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现代地质 ›› 2025, Vol. 39 ›› Issue (04): 964-980.DOI: 10.19657/j.geoscience.1000-8527.2024.036

• 矿床学与岩石学 • 上一篇    下一篇

浙江南雁荡山晚白垩世火山岩及地层厘定

潘少军(), 陈小友*(), 张建芳, 曾凡飞, 顾明光, 马俊祥   

  1. 浙江省地质院,浙江 杭州 311200
  • 出版日期:2025-08-10 发布日期:2025-08-27
  • 通信作者: *陈小友,男,高级工程师,1979年出生,主要从事区域地质调查研究工作。Email: 414177270@qq.com
  • 作者简介:潘少军,男,地质工程师,1986年出生,主要从事区域地质调查研究工作。Email:751151749@qq.com
  • 基金资助:
    浙江省级基础性公益性战略性地质工作专项资金项目(〔省资〕2022012);浙江省级基础性公益性战略性地质工作专项资金项目(〔省资〕2025004)

Late Cretaceous Volcanic Rocks and Stratigraphic Delimitation in the Nanyandang Mountain Area, Southeastern Zhejiang

PAN Shaojun(), CHEN Xiaoyou*(), ZHANG Jianfang, ZENG Fanfei, GU Mingguang, MA Junxiang   

  1. Zhejiang Institute ofGeosciences, Hangzhou, Zhejiang 311200, China
  • Published:2025-08-10 Online:2025-08-27

摘要:

浙东南沿海地区是否存在晚白垩世火山岩,以及如何厘定其成岩年龄,一直是该区域地质研究中的难点问题。以南雁荡山地区白云山火山机构为研究对象,开展锆石U-Pb测年工作,获得了8套高精度测年数据,4套火山岩和1套正长斑岩的年龄分布于90.32~98.37 Ma,确认该地区在晚白垩世仍存在强烈的火山活动。对6套晚白垩世火山岩样品开展地球化学特征研究,主量元素呈现高硅、富碱、低铝,贫钙、铁、镁、磷、钛,高分异度等特征;微量及稀土元素呈现出大离子亲石元素Rb、K、Th、U等富集,Co、Ni、Cr等亲铁元素含量低,且贫Ba、Nb、Sr、P、Ti等元素的特征;反映了该套火山岩属于准铝质-过铝质高钾钙碱性岩石,具有高结晶分异演化程度和壳源特征。通过火山岩成因探讨,认为由于太平洋板块的俯冲作用,导致浙江东南部自晚侏罗世以来上地壳挤压-伸展拉张作用一直持续到晚白垩世,造就了南雁荡山地区晚白垩世火山活动。浙江东南区域不断有新的晚白垩世火山岩被发现,且岩性、地球化学组合特征与小雄组并不完全一致,为了更好地“安置”晚白垩世火山岩地层,建议新建“雁荡山群”,并根据岩性组合和地球化学特征在群内建立不同的“组-段”地层单元。

关键词: 晚白垩世, 火山岩, U-Pb测年, 地质意义, 南雁荡山地区, 浙江东南部

Abstract:

This study focuses on the Baiyunshan volcanic edifice in the Nanyandang Mountain area, southeastern Zhejiang. Zircon U-Pb dating was conducted on volcanic rocks and syenite porphyry from the central intrusion of the edifice, yielding 8 sets of high-precision data. Four volcanic rock samples and one syenite porphyry sample yielded ages ranging from 90.32 to 98.37 Ma, confirming intense volcanic activity in the region during the Late Cretaceous.Geochemical analysis of 6 Late Cretaceous volcanic clastic rock samples reveals the following characteristics: major elements are characterized by high silica, high alkali, low aluminum, depletion in Ca, Fe, Mg, P, and Ti, and high differentiation. Trace and rare earth elements show enrichment in large ion lithophile elements (Rb, K, Th, U), depletion in Ba, Nb, Sr, P, and Ti, and low contents of siderophile elements (Co, Ni, Cr). These features indicate that the volcanic rocks belong to quasi-aluminous to peraluminous high-K calc-alkaline series, with high degrees of fractional crystallization and crustal origin.The genesis of the Late Cretaceous volcanic rocks is attributed to the subduction of the Pacific Plate, which sustained upper crustal compression and extensional tectonics in southeastern Zhejiang from the Late Jurassic to the Late Cretaceous, triggering volcanic activity in the Nanyandang Mountain area.Recent discoveries of Late Cretaceous volcanic rocks in southeastern Zhejiang, with expanding outcrops, show lithological and geochemical differences from the Xiaoxiong Formation. To better “accommodate” these volcanic strata, it is proposed to establish a new “Yandang Mountain Group” and subdivide it into “Formation-Member” units based on lithological assemblages and geochemical characteristics.

Key words: Late Cretaceous, volcanic rock, U-Pb dating, geological significance, Nanyandang Mountain area, southeastern Zhejiang

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