Tourmaline occurs as a minor but important mineral in the alteration zone of the Archean orogenic gold
deposit of Guddadarangavanahalli (G.R.Halli) in the Chitradurga greenstone belt of the western Dharwar
craton, southern India. It occurs in the distal alteration halo of the G.R.Halli gold deposit as (a) clusters of
very fine grained aggregates which form a minor constituent in the matrix of the altered metabasalt
(AMB tourmaline) and (b) in quartz-carbonate veins (vein tourmaline). The vein tourmaline, based upon
the association of specific carbonate minerals, is further grouped as (i) albite-tourmaline-ankerite-quartz
veins (vein-1 tourmaline) and (ii) albite-tourmaline-calcite-quartz veins (vein-2 tourmaline). Both the
AMB tourmaline and the vein tourmalines (vein-1 and vein-2) belong to the alkali group and are classified
under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tourmalines
are unzoned. Mineral chemistry and discrimination diagrams reveal that cores and rims of the
vein tourmalines are distinctly different. Core composition of the vein tourmalines is similar to the
composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tourmalines
are proposed to be related to the regional D1 deformational event associated with the
emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-àvis
gold mineralization is spatially linked to the juvenile magmatic accretion (2.56e2.50 Ga) east of the
studied area in the western part of the eastern Dharwar craton.