Metamorphic reprocessing of a serpentinized carbonate-bearing peridotite after detachment from the mantle wedge: A P-T path constrained from textures and phase diagrams in the system CaO-MgO-Al2O3-SiO2-CO2-H2O

Mposkos, E; Baziotis, I; Proyer, A

dc.contributor.author	Mposkos, E	en
dc.contributor.author	Baziotis, I	en
dc.contributor.author	Proyer, A	en
dc.date.accessioned	2014-03-01T01:33:43Z
dc.date.available	2014-03-01T01:33:43Z
dc.date.issued	2010	en
dc.identifier.issn	0024-4937	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20562
dc.subject	Carbonate-bearing metaperidotite	en
dc.subject	High-pressure metamorphism	en
dc.subject	Mantle wedge	en
dc.subject	Rhodope	en
dc.subject.classification	Geochemistry & Geophysics	en
dc.subject.classification	Mineralogy	en
dc.subject.other	carbonate	en
dc.subject.other	eclogite	en
dc.subject.other	geochemistry	en
dc.subject.other	isotopic composition	en
dc.subject.other	P-T conditions	en
dc.subject.other	P-T-t path	en
dc.subject.other	peridotite	en
dc.subject.other	phase transition	en
dc.subject.other	prograde metamorphism	en
dc.subject.other	rare earth element	en
dc.subject.other	serpentinization	en
dc.subject.other	tectonic evolution	en
dc.subject.other	tectonic setting	en
dc.subject.other	tectonic wedge	en
dc.subject.other	texture	en
dc.subject.other	ultrahigh pressure metamorphism	en
dc.subject.other	Eastern Macedonia and Thrace	en
dc.subject.other	Greece	en
dc.subject.other	Rhodope	en
dc.subject.other	Xanthi	en
dc.title	Metamorphic reprocessing of a serpentinized carbonate-bearing peridotite after detachment from the mantle wedge: A P-T path constrained from textures and phase diagrams in the system CaO-MgO-Al2O3-SiO2-CO2-H2O	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.lithos.2010.05.009	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.lithos.2010.05.009	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	In the central Rhodope mountains of Greece a carbonate-bearing metaperidotite lens similar to 200 x 500 m in size crops out as part of the high- to ultrahigh-pressure metamorphic Upper Sidironero Complex similar to 500 m SE of the Gorgona Village, north of Xanthi town. It is composed primarily of coarse grained (3-20 mm in size) olivine and orthopyroxene, medium grained clinohumite and medium to fine grained tremolite, chlorite, dolomite, magnesite, talc, antigorite and various spinel phases. Whole-rock chemistry, mineral textures and compositions, and phase diagram calculations show that the metaperidotite was subjected to a prograde HP metamorphism, isofacial with the surrounding migmatitic gneisses, metapelites and amphibolites. The prograde character of metamorphism is demonstrated by inclusions of talc, antigorite, chlorite, dolomite, magnesite and Ti-clinohumite in ferrit-chromite, olivine, and orthopyroxene, as well as of olivine in orthopyroxene, and by the typical change in composition of zoned spinel minerals from ferrit-chromite in the core to chromian spinel at the rim. The prograde path is characterized by successive growth of amphibole, Ti-clinohumite, olivine and orthopyroxene, followed by the breakdown of Ti-clinohumite to olivine + Mg-ilmenite and of chlorite to olivine + spinel, probably during exhumation. The construction of a partial petrogenetic P-T grid in the system CaO-MgO-Al2O3-SiO2-CO2-H2O (CMASCH) for Ca-poor ultramafic bulk compositions has proven highly useful for the reconstruction of the metamorphic evolution and a P-T path, indicating that the use of univariant reactions in mixed volatile systems is highly warranted. The P-T path is clearly constrained to pressures below 1.5-1.7 GPa by the absence of clinopyroxene. These pressures are slightly lower than those recorded in the closely associated Jurassic eclogites and much lower than those recorded in the diamond-bearing gneisses 5 km to the south in the same tectonic unit. The carbonate-bearing metaperidotite from Gorgona probably represents a fragment of the hydrated mantle wedge. This is indicated by the REE compositions which differ from those of ophiolitic peridotites and resemble those of spinal or garnet peridotites of sub-continental origin. The ultramafic slice was incorporated tectonically into the subduction channel, most likely by tectonic erosion in the Early Jurassic, but did not experience ultrahigh-pressure metamorphism like the nearby metapelites that exhumed along the same subduction channel. (C) 2010 Elsevier B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	Lithos	en
dc.identifier.doi	10.1016/j.lithos.2010.05.009	en
dc.identifier.isi	ISI:000280888200010	en
dc.identifier.volume	118	en
dc.identifier.issue	3-4	en
dc.identifier.spage	349	en
dc.identifier.epage	364	en