Abstract

Electron-probe microanalyses and scanning electron microscopy of chrornitites
from some ultramafic members of Neyriz ophiolite indicate that sulifides of platinum-
group minerals (PGMs) occur as solid inclusions in chromite grains. Laurite
with the general formula of (Ru ,Os ,lr ) S , and erlichmanite are the main
identified sulfide phases. The PGMs occur as 4 to 20 microns euhedral to rectangular
inclusions, and seem to be confined to massive chrornitite deposits. The PGMs do not
seem to have exsolved from chromite, it is believed that their crystallization has taken
place prior and/or during the crystallization of this mineral. Some secondary minerals
of rare earth elements (REEs) were also found to fill the micro cracks and fractures
in chromite grains. Semiquantitative analyses reveal the presence of appreciable
amounts of Ce and La along with some minor quantities of Gd, Eu, Pr, and Nd. These
secondary minerals are extremely small and none were found to be larger then 10
microns in diameter. Some base metal alloys (largely made of Ni-Fe), along with
magnetite, ferritechromite, and some olivine and pyroxene silicate inclusions are also
reported.