The provenance of metal in anorthositic rocks

Calculated compositions for metal crystallized from anorthositic melt rocks or feldspathic basalts such as 14310, 68415, and 77017 are (1) meteoritic in the initial stages or if metal is the only phase crystallized, and (2) higher in Co than meteoritic metal as a result of fractional crystallization of metals and silicates. Metal in coarse anorthositic rocks 15415, 15455, 60015, 64435, and 78238 is not of meteoritic composition and has Co contents from 0 to 9% with a Ni/Co ratio of about 1. The formation of anorthosites and the composition of the earliest metal are discussed with attention to Ni concentrations and the Ni/Co ratio. It is shown that anorthositic hornfels and breccias contain metal of a composition not found in their source material, coarse anorthosite; it is suggested that the hornfels includes metal grains probably derived with little change in composition from ancient meteorites.