Metamorphism in the Moine Nappe of northern Scotland

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Abstract
The paper summarizes current hypotheses regarding Moine metamorphism, assesses their validity, and presents a metamorphic synthesis based on existing evidence and on new observations and inferences. The writer adopts the hypothesis of thermal zoning falling in grade westwards from a SSW-NNE belt of migmatisation. Migmatisation, thermal zoning and folding are regarded as penecontemporaneous and of early Caledonian age. Late-Caledonian movement along the Moine Thrust-plane is supposed to have taken place while the Moines were still hot, zonal temperatures being carried westwards in the Moine Nappe. Dislocation-metamorphism east of the outcrop of the Moine Thrust is thus regarded as high-grade, the operative temperatures not being lower than those of the Garnet Zone. Retrograde dislocation-metamorphism is believed to be restricted to the immediate vicinity of cold rocks below the Moine Thrust. Evidence is also presented of the equivalence of Moine and Sub-Moine sedimentary rocks, in Sutherland and Morar respectively.