Cold plumes trigger contamination of oceanic mantle wedges with continental crust-derived sediments: Evidence from chromitite zircon grains of eastern Cuban ophiolites

An Alternative Scenario on the Origin of Ultra-High Pressure (UHP) and Super-Reduced (SuR) Minerals in Ophiolitic Chromitites: A Case Study from the Mercedita Deposit (Eastern Cuba)

“…The Mercedita chromitite deposit is located in eastern Cuba (Figure 1a), part of the Mayarí-Baracoa ophiolitic belt. It is associated with Cretaceous HP serpentinite-matrix subduction mélanges (Sierra del Convento and La Corea), Early to Late Cretaceous volcanic arc sequences, and a Late Cretaceous metamorphic sole (the Güira de Jauco Amphibolite Complex) related to the onset of ophiolite obduction [16,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] (Figure 1a,b). The synorogenic La Picota and Mícara formations date oceanic arc-terrane collision and exhumation during latest Cretaceous to earliest Paleocene times, prior to the final northeasterly verging collision with the Bahamas platform and accretion of tectonic pile onto the North American plate (Figure 1b) [23,27,28,35,36].…”

“…In addition, it should be mentioned that euhedral grains of zircon have been identified [16] in heavy-mineral concentrates from the Mercedita chromitites.…”

“…Occurrence of UHP (Ultra-High Pressure), SuR (Super-Reduced) and Crustal-derived "exotic" mineral phases in worldwide ophiolites and chromitites. Luobusa (Tibet), Dingqing (Tibet) and Ray-Iz (Polar Urals) data is from [15,72] and references therein, Purang (Tibet) data from [73], Zedang (Tibet) data from [74], Semail (Oman) data from [4,62], Mirdita (Albania) data from [75], Ponzati-Karsanti (Turkey) data from [10], Orhaneli-Harmancik (Turkey) data from [11], Myitkyina (Myanmar) data from [76], Baja California (Mexico) data from [12] and Moa-Baracoa (Cuba) data from [16] and this study. ×: Indicates the presence of the mineral in the ophiolite (peridotites and/or chromitites).…”

“…Mineral concentrates from the Mercedita chromitite contain zircon, corundum, and quartz ( Table 2). According to [16], zircon yields an age between 289 ± 9 Ma (early Permian) and 310 ± 10 Ma (late Carboniferous), much older than the time of ophiolite formation (90-125 Ma); [23,25]. The zircon contains a suite of inclusions (monazite, K-feldspar, quartz, biotite, apatite and occasional ilmenite) typical of any zircon crystallized from a crustal magma.…”

“…Rapid exhumation of the deep-seated chromitites and host peridotites carrying SuR, UHP and continental-crust-derived minerals is related to the generation of low-viscosity upwelling channels created during the opening of marginal basins in island arcs or continental arcs as a result of retraction of subducting slabs during the rollback process [14,15]. In this model, crustal minerals are already present in the chromitite, which forms in a mantle wedge contaminated by subducted material with a crustal component after the ascent of cold plumes derived from the subducting slabs [12,16].…”