压力对辉长岩矿物反应和部分熔融影响的实验研究

Experimental research of the pressure effect on mineral reaction and partial melting of gabbro

本文在高温高压条件下,开展了辉长岩矿物反应与部分熔融实验,利用偏光显微镜与扫描电镜对实验样品微观结构观察,研究实验中的新生矿物与熔体的分布;通过电子探针分析熔体成分特征。实验结果表明,在低压(300MPa)条件下,静压和塑性变形实验样品中,单斜辉石以固体反应方式生成橄榄石,在高压(1300MPa)塑性实验中所有实验样品都没有发现新生矿物颗粒,这与相图中低压条件下斜长石与橄榄石稳定共存,而高压下斜长石-辉石稳定共存相吻合。高压塑性变形条件下,单斜辉石和黑云母首先发生部分熔融,随着温度增高,斜长石逐渐参与熔融,熔体呈薄膜状分布在矿物颗粒边界,熔体成分依赖于参与熔融的矿物成分,表明出现的熔体为非平衡熔融结果。

This paper performed experimental studies on mineral reaction and partial melting under high temperature and high pressure. The distribution of new minerals and partial melting of experimental deformed samples were studied based on microstructures observation under optical microscope and scattered electron microscopy （SEM）, the chemical composition of melt was analyzed by using microprobe. The experimental results show that the reaction about solid to solid from clinopyroxene to olivine occurred under low pressure （300MPa） in static and plastic deformed samples, but no any reaction production was found in high pressure （1300MPa） plastic experiments, which was fit with the phase diagram for stable of plagioclase and olivine under lower pressure, plagioclase and clinopyroxene under higher pressure. The melt films were found between most of grain boundaries of minerals under high pressure. The partial melting firstly occurred in clinopyroxene, but plagioclase joined molten process with temperature increasing under high pressure. The chemical composition of melt depended on locations where minerals joined partial molten under high pressure; it means the melting process is non-equilibrium.