Factors controlling entrapment of platinum-group minerals in chromite, Troodos, Cyprus

Chromite from the Troodos massif, Cyprus, contains ubiquitous inclusions of platinum-group minerals (PGM), 90%, of which are laurite of up to 20µm in diameter. Determination of iron valence in chromite by microprobe suggests that PGM’s are preferentially trapped in zones (sectors) of increased Fe³⁺/Fe²⁺ ratios. Raman spectra confirm this observation indicating in such zones ferritchromite peak at 726 cm^-1, and trace laurite bond at 355.8 cm^-1. Atomic force microscope (AMF) studies show that chromite zones are 3-4µm wide. Zonation is disturbed around PGM’s inclusions. Microareas of chromite surrounding PGM inclusions are slightly enriched in Mg and depleted in Cr.