新疆南天山缝合带的形成时限 ——来自阔克萨彦岭花岗岩体的锆石年龄新证据

南天山缝合带位于塔里木克拉通与中天山-伊犁-哈萨克斯坦地块之间,其形成时限对于研究古亚洲洋西南缘的南天山洋最终闭合具有重要的意义.利用LA-ICP-MS锆石U-Pb法对南天山阔克萨彦岭地区的花岗岩体进行测试,结果表明花岗岩体的形成时代为早二叠世(273～283Ma),而且大量早二叠世侵入体同时出现在中天山-伊犁-哈萨克斯坦地块和塔里木克拉通.其中,巴雷公蛇绿岩也被早二叠世侵入体所侵入,限定了南天山缝合带的形成时限应早于早二叠世.研究结果进一步支持南天山洋的最终闭合应发生在300Ma之前.

Timing of the South Tianshan suture zone: New evidence of zircon ages from the granitic plutons in Kokshal area

Timing of the South Tianshan suture zone between the Central Tianshan-Kazakhstan-Yili terrane and the Tarim craton is very important for the final closure of the South Tianshan Ocean, the southwestern part of the paleo-Asain Ocean. Zircon LA-ICP-MS U-Pb dating of the granitic plutons in Kokshal area of the South Tianshan Mountains indicates that these plutons were emplaced during the Early Permian (273~283Ma). Spatially, these Early Permian plutons occur simultaneously in the Kazakhstan-Yili terrane in the north and the Tarim craton in the south, with one of the plutons directly crosscuting the Baleigong ophiolite, implying that the South Tianshan suture zone was formed before the emplacement of the Early Permian plutons. The results obtained by the authors further prove that the South Tianshan Ocean was closed at ~300Ma.