The response of zircon to the extreme pressures and temperatures of a lightning strike.

ABSTRACT: Hypervelocity impacts can produce features in zircon that are not normally produced by endogenic processes. However, lightning can also induce extreme pressure-temperature excursions, and its effect on zircon has not been studied. With the aim to recognise features that form in response to extreme pressure-temperature excursions but are not unique to hypervelocity impacts, we imaged and undertook microstructural characterization of zircon in a fulgurite (a tubular body of glass and fused clasts that formed in response to a lightning strike). We document zircon with granular ZrO₂ and rims of vermicular ZrO₂, features which vary in abundance with increasing distance from the fulgurite's central void. This indicates that these features formed in response to the lightning strike. Zircon dissociation to ZrO₂ and SiO₂ is a high-temperature, relatively low-pressure phenomenon, consistent with previous suggestions that lightning strikes involve extreme temperatures as well as pressures greater than those usually generated in Earth's crust but rarely?>?10 GPa. The rims of monoclinic ZrO₂ record crystallographic evidence for precursor cubic ZrO₂, demonstrating that cubic ZrO₂ is not unique to hypervelocity impacts. Given the likelihood that this fulgurite experienced pressures of, at most, a few GPa, evidence for cubic ZrO₂ indicates peak temperatures?>?2000 °C.

SUBMITTER: Kenny GG 

PROVIDER: S-EPMC7810979 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature