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

点击翻译按钮获取中文摘要

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.