福建政和地区加里东期花岗岩的厘定及其大地构造意义

福建政和地区林屯石英闪长岩和富美花岗岩原定为燕山早期岩体,通过对其进行锆石LA-ICP-MS U-Pb同位素测年分析,获得的年龄分别为林屯岩体433±7 Ma,富美岩体369±4 Ma。林屯岩体全岩微量元素具有明显的Ti、Nb、Ta负异常和Pb正异常,轻稀土富集,重稀土配分曲线较为平缓,不具明显的Eu负异常,为I型花岗岩,具有板块边缘幔源岩浆的特征。富美岩体全岩微量元素具有明显的Ba、Sr、P、Ti负异常和Rb、Pb、Th、U正异常,轻稀土富集,Eu负异常明显,具有板内S型花岗岩的特征。两个岩体的同位素测年及元素地球化学分析结果证明,这两个岩体为加里东期形成,反映了武夷山地区存在加里东期构造?岩浆事件,也为武夷山加里东构造运动的性质和时限提供了精确约束。

Identification of Caledonian granite in the Zhenghe area, Fujian province and its tectonic significance

The Lintun quartz diorite and Fumei granite in the Hezheng area of Fujian province are initially regarded as the early Yanshannian pluton. Zircon LA- ICP- MS U- Pb dating yields two ages of 433 Ma and 369 Ma for the plutons, confirming that two plutons belong to the Caledonian instead of early Yanshanian. Whole rock trace element analysis of the Lintun pluton shows distinct negative anomalies of Ti, Nb and Ta and positive anomaly of Pb. Rare earth elements analysis shows LREE enrichment, flat REE distribution pattern, without distinct negative Eu anomaly, suggesting I- type granite characteristic of mantle magma source in the margin of the plate. While whole rock trace element analysis of the Fumei pluton shows negative anomalies of Ba, Sr, P and Ti, and positive anomalies of Rb, Pb, Th and U, LREE enrichment, distinct negative Eu anomaly, presenting the characteristic of intra- plate S- type granite. Isotopic dating and element geochemical analysis of the two plutons show that the plutons are the Caledonian plutons, reflecting that the Caledonian tectonic- magmatic activites are characterized by plate tectonic effect and providing the precision constraint on feature and time limit of Caledonian tectonic movement in the Wuyishan area.