26 mai : Séminaire de Yamirka Rojas-Agramonte
The Caribbean: A natural laboratory to understand the consequences of ridge subduction and the evolution of intraoceanic arc systems
Yamirka-Rojas-Agramonte, Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Germany
The present-day Caribbean region developed since early/mid-Jurassic in three main phases:
- ~ 180 Ma- rifting of Pangea and formation of a spreading ridge in the Proto-Caribbean,
- ~150 – 70 Ma- drifting and spreading apart of North and South America and development of an oceanic basin (the Proto-Caribbean) connected with the Central Atlantic;
- ~135 – 50 Ma- complete subduction (including the ridge) of the Proto-Caribbean and Central Atlantic basin and insertion of the Farallon (Pacific)-derived Caribbean plate in between the Americas.
One evidence suggesting subduction of the Proto-Caribbean spreading ridge is the formation of ca. 120 Ma anatectic adakitic liquids after melting of subducted (50 km) hot-young Proto-Caribbean MORB in Eastern Cuba (La Corea and Sierra del Convento mélanges; García-Casco et al., 2008; Blanco-Quintero et al., 2010; Lázaro et al., 2011), also emplaced at shallow depths in the Cordillera Central of the Dominican Republic (Escuder-Viruete et al., 2007) and Haiti (Rojas-Agramonte et al., 2021) during the mid-late Cretaceous.
Studies on U-Pb zircon geochronology, Lu-Hf, and 18O/16O isotope systematics from Cretaceous upper-mantle rocks and juvenile intra-oceanic volcanic arc in the Greater Antilles (Cuba and Hispaniola) reported old inherited zircon grains ranging from 200 Ma to 3.0 Ga (Proenza et al., 2018; Rojas-Agramonte et al., 2016; Torró et al., 2018). These ages are similar to those of zircons from nearby crustal regions in northern Central America, Mexico and northern South America. These studies concluded that detrital zircons of sediments deposited in the Proto-Caribbean/Atlantic were transferred to the sub-arc mantle of the Caribbean plate by means of subduction. Moreover, the presence in Hispaniola of Quaternary alkali basalts with isotopic EM1-l affinities, led Kamenov et al. (2011) to propose an ancient subcontinental lithospheric mantle (SCLM) source with Gondwana affinity entrained beneath the island likely derived from a Grenvillian terrane in Central America or Mexico. An undefined “tectonic interaction” of the intraoceanic arc with such a terrane was proposed by these authors.
In this talk I explore how subduction of the proto-Caribbean ridge may help explaining the presence of old zircons and a SCLM fragment below the Caribbean arc.