Geochemical, stable isotopic (S, O, H, C), microthermometric and geochronological (U-Pb) evidence on the genesis of the Pinarbasi porphyry Cu-Mo mineralization (Gediz-Kutahya, Western Turkey)

Abstract

The Pinarbasi porphyry Cu-Mo mineralization is located at northwest of Gediz (Kutahya-Turkey) and east of Simav (Kutahya-Turkey) in western Anatolia. The Pinarbasi Cu-Mo mineralization is hosted by Pinarbasi granitoidic intrusion consisting of granite, granodiorite and quartz monzonite. Geochemical and geochronological evidences for Pinarbasi granitoidic rocks show that they are high-K calc-alkaline, and I-type granitoid magma likely developed post-collisional extensional regime. The U-Pb zircon age of granite (18.88 +/- 0.17 Ma) and quartz monzonite porphyry (18.27 +/- 0.14) obtained from the Pinarbasi granitoid show Early Miocene (Burdigalian). The Pinarbasi Cu-Mo mineralization predominantly comprises molybdenite, chalcopyrite, galena, sphalerite, pyrite, fahlore, magnetite, bornite, hematite, jarosite, malachite and orpiment occurred in disseminated form in veins/veinlets associated with potassic, phyllic (sericitic) and advanced argillic alteration zones. According to the paragenetic and crosscutting relationships of veins/veinlets, the ore-forming process were divided into three stages; early-stage: quartz - molybdenite +/- K-feldspar +/- pyrite veins associated with potassic alteration, middle-stage: quartz +/- calcite +/- chalcopyrite +/- galena +/- sphalerite +/- molybdenite + pyrite veins in phyllic alteration and late-stage: quartz +/- calcite +/- pyrite veins associated with advanced argillic alteration. Three types of fluid inclusions in quartz distinguished were designated as L-rich L + V phases (Type-I), salt-bearing L + V + S (Type-II), and V-rich L + V phases (Type-III). FIs of the early and middle stages are predominantly Type-II and Type-III inclusions, whereas the late-stage minerals commonly contain Type-I inclusions. Homogenization temperatures and salinities of FIs trapped in the early-stage quartz range from 481 to 590 degrees C and 13.19 to 61.1 wt% NaCl equivalent, respectively. FIs in quartz of the middle-stage yield homogenization temperatures (Th) of 310 to 460 degrees C, while halite dissolution temperatures are ranged from 264 to 430 degrees C, and salinities of 7.9 to 50.3 wt% NaCl eq. Homogenization temperatures and salinities of FIs in calcite of the middle-stage are range from 270 to 420 degrees C, 3.4 to 49.1 wt% NaCl eq. The late-stage homogenize at temperatures of 138 to 240 degrees C, and salinities of 0.9 to 6.5 wt% NaCl eq. The delta S-34(H2S) values (0.6 to 4.5 parts per thousand) of sulfides (molybdenite, chalcopyrite, pyrite and galena) and the delta O-18(SMOW) (6.9 to 9.6 parts per thousand) - delta D ( - 71 to - 86 parts per thousand) values of molybdenite-bearing quartz from Pinarbawsi Cu-Mo mineralization suggest a magmatic origin for the ore-forming fluids. The delta C-13(PDB) (from - 4.65 parts per thousand to 0.55 parts per thousand) and delta O-18(SMOW) (from 9.05 parts per thousand to 18.76 parts per thousand) values of calcite which is one of the most common gangue minerals in Pinarbasi mineralization show a high temperature influence and/or sedimentary contamination process to magmatic carbonate as well as continental carbonate. The S-O-H-C and U-Pb isotopic compositions indicate that the metallic elements and fluids came primarily from a magmatic source linked to Miocene intrusion. The geological, geochronological, and geochemical data support a magmatic-hydrothermal origin for the Pinarbasi Cu-Mo mineralization and confirm that mineralization is formed from an Early Miocene porphyry-related magmatic-hydrothermal system that is genetically linked with Egrigoz and Pinarbasi granitoids.