Geochemistry of Palaeo-Proterozoic Kajrahat Limestone, Vindhyan Supergroup, Central India: insights into Depositional Conditions and Sources of Rare Earth Elements
Research Square (Research Square)(2023)
摘要
Abstract This study investigates the geochemical composition of major, trace and rare earth elements (REEs) in the Palaeo-Proterozoic Kajrahat Limestone, Vindhyan Supergroup, Central India to infer the depositional environment and source for the REEs. The studied limestones, have a high percentage of CaO (ranging from42.27–66.53, n = 17), followed by SiO 2 as the major oxides. Sr is dominant trace element showing a negative correlation with CaO. This indicates that either Sr precipitated its own minerals or it was contributed by the siliciclastic material. All trace elements exhibit depletion with respect to Post-Archean Australian Shale (PAAS) values. The PAAS-normalized REE pattern of studied limestone has a relatively uniform pattern, with slightly enriched LREE compared to HREE, negative Ce anomaly (ranging from 0.66–0.89), negative Eu anomaly (largely ranging from 0.84–1.43), and low U/TH ratio (ranging from 0.12–1.25).The studied limestones exhibit a negative correlation between ΣREE and Fe 2 O 3 , MnO, MgO, Sr but a positive correlation with other elements. These positive correlations suggest that, in addition to seawater, siliciclastic sediments also serve as a source for the REEs. The (La/Yb) N , La/Sc, La/Th, and Th/Sc ratios imply that the terrigenous admixture in studied limestone likely originated from felsic source rocks. The geochemical investigation of studied limestone indicates a low U content (0.3–1.3, n = 17) and U/Th (0.12–1.25, n = 17) ratios suggest an oxygen-rich environment. This, in turn, indicates that the deposition of this limestone occurred in a coastal/ shallow marine environment with some contribution from continental part.
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关键词
geochemistry,central india,palaeo-proterozoic
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