扬子西南缘分散元素铟镉共生成矿作用研究：以大厂、都龙锡矿为例

The three types of rare mineral resources are the strategic metal resources in China, among which the dispersed elements indium and cadmium are the irreplaceable important raw material in modern high-tech materials, and play a decisive role to the development of the world's high-tech industry. However, the researches about the unique metallogenic conditions and abnormal enrichment mechanism of the dispersed elements indium and cadmium are longstanding lag, which has seriously restricted the discovery and utilization of the scarce indium and cadmium. The cassiterite-sulfide deposits in southwestern Yangtze massif (e.g. Guangxi Dachang and Yunnan Dulong) show a very significant abnormal enrichment of indium and cadmium, and are also considered as the best natural base to explore the coexistence mineralization of indium and cadmium. This study is focused on the ore-forming fluid, coexistence regularity, element zonation, crystallization sequence, lattice structure and its carrying capacity of the indium and cadmium abnormal enrichment. From the viewpoints of both the fluid evolution and mineral crystallization, using a variety of high precision micro area research methods and means, such as LA-ICP-MS, the transmission electron microscope, the laser micro-Raman spectra, the infrared microscopy and X-ray diffraction, the main researches involve of indium and cadmium crystallography, mineralogy and geochemistry, etc. The purpose is to reveal the coexistence regularity and crystallization mechanism of indium and cadmium, to determine the unique geological setting of southwestern Yangtze massif, and to explore the crystal structure and carrying capacity. Moreover, it further enriches and develops the metallogenic theory of the dispersed elements indium and cadmium, ensuring the sustainable and healthy development of the national strategic resources.

“三稀金属”是国家战略性金属资源，其中分散金属铟镉作为现代高精端技术材料中不可替代的重要原料，对世界高科技产业发展举足轻重。然而，关于铟镉的苛刻成矿条件及其超常富集机制研究长期滞后，严重制约着铟镉稀缺资源的发现与利用。扬子西南缘（广西大厂、云南都龙）锡石硫化物矿床中铟镉超常富集，是探索铟镉共生成矿的最佳天然基地。本项目针对铟镉超常富集的成矿流体、共生规律、元素分带、结晶时序、晶格结构及其赋铟镉能力等，从流体演化和矿物结晶的视角，采用微区原位LA-ICP-MS、分析型透射电子显微镜、显微激光拉曼光谱、红外显微技术以及X射线衍射等高精度微区研究的方法和手段，深入开展铟镉的结晶学、矿物学以及地球化学等研究，旨在揭示铟镉共生规律及其结晶机制，厘定扬子西南缘铟镉富集的独特地质条件，探索赋铟镉矿物的晶体结构及其承载能力，从而丰富与发展分散元素铟镉的成矿理论，保障国家战略性资源的可持续健康发展。

分散金属铟镉属战略性矿产，物理和化学性能独特，已被广泛应用于国防军事、航空航天、现代信息等高精尖技术领域，对于战略性新兴产业发展举足轻重。保障铟镉资源储备与供给，是支撑相关战略性产业稳健发展的关键。以广西大厂和云南都龙锡石硫化物矿床为对象，研究了主要赋铟镉矿物组合的基本特征，解析了铟镉等稀土与微量元素在不同矿物中的分配，探究了分散元素铟镉的共生关系以及载体矿物标型对铟镉产出的影响与制约，揭示了铟镉共生赋存状态及其成矿规律，探讨了驱动分散元素铟镉超常富集成矿的独特成矿条件与成矿环境，深入探索了锡石硫化物矿床中铟镉共生富集的成矿机制。①揭示了都龙锡锌多金属矿床的成矿流体特征以及流体演化，发现成矿流体富K+和Cl-、贫F-，成矿流体具有岩浆热液特性，具弱酸性和还原性，可与金属阳离子结合，以络合物的形式驱动成矿元素的活化与迁移，CO2等气相成分可能参与成矿作用。②解析了都龙锡锌多金属矿床的硫铅来源及其深部构造背景，提出矿床的硫主要来自于岩浆作用，而铅表现出多来源特点，以下地壳铅为主，次为造山带铅，成矿作用总体受下地壳构造环境的影响和控制。③都龙锡锌矿床最晚期闪锌矿最富集Cd，闪锌矿中Zn与Fe呈明显的负相关性，具有显著替代关系；当Zn大量置换Fe时，矿床由高温过渡至中低温。④都龙矿床中黄铁矿和磁黄铁矿的Rb-Sr同位素等时线年龄分别为81.0±5.4Ma和84.7±3.1Ma，成矿主要发生于晚白垩纪，与岩浆热液联系紧密且晚期阶段对矿床叠加改造显著，成矿物质可能来源于基底前寒武系变质岩和老君山岩体。⑤大厂矿田黄铁矿继承了岩浆岩和围岩特征，其高场强元素U、Sm和Lu富集，其他微量元素亏损，黄铁矿成矿具有多阶段性。该项目研究成果有助于揭示铟镉共生关系及其成矿规律，丰富与发展铟镉共伴生超常富集成矿理论，为分散金属找矿预测和勘探增储提供重要科学依据；同时，助力战略性铟镉资源的高效回收与综合利用，为相关战略性产业稳健发展提供坚实保障。