Dolomitic marbles from the ultrahigh-pressure metamorphic Kimi complex in Rhodope, N.E. Greece

Mposkos, E; Baziotis, I; Proyer, A; Hoinkes, G

dc.contributor.author	Mposkos, E	en
dc.contributor.author	Baziotis, I	en
dc.contributor.author	Proyer, A	en
dc.contributor.author	Hoinkes, G	en
dc.date.accessioned	2014-03-01T02:44:01Z
dc.date.available	2014-03-01T02:44:01Z
dc.date.issued	2006	en
dc.identifier.issn	0930-0708	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/31618
dc.subject.classification	Geochemistry & Geophysics	en
dc.subject.classification	Mineralogy	en
dc.subject.other	ARAGONITE PLUS MAGNESITE	en
dc.subject.other	SYSTEM CACO3-MGCO3	en
dc.subject.other	JOIN CACO3-MGCO3	en
dc.subject.other	DIAMOND	en
dc.subject.other	ROCKS	en
dc.subject.other	COESITE	en
dc.subject.other	SUBSOLIDUS	en
dc.subject.other	CHINA	en
dc.subject.other	EXHUMATION	en
dc.subject.other	INCLUSIONS	en
dc.title	Dolomitic marbles from the ultrahigh-pressure metamorphic Kimi complex in Rhodope, N.E. Greece	en
heal.type	conferenceItem	en
heal.identifier.primary	10.1007/s00710-006-0159-z	en
heal.identifier.secondary	http://dx.doi.org/10.1007/s00710-006-0159-z	en
heal.language	English	en
heal.publicationDate	2006	en
heal.abstract	Dolomitic marbles from the Organi and Pandrosos areas of the ultrahigh-pressure (UHP) metamorphic Kimi complex in East Rhodope, N.E. Greece have the mineral assemblage: Ca1 + Do1 + O1 + Ph1 +/- Di +/- Hb1 +/- Sp1 +/- Ti-Chu + retrograde Srp and Ch1. Several generations of calcite and dolomite with variable composition and texture represent different stages of the P-T evolution: The first stage is represented by matrix dolomite (X-MgCO3 = 0.48) and relic domains of homogenous composition in matrix calcite (X-MgCO3 = 0.11-0. 13); the second stage is evident from precipitation of lath-shaped and vermicular dolomite in matrix calcite. The third stage is represented by veinlets of almost pure CaCO3 and domainal replacement of prior calcite by nearly pure CaCO3 + Ca-rich dolomite (X-MgCO3 = 0.34-0.43). Matrix dolomite adjacent to CaCO3 veinlets also becomes Ca-rich (X-MgCO3 = 0.42). In fact, Ca-rich dolomites with X-MgCO3 in the range of 0.40-0.34 are reported for the first time from metamorphic marbles. Coexisting Ca-rich dolomite and Mg-poor calcite cannot be explained by the calcite-dolomite miscibility gap. This assemblage rather suggests that Mg-poor calcite was aragonite originally, which formed together with Ca-rich dolomite according to the reaction Mg-Cal -> Arg -> Dol (1) at ultrahigh pressures and temperatures above at least 850 degrees C, when dolomite becomes disordered and incorporates more Ca than coexisting aragonite does in terms of Mg. The simplest explanation of these observations probably is to suggest two metamorphic events: The first one represented by relic matrix carbonates at relatively low to moderate pressures and temperatures of ca. 750 degrees C, and the second one limited by the minimum temperatures for dolomite disorder (ca. 850 degrees C) and in the aragonite+ dolomite stability field, i.e. at a minimum pressure of 3 GPa and, if the presence of diamond-bearing metapelites nearby is considered, at conditions of at least 850 degrees C and 4.3 GPa in the diamond stability field. As there is hardly any back-reaction of Ca-rich dolomite + Mg-poor calcite to Mg-rich calcite, peak temperatures remained below the reaction (1) and the exhumation path probably crossed the aragonite-calcite transition at much lower than peak temperature. Cooling and decompression must have both occurred extremely fast in order for the mu m-sized Ca-rich dolomite textures to be preserved. An alternative explanation of the formation of "UHP" -textures and compositions is by a fluid influx that not only caused serpentinisation and chloritisation of silicates but also Mg-leaching from carbonates, particularly from Mg-rich calcite and its fine grained dolomite-precipitates, thus transforming them into Mg-poor calcite + Ca-rich dolomite.	en
heal.publisher	SPRINGER WIEN	en
heal.journalName	Mineralogy and Petrology	en
dc.identifier.doi	10.1007/s00710-006-0159-z	en
dc.identifier.isi	ISI:000241174000017	en
dc.identifier.volume	88	en
dc.identifier.issue	1-2	en
dc.identifier.spage	341	en
dc.identifier.epage	362	en