Abstract:

In this study, the granitoid rocks exposed in the Pelitli (Bayburt) area was investigated to determineits petrographical and geochemical characteristics. In the studied area located on the northernzone in the eastern Pontides, the basement is represented by Eocene aged andesite and pyroclastic rocks. These units are cut by the Eocene Pelitli Granitoid (46 Ma, U-Pb zircon) and are overlaine uncorformably by Quaternary alluvium. Pelitli Granitoid is in ellipse shape and settled approximately in an area of 16 km2. The Pelitli Granitoid consists of diorite, tonalite, granodiorite and granite, and includes plagioclase, orthoclase, quartz, hornblende, biotite and rare pyroxene as main minerals. The rocks of the granitoid are generally I-type, low to high K calc-alkaline, metaluminous to slightly peraluminous characteristics. They are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE). (La/Lu)N values are between 5.6 and 12.2 with pronounced negative Eu anomalies (Eu/Eu*=0.3-0.9) of the Pelitli Granitoid rocks. Major and trace element variations indicate significant role of plagioclase, pyroxene, hornblende and Fe-Ti oxide fractionation during the evolution of granitoid. As determined by zircon and apatite saturation thermometry, the estimated crystallization temperatures range from 690 °C to 897 °C. The geochemical compositions of the Pelitli Granitoid suggest an origin through partial melting of meta-igneous (amphibolitic) source rocks.

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