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。这种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。陶瓷和玻璃工业特别寻求的一种锂矿物是花瓣石，因为它具有很高的减少热冲击的能力。值得注意的是，在分离激流伟晶岩中，加拿大安大略省拥有世界上最大的瓣岩资源之一，加上另一种重要的锂矿物锂云母的大量资源。本提案中描述的研究旨在调查这些富含花瓣岩的伟晶岩的性质、分布和起源，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LCT（锂-铯-钽）类伟晶岩，其成因尚无定论。目前我们对岩浆起源的看法主要有两种假说，即Jahns和Burnham（1969）提出的水饱和岩浆假说和London（1992）提出的水不饱和假说。根据前一种假设，伟晶质结构是岩浆被水饱和的结果，水降低了黏度，抑制了成核；而后一种假设则是边界层液体结晶，富含降低黏度的网状修饰元素（B、P和F）。对于这两种模型，矿物化学在预测岩浆演化方面，将为寻找富含锂的伟晶岩提供工具。如果Jahns和Burnham（1969）的模型是正确的，那么热液流体将影响宿主岩石，并且它们的岩石地球化学可以用来开发富锂伟晶岩的载体。在这个项目中，我们将结合岩石学、矿物化学、同位素、熔体/流体包裹体和热力学分析，为Separation Rapids伟晶岩场建立一个强大的成因模型。这项研究将为一种鲜为人知的战略矿床的起源提供新的线索，并确定勘探的新指导方针。

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.