Chemical characteristics of fluorine-bearing biotite of early Paleozoic plutonic rocks from the Sør Rondane Mountains, East Antarctica
Chemical characteristics of fluorine-bearing biotite of early Paleozoic plutonic rocks from the Sør Rondane Mountains, East Antarctica
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DOI：
10.2343/geochemj.37.145
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发表时间：
2003-04
影响因子：
0.8
通讯作者：
Zilong Li;Y. Tainosho;K. Shiraishi;M. Owada
中科院分区：
文献类型：
--
作者：
Zilong Li;Y. Tainosho;K. Shiraishi;M. Owada
本文测定了东南极索龙托山脉早古生代深成岩中黑云母的化学成分。将其划分为Ⅰ型花岗岩类、Ⅱ型花岗岩类和梅菲尔深成杂岩三大类。黑云母有两种类型：I型花岗岩类中的浅黄色至深绿色绿色黑云母，II型花岗岩类和Mefjell深成杂岩中的棕色至深棕色黑云母。在矿物化学上，I型花岗岩类黑云母的SiO2含量、F含量和XMg值均高于II型花岗岩类黑云母，而TiO 2和Cl含量则低于II型花岗岩类黑云母。在II型花岗岩类和Mefjell深成杂岩中，强烈富集FeO的黑云母具有较低的F含量。II型花岗岩类和Mefjell深成杂岩中黑云母的log（fHO 2）/（fHF）值远高于I型花岗岩类。I型花岗岩中黑云母的氟含量与澳大利亚东部Lachlan褶皱带部分熔融A型花岗岩相似，而II型花岗岩和Mefjell深成杂岩中黑云母的氟含量与Lachlan褶皱带分离的铝质A型花岗岩和印度南部Ambalavayal铝质A型花岗岩相当。II型花岗岩类和Mefjell深成杂岩中黑云母的低氟含量可能主要受与熔体有关的晚期岩浆流体-岩石相互作用过程的控制，可能不指示原始岩浆含量。I型花岗岩类中黑云母和全岩中较高的氟含量可能反映了富氟岩浆源区。我们对I型花岗岩中黑云母的研究结果以及地球化学结果支持了富氟A型花岗岩可能源自英云闪长岩至花岗闪长岩成分的部分熔融地壳火成岩的模型。
The chemical compositions of biotite grains have been determined for early Paleozoic plutonic rocks from the Sor Rondane Mountains, East Antarctica. The plutonic rocks are divided into three groups of the type-I granitoids, type-II granitoids and the Mefjell Plutonic Complex. Two types of biotite are found in the groups: pale yellow to dark green biotite in the type-I granitoids and brown to dark brown biotite in the type-II granitoids and the Mefjell Plutonic Complex. Mineral chemically, biotites from the type-I granitoids have higher SiO2 contents, F contents, and XMg values with lower TiO2 and Cl contents relative to biotites from the type-II granitoids. In the type-II granitoids and the Mefjell Plutonic Complex, biotite strongly enriched in FeO has lower F contents. Biotites in the type-II granitoids and the Mefjell Plutonic Complex have much higher log( f HO 2 )/( fHF) than those from the type-I granitoids. The fluorine content in biotite from the type-I granitoids is similar to that from partial melting A-type granites in Lachlan Fold Belt of eastern Australia; and those from the type-II granitoids and the Mefjell Plutonic Complex are comparable to fractionated aluminous A-type granites from the Lachlan Fold Belt, and the Ambalavayal aluminous Atype granites of South India. Lower fluorine contents in biotite from the type-II granitoids and the Mefjell Plutonic Complex may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt and may not be indicative of original magma contents. Higher fluorine contents in biotite and whole-rock from the type-I granitoids may reflect fluorine-enriched magmatic source. Our results in biotites from the type-I granitoids as well as geochemistry support the models, which fluorine-rich A-type granites may be derived from partial molten crustal igneous rocks of tonalitic to granodiorite composition.