Petrological investigation of the Gungormez pluton (Saray-Kırklareli) in the Istranca massif

The Güngörmez Pluton is a pluton located in the Istranca massif in the northwest of Turkey and is located to the E-NE of Saray (Kırklareli). The pluton is composed of metamorphosed rocks, generally granitic or granodioritic in composition. The mineralogical composition of the rocks here is generally composed of main felsic minerals; quartz, feldspar (orthoclase, plagioclase, microcline), mafic minerals; biotite, hornblende, muscovite, and opaque minerals. Accessory minerals are composed of zircon, titanite, apatite. The texture of metagranitic rocks is defined as foliated, lepido-granoblastic texture. These textural features are a result of metamorphism and deformation processes in the region, and coarse-grained quartz and feldspars in the form of porphyroblasts are common in the rocks. In this study, it is aimed to reveal the geological evolution of the pluton and its position within the regional geological setting by examining the petrographic and geochemical properties of the Güngörmez Pluton within the Istranca massif in detail. The Güngörmez Pluton is geochemically high-K calc-alkaline and peraluminous in character. It is enriched in large ion elements (LIL; K, Rb, Ba) and significantly depleted in high persistence elements (HFS; Nb, Ta, Ti). In the rare earth element (REE) distribution, it is characteristically enriched in light rare earth elements (LREE), depleted in heavy rare earth elements (HREE) and shows a negative Eu anomaly. These chemical data indicate that the pluton developed in an arc magmatism environment with mantle-crust interaction. The Güngörmez Pluton was emplaced within the continental crust in the north of the Istranca Massif and played an important role in the geodynamic evolution of the region. The Güngörmez pluton forms a part of the Cadomian magmatism in the region and is considered as one of the felsic metagranitic plutons forming the basement of the Istranca Massif. This pluton is located in the volcanic arc granites (VAG) area in the tectono-magmatic discrimination diagrams and is considered as the products of arc magmatism. Zircon U-Th ages obtained from nearby plutons in the region vary between 525.3 ± 3.5 and 548.7 ± 2.3 Ma, suggesting that the Güngörmez pluton may also have a crystallization age in this age range. The Güngörmez pluton was evaluated together with its geological setting, mineralogical-petrographic features and geochemical features, and it can be said that this pluton, like other plutons in the region, was formed in a magmatic arc environment related to the subduction-related collapse of the Proto-Tethys Ocean southward during the Late Precambrian-Early Paleozoic period in the Istranca massif.