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

Abstract

The Pınarbaşı porphyry CuMo mineralization is located at northwest of Gediz (Kütahya-Turkey) and east of Simav (Kütahya-Turkey) in western Anatolia. The Pınarbaşı CuMo mineralization is hosted by Pınarbaşı granitoidic intrusion consisting of granite, granodiorite and quartz monzonite. Geochemical and geochronological evidences for Pınarbaşı granitoidic rocks show that they are high-K calc-alkaline, and I-type granitoid magma likely developed post-collisional extensional regime. The UPb zircon age of granite (18.88 ± 0.17 Ma) and quartz monzonite porphyry (18.27 ± 0.14) obtained from the Pınarbaşı granitoid show Early Miocene (Burdigalian). The Pınarbaşı CuMo 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 °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 °C, while halite dissolution temperatures are ranged from 264 to 430 °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 °C, 3.4 to 49.1 wt% NaCl eq. The late-stage homogenize at temperatures of 138 to 240 °C, and salinities of 0.9 to 6.5 wt% NaCl eq. The δ34SH2S values (0.6 to 4.5‰) of sulfides (molybdenite, chalcopyrite, pyrite and galena) and the δ18OSMOW (6.9 to 9.6‰) - δD (−71 to −86‰) values of molybdenite-bearing quartz from Pınarbaşı CuMo mineralization suggest a magmatic origin for the ore-forming fluids. The δ13CPDB (from −4.65‰ to 0.55‰) and δ18OSMOW (from 9.05‰ to 18.76‰) values of calcite which is one of the most common gangue minerals in Pınarbaşı 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 UPb 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 Pınarbaşı CuMo mineralization and confirm that mineralization is formed from an Early Miocene porphyry-related magmatic-hydrothermal system that is genetically linked with Eğrigöz and Pınarbaşı granitoids.