REE–HFSE–rich, Titanite-bearing Syenite - Pyroxenite Intrusive Suite from the Chilka Lake Domain of the Northeastern Eastern Ghats Belt

Abstract

A suite of REE - HFSE - rich syenite and associated clinopyroxenite hosted in charnockitic orthogneisses of the northeastern part of the Eastern Ghats province, south of the Mahanadi shear zone has been recorded for the first time. The mode of emplacement, petrography, mineralogy, chemistry and economic significance in terms of the REE and HFS elements of this magmatic suite of intrusive rocks are presented and discussed.

The coarse grained syenite, composed mainly of Ba-bearing (with up to 8 wt% BaO) K-feldspar (hyalophane), and accessory greenish clinopyroxene is the main rock type of this magmatic unit. Associated segregations of clinopyroxene cumulates has formed a greenish grey coarse-grained pyroxenite. Sporadic concentration of sphene (titanite) in irregular patches in the syenite is also observed which displays high radioactivity. Sphene along with allanite, thorite, monazite and other REE bearing phases are characterized by high abundance of total-REE and HFSE. The syenite and pyroxenite do not exhibit features of discernible postemplacement deformation and metamorphism and may represent a late-tectonic event of ferroan-felsic magmatism in the Chilka lake domain of the northeastern Eastern Ghats belt.