Normative calculation of mineral composition in Cr ores of the ophiolite complexes from SE Iran

Specific elements (Cr, Al, Ca, and Si) and loss on ignition (LOI) were used for semi-quantitative determination of the normative mineralogical composition of naturally occurring chromium ores in ophiolite complexes. By far the occurring ore minerals are complex both from the mineralogical and chemical viewpoints. The secondary minerals serpentine and Cr-containing chlorite (kaemmererite) form next to the spinel, the most abundant mineral in the ores. As a secondary formed mineral, Cr-containing garnet (uvarovite) is very rare. Among the primary minerals olivine occurs most often. Diopside plays a subordinate role. The amounts calculated for mineral associations of chromium ores occurring in south-eastern Iran are sufficiently accurate. The sum of calculated mineral contents varies from 83 to 108 wt. %. In the application of the normative procedure, Mg, Fe, Mn and Ni were not used for the calculation. Therefore, tests could be performed by comparing the measured Mg, Fe, Mn and Ni contents with the amounts of these elements deriving from normative calculation. The results are satisfactory, considering of the general problems of quantitative phase analysis of mineral associations.