Abstract The Intra-Pontide suture zone is the northernmost ophiolite suture zone exposed in the Anatolian peninsula. It consists of several variably deformed and metamorphosed tectonic units derived from the Neo-Tethyan Intra-Pontide oceanic (IPO) basin, and its continental margins that are currently represented by the Istanbul-Zonguldak and the Sakarya terranes. Recent data suggests that the IPO was a wide supra-subduction oceanic basin whose closure began in the uppermost Early Jurassic by a north dipping intra-oceanic subduction that divided the IPO into two different oceanic areas, namely IPO1 and IPO2. The Saka Unit is a small tectonic unit exposed in the eastern portion of the Intra-Pontide suture zone in the Central Pontides, which is interpreted as a tectonic melange produced during the intra-oceanic subduction that led to the closure of IPO1. The unit was affected by polyphase deformation and epidote–amphibolite facies metamorphism peak conditions experienced during the uppermost Middle Jurassic. Metamorphic studies and thermodynamic investigations constrain the peak pressure conditions to T ≈ 650–700 °C and P ≈ 0.9–1.3 GPa. These conditions reveal a ‘hot’ and anomalous geothermal gradient (15–22 °C/km) with respect to those of the other ophiolite-bearing units of the Intra-Pontide suture zone involved in the subduction. This anomalous gradient was herein attributed to the thermal pulse produced by the subduction of the IPO1 mid-oceanic ridge. The final re-equilibration occurred under greenschist facies conditions during the Early Cretaceous exhumation, when the oceanic lithosphere of the IPO was completely consumed and the continental collision between the Istanbul-Zonguldak and Sakarya terranes occurred.

中文翻译：

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山脊俯冲在 Saka 单元（土耳其北部中央蓬蒂斯）新特提斯蛇绿岩上的变质印记

摘要 Intra-Pontide缝合带是安纳托利亚半岛出露的最北端蛇绿岩缝合带。它由来自新特提斯邦内大洋 (IPO) 盆地及其大陆边缘的几个变形和变质的构造单元组成，目前以伊斯坦布尔-宗古尔达克地体和萨卡里亚地体为代表。最近的数据表明，IPO 是一个广阔的超俯冲洋盆，其关闭始于侏罗纪早期最上部，被北倾的洋内俯冲划分为两个不同的海洋区域，即 IPO1 和 IPO2。萨卡单元是一个小的构造单元，出露在中央海盆底的海盆内缝合带的东部，这被解释为在导致 IPO1 关闭的大洋内俯冲过程中产生的构造混杂物。该单元受到中侏罗统最上部经历的多相变形和绿帘石-角闪石相变质峰条件的影响。变质研究和热力学研究将峰值压力条件限制在 T ≈ 650–700 °C 和 P ≈ 0.9–1.3 GPa。这些条件表明，相对于参与俯冲的庞德内缝合带的其他含蛇绿岩的单元，这些条件显示了一个“热”和异常的地热梯度（15-22°C/km）。这种异常梯度在这里归因于 IPO1 洋中脊俯冲产生的热脉冲。最终的再平衡发生在早白垩世剥露期间的绿片岩相条件下，