Moderately volatile element behaviour at high temperature determined from nuclear detonation

Abstract

The first nuclear detonation, at the Trinity test site, is an analogue for high temperature volatile loss during planet formation processes. We report Cu isotope and abundance data, comparing them with Zn and K isotopes in trinitite glasses sampled with distance from the detonation centre. Copper concentrations drop, and isotopic compositions become ~0.3 % higher with proximity to the detonation. Relative sensitivity to high temperature evaporative isotopic fractionation processes occur in the order: Zn > Cu >> K. Lower volatility of K relative to Cu and Zn results from its low activity coefficient in silicate melts. Lunar mare basalt and some tektite Cu, Zn and K isotope compositions can be modelled using empirical fractionation factors (α) derived from trinitite. Combined with isotopic variations measured in mare basalts, the results support volatile loss during a magma ocean phase for the Moon.