Abstract The Pailin Crystalline Complex, which consists of amphibolites, metagabbros, and felsic igneous rocks, is located in western Cambodia. We used the geochemistry of the amphibolites and the zircon U Pb ages of felsic igneous rocks to constrain the origin of the Pailin Crystalline Complex and to gain insights into the tectonic framework of Southeast Asia. Geochemical analyses indicate that the amphibolites are normal (N-type) mid-ocean ridge basalts, similar to the Sa Kaeo Back-arc Basin basalts of southeastern Thailand. The zircon U Pb ages are 283 ± 2 Ma (anorthosite dike), 280 ± 2 Ma (aplite dike), and 275 ± 2 Ma (plagiogranite). The geochemistry and detrital zircon U Pb ages of sandstones adjacent to the Pailin Crystalline Complex suggest that they are sediments that filled the Sa Kaeo Back-arc Basin during the Triassic. We infer that the Pailin Crystalline Complex is part of a dismembered ophiolite related to the back-arc basin, and that the igneous rocks formed during the Early Permian. Most of the metamorphism occurred during continental collision in Southeast Asia. However, the amphibolites of the Pailin Crystalline Complex also experienced ocean-floor metamorphism at a back-arc spreading center, in a tectonic setting similar to that of the mafic metamorphic rocks of the Nan Back-arc Basin, northern Thailand. We conclude that the Pailin Crystalline Complex is the southernmost extension of a back-arc basin related to subduction of Paleo-Tethys oceanic crust and the Sukhothai Arc.

中文翻译：

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柬埔寨西部拜林晶体杂岩成因及古特提斯洋弧后盆地发育

摘要 拜林晶体杂岩体位于柬埔寨西部，由角闪岩、变长岩和长英质火成岩组成。我们使用角闪岩的地球化学和长英质火成岩的锆石 U Pb 年龄来限制拜林晶体杂岩的起源，并深入了解东南亚的构造框架。地球化学分析表明角闪岩是正常的（N 型）洋中脊玄武岩，类似于泰国东南部的沙缴弧后盆地玄武岩。锆石 U Pb 年龄为 283 ± 2 Ma（斜长岩脉）、280 ± 2 Ma（斜长岩脉）和 275 ± 2 Ma（斜长花岗岩）。拜林结晶杂岩体附近砂岩的地球化学和碎屑锆石 U Pb 年龄表明，它们是三叠纪期间充满沙缴弧后盆地的沉积物。我们推断拜林晶体杂岩是与弧后盆地相关的已肢解蛇绿岩的一部分，火成岩形成于早二叠世。大多数变质作用发生在东南亚大陆碰撞期间。然而，拜林晶体杂岩的角闪岩也在弧后扩张中心经历了海底变质作用，其构造环境类似于泰国北部南弧后盆地的基性变质岩。我们得出结论，拜林晶体杂岩是与古特提斯洋壳和素可泰岛弧俯冲有关的弧后盆地的最南端延伸。大多数变质作用发生在东南亚大陆碰撞期间。然而，拜林晶体杂岩的角闪岩也在弧后扩张中心经历了海底变质作用，其构造环境类似于泰国北部南弧后盆地的基性变质岩。我们得出结论，拜林晶体杂岩是与古特提斯洋壳和素可泰岛弧俯冲有关的弧后盆地的最南端延伸。大多数变质作用发生在东南亚大陆碰撞期间。然而，拜林晶体杂岩的角闪岩也在弧后扩张中心经历了海底变质作用，其构造环境类似于泰国北部南弧后盆地的基性变质岩。我们得出结论，拜林晶体杂岩是与古特提斯洋壳和素可泰岛弧俯冲有关的弧后盆地的最南端延伸。