Fe,Mg,Mn-bearing phosphates in the GRA 95209
meteorite: occurrences and mineral chemistry
Two large regions of Fe,Mg,Mn-bearing phosphates,together with metal and various silicate phases, have been observed in the GRA 95209 meteorite (a primitive achondrite belonging to the acapulcoite&endash;lodranite group). Numerous grains of an orthophosphate intermediate in composition between farringtonite and graftonite/sarcopside are found in association with Fe-and Mn-rich chladniite. The chladniite occurs as rims around the Ca-free phosphate (termed Mg-graftonite here) and along boundaries between Fe,Ni metal and silicate grains. Relict metal grains are included within both phosphates. Textures, as well as mineral compositions, suggest formation of Mg-graftonite by reaction of Fe,Ni metal with surrounding silicates (olivine and orthopyroxene). Chladniite probably formed both through replacement of Mg-graftonite and directly by reaction of metal with silicates, including plagioclase. Apatite appears to have played only a minor role in the formation of these phosphates.
Floss (1999) Am. Mineral. 84, 1354-1359.
Full publication: 1999_AM84_1354.pdf
Last revised: 12-2003