The search of formation of ametist around Gugu (Dursunbey-Balikesir, Turkey)

In this thesis, mineralogical, petrographical and geochemical features of volcanic rocks which hoşt chalcedony, quartz and amethyst bearing veins around Gugu village of Dursunbey-Balıkesir are determined. Due to investigations, volcanic rocks are represented by rhyolitic tuffs, lithic tuffs and agglomerates and also andesitic, dacitic and rhyolitic lavaş. These volcanites are characterized by high K calcalcaline and shosonitic magma series. Quartz and amethyst bearing veins occur in special type of rhyolites which contain higher amounts of K2O and lower amounts of Na20, CaO and MgO as majör elements compared to other volcanics in the investigated area. Rhyolites with amethyst bearing veins display As, Sb, Li, Cs and W enrichments. Amethyst and quartz crystalls are also enriched in As, Sb, Li and some samples show W, Mo and Sn increases. Comb, banded and cockade textures in addition to some replacement textures of the amethyst veins indicate an around 500 m. depth of formation of an epithermal system which characterize boling level for solutions of precious metal zone or a little bit upper of it. Fluid inclusion studies at amethyst and quartz crystalls point out liquid and vapour phases with 170-230° C homogenization temperatures. Enrichments in Li, Cs, As and Sb elements both at amethyst and quartz veins and crystalls may indicate a close relationship to boron and antimony deposits forming systems at Miocene at the Western Turkey. Key Words;, Petrology, mineralchemistry, geochemistry, amethyst, Balıkesir.