Ophiolite hosted chromitite formed by supra-subduction zone peridotite –plume interaction |
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| Institution: | 1. Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain;2. Departamento de Mineraloga y Petrologa, Universidad de Granada, Facultad de Ciencias, Fuentenueva s/n, 18002, Granada, Spain;3. Department of Civil Engineering and Natural Resources, Luleå University of Technology, SE 97187, Luleå, Sweden;4. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, E-18100, Armilla, Granada, Spain;5. Instituto Geológico y Minero de España, C/ La Calera 1, Tres Cantos, 28760, Madrid, Spain;6. Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Ciudad de México, Mexico;7. Facultad de Ingeniería, Universidad Católica de Cibao, La Vega, Dominican Republic |
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| Abstract: | Chromitite bodies hosted in peridotites typical of suboceanic mantle (s.l. ophiolitic) are found in the northern and central part of the Loma Caribe peridotite, in the Cordillera Central of the Dominican Republic. These chromitites are massive pods of small size (less than a few meters across) and veins that intrude both dunite and harzburgite. Compositionally, they are high-Cr chromitites Cr# ?= ?Cr/(Cr ?+ ?Al) atomic ratio ?= ?0.71–0.83] singularly enriched in TiO2 (up to 1.25 ?wt.%), Fe2O3 (2.77–9.16 ?wt.%) as well as some trace elements (Ga, V, Co, Mn, and Zn) and PGE (up to 4548 ?ppb in whole-rock). This geochemical signature is unknown for chromitites hosted in oceanic upper mantle but akin to those chromites crystallized from mantle plume derived melts. Noteworthy, the melt estimated to be in equilibrium with such chromite from the Loma Caribe chromitites is similar to basalts derived from different source regions of a heterogeneous Caribbean mantle plume. This mantle plume is responsible for the formation of the Caribbean Large Igneous Province (CLIP). Dolerite dykes with back-arc basin basalt (BABB) and enriched mid-ocean ridge basalt (E-MORB) affinities commonly intrude the Loma Caribe peridotite, and are interpreted as evidence of the impact that the Caribbean plume had in the off-axis magmatism of the back-arc basin, developed after the Caribbean island-arc extension in the Late Cretaceous. We propose a model in which chromitites were formed in the shallow portion of the back-arc mantle as a result of the metasomatic reaction between the supra-subduction zone (SSZ) peridotites and upwelling plume-related melts. |
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| Keywords: | Chromitite Ophiolite Plume Mantle Back-arc basin Dominican Republic |
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