Magma source evolution beneath the Caribbean oceanic plateau: new insights from elemental and Sr-Nd-Pb-Hf isotopic studies of ODP Leg 165 Site 1001 basalts

Abstract

Ocean Drilling Project Leg 165 sampled 38 m of the basaltic basement of the Caribbean Plate at Site 1001 on the Hess Escarpment. The recovered section consists of 12 basaltic flow units which yield a weighted mean Ar/Ar age of 80.9 + 0.9 Ma. The basalts (6.4-8.5 wt% MgO) are remarkably homogeneous in composition and are more depleted in incompatible trace elements than N-MORB. Depleted initial radiogenic isotope ratios (1 Nd þ11.1 to þ11.9; 1 Hf þ15.2 to þ16..90) reveal a long-term history of depletion. Although the Site 1001 basalts are superficially similar to N-MORB, radiogenic isotopes in conjunction with incompatible trace element ratios show that the basalts have more similarity to the depleted basalts and komatiites of Gorgona Island. This chemical composition strongly implies that the Site 1001 basalts are derived from a mantle plume-depleted component and not from depleted ambient upper mantle. Therefore the Site 1001 basalts are, both compositionally and tectonically, a constituent part of the Caribbean oceanic plateau. Mantle melt modelling suggests that the Site 1001 lavas have a composition which is consistent with second-stage melting of compositionally heterogeneous mantle plume source material which had already been melted, most likely to form the 90 Ma basalts of the plateau. The prolonged residence (.10 Ma) of residual mantle plume source material below the region confirms computational model predictions and places significant constraints on tectonic models of Caribbean evolution in the Late Cretaceous.

Accreted seamounts in North Tianshan, NW China: Implications for the evolution of the Central Asian Orogenic Belt

“…Pooled fractional melt calculations have been used to model the composition (depleted vs. primitive mantle) and mineralogy (lherzolite containing either spinel or garnet or a 50:50 mix representing melting across the transition zone) of the source region (Aldanmaz et al, 2006;Kerr et al, 2004Kerr et al, , 2009. Partition coefficients are averages from Salters et al (2002) and McDade et al (2003).…”

Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

“…These mineralogical and geochemical data indicate that the Loma Peguera chromitites are rather unusual when compared with those commonly occurring in mantle harzburgite associated with supra-subduction zone ophiolites (Proenza et al 2007). Very likely they formed close to plume-proximal spreading ridges and as part of oceanic plateaus, in particular in the so-called Caribbean Plateau described by Kerr et al (2009). Therefore, following the classification proposed by Dilek & Furnes (2011), the Loma Peguera chromitites are hosted by a plume-type ophiolite.…”

Late Cretaceous arc development on the SW margin of the Caribbean Plate: Insights from the Golfito, Costa Rica, and Azuero, Panama, complexes

“…Figure 6. Geochemical characteristics of the igneous rocks of the Golfito Complex and Azuero Marginal Complex, with comparison to the "Sámara Arc" , "Morti Arc" , East Pacific Rise MORBs (EPR) [Su and Langmuir, 2003], Nicoya Complex (oceanic plateau) [Hauff et al, 2000], Tonga Arc [Turner and Hawkesworth, 1997], Lau Basin [Turner and Hawkesworth, 1997], Mariana Arc and Trough (GEOROC online database), and CLIP basalts from the Caribbean Sea (locations in Figure 1) [Sinton et al, 1998;Révillon et al, 2000;Kerr et al, 2002Kerr et al, , 2009 affinities [Kerr, 2003], (2) some circum-Caribbean igneous complexes interpreted to be part of the CLIP have a controversial origin and may pertain to distinct oceanic plateaus [e.g., Kerr, 2005;, and (3) high compositional variability of CLIP basalts recovered by drilling and dredging in the Caribbean Sea is observed at a scale much larger than that of the Azuero Marginal Complex and is not observed at individual sites [Sinton et al, 1998;Révillon et al, 2000;Kerr et al, 2002Kerr et al, , 2009 (see also ODP and IODP sites in Figures 1 and 6).…”