Spilites, Serpentinites and Associated Rocks of the Mossburn District, Southland By J. J. Reed N.Z. Geological Survey [Read before Wellington Branch, October 9, 1947; received by the Editor, January 10, 1949; issued separately, February, 1950.] Contents Introduction and Acknowledgments. Summary of Geological History. Previous Work. Topography. Mossburn Group. Geological Occurrence. Petrography of argillites, greywackes, and volcanic tuffs. Petrography of limestone. Petrography of spilites, albite dolerites and keratophyres. (i) Structure, (ii) Mineralogical features. (iii) Petrogenesis: (a) spilites, (b) albite dolerites, (c) keratophyres. Age and Correlation. Serpentinites And Associated Rocks. 1. Geological occurrence. 2. Economic use of serpentinite. 3. Petrology. (a) Petrography of serpentinites. (b) Petrogenesis of serpentinites. (c) Petrography of altered dolerites and gabbros. (d) Petrogenesis of altered dolerites and gabbros. 4. Tectonic significance and date of intrusion. Conclusions. Literature Cited. Introduction and Acknowledgments This paper embodies the results of a field and laboratory investigation of approximately 80 square miles of the Eyre, Lincoln and Burwood Survey districts of Southland (Fig. 1). The field mapping was carried out during three months of 1944, and was hindered by the lack of a good base map and by the wooded and rugged nature of the country. The laboratory work involved the examination of 200 rock sections and 450 hand specimens. The paper was prepared originally at the University of Otago during the tenure of a Smeaton Research Scholarship and the manuscript subsequently revised at the New Zealand Geological Survey. The writer desires to express his gratitude for the assistance and guidance given at all times by Professor W. N. Benson and Dr F. J. Turner. Mr R. W. Willett assisted in the field on several occasions. Acknowledgment is made of a monetary grant from the Scientific and Industrial Research Department to defray part of the field expenses. The assistance of the Cawthron Institute in undertaking cobalt analyses of serpentinite rock and soils is also gratefully acknowledged. The author is particularly indebted for the hospitality extended by Mr and Mrs G. Hamilton, “Cloverdon,” Lowther, and by Messrs Taylor, of the West Dome Station.