Molybdenum isotopes demonstrate that multistage upgrading is required to generate heavy rare earth element–enriched carbonatites

作者：Xiaochen Zhao, Shuang Yan, He‐Cai Niu, Wu‐Bin Yang, Ningbo Li, Jie Li, Le Zhang, Alex J. McCoy‐West · 发表于：Geological Society of America Bulletin · 年份：2024 · DOI：10.1130/b37700.1 · 被引用次数：4 · 研究领域：Geochemistry and Elemental Analysis、Paleontology and Stratigraphy of Fossils、Radioactive element chemistry and processing

Abstract Carbonatites with heavy rare earth element (HREE) enrichment are a rare and intriguing prospect for economic geology research, due to the growing global demand for HREEs in various industries. However, debate persists over the mechanism responsible for HREE enrichment in carbonatites, with the mantle source, magmatic-hydrothermal evolution, or a combination of these factors proposed to be responsible. This study examines three adjacent Late Triassic carbonatites (from the Huanglongpu, Huayangchuan, and Jialu carbonatite dike systems) in the Lesser Qinling of Central China and uses Mo isotope systematics to provide unique insights into the HREE enrichment process of these magmas. All three carbonatites exhibit elevated total REE (ΣREE) concentrations (up to 4600 ppm), along with significant HREE enrichment (ΣHREE/ΣREE = 0.1–0.4). Notably, Jialu carbonatite stands out for having the highest total HREE concentrations (≥360 ppm) and ΣHREE/ΣREE ratios (0.2–0.4). Regardless of their variable degrees of HREE enrichment, the three carbonatites display similar Sr-Nd-Pb isotope signatures, which indicates a shared enriched mantle source. The Huanglongpu and Huayangchuan carbonatites mostly display significantly lighter δ98/95Mo (−1.71‰ to −0.15‰) values than the depleted mantle, which indicates an origin from an enriched mantle influenced by recycled pelagic clays and Fe-Mn nodules. Both types of marine sediments are enriched in REEs and would have undergone initial HREE enric...