|Title||Evaporative fractionation of zinc during the first nuclear detonation|
|Publication Type||Journal Article|
|Year of Publication||2017|
|Authors||Day JMD, Moynier F, Meshik AP, Pradivtseva OV, Petit DR|
Volatile element and compound abundances vary widely in planets and were set during the earliest stages of solar system evolution. Experiments or natural analogs approximating these early conditions are limited. Using silicate glass formed from arkosic sands during the first nuclear detonation at the Trinity test site, New Mexico, we show that the isotopes of zinc were fractionated during evaporation. The green silicate glasses, termed “trinitite,” show +0.5 ± 0.1‰/atomic mass unit isotopic fractionation from ~200 m to within 10 m of ground zero of the detonation, corresponding to an α fractionation factor between 0.999 and 0.9995. These results confirm that Zn isotopic fractionation occurs through evaporation processes at high temperatures. Evidence for similar fractionations in lunar samples consequently implies a volatile-depleted bulk Moon, with evaporation occurring during a giant impact or in a magma ocean.
The new results from trinitite provide the first definitive evidence for evaporative fractionation of zinc during high-temperature conditions and are consistent with subdued fractionation factors for Zn. Pressure conditions are more difficult to ascertain, but elevated pressures are likely during planetary formation or during global magma ocean phases on planetary bodies, when volatile loss led to nascent atmospheres. These results strongly support the loss of Zn and other volatile and moderately volatile elements through evaporative fractionation effects during the formation and evolution of the Moon, as well as other planetary bodies.