Jeoloji Münendisliği Dergisi

Geology and Genesis of Fluorite Deposit of Ovacık (Tavşanh-Kütahya)

ABSTRACT: Epi-mesotherma! fluorite mineralization of Tertiary age occurs in allochton limestone of Late Cretaceous age. The mineralization is controlled by WNW-ESE trending young faults and related shears and extension fractures General trends of young faults are parallel to the Gediz - Simav graben system. Some dissolution cavities occured mainly m shears. Fluorite mineralization occurs in shears and dissolution cavities. Extension fractures are represented by small barite veins. Depositional texture is open space filling and represented by asymmetric banded texture in shears and symmetric banded texture in dissolution cavities. Fluorite is major ore mineral in the deposit. Calcite is major gangue mineral Minor gangue minerals are barite and uartz, No sulfide mineralization have been observed in the deposit. The host rock is limestone, Dolomitizaiton of wall rock is common and locally intense where fluorite mineralization is dominant. Two paragenetic stages have been distinguished. Mesothermal stage: Purple fluorite - quartz-green fluorite - barite, Epithermal stage: Brown calcite - pink fluorite - white calcite, Microthermometric measurements on nearly 100 two phase (1+v), phase (1) pyrimary jnclusions, yielded mean homogenization temperature of 270 C° for purple fluorite, 254 C* for quartz, 243 tf for green fluorite, 219 Cs for barite, 206 C° for brown calcite, 178 C* for pink fluorite and 160 C° for white calcite. The salinity of fluorite ranges from % 7- 84 equ iv ,wt, of NaCl, The mean homogenization temperature of monomineralic barite veins range between 219-24 fC: The REE content of fluorites are slightly variable, rangnig from from 0,11 to 5,20 ppm, Ce/Yb ratios reflect the dominant trend of light REE enrichment. The puiple fluorite harf a lower Tb^ia ratio which is indicative for earlier crystallization. Relatively higher Tb/La ratios of green and pink fluorite indicate a sequential crystallization after purple fluorite. Chondrite normalized plots an REE ratios reveal persistent negative Ce anomalies indicating high oxygen fugacities at the source area Positive Eu anomaly of purple fluorite indicates the release of Eu+2 during dolomitization limestone and oxidation to Eu+3 at deposition site and subsequent incorporation in the puiple fluorite. Negative Eu anomalies of green and pink fluorite indicate the presence of divalent Eu in the hydrothermal fluids, The geologic, geochemical and fluid inclusion data support deposition in Tertiary hydrothermal system which is characterized by sulfide mineralization and too many thermal springs around the fluorite deposit. The most likely depositional mechanism is believed to be an increase in the pH of the ore bearing fluids upon interaction with limestone which resulted in the fluorite deposition.