Telluric iron assemblages as a source of prebiotic phosphorus on the early Earth: Insights from Disko Island, Greenland

Abstract

Phosphorus is one of the key elements, which determined the emergence of primordial life on our planet. The source of prebiotic phosphorus was most likely to be easily soluble compounds containing phosphorus in the negative form of oxidation (e.g., phosphides). The present paper is the first thorough investigation of phosphide-bearing mineral assemblages confined to telluric (terrestrial) native iron from volcanic rocks of Disko Island, Greenland. Phosphorus speciation in given assemblages varies from the solid solution in native iron (up to 0.3 wt.% P), different phosphides – schreibersite Fe₃P, nickelphosphide Ni₃P, barringerite Fe₂P, and phosphates, including fluorapatite, anhydrous Fe-Na phosphates, phosphoran olivine and pyroxene (up to 1 wt.% P). The diversity of observed phosphorus speciation can be explained by the steep changes of redox conditions during subsurface crystallization of iron-phosphide-bearing lavas. Based on the available data on likely redox conditions on the early Earth, we hypothesize that reactive prebiotic phosphorus may have originated from shallow crustal rocks.