辽西四合屯-后燕子沟早白垩世火山机构及火山喷发作用的演化

Evolusion of Sihetuen-Houyanzigou Early Cretaceous volcanic cluster apparatus and volcanic effusive activity in western Liaoning

在四合屯—后燕子沟火山岩区的工作,确定了火山机构的组合、分布及其类型。并将本区的火山作用划分为4个亚旋回。亚旋回Ⅰ的下部为凝灰质胶结复成分细砾岩,上部聚斑状橄榄玄武岩,气孔杏仁状玄武岩。亚旋回Ⅱ的下部为凝灰质杂砂岩、沉凝灰岩、凝灰岩和玄武安山质集块岩。上部杏仁状橄榄玄武岩与玄武安粗岩互层,夹辉石玄武安山岩。亚旋回Ⅲ为玄武安山质晶屑岩屑凝灰岩、岩屑杂砂岩、玄武安山质熔结集块岩、杏仁状橄榄黄长碧玄岩、拉斑玄武岩、安山质集块角砾岩、杏仁状玄武安山岩和杏仁状安山岩夹橄榄玄武岩。亚旋回Ⅳ为火山喷出大量橄榄玄武岩,杏仁状玄武岩和玄武安山岩,盖在凝灰质岩屑长石杂砂岩上。该火山岩区是一个巨大的组合式火山机构,火山机构中心地段由十几个火山口组成,构成中心火山群,即中心火山机构。外侧还有5个小火山群形成次级火山机构,围绕其近于有规律地匀称地分布,每个次级火山机构的中心火山口外侧也有数个火山口呈环状围绕其分布。故称其为"组合式"火山机构。"组合式"火山机构中心地带发现了含有地幔岩成分的橄榄玄武岩、碧玄岩。"组合式"火山机构是由含有地幔岩浆物质形成的。

By the regional detailed survey, we discovered the association, distribution and types of the volcanic apparatus, and finded outcropping mantle rocks in that area. The volcanic activity of the first member of Yixian Formation in this area can be divided into four volcanic eruption subcycles. Subcycle I - The lower part of the layer is a thick-bedded tuffaceous polymictic microconglomerate. The upper part is glomeroporphyric dorgalite and vesicular amygdaloidal basalt. Subcycle II : The lower part of the layer contains tuffaceous greywacke, sedimentary tuff, tuff and basaltic andesitic agglomerate. The upper part is amygdaloidal dorgalite, interbedded with latibasalt, and intercalate pyroxene basaltic andesite. Subcycle III : Crystal-lithic tuff, lithic basaltic andesitic greywacke, welded agglomerate, amygdaloidal olivine melilite basanite, tholeiite, amygdaloidal basaltic andesite and amygdaloidal, which contain interbed of dorgalite. Subeycle IV: The volcanic erupted a great deal of dorgalite, amygdaloidal. basaltic andesite and basalt on tuffaceous lithic feldspathic greywacke. A great deal of volcanic apparatus occurred in Sihetuen-Houyanzigou volcanic area in association style. About five craters distributed in the center of volcanic field. They are in a center volcanic cluster around which these are five small volcanic cluster in near annular. Every small volcanic cluster made up a small volcanic apparatus. Similarly, small volcanic apparatus also have center volcanic crater rounded by a number of small volcanic craters. We name it as the 'assemblage type' volcanic apparatus. Combination basanite and dorgalite was discoved in the center district of the' assemblage type' volcanic apparatus. According to geochemical research, magma occurred at the depth up to 118 kilometers, we recognize that the magma material derived from upper mantle.