内蒙古宝日拉锦乌拉钠闪石花岗岩特征

CHARACTERISTICS OF BAORILAJINWULA RIEBECKITE GRANITE IN INNER MONGOLIA

宝日拉锦乌拉钠闪石花岗岩岩体位于大兴安岭中段东坡,形成于早白垩世晚期或更晚些.钠闪石花岗岩富SiO(2含量为71.63%～77.35%),富碱(ALK=4.94%～9.17%),贫铝、镁、钙.钠闪石花岗岩的稀土元素总量极高,其中钠闪石钾长花岗岩的稀土总量在271.77×10-6～701.77×10-6之间,而钠闪石二长花岗岩中的稀土元素总量在2938×10-6～6933.2×10-6之间.轻、重稀土元素比值在1.63～7.49之间,大部分在2～5之间,稀土配分曲线为略呈右倾的"V"字形,说明轻、重稀土元素的分馏程度较差.δEu值极低,在0.016～0.035之间,说明该岩石的Eu负异常极为明显.研究区出露的钠闪石花岗岩形成于板块内部非造山的相对稳定的构造环境.

The Baorilajinwola riebeckite granite body, located in the eastern flank of the middle section of Daxing＇an Mountains, was formed in the late stage of Early Cretaceous or later. The rock body contains rich SiO2 （71.63% - 77.35%） and alkaline minerals （ALK = 4.94% - 9.17%）, with poor Al, Mg and Ca. The total amount of rare earth elements （ REE） in the riebeckite granite body is high. In the rock body, the ~ REE of riebeckite moyite is 271.77×10^-6 - 701.77×10^-6, and the ∑ REE of monzonitic granite is 2938×10^-6 - 6933.2×10^-6. The ratio of LREE/HREE is from 1.63 to 7.49 （mostly between 2 and 5）. The REE pattern diagram shows V-shaped curves inclining to the right, suggesting that the fractionation between LREE and HREE is not ideal. The 8Eu is quite low （0.016 - 0.035）, showing an evident negative Eu anomaly. The riebeckite granite in the region is formed in anorogenic setting, which is located inside the plate and relatively steady.