David Hilton, Ph.D.

scripps institution of oceanography

My work on the helium and argon isotope systematics of the Lau Basin was amongst the first to show the combined effects of shallow-level magma chamber degassing effects on helium isotopes (ratios decreased as a function of magmatic differentiation) and argon isotopes (40Ar/36Ar became atmosphere-like). Because all samples were well-characterized (for trace elements and radiogenic isotopes - Sr, Nd and Pb) the study was able to show that decoupling of various geochemical tracers (He and Pb isotope variations for example) was due to different provenance: radiogenic helium was derived from the uppermost crust whereas radiogenic lead was indicative of a subducted sediment contribution. The paper included a far-ranging discussion on tracing magma provenance in arcs, back-arcs, spreading ridges and hotspots, and formed the basis for a number of subsequent papers where ideas of mantle-crust interactions at different tectonic locations were developed and tested. Current studies are focusing on the Manus Basin in the Bismark Sea as this back-arc region also records a hotspot component superimposed upon the slab/MORB mixture.