Geology and geochemistry of giant quartz veins from the Bundelkhand Craton, central India and their implications

Giant quartz veins (GQVs; earlier referred to as 'quartz reefs') occurring in the Archean Bundelkhand Craton (29, 000 km(2)) represent a gigantic Precambrian (similar to 2.15 Ga) silica-rich fluid activity in the central Indian shield. These veins form a striking curvilinear feature with positive relief having a preferred orientation NE-SW to NNE-SSW in the Bundelkhand Craton. Their outcrop widths vary from <= 1 to 70 m and pervasively extend over tens of kilometers along the strike over the entire craton. Numerous younger thin quartz veins with somewhat similar orientation cut across the giant quartz veins. They show imprints of strong brittle to ductile-brittle deformation, and in places are associated with base metal and gold incidences, and pyrophyllite-diaspore mineralization. The geochemistry of giant quartz veins were studied. Apart from presenting new data on the geology and geochemistry of these veins, an attempt has been made to resolve the long standing debate on their origin, in favour of an emplacement due to tectonically controlled polyphase hydrothermal fluid activity.