阿拉善右旗库和乌拉石英闪长岩体地球化学特征及其地质意义

阿拉善右旗库和乌拉石英闪长岩体位于塔里木—华北古陆块与西伯利亚古陆块之间的古生代褶皱带,为探讨其独特的地质意义,本文通过对库和乌拉石英闪长岩体的常量、微量和稀土元素成分分析和综合研究,系统讨论了岩体的岩石地球化学特征、岩体的形成时代及大地构造环境等地质问题。研究表明库和乌拉石英闪长岩属于钙碱性岩,岩体40 Ar-39 Ar同位素测年结果为278.0±2.0Ma,形成时代为早二叠世。稀土元素球粒陨石标准化配分曲线为轻稀土略富集型,LREE/HREE为6.83～6.92,(La/Yb)N为7.23～7.29,δEu=0.93～0.98,δCe=0.90～0.91;大离子亲石元素(Ba、Sr)和不相容元素(Zr、Hf)明显的富集,与碰撞造山环境有关的钙碱性岩石相似。研究认为库和乌拉石英闪长岩体是在板块碰撞条件下形成于造山带的深源岩浆演化产物,具备形成浆控型铜金矿的地质地球化学条件。

Geochemical Characteristics of Quartz-Diorite in Kuhewula Right-Banner Alxa and its Geological Significance

The Alxa Right-banner Kuhewula quartz-diorite locates in the Palaeozoic fold belt between Tarim-northern China and Siberia ancient lands.In order to investigate the geological significance,this paper studied the rock geochemical characteristics,formation age,tectonic setting from the analysis of major,trace element,REE content of Kuhewula quartz-diorite.The results showed that the quartz-diorite being the calc-alkaline series and the ages of the quartz-diorite being 278.0±2.0 Ma formed in early Permian period,according to 40Ar-39Ar isotopic dating.Chondrite-normalized REE patterns being LREE slightly richer,LREE/HREE 6.83~6.92,(La/Yb)N 7.23~7.29,δEu 0.93~0.98,and δCe 0.90~0.91.large-ion lithophile elements(Ba、Sr) and incompatible elements(Zr、Hf) being enriched and similar to the calc-alkaline series of active continental margins.The reseach results in the conclusion of Kuhewula quartz diorite body is the product of magma evolution within deep-source of orogenic belt formed in the condition of plate-collision with the geological and geochemical conditions forming magma controlled copper-gold deposit.