HIGH NI-BEARING METAL AND SULFIDE PHASES IN THE D´ORBIGNY ANGRITE.

VARELA M.E.; HWANG S.L.; SHEN P; CHU, H-T; YUI T.F.; IIZUKA Y.

Houston

Conferencia; 46th Lunar and Planetary Science Conference; 2015

NASA

Introduction: Angrites are a small enigmaticgroup of achondrites. They are ancient rocks (e.g,LEW Cliff 86010: 4,558.55 ± 0.15 Ma and D?Orbigny:4,563.36 ± 0.34, [1-2]), that record an unusual primitivepetrogenetic history. Their origin is not yet clearlyunderstood. In part this is due to the few members ofthis group, a situation that is changing with the recentfinds in cold and hot deserts (e.g., [3]). D´Orbigny isby far the largest (16.55 kg) angrite known and is peculiarin several aspects. Its unusual shape, the presenceof plates of anorthite-olivine intergrowths, druseaugite crystals in void spaces and the abundant presenceof glass are some of the peculiarities. (e.g., [4-6]).Its mushroom-like shape is characterized by a frontand back shields having compact lithologies. Thespace between these shields is filled by a highly porouslithology, with open voids and hollow spheres.The study of new material from the porous lithologyreveals the presence of high content Ni-bearing metalwith sulfides. This abstract reports these findings andtheir implications regarding the redox conditions prevailingduring D'Orbigny formation