辽宁阜新地区晚太古宙花岗质岩石在中地壳糜棱岩化过程中的体积亏损和成分变异

VARIATION OF COMPOSITION AND VOLUME LOSS DURING MID -CRUSTAL MYLONITIZATION OF LATE ARCHEAN GRANITOID, FUXIN AREA,LIAONING PROVINCE

对辽西阜新地区晚太古宙韧性剪切变形变质岩石岩石学，常量、微量和稀土元素地球化学和矿物学的研究表明，在中地壳环境下的韧性剪切变形变质进程中，岩石中的元素都发生了不同程度的变异，主要表现为随变形强度的增加ＳｉＯ２，Ｎａ２Ｏ，Ｚｒ等组分规律性减少，而Ａｌ２Ｏ３，ＣａＯ，ＦｅＯ，ＭｇＯ等常量元素、稀土元素以及Ｂａ，Ｃｒ，Ｓｒ，Ｎｉ，Ｒｂ等微量元素规律性增加，本文认为剪切变形变质岩石的成分变异不仅仅是流体作用的结果，而且与剪切变形变质过程中的体积亏损相关。

The development of a 70 m￣80 m wide mylonite zone at mid crustal depth in Archean granitoids in Fuxin area, Liaoning Province, have been studied. Syndeformational fluid rock interaction produced substantial differences in mineral composition and bulk rock chemistry in shear zone.The changes in whole rock chemistry , trace and rare earth elements indicate increase in mass fraction of K,Na,Ca,Sr,Ni,Co,Zr and REE,and decrease in mass fraction of Si,Ba,Cr with the REE patterns remaining unchanged.The authors recognized that the variation of immobile elements result mainly from volume deficiency, but the variation of mobile elements from fluid infiltration. Based on the volume loss expression C s/ C o=1/(1- V ),the fractional volume losses are 30% and 40% respectively for blastomylonite and mylonite schist.Based on the equation of fluid and rock N =L Si /C Si f(1-S ) ,we obtain the ratio of liquid and rock of 11.8￣59.4 and 14.8￣73.9.