Silica-rich volcanism in the early solar system dated at 4.565 Ga

Abstract

The ranges in chemical composition of ancient achondrite meteorites are key to understanding the diversity and geochemical evolution of planetary building blocks. These achondrites record the first episodes of volcanism and crust formation, the majority of which are basaltic. Here we report data on recently discovered volcanic meteorite Northwest Africa (NWA) 11119, which represents the first, and oldest, silica-rich (andesitic to dacitic) porphyritic extrusive crustal rock with an Al–Mg age of 4564.8 ± 0.3 Ma. This unique rock contains mm-sized vesicles/cavities and phenocrysts that are surrounded by quench melt. Additionally, it possesses the highest modal abundance (30 vol%) of free silica (i.e., tridymite) compared to all known meteorites. NWA 11119 substantially widens the range of volcanic rock compositions produced within the first 2.5–3.5 million years of Solar System history, and provides direct evidence that chemically evolved crustal rocks were forming on planetesimals prior to the assembly of the terrestrial planets.

Abstract

Achondritic meteorites can record volcanism and crust formation on planetesimals in the early Solar System. Here, the authors date the Northwest Africa 11119 meteorite with an Al-Mg age of 4564.8 ± 0.3 Ma indicating that this is the earliest evidence of silicic volcanism in the Solar System to date.