小兴安岭二龙山林场堆晶辉长岩地球化学特征及构造环境

Geochemical characteristics and tectonic setting of cumulate gabbro in Erlongshan Tree Farm in Xiaoxing'anling

小兴安岭北部二龙山林场辉长岩的主量、微量和稀土元素的测试分析结果显示:二龙山辉长岩为钙碱性系列、偏铝质岩石;δEu正异常,Sr元素含量富集明显,具有堆晶辉长岩特征;Rb/Sr、Nb/Ta、LILE/HFSE、Th/Ta、Nb/U和Nb/La比值特征均显示,辉长岩岩浆来自受到俯冲流体交代的地幔源区。Nb/Zr、Th/Nb、Th/Ta和Ta/Hf比值特征及对Th/Hf-Ta/Hf构造环境判别图解投点表明,二龙山辉长岩形成于陆内拉张环境。

The major,trace and REE element testings of the gabbro in Erlongshan Tree Farm in northern Xiaoxing＇anling showed that： the gabbro in the Farm belonged to calc-alkaline series and metaluminous rocks with δEu positive anomaly,and Sr element enriched obviously with the characteristics of cumulate gabbro.The characteristics of Rb/Sr,Nb/Ta,LILE/HFSE,Th/Ta,Nb/U and Nb/La ratios showed that the gabbro magma came from the mantle source metasomatized by subduction fluid.The characteristics of Nb/Zr,Th/Nb,Th/Ta and Ta/Hf ratios and the Th/Hf-Ta/Hf tectonic setting discrimination diagram showed that the gabbro in Erlongshan formed in continental extension environment.