摘要:
稀土元素和稀有金属被广泛应用于新兴产业及国防科技等领域,是国家重要的关键金属,稀有稀土元素找矿迫在眉睫。近日,我国在江西上饶灵山复式岩体周围的黄山花岗伟晶岩中发现新矿物铈钽易解石,并通过了国际新矿物委员会审核认证,该发现不仅丰富了易解石族矿物,同时也为稀有金属找矿提供了新的方向。铈钽易解石出现于黄山富钽伟晶岩中,与长石、石英、萤石等矿物共生,以针状或束状集合体的形式产出; 化学成分极度富钽、钛、铈,理想化学式为Ce(TiTa)O6,属于斜方晶系,晶体结构由铈氧多面体和钛/钽氧八面体构成。铈钽易解石形成于高演化的花岗伟晶岩,表明成矿环境极度富集钽; 与周围铌铁矿等矿物相比,铈钽易解石的钽含量突然增加,无法简单地用岩浆结晶分异的过程来解释; 伟晶岩组分分区提纯模型提出伟晶岩结晶过程存在“边界层”,该层具有富钠、氟、氯等挥发组分(也叫助熔剂)的特点,同时不相容组分不断积累导致丰度增加,熔体成分消耗殆尽后,边界层结晶造成矿物成分突变,不相容元素大量富集; 高分异花岗伟晶岩边界层以富集钠长石、萤石等富集挥发分的矿物为特征,是稀有金属找矿的重要方向。江西上饶灵山复式岩体具有稀有金属成矿潜力,研究对区域稀有金属找矿具有重要的指导意义。
Abstract:
Rare earth elements and rare metals are widely used in the emerging industries and national defense science and technology areas. And they are also regarded as the important key metals for the country and their prospecting is imminent. Recently, new mineral tantalaechynite-(Ce) has been discovered in Huangshan granite pegmatite around Lingshan complex massif in Shangrao of Jiangxi Province, and it has been approved by International Mineralogical Association (IMA), which not only enriches the aeschynite group minerals, but also provides a new direction for rare metal prospecting. Tantalaeschynite-(Ce) occurs in Huangshan tantalumrich pegmatite in the form of acicular or bundle aggregates, and intergrows with feldspar, quartz, fluorites. The composition is extremely enriched in tantalum, titanium and cerium, and the ideal formula is Ce(TiTa)O6. The structure belongs to the orthorhombic system, and it is composed of cerium oxygen polyhedron and titanium/tantalum oxygen coctahedron. The tantalaeschynite-(Ce) is formed in highly evolved granite pegmatite, indicating that the ore-forming environment is extremely rich in tantalum. Compared with the surrounding columbites, the sudden increase of tantalum content in tantalaeschynite-(Ce) cannot be simply explained by magmatic crystallization differentiation. The existence of boundary layer in pegmatite was put forward in the pegmatite zone-refining model, and this layer is enriched in sodium, fluorine, chlorine and other volatile components (also called fluxes). The boundary layer crystallization results in abrupt change of mineral composition, and incompatible elements are enrich in large quantities, after the exhaustion of melt component, and a large number of incompatible components are continuously accumulated and abundant. The boundary layer of highly differentiated granite pegmatite is characterized by the enrichment of volatile minerals such as albitite and fluorite, which is a vital indication for rare metal prospecting. Lingshan complex massif in Shangrao of Jiangxi Province has good potential of rare metal resources and this reasearch is of great significance for regional rare metal prospecting.
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