Abstract: A widespread, and intense hydrothermal alteration zone has developed in the Upper Cretaceous Şaplıca volcanics, in the northern part of theeastern Pontids, as a result of the intrusion of Late Cretaceous-Paleocene granitoids. Under strongly acidic, acidic, acidic-intermediate and intermediate alkaline conditions, propylitic, phyllic (sericitic), argillic (alunitization and kaolinization) alteration along with hematite and silica polymorphs, and two type oftuormaline mineralization developed under wide range of pH and Eh conditions.Alunite, kaolinite and silica are abundant in argillic alteration, whereas sericite dominates in phyllic alteration. Most of the major alunitedeposits are located along the periphery of the Şaplıca volcanic rocks and in addition contain alunite, kaolinite + quartz ± opal ± cristobalite.Illite, pyrite, barite, and gypsum also occur in small amounts.Major and some trace elements are notably concentrated in or were leached from, the volcanic rocks depending upon the alteration types. Ingeneral, Al + K and Mg + Ca + Fe were enriched in the alunitic + sericitic and propylitic alteration types, respectively. On the other hand, Ca,Mg and Fe were leached in the argillic alteration, and Fe was concentrated in hematite formation. Strong leaching ofNa was determined mainly for all alteration types. Silica generally decreased in argillic (e.g., in kaolinitic and alunitic) alteration zones. Most of trace elements weremobile during hydrothermal alteration. Y, Sc, Mo, Cr, Co, Ni, Zn tend to be mobile in acid aqueous systems and, thus, are nearly absent in thesealunitic alteration zones. In the swrounding kaolinitic envelope, these elements are present at background or slightly higher concentrations.Mainly Sr and partly Rb contents are higher in the alunic and kaolinitic zones than weakly altered parent rock. Barium content in the acidic alteration zones (alunitic and kaolinitic zone) is half about of the parent rock because of the relative insolubility of barite in acidic solutions. The lowest concentration of the element were determined in all the other alteration zones, and its content were strongly leached (about 1/10 to 1/20) fromthe weakly altered parent rocks. Pb and Cu content is increased in the propylitic zone. V is generally enriched in all alteration types comparedto weakly altered parent rocks. Such hydrothermal alteration zones can be used effectively to assess mineral exploration/evaluation of resourcesof similar alteration zones the eastern Black Sea region.