites interacted with arc‐derived tholeiitic melts. This interaction resulted in substantial olivine and minor Cr‐spinel addition to the studied harzburgites, thus enhancing their refractoriness. Cryptic metasomatism was plausibly responsible for the demolition of any strong geochemical signatures suggestive of a previous melting event in a spreading centre. Comparable observations from the neighbouring Vourinos suite imply that the southern Dramala harzburgites probably represent an arc/fore‐arc mantle region within the mutual Pindos–Vourinos, Mesohellenic lithospheric mantle. Copyright © 2014 John Wiley & Sons, Ltd.

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

“…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.…”

“…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.…”

Genesis and Geodynamic Significance of Chromitites from the Fuchuan Ophiolite, Southern China, as Evidenced by Trace Element Fingerprints of Chromite, Olivine and Pyroxene

“…Mantle peridotites and chromitites in ophiolites from different tectonic settings can be used as natural laboratories to help us understand the processes that essentially take place within the upper mantle (Zhou et al, 2005;Kapsiotis, 2016). The Fuchuan ophiolite (FO), one of the oldest in the South China block, is located at Shexian, Anhui Province in the northeasternmost segment of the Jiangnan orogen (Zhou et al, 1989;Wang X L et al, 2017), and it hosts a small high-Al podiform chromitite deposit.…”

Υπολείμματα Ανώτερου Μανδύα Και Ωκεάνιου Φλοιού Από Περιοχές Της Κεντρικής Μακεδονίας

“…Οι σημαντικότερες οφιολιθικές εμφανίσεις που απαρτίζουν τη δυτική ζώνη είναι της Πίνδου (π.χ. Capedri et al 1981, Kostopoulos 1988, Rassios 1991, Jones & Robertson 1991, Saccani & Photiades 2004, Kapsiotis 2013b, 2014, 2016, του Βούρινου (Savvidis & Hovorka 1997, Rassios & Smith 2000, Καψιώτης 2009, Kapsiotis 2013b, Tzamos 2017, της Όθρυος (Μιγγίρος 1990, Rassios 1990, Rassios & Konstantopoulou 1993, Dijkstra 2001, Barth et al 2008, Barth & Gluhak 2009, Koutsovitis 2012, Magganas & Koutsovitis 2015, της Εύβοιας (Gartzos et al 1990, Danelian & Robertson 2001, Gartzos 2009, καθώς και μικρότερες οφιολιθικές εμφανίσεις όπως της Καστοριάς (Mountrakis 1986), του Κόζιακα (Pomonis et al 2002, Πομώνης 2003, Pomonis et al 2005, 2007b, Chiari et al 2012, του Βερμίου (Economou 1983), της Ανατολικής Θεσσαλίας (Migiros & Economou 1988), της Οίτης (Καρίπη 2004(Καρίπη , Karipi et al 2008) και της Αργολίδας (Hatzipanagiotou 1990, Bortolotti et al 2002. Στην ανατολική ζώνη, οι κυριότερες οφιολιθικές εμφανίσεις είναι της Γευγελής (Ivanov 1987), της Κεντρικής Χαλκιδικής…”