钪在岩浆、热液及风化过程中富集成矿机制研究—以湘南益将特大型独立钪矿为例

The demand for Scandium resource has accumulated over last 30 years with the development of High-Tech industry. However, Because of the lack of independent giant scandium deposit, the limited supply of scandium resource mainly recovered from other mineral processing operations as a byproduct has resulted in high market prices. Therefore, independent giant scandium deposit will be the main target for mineral exploration, which requires us to better understand the genesis of various scandium deposits. Unfortunately, litter is known about the genesis of scandium deposits due to the lack of the thermodynamic data for the scandium transported in hydrothermal fluid at elevated temperature and pressure. Based on the previous studies, this proposal will take the Yijiang independent giant scandium deposit, southern Huna as an example, and systematically conduct the studies of petrology, mineralogy and in situ analysis, elemental and fluid geochemistry on the ore-bearing igneous rocks, and different type of alterated rocks and ores. Combined with the high temperature and pressure simulated experiments, we will directly measure and calculate the solubility, species and corresponding formation constant of scandium transported in hydrothermal fluid; then we will further study the species of scandium transported in magmatic-hydrothermal processes, enrichment and the mechanism of its precipitation to mineralization. The study of this project will not only enhance the understanding of the genesis of the Yijiang scandium deposit, but also present important thermodynamic data to promote the studies on the genesis of various hydrothermal scandium deposits, and then further enrich the metallogenic theory of scandium deposit.

在过去30年内，随着高科技产业的不断发展，对钪矿资源的需求越来越大，但由于独立大型钪矿床很少，钪矿资源主要从其他矿床中以副产品的形式回收，其供给并不稳定，导致钪矿的价格不断攀升。目前，寻找特大型独立钪矿已成为矿业勘探的重要目标，这需对各类钪矿的成因有较深入的理解。然而，由于缺乏钪在热液流体中迁移的热动力学数据，目前对钪矿成因的研究仍较为薄弱。本项目在已有研究的基础上，选择湘南益将特大型独立钪矿为解剖对象，通过对成矿岩体、各蚀变岩及不同类型矿体系统开展岩石学、矿物学及矿物微区分析、元素及流体地球化学的研究，同时结合高温高压模拟实验，在系统测定及计算钪在热液流体中溶解度、络合物结构及其稳定常数，明确钪在益将矿床岩浆、热液及表生风化作用中的迁移、富集过程及沉淀成矿机理。该项目的开展，不仅可以深化益将钪矿成因的研究，而且为推动国际上各类热液钪矿成因研究提供了重要的热力学参数，进而丰富钪成矿理论。

离子吸附型稀土矿床供应全球80%的重稀土资源，目前针对类型矿床的成矿机制尚不清楚，南岭地区是全球著名的离子吸附型稀土矿床资源基地，是研究此类矿床成因的理想场所。本次研究以益将高铕-富钪轻稀土矿床为例，通过岩相学、矿物学、年代学和地球化学研究，确定了与离子稀土矿床相关的岩浆源区特征，查明了益将岩体中钪-铕-轻稀土元素的赋存状态，结合高温高压模拟实验，确定了钪金属在不同热液流体中的迁移形式和溶解度，并系统对比南岭地区离子吸附型稀土矿床成矿岩体的地球化学特征，揭示了成矿岩体中控制稀土元素分异的制约机制。取得了一下认识：1、益将岩体主要形成于下地壳物质的部分熔融，有少量幔源物质的混入，该岩体还原的性质和低的分异程度，形成高钪、铁、镁含量的岩浆，利于形成富集钪元素的角闪石、辉石矿物。2、益将岩体中钪元素富集于富锆和铁镁质的矿物，如角闪石；铕元素富集于富钙的矿物，如斜长石；轻稀土元素富集于副矿物，如磷灰石。3、钪金属在含氟酸性成矿热液流体中以Sc-F络合形式迁移；在含氯离子热液流体中以Sc3+、Sc(OH)2+和Sc(OH)30的络合物形式迁移；在硫酸根热液流体中主要以Sc(SO4)+和Sc(SO4)2-的形式迁移。4、明确了重稀土型成矿岩体形成于高成熟度壳源物质的部分熔融，具有高度分异演化程度；轻稀土型成矿岩体形成于壳幔物质的混合，易形成准铝质-过铝质、富硅、钙碱性-碱性、富磷的岩浆，具有中等的分异演化程度； 轻稀土-铕型成矿岩体主要形成于低成熟度壳源物质的部分熔融，可能有少量幔源物质的混入，低的分异演化程度。