【摘要】 <正> 科马提岩(Komatiite)是1969年Viljoen等根据南非巴伯顿山区科马提河命名的,用以包括当地早寒武纪斯威士兰系超镁铁质到镁铁质的一系列海底喷发火山熔岩。它们是太古代绿岩带的重要组成部分,其地质产状、岩石组合、化学成分、结构构造、成矿专属性,都与其它岩类不同,而自有独特的特征。更多还原

【Abstract】 The iron-bearing metamorphic volcano-sedimentary series in Gong-changling Iron Mine forms a part of the Archaean greenstone belt inNortheastern China. Peridotitic, pyroxenitic and basaltic komatiites arefound at the basal part of its recurring subcycles as it is elsewhere inother parts of the world, but they are associated not only with tholeiitictuffaceous layers but also with mafic sediments as well as silicic andferrosilicic banded sediments. After metamorphism, the peridotitic, pyroxenitic and basaltic komatiiteshave been altered respectively to soapstone or talc schist, tremolite schistand amphibolites or amphibolitic schist. However, being a low gradeterrain of green schist to low amphibolitic facies, some relict structuresand textures typical fo komatiites like polyhedral joints, amygdaloidstructure and spinifex texture as well as other skeletal crystal textures arewell-preserved. Petrochemically, they are similar to other komatiites in high MgO andlow K₂O and TiO₂. In succession, they are overlain by keratophyric andquartz-keratophyric pyroclastics in the middle and the upper parts of theseries, while most of the other komatiites are overlain by andesitic torhyolitic lavas. Their geological setting, chemical composition and rock assemblageas well as their textures and structures reveal in all respects that theyare the most typical komatiites ever found in the Archaean of China. Being included in the iron-bearing series, they are relatively highin iron and silica and can be used as an indicator for prospecting andexploration of banded iron ores.更多还原