The pressure estimated by amphibole geobarometer in syenite and granil

在0.05GPa ~ 0.34GPa的水压和FMQ缓冲层的氧逸度条件下，估算了含角闪石的正长岩和花岗质岩石的压力范围为600 ℃ ~ 930 ℃。角闪石的稳定极限曲线在低压时的P-T斜率为正，高压时为负，与正长岩和花岗岩的固相线相交于两个压力点。Hammarstrom和Zen（1986，1992）提出了钙碱性岩体的结晶压力与镁铝榴石全铝含量之间的经验关系。然而，在目前的实验中，角闪石固相线附近的化学成分并没有发生变化。角闪石中的角闪石含量随温度的升高而增加。如果将不同温度下合成的角闪石进行比较，角闪石地质压力计存在相当大的不确定性。本文尝试了钠、铝、镁和铁在角闪石和辉石之间的分配。

We attempt to estimate the pressure of amphibole-bearing syenites and granitic rocks in the range 600ﾟC -930ﾟC under a water pressure from 0.05GPa to 0.34GPa and oxygen fugacitied of the FMQ buffer. The stability limit curve of amphibole changes its P-T slope from positive at low pressure to negative at high pressure, and it intersects with a solidus of syenite and granite at two pressure points. We suggest that amphibole in syenite from the Yamato Mountains could have crystallized at pressres less than 0.3GPa (depth : -10 km), probably in a shallow crustal magma chamber.Hammarstrom and Zen (1986, 1992) proposed an empirical correlation between the estimated pressures of crystallization of calc-alkaline plutons and the total Al content of horublende. However, in the present experiments, the chemical composition of amphibole near solidus does not change. We reported that the pargasite content in amphibole increases with increasing temperature. If we compared with amphiboles synthesized at different temperatures, amphibole geobarometer is considerable uncertainty. We attempt the partitioning of Na, Al, Mg and Fe between amphibole and pyroxene.