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Late Jurassic continental flood basalt doleritic dykes in northwestern Cuba: remnants of the Gulf of Mexico opening

¹ Institut de Minéralogie et de Géochimie, Université de Lausanne, Bât Anthropole, CH1015, Lausanne, Switzerland.
² LGCA, UMR CNRS 5025, Maison des Géosciences, Université Joseph Fourier Grenoble 1, 1381 rue de la piscine, 38041 Grenoble, France.
³ LGCA, UMR CNRS 5025, Université de Savoie, F.73376 Le Bourget du Lac, France
⁴ Universidad Autonoma de Nuevo Léon, Facultad de Ciencias de la Tierra, Carr. A Cerro Prieto km 8, ex-hacienda de Guadelupe, CP 67700, A P 104, Linares, Nuevo Leon, Mexico.

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 paleo-geography.

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.

Key Words: Dolerite dykes • Upper Jurassic • Continental flood basalts • Geochemistry • Cuba