Abstract: Başnayayla molybdenum-copper mineralization is related to granitic rocks ofPaleocene age (?) which are located on thenorthern edge of the Central Anotalian Crystalline Complex and Kırşehir Massif, approximately 15 km southwest of Yozgat district The rock units around the mineralization are; Kamışcıdere gabbro, Başnayayla granitoid, Beşiktepe volkanosedimentary series and alluvium. Başnayayla granitoid consists of biotite granite, microcline granite, andalusite-sillimanitegranite ve two mica granite together with felsic dikes. Kamışcıdere gabbro and Başnayayla granitoid are cut by felsic andmafic veins. Molybdenum-copper mineralization is hosted by biotit granite, andalusite-sillimanite granite and two mica granite with cordierite granite, aplite granite and quartz veins of the Başnayayla granitoid surrounded by Kamışcıdere gabbro andBeşiktepe volkano-sedimentary series Molybdenum mineralizations are occured as molybdenite-bearing quartz veins/veinlets, coatings in joints and cracks and,disseminations in the host rock. Main ore minerals are molybdenite, pyrite, chalcopyrite and magnetite. Cubanite, pyrrhotite,sphalerite, galena, ilmenite, bornite and bismuthinite are also encountered in traces. Limonite, hematite, marcasite, chalcociteand covellite are occured as secondary minerals. Three types of alterations related to the mineralization were determined andthese are quartz+s e ricite+py rite, quartz+feldspar+biotite and quartz+feldspar+biotite+sericite/muskovite associations. Molybdenum mineralization is generally seen between quartz+sericite+pyrite and quartz+feldspar+biotite alteration zones andwithin quartz+feldspar+biotite alteration zone.The mineralizations my be defined as low-grade porphyry and/or stockwork molybdenum-copper type when the ore types,mineralogy and alteration properties are taken in account. Başnayayla granitoid which involves Başnayayla porphyry and stockwork molybdenum-copper mineralization posseses the different properties than those of the host rocks mentioned in theliterature from the points of origin and geotectonic environments. On the basis of mineralogical, petrographical andgeochemical data, although it has the properties of 1- and S-type granites, the properties of the S-type is dominant in theBaşnayayla granitoid. From the geotectonic environments point of view, the Başnayayla granitoid possesses the features of thesy n-co His ional granites.