Modelling the genesis of the Separation Rapids petalite-lepidolite pegmatites as a guide to their exploration

由于对全球变暖的担忧以及政府决定用锂离子电池驱动的电动汽车取代汽油和柴油汽车，锂的需求非常高。这一需求也强烈影响了其他需要锂的应用，特别是在陶瓷/玻璃行业。锂长石是陶瓷和玻璃工业特别需要的锂矿物，因为它具有降低热冲击的高能力。值得注意的是，在分离急流伟晶岩，安大略，加拿大有一个最大的透锂长石资源在世界上加上锂云母，另一个重要的锂矿物的大量资源。这些透锂长石的分布和来源丰富的伟晶岩作为确定其成因和开发对其成功勘探至关重要的工具的总体目标的一部分。伟晶岩属于LCT（锂-铯-钽）类伟晶岩，其成因尚无共识。目前有两种假说主导着我们对它们起源的看法，即Jahns和Burnham（1969）的水饱和岩浆假说和伦敦（1992）的水不饱和假说。根据前一种假设，伟晶岩结构的结果，从饱和的岩浆与水，降低粘度和抑制成核，而对于后一种假设，他们被解释为结晶从边界层液体富含网络修饰元素（B，P和F），降低粘度。对于这两个模型，矿物化学，在预测岩浆演化，将提供针对富锂伟晶岩的工具。如果Jahns和Burnham（1969）的模型是正确的，那么热液流体会影响寄主岩石，它们的岩石地球化学可以被用来开发富含锂的伟晶岩的载体。在本项目中，我们将利用岩相学、矿物化学、同位素、熔体/流体包裹体和热力学分析的组合，为分离急流伟晶岩区开发一个可靠的成因模型。这项研究将揭示一个鲜为人知的战略性矿床的起源，并为勘探确定新的指导方针。**

Lithium is in very high demand because of concerns about global warming and government decisions to replace gasoline and diesel vehicles with electric vehicles powered by lithium-ion batteries. This demand also strongly affects other applications requiring lithium, notably in the ceramic/glass industry. A lithium mineral that is particularly sought by the ceramics and glass industry is petalite, because of its high capacity to reduce thermal shock. Significantly, in the Separation Rapids pegmatites, Ontario, Canada has one of the largest petalite resources in the World plus large resources of lepidolite, another important lithium mineral. The research described in this proposal is designed to investigate the nature, distribution and origin of these petalite-rich pegmatites as part of an overall objective to determine their genesis and develop tools that will be important to their successful exploration. The pegmatites belong to the LCT (Lithium-Cesium-Tantalum) class of pegmatites, for which there is no consensus on genesis. Two hypotheses currently dominate our view of their origin, the water-saturated magma hypothesis of Jahns and Burnham (1969) and the water-undersaturated hypothesis of London (1992). According to the former hypothesis, pegmatitic textures result from saturation of the magma with water, which lowers viscosity and suppresses nucleation, whereas for the latter hypothesis, they are explained by crystallisation from a boundary layer liquid enriched in network modifier elements (B, P and F) that reduce the viscosity. For both models, mineral chemistry, in predicting magma evolution, will provide tools for targeting lithium-rich pegmatites. If the Jahns and Burnham (1969) model is correct, then hydrothermal fluids would have affected the host rocks, and their lithogeochemistry could be used to develop vectors towards lithium-rich pegmatites. In this project, we will make use of a combination of petrographic, mineral chemical, isotopic, melt/fluid inclusion, and thermodynamic analyses to develop a robust genetic model for the Separation Rapids pegmatite field. The study will shed new light on the origin of a poorly understood strategic class of mineral deposits and, identify new guidelines for their exploration. **