LOW-GRADE METAMORPHISM OF THE MANX GROUP, ISLE OF MAN - A COMPARATIVE-STUDY OF WHITE MICA CRYSTALLINITY TECHNIQUES

Studies have been made in two laboratories on metapelites from the Manx Group, Isle of Man, showing the distribution of white mica "crystallinity', using the Kubler index (Δ°2θ) and the Weber index (Hbrel). Two isocryst maps, which show broadly similar distributions of metamorphic grade, are illustrated and a correlation between the laboratories is presented. The mineralogy of the < 2 μm fraction in relation to "crystallinity' has been determined. The distribution of metamorphic grade over central and eastern parts of the Isle of Man, as depicted by the Kubler index isocryst map, is related to subjacent granite plutons, but these contact metamorphic effects overprint an earlier, largely anchizonal, regional metamorphism. Localized, late, retrograde effects are related to low temperature hydrothermal mineralization and to cold re-working in a large fault zone. -from Authors