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

Abstract

Giant quartz veins (GQVs; earlier referred to as 'quartz reefs') occurring in the Archean Bundelkhand Craton (29, 000 km 2 ) represent a gigantic Precambrian (∼ 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.

Thermo-mechanical properties of Bundelkhand granite near Jhansi, India

“…It consists of supracrustal gneisses with or without TTG affinity, metapelites, amphibolites, iron rich and less abundantly, manganese-rich metasedimentary rocks, marble, calc-silicate rocks and quartzites. Several phases of compositionally different felsic intrusive rocks, felsic volcanic rocks, giant quartz veins (GQVs) (Pati et al 2007), and mafic-ultramafic intrusive rocks (Basu 1986;Mondal et al 2002;Malviya et al 2006) are also present. The GQVs are up to 70 m wide and can exceed 100 km in strike length, and are the most conspicuous regional structures observed as curvilinear features throughout the Bundelkhand craton.…”

“…These veins were later intruded by NW trending mafic dikes. The supracrustal gneisses show three phases of folding and the imprint of a crustal-scale brittle ductile shearing (*E-W trending) episode that affected all major lithology except the mafic dikes (Pati et al 2007;Malviya et al 2006). The Bundelkhand rocks, in general, are metamorphosed to amphibolite facies (Basu 1986) and, in places, possibly to granulite facies.…”

The Dhala structure, Bundelkhand craton, Central India—Eroded remnant of a large Paleoproterozoic impact structure

“…1b); it consists of supracrustal gneisses with or without tonalite-trondhjemitegranodiorite (TTG) affinity, metapelites, amphibolites, ironrich and, less abundantly, manganese-rich metasedimentary rocks, marble, calc-silicate rocks and quartzites. Several phases of compositionally different felsic intrusive rocks, felsic volcanic rocks, giant quartz veins (GQVs) (Pati et al 2007), and mafic-ultramafic intrusive rocks (Basu 1986;Mondal et al 2002;Malviya et al 2006) are also present. The giant quartz veins are up to 70 m wide and can exceed 100 km in strike length, and are the most conspicuous regional Fig.…”

“…b) A simplified geological map of the Bundelkhand craton shows the location of the Dhala structure (encircled) and the regional geology. Adapted from Pati et al (2007) The rectangle around the symbol for Dhala village indicates the area of the geological map shown in Fig. 3.…”

“…These veins were later intruded by NWtrending mafic dikes. The supracrustal gneisses show three phases of folding and the imprint of a crustal-scale brittleductile shearing (∼E-W trending) episode that affected all major lithologies except the mafic dikes (Malviya et al 2006;Pati et al 2007). The Bundelkhand rocks, in general, are metamorphosed to amphibolite facies (Basu 1986) and, in places, possibly to granulite facies (J. K. Pati, unpublished data).…”