TUNGSTEN-TIN MINERALIZATION IN BAMSAR-REVESHT REGION, CENTRAL IRAN

Southwest of Shazand in central Iran is a potential region for tungsten and tin. Apart from Nezam-Abad tungsten deposit, Bamsar and Revesht are among the already discovered tungsten-tin occurrences in the region. The study of such occurrences will lead geologists in finding new deposits.

Paleozoic and Triassic volcano-sedimentary rocks and upper Triassic-Jurassic detrital-chemical and volcanic units outcrop in the Bamsar-Revesht region. Upper Triassic-Jurassic rocks consist of phyllites, micaschists, quartzites, metamorphosed cherty limestones as well as metamorphic acidic and basic tuffs. The intrusives in the region have granitic and granodioritic compositions which have caused metamorphic haloes in the upper Triassic-Jurassic units.

Six ore-bearing skarn horizons have been identified at Bamsar. Country rocks at Bamsar are mainly calcareous actinolite-tremolite-diopside-quartz schists in which ore minerals occur in fine-grained laminas and coarse-grained garnet-bearing diagenetic veins and layers. Ore paragenesis at Bamsar includes scheelite, chalcopyrite, arsenopyrite, sphalerite, pyrite, cassiterite, chalcocite and covellite. Granodioritic intrusives host vein-type mineralization at Revesht. Ore paragenesis of Revesht mineralized veins comprises scheelite and arsenopyrite.

Bamsar ore-bearing samples have identical chondrite-normalized REE patterns when compared with those of the metamorphic rocks in the region. Samples of scheelite at Bamsar exhibit REE patterns which show derivation from a reduced fluid with moderate Na activity. On the other hand, REE patterns for samples of scheelite from Revesht are different from those of Bamsar scheelites and imply that Revesht scheelites formed from an oxidized fluid with moderate Na activity.

Geological, textural, mineralogical and geochemical studies suggest that Bamsar occurrence is sedimentary-diagenetic in origin, subsequent concentration happening through Late Kimmerian regional metamorphism and deformation. Also, considering spatial position and proximity of Bamsar ore-bearing horizons with granodioritic intrusions hosting vein-type mineralization at Revesht, it is likely that Revesht mineralized veins formed through assimilation of stratiform and stratabound ores by a granitoid magma.