新疆西准噶尔晚古生代侵入岩的年龄和构造意义：来自锆石LA-ICPMS定年的证据

摘要

Voluminous Late Paleozoic plutons distributed throughout the West Junggar region provide critical information for the Phanerozoic crustal growth. On the basis of new zircon U-Pb dating on seven plutons in the Northern West Junggar region, in association with the previous zircon U-Pb ages, the plutons can be divided into two groups:Early Carboniferous (ca. 346 to 321 Ma), Late Carboniferous-Early Permian (ca. 316 to 281 Ma). The Early Carboniferous plutons mainly consist of I-type granites and only occur in Zharma-Saur volcanic arc, and may be related to the southward subduction of the Irtysh-Zaysan Ocean. Late Carboniferous-Early Permian plutons are widely distributed in the northern and southern parts of the West Junggar region. The plutons composed of A-type granites, Charnockites, adakites, magnesian diorites, which indicate a high-temperature and extensional setting. All these suggest that ridge subduction and slab window formation are likely an important mechanism for the generation of the Late Carboniferous-Early Permian plutons in the West Junggar region.%晚古生代以来，西准噶尔地区出露有一系列的侵入岩，成为了解该地区地壳生长的重要窗口。通过对西准噶尔北部7个晚古生代侵入岩体的LA-ICPMS锆石U-Pb年龄的研究，并结合前人的锆石U-Pb定年结果，将西准噶尔晚古生代的岩浆活动分为两期，一期为早石炭世(346~321 Ma)，另一期为晚石炭-早二叠世(316~281 Ma)。早石炭世的侵入岩主要由I型花岗岩组成，仅出露于西准噶尔北部的扎尔玛-萨吾尔火山弧上。这些侵入岩的产生可能与额尔齐斯-斋桑洋的南向俯冲有关。而晚石炭-早二叠世的侵入岩在西准噶尔南部(316~287 Ma)和北部(303~283 Ma)都广泛分布。这些侵入岩主要由A型花岗岩、紫苏花岗岩、埃达克岩和富镁闪长岩等特殊岩石组成，它们反映了一个高温和张性的背景。洋脊俯冲伴随板片窗的形成可能是西准噶尔晚石炭-早二叠世侵入岩产生的重要机制。