Although Variscan terranes have been documented from the Balkans to the Caucasus, the southeastern portion of the Variscan Belt is not well understood. The Strandja Zone along the border between Bulgaria and Turkey encompasses one such terrane linking the Balkanides and the Pontides. However, the evolution of this terrane, and the Late Carboniferous to Triassic granitoids within it, is poorly resolved. Here we present laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U–Pb zircon ages, coupled with petrography and geochemistry from the Izvorovo Pluton within the Sakar Unit (Strandja Zone). This pluton is composed of variably metamorphosed and deformed granites which yield crystallization ages of c. 251–256 Ma. These ages are older than the previously assumed age of the Izvorovo Pluton based on a postulated genetic relationship between the Izvorovo Pluton and Late Jurassic to Early Cretaceous metamorphism. A better understanding of units across the Strandja Zone can now be achieved, revealing two age groups of plutons within it. An extensive magmatic episode occurred c. 312–295 Ma, and a longer-lived episode between c. 275 and 230 Ma. Intrusions associated with both magmatic events were emplaced into pre-Late Carboniferous basement, and were overprinted by Early Alpine metamorphism and deformation. These two stages of magmatism can likely be attributed to changes in tectonic setting in the Strandja Zone. Such a change in tectonic setting is likely related to the collision between Gondwana-derived terranes and Laurussia, followed by either subduction of the Palaeo-Tethys Ocean beneath Laurussia or rifting in the southern margin of Laurussia, with granitoids forming in different tectonic environments.

中文翻译：

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保加利亚和土耳其斯特兰贾区晚石炭世至三叠世两个阶段的岩浆作用

尽管从巴尔干半岛到高加索地区都有华力斯坎地体的记录，但华力斯坎带的东南部尚不清楚。保加利亚和土耳其边界沿线的 Strandja 区包含一个连接巴尔干半岛和庞蒂斯山脉的地层。然而，这种地体的演化，以及其中的晚石炭世至三叠纪花岗岩，很难解决。在这里，我们展示了激光烧蚀 - 电感耦合等离子体 - 质谱 (LA-ICP-MS) U-Pb 锆石年龄，以及来自 Sakar 单元（Strandja 带）内 Izvorovo Pluton 的岩相学和地球化学。该岩体由变质和变形的花岗岩组成，其结晶年龄为C。251-256 马。这些年龄比先前假设的伊兹沃罗沃冥王星年龄要老，这是基于伊兹沃罗沃冥王星与晚侏罗世至早白垩世变质作用之间假定的遗传关系。现在可以更好地了解 Strandja 带的单元，揭示其中的两个年龄组的岩体。发生了广泛的岩浆事件C。312-295 Ma，并且在C。275 和 230 毫安。与这两个岩浆事件相关的侵入体都进入了晚石炭世的基底，并被早期高山变质作用和变形所覆盖。岩浆活动的这两个阶段很可能归因于 Strandja 带构造环境的变化。这种构造环境的变化可能与冈瓦纳地体与劳鲁斯大陆的碰撞有关，随后是劳鲁斯大陆下方的古特提斯洋俯冲或劳鲁斯南缘的裂谷，在不同的构造环境中形成了花岗岩。