新丰花岗岩稀土分布型式的初步研究
来源期刊：中南大学学报(自然科学版)1984年第4期
论文作者：朱余德 阮道源
文章页码：101 - 107
关键词：花岗岩体； 分布型式； 过渡相； 中稀土； 褐帘石； 斜长石； 重稀土； 独居石； 变化规律； 稀土元素
摘 要：新丰花岗岩中有两类稀土分布型式,在中心相花岗岩中轻重稀土比值较大（LREE/HREE>3）,有着不显著的铕负异常（δEu>0.5）;而在过渡相花岗岩中轻重稀土比值较小（LREE/HREE<8）,有着较显著的铕负异常（δEu<0.5）。在岩体中轻重稀土比值和δEu值有随着SiO2含量增加而减小的变化规律。经研究,中心相花岗岩中稀土分布型式主要与褐帘石和斜长石有关,而过渡相花岗岩主要与独居石、磷钇矿、斜长石和褐钇铌矿有关。许多证据表明新丰花岗岩应属岩浆型花岗岩,而且是由中心相花岗岩往过渡相花岗岩演化的。花岗岩中和矿物中稀土元素分布型式的变化规律也正反映了这样的演化过程。
Abstract: Xinfeng granite is the northeast part of Fogang batholith. The determination of rare earth elements （REE）for Xinfeng granite, two rock samples in the central facies granite and three rock samples in the intermediate facies, shows two types of chondrite normallization REE pattern. The granite in the central facies has greater values of LREE/HREE （LREE/HREE>3） but has unnoticeable Eu depletion （<δEu>0.5）,while that in the intermediate facies shows lower values of LREE/HREE（LREE/HREE<3）and obvious Eu depletion （Eδu<0.5） . The values of both LREE/HREE and δEu show a systemetic decrease with the increase of SiO2. In the central facies granite the chondrite normallization REE patterns are mainly affected by allanite and plagioclase, while in the intermediate facies graniteby monazite, xenotime, plagioclase and fergusonite. Rare earth elements have been determined and the chondrite normallization REE patterns have been plotted for the above minerals except plagioclase which also has been studied through REE partition co efficients. A lot of evidence indicates that Xinfeng granite is formed mainly through the differentiation from the central facies to the intermediate facies. The chondrite normallization REE patterns in the granite, of course, are chiefly controlled by the differentiation of the granitic magma. The distribution of REE in the granite and in the minerals indicates that this assump tion is acceptable.
