Rare earth element mobility in and around carbonatites controlled by sodium, potassium, and silica.
Rare earth element mobility in and around carbonatites controlled by sodium, potassium, and silica.
复制标题
碳酸岩及其周围的稀土元素活动性受钠、钾和硅的控制。
DOI：
10.1126/sciadv.abb6570
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发表时间：
2020-10
期刊：
影响因子：
13.6
通讯作者：
Wall F
中科院分区：
文献类型：
--
作者：
Anenburg M;Mavrogenes JA;Frigo C;Wall F
稀土在碳酸盐成因的热液中通过与碱的络合而浓缩。碳酸盐岩和伴生岩石是稀土元素(REE)的主要来源，稀土元素是现代技术所必需的金属。稀土矿化赋存于碳酸盐岩内部或附近的热液组合中，表明稀土元素在水中迁移。我们用轻(La)和重(Dy)稀土进行了从1200°C和1.5 GPa到200°C和0.2 Gpa的实验，结晶了与方解石互生的氟磷灰石，从白云石到铁角闪石。所有实验都含有阴离子的溶液，以前人们认为它们能激活稀土元素(氯化物、氟化物和碳酸盐)，但只有在有碱的情况下，稀土元素才能广泛溶解。在碱性络合条件下，镝比镧更易溶解。SiO_2的加入或捕获早期结晶磷灰石中的稀土元素，或通过固定硅酸盐中的碱而使溶解度增加。卤素和碳酸盐等阴离子物种不足以促进稀土元素的迁移。作为经济品位矿化的先驱，碳酸盐岩内部和周围的大量稀土元素需要与碱进一步络合才能大量运输。
Rare earths concentrate by complexing with alkalis in carbonatite-derived hydrothermal fluids. Carbonatites and associated rocks are the main source of rare earth elements (REEs), metals essential to modern technologies. REE mineralization occurs in hydrothermal assemblages within or near carbonatites, suggesting aqueous transport of REE. We conducted experiments from 1200°C and 1.5 GPa to 200°C and 0.2 GPa using light (La) and heavy (Dy) REE, crystallizing fluorapatite intergrown with calcite through dolomite to ankerite. All experiments contained solutions with anions previously thought to mobilize REE (chloride, fluoride, and carbonate), but REEs were extensively soluble only when alkalis were present. Dysprosium was more soluble than lanthanum when alkali complexed. Addition of silica either traps REE in early crystallizing apatite or negates solubility increases by immobilizing alkalis in silicates. Anionic species such as halogens and carbonates are not sufficient for REE mobility. Additional complexing with alkalis is required for substantial REE transport in and around carbonatites as a precursor for economic grade-mineralization.
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