Accreted terranes, comprising a wide variety of Late Jurassic and Early
Cretaceous igneous and sedimentary rocks are an important feature of
Cuban geology. Their characterization is helpful for understanding
Caribbean paleogeography.
The Guaniguanico terrane (western Cuba) is formed by upper Jurassic
platform sediments intruded by microgranular dolerite dykes. The
geochemical characteristics of the dolerite whole rock samples and their
minerals (augitic clinopyroxene, labradorite and andesine) are
consistent with a tholeiitic affinity. Major and trace element
concentrations as well as Nd, Sr and Pb isotopes show that these rocks
also have a continental affinity. Sample chemistry indicates that these
lavas are similar to a low Ti-P2O5 (LTi) variety of continental flood
basalts (CFB) similar to the dolerites of Ferrar (Tasmania). They
derived from mixing of a lithospheric mantle Source and an asthenopheric
component similar to E-MORB with minor markers of crustal contamination
and sediment assimilation. However, the small quantity of Cuban magmatic
rocks, similarly to Tasmania, Antarctica and Siberia differs from other
volumetrically important CFB occurrences Such as Parana and Deccan.
These dolerites are dated as 165-150 Ma and were emplaced during the
separation of the Yucatan block from South America. They could in fact
be part of the Yucatan-South America margin through which the intrusive
system was emplaced and which was later accreted to the Cretaceous arc
of central Cuba and to the Palaeogene arc of eastern Cuba. These samples
could therefore reflect the pre-rift stage between North and South
America and the opening of the gulf of Mexico.