作　　者： ; ; ; (胡双怀）;

机构地区： 深圳职业技术学院

出　　处： 《吉林大学学报（地球科学版）》 2004年第3期344-350,共7页

摘　　要： 平岗-渭津中性中基性火山岩的岩石化学特征显示:岩石类型主要有钾玄岩、玄武安山岩、安山岩、歪长粗面岩,岩浆系列以高K钙碱性系列为主,伴有钾玄岩系列和拉斑玄武岩系列;轻稀土富集,Eu异常不明显;Sr、K、Rb、Ba、Th等强不相容元素富集、高场强元素Nb相对亏损,反映出火山岩具火山弧与板内玄武岩构造背景的双重性。钾玄岩的Mg值及Ni含量表明钾玄岩属进化了的基性岩浆。根据Nd、Sr同位素比值及英安岩中辉石巨晶的结晶深度、松辽盆地东侧的地壳厚度等资料,认为钾玄岩浆来源于幔源基性岩浆。通过对岩浆密度及结晶压力、温度的估算认为多斑钾玄岩的形成与岩浆密度、斜长石密度及斜长石的结晶压力有关。 The petrologic characteristics of the intermediate and intermediate-basic volcanics from Pinggang-Weijin area are: main rocks are shoshonite, basalt-andesite, andesite and latite; magmatic evolution series belongs to high potassium calc-alkali series, accompanied by minor shoshonitic series and tholeiitic series; rich in LREE and lack in Eu anomaly; Sr、K、Rb、Ba、Th enriched, but Nb is lower, indicating the volcanic rocks in the area were formed in a mixed tectonic setting of both volcanic arc and inter-plate. Mg and Ni contents in shoshonite indicate that the shoshonite was derived from an evolved basic magma. Based on Sr/Nd ratios and crystalline depth of pyroxene megacrystals in dacite and crust thickness of the east side of the Songliao Basin, it is inferred that the shoshonitic magma originated from primary magm from the mantle. It is recognized that the formation of shoshonite is related to the density of magma and plagioclase and to the crystallizing pressure of plagioclase based on estimation on the density of magma, crystalline pressure and temperature.

关 键 词： 中性 中基性火山岩 钾玄岩 岩浆起源 平岗 渭津

领　　域： [天文地球] [天文地球]