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Please use this identifier to cite or link to this item: http://hdl.handle.net/10481/32078

Title: Metamorphism on Chromite Ores from the Dobromirtsi Ultramafic Massif, Rhodope Mountains (SE Bulgaria)
Authors: González-Jiménez, José María
Kerestedjian, Thomas
Proenza Fernández, Joaquín Antonio
Gervilla Linares, Fernando
Issue Date: 2009
Abstract: Podiform chromitite bodies occur in highly serpentinized peridotites at Dobromirtsi Ultramafic Massif (Rhodope Mountains, southeastern Bulgaria). The ultramafic body is believed to represent a fragment of Palaeozoic ophiolite mantle. The ophiolite sequence is associated with greenschist - lower-temperature amphibolite facies metamorphosed rocks (biotitic gneisses hosting amphibolite). This association suggests that peridotites, chromitites and metamorphic rocks underwent a common metamorphic evolution. Chromitites at Dobromirtsi have been strongly altered. Their degree of alteration depends on the chromite/silicate ratio and to a lesser extent, on the size of chromitite bodies. Alteration is recorded in individual chromite grains in the form of optical and chemical zoning. Core to rim chemical trends are expressed by MgO- and Al2O3- impoverishment, mainly compensated by FeO and/or Fe2O3 increases. Such chemical variations correspond with three main alteration events. The first one was associated with ocean-floor metamorphism and was characterized by a lizardite replacement of olivine and the absence of chromite alteration. The second event took place during greenchist facies metamorphism. During this event, MgO- and SiO2-rich fluids (derived from low temperatura serpentinization of olivine and pyroxenes) reacted with chromite to form chlorite; as a consequence, chromite became altered to a FeO- and Cr2O3-rich, Al2O3-poor chromite. The third event, mainly developed during lower temperature amphibolite facies metamorphism, caused the replacement of the primary and previously altered chromite by Fe2O3-rich chromite (ferritchromite).
Sponsorship: This research was financially supported by the Spanish project CGL2007-61205 of the MEC, the CSICBAS collaborative project 2007BG0006, the research group (RNM 131) of the Junta de Andalucía, and an F.P.I grant BES-2005-8328 of the Spanish Ministry of Education and Sciences.
Publisher: Universidad de Barcelona; Instituto de Ciencias de la Tierra Jaume Almera
Keywords: Ophiolite
Chromite
Metamorphism
Dobromirtsi Ultramafic Massif
Bulgaria
URI: http://hdl.handle.net/10481/32078
ISSN: 1695-6133
1696-5728
Rights : Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License
Citation: González-Jiménez, J.M.; et al. Metamorphism on Chromite Ores from the Dobromirtsi Ultramafic Massif, Rhodope Mountains (SE Bulgaria). Geologica Acta, 7(4): 413-429 (2009). [http://hdl.handle.net/10481/32078]
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