内蒙古阿德拉嘎乌拉正长花岗岩锆石U-Pb年龄

阿德拉嘎乌拉正长花岗岩出露于中蒙边界一线，1：20万区域地质调查将其划归于燕山早期侵入岩（Kγ52），1：25万区域地质调查划归于早二叠世碱长花岗岩（P1χγ）.通过单颗粒锆石U-Pb同位素稀释法测定其年龄，206Pb/238U表面年龄加权平均值为273.1±0.4 Ma.结合区域地质资料和前人研究成果分析，该正长花岗岩为早二叠世晚期岩浆活动的产物.岩石具高硅、高钾、过铝、贫铁镁钙的特征，属造山后的I型花岗岩.岩石稀土总量偏低，轻重稀土元素分馏程度不明显，δEu在0.07~0.60之间，铕强烈亏损，稀土元素配分曲线呈“V”字型.

U-Pb AGE OF ZIRCON FROM THE SYENOGRANITE IN ADELAGAWULA,INNER MONGOLIA

The Adelagawula syenogranite occurs in Abaga Qi, Inner Mongolia, near the Sino-Mongolian border. The intrusive rock was assigned to Early-Yanshanian （Krs2） by 1：200 000 regional geological surveyor or Lower Permian as alkali feldspar granite （P1Xr） in 1：250 000 regional geological survey. The U-Pb isotopic dating of the syenogranite shows the age of 273.1±0.4 Ma. Combined with regional geological data and previous research, it is possibly a product of Early Permian magmatism. The syenogranite, with high silica, high potassium, per-aluminum and poor calcium-magnesium-iron, belongs to post-orogenic I-type granite. The REE distribution is in V-shaped pattern, with low total rare earth content, unobvious fraetionation of LREE and HREE, 8Eu values ranging from 0.07 to 0.60 and strongly depleted Eu.