我国科学家破解稀土成矿难题

Core Viewpoint - The depth of carbonatite magma intrusion (pressure) is a key factor controlling the extraordinary accumulation of rare earth elements (REEs) [1][2]. Group 1: Research Findings - The research team conducted high-temperature and high-pressure experiments simulating the cooling and crystallization process of carbonatite magma at depths of approximately 6-20 kilometers [1]. - At depths shallower than 10 kilometers (approximately 0.3 GPa), apatite crystallizes early, trapping REEs within its structure, which prevents further migration and accumulation of these elements [1][2]. - In contrast, at depths greater than 0.3 GPa, olivine crystallizes first, consuming silicon and preventing apatite from forming a "cage" to lock in REEs, allowing for higher solubility of REEs in saline melts [2]. Group 2: Implications for Rare Earth Deposits - This discovery explains the distribution patterns of global carbonatite-type rare earth deposits, with world-class deposits like Baiyun Obo in China having intrusion depths greater than 10 kilometers [5]. - Shallow carbonatite bodies, such as those in Sweden and Tanzania, may contain REEs but are often dispersed and lack economic viability for mining [5]. - The research establishes a complete causal chain of "pressure-mineral crystallization sequence-melt properties-REE enrichment," enhancing the understanding of REE accumulation mechanisms and providing new insights for exploration of carbonatite-type rare earth deposits [5].