加热处理镁铝榴石的晶体化学研究

通过应用XRD,IR和MS谱对加热过程中的一个紫红色含铬镁铝榴石样品作了研究,结果表明,在1000℃时,镁铝榴石转化为辉石和非晶态的Al_2O_3,但在加热只达800℃的过程中,其十二面体中的Fe^(2+)逐渐氧化为Fe^(3+),并与四面体中原有的Fe^(3+)和八面体中的Al^(3+)一同析出。从而得出,在镁铝榴石结晶过程中,高温有利于Fe^(3+)和Cr^(3+)取代Al^(3+)进入八面体,但却不利于Fe^(3+)进入四面体。这一结论对重新认识镁铝榴石在金刚石找矿方面的标志特征具有十分重要的意义。

Garnet of the Pyrope-Majorite Series from Coorara Meteorite and Lamprophyres of Central Timan

In kersantite and spessartite dikes of Chetlas Kamen＇ in Central Timan among accessory garnets, that are rather rare in lamprophyres, there was discovered few and for the first time high-majorite pyrope garnet with majorite minal Mg3Fe2[SiO4]3 （26-42%）, similar to majorite garnet originating from a meteorite. Majorite discovered in Coorara meteorite is very rare in the terrestrial rocks. As it is shown, there is 18% pyroxene admixture in original analysis of maj orite that is why a surplus of S i appeared in its formula. In rocks, where majorite garnet was found, there are also revealed microcrystalline diamonds.