A geochemical Nd Sr and stable Ca isotopic study of siliciclastic and chemical sedimentary rocks volcanic tuffs and authigenic glauconites from Proterozoic sedimentary basins of India

Abstract

The Archean-Proterozoic transition is marked by globally synchronous changes in tectonothermal and climatic patterns along with development of widespread epicontinental seas, with extensive shelf-sedimentation. The Indian Shield hosts several Proterozoic sedimentary basins, popularly known as the Purana basins, with mostly undeformed and unmetamorphosed siliciclastic and carbonate sediments. The undeformed and unmetamorphosed nature of these sediments, along with their prolonged sedimentation, makes them excellent geological archives of past tectono-thermal and climatic events as well as paleo-depositional environments, and makes them suitable for geochemical and isotopic studies. In this study, sedimentary rocks were collected from the Paleo-Mesoproterozoic Cuddapah Basin and the Mesoproterozoic Chhattisgarh Basin from the Southern Indian Block (SIB), the Paleo-Mesoproterozoic Vindhyan Basin from the Northern Indian Block (NIB), and the Neoproterozoic Marwar Basin from the Western Indian Block (WIB) or the Marwar Block (MB). A geochemical and Nd isotope study of the siliciclastic sediments from the Cuddapah, Vindhyan, and Chhattisgarh basins show that during periods of tectonic stability in the Indian Craton, these basins derived detritus from evolved sources with unradiogenic Nd isotopic compositions. Periods of juvenile magmatism can be well-traced in the associated sediments across the basins. The volcanic tuffs from Cuddapah (1.86 Ga), Singhora (1.5 Ga), and Chhattisgarh basins (1.0 Ga) show similar geochemical compositions suggesting their derivation from ancient arcs. The Nd isotope evolution of these tuffs, with widely-varying eruption ages, suggest their derivation from a common mantle source. Chemically precipitated Precambrian sediments have been variably used to infer the redox condition of early Earth, to trace the fluxes of crustal and mantle derived cations and anions to the oceans, and to understand the paleo-habitat of ancient lifeforms...