阿里根刀若地区花岗岩地球化学特征及其地质意义

Geochemical characteristics and geological significance of granite in the Aligendaoruo area

阿里根刀若地区位于柴达木盆地北缘东段,该区域分布有大量的中晚泥盆世花岗岩。为揭示阿里根刀若地区地质背景、花岗岩成因及地质构造特征,对该地区花岗岩开展了岩石矿物学、主微量元素及稀土元素地球化学特征研究。结果表明:阿里根刀若地区花岗岩具有高硅高钾富铝的特点;Nb、Sr、P、Ti高场强元素相对亏损,Th、Ba、K大离子亲石元素相对富集;轻稀土元素富集,重稀土元素相对亏损,球粒陨石标准化配分曲线呈明显的右倾“海鸥”型,具有明显的Eu负异常;该地区花岗岩主要为过铝质钙碱性Ⅰ型花岗岩,少部分为高硅高钾富铝A型花岗岩。研究认为中晚泥盆世花岗岩形成于陆内伸展阶段后造山构造背景,研究认识对于理解该地区花岗岩成因及稀贵金属找矿具有重要的地质意义。

Aligendaoruo area is located in the eastern part of the northern margin of Qaidam basin with a large number of Middle and Late Devonian granite distributed.The petrological and minera-logical characteristics,major and trace elements as well as geochemical characteristics of rare earth elements in the area are explored to reveal the geological background,granite petrogenesis and geo-logical structure characteristics of the area.The results show that the granite in the area is characte-rized by high silicon,high potassium,rich aluminum and rich sodium.Nb,Sr,P and Ti high field strength elements are relatively deficient,while Th,Ba and K large ion lithophile elements are rela-tively enriched.The area is rich in light rare earth elements,while heavy rare earth elements are rela-tively depleted.The standardized distribution curve of chondrite shows an obvious right-leaning"seagull"type,with obvious negative Eu anomaly.The granite in the area is mainly peraluminous calc-alkaline I-type granite,with a small portion being high potassium,high silicon and aluminum-rich A-type granite.The research suggests that the Middle and Late Devonian granite was formed in the post-orogenic tectonic setting of intracontinental extension stage,which is of great geological sig-nificance for understanding the petrogenesis of granite and the prospecting direction of rare metals in the area.