Tin-bearing granites are widely distributed in all the continents yielding many economically valuable deposits. Tin mineralization related to granite occurred from Proterozoic to Neogene age.
Comparative studies of mineralised granites were carried out, taking examples from well known type areas viz., the tin granites from Malaysia of Asia, Cornwall granites from Europe, Bushveld from Africa, Bolivian granites from South America, Alaskan granites from North America and Tasmania granites from Australia. Geochronologically the tin-bearing granites could be broadly grouped into 5 tectono-magmatic crustal orogenies viz., Precambrian, Caledonian, Variscan, Kimmeridigan and Alpine.
Tin-bearing granites range in composition from granite to granodiorite with minor variations. Biotite granite and two-mica leucocratic granites devoid of amphibole and other ferromagnesian minerals are generally more fertile. Zircon, apatite, monazite, allanite and xenotime are found as typical accessory minerals. Polyphase palingenetic granites formed in the last stages of orogeny mostly in hypabyssal intrusion level in the mobile region are found to be more congenial for mineralization. Shallow dipping Benioff zones with adjoining sialic components, continent-continent collision and intra-continental rift zones constitute many tin granites. Late magmatic autometasomatism (microclinization, albitization) and post- magmatic metasomatism (greisenization) are common alterations found in tin-bearing granites.
Geochemically the tin granites have slight rise in silica and potash and appreciable fall in ferromagnesian constituents especially MgO, CaO, Fe₂O₃ and TiO₂ than normal granites. There is enrichment of F, Li, B, Rb, Be and depletion of Cr, Ni, Co and V. The study indicated that geological setup, structural frame work, tectono- magmatic regimes, geochemical characteristics and alteration patterns of tin fertile granites of the world display many striking similarities and certain interesting inherent deviations.