Investigations of petrographic and geochemical properties of kopuz (Torul, Gümüşhane) granitoid

The study area is located in the transition zone between the north and south zones of the Eastern Pontides Tectonic Belt. In the area, there are volcano-sedimentary rocks consisting of Upper Cretaceous aged dacite, andesite, basalt and theirpyroclasts and sedimentary interlayers and they have a wide spread. This unit is cut by the Eocene aged Kopuz Granitoid. Quaternar aged alluviums unconformably overlies the other units. The Kopuz Granitoid, which is elliptical and outcrops in an area of approximately 15 km2 , generally consists of rocks with a mineralogical composition of granite, granodiorite and quartz diorite, and mainly consists of plagioclase, quartz, orthoclase, hornblende, biotite and opaque minerals. The SHRIMP concordia age of 44.75±0.92 Ma U-Pb zircon was obtained from the magmatic zircons analyzed from the Kopuz Granitoid, corresponding to the Middle Eocene period. Kopuz granitoid generally has I-type, high K and calc-alkali affinity, metaluminum character and high SiO2 (52.36-71.81%) content. Major and trace element changes show that plagioclase, hornblende and Fe-Ti oxide differentiation play an important role in the formation of these rocks. The rare earth element patterns of the samples, which is normalized based on chondrite, are similar to each other. The light rare earth elements (LREE) in the samples are more enriched than the heavy rare earth elements (HREE), however, the HREE enrichment in granodiorites is more pronounced compared to granite and quartz diorites. The (La/Lu)N values of the rocks vary between 4.12 and 7.90, and negative Eu anomaly (Eu/Eu*=0.55-0.82) of the rocks is evident. In granitoidic samples, negative Nb (Ta) anomaly, positive Pb anomaly, negative P and Ti anomalies, enrichment of large ion radius (LIL) and LRE elements were detected. Based on their geochemical and petrological properties, it has been revealed that partial melting of lower continental crustal rocks (amphibolitic) and lithospheric mantle components are effective in the formation of these rocks. Keywords: Granitoid, Gümüşhane, Geochemistry, Kopuz, Torul, Turkey, U-Pb Zircon Age