MG-RICH ULTRAMAFICS OF THE NAGA HILLS OPHIOLITE, NAGALAND, INDIA: A POTENTIAL SUBSTITUTE AS BASIC FLUX IN METALLURGICAL INDUSTRIES

Abstract

Flux materials are indispensable in iron ore refining process to effectively segregate gangue minerals and to improve other physicochemical properties. Lately, the demand for metallurgical grade flux materials such as limestone and dolomite for iron and steel manufacturing industries in India has surged manifold and depends largely on imports due to its limited resources. MgO-bearing flux has emerged to be a potential alternative to conventional fluxes (limestone and dolomite); though huge resources of Mg-rich ultramafic rocks are available in the Indian subcontinent, their economic utility as metallurgical flux is not fully explored. To evaluate the suitability of flux material in iron and steel industries, Mg-rich ultramafics of the Naga Hills Ophiolite (NHO) have been studied. Major oxides and petro-mineralogical studies have been undertaken to understand the chemical and mineralogical attributes of NHO Mg-rich ultramafics. Results indicate appreciable MgO content (up to 46.7%) barring pyroxenite, with low Al2O3 (< 2 wt%), loss on ignition (< 14 wt%), and Cr2O3 (< 1 wt%) conforming to the chemical specifications set for flux/sinter mix by the major steel producers in India. Fouling index further indicates Mg-based flux of NHO as better quality in contrast to conventional flux materials, albeit alkali content is relatively high. Finer crystals of NHO Mg-rich rocks are added advantage which would readily assimilate in the melt at lower energy. Mg-based flux in iron and steel industries would aid in augmenting productivity with reduced slag volumes at lower cost, energy and pollution.