北京西山东岭台组火山岩包裹体均一过程及研究意义

THE HOMOGENEOUS PROCESS OF MELT INCLUSIONS AND ITS IMPLICATION FOR THE VOLCANIC ROCKS OF THE DONGLINGTAI FORMATION, WESTERN MOUNTAINS, BEIJING

东岭盆地内东岭台期火山活动有五个阶段,其中流纹质熔结凝灰岩很发育,单元流层特征变化明显。石英晶屑内熔融包裹体发育。本文研究了其均一过程,即包裹体净化现象、裂纹弥合、二次气泡的出现与消失、在某一温度间隔内气泡明显变小等现象。提出了气泡较大时常不能获得均一温度,代表捕获时非均一相的看法。据包裹体固相探针分析资料投图解释均一过程的成因,并给出了一种确定火山喷发前熔体中水含量的方法。

The volcanic rocks of Donglingtai formation,in the Western Mountains,Bejing,consist mainly of rhyolitic welded pyroclastic rocks which were formed from ash flows and pyroclastic flows. A great mumber of melt inclusions are there in the quartz phenocrysts. And the research of their homogeneous process is of essential importance for understanding of the genesis of the rocks and for the correct usage of homogeneous temperature date. The process provides a new way to determine the water content in magmas.