Isotope fractionation and concentration measurements of Zn in meteorites determined by the double spike, IDMS-TIMS techniques

Abstract

The isotope fractionation of Zn in meteorites has been measured for the first time using thermal ionization mass spectrometry and a double spiking technique. The magnitude of δZn ranged from -0.29 to +0.38‰amu-1 for five stone meteorites whereas the iron meteorite Canyon Diablo displays δZn of 1.11±0.11‰amu-1. The results for chondrites in this work can be divided into positive and negative δZn, supporting a previous proposal that chondrites are a mixture of materials from two different temperature sources. The Zn isotope fractionation present in meteorites may represent a primordial heterogeneity formed in the early solar system. An anomalous isotopic composition of Zn obtained for the Redfields iron meteorite suggests large-scale inherited isotope heterogeneity of the protosolar nebula, or the presence of a parent body that has formed within its own isotopically anomalous reservoir. These anomalies are in the same direction but smaller than nuclear field shift effects observed in chemical exchange reactions. The isotope dilution mass spectrometry (IDMS) technique was used to measure Zn concentration, yielding a range from 20.1μgg-1 to 302μgg-1 in five stone meteorites and from 0.019 to 26μgg-1 in seven iron meteorites. The IDMS-measured abundance of Zn in Orgueil is 302±14μgg-1 and should be considered for future compilations of the abundance of Zn in the solar system. © The Meteoritical Society, 2011.