赵小明, 胡在龙, 裴毅俊, 袁海军, 邱啸飞, 吴年文, 姚华舟. 海南三亚中元古代变质砾岩的发现及其对Columbia超大陆裂解的指示[J]. 地质通报, 2021, 40(6): 880-888.
    引用本文: 赵小明, 胡在龙, 裴毅俊, 袁海军, 邱啸飞, 吴年文, 姚华舟. 海南三亚中元古代变质砾岩的发现及其对Columbia超大陆裂解的指示[J]. 地质通报, 2021, 40(6): 880-888.
    ZHAO Xiaoming, HU Zailong, PEI Yijun, YUAN Haijun, QIU Xiaofei, WU Nianwen, YAO Huazhou. Recognition of metamorphic conglomerate in the Sanya area of Hainan Island and its indicator to breakup of the Columbia supercontinent[J]. Geological Bulletin of China, 2021, 40(6): 880-888.
    Citation: ZHAO Xiaoming, HU Zailong, PEI Yijun, YUAN Haijun, QIU Xiaofei, WU Nianwen, YAO Huazhou. Recognition of metamorphic conglomerate in the Sanya area of Hainan Island and its indicator to breakup of the Columbia supercontinent[J]. Geological Bulletin of China, 2021, 40(6): 880-888.

    海南三亚中元古代变质砾岩的发现及其对Columbia超大陆裂解的指示

    Recognition of metamorphic conglomerate in the Sanya area of Hainan Island and its indicator to breakup of the Columbia supercontinent

    • 摘要: 海南岛中元古代沉积记录对于探讨华南陆块早期大陆演化过程起关键作用。对海南三亚三郎岭地区奥陶系干沟村组砂岩-板岩组合中的变砾岩形成时代进行了重新厘定。碎屑锆石U-Pb同位素年龄分析结果表明,65颗锆石207Pb/206U年龄范围为2691~1350 Ma,且分成2691~2444 Ma、1838~1632 Ma、1540~1350 Ma三组,形成约1699 Ma、约1440 Ma 2个主要峰值和约2461 Ma的1个次要峰值。基于最年轻锆石年龄为1350 Ma,且没有出现海南岛常见的1250~1100 Ma和1000~900 Ma年龄记录,将该套变质砾岩沉积时代限定在1350~1250 Ma,而并非前人划属的奥陶纪,这是海南岛首次发现中元古代的砾岩建造。该套变砾岩砾石成分成熟度高、结构成熟度中等,表现为裂谷盆地高密度的碎屑流沉积特征,是研究区Columbia超大陆裂解晚期的沉积响应。变质砾岩与劳伦大陆西部的Belt-Purcell超群下部沉积地层具有相似的碎屑锆石年龄组成和年龄谱特征,暗示中元古代哥伦比亚超大陆中,海南岛与劳伦西部靠近。

       

      Abstract: Mesoproterozoic sedimentary records in the Hainan Island are significant for discussing the continental crust evolution of the South China Massif.In our studies, the formation age of metamorphic conglomerate in the sandstone-slate combination of the Ordovician Gangoucun Formation in the Sanlangling area of the Sanya city, Hainan Island, were redetermined.Total 65 detrital zircons from the conglomerate were measured for U-Pb dating.The U-Pb ages of the zircons range from 2691 Ma to 1350 Ma, and are clustered at 2691~2444 Ma, 1838~1632 Ma, and 1540~1350 Ma, with two main peaks at ~1699 Ma and ~1440 Ma and a subordinary peak at ~2461 Ma.Based on the youngest detrital zircon age of ~1350 Ma for the conglomerate, without 1250~1100 Ma and 1000~900 Ma age records which are common in the Hainan Island, it is suggested that the metamorphic conglomerate was deposited at 1350~1250 Ma.This is the first time that a Mesoproterozoic conglomerate formation has been recognized on Hainan Island, rather than the Ordovician sedimentary rocks previously classified.The metamorphic conglomerates have high compositional maturity and middle texture maturity, which are consistent with the sedimentary features of high-density debris flow in the rift basin.They might represent the sedimentary response to the final breakup of the Columbia supercontinent in the Hainan Island.

       

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