摘要
本区碱性玄武岩中的多数深源包体大都含有尖晶石族矿物,不同成份的深源包体来自于上地幔上部的不同深处,它们所含的尖晶石族矿物也各不相同。据尖晶石族矿物化学成分可分为铬尖晶石、含铬尖晶石、铝尖晶石、富铝尖晶石和铁镁铝尖晶石。据尖晶石形成阶段可分为早期成岩阶段产物、成岩阶段产物、晚期成岩阶段产物,出熔阶段产物和部分熔融阶段产物。不同成分的尖晶石、不同阶段形成的尖晶石具有各自的矿物学特点及相互间的规律性。铝尖晶石比较特殊,有着一系列的重要特点,根据其主要化学成分,主要粉晶谱线和其它物理特征,定名为黑晶石。它的发现在我国尚属首次,而在碱性玄武岩上地幔深源包体中见到黑晶石全球也属首次。
Most of the deep-source inclusions in the alkalibasalt of the studied area contain spinel group minerals which differ from different deep-source inclusions with different compositions.These inclusions come from different parts of the upper portion of the upper mantle. Based on chemical composition,the minerals of this group are classi- fied as chromium spinel,chromium-bearing spinel,aluminium spinel, aluminiumrich spinel and iron-magnesium-aluminium spinel.Taking forming stage as a standard,the minerals is seperately grouped under the early diagenetic stage,diagenetic stage,late diagenetic stage, exsolution stage and partial melting stage.The spinels with different compositions or formed in different stages possess their own particular mineralogical characters,They also have certain inter-relationship. Among the said minerals,aluminium spinel,which is remarkably different from others,has a series of major characteristics.According to the analyses of chemical composition,powdery crystal x-ray curves and other physical features,it is named as magnalumoxide.This is the first time for this mineral to be found in our country.It is also the first time for magnalumoxide to be found in deep-source(upper mantle)inclusions of alkali-basalt in the world.
