福建省永定地区早侏罗世双峰式火山岩及其构造环境

Early Jurassic Bimodal Volcanic Rocks and Their Structure Environment in Yongding County, Fujian Province

摘要永定地区早侏罗世火山岩出露于政和一大埔断裂带西侧,以火山喷发盆地形式产出。前人将其划归晚侏罗世南园组。经本次调研证实,应属早侏罗世双峰式火山岩。其岩石组合为玄武岩(安山岩)-流纹岩组合,岩石系列属亚碱性岩系中的拉斑玄武岩系列。岩石地球化学特征及^(87)Sr/^(86)Sr初始化值表明,其原始岩浆来源于幔壳混源区,形成于陆壳板内拉张环境。

Early Jurassic volcanic rocks in the Yongding area of Fujian Province are exposure to the westernside of the Zhenghe-Dapu Deep Fault and occur as the eruptive basin. They were grouped under theNanyuan Formation of Late Jurassic, and they are now considered to be the bimodal volcanic rocks ofEarly Jurassic after the investigation. Their rock association is basalt (andesite) and rhyolite, and theybelong to tholeiite series. The petrogeochemical characteristics and the. ^(87)Sr/^(86)Sr initial ratio of the volcanicrocks indicate that their original magma was derived from the mantal-crust area and that the formationof the volcanic rocks is in the extensive structure setting within the plate of the continentalcrust.