Spodumene: The key lithium mineral in giant lithium-cesium-tantalum pegmatites

Abstract

寻找传统化石燃料的替代能源已成为全球性议题。受动力电池消费的拉动，锂资源需求急剧上升，伟晶岩型锂矿勘查热度持续攀升。虽然众多伟晶岩型锂矿地质特征尚不清晰，已有证据表明锂辉石是大多数大型-巨型伟晶岩型锂矿床的主要含锂矿物。与许多近直立的伟晶岩脉群不同，世界范围内大多数太古代伟晶岩矿脉往往呈近水平或缓倾斜在角闪岩相围岩中产出，它们往往具有复杂的三维形态并发育明显的矿物和地球化学分带。这些太古代伟晶岩脉通常形成于挤压或压剪构造体制下同变质环境中，成岩期最小主应力（σ₃）近竖直。因此，伟晶岩常常侵位于近水平的构造局部引张区而形成复杂的几何学形态。压性的构造环境为富锂熔体多次脉动式注入和富含挥发分熔体垂向结晶分异提供了充足的时间；锂辉石在中高温压条件下结晶成为缓倾富锂带中最为常见的含锂矿物。;As alternate energy sources have become a global issue, the demand for lithium has increased and there has been greater exploration for lithium pegmatite deposits. Although the geology of many of these deposits is poorly documented in the modern literature, it is evident that most major to giant pegmatites have spodumene as the economic lithium mineral rather than other lithium minerals. These largely Archean economic pegmatites throughout the world are normally sub-horizontal to gently dipping, in contrast to many near-vertical pegmatite-swarms, commonly have complex 3D geometries, are strongly mineralogically and geochemically zoned, and are hosted in amphibolite-facies wallrocks. The complex geometries and flat dips are consistent with syn-metamorphic emplacement in dilation zones within a compressional to transpressional regime with a near-vertical minimum principal stress, sigma 3. This would have allowed injection of multiple pulses of lithium-enriched melt and greater time for vertical pegmatite differentiation of volatile-rich pegmatitic melts during prolonged cooling, and importantly, for spodumene to crystallize as the most common medium to high P-T lithium phase in flat-lying lithium-rich zones.