Abstract The Eastern Pontides Orogenic Belt (EPOB) as a well-preserved ancient magmatic arc situated in the eastern part of the Sakarya Zone and has key importance to allow for proper reconstruction of the geodynamic evolution of the region. The region accepted as important part of Alpine–Himalayan Belt comprises of many granitoids of the Late Cretaceous age. This paper presents new mineral chemistry, bulk-rock petrochemistry, U-Pb geochronology and radiogenic and stable isotope geochemistry data from the Arpakoy and Oyman granitoids in the north part of the EPOB to interpretation of the igneous activity and geodynamic evolution of the region in Late Cretaceous era. Emplacement ages of 86.82 ± 0.58 Ma for the Oyman granitoid and 82.0 ± 2.3 Ma for the Arpakoy granitoid according to laser ablation ICP-MS U–Pb zircon dating. The Arpakoy granitoid are gabbro diorite, diorite and granite, whereas the Oyman granitoid are tonalite and granite in composition. They show metaluminous-peraluminous transitional (ASI = 0.79–1.20) low to medium-K calc-alkaline features. The rock samples from granitoids are characterized by enrichment in large ion lithophile elements (LILE) and high field strength elements (HFSE) depletion with concave-upward shapes (LaN/LuN = 1.88 to 6.04). The crystallization temperatures are 648 °C–913 °C and the pressure values are 0.2–3.0 kbar, which indicates emplacement depth of the studied granitoids varying from ∼1 to 9 km correspond to shallow crustal depths. They show considerable variations in eNd(i) (−4.02 to 1.50) and 87Sr/86Sr(i) (0.70478–0.70689). The 206Pb/204Pb ratios are between 17.97 and 18.65, and δ18O are varying from +5.4 to +9.3‰. The parental magma of the Arpakoy and Oyman granitoids originated from a melt of the enriched lithospheric mantle and the fractional crystallization and lesser assimilation processes has important role on the evolution of magmas in the shallow crustal levels.

中文翻译：

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晚白垩世 I 型花岗岩在弧形环境中的 U-Pb 锆石年龄和岩石成因，Eastern Pontides，土耳其东北部

摘要 东桥造山带 (EPOB) 作为保存完好的古老岩浆弧，位于萨卡里亚带东部，对于正确重建该地区的地球动力学演化具有关键意义。该地区被认为是高山-喜马拉雅带的重要组成部分，由许多晚白垩世的花岗岩组成。本文介绍了 EPOB 北部 Arpakoy 和 Oyman 花岗岩的新矿物化学、大块岩石岩石化学、U-Pb 年代学以及放射成因和稳定同位素地球化学数据，以解释该地区晚晚期的火成岩活动和地球动力学演化。白垩纪。根据激光烧蚀 ICP-MS U-Pb 锆石测年，Oyman 花岗岩的侵位年龄为 86.82 ± 0.58 Ma，Arpakoy 花岗岩的侵位年龄为 82.0 ± 2.3 Ma。Arpakoy 花岗岩是辉长闪长岩、闪长岩和花岗岩，而 Oyman 花岗岩是辉长岩和花岗岩。它们显示出金属铝-过铝过渡 (ASI = 0.79–1.20) 低至中 K 钙碱性特征。花岗岩样品的特征是大离子亲石元素（LILE）富集和高场强元素（HFSE）耗尽，呈凹上向上的形状（LaN/LuN = 1.88 to 6.04）。结晶温度为 648 °C–913 °C，压力值为 0.2–3.0 kbar，这表明所研究花岗岩的侵位深度为 ∼1 至 9 km，对应于浅地壳深度。它们在 eNd(i)（-4.02 至 1.50）和 87Sr/86Sr(i) (0.70478–0.70689) 方面表现出相当大的变化。206Pb/204Pb 比值介于 17.97 和 18.65 之间，δ18O 从 +5.4 到 +9.3‰变化。