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The metamorphic and granitic rocks of north-western Donegal are being investigated by a research group, mainly from the Geology Department of Imperial College, London. The present paper is the first of a series in which the detailed geology will be described and material assembled to provide eventually a synthesis of the geological history of one of the most interesting plutonic regions of the world. In these investigations all mapping is of outcrop type, the minimum scale being six inches to the mile.
This first communication gives the pattern of the plutonic history of a key-area characterized by a long sequence of granitic manifestations varying with time and crustal environment. The position of the area is shown in Fig. 1. It falls within sheet 15, published in 1890, of the one-inch Geological Survey map; the description of the geology of this sheet is included in the memoir for North-West and central Donegal, published in 1891. The rocks encountered are a varied series of folded metamorphosed sedimentary rocks, presumably Dalradian, with associated basic igneous intrusions that become involved in migmatitic and granitic complexes of diverse characters.
Earlier work on this small area will be most approriately dealt with in the final synthesis, where the development of ideas on the whole Donegal research field will be considered. Two aspects of this earlier work may, however, be mentioned. First, the attempts to determine the succession of the sedimentary strata are of little value in the absence of modern sedimentation techniques. Second, the opinions on
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