北武夷地区早泥盆世花岗岩的确定及其地质意义

Determination of Early Devonian Granite in North Wuyi Area and its Geological Significance

在北武夷地区建瓯南雅一带识别出一套早泥盆世花岗岩,LA-ICP-MS锆石U-Pb年龄分别为401.2 Ma、403.8 Ma。该套花岗岩为高钾钙碱性过铝质花岗岩,稀土元素表现出轻稀土富集、重稀土亏损的右倾模式,轻重稀土分馏明显,(La/Yb)N为24.91~35.88,弱Eu负异常。微量元素蛛网图显示亏损Nb、Ti等高场强元素,Rb、K、Pb等大离子亲石元素富集,具S型花岗岩特点,形成于同碰撞构造环境,初步判断为早古生代晚期洋盆闭合过程的产物之一。早泥盆世花岗岩的发现,进一步完善福建省侵入岩岩浆发育谱系,对探讨省内地质构造演化有重要意义。

A set of early Devonian granite was identified in the Northern Wuyi Jian’ou Nanyi area, that the LA-ICP-MS zircon U Pb aged was respectively 401.2 Ma and 403.8 Ma. The granite is peraluminous granite of high potassium calc-alkaline series. The characteristics of REE pattern shows LREE enrichment and HREE depletion. The fractionation of LREE and HREE is obvious, the value of(La/Yb)N is between24.91 and 35.88,and shows weak Eu negative anomaly. Trace element spider grams show that high field strength elements such as Nb and Ti are depleted, and large ion lithophile elements such as Rb, K and Pb are enriched, showing characteristics similar to S-type granite, forming in the same collisional tectonic environment. The discovery of early Devonian granite has further improved the lineage of intrusive magma development in Fujian Province, and it has great significance to the study of the geological tectonic evolution in Fujian Province.