Hafnium isotopic variations in volcanic rocks from the Caribbean Large Igneous Province and Galápagos hot spot tracks

Abstract

[1] We report Hf isotope compositions of 79 lavas that record the early ($5-95 Ma) history of the Galápagos plume volcanism. These include lavas from the Caribbean Large Igneous Province (CLIP; $95-70 Ma), the accreted Galápagos paleo-hot spot track terranes (54-65 Ma) of Costa Rica (Quepos, Osa and Burica igneous complexes), and the Galápagos hot spot tracks (<20 Ma) located on the Pacific seafloor (Cocos, Carnegie, Malpelo, and Coiba Ridges and associated seamounts). These samples have previously been well characterized in terms of major and trace elements, Sr-Nd-Pb isotopes and Ar/Ar ages. As a result of the relative immobility of the high field strength and rare earth elements during synand post-emplacement hydrothermal activity and low-temperature alteration, combined Lu-Hf and Sm-Nd isotope systematics, when used in conjunction with Pb isotopes, provide a particular powerful tool, for evaluating the source compositions of ancient and submarine lavas. The combined Nd-Hf isotope data suggest that three of the isotopically distinct source components found today in the Galápagos Islands (the Floreana-like southern component, the Fernandina-like central component, and the depleted Genovesa-like eastern component) were present in the CLIP already by 95-70 Ma. The fourth Pinta-like northern component is first recorded at about 83-85 Ma by volcanism taking place during the transition from the plume head/CLIP to plume tail stage and has then been present in the hot spot track continuously thereafter. The identification of the unique northern and southern Galápagos Plume Hf-Nd-Pb isotope Pb and lower DeHf, a signature typical of the northern Galápagos island Pinta.

A 1.5 Ma record of plume-ridge interaction at the Western Galápagos Spreading Center (91°40′–92°00′W)

“…Magmatism along the Wolf-Darwin and other arcuate lineaments to the south of the WGSC has a slightly different composition from the material erupted at the WGSC over the last ≤1.4 Ma. Therefore the Quaternary Northern Galápagos Domain is more heterogeneous than previously thought but similar in composition to melts derived from the northern part of the Galápagos hotspot 11-15 Ma ago, providing further support that the Galápagos hotspot is compositionally zoned (Hoernle et al, 2000;Werner et al, 2003;Geldmacher et al, 2003;Kerr and Meriaux, 2004).…”

“…Ma (Hoernle et al, 2000;Werner et al, 2003;Geldmacher et al, 2003), leading to the proposition that the Galápagos plume is geochemically zoned. It was further proposed that the plume taps distinct reservoirs in its source area near the core-mantle boundary and preserves these geochemical heterogeneities through laminar flow, which then leads to a spatially zoned hotspot track.…”

Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia

“…Total chemistry blanks were b400 pg for Sr, Nd, Hf and Pb and thus considered negligible. Hafnium was separated following a two-column procedure as described by Geldmacher et al (2003). Hafnium isotope ratios were carried out on a VG Axiom multi-collector ICPMS (MC-ICPMS).…”

Evaluation of the effects of alteration and leaching on Sm–Nd and Lu–Hf systematics in submarine mafic rocks

“…Duncan and Hargraves, 1984;Kerr, 1996Kerr, , 2002Sinton et al, 1998), and several studies have recently applied Nd-Hf isotope systematics to unravelling their petrogenesis (Geldmacher et al, 2003;Thompson et al, 2004a). In contrast to Iceland, however, the Caribbean plateau is ~90 Ma and Caribbean plateau data thus require age correction.…”