Field relationships, mineralogy and chemistry of the greisens and related rocks associated with the Eskdale Granite, Cumbria

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Abstract
SUMMARY: Greisens in the Eskdale Granite are shown to be far more numerous, widespread and variable than was hitherto suspected. Most are quartz-mica, quartz-topaz or quartz greisens and occur near the granite margins. An exceptional facies of quartz-topaz greisen containing andalusite occurs on Water Crag, Devoke Water, from where a unique quartz-andalusite rock is described. Greisens away from the granite contact differ in several mineralogical and chemical respects. Eskdale greisens differ from those in Cornwall and elsewhere in being impoverished in lithium; their nearest analogue appears to be the Grainsgill Greisen associated with the Skiddaw Granite. Field and petrochemical evidence is consistent with metasomatic alteration of granite, but the origin of the quartz-andalusite rock remains enigmatic.