赵小明, 姚华舟, 裴毅俊, 胡在龙, 袁海军, 汪洋, 张仁杰, 何金兰, 龙文国, 吴年文. 海南儋州兰洋地区发现泥盆纪地层:来自锆石U-Pb年龄的证据[J]. 地质通报, 2020, 39(6): 818-826.
    引用本文: 赵小明, 姚华舟, 裴毅俊, 胡在龙, 袁海军, 汪洋, 张仁杰, 何金兰, 龙文国, 吴年文. 海南儋州兰洋地区发现泥盆纪地层:来自锆石U-Pb年龄的证据[J]. 地质通报, 2020, 39(6): 818-826.
    ZHAO Xiaoming, YAO Huazhou, PEI Yijun, HU Zailong, YUN Haijun, WANG Yang, ZHANG Renjie, HE Jinlan, LONG Wenguo, WU Nianwen. The discovery of Devonian strata in Lanyang area, Danzhou, Hainan Province: Evidence from the zircon U-Pb ages[J]. Geological Bulletin of China, 2020, 39(6): 818-826.
    Citation: ZHAO Xiaoming, YAO Huazhou, PEI Yijun, HU Zailong, YUN Haijun, WANG Yang, ZHANG Renjie, HE Jinlan, LONG Wenguo, WU Nianwen. The discovery of Devonian strata in Lanyang area, Danzhou, Hainan Province: Evidence from the zircon U-Pb ages[J]. Geological Bulletin of China, 2020, 39(6): 818-826.

    海南儋州兰洋地区发现泥盆纪地层:来自锆石U-Pb年龄的证据

    The discovery of Devonian strata in Lanyang area, Danzhou, Hainan Province: Evidence from the zircon U-Pb ages

    • 摘要: 在海南岛中部儋州兰洋镇上番开村附近,发育一套灰绿色变细砂岩、变粉砂岩与深灰色板岩互层的岩石组合,其整合于灰色变细砂岩夹浅灰色中厚层状结晶灰岩或白云质灰岩组合的地层之上,伏于灰黑色炭质板岩、千枚岩与灰色变细砂岩互层,夹薄层硅质岩的地层之下。前人将该套岩石组合划归石炭纪青天峡组。本次在该组合下部新发现了2层沉凝灰岩夹层,对该凝灰岩进行LA-ICP-MS锆石U-Pb年龄测试,60颗锆石206Pb/238U年龄分成4组,其中年龄最小的一组为349~375 Ma,年龄加权平均值为365±3 Ma,代表了火山喷发的时限,也指示地层的沉积时代为晚泥盆世晚期,这是海南岛首次报道的泥盆系绝对年龄。结合在相邻的上番开村青天峡组结晶灰岩中新采获的泥盆纪弗拉期竹节石Polycylindrites鉴定结果,可以确定海南岛存在中晚泥盆世沉积。据此对海南岛中北部晚古生代地层序列进行了重新厘定,为研究古特提斯洋东延及构造演化等问题提供了新的思路和证据。

       

      Abstract: The interbedded rock assemblage of grayish green metamorphic fine-grained sandstone, metasiltstone and dark gray slate is developed near Shangfankai Village, Lanyang Town, Danzhou City in the middle of Hainan Island.This rock assemblage overlies the gray metamorphic fine-grained sandstone intercalated with light gray medium-thick bedded crystalline limestone and dolomitic limestone, and underlies the interbedded strata of grayish-black carbonaceous slate, phyllite, and gray metamorphic fine-grained sandstone intercalated with thin bedded chert.Previously, this rock association was classified as Carboniferous Qingtianxia Formation.In this study, two sedimentary tuff beds were discovered in the lower part of this rock association.According to the zircon U-Pb age dating by LA-ICP-MS, 60 zircon of 206Pb /238U age are divided into four groups.The youngest group is 349~375 Ma, and the weighted average age of 365±3 Ma represents the time of the eruption.Therefore, the strata should be deposited in the Late Devonian.This is the first absolute age of Devonian on Hainan island.The tentaculitoid Polycylindrites, obtained in the crystalline limestone of Qingtianxia Formation near Shangfankai Village, indicate that the Middle-Late Devonian deposition existed in the Hainan Island.The stratigraphic sequence of the Late Paleozoic in the northern part of central Hainan Island was reclassified, which provides new ideas and evidence for the study of eastward extension of the Paleo-Tethys Ocean and tectonic evolution.

       

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