摘要
同位素年代学研究表明:长乐-南澳变形变质带存在元古宙的古陆块,随后至少经历了加里东、印支、燕山、喜马拉雅等4期构造热事件。岩石化学特征显示:加里东基底岩石为正变质岩;印支、燕山期盖层岩石有正变质岩,也有负变质岩。从加里东→印支、燕山期,SiO_2含量从低到高,FeO+MgO+CaO+TiO_2含量由高到低呈现规律性变化。稀土地球化学研究表明:加里东期基底岩石稀土总量较低,轻重稀土轻度分异,Eu正异常,为轻稀土轻度富集,重稀土平坦型;印支、燕山期盖层岩石稀土元素总量较高,轻重稀土强烈分异,Eu负或无异常,为轻稀土富集、重稀土强烈亏损型。从加里东→印支、燕山期、稀土总量从低到高,轻重稀土分异由弱到强,Eu从正异常到负或无异常呈现规律性演化。
The study of isotope chronology shows that there possibly existed a Proterozoic continental block in the Changle-Nanao deformation metamorphic belt and that after the Proterozoic the Changle-Nanao deformation-metamorphism belt at least underwent 4 tectono-thermal events (Caledonian, Indosinian, Yanshanian and Himalayan). Petrochemical study shows; Caledonian basement rocks are positve metamorphic rocks; there are not only positive but also negative metamorphic rocks in the Indosinian-Yanshanian covers; there is a regular variation in the petrochemical composition from the Caledonian to Indosinian-Yanshanian metamorphic rocks, i. e. an increase of the SiO2 content and a decrease of FeO* +MgO + CaO + TiO2. REE study indicates that the Caledonian basement rocks are characterized by a low 2REE, a low ratio of LREE/ HREE and positive Eu anomaly, showing a LREE-enriched and HREE-smooth pattern; whereas the Indosinian-Yanshanian covers have a high ∑REE, a high ratio of LREE/HREE and negative or no Eu anomaly, exhibiting a LREE-enriched and HREE-depleted pattern. There is a regular variation in the REE composition from Caledonian to Indosinian-Yanshanian metamorphic rocks, i. e. increases in ∑REE and LREE/HREE and a conversion from positive to negative or no Eu anomaly.
出处
《地质论评》
CAS
CSCD
北大核心
1996年第3期223-231,共9页
Geological Review
