The first part of the title of this conference is also the title of an international group co-ordinating research in this field. This meeting was held at the request of the Group's British representatives and produced varied group of papers covering mineralization in both the volcanic and plutonic associations.
It had been hoped that Dr M. Štemprok would give an opening address but, as he was unable to be present, Dr Alan Bromley kindly stepped into the breach. In a very comprehensive survey of the field he commenced with the problem of the generation of granitic magmas particularly those associated with subduction zones, because at this plate juncture we often see a zoning of metallic deposits which suggests derivation of the metals from the subduction zone, with perhaps the rising granite magmas acting only as carriers. The metals probably move as complex halide ions with, perhaps for tin, the possibility of fluoride, liberated from the breakdown of apatite, being the carrier ion. Bromley emphasized the importance of manganese nodules as carriers of many metals down the subduction zones but not of tin and tungsten. He noted that in Cornwall, joints in mineralized areas are coated with much manganese and posed the question, 'Does manganese give a broad halo useful in exploration in such areas?'
Manganese nodules and the sediments of layer 1 of the oceanic crust could supply the metals of deposits in the zones nearest to the trenches. However, the genesis of tin and tungsten ores seems