Lamprophyre Dykes in the South Delhi Fold Belt Near Pipela, District Sirohi, Rajasthan

Lamprophyre dykes are reported from the southern part of the South Delhi Fold Belt (SDFB), near Pipela, about 3 km SE of Sarupganj in Sirohi district of Rajasthan. They occur as sub-volcanic intrusives in the Ajabgarh supracrustals and follow a WNW -ESE to E-W trends. They show porphyritic and panidiomorphic textures with biotite and magnetite occurring as euhedrru phenocrysts ina cryptocrystalline matrix. One large Jamprophyre body shows acompositionallayering. Widespread alteration (chloritisation of biotite and potash depletion) suggests that they are not cogenetic with the post-Cretaceous, fresh lamprophyres of the Mundwara area. Probably these dykes are emplaced during the waning stage of the Late Proterozoic tectonomagmatic cycle of the South Delhi Fold Belt.