New Ar–Ar ages of southern Indian kimberlites and a lamproite and their geochemical evolution

Abstract

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Petrology of Lamproites from the Nuapada Lamproite Field, Bastar Craton, India

“…The concordance of the plateau and isochron ages and an atmospheric isotopic composition for the trapped (Gregory et al 2006). Two other ages of 1,044 ± 22 and 1,067 ± 31 Ma have been reported for the Majhgawan lamproite using Rb-Sr systematics (Smith 1992;Kumar et al 1993, respectively) Osborne et al 2011). However, Phillips (2012) commented that the age of *1500 Ma reported by Osborne et al (2011) was an overestimate and that the studied lamproite was emplaced at \1,400 Ma.…”

“…Two other ages of 1,044 ± 22 and 1,067 ± 31 Ma have been reported for the Majhgawan lamproite using Rb-Sr systematics (Smith 1992;Kumar et al 1993, respectively) Osborne et al 2011). However, Phillips (2012) commented that the age of *1500 Ma reported by Osborne et al (2011) was an overestimate and that the studied lamproite was emplaced at \1,400 Ma. Hence, the likely age range of the Krishna lamproites is 1,100-1,400 My, the lower limit of which is still *50 My older than the Nuapada and Majhgawan lamproites.…”

Subduction-related origin of eclogite xenoliths from the Wajrakarur kimberlite field, Eastern Dharwar craton, Southern India: Constraints from petrology and geochemistry

“…Radiometric ages determined using Ar/Ar and U-Pb isotope systems on mineral separates (phlogopite and perovskite) demonstrate that kimberlite emplacement in all fields in the Eastern Dharwar craton took place during the Mesoproterozoic, at ca. 1.1 Ga (Gopalan and Kumar, 2008;Osborne et al, 2011;Chalapathi Rao et al, 2013). Therefore studies of kimberlites and their xenoliths EDC offer excellent opportunities to obtain insight into Proterozoic lithosphere composition bearing on the formation of Gondwana and the breakup of the Rodinia supercontinent.…”

Petrogenesis of Mesoproterozoic lamproite dykes from the Garledinne (Banganapalle) cluster, south-western Cuddapah Basin, southern India

“…Available radiometric ages of the Cuddapah Basin and EDC lamproites show them to be of Mesoproterozoic age with a great majority emplaced between 1.25 and 1.45 Ga (Chalapathi Rao et al 1999;Kumar et al 2001;Osborne et al 2011). These ages are strikingly similar to: (i) the emplacement age (1326±73 Ma) of the Racherla alkali syenite within the Cuddapah Basin (Fig.…”

“…As a result, most of the current lamproite petrogenetic models are strongly influenced by studies on Phanerozoic lamproites (e.g., Leucite Hills, Smoky Butte, West Kimberley, Gaussberg, and the Mediterranean region; Murphy et al 2002;Carlier and Lorand 2003;Coban and Flower 2006;Mirnejad and Bell 2006;Davies et al 2006;Prelević et al 2012). A significant number of Mesoproterozoic lamproites occur in the Eastern Dharwar, the Bastar and the Bundelkhand cratons of the Indian shield (Chalapathi Rao et al 1996Rao et al , 1999Kumar et al 2001;Osborne et al 2011;Sahu et al 2013) and they provide a unique opportunity to understand the tectonomagmatic processes when these cratons constituted a part of Proterozoic supercontinents such as Columbia and Rodinia. Furthermore, the spatial association of Mesoproterozoic lamproites, some of which are diamondiferous, with two of the major Proterozoic Purāna sedimentary basins of peninsular India -the Vindhyan (Chalapathi Rao 2005 and references therein; Masun et al 2009) in central India and the Cuddapah (Bergman 1987;Chalapathi Rao 2007) in southern Indiaremains one of the puzzling aspects of Indian geology.…”