Ecandrewsite and zincian manganoan ilmenite from albitite veins of South Khetri Fold Belt, Rajasthan-implications in mineral search for basemetal-gold-uranium

Abstract

Ecandrewsite mineral occurs within albitite vein intruded within the Udaipurwati granite gneiss from South Khetri Belt (SKB), Rajasthan, India. Microprobe analysis of the ecandrewsite gave compositional range from (Zn0.47Fe0.34 Mn0.14) Ti1.01O3 to (Zn0.02 Fe0.78 Mn0.15) Ti1.01O3 and is classified as ferroan manganoan ecandrewsite to zincian manganoan ilmenite. EPMA study reveals that the host rock consists of albite as major mineral constituent with some K-feldspar and chlorite as minor mineral constituents. The accessory minerals are sphene and ilmenite. On the basis of whole rock data, the albitite is classified as granite to syenite. The compositional variability within individual grains of ecandrewsite and other zinc bearing ilmenite suggests a replacement origin of the earlier formed magmatic mineral ilmenite. Core to rim enrichment of Zn content within ecandrewsite suggest that migration of Zn along the grain boundaries of ilmenite occurred through mantle derived alkaline fluids from outside the system along the deep seated fracture zones and micro-shears; thus, precipitating many other metals (Cu, Au, U, REE) along with Zn. This association of ecandrewsite within albitite may be used as an indicator mineral for search of copper, gold, uranium and REE in cratonic parts of India and elsewhere in a similar geological set up.