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热带海洋学报

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南沙地块中生代岩浆作用对南海南部陆缘构造亲缘性及古南海扩张机制的制约

苗秀全1, 2, 张运迎1, 2, 颜文1, 2, 3   

  1. 1. 热带海洋环境与岛礁生态全国重点实验室(中国科学院南海海洋研究所), 广东 广州 510301;

    2. 边缘海与大洋地质实验室(中国科学院南海海洋研究所), 广东 广州 510301;

    3. 中国科学院大学, 北京 100049



  • 收稿日期:2026-01-30 修回日期:2026-03-14 接受日期:2026-03-25
  • 通讯作者: 张运迎
  • 基金资助:

    国家重点研发计划(2021YFC3100600; 2024YFF0808200); 国家自然科学基金项目(42541603; 42506052; 42372080)

Mesozoic Magmatism in the Nansha Block: Implications for the Tectonic Affinity of Southern Continental Margin of the South China Sea and the Opening Mechanism of the Proto–South China Sea

MIAO Xiuquan1, 2, ZHANG Yunying1, 2, YAN Wen1, 2, 3   

  1. 1. State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China

    2. Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanography, Chinese Academy of Sciences, Guangzhou 510301, China

    3. University of Chinese Academy of Sciences, Beijing 100049, China



  • Received:2026-01-30 Revised:2026-03-14 Accepted:2026-03-25
  • Supported by:

     National Key R&D Program of China (2021YFC3100600; 2024YFF0808200), National Natural Science Foundation of China (42541603; 42372080; 42506052).

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摘要： 明确南海南部陆缘是否以及何时位于华南板块东南陆缘, 对认识东南亚中–新生代构造演化及区域古地理格局重建具有关键意义。此外, 在南海形成之前, 古南海位于华南板块东南陆缘, 是中生代东南亚构造体系的重要组成部分, 然而其初始扩张时代与动力学机制长期缺乏直接地质约束。本研究以南海南部陆缘南沙地块“南科1井”钻孔岩浆岩为研究对象, 通过系统的年代学、岩石学与地球化学分析, 约束岩浆活动的形成时代、成因及构造背景, 进而探讨南海南部陆缘的构造亲缘性及古南海的形成机制。研究结果表明, “南科1井”记录了三期中生代岩浆作用, 分别为晚三叠世英安岩(约217 Ma)、早侏罗世辉长闪长岩(约177 Ma)和早白垩世辉绿岩(约124 Ma)。华南板块内部亦广泛发育与上述三期岩浆事件在时代和性质上相对应的岩浆作用。结合地球物理及古生物学等证据, 推断在三叠纪时期, 以南沙地块为代表的南海南部陆缘应属于华南板块东南陆缘的一部分。三三期岩浆活动系统记录了华南板块东南陆缘在中生代的连续构造演化过程: 晚三叠世的英安岩表现出典型的A2型花岗岩地球化学特征, 指示其形成于古太平洋板片俯冲主导下的陆内伸展环境; 早侏罗世辉长闪长岩显示明显的陆缘弧玄武岩亲缘性, 反映古太平洋板块俯冲控制下的大陆边缘弧岩浆作用; 早白垩世辉绿岩则表现出弧后盆地玄武岩特征, 形成于古太平洋板片俯冲后撤引发的弧后盆地扩张阶段。此外, “南科1井”早白垩世辉绿岩代表古南海初始扩张阶段的陆缘伸展岩浆活动, 其地球化学特征与同期古南海残留洋壳共同显示弧后盆地玄武岩属性, 表明古南海为早白垩世古太平洋板片俯冲后撤过程中形成的弧后盆地。本研究为重建中生代南海南部陆缘构造格局及东南亚区域构造演化提供了新的关键约束。

关键词: 南科1井, 南海南部陆缘, 古南海, 华南板块, 古太平洋

Abstract: Clarifying the tectonic affinity of the southern continental margin of the South China Sea (SCS) and constraining when it was part of the southeastern continental margin of South China Block (SCB) is critical for reconstructing the Mesozoic–Cenozoic paleogeography of Southeast Asia. Furthermore, prior to the opening of the SCS, the proto–South China Sea (PSCS) is thought to have been located along the southeastern continental margin of the SCB. However, the timing of initial spreading and the geodynamic mechanism responsible for the opening of the PSCS remain poorly constrained. To solve these issues, we conducted geochronological, petrographic, and geochemical analyses on igneous rocks from the Well NK-1 drilled in the Nansha Block of the southern SCS margin in this study. Our results identify three distinct stages of Mesozoic magmatism in the Nansha Block: Late Triassic dacite (~218–217 Ma), Early Jurassic gabbro-diorite (~177 Ma), and Early Cretaceous diabase (~124 Ma). Magmatic events of comparable age and composition are also widely documented within the interior of the SCB. Together with geophysical and paleontological evidence, these findings indicate that the southern SCS margin—represented by the Nansha Block—was part of the southeastern SCB margin at least since the Triassic. These three magmatic episodes collectively record the progressive Mesozoic tectonic evolution along the southeastern SCB margin. The Late Triassic dacites exhibit geochemical characteristics of A2-type granites, implying formation in an intracontinental extensional regime driven by far-field paleo-Pacific subduction. The Early Jurassic gabbro-diorites show geochemical affinities to continental arc basalts, reflecting subduction-related continental arc magmatism associated with the paleo-Pacific plate. The Early Cretaceous diabases display geochemical features typical of back-arc basin basalts, consistent with emplacement during a back-arc extensional stage induced by paleo-Pacific slab rollback. Moreover, the Early Cretaceous diabases from Well NK-1 represent continental-margin extensional magmatism associated with the initial opening of the PSCS. Its geochemical characteristics, together with those of the Early Cretaceous remnants of the PSCS oceanic crust, consistently exhibit features of back-arc basin basalts, indicating that the PSCS developed from a back-arc basin formed by slab rollback of the paleo-Pacific plate during the Early Cretaceous. This study provides insights into reconstructing the Mesozoic tectonic evolution of the southern SCS margin and Southeast Asia.

Key words: Well NK–1, Southern South China Sea, Proto–South China Sea, South China Block, Paleo–Pacific plate