title: Selective ingress of a Samoan plume component into the northern Lau backarc basin.
abstract: Intra-plate basalt isotopic trends require mixing between enriched mantle components (EM1, EM2, HIMU) and a primordial component with high (3)He/(4)He termed FOZO. However, proportions of components, geometric distributions within individual plumes, relative proportions of melting components and loci of mixing of melts and residues remain poorly understood. Here we present new Hf-Nd isotopic data of dredged sea floor basalts from the northern Lau backarc basin, ~250 km south of the subaerial and submerged Samoan chain, with high (3)He/(4)He, (20)Ne/(22)Ne and primordial (129)Xe/(130)Xe, characteristic of the FOZO component. Combined Hf-Nd-noble gas isotope systematics require mixing of refractory, sub-northwestern Lau backarc mantle only with a spatially restricted FOZO component, most plausibly sourced from part of the Samoan plume. Other geographically restricted and possibly volumetrically minor enriched Samoan plume components are not detectable in northern Lau backarc samples, consistent with selective plume ingress of the FOZO component beneath the basin.
authors.affiliation: 1] Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia [2] School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia.
authors.forename: Oliver
authors.initials: O
authors.lastname: Nebel
authors.affiliation: Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Arculus