江西三百山盆地粗面岩锆石年代学与地球化学制约

Zircon Chronology and Geochemical Constraints of Trachyte of Sanbaishan Basin in Jiangxi Province

三百山盆地的粗面岩主要出现在盆地东部仰天湖破火山口构造中,粗面岩锆石SHRIMP测年的年龄为141.56±0.96 Ma,应归属于早白垩世。盆地粗面岩具有钾含量高,全碱含量高,稀土元素配分曲线图表现为右倾的轻稀土富集型,Eu负异常不明显或表现为正异常的特征,表明三百山盆地的粗面岩属橄榄玄粗岩系列,具有高压型粗面岩的特征,标志着一个加厚的陆壳存在;岩浆物质来源于由上地壳物质俯冲到深部与地幔的混合而形成的再循环富集地幔,岩石形成的构造环境为"同碰撞"环境,代表挤压至拉张过渡构造环境。

Trachyte in Sanbaishan basin,which have a zircon SHRIMP dating age of 141. 56 ± 0. 96 Ma,belongs to Early Cretaceous. Potassium content and ALK content of Trachyte in Sanbaishan basin are both high,and the Chondrite-normalized REE pattern of it represents a LREE-rich curve with mild negative Eu anomaly or positive Eu anomaly. According to the analyses above,trachyte in Sanbaishan basin show the characters to shoshonite rocks and the high-pressure trachyte,which indicates an thickening continental crust. The source roots in the recycle enrichment mantle which is derivable from the mixing of mantle and up-crust materials that have dived to the deep mantle. The tectonic background of the trachyte in this area is squeeze to pull up a transitional structure environment.