摘要
石榴石是研究区内暗色镁铁质岩、麻粒岩及片麻岩的主要造岩矿物之一。成分分析表明,它们是含钙铝榴石分子较多的镁铝-铁铝系列石榴石;红外光谱测定其近于铁铝榴石;穆斯堡尔谱分析表明,Fe^(3+)含量增多将引起石榴石内六配位多面体变形程度增大;晶胞参数a_0与Ca^(2+)含量呈正相关。本区石榴石是麻粒岩相变质作用的产物,形成的温压条件为780—840℃、0.85—1.10GPa。形成石榴石的反应是复杂的,其中包括角闪石与斜长石的增温脱水反应以及紫苏辉石+斜长石组合向石榴石+单斜辉石组合转化的滑动反应。
Garnet group is one of the major rodk-forming minerals in dark maficrocks, granulite and gneiss of the Archean metamorphic complex in Liaoxi-Chifeng area. It is of pyrope-almandine series containing 1ots of grossularmolecules according to electron microprobe analyses and is close to alman-dine according to infrared absorption spectra. Mossbauer spectra of garnetsshow that the increase in Fe^3+ content will lead to further deformationof six-coordinated polyhedra in garnets. There exists positive correlationbetween the cell parameter a_0 and the Ca^2+ content of garnets. Chemicalcomposition and structural relationship wfth other coexisting mineralssuggest that garnets are products of granulite facies metamorphism underthe condition of temperature 700--840℃ and pressure 0.85--1.10 GPa. Thereactions causing the formation of garnets are complex, which include thetemperature rising dehydration reaction of hornblende and plagioclase andthe sliding reaction from the hypersthepe+plagioclase assemblage to thegarnet+clinopyroxene assemblage.
出处
《岩石矿物学杂志》
CAS
CSCD
1992年第2期157-165,T001,共10页
Acta Petrologica et Mineralogica
关键词
石榴石
麻粒岩相
岩石
杂岩
变质岩
garnet
rock of granulite facies
P-T conditions
Liaoxi (West Liaoning)-Chifeng
