辽西义县组玄武岩捕虏晶的发现及其意义

The high-Mg basalts rich in magnesium (MgO = 8% - 10%) existing in the bottom of Yixian formation of Early Cretaceous in the west Liaoning Province used to be called "High-Mg basalt". The authors of this paper recognize the olivine and clinopyroxene contained in those basalts as mantle xenocrysts according to studies on their morphological features, zoned structure, and opaque minerals borne in them. Reaction of the xenocrysts with the melt mass not only resulted in the zoned structure, but also increased the content of magnesium in the melt because contents of Mg, Ni, and Cr are higher and contents of Fe, Mn, and Ca are lower in the xenocrysts than in the basaltic melt. Besides, the anti-zoned and complex-zoned structure of the clinopyroxenes reflect intermingling of two kinds of melts. Discovery of those olivine and clinoaugit xenocrysts, therefore, helps to reveal: 1) interaction of the lithospheric mantle with the melt mass, which resulted in the high-magnesium rocks, and 2) intermingling of the two kinds of melts. The discovery is of significance for further researching transformation and disruption of the Mesozoic lithosphere in North China and for understanding the Mesozoic geodynamic background and tectonic settings of the eastern North China Craton.