北山地区碱滩山东早石炭世花岗闪长岩岩石地球化学及年代学特征

研究表明：碱滩山东花岗闪长岩LA-ICP-MS锆石U-Pb年龄为323.6±3.2 Ma,时代为早石炭世,岩石样品SiO₂含量介于66.37×10^_-2～69.44×10^_-2之间,具富钠(Na₂O＞K₂O),弱过铝(铝饱和指数(A/CNK)介于1～1.1之间)的特征,属弱过铝钙碱性岩石系列；岩石球粒陨石标准化稀土配分曲线呈右倾斜曲线,斜率较大,属轻稀土富集型；微量元素蛛网图表明岩石明显富集Rb、Ba、Th、U、K等大离子亲石元素,亏损Nb、P、Ti等高场强元素。综合区域背景分析表明：碱滩山东花岗闪长岩具有岛弧花岗岩地球化学特征,在R1-R2图解中落入碰撞前花岗岩区,其与研究区广泛分布的晚石炭世早期石英闪长岩、花岗闪长岩、二长花岗岩、奥长花岗岩等共同构成了类似于TTG岩石组合的特征,暗示了研究区在石炭世可能处于大陆边缘弧的构造环境。

Petrogeochemistry of late permian calc-alkaline intrusive rocks in Tamusu erea of alxa and its significances

The results show that the LA-ICP-MS zircon U-Pb age of the granodiorite to the east of Jiantan mountain is 323.6±3.2 Ma, and the age is early Carboniferous; the SiO₂ content of the granodiorite is between 66.37×10^_-2-69.44×10^_-2, with the characteristics of rich sodium(Na₂O>K₂O), weak peraluminium(A/CNK) between 1-1.1), belonging to the weak peraluminium calc alkaline rock series; The curves map the standardized rare earth distribution of chondrite shows a right inclined curve with a large slope, which belongs to the light rare earth enrichment type. The trace element cobweb map shows that the rock is obviously enriched in Rb, Ba, Th, U, K and other large ion lithophile elements, and obviously depleted in Nb, P, Ti and other high field strength elements. Comprehensive regional background analysis: the granodiorite of the east of Jiantan mountain has the geochemical characteristics of island arc granite, which falls into the pre-collisional granite area in the R₁-R₂ diagram, and together with the early Late Carboniferous quartz diorite, granodiorite, monzogranite and trondhjemite widely distributed in the study area, it has the characteristics similar to TTG rock assemblage. It is suggested that the study area may be in the tectonic environment of continental margin arc in Carboniferous.