Alunite occurrences, related to Upper Cretaceous volcanic rocks of acid to intermediate composition from northern part of Sebinkarahisar, located in the south of eastern Black Sea region of Pontid provenance. Upper Cretaceous aged volcanic rocks of the Sebinkarahisar volcanic field intruded by same aged acidic plutonics and unconformably overlie Palaeozoic volcanic and ophiolitic rocks (Ayan and Dora, 1993). Eocene and Miocene-Palaeocene volcanic and sedimentary rocks covers the other volcanic and plutonic. Saphca volcanites remarkably altered by hydrothermal solutions and comprises of riyolite, dacite, and andesite lava and pyroclastics. Most of the replacement alunite deposits are located in the low hills of volcanic complexes and abundant in the centre of the advanced argillic alteration zone develops laterally outward from the alunite border. Most of the large replacement of alunite deposits in Sebinkarahisar volcanic field are located around the periphery of Saphca volcanites and contain alunite and kaolinite, quartz_ opal___ cristobalite. lllite and most rarely illite-smectite present whereas hematite, jarosite are common and more prevalent than pyrite and baryte or gypsum. Alunite replacement are generally observed in generally fault and contact zones and partly in pyroclastics by means of porosity controlled. Some spring waters are seen especially in these locations, pH of these waters are between 2.33 to 6.40. Vertically, the replacement of these deposits vary systematically downward from a quartzose cap though hematitic, jarositic, alunitic and finally propylitic zones. The complete sequence can be observed at only a few deposits but can be pieced together from several different localities (Celik and Karakaya, 1997). The replacement alunite forms massive, finegrained, white to light pink aggregates that are slightly denser than less altered rocks. Most of the texture of the pre-existing volcanic rock has been obliterated in the alunite zone, but relict clasts and phenocrysts can be discerned wither the transition zone to kaolinite. In thin section, the alunite appears as an interlocking and granular quartz with minor hematite dust. Small, spotty patches ofjarosite occur near the top of alunite zone. Most of the pre-existing volcanic rock here is replaced by an alunite-quartz mixture, but jarosite adds a golden-brown colour. Hematite forms a characteristic bright red stain on incompletely altered volcanic that contain some alunite and quartz. The hematite is distributed vertically as a band above the jarosite zone and beneath the flooded silica zone. Dense granular quartz of the flooded zone forms the top of the alteration sequence and commonly forms resistant caps on the highly coloured hills. Much of the quartz is massive, light grey has a concoidal fracture, and contains brecciated fragments of volcanic rocks. It consist of a microgranular intergrowth of quartz crystal locally containing disseminated aggregates of fine-grained hematite crystals. X-ray diffraction analysis of these samples showed that distribution of most trace elements correlates inversely with alunite content. K20 and A1203 in alunite deposits are found to be in the range 6.50% to 7.30% and 15.70% to 46.80%, respectively. Size of alunite crystals ranges between 2~tm and 15~tm. Alunite crystals sometimes observed in euhedral shape and especially amorphous crystals contain much silica (between 5% to 12%) in EDS analysis. The trace elements Y, Sc, Mo, Cr, Co, Ni, Zn to be mobile in acid aqueous systems and are nearly absent in the zone. In the surrounding kaolinitic envelope, on the other hand, these elements are present in background or slightly higher concentrations. In illitic zone, Rb and Sr content are high. Barium is highest close to the alunite zone because of the relative insolubility of baryte in acid solutions. The spring waters are meteoric in origin and they are rich in especially SO4, K, A1 and partly Fe, Si and Ca. The colour of waters varies colourless to brown and around the source of waters recent mineralization such as gypsum, alunite, goetite are determined.