中文摘要：

白云母是变质岩中分布最广泛的矿物之一，在大多数矿物组合中白云母的Si含量随着变质作用压力的增加而增加，可作为地质压力计。对KMASH体系3个有限组合中多硅白云母的Si含量与温压条件关系的实验研究结果表明，多硅白云母Si含量地质压力计明显与矿物组合有关。因此，不能把这些实验结果简单地外延到矿物组合不同的天然岩石中。在KMASH体系的温压视剖面图上模拟白云母的Si含量等值线与质量较好的实验结果非常接近，由此可以把这种方法推广到KFMASH或更复杂的体系中。在利用多硅白云母Si的含量确定天然矿物组合的变质作用压力时，最好利用视剖面图的方法。

英文摘要：

Muscovite is one of the most widespread minerals in metamorphic rocks. In most mineral assemblages, the Si content in phengite increases with increasing pressure, which can be used as a good geobarometer. Experimental study of the relations between the Si content of phengite and p-T conditions in three KMASH linfited assemblages indicates that the geobarometer of the Si content of phengite is highly dependent on mineral assemblages. Consequently, we cannot simply extrapolate the experimental results to determine the metamorphic pressures of natural rocks with assemblages different from the experimental ones. Therrnopdynamic simulation of the phengite Si isopleths in the KNIASH p-T pseudosections shows a good a- greement with the experimental results of high quality. Hence, we can use this approach in the KFMASH or more comphcated systems. It is preferentially recommended to use the pT pseudosection approach contoured with phengite Si isopleths to define metamorphic pressures of natural mineral assemblages.