Iodine in granitic and associated rocks

48 samples of granitic and associated rock types have been analysed for iodine. Granites from the British Isles (mean 0.27 ppm) are generally richer in I than granites from other areas of the world (mean 0.10 ppm), the highest values being recorded for granites from North Wales (up to 0.72 ppm). There is no significant enrichment of I in pegmatitic or aplitic rocks, while I is lower in kaolinished granites than in unaltered granites. In general, 60-100% of the iodine in the rocks analysed is water soluble. It is suggested that whereas small amounts of I may occur within the lattices of some minerals most of it is present in fluid and/or soluble solid inclusions.