Mineralogy and Genesis of the Çanakçi (Ulukisla-Nigde) Baryte Vein Deposits, Central Turkey

Abstract

The studied area is located around (~anakqi (Ulukisla) Village in the north of Bolkardag Unit, Central Turkey. The baryte mineralization occurs within Elmali vulcanite member belonging to UpperPalaeocene aged ~iftehan complex which overlies unconformably the Alihoca ophiolites. The complex on the basis of lithological features can be divided into four members; Kodak shale-sandstone, Elmali volcanite, Aktastepe limestone and Ugtepe monzonite-diorite. The Elmali volcanites consists of basalt, andesite and trachyte lava flows, hypabyssal rocks, pillow lava and agglomerate. The lava flows have a E W strike and are cut by hypabyssal rocks of different phases. The baryte mineralizations occur nearly 2km southeast-east and 3km southwest of ~anakgi village. The baryte mineralization in SW of ~anakgi village has nearly lm thick and 33m length. Many small veins of baryte, nearly parallel to the main ore, are also present in the surrounding areas. Baryte veins contain mainly some galena. Minerals were identified by ore microscopy, and major and trace element analyses were performed by the XRF method. Mineralogy Megascopically, baryte ore is crystall ine, white and p ink i sh white in colour . Microscopically, small amount of quartz is accompanied with baryte mineral. Baryte occurs mainly as euhedral but sometimes anhedral crystals. Baryte crystals are colourless, perpendicular sets of cleavage and greyish interference colours indicating small brefringence. Crystals are characterised by polysynthetic twinning, undulatory extinction due to mechanic terrain in common. Mechanic twinning and like moiler texture are also observed in minerals. Baryte is cut by very thin quartz, sphalerite and galena veins and some baryte inclusion formed in some quartz crystals, all of which indicates that baryte is formed early than quartz, sphalerite and galena. The baryte crystals may also show fibrous or prismatic habit with patchy extinction reflecting the presence of considerable stresses during or after the deposition of baryte. The common opaque minerals are mainly galena, and rare sphalerite, chalcopyrite, pyrite, covellite, ilmenite and fahlore. Secondary minerals are anglesite, malachite, azurite, smitsonite, iron oxide and cerussite. The gangue minerals are represented by quartz, calcite chlorite and muscovite. Chemistry Selected 4 samples from baryte occurrences were analysed for major and trace elements (Table 1). As seen in Table 1, there is a negative correlation between the Ba and Al203. Feldspar, muscovite and possibly some clay minerals are present in order to account for the A1203 content that ranges between 3.07-12.35%. FeO is very low (0 .1-0 .5%), suggesting that baryte mineralization occurred at very low temperatures. Extremely low Na20 and CaO contents show clearly that calcium and sodium enriched fluids did not come to deposition environment during the baryte mineralization. Na20 and K20 occur principally as soluble salts mostly taking the form of chlorides, MgO does not behave as a soluble salt. The main impurity is SiO2 (mainly in the form of quartz mineral) and ranges between 2.1-17.81%. High ratio of Cu (109-161ppm) and TiO2 (0.12-1.56 %) reveals that the mineralising fluids are of hydrothermal origin and mineralising fluids came up from through volcanics and intrusive rocks. S content of the baryte minerals are between 63984 and 74306 ppm suggesting that the baryte mineralization is epithermal in origin. In addition, the high Sr values (9605-13603ppm) reflect that the origin of Sr is related with volcanic activity. The very high BaJSr ratio implies that the origin of Ba is the hydrothermal (especially epithermal) origin (Werner, 1958; Starke, 1969). Zn content ranges from 2 to 793 ppm, suggesting that the baryte occurrence is related with volcanic activity (Marchig et al., 1985). Pb