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Boletín de la Sociedad Geológica Mexicana Volumen 72, núm. 3, A110620, 2020 |
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Orthopyroxenite hosted chromitite veins anomalously enriched in platinum-group minerals from the Havana-Matanzas Ophiolite, Cuba
Vetas de cromitita en ortopiroxenita anómalamente enriquecidas en minerales del grupo del platino de la ofiolita Habana-Matanzas, Cuba
Júlia Farré-de-Pablo1,*, Núria Pujol-Solà1, Harlison Torres-Herrera2, Thomas Aiglsperger3, José María
González-Jiménez4, Angélica Isabel Llanes-Castro5, Antonio Garcia-Casco4,6, Joaquín A. Proenza1
1 Departament de Mineralogia, Petrologia i Geologia Aplicada. Facultat de Ciències de la Terra, Universitat de Barcelona. C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
2 Fundación Universitaria del Area Andina – Sede Valledupar. Transv 22 Bis 4-105, Valledupar, Colombia.
3 Department of Civil Engineering and Natural Resources, Luleå University of Technology. SE 97187, Luleå, Sweden.
4 Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada. Avda. Fuentenueva, s/n, 18002, Granada, Spain.
5 Departamento de Petrología y Mineralogía, Instituto de Geología y Paleontología. Vía Blanca 1002, San Miguel del Padrón, Cuba.
6 Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR). Avda. de las Palmeras 4, E-18100 Armilla, Granada, Spain.
* Corresponding author: (J. Farré de Pablo) This email address is being protected from spambots. You need JavaScript enabled to view it.
How to cite this article:
Farré-de-Pablo, J., Pujol-Solà, N., Torres-Herrera, H., Aiglsperger, T., González-Jiménez, J. M., Llanes-Castro, A. I., Garcia-Casco, A., Proenza, J. A., 2020, Orthopyroxenite hosted chromitite veins anomalously enriched in platinum-group minerals from the Havana-Matanza Ophiolite, Cuba: Boletín de la Sociedad Geológica Mexicana, 72 (3), A110620. http://dx.doi.org/10.18268/BSGM2020v72n3a110620
Abstract
The Havana–Matanzas Ophiolite contains one of the few examples of ophiolitic platinum group minerals (PGM)-rich chromitites associated with orthopyroxenites in the mantle section of ophiolitic complexes. The chromitites occur as veins hosted by orthopyroxenite bands within mantle peridotites. The peridotites are mostly harzburgites and their accessory chromite shows high-Al compositions (Cr# [Cr/(Cr+Al), atomic ratio] = 0.39–0.50), which are typical of spinels in abyssal peridotites. Conversely, chromite from the chromitite veins and their host orthopyroxenite are high-Cr (Cr# = 0.72–0.73 and 0.62–0.69, respectively), with lower Mg# [Mg/(Mg+Fe2+), atomic ratio]. This suggests that both the chromitite and the orthopyroxenite formed from melts with boninitic affinity. The abundant PGM inclusions found in the chromitites are mainly Os-rich laurite grains, which is also characteristic of chromitites formed from magmas with boninitic affinity. Therefore, we propose that the chromitite veins and the orthopyroxenite bands probably formed contemporaneously in the fore-arc setting of an intra-oceanic arc during subduction. The chromitite-orthopyroxenite pair of the Havana-Matanzas Ophiolite could form after the reaction of a Si-rich melt with boninitic affinity and mantle harzburgite, with the orthopyroxenite bands preserving fingerprints of the infiltration of boninitic-affinity melts within the mantle. The small volume of forming chromitite could maximize the efficiency for the mechanical collection of the PGM forming in the parental melt of these rocks, resulting in the anomalous enrichment of primary PGM in the chromitites.
Keywords: chromitite, Cuba, ophiolite, orthopyroxenite, PGM.
