Geochemistry of clastic sediments from Sargur supracrustals and Bababudan group, Karnataka: Implications on Archaean Proterozoic Boundary

Abstract

The sediments from three stratigraphic levels in the Bababudan schist belt of Dharwar craton exhibit great diversity in major, trace and rare earth element (REE) geochemistry and thus interpreted to represent significant compositional variation in the source rocks. Detailed geological and geochemical studies have been carried out on clastic rocks constituting the Archaean Sargur supracrustals and the Bababudan belt of Dharwar craton (DC), southern India for understanding the geochemical characteristics and to define the Archaean-Proterozoic Boundary (APB/QPC) in southern India. There is significant contrast in the geochemical signatures for the sediments from these stratigraphic levles. The Sargur enclave population is characterised by slight LREE enrichment with (La/Sm) N ranging from 1.45 to 3.58, almost flat HREE with (Gd/Yb) N ranging from 0.65 to 1.29 with Eu/Eu* ranging from 0.49 to 0.91 suggesting mafic-ultramafic source rocks in the provenance. On the other hand, the Post QPC (PQPC) rocks are characterised by LREE enrichment with (La/Sm) N ranging from 2.66 to 7.07, nearly flat HREE with (Gd/Yb) N ranging from 0.58 to 0.95 and significant depletion of Eu with Eu/Eu* ranging from 0.34 to 0.85, indicating felsic province in the source area. The conglomerates and quartzites representing the QPC are showing mixed nature of these, reflecting the transitional character in depositional environment. Increase in abundance of REE, K 2 O/Na 2 O, Th/Sc, La/Sc, Th/U, Hf/Ta and Zr/Y ratios are characteristic of the QPC. The PQPC sediments are enriched in Th, U and HFSE like Hf, Nb, Zr and Y, and depleted in Co and Eu than their older counterparts. These geochemical signatures signify the dominance of mafic-ultramafic rocks in the source area for Sargur rocks and the existence of granite-granodiorite for PQPC clastics. Thus, the unconformity related oligomictic quartz pebble conglomerates (QPC) and quartzites at the base of Bababudan Group resembling the QPC of Witswaterand, South Africa signifies that a stable continental crust had already developed in southern India prior to ~3.0Ga.

Provenance and tectonic settings of sands from Puerto Peñasco, Desemboque and Bahia Kino beaches, Gulf of California, Sonora, México

“…Roser and Korsch (1988) used a discriminant function analysis of major elements (TiO 2 , Al 2 O 3 , total Fe 2 O 3 , MgO, CaO, Na 2 O and K 2 O) -Altrin et al, 2004;Drobe et al, 2009;Gabo et al, 2009;Bhushan and Sahoo, 2010;de Araújo et al, 2010;Maslov et al, 2010;Wani and Mondal, 2010;Purevjav and Roser, 2012). The major-element based discriminant function diagram of Roser and Korsch (1988) shows felsic source for PP, DE and BK sands (Fig.…”

A review of the inferred geodynamic evolution of the Dharwar craton over the ca. 3.5–2.5 Ga period, and possible implications for global tectonics

“…(1) Deposition of a basal quartz pebble conglomerate (QPC; Kartikere conglomerate) was succeeded by quartzite-basalt alternations and minor gabbroic sills, BIF, and phyllites, together making up "succession 1" (Swami Nath and Ramakrishnan 1981; Arora et al 1994;Arora and Naqvi 1993;Bhusan and Sahoo 2010). The latter is interpreted as braided fluvial deposits and subaerial lavas, and according to Hokada et al's (2013) age data, deposition occurred at <3.14 Ga; these rocks most likely were deposited between ca.…”

A Combined Petrological-Geochemical Study of the Paleozoic Successions of Iraq

“…Bhatia (1983) and Roser and Korsch (1986) proposed tectonic setting discrimination fields for sedimentary rocks to identify the tectonic setting of unknown basins. These tectonic setting discrimination diagrams are still extensively used by many researchers to infer the tectonic setting of ancient basins (Drobe et al, 2009;Gabo et al, 2009;Maslov et al, 2010;Wani andMondal, 2010 Bakkiaraji et al, 2010;Bhushan and Sahoo, 2010;de Araújo et al, 2010). However, the functioning of major elements tectonic setting discrimination diagrams proposed by Bhatia (1983) and Roser and Korsch (1986) have been evaluated in many studies.…”