江南造山带北缘鄣源基性岩地质-地球化学特征及成因机制

Geological and Geochemical Characteristics and Petrogenesis of the Mafic Rocks from Zhangyuan,Northern Jiangnan Orogen

鄣源基性岩呈北东—南西向分布于皖赣相邻区鄣公山北坡瑶里—鄣源—江潭一带,以构造碎块或碎片形式产于新元古代火山-陆缘细碎屑岩组成的复理石基质中,总体显示构造混杂岩带特征。基性岩残块包括蚀变枕状—块状基性熔岩、辉长岩、辉绿岩等,它们在空间上紧密相伴,形成于新元古代。通过对鄣源基性岩地质及岩石地球化学特征等的分析,认为其形成于低速扩张的陆缘小洋盆扩张脊环境,具初始洋壳基性岩特征。提出鄣源基性岩可能属皖南伏川蛇绿岩西延组成部分。

Zhangyuan mafic rocks of NE-SW trend are distributed along the Yaoli-Zhangyuan-Jiangtan line in the northern slope of Zhanggong Mountain,between Anhui and Jiangxi provinces.They occur as structural shivers and fragments in flysch matrix textured by Neoproterozoic volcano-fine clastic rocks of continental margin,and overall display characteristics of tectonic melange belt.Mafic fragments include altered pillow-block basic lava,gabbro,dolerite,etc,which were concomitant in space since the Neoproterozoic.By analyzing geological and geochemical characteristics of the Zhangyuan mafic rocks,their origin is considered to be in a small,slow expansion oceanic basin spreading ridge of the continental margin environment,with the features of primitive oceanic crust mafic rocks.It is proposed that Zhangyuan mafic rocks belong to westward extension of Fuchuan ophiolite in Southern Anhui province.