Abstract The Pavlovsk complex granitoid plutons and associated gabbro-diorites are confined to the East Sarmatian Orogen (ESO) that compose the western part of the junction between the Sarmatian and Volgo-Uralia segments of the East-European Craton. The plutons form the largest batholiths with an area of up to 2000 km2 and a total length of more than 330 km. The conditions for their emplacement and crystallization, sources of melts and tectonic position remain debatable. Here we present new results on geochronological, geochemical and isotope- data on the Pavlovsk complex granitoids and associated gabbro-diorites and discuss these in conjunction with previously published data. The geochemical characteristics, such as elevated concentrations of Mg, K, Sr and Ba (usually > 500 ppm), ratios (La/Yb)N (25–73) and Sr/Y (23–223) in the absence of Eu anomalies of the Pavlovsk-type plutons are similar to high-Mg Archean granites. Zircon U-Pb data indicate the formation of the granitoids and associated gabbro-diorites during a short span at 2060–2075 Ma. The magma emplacement occurred in a transitional environment (from late-collisional to post-collisional) after the collision of two crustal segments (Sarmatia and Volgo-Uralia). We identify a significant ancient Archean continental crust in the magma source for the northern plutons and leucogranites including the presence of Archean zircon cores and Archean model TNd (DM) ages. All the plutons are dominated by a mixed magma source generated through the interaction of juvenile lower crustal and enriched mantle components. The Nd isotopic composition of the studied plutons is significantly more radiogenic as compared with the host Archean rocks (eNd (T) from +0.3 to −4.2). Our geochemical data suggest that that the mantle source of the gabbro-diorites and granitoids were modified (metasomatized) by subduction-related processes. The contrasting geochemical and isotopic features of the granitoids in the ESO as compared to the Pavlovsk granitoids suggest different sources for the parent melts.

中文翻译：

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Don terrane, East-Sarmatian Orogen 的古元古代花岗岩类：年龄、岩浆来源和构造意义

摘要 巴甫洛夫斯克复合花岗岩体和伴生辉长闪长岩仅限于东萨尔马提亚造山带（ESO），该造山带构成东欧克拉通萨尔马提亚和伏尔加-乌拉利亚段交界处的西部。这些岩体形成了最大的基岩，面积达 2000 平方公里，总长度超过 330 公里。它们的侵位和结晶条件、熔体来源和构造位置仍然存在争议。在这里，我们展示了关于巴甫洛夫斯克复合花岗岩和相关辉长闪长岩的年代学、地球化学和同位素数据的新结果，并结合以前发表的数据进行讨论。地球化学特征，例如 Mg、K、Sr 和 Ba 浓度升高（通常 > 500 ppm），在没有 Pavlovsk 型岩体的 Eu 异常的情况下，(La/Yb)N (25-73) 和 Sr/Y (23-223) 的比率与高镁太古代花岗岩相似。锆石 U-Pb 数据表明花岗岩和相关辉长闪长岩在 2060-2075 Ma 的短时间内形成。岩浆侵位发生在两个地壳段（Sarmatia 和Volgo-Uralia）碰撞后的过渡环境（从晚期碰撞到后碰撞）。我们在北部岩体和白质花岗岩的岩浆源中确定了一个重要的古代太古代大陆地壳，包括太古代锆石核的存在和太古代模型 TNd (DM) 年龄。所有的岩体都以年轻的下地壳成分和富集地幔成分相互作用产生的混合岩浆源为主。与宿主太古代岩石相比，所研究的岩体的 Nd 同位素组成明显更具放射成因（eNd (T) 从 +0.3 到 -4.2）。我们的地球化学数据表明辉长闪长岩和花岗岩的地幔来源被俯冲相关过程改造（交代）。与 Pavlovsk 花岗岩相比，ESO 中花岗岩的地球化学和同位素特征的对比表明母体熔体的来源不同。