The Netherlands 4 ° Ar / agAr AND UPb EVIDENCE FOR LATE PROTEROZOIC ( GRENVILLE-AGE ) CONTINENTAL CRUST IN NORTH-CENTRAL CUBA AND REGIONAL TECTONIC IMPLICATIONS

Renne, P.R., Mattinson, J.M., Hatten, C.W., Somin, M., Onstott, T.C., Millfin, G. and Linares, E., 1989. 4°Ar/39Ar and U-Pb evidence for Late Proterozoic (Grenville-age) continental crust in north-central Cuba and regional tectonic implications. Precambrian Res., 42: 325-341. Central Cuba is composed of fault-bounded tectonostratigraphic terranes juxtaposed and deformed during plate collision and subsequent transform motion between the Caribbean and North American plates in the Late MesozoicCenozoic. One of these, the Las Villas terrane, contains crystalline basement rocks thought to be pre-Upper Jurassic on stratigraphic grounds. The Socorro Complex occurs in the northwestern Las Villas terrane, and consists of marbles and siliciclastic metasedimentary rocks, and the Rio Carla Granite. An 4°Ar/39Ar plateau date of 903.5 _+ 7.1 Ma for phlogopite from a marble corroborates previous K-Ar dates from this unit, and establishes unambiguously a Late Proterozoic age for high-grade metamorphism. Discordance of the 4°Ar/agAr age spectrum can be reliably attributed to diffusive Ar loss, which if modeled as an episodic thermal event implies a reheating age that closely coincides with the Late-Cretaceous-Paleogene collision between the Caribbean and North American plates. U-Pb zircon data indicate an intrusive age of 172.4 Ma for the Rio Carla Granite, and reveal an inherited zircon component with an age of ~ 900 Ma. Radio-isotopic data from the Socorro Complex display no evidence of Pan-African age thermal overprinting. These observations, combined with constraints provided by published results from nearly Pangean landmasses, suggest that the complex lay substantially to the southwest (present-day co-ordinates) during the Early Paleozoic. Following its genesis in the mid-Mesozoic, the Caribbean plate evidently transported fragments of an extensive Grenville-age belt that spanned the Americas during the Late Proterozoic.

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