PETROLOGY, GEOCHEMISTRY AND TECTONIC SETTING OF OPHIOLITES IN CUBA

The Mesozoic ophiolites of Cuba (the so-called Northern Cuban Ophiolite Belt, NCOB, and the Eastern Cuban Ophiolites, ECO) constitutes the most extensive surface exposure of oceanic lithosphere in the Circum-Caribbean region. The ophiolitic units represent pieces of oceanic lithosphere obducted onto the passive North American continental paleo-margin in Late Cretaceous to Late Eocene time during collision between the Caribbean arc with Jurassic-Cretaceous passive margins of the continental Maya block and the Bahamas platform.

The NCOB comprises five variously sized individual thrust-bounded blocks, separated by major fault zones, from west to east: Cajálbana, Habana-Matanza, Villa Clara, Camagüey and Holguín, while the ECO includes the Mayarí-Cristal and Moa-Baracoa units. The ophiolite assemblages of all blocks are highly dismembered and complete sequences of a classic ophiolite suite are not present. However, sections of mantle tectonite harzburgite and a Moho transition zone overlain by layered gabbros and mafic volcanic rocks and sediments occur, whereas sheeted dikes and isotropic gabbro are rarely found.

The ophiolites of Cuba contain remnants of ancient oceanic crust and upper mantle of different origins and formed in a variety of tectonic settings, including both MOR and SSZ. The MOR-type ophiolites represent remnants of the proto-Caribbean oceanic crust formed during Upper-Jurassic-Cretaceous at an oceanic spreading center that separated the North and South American plates after Pangea’s break-up. MOR-type ophiolites are only locally preserved in central Cuba as dismembered tectonic slices, commonly associated with serpentinite matrix mélanges bearing high-pressure metamorphic blocks. However, the widespread occurrence of refractory mantle peridotites, Al- and Cr-rich chromitite bodies, as well as extrusive rocks with FAB, boninites, low-Ti IAT, IAT, and BABB affinities indicate formation/modification of oceanic lithosphere above a subduction zone (SSZ-type ophiolites) both in NCOB and ECO. SSZ ophiolites formed by sea-floor spreading in the oceanic Caribbean plate during subduction of the proto-Caribbean and formation of the associated Caribbean volcanic arc (~135-70 Ma). Our results indicate that NCOB cannot be classified as “plume type” as was suggested by some authors.