南祁连察汗鄂博图岭地区下奥陶统吾力沟群火山岩岩石地球化学特征

Geochemical characteristics of volcanic rocks of Wuligou Group of Lower Ordovician in Chahanebotuling area,South Qilian area

研究区内分布一套奥陶系吾力沟群,根据其岩石组合特征分为上、下两个岩段;地球化学数据结果表明,岩石里特曼指数σ>1.8,属于钙碱性系列过铝质岩石;岩石分异程度较高,岩浆结晶分异作用明显;岩性由酸性到基性依次呈亚碱性到碱性系列过渡,且依次呈高钾→低钾、低钠→高钠的演化;轻重稀土比值(∑LREE/∑HREE)位于5.46~5.49之间,轻稀土元素富集,重稀土元素亏损;微量元素Ta、Sr、P、Ti相对亏损,Ba、Pb、Nd相对富集;岩石学和地球化学数据特征表明吾力沟群火山岩属于经典岛弧拉斑玄武岩,构造环境为造山带大陆边缘岛弧环境。

A set of Ordovician Wuligou Group distributed in the research area,According to the characteristics of its rock composition,it is divided into upper and lower rock sections;The geochemical data show that the Rock Liteman Indexσmore than 1.8,Aluminum rocks belonging to the calcium alkaline series;High degree of rock differentiation,Magmatic crystal differentiation is obvious;The transition of lithology from acidic to basic is in turn subalkaline to alkaline series;And in turn,the evolution of high potassium to low potassium,low sodium to high sodium;Light rare earth ratio Between 5.46 and 5.49,Concentration of light rare earth elements,Loss of heavy rare earth elements;Trace elements Ta、Sr、P、Ti Relative losses,Ba、Pb、Nd Relative enrichment;The characteristics of petrology and geochemical data indicate that the volcanic rocks of the Wuligou group belong to the classic island arc spot basalt,The tectonic environment is the island arc environment on the continental margin of orogenic belt.