The Zr-Ti mineralization in carbonatites of the Samchampi alkaline carbonatite complex, Assam, India

Viladkar S.G.*, Sorokhtina N.V.**, Senin V.G.**

* Carbonatite Research Centre, Amba Dongar Kadipani, India; ** Vernadsky Institute of geochemistry and analytical chemistry, Moscow, Russia

The Zr-Ti minerals are widespread in carbonatites of a many alkaline provinces - Kola Peninsula, Polar Siberia, Ukrainian, Canada, Brazil et al. We have found calzirtite and zirconolite in calcite carbonatites of the Samchampi alkaline complex (India). The Samchampi-carbonatite alkaline igneous intrusion is a roughly circular and stock-like body cropping out in Archaean of the Mikir Hills massif of Assam (eastern India). The Samchampi complex is composed of syenitic fenite, magnetite-perovskite-apatite rock, phoshatic rock, ijolite-melteigite, carbonatites of varied dimensions, chert breccia, nepheline syenite, alkali pyroxenite, phonoliteand volcanic tuff [1].

Carbonatites the first generation are presented with olivine-phlogopite sovite and sovite with pyrochlore. The second generation’s carbonatites are olivine-biotite sovite, beforsite and silicocarbonatites and they are changed metasomatically often. Carbonatites forms discontinuous dykes and veins intruding silicate rocks of massif.

Fig.1 (a) backscattered electron images of euhedral zirconolite showing chemical zoning and (b) replacement of calzirtite (Cz) with zirconolite (Zr) and baddeleyite (Bd) from the Samchampi complex.

Table 1 Microprobe analyses of zirconolite, calzirtite and baddeleyite (wt.%)