Mass dependent and independent Mo isotopic composition of the mafic rocks of Acasta Complex

抄録

In an attempt to understand the late accretionary history of Earth, we investigated Archean rocks from Acasta complex. The Acasta Gneiss complex hosts the oldest rocks preserved on Earth with a crystallization age of 4.03 Ga [1]. Molybdenum isotopes provide important insights into the late accretionary history of our planet. Due to its moderately siderophile character, Mo partitioned largely into the core and the present day bulk silicate Earth Mo isotope composition is an integration of the original and late accreted material [2].Although mass independent (nucleosynthetic) Mo isotope anomalies are a valuable tool in constraining genetic relationship among meteorites and planetary materials, spurious Mo mass independent anomalies can result from a mass dependent fractionation of Mo isotopes [3]. We have conducted a Mo isotopic investigation of several mafic and intermediate rocks from the Acasta Complex, that have been least affected by later events involving widespread migration of fluid mobile elements [4].Ref [1] Reimink et al. (2019) Earth s Oldest Rocks. [2] Dauphas (2017) Nature 541. [3] Budde et al. (2023) Geochemistry, 83. [4] Koshida et al. (2016) Precam. Res. 283.