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A new jadeitite jade locality (Sierra del Convento, Cuba): first report and some petrological and archeological implications |
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| Authors: | Antonio García-Casco A Rodríguez Vega J Cárdenas Párraga M A Iturralde-Vinent C Lázaro I Blanco Quintero Y Rojas Agramonte A Kröner K Núñez Cambra G Millán R L Torres-Roldán S Carrasquilla |
| Institution: | 1. Departamento de Mineralogía y Petrología, Universidad de Granada, and Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Avda Fuentenueva sn, 18002, Granada, Spain 2. Departamento de Geología, Instituto Superior Minero-Metalúrgico, Las Coloradas s/n., Moa, 83329, Holguín, Cuba 3. Departamento de Mineralogía y Petrología, Universidad de Granada, Avda Fuentenueva sn, 18002, Granada, Spain 4. Museo Nacional de Historia Natural, Obispo no. 61, Plaza de Armas, 10100, La Habana, Cuba 5. Institut für Geowissenschaften, Universit?t Mainz, 55099, Mainz, Germany 6. Instituto de Geología y Paleontología, Via Blanca y Carretera Central, San Miguel del Padrón, 11000, Ciudad Habana, Cuba |
| Abstract: | A new jadeitite jade locality has been discovered in the serpentinite-matrix subduction mélange of the Sierra del Convento (eastern Cuba) in a context associated with tectonic blocks of garnet-epidote amphibolite, tonalitic–trondhjemitic epidote gneiss, and blueschist. The mineral assemblages of jadeitite jade and jadeite rocks are varied and include combinations of jadeite, omphacite, albite, paragonite, analcime, clinozoisite-epidote, apatite, phlogopite, phengite, chlorite, glaucophane, titanite, rutile, zircon, and quartz formed during various stages in their P–T evolution. Field relationships are obscure, but some samples made almost exclusively of jadeite show evidence of crystallization from fluid in veins. In one of these samples studied in detail jadeite shows complex textural and chemical characteristics (including oscillatory zoning) that denote growth in a changing chemical medium. It is proposed that interaction of an Al–Na rich fluid with ultramafic rocks produced Al–Na–Mg–Ca fluids of varying composition. Episodic infiltration of these fluids, as a result of episodic opening of the veins, developed oscillatory zoning by direct precipitation from fluid and after reaction of fluid with pre-existing jadeite. The latest infiltrating fluids were richer in Mg–Ca, favouring the formation of omphacite and Mg–Ca rich jadeite in open voids and the replacement of earlier jadeite by fine-grained omphacite + jadeite at 550–560°C. This new occurrence of jadeite in Cuba opens important perspectives for archeological studies of pre-Columbian jade artifacts in the Caribbean region. |
| Keywords: | Jadeitite jade High pressure Fluids Subduction Caribbean Eastern Cuba |
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