In search of lost planets ¯ the paleocosmochemistry of the inner solar system

Mafic lavas from the central Nicaraguan portion of the Central American volcanic front exhibit considerable variability in the magnitude of high-field-strength element (HFSE) depletions. This variability cannot be attributed to variable magmatic differentiation, or more significantly, to variable depletion originating in the mantle wedge. Instead the HFSE depletions are thought to be the product of variable contributions from the subducting Cocos plate. Both subducted hemipelagic sediment and subducted oceanic crust are identifiable contributors to the overall signal. The latter could exert important control over HFSE depletions, but only if the dehydrating crust is rutile-saturated. Slab control over HFSE depletions is possible throughout the Central American subduction zone, even where slab contributions to magma generation are thought to be minimal, as in central Costa Rica. In some other subduction zones, slab control over HFSE depletions is apparent, but in others, such as the Marianas and the Aleutians, HFSE depletions are probably wedge-based.