SCREED: Supergene enrichment of carbonatite REE deposits

SCREED：碳酸岩稀土矿床的表生富集

• 批准号: NE/X015114/1
• 负责人: Martin Smith
• 金额: $ 103.6万
• 依托单位: University of Brighton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX015114%2F1
• 关键词: SCREED; Supergene; enrichment; carbonatite; REE

The rare earth elements (REE), and in particular neodymium and dysprosium, are essential for renewable energy devices such as wind turbines and the development of electric motors for transport. At present the REE are sourced from either low concentration weathered granitoid (ion adsorption clay) deposits, or from high concentration carbonatite-related deposits, especially the World's dominant REE mine in hard-rock, altered carbonatite at Bayan Obo, China. The one major mine operator outside of China is the Mount Weld weathered carbonatite, Australia. Weathered carbonatites such as Mount Weld are some of the world's richest REE deposits and several are subject to active exploration. As part of the NERC Global Partnerships Seedcorn fund project WREED, we have carried out preliminary investigations of weathering products on carbonatite hosted REE deposits. Three end member weathering products have been identified (1) carbonate mineral dissolution leaves behind primary REE minerals, forming residual deposits; (2) dissolution and reprecipitation of REE phosphates and fluorcarbonate minerals results in the formation of new hydrated REE-phosphate or -carbonate minerals producing supergene enrichment; and (3) the formation of clay and iron-manganese oxide caps (either from weathering of the deposit itself, or from soil transport from surrounding rocks) that may hold the REE adsorbed to mineral surfaces (c.f. the ion adsorption deposits). High grade, weathered carbonatite deposits typically consist of a range of soil and weathered horizons, that may be phosphate-rich due to dissolution and re-precipitation of apatite and monazite during the weathering process (Mount Weld, Australia), overlain by later sediments that may be REE enriched either by accumulation of residual minerals in lake sediments (Tomtor, Russia). The mineralogy of the ore zone is linked to, but distinct from, the unweathered carbonatite rock, and includes phosphates, crandallite-group minerals, carbonates and fluorcarbonates and oxides. In this study we will utilise bulk rock geochemistry, sequential leaching techniques, mineral chemistry and microbiology to investigate the processes producing different weathered REE deposit styles in carbonatites and their influence on the economic REE grade and environmental impact of deposits. Bulk rock geochemistry will be used to quantify element enrichments and depletions relative to bedrock, and to investigate the potential for ion adsorption style mineralisation in weathered carbonatites. Mineral chemical techniques will be used to investigate the timing of weathering, host minerals of the REE, potential beneficial or harmful changes in chemistry relative to primary minerals, and proxies for the environmental controls on weathering style. These data will be combined with existing records of surface morphology and weathering depth to produce overall genetic models linking climate, geomorphology and geochemistry that will allow prediction of the resource potential of the carbonatite weathered zone. The results will be communicated with industry and the public to raise awareness of the resource requirements of decarbonisation, and potential routes to increased extraction efficiency and reduced impact.

稀土元素（REE），尤其是新近hode虫和dosprosium，对于可再生能源设备（例如风力涡轮机）和电动机的发展是必不可少的。目前，REE来自低浓度风化的花岗岩（离子吸附粘土）沉积物，或来自与碳酸盐岩相关的高浓度，尤其是中国巴曼OBO的碳酸盐岩改变了世界上占主导地位的REE矿山。中国以外的一个主要矿山经营者是澳大利亚焊山风化的碳酸盐岩。风化的碳酸盐（例如焊缝）是世界上最丰富的REE沉积物，有几个经受积极的探索。作为NERC全球合作伙伴种子康科基金项目的一部分，我们已经对碳酸盐岩托管REE存款的风化产品进行了初步调查。已经鉴定出三个最终成员风化产品（1）碳酸盐矿物质溶解叶子后面的主要REE矿物质，形成残余沉积物； （2）REE磷酸盐和氟碳酸盐矿物质的溶解和重新沉淀导致形成新的水合磷酸盐或碳酸盐矿物质，产生超元富集； （3）形成粘土和铁山烷氧化物盖（来自沉积物本身的风化，或来自周围岩石的土壤传输），可能使REE吸附到矿物质表面（C.F.离子吸附沉积物）。高级风化的碳酸盐沉积物通常由一系列土壤和风化的水平构成，在风化过程（澳大利亚山脉WELD，WELD，WELD）期间，由于对磷酸盐和磷灰石的溶解和重新沉积可能会富含磷酸盐的水平，这些沉积物被后来的沉积物覆盖，后来的沉积物可以因湖泊沉积物中的残留物（Tometia in tomtia）（Tomtia）的累积而丰富，tomteria（Tomecia）（Tomtia）（tomeria russia russia）。矿石区的矿物学与不受欢迎的碳岩岩相关，但与未经许可的碳酸盐岩相关，其中包括磷酸盐，脑臂组矿物质，碳酸盐，碳酸盐，碳酸盐和氧化物和氧化物。在这项研究中，我们将利用散装岩石地球化学，顺序浸出技术，矿物质化学和微生物学来研究产生碳酸盐岩中不同风化的REE沉积样式的过程，以及它们对沉积物的经济REE等级和环境影响的影响。散装岩石地球化学将用于量化相对于基岩的元素富集和耗竭，并研究风化碳酸盐岩中离子吸附样式矿化的潜力。矿物化学技术将用于研究风化的时机，REE的宿主矿物，相对于原发性矿物的潜在有益或有害变化，以及对风化风格的环境控制的代理。这些数据将与现有的表面形态和风化深度的记录相结合，以产生与气候，地貌和地球化学联系的总体遗传模型，从而可以预测碳酸盐风化区的资源潜力。结果将与行业和公众传达，以提高人们对脱碳资源要求的认识，以及提高提取效率和降低影响的潜在途径。