Characteristics of rare earth element abundances in shallow marine continental platform carbonates of Late Neoproterozoic successions from India.
Year: 2003
Type: article
Abstract: We have studied the REE distribution in shallow marine continental platform carbonates belonging to two late Neoproterozoic basins of India.Their REE abundance patterns normalized by chondrite display well defined W-type tetrad effect.Based on chondrite-normalized Gd/Ho, La/Nd ratios, the REE abundance patterns have been classified into three groups.(Y/Ho) and (Y/Dy) concentration ratios reflect a combined effect of Y fractionation relative to neighboring trivalent REEs during carbonate precipitation from seawater and influence of continental contributions with chondritic ratios.Negative Ce anomalies recorded in Krol and Bilara carbonates resembles the Ce anomaly reported from shallow marine waters.However, absence of Ce anomaly and distinct positive anomalies in some of our carbonate samples reflect post-depositional redox condition related to Ce mobilization and preferential enrichment during early diagenesis.Variations in the REE abundance patterns may be attributed to contamination with terrigenous particulates having shale like REE abundances and post-depositional early diagenetic processes.marine realm owing to differences in intrinsic quantum chemical properties (Racah parameters) of the REE complexes in the solution (Masuda and Ikeuchi, 1979;Masuda et al., 1987;Kawabe et al., 1998;Ohta and Kawabe, 2000).The tetrad effects are observed as concave curves consisting of La-Ce-Pr-Nd, Pm-Sm-Eu-Gd, Gd-Tb-Dy-Ho and Er-Tm-Yb-Lu in chondrite-normalized REE abundance patterns.Tetrad effect has been documented from marine chemical sediments like limestone/ dolomite (Kawabe et al., 1991;Kawabe et al., 1998;Tanaka et al., 2002) and chert (Minami et al., 1998).On the other hand Minami and Masuda (1997) and Minami et al. (1998) suggested quadratic equations for each tetrad curve which enable quantification of the degree of lanthanide tetrad effect.REEs in marine carbonate rocks have been
Source: GEOCHEMICAL JOURNAL
Institution: Nagoya University
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2055931639