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 TiO (up to 1.25 ​wt.%), FeO (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.

Funding for this research was provided by the Fondo Europeo de Desarrollo Regional (FEDER) Funds, the Spanish Project CGL2015-65824 granted by the Spanish Ministerio de Economía y Competitividad (MINECO) to JAP and RTI2018-099157-A-I00 Ministerio de Ciencia, Innovación y Universidades (MICINN) to JMGJ. Additional funding was obtained from the Ramón y Cajal Fellowship RYC-2015-17596 to JMGJ (sponsored by MICINN), the Ph.D. grant BES-2016-076887 to JFdP (sponsored by MINECO), and the Mexican research programs Ciencia Básica (A1-S-14574) sponsored by the Consejo Nacional de Ciencia y Tecnología (CONACYT) from Mexico, and the Programa de Apoyo a Proyectos de Investigación e Innovación tecnológica (IA-101419) sponsored by the UNAM. Additional support was provided by the University of Barcelona and University of Granada, Spain. We also thank Dr. Carlos Ortega-Obregón (Laboratorio de Estudios Isotópicos of Centro de Geociencias, UNAM, Mexico) for the help with the Laser ICP-MS analyses on chromite.