闽南沿海兄弟屿印支期花岗岩的发现及其地质意义

Discovery and Its Geological Significance of the Brother Island Indosinian of Granite in the Southern Coast of Fujian Province

对闽南沿海兄弟屿西南部的侵入岩开展了LA-ICP-MS锆石U-Pb年代学及全岩地球化学研究,获得2组锆石^(206)Pb/^(238)U加权平均年龄,其中(241±3.6) Ma为岩体侵入年龄(印支期),(141±5.1) Ma可能为后期热液事件年龄(燕山期)。岩石属高钾钙碱性弱过铝质花岗岩,轻、重稀土分馏程度强烈,具有中强的Eu负异常(δ Eu 0.39~0.45)和富集大离子亲石元素特征,显示S型花岗岩。其构造背景可能与古太平洋板块及滨海断裂带等活动有关,兄弟屿的侵入岩体发现为该地区构造-岩浆演化提供新的时空约束信息。

Conducted Zircon LA-ICP-MS U-Pb chronology and whole rock geochemical research of the intrusive rock whick exposed on southwestern Brother island of in the south coast of Fujian Province,and two sets of zircon weighted average ^(206)pb/^(238)U ages have been obtained,of which(241±3.6)Ma is the intrusion age of the rock body(Indosinian period),and(141±5.1)Ma may be the later hydrothermal event age(Yanshan period).The rock belongs to high potassium calcium alkaline weakly peraluminous granite;The degree of light and heavy rare earth fractionation is strong,with moderate to strong negative Eu anomalies(8Eu:0.39~0.45)and enriched withlargeionlithophileelements,indicating S-type granite.Its tectonic setting may be related to the activities of the ancient Pacific Plate and the coastal fault zone.The discovery of the Indosinian intrusive body in the Brother Island has supplied new space-time constraints to the regional tectonic magmatic evolution.