Pyroclastic Rocks of Dharwar Craton: A Possible Source for Rare Metals and Rare Earth Elements?

ABSTRACT Pyroclastic rocks constitute an important, yet comparatively understudied product of volcanism, which yield valuable insights into magma fragmentation, volatile behaviour and magma-water interaction during explosive eruptions. Owing to their glass-rich nature, high permeability and large surface area, pyroclastic rocks provide favourable sites for fluid-rock interaction and may locally concentrate incompatible elements, including Rare Earth Elements (REE) and Rare Metals (RM). The Dharwar Craton preserves multiple phases of Neoarchean volcanism ranging from ultramafic to felsic compositions within the greenstone belts. The western Dharwar Craton represents relatively older volcanic activity (~3.3 Ga), whereas the eastern sector (~2.7 Ga) records island-arc-related volcanism characterised by diverse mafic and felsic volcanic rocks with abundant gold mineralisation. Despite their spatial association with mineralised units, the pyroclastic rocks of EDC representing effusive to explosive volcanic activity received limited attention with respect to their REE and RM potential. Preliminary studies on the pyroclastic units from the Ulindakonda area of the Gadwal belt and Veligallu belt indicate the occurrence of sulphide and accessory minerals including pyrite, chalcopyrite, magnetite, allanite, zircon, monazite, bastnäsite and titanite, indicating their mineralised nature. Keeping in view the extensive hydrothermal alteration along with prolonged weathering conditions, these pyroclastic lithologies may be favourable hosts for REE and RM enrichment, warranting detailed geochemical and mineral chemical studies.