内蒙古阿巴嘎旗乌和尔楚鲁图地区二长花岗岩地球化学特征及地质意义

GEOCHEMICAL CHARACTERISTICS OF MONZONITIC GRANITES IN WUHERCHULUTU AREA,ABAGA BANNER,INNER MONGOLIA, AND THEIR GEOLOGICAL SIGNIFICANCE

内蒙古阿巴嘎旗乌和尔楚鲁图地区发育的印支期二长花岗岩呈北东向展布,与围岩界限截然,该岩体具有高硅、富碱、低钙、低镁、铁准铝到弱的过铝质的钙碱性A型花岗岩特征,稀土元素呈轻稀土富集、重稀土分布平坦、强负铕异常的右倾型海鸥式模式,微量元素中大离子亲石元素Rb,Th,U,K,Pb明显富集;而Ba,Sr均强烈亏损,高场强元素(HFSE)中P,Ti明显亏损。通过区域地质及岩石地球化学分析,岩体形成于造山后伸展的构造环境,是印支期岩石圈伸展减薄诱发地幔来源的玄武质岩浆底侵使得下地壳部分熔融的产物。

The NE trending Indosinian monzonitic granites showed obvious dividing line with wall rocks in Wuherchulutu area, Inner Mongolia. The intrusions were characteristic of high in sil- icon, alkali, and low in calcium, magnesium iron and metaluminous to weak peraluminous, belong- ing to calc alkaline A-type granite. Rare earth elements showed that they are rich in LREE, flat distributed in HREE, strong negative in Eu and right deviation model like sea gull. Trace elements showed that they are rich in Rb,Th,U,K,Pb,but deficit in Ba, Sr in LILE,clearly deficit in P,Ti in HFSE. Based on the analysis of regional geology and petrogeochemistry,the intrusions formed in the post orogenic extensional stage and resulted from partial melting of crustal materials which basaltic magma underplated from mantle sources in Indosinian.