Workshop on Chronology of Meteorites (2007) 4033.pdf 182 HF-182 W CHRONOMETRY AND THE ORIGIN AND EVOLUTION OF PLANETARY BODIES. T. Kleine 1, M. Touboul 1, B. Bourdon 1, K. Mezger 2, H. Palme 3, F. Nimmo 4, S.B. Jacobsen 5, and Q.Z. Yin 6. 1IGMR, Dept. Earth Sci., ETH Zurich, CH-8092 Zurich (
[email protected]), 2Inst. Min., Univ. Münster, D-48149 Münster, 3Inst. Geol. Min., Univ. Köln, D-50674 Köln, 4Dept. Earth Planet. Sci., UCSC, Santa Cruz, CA95064, USA, 5Dept. Earth Planet. Sci., Harvard Univ., MA 02138, USA, 6Dept. Geol., UCD, Davis, CA 95616, USA. Introduction: In the past ~15 years 182 Hf-182 W dicate that heating by 26 Al decay was the dominant heat chronometry has successfully been applied to provide source for the thermal metamorphism. Hf-W ages for time constraints for a variety of processes and events acapulcoites and lodranites are ~6 Ma [18]. Compari- associated with the formation and earliest evolution of son with ages obtained from other chronometers re- planetary bodies. The main interest in the Hf-W system veals that, although acapulcoites/lodranites were heated was initially related to its potential for dating core for- to much higher temperatures than H6 chondrites, they mation [1-3] but Hf-W fractionations do not only occur cooled faster than the H6 chondrites. This in conjunc- during core formation but also during partial melting tion with the higher peak temperatures of acapulco- and fractional crystallization [4,5]. This allows the ites/lodranites indicates that their parent body was timescales of mantle differentiation (e.g., magma ocean smaller and accreted earlier than the H chondrite parent crystallization) to be determined.