Geology of the principal tin deposits of Bolivia

The Bolivian tin belt with a length less than 1000 km and a width not exceeding 60 km does not extend outside its national frontiers, either north into Peru or south into Argentina. In the northern part the high Cordillera contains deposits related to granitic batholiths (Jurassic, Triassic, Cretaceous and Miocene). From Oruro to the south of the country, the lode deposits are related to small stocks and dikes of dacite and rhyolite (Pliocene) and form the famous polymetallic province, with rare associations of tin and silver like teallite, franckeite, aramayoite, andorite, argidorite, etc. The narrow vein deposits are shallow in depth and in most of the cases their vertical range is less than 500 m. There are about 1000 tin mines, most of them small and shallow. However, the wealth of some of these mines is extraordinaryfor example the production of Llallagua (Catavi) is estimated to be 600,000 tons of tin. There are still one million tons of proven and indicated reserves in the country. The tin veins are exploited by selective underground methods, despite high mining costs. Grades have declined to limits which can now be considered almost marginal