NUCLEAR-BLAST INDUCED NANOTEXTURES IN TRINITITE QUARTZ AND ZIRCON GRAINS

The intense heat and pressure resulting from the detonation of the world’s first nuclear device in the New Mexico desert, 16 July, 1945, severely altered the arkosic desert sand, producing the fused, glassy material referred to as Trinitite. The study of Trinitite is key to the development of nuclear forensic techniques that can provide crucial information about a nuclear event, such as device composition and radionuclide distribution. Moreover, nuclear blasts are often considered analogues to catastrophic natural events such as meteorite impacts, and it is well-documented that with increasing impact severity, zircon and quartz grains deform systematically. In Trinitite, a sufficient number of primary quartz and zircon grains remain identifiable. Here, a multi-technique approach (focused ion beam, scanning electron microscopy, aberration-corrected transmission electron microscopy, and micro-Raman spectroscopy) is employed to study the micron-to-nanometer-scale deformation features in altered grains in order to constrain blast pressure and temperature. Trinitite zircon grains consistently show an outer halo of fibrous baddeleyite, radiating from a relatively unaltered core; HRTEM images show complex martensitic twinning, likely originating from an intermediate, tetragonal zirconia precursor. Trinitite quartz grains show various states of melting that appear to vary predictably with depth. Grains occurring deeper than ~1.5 cm are crystalline, with occasional planar fractures at the optical scale. At shallower depths, a systematic increase in quartz vitrification is observed. Considered together, these data suggest maximal temperatures in excess of 1500 °C and pressures of <10 GPa, the latter being considerably less than for any natural impact event.