Image source: Iturralde-Vinent, M.A. 1998. Sinopsis de la constitución geológica de Cuba. Acta Geológica Hispánica 33, 9-56.

Image source: Modified after Iturralde-Vinent, M.A. 1998. Sinopsis de la constitución geológica de Cuba. Acta Geológica Hispánica 33, 9-56.
 
Image source: García-Casco et al., 2006, High pressure metamorphism of ophiolites in Cuba. Geologica Acta 4, 63-88. The serpentinite bodies within the Sierra del Rosario belt are considered olistostromes or olistoplates deposited in the syntectonic Eocene Manacas formation. The Vieja unit containing exotic blocks is part of this Manacas formation.

Western Cuba is here used informally to represent the geological units which crop out mostly in the Pinar del Río province. The Geology of this region diverges from that of central Cuba in that the continental Guaniguanico terrane represents the Mesozoic margin of the Maya block (Iturralde-Vinent, 1994; Pszczólkowski, 1999), though the oceanic terranes correlate with central Cuba. The Cajálbana ophiolite body is the western counterpart of the northern ophiolite belt. The body is noticeably elongated and tectonically sandwiched in between tectonic slices of two Cretaceous arc sequences: the Albian-Campanian volcanic-sedimentary sequences of the Bahía Honda belt to the north and the
Albian-Cenomanian Felicidades belt to the south (Fig. 4). The Bahía Honda belt constitutes the western equivalent of the calc-alkaline Albian-Campanian volcanic arc belt while the Felicidades belt is interpreted as an adjacent marginal-sea basin of nearly the same age (Iturralde-Vinent, 1996a, b; Kerr et al., 1999). The Cajálbana ophiolite and the Bahía Honda and Felicidades belts are grouped within the oceanic Bahía Honda allochthonous terrane, which overrides the Guaniguanico terrane along NW-directed thrusts (Iturralde-Vinent, 1994; 1996a). The
Guaniguanico terrane is formed by north verging thrust belts, namely the Quiñones, Sierra del Rosario, Sierra de los Órganos and Cangre belts (Fig. 4A), composed of Jurassic and Cretaceous sedimentary sequences related to the eastern margin of the Maya block (North American Plate) and syntectonic Paleocene to Middle Eocene foreland sediments (Iturralde-Vinent, 1994, 1996a; Rosencrantz, 1990, 1996; Bralower and Iturralde-Vinent, 1997; Pszczólkowski, 1999). Iturralde-Vinent (1994, 1996a) and Pszczólkowski (1999) considered that thrusting and gravitational sliding during the Paleogene completely reversed the original relative paleogeographic positions of the Guaniguanico thrust units. Gordon et al. (1997) identified a complex Paleogene tectonic history with at least five phases of deformation. The terrane is non-metamorphic, except the Cangre belt, metamorphosed to high pressure low temperature conditions (Somin and Millán, 1981; Pszczólkowski and Albear, 1985; Millán, 1988, 1997a). The age of metamorphism has not been precisely determined. Somin et al. (1992, sample M-3) reported a K-Ar whole-rock data of 113 ± 5 Ma in a sample of micaquartz schist that probably represents a mixture of detritic and metamorphic ages (Hutson et al., 1998).

Mostly in the Sierra del Rosario belt, metamorphosed and non-metamorphosed ophiolitic material appears as medium-to large-sized exotic blocks and olistoplates incorporated into syn-tectonic olistostromic formations having a Lower Eocene sedimentary matrix (Pszczólkowski, 1978; Somin and Millán, 1981; Somin et al., 1992; Millán, 1996a, 1997a; Bralower and Iturralde-Vinent, 1997). The metamorphosed blocks consist of serpentinite-matrix mélanges containing HP exotic blocks. Available age data from the HP metamorphic blocks range form 128 to 58 Ma, with recurrence of 110±10 Ma ages (Somin and Millán, 1981; Somin et al., 1992; Iturralde-Vinent et al., 1996). The coincidence of age data of HP blocks from western and central Cuba suggests that the occurrence of HP ophiolitic rocks within Lower Eocene sedimentary matrix in western Cuba is a peculiarity of this region related to the late stages of Tertiary orogenic evolution and not to the primary evolution of the subduction system where the HP blocks originated. Additionally, the Early Cretaceous radiometric ages in western and central Cuba mélanges suggest that HP metamorphism developed in the same subduction system.

Image source: García-Casco et al., 2006, High pressure metamorphism of ophiolites in Cuba. Geologica Acta 4, 63-88.

Although sample SRO1A formed at a distinct shallower level in the subduction system compared with the eclogites from central Cuba, their metamorphic evolutions prove to be similar. This interpretation is confirmed by prograde growth zoning of garnet from this W-Cuba sample, which is disturbed by several euhedral concentric oscillations in Mn, Mg, Ca and Fe. These oscillations developed in the course of prograde metamorphism towards peak albite-epidote amphibolite facies conditions. As in the eclogites of central Cuba, the increase in Mn and decrease in Mg# at the reversed layers indicate formation upon recurrent prograde-retrograde episodes taking place in the course of subduction. Matrix amphibole shows a distinctively irregular patchy zoning in many grains. When concentric zoning is developed the cores are actinolitic and the overgrowths are magnesiohornblende to barroisite-magnesiokatophorite, indicating prograde growth. The outermost rims are retrograde as they trend backwards to magnesiohornblende and actinolite with increasing Mg# relative to peak sodic-calcic amphibole. The inclusions of amphibole within garnet cores are similar to the actinolitic cores of matrix amphibole. Consequently, the prograde zoning of matrix amphibole correlates, at least in part, with the oscillatory zoning of garnet. Indeed, the preservation of prograde patchy zoning in this sample is consistent with the adjustment of amphibole composition to recurrent changes in pressure and/or temperature in the course of subduction-related metamorphism.

Image source: García-Casco et al., 2006, High pressure metamorphism of ophiolites in Cuba. Geologica Acta 4, 63-88, and García-Casco et al., 2002. Oscillatory zoning in eclogitic garnet and amphibole, Northern Serpentinite Melange, Cuba: a record of tectonic instability during subduction? Journal of Metamorphic Geology 20, 581–598.

The calculated P-T path for SRO1A is clockwise with a) P-T oscillations (that account for reversals in garnet) during the prograde subduction-related path and b) decompression dominated retrogression. It should be noted that the P-T oscillations of the path suggest tectonic instability of the down-going slab, and that the Alpine-type retrograde portion of the path implies rapid exhumation and a relatively steep geothermal gradient, in all aspects similar to paths followed by eclogite blocks of central Cuba. These features strongly suggest the serpentinite-mélanges of western and central Cuba formed at the same Early Cretaceous subduction system that extended for a distance of about 800 km (present geographic coordinates), and that this system suffered a generalized (Aptian-Albian) tectonic event that terminated subduction.