Zircon ages, mineralogy, and geochemistry of ophiolitic mafic and island-arc rocks from central Cuba: Implications for Cretaceous tectonics in the Caribbean region

Ophiolite-related rocks and volcanic-arc rocks are the main geological components in Cuba; deciphering their origin and evolution is fundamental in interpreting and reconstructing the tectonic processes for the Caribbean region. In this paper, we report new zircon UPb chronology, mineralogy, and geochemistry of ophiolitic metadiabase dikes and island-arc rocks in central Cuba, and discuss their origin and petrogenesis. The metadiabase dikes have a zircon UPb age of 135.0 ± 1.7 Ma; they are low-K tholeiites, and have geochemical characteristics intermediate between those of typical normal mid-ocean ridge basalt (N-MORB) and island-arc tholeiites (IAT), suggesting that they were formed in a back-arc basin. The investigated island-arc rocks, including amphibolite from the Mabujina amphibolite complex (MAC), plutonic diorite and their mafic enclaves, and volcanic dacite, have zircon UPb age of 93.53 Ma, 92.31 Ma, 94.35 Ma and 83.60 Ma, respectively, recording different phases of island-arc magmatism. The amphibolite samples have geochemical compositions suggesting that the protolith of the amphibolite was basaltic igneous rocks that originated from a depleted mantle source mildly modified by fluids from a subducting slab, and that the mantle source might be deep and garnet-bearing. Microstructures and elemental geochemical data reveal that the mafic enclaves and diorites represent distinct island-arc magma pulses that originated from partial melting of depleted mantle which had been previously modified by subduction-related mobile elements. The dacites are evolved island-arc volcanic rocks that formed through fractional crystallization of hydrous basaltic magmas that originated from a strongly depleted mantle source. Above data support such a tectonic model, that is, during the Early Cretaceous (from ∼135 Ma or even earlier), a typical trench–arc–basin system developed in the Caribbean region as a result of southwest-directed subduction of the Proto-Caribbean plate beneath the Caribbean plate; after that time, uninterrupted Proto-Caribbean plate subduction occurred, generating quasi-continuous arc magmatism from before ∼135 to 81 Ma, and gradually consuming the Proto-Caribbean Ocean. •A diabase dike in the ophiolite in central Cuba has a zircon UPb age of 135.0 ± 1.7 Ma.•A typical trench–arc–basin system developed in the Caribbean region during the Early Cretaceous.•The arc rocks have highly diverse major and trace elemental and isotopic compositions.