辽西阜新中生代玄武岩中深源捕虏体的岩石学和矿物化学研究

The petrology and mineral chemistry of the deep-seated xenoliths in Mesozoic basalt in Fuxin district from western Liaoning

辽西阜新中生代碱性玄武岩的Ｋ－Ａｒ同位素年龄为８４．７６±１．６７Ｍａ， 其中含有丰富的深源岩石捕虏体， 包括角闪尖晶二辉橄榄岩、尖晶石二辉橄榄岩、含长角闪二辉石岩、二辉麻粒岩和辉石斜长片麻岩等。与新生代玄武岩中的同类捕虏体相比， 橄榄岩类捕虏体中橄榄石的成分相似 （Ｆｏ＝ ８６～９１）， 透辉石具有富Ａｌ、贫Ｃｒ 和Ｃａ 的特点， 尖晶石的成分以ＭｇＡｌ２ Ｏ４ 为主， 有的橄榄岩捕虏体中含少量韭闪石。二辉麻粒岩捕虏体中的斜方辉石为紫苏辉石， 单斜辉石为普通辉石， 斜长石属于更长石。橄榄岩类捕虏体的平衡温度为１０１２．６℃～１２７２．１℃； 压力为１．８２５～２．９３５ＧＰａ， 二辉麻粒岩和片麻岩的平衡温度为８９２℃～１１５７℃。该类深源岩石捕虏体的发现对中国东部中生代上地幔和下地壳的研究均具有重要意义。

The K Ar isotopic age of Mesozoic alkali basalt in Fuxin district from western Liaoning is 84 76±1 67Ma The abundant deep seated xenoliths are discovered in the basalt They are amphibole spinel iherzolite, spinel iherzolite, plagioclase bearing amphibole websterite, two pyroxene granulite and clinopyroxene plagioclase gneiss etc Compared with same xenoliths in Cenozoic basalts, the composition of olivines in peridotite xenoliths is similar (Fo=86～91); diopside is rich in Al, but poor in Cr and Ca; the compositions of spinels are major in MgAl 2O 4, pargasites exist in some peridotite xenoliths Opx and Cpx in two pyoxene granulite are hypersthene and augite, respectively, plagioclases belong to oligoclase The equilibrium T P conditions of peridotite xenoliths are 1012 6℃～1272 1℃ and 1 825～2 935GPa, respectively The equilibrium T of two pyroxene granulite and gneisses is between 892℃～1157℃ The discovery of these xenoliths is very important to study the upper mantle and lower crust in eastern China