HR: 17:30h
AN: T44A-07    [Abstracts]
TI: Geochemistry of Cretaceous Magmatism in Eastern Cuba: Recycling of North American Continental Sediments and Implications for the Subduction Polarity in the Greater Antilles Paleo-arc
AU: * Marchesi, C
EM: claudio@ugr.es
AF: Departamento de Mineralogia y Petrologia, Universidad de Granada, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AU: * Marchesi, C
EM: claudio@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AU: Garrido, C J
EM: carlosg@ugr.es
AF: Departamento de Mineralogia y Petrologia, Universidad de Granada, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AU: Garrido, C J
EM: carlosg@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AU: Bosch, D
EM: delphine.bosch@gm.univ-montp2.fr
AF: Geosciences Montpellier, Equipe Manteau-Noyau, CNRS-Universite Montpellier II, Place E.Bataillon, Montpellier, 34095, France
AU: Proenza, J A
EM: japroenza@ub.edu
AF: Departament de Cristal lografia, Mineralogia i Diposits Minerals Universitat de Barcelona, Facultat de Geologia, C. Marti y Franques s/n, Barcelona, 08028, Spain
AU: Gervilla, F
EM: gervilla@ugr.es
AF: Departamento de Mineralogia y Petrologia, Universidad de Granada, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AU: Gervilla, F
EM: gervilla@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, Facultad de Ciencias, Avenida Fuentenueva s/n, Granada, 18002, Spain
AB: We present whole rock major and trace element data and Nd-Sr-Pb radiogenic isotope ratios of Cretaceous igneous suites from eastern Cuba. These rocks are related to the Greater Antilles paleo-island arc magmatism and have three different igneous styles. Group 1 consists of tholeiitic basalts and rare basaltic andesites that have N-MORB-like compositions similar to those found in back-arc basin basalts (TiO2 = 1.2-2.9 wt%; La/Yb(N) = 0.7-0.9, Th/Nb = 0.06-0.08, and initial 208Pb/204Pb = 37.65-37.74). Group 2 comprises basaltic and rare basaltic andesitic subvolcanic dykes with major-, trace-element and isotopic compositions similar to island arc tholeiites (TiO2 = 0.7-1.4 wt%; La/Yb(N) = 0.6-0.9, Th/Nb = 0.06-0.68, and initial 208Pb/204Pb = 37.74-38.25). Group 3 is composed of low-Ti (TiO2 = 0.3-0.9 wt%) calcalkaline igneous rocks that have an unambiguous subduction- related character (La/Yb(N) = 1.1-5.0, Th/Nb = 0.35-1.55, and initial 208Pb/204Pb = 37.94-38.39). The parental magmas of the three groups formed by variable melting degrees (< 5-25%) of spinel lherzolite, with the more depleted mantle sources for Groups 2 and 3 than Group 1. The trace element and radiogenic isotope compositions of primitive Group 3 samples are strongly bimodal. One subgroup of samples is characterized by low Ta/Yb (0.02-0.03) and Th/La (0.10-0.13), slightly subchondritic Nb/Ta (13.3-17.3), and relatively high initial 206Pb/204Pb (18.57-18.62) and åNd (7.6-9.4). The remaining primitive Group 3 samples have higher Ta/Yb (0.06-0.11) and Th/La (0.24-0.32), highly subchondritic Nb/Ta (7.6-9.1), coupled with lower initial 206Pb/204Pb (18.24-18.29) and åNd (3.4-5.5). These signatures were induced by two distinct slab components that mainly reflect the contributions of Cretaceous Atlantic marine and North American continental sediments, respectively. Nb/Ta in the first subgroup was induced by melting of rutile-bearing subducted crust, whereas in the second it was inherited from recycled continental material. The involvement of Atlantic and North American sediments in Cuban Cretaceous magmatism indicates that the Proto-Caribbean (North American-Proto Atlantic) lithosphere subducted beneath the Greater Antilles arc during Late Cretaceous (pre-Campanian) time, consistently with geotectonic models involving onset of south-westward-dipping subduction beneath the Greater Antilles paleo-arc during the Aptian. The variable source depletion and magnitude of subduction component probably reflect different settings across arc, from the arc front to a back-arc spreading ridge.
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8185 Volcanic arcs
DE: 8410 Geochemical modeling (1009, 3610)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting