Lemitar Mountains

The Lemitar Mountains are composed predominantly of Precambrian granites, diorite-gabbro, and arkoses and quartzites of the Corkscrew Canyon sequence. All these rock types are cut by numerous carbonatite dykes which vary from a few centimetres to a few metres in thickness, but can rarely be followed for more than several hundred metres. A sodium metasomatism occurs along some dykes cutting diorite-gabbro and is manifested by a reddening and development of large albites. One group of dykes contains 10-40% of country rock xenoliths, including red fenitized granite, the matrix consisting of 50-70% carbonate, 5-15% biotite-phlogopite, 5-10% magnetite, 5-10% apatite, a little feldspar and minor fluorite, quartz, chlorite and bastnaesite. Xenolith-free dykes define calcite-dolomite and ankeritic varieties, the latter cross-cutting the former; baryte is found in the ankeritic dykes. Chemical data are available (McLemore, 1980, Tables 2 and 3).