Petrology of the Carboniferous igneous rocks of the Tweed Basin

I. Introduction and Acknowledgments. In February 1937 I read before this Society the original draft of this paper. Since then a certain amount of work on the area has been published. It includes a paper by Eckford and Ritchie (1) and two preliminary reports on the progress made by the Geological Survey in the revision of Sheet 25 (2, 3), which embraces the greater part of the area. The present work is concerned mainly with the petrology and chemistry of the basic igneous rocks of this district and therefore only slightly overlaps the work of the Geological Survey. I began working in this district many years ago, but delayed publication in order to make my collection of material as large and inclusive as possible. Even so, the rich petrological potentialities of this area are by no means exhausted in the present paper and a still richer harvest may be gathered in the future. It gives me great pleasure to record my thanks to Mr R. J. A. Eckford, Dr A. G. MacGregor and Mr A. Fowler, in whose company I have examined certain parts of this district and who have put at my disposal much valuable information, but my thanks are particularly due to Dr A. G. MacGregor, who has kindly read the typescript of this paper and made many suggestions, although he is not responsible for any opinions expressed in the paper. II. Scope of Work. The rocks under investigation occur in a wide tract of country which stretches