Potential deposits of selected metallic resources on L chondrite parent bodies

Abstract

The authors have undertaken research aimed at determining the abundance of metallic resources on parent bodies of ordinary chondrites. In this report, they present their findings concerning L chondrites, whose parent S asteroids make about 17% of all asteroids in the main belt and ca. 66% of NEAs. The abundances, and their variations, of selected metals in the rocks of L chondrites were studied based on a bulk chemical composition analysis. The authors also analysed the abundances of selected metals in FeNi alloy grains crystallizing in the forms of kamacite, taenite and tetrataenite. These are the only minerals that they considered to be ore minerals forming potential deposits of metallic resources on L chondrite parent bodies. Further analyses focused on the distribution and concentration of FeNi alloy grains in L chondrite rocks, and finally also on the influence of the structure of rocks building the surfaces of asteroids on the feasibility and the method of extracting metallic resources from these bodies. The conducted analyses demonstrated that the abundances of Fe, Ni, Cr, Co, Cu and Au on L chondrite parent bodies are higher, and the abundances of REE – much lower than those in the Earth's crust, where the majority of the currently mined metallic resources are found. Ni content in L chondrite rocks is 1.7 times as high as that in terrestrial nickel deposits, and Co content – 2.5 times as high as its minimum abundance in terrestrial deposits. As Fe, Ni, Co, Cr, Cu and Au occur in parent bodies in mineral association, they form polymetallic deposits. Co and Ni could be considered the main mineral resource on the parent asteroids of L chondrites, while Fe, Au, Cu and Cr could be accompanying minerals.Rocks with the composition of L chondrites contain 9.2 wt% of FeNi grains distributed evenly throughout the rock. Ore mineral content does not change with depth on ordinary chondrite parent bodies with onion shell structure and it is the same in pieces of regolith from the rubble pile asteroids. The high abundance of ore minerals and their even distribution in space make it possible to regard the whole asteroid as an abundant deposit of metallic resources. Metallic resources are also found on asteroid surfaces, which could enable open-pit mining at any place without previous prospection work or the need to remove the overburden. The presence of regolith and the high porosity of rocks underlying it directly will considerably facilitate the crushing of the excavated material and processing the ore. The estimated Ni and Co resources on 4179 Toutatis asteroid, being the most likely the parent body of L chondrites, would satisfy the current needs of the humankind for the nearest 200 years, and Cr, Fe, and Au resources – for a few years.