Nickeliferous opaque minerals associated with chromite alteration in the Sakhakot-Qila complex, Pakistan, and their compositional variation

Abstract

Chemical compositions of the awaruite-heazlewoodite-pentlandite assemblage from the Sakhakot-Qila ultramafic complex, Pakistan, indicate its genesis in highly reducing conditions with f o 2 and f s 2 much below those yielding nickel sulphide ores. The compositions from various parts of the complex exhibit larger variations than those reported so far from a single complex, and include unusually high Ni contents. Awaruite compositions extend beyond the previously known limit of Ni content, and are unique in containing Cu and not Co as the third constituent after Ni and Fe; with sympathetic relation between Cu and Ni. Previous reports indicate genesis of such minerals by serpeatinization only, but the present example links them to chloritization and the formation of ‘ferritchromit’ as well. Their petrographic distribution is related to that of chromite grains and segregations and not to that of serpentine.