Rare Earth Element Geochemistry of Late Cenozoic Island Carbonates in the South China Sea

Marine carbonates, precipitating from seawater through inorganic geochemical and biogeochemical processes, are considered to have recorded the signatures reflecting marine environmental conditions during their formation. However, they susceptible post-depositional diagenetic alteration. The redox chemical composition of fluid may be different those overlying seawater. Therefore, assessing whether carbonate rocks that experienced variable diagenesis could still preserve primary geochemistry is a prerequisite before inferring ancient environments using tracers such as cerium anomaly (Ce/Ce*). Here, we investigate rare earth elements plus yttrium (REY) features reefal carbonates XK-1 core in Xisha Islands South China Sea. We aim evaluate island potential reliable REY characteristics after experiencing meteoric diagenesis, burial or dolomitization. results show even alteration, all samples exhibit seawater-like patterns, which characterized by negative Ce anomalies (Ce/Ce* < 1), distinctively high Y/Ho ratios (>44), uniform depletion light (LREE) relative heavy (HREE) ((Pr/Yb)N 1). This suggests original retained, regardless varying degrees changes mineralogical composition, state. unmodifiable can attributed three aspects: (1) low content fluids short-term reactions between make it difficult significantly alter carbonates; (2) ubiquitous cementation creates relatively closed environment facilitates inheritance (3) dolomitization, dolomitizing derived penecontemporaneous would not destroy but rather promote preservation dolostones. Ce/Ce* variations indicate been deposited under constantly oxic since Neogene, consistent with paleontological redox-sensitive element evidence.