Silica phase transformations drive Si-O isotopic offsets in ancient chert: Implications for paleo-ocean temperature and silicon cycle reconstructions

The datasets include major and minor elements, and TOC contents (wt.%; Supplementary Data Table S1), trace element and REEs concentrations (mg/kg; Supplementary Data Table S2). Various chert types from representative sedimentary profiles of the Paleozoic, Proterozoic and Archean, invoking volcanic, S-, C- (seawater, hydrothermal), dike chert types and their Si and O isotopic and trace elements datasets (Supplementary Data Table S3), and Si and O in-situ isotope datasets for representative microquartz and quartz veins of the 1.88 Ga Gunflint (Canada), 2.72 Ga Tumbiana Formation (Australia), 3.29 Ga Mendon Formation (South Africa), and 3.48 Ga Dresser Formation (Australia) chert (Supplementary Data Table S4). Also included are Si isotope fractionation in opal-CT dissolves and reprecipitates to microquartz process in porewater (Supplementary Data Table S5), and models for various styles of paleotemperature reconstruction from O isotope of chert (Supplementary Data Table S6) are shown for the early Silurian C-chert (seawater chert) sample from the Yangtze block, South China, the Proterozoic-Cambrian transition C-chert from the Bohemian Massif, Czech Republic, and 1.9 Ga Gunflint chert, Canada.