Discovery of xenocrysts in basalts of Yixian Formation in west Liaoning Province and its significance.

辽西早白垩世义县组底部有一套镁含量较高(MgO=8%～10%)的橄榄玄武岩,有人称之为“高镁玄武岩”。通过这些玄武岩所含的橄榄石、单斜辉石的形态特征、环带结构以及所包含不透明矿物的研究,笔者认为它们属于地幔捕虏晶。捕虏晶和玄武质熔体反应的结果形成了环带结构,由于捕虏晶比玄武质熔体富 Mg、Ni、Cr,贫 Fe、Mn、Ca,因此作用结果提高了熔体的镁含量。此外,辉石的反环带以及复杂环带结构反映了两种熔体的混合作用。因此上述橄榄石、辉石捕虏晶的发现有助于揭示:1)岩石圈地幔和熔体相互作用以及高镁岩石的成因;2)两种熔体的混合作用。这一发现对进一步研究华北中生代岩石圈地幔的改造与破坏,理解华北克拉通...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.SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)0061547-15582