贵东东部花岗岩岩体蠕英石的特征与成因初步探讨  

PRIMARY STUDY ON THE ORIGIN OF MYRMEKITE IN EASTERN GUIDONG GRANITIC MASSIVE

作　　者：张玉燕[1] 李子颖[1] 黄志章[1] 李秀珍[1] 

机构地区：[1]核工业北京地质研究院,中核集团铀资源勘查与评价技术重点实验室,北京100029

出　　处：《矿物岩石》2016年第2期17-26,共10页Mineralogy and Petrology

摘　　要：贵东东部花岗岩岩体中多发育蠕英石,一般为3%-5%,有时高达8%。蠕英石的产出条件多种多样,形态千姿百态。随着岩浆演化,岩石粒度变细,蠕英石越来越不发育,且蠕英石中的蠕石英含量越来越低。如产于粗粒斑状角闪黑云母二长花岗岩中蠕英石的蠕石英含量高达27.78%,中粒斑状黑云母花岗岩蠕英石中的蠕石英含量约为18.44%;中-细粒黑云母花岗岩中蜗牛状蠕英石中的蠕石英含量约为10.00%,细粒黑云母花岗岩粒间蠕英石中的蠕石英含量仅为9.11%。蠕英斜长石中Ab含量一般比主晶斜长石中Ab含量高,如粗粒角闪黑云母二长花岗岩蠕英斜长石中An为8-27,主晶斜长石An为33-41;当主晶斜长石属于钠长石区的斜长石时,蠕英斜长石与主晶斜长石的成分相差不多。贵东东部花岗岩蠕英石化与钠长石化密切共生,两者在时间和空间上具有统一性,存在此消彼长的关系。综合研究认为贵东花岗岩中蠕英石的形成是交代成因,且岩石动力变形是蠕英石形成的必要条件。The myrmekite occurs in intermediate-acidic intrusive rocks of eastern Guidong granitic massive,usually ranges from 3% to 5%,sometimes up to 8%,with various occurrence and shapes.Myrmekite becomes poorly developed as the grain size of the rocks becomes finer during the evolution of magma.From early to late in age and from coarse to fine in crystal size,myrmekite is found less and less,whereas the myrmekitic quartz is decreasing.In fact,the content of myrmekitic quartz in coarse-grained porphyritic biotite granite reaches to 27.78%,the content of myrmekitic quartz in medium-grained porphyritic biotite granite is 18.44%,the content of snaillike myrmekitic quartz in medium-grained porphyritic biotite granite is 10.00%,while the content of myrmekitic quartz in the fine-grained biotite granite is only 9.11%.It reveals that the albite molecule content of plagioclase is higher in myrmekite than that in the host plagioclase.Plagioclase in myrmekite in coarse-grained porphyritic biotite granite has calciclase index An ranging from 8to 27,while in the host plagioclase ranging from 33 to 41.The plagioclase composition between them is almost the same if host crystal plagioclase belongs to albite range.Myrmekite metasomatism and albite metasomatism exist in the same space and same time with counter proportion.It is considered that myrmekite is results from metasomatism and caused by rock deformation stress.

关 键 词：蠕英石 蠕石英 蠕英斜长石 交代作用 贵东东部花岗岩岩体 

分 类 号：P588.121[天文地球—岩石学]