清原太古代花岗—绿岩区花岗岩的稀土地球化学

The REE Geochemistry of Granitic Rocks in Qingyuan Archean Greenstone-Granite Terrene

一、引言 清原地区太古代花岗岩是该区花岗—绿岩带的主要组成部分,它与绿岩一起形成稳定的太古代克拉通。 国外对太古代花岗岩的研究已较深入。近年来,还提出了稀土元素(REE)和大半径不相容元素(LIL)的数学计算模式。

The granitic rocks are an importent part of the Qingyuan Archean greenstone-granite terrene, constituting a steady Archean craton together with the greenstone rocks. This paper deals with the discussion’ about the petrogenesis of the granitic rocks in accordance with the REE geochemistry. The granitic rocks in this terrene can be classified into two types- granitic and tonalitic. Their chondrite-normalized REE distribution patterns are comparable with A and B group of the Amitzoq granitic gnessic rocks. The Melinghong tonalitic diapir exhibits a typical REE plot of Archean tonalite, its HREE is strongly depleted, near GARB. CHOND..On the basis of rare elements and field geological investigation it is possible that the both groups derived from a common parental magma. The tonalitic parental magma was derived by partial mel-tig of the lower crust, and fractional crystallization was displayed by the widespread activity of two types of the granitic rocks. The granulite-charno-ckite series are the crystal basement of the greenstone belt, which occurs as arc around the charnockite. In the light of the REE and LIL model calculation, the charnockite in Xianjinchang is probably the result of partial melting from the basic crust. After this it was migmated again, or many times.