海南岛五指山地区早白垩世火山岩地层的厘定

Determination of the early Cretaceous volcanic stratum in Wuzhishan area,Hainan Island

五指山火山岩位于海南岛中部略偏南,为一套中酸性向酸性演化的火山岩系,前期研究对于这套岩石的归属存在不同的认识,将这套岩石时代归为晚侏罗世—早白垩世。本研究对这套火山岩进行了详细剖面测制,该火山岩主要由流纹质熔岩及相应的火山碎屑岩组成,少量为英安质、玄武安山质和粗面安山质火山岩。对英安质角砾岩屑晶屑熔结凝灰岩进行锆石LA-ICP-MS U-Pb测年,结果为(102.3±1.3)Ma,表明该套火山岩形成于早白垩世晚期,经岩性时代对比,将此套火山岩归为岭壳村组。这为海南岛白垩纪火山活动研究提供了重要参考资料。

Wuzhishan volcanic rocks are located at the central Hainan Island.They are a set of intermediate acid to acid volcanic rock series.The previous study has the different understandings on the attribution of this set of volcanic rocks,and the rock age is classified as Late Jurassic to Early Cretaceous.In the study,the profile of the set of volcanic rocks has been surveyed in detail.The volcanic rocks are mainly composed of rhyolite lava and corresponding pyroclastic rocks,with a small amount of dacite,basaltic andesite and trachyandesite volcanic rocks.LA-ICP-MS zircon U-Pb dating age of dacite breccia detritus crystal lava tuff shows a result of(102.3±1.3)Ma,indicating that this set of volcanic rocks is formed in the late Early Cretaceous.For the lithology and age comparison,this set of volcanic rocks is classified as Lingkaicun Formation.This provides the important reference data for the study of Cretaceous volcanic activity in Hainan Island.