Iron Isotope Fractionation During Magmatic Differentiation in Kilauea Iki Lava Lake

Abstract

Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stagemeltveins are 0.2 permil (per thousand) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2 per thousand lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.

Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

“…3b) This is supported by the absence of porous pyrites in our sample from this reef. Dominion Reef pyrite and chalcopyrite from underlying and overlying rocks display a relatively small range of δ 56 Fe values, which is within the range of igneous δ 56 Fe values in mantle-derived rocks, including bulk rocks and mineral separates (Poitrasson and Freydier, 2005;Heimann et al, 2008;Teng et al, 2008;Schoenberg et al, 2009). This range is also consistent with experimental studies of Fe isotope fractionation at magmatic temperatures (Shuessler et al, 2007;Shahar et al, 2008).…”

The Mg isotopic systematics of granitoids in continental arcs and implications for the role of chemical weathering in crust formation

“…As far as we know, there is no evidence so far of high-temperature stable isotope fractionations large enough to explain the heavy Mg isotope signatures of the granites (13,14). The only exception is that of Fe isotopes (30), but Fe isotope fractionation is likely to be caused by redox reactions, which are absent for Mg. In any case, correlations with radiogenic isotopes are inconsistent with this hypothesis.…”

Nitrogen in peridotite xenoliths: Lithophile behavior and magmatic isotope fractionation

“…The large isotopic effects observed among co-genetic mineral phases warn against oversimplified interpretations of N isotopic variations as source signatures, and demonstrate the need to take into account isotopic fractionation of light elements during magmatic processes such as partial melting (Burnard, 2004), crystallization (Teng et al, 2008) and kinetic isotope exchanges during entrainment (Deloule et al, 1991;Peslier and Luhr, 2006;Jeffcoate et al, 2006). Furthermore, different metasomatic pulses could involve different batches of a single melt having evolved through crystal fractionation and/or interaction with other minerals in the mantle (Navon and Stolper, 1987), potentially involving the diffusive exchange.…”