Evolved Late Mesozoic continental arc: Constraints of detrital zircons from the western East China Sea

The Late Mesozoic subduction of Izanagi slab beneath East Asia formed large-scale intraplate magmatism in SE South China and subduction mélanges outcropped in SW Japan to eastern Taiwan Island, but the accompanying arc remains uncertain. We conducted LA-ICP-MS U–Pb zircon dating and trace element analyses of proximal sandstones from the SW East China Sea to trace a Jurassic to Cretaceous magmatic arc. Newly acquired data reveal that arc magmatism mostly developed in episodes of 150–124 and 124–102 Ma, exhibiting characteristics of low-T, high Th/U, U/Yb, Sc/Yb, Th/Nb, and low Nb/Yb, Nb/Hf ratios. This magmatic arc, combined with the SE South China intraplate and residual subduction mélanges, spatially forms a Late Mesozoic trench–arc–intraplate architecture responding to the Izanagi subduction. Its identified tectonic scenarios mainly include slab strike-slip subduction (200–170 Ma), slab stagnation and intraplate foundering (170–150 Ma), slab rollback and arc-root removal (150–102 Ma), and arc migration (102–86 Ma). Both the western East China Sea and Cathaysia block share a unified Paleoproterozoic basement that formed at ca. 1.85 Ga, and the Cathaysia-based magmatic arc occurred then.东亚下方伊佐奈岐俯冲板片（Izanagi slab）的晚中生代（Late Mesozoic）俯冲作用，在华南东南部形成了大规模板内岩浆作用，并在日本西南部至台湾东部岛出露了俯冲混杂岩（subduction mélanges），但与之伴生的岩浆弧（magmatic arc）仍存在争议。我们对东海西南部的近源砂岩开展了激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）U-Pb锆石定年与微量元素分析，以追溯侏罗纪至白垩纪的岩浆弧演化。新获得的数据显示，弧岩浆作用主要发育于150~124 Ma和124~102 Ma两个期次，具有低温度、高Th/U、U/Yb、Sc/Yb、Th/Nb比值以及低Nb/Yb、Nb/Hf比值的地球化学特征。该岩浆弧结合华南东南部板内岩浆作用与残余俯冲混杂岩，在空间上构成了响应伊佐奈岐俯冲作用的晚中生代沟-弧-板内构造格架。其厘定的构造动力学背景主要包括：板片走滑俯冲（200~170 Ma）、板片停滞与板内塌沉（170~150 Ma）、板片后撤与弧根拆离（150~102 Ma），以及弧迁移（102~86 Ma）。东海西部与华夏地块（Cathaysia block）共享形成于约1.85 Ga的统一古元古代基底，且华夏地块相关的岩浆弧也同期形成。