| 鄂尔多斯盆地西南部早白垩世岩浆事件及其地质意义 |
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| 引用本文：陈印,田德强,徐喆,吴兆剑,张羽,张博.2026.鄂尔多斯盆地西南部早白垩世岩浆事件及其地质意义[J].地球学报,47(3):597-612. |
| DOI：10.3975/cagsb.2025.090221 |
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| 基金项目:本文由中广核铀业发展有限公司科技项目(编号: CGNPC-URC-T-2024-12)、天津市自然科学基金项目(编号: 24JCYBJC00410)和科技部科技基础资源调查专项(编号: 2022FY101800)联合资助。 |
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| 中文摘要:鄂尔多斯盆地白垩纪岩浆事件, 对揭示早白垩世区域构造动力学演化机制、探讨岩浆活动与油气成藏及砂岩型铀矿的时空耦合关系具有重要意义。本研究首次在鄂尔多斯盆地西南部下白垩统环河华池组识别出早白垩世侵入岩, 综合开展了岩石学、锆石U-Pb年代学及Hf同位素分析。盆地西南部下白垩统环河华池组发育黑榴斑岩侵入体, 锆石U-Pb加权平均年龄为(126.5±0.9) Ma(MSWD=1.6), 属早白垩世中期岩浆活动。锆石εHf(t)值为–12.32 ~ –4.70, TDM2=1 960~1 501 Ma, 记录了华北克拉通最西缘早白垩世岩浆事件。华北克拉通内早白垩世岩体年龄自太行—吕梁山构造带向东、西两侧呈递减趋势, 反映古太平洋板块西向俯冲与班公湖—怒江洋北东向俯冲共同控制的伸展背景。软流圈上涌诱发岩石圈减薄及古老地壳部分熔融, 形成幔源热驱动型岩浆系统。早白垩世岩浆热效应促进了盆地烃源岩的生排烃过程, 释放的还原性组分参与浅部砂岩型铀矿的氧化-还原界面调控, 但岩浆热液未直接参与铀成矿过程。 |
| 中文关键词:鄂尔多斯盆地 早白垩世岩浆活动 锆石U-Pb定年 Hf同位素 板块俯冲 |
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| Early Cretaceous Magmatic Events in the Southwestern Part of the Ordos Basin and Their Geological Significance |
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| Abstract:Cretaceous magmatic events in the Ordos Basin are crucial for unraveling the regional tectonic dynamic evolution mechanisms of the Early Cretaceous and exploring the spatiotemporal coupling relationships between magmatism, hydrocarbon accumulation, and sandstone-type uranium mineralization. This study identified, for the first time, Early Cretaceous intrusive rocks within the Lower Cretaceous Huanhe-Huachi Formation in the southwestern part of the Ordos Basin. Integrated petrological, zircon U-Pb geochronological, and Hf isotopic analyses were conducted. A melanocratic porphyry intrusive body is identified in the Huanhe-Huachi Formation, yielding a zircon U-Pb weighted mean age of (126.5±0.9) Ma (MSWD=1.6), indicating the middle Early Cretaceous magmatism. Zircon εHf(t) values of –12.32 – –4.70, and TDM2 model ages of 1 960–1 501 Ma indicate that this region records the Early Cretaceous magmatic activity of the westernmost North China Craton. The magmatic ages decrease eastward and westward from the Taihang-Lüliang tectonic belt, reflecting an extensional setting jointly controlled by the westward subduction of the Paleo-Pacific Plate and the northeastward subduction of the Bangong–Nujiang Ocean. Asthenospheric upwelling triggered lithospheric thinning and the partial melting of the ancient crust, forming a mantle heat-driven magmatic system. Magmatic thermal effects promoted hydrocarbon generation and expulsion in deep-source rocks. The released reducing agents participated in redox interface regulation for shallow sandstone type uranium mineralization, although magmatic–hydrothermal fluids did not directly contribute to uranium ore-forming processes. |
| keywords:Ordos Basin Early Cretaceous magmatism zircon U-Pb dating Hf isotopes plate subduction |
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