Abstract The West Qinling Orogen (WQO) features widespread Triassic granitic rocks, which are crucial to constrain the tectonic evolution of the WQO. Here, we conducted an integrated petrological, geochronological, geochemical, and Sr-Nd-Hf isotope study on quartz diorites and mafic microgranular enclaves (MMEs) from the Ren’ai and Daerzang plutons, Hezuo area, WQO. The quartz diorites and MMEs have crystallization ages between 244 and 241 Ma. The quartz diorites display intermediate SiO2, high Mg# values (62–66) and evolved S-Nd-Hf isotope compositions, indicating an origin from magma mixing process. The MMEs display mineral compositions similar to those of the host rocks, only with more mafic minerals. The The Ren’ai and Daerzang plutons were part of the early Indosinian magmatic belt mainly distributed in the western and middle parts of the northern WQO. In comparison, late Indosinian magmatic rocks are mainly exposed in the eastern WQO. The asymmetric distribution of Early Mesozoic magmatism in the WQO might have been caused by a specific subduction pattern of the A’nimaque-Mianlue oceanic crust. The western and middle WQO experienced a period of flat or low angle subduction in the early stage, followed by slab rollback of the oceanic crust, which accounted for the flare-up of early Indosinian magmatism in the northern WQO. However, the distribution of late Indosinian magmatism might have been caused by asymmetric crustal delamination in the WQO.

中文翻译：

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西秦岭造山带夏河地区中三叠世高Mg#石英闪长岩的成因及其地球动力学意义

摘要 西秦岭造山带（WQO）具有广泛分布的三叠纪花岗岩，是制约西秦岭造山带构造演化的关键。在这里，我们对来自 WQO 合佐地区仁爱和达尔藏岩体的石英闪长岩和镁铁质微粒包体 (MME) 进行了综合岩石学、地质年代学、地球化学和 Sr-Nd-Hf 同位素研究。石英闪长岩和 MME 的结晶年龄在 244 到 241 Ma 之间。石英闪长岩显示中等 SiO2、高 Mg# 值 (62-66) 和演化的 S-Nd-Hf 同位素组成，表明来自岩浆混合过程。MME 显示出与主岩相似的矿物组成，只是具有更多的镁铁质矿物。仁爱岩体和达尔藏岩体是早印支期岩浆带的一部分，主要分布在西北部西部和中部。相比之下，晚印支期岩浆岩主要出露在 WQO 东部。WQO早期中生代岩浆活动的不对称分布可能是由阿尼玛克-绵略洋壳的特定俯冲模式引起的。WQO 西部和中部早期经历了一段平坦或低角度俯冲，随后洋壳板块回滚，导致 WQO 北部早印支期岩浆活动爆发。然而，晚印支期岩浆活动的分布可能是由 WQO 的不对称地壳分层造成的。WQO早期中生代岩浆活动的不对称分布可能是由阿尼玛克-绵略洋壳的特定俯冲模式引起的。WQO 西部和中部早期经历了一段平坦或低角度俯冲，随后洋壳板块回滚，导致 WQO 北部早印支期岩浆活动爆发。然而，晚印支期岩浆活动的分布可能是由 WQO 的不对称地壳分层造成的。WQO早期中生代岩浆活动的不对称分布可能是由阿尼玛克-绵略洋壳的特定俯冲模式引起的。WQO 西部和中部早期经历了一段平坦或低角度俯冲，随后洋壳板块回滚，导致 WQO 北部早印支期岩浆活动爆发。然而，晚印支期岩浆活动的分布可能是由 WQO 的不对称地壳分层造成的。这解释了 WQO 北部早期印支期岩浆活动的爆发。然而，晚印支期岩浆活动的分布可能是由 WQO 的不对称地壳分层造成的。这解释了 WQO 北部早期印支期岩浆活动的爆发。然而，晚印支期岩浆活动的分布可能是由 WQO 的不对称地壳分层造成的。