Systematic boron isotope analysis on a Quaternary deep SG-1 core from the Qaidam Basin, NE Tibetan Plateau and its paleoclimate implication

Abstract

Boron (B) isotope has been widely used in marine sediments to reconstruct paleoclimate evolution history. However, due to the relatively complex continental deposition environment, complicated fractionation process and controls of multi-processes on the δ11B variations of terrestrial sediments, the application of B isotope in terrestrial sediments and its indicative significance are limited and controversial. Here we conducted systematic B isotope and chemical composition studies on extracted evaporite, carbonate and silicate phases of sediments from a well-studied Quaternary deep drilling core (SG-1) from the Qaidam Basin, NE Tibetan Plateau, to explore the respective geochemical behavior of the B isotope in different phases of sediments and their respective implications. The results indicate that B in the evaporite phase of the SG-1 sediments is primarily derived from ion co-precipitated minerals instead of fluid inclusions. The δ11B variations in the carbonate and silicate phases possess different implications. The δ11Bcarbonate could serve as a potential paleo-salinity indicator, and the δ11Bsilicate could be a possible indicator to reflect the chemical weathering history of the catchment. Our systematic B isotope analysis explores the influences of different processes on the B isotope components of terrestrial sediments and decomposes the respective implication of B isotope in different phases of sediments. It can therefore provide important reference significance for future B isotope in terrestrial sediments and its application in paleoclimate study.