内蒙古东部火山岩中云母特征及其形成条件

玄武岩中云母为金云母,其余皆为金云母到镁黑云母之间的一种特别富Mg的黑云母。在这些黑云母中MgO、TiO_2、Fe_2O_3含量明显偏高,而Al_2O_3和FeO较低。穆斯堡尔谱研究说明这些黑云母的Fe~(2+)四极分裂值比一般黑云母的小(Fe~(2+)Mz为2.35)。黑云母结晶时氧逸度较高,并保存了母岩浆SiO_2高和Al_2O_3低的特点,喷出时受到高温氧化作用的影响。

CHARACTERISTICS OF MICAS IN VOLCANIC ROCKS FROM EASTERN INNER MONGOLIA AND THEIR FORMING CONDITIONS

Micas in basalts is predominated by phlogopite, and the rest Mg-rich biotites chemically ranging between phlogopite and Mg-biotite. These biotites contain lower Al_2O_3 and FeO but obviously higher MgO, TiO_2 and Fe_2O_3.Mssbauer spectra show that the quadrupole splittings of Fe~(2+) in these biotites are low as compared with normal biotite (Fe~(2+)Mz2.35). During biotite crystallization the oxygen fugacity is relatively high. And they have preserved the characteristics of their parental magma which had high SiO_2 and low Al_2O_3. These biotites in the volcanic rocks were subjected to oxidation at high temperature after they had been brought to the surface.