【摘要】 汉诺坝碱性玄武岩是深源包体和巨晶的主要寄主岩,同时,也有不含包体的碱性玄武岩和含包体的拉斑玄武岩。本文基于理论计算,探讨了包体和巨晶分布的动力学机理。更多还原

【Abstract】 Alkali basalts in Hannuoba area of northern Hebei are the major host rocks of deep-seated xenoliths and magacrysts. In addition, there are somealkali basalts containing no xenoliths and megacrysts and some tholeiites contain-ing xenoliths and megacrysts. This paper deals with the dynamic mechanismfor the distribution of xenoliths and megacrysts on the basis of theoreticalcalculation. Xenoliths or megacrysts with densities larger than those of magma-tic melts are mainly present in basaltic melts with large minimum settlingradii（r^?） and low settling velocities (U₁ of xenoliths or megacrysts and highascending velocities （U₃）. Spinel peridotite xenoliths are more abundant thantransitional type peridotite xenoliths, green pyroxenite xenoliths are richer thanblack pyroxenite xenoliths, and clinopyroxene megacrysts are higher in contentthan garnet megacrysts, all related to large. r^* and low U₁ values of the formers.Anorthoclase megacrysts are obviously lower than host rocks in density andhave very small minimum ascending radii. The larger the grain size, thehigher the ascending. velocity of anorthoclase. Therefore, the anorthoclase occur--ring in basalts generally has comparatively large grain size.更多还原