Skarn Alteration and Au-Cu Mineralization Associated with Tertiary Granitoids in Northwestern Turkey: Evidence from the Evciler Deposit, Kazdag Massif, Turkey

The Eveiler Au-Cu district is located in the Kazdag region of northwestern Anatolia, Turkey. Skarn alteration and Au-Cu mineralization assemblages are related to an elliptical T-type, magnetite series, metaluminous, calcalkaline body, which has intruded the Kazdag Massif. The skarns have an oxidized mineralogy dominated by garnet (Ad(85)Gr(15)-Ad(50)Gr(50)) hedenbergitic pyroxene (Di(70)Hd(30)-Di(25)Hd(75)), epidote, amphibole, and chlorite and contain lip to 80 percent sulfides (pyrrhotite >> pyrite + chalcopyrite). The massive pyrrhotite-bearing mineralization replaced prograde skarn and marble. At least two paragenetic stages of skarn formation and ore deposition have been recognized: stage I hedenbergitic pyroxene +/- garnet +/- scapolite +/- quartz +/- magnetite, and stage II amphibole +/- epidote +/- chlorite +/- quarta +/- calcite and pyrrothite + chalcopyrite +/- pyrite. Early skarn formation (stage I) was dominated by anhydrous minerals, hedenbergitic pyroxene, and garnet. The hydrous skarn assemblage (stage II) replaced early-formed skarn assemblages. Clinopyroxene is hedenbergite rich, whereas garnet is andraditic. The mineralogy and character of the Eveiler skarn is Consistent with deposition under oxidized conditions, formation at shallow crustal levels and similar to those of other Cu-Au, Febearing skarn systems. Stable isotope data indicate that magmatic water was involved in the early stage of skarn formation (delta O-18(H2O) = 6.3-10.9 parts per thousand) and a mixed magmatic-meteoric water was responsible for the subsequent mineralization (delta O-18(H2O) = -4.6 to 1.0 parts per thousand, delta D-H2O= -30.9 to -17.7 parts per thousand).