近日，西北大学孙娇鹏团队在研究昆仑-柴达木大陆弧二叠纪至三叠纪的厚度变化上取得新进展。相关论文于2024年10月28日发表在《地球化学学报》杂志上。

据介绍，确定二叠系—三叠系昆仑—柴达木大陆弧的演化历史，对认识南昆仑洋的俯冲和闭合过程具有重要意义。

本文利用昆仑-柴达木大陆弧内二叠纪-三叠纪钙碱性岩（SiO₂55wt%-68wt%）和深成岩的地球化学数据中的（La/Yb）_N比率，重建了相对地壳厚度的时空变化。结合已有的地质观测资料，研究人员讨论了南昆仑洋俯冲-增生构造和昆仑-柴达木大陆弧的地形演化过程。结果揭示了地壳增厚和减薄的两个阶段。

重建的厚度揭示了昆仑-柴达木大陆弧ca.270-210Ma期间的两次地壳增厚和减薄事件。昆仑-柴达木大陆弧南段比北段厚约7km，ca.270-230Ma期间最大厚度约55km。ca.270和230Ma地壳增厚事件，分别与南昆仑洋板块重新向北俯冲和大洋闭合同时发生。ca.270-240Ma和ca.230-210Ma的地壳减薄事件，可能分别反映了碰撞后伸展过程中大洋板块的板块断裂和岩石圈的塌陷。

附：英文原文

Title: Depicting Permian to Triassic thickness variation of the Kunlun-Qaidam Continental Arc: Implication for tectonic evolution of the South Kunlun Ocean

Author: Wang, Zhigang, Sun, Jiaopeng, Qi, Yukun, He, Weidong, Ye, Kai, Li, Zongli, He, Lei, Zhang, Junxiang, Wang, Teng

Issue&Volume: 2024-10-28

Abstract: Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean. In this paper, we utilize (La/Yb)N ratios collected from a filtered geochemical dataset on Permian to Triassic calc-alkaline rocks (55 wt%–68 wt% SiO₂) and plutonic rocks within the Kunlun-Qaidam Continental Arc to reconstruct the spatiotemporal variation of the relative crustal thickness. Combined with known geologic observations, we discuss the subduction-accretionary tectonics of the South Kunlun Ocean and the topographic evolution of the Kunlun-Qaidam Continental Arc. Two episodes of crustal thickening and thinning were revealed. The reconstructed thickness reveals two crustal thickening and thinning events for the Kunlun-Qaidam Continental Arc from ca. 270 to 210 Ma. The southern sector of the Kunlun-Qaidam Continental Arc is about 7 km thicker than the northern portion, with a maximum thickness of about 55 km at ca. 270 and 230 Ma. The ca. 270 and 230 Ma crustal thickening events coincide with renewed northward subduction of the South Kunlun Ocean plate and ocean closure, respectively, whereas the ca. 270-240 Ma and ca. 230-210 Ma crustal thinning events may reflect slab break-off of the oceanic plate and lithospheric collapse during the post-collision extension, respectively.

DOI: 10.1007/s11631-024-00744-9

Source: https://link.springer.com/article/10.1007/s11631-024-00744-9