Abstract The Anatolide-Tauride block in the Tethyan belt represented passive northern continental margin of Gondwana throughout Paleozoic time. In this paper, we report on a relatively large amphibolite-facies metaquartz-syenite to -granite complex (~ 60 km2) in the Eastern Anatolia, the easternmost part of the Anatolide-Tauride block. Igneous textures in the metaintrusive complex are variably preserved. The preserved igneous minerals include mesoperthite + quartz ± aegirine-augite ± sodic amphibole ± calcic amphibole ± biotite and ± allanite. Mesoperthite is the sole feldspar in well-preserved igneous textures, suggesting the hypersolvus nature of the original quartz syenite to granite. In the well-recrystallized samples, mesoperthite is partially or totally replaced by discrete grains of plagioclase and K-feldspar. U Pb dating on igneous zircons from three samples yielded Silurian igneous crystallization ages (430–440 Ma). All rock types have typical geochemical characteristics of A-type syenite to granite with relatively high abundances of FeO*, Na2O, K2O, Nb, Ga, Zr, Ce, and Zn, and low abundances of MgO, CaO and Sr, resulting in high ratios of Fe/Mg and Ga/Al. Geochemical features such as (i) the absence of negative Nb Ta anomalies on multielement variation diagrams, (ii) the enrichment of Nb and Ce relative to Y, and (iii) Y/Nb, Yb/Ta and Ce/Nb ratios similar to those in ocean island basalts point to A1-type syenite and granite which are thought to be differentiates of ocean island basaltic magmas. Estimated magma temperatures based on zirconium saturation range from 850 to 990 °C, indicating derivation of the original quartz syenite and granite from high-temperature juvenile magmas. Initial eHf values of the igneous zircons from two samples are 2.59 ± 1.14 and 2.30 ± 1.29, while δ18O values of the zircons range from 5.41 to 7.32‰ with a median of 6.50 ± 0.48‰. All these isotopic characteristics suggest that the quartz syenite to granite were derived from high-temperature mantle magmas with insignificant crustal assimilation. The Late Ordovician-Silurian A-type igneous rocks in the northern part of the Anatolide-Tauride block were probably related to a rifting event at the northern margin of Gondwana, leading to the opening of the Paleo-Tethys. This interpretation is also supported from (i) regional geological features of the Early Paleozoic sedimentary successions suggestive of extensional setting during the Late Ordovician-Silurian, (ii) the presence of Silurian anorogenic magmatism in continental blocks detached from Gondwana during Early Paleozoic time, and (iii) the presence of Silurian deep sea sedimentary blocks in Paleo-Tethyan accretionary complexes.

中文翻译：

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安纳托利亚东部志留系 A 型变质石英-正长岩至花岗岩：冈瓦纳北缘晚奥陶世-志留系裂谷的意义

摘要 特提斯带中的 Anatolide-Tauride 地块代表了整个古生代冈瓦纳大陆被动的北部大陆边缘。在本文中，我们报道了位于 Anatolia 东部、Anatolide-Tauride 区块最东端的相对较大的角闪岩相变质石英-正长岩至花岗岩复合体（约 60 平方公里）。亚侵入复合体中的火成岩质地不同程度地保留下来。保存下来的火成岩矿物包括中钙辉石 + 石英 ± 绿辉石 ± 钠闪石 ± 钙闪石 ± 黑云母和 ± 褐云母。中钙长石是保存完好的火成岩结构中唯一的长石，表明原始石英正长岩到花岗岩的超溶解性质。在再结晶良好的样品中，中钙长石部分或全部被斜长石和钾长石的离散颗粒取代。对来自三个样品的火成岩锆石进行 U Pb 测年得出志留纪火成岩结晶年龄（430-440 Ma）。所有岩石类型均具有典型的 A 型正长岩至花岗岩地球化学特征，FeO*、Na2O、K2O、Nb、Ga、Zr、Ce 和 Zn 丰度较高，MgO、CaO 和 Sr 丰度较低，导致高Fe/Mg 和 Ga/Al 的比例。地球化学特征，例如 (i) 在多元素变化图上不存在负 Nb Ta 异常，(ii) Nb 和 Ce 相对于 Y 的富集，以及 (iii) Y/Nb、Yb/Ta 和 Ce/Nb 比率类似于海岛玄武岩中的A1型正长岩和花岗岩被认为是海岛玄武岩岩浆的区别。基于锆饱和度的估计岩浆温度范围为 850 至 990 °C，表明原始石英正长岩和花岗岩来自高温幼年岩浆。两个样品的火成岩锆石的初始 eHf 值为 2.59±1.14 和 2.30±1.29，而锆石的 δ18O 值范围为 5.41 至 7.32‰，中值为 6.50±0.48‰。所有这些同位素特征表明，石英正长岩到花岗岩来源于高温地幔岩浆，地壳同化作用不明显。Anatolide-Tauride 地块北部晚奥陶世-志留纪A 型火成岩可能与冈瓦纳北缘裂谷事件有关，导致古特提斯洋的张开。