基于氧化系数的火山喷发环境判别:以准噶尔盆地西北缘下二叠统为例

Discrimination of Volcanic Eruption Environment Using Oxidation Index:A Case Study of Lower Permian Volcanic Rocks in Northwestern Margin of Junggar Basin

火山喷发环境的准确判别是火山岩储层评价的重要依据,准噶尔盆地西北缘下二叠统火山岩类型多,沿盆地边缘断裂带分布,是这一地区重要的油气储层类型。文章通过岩芯分析、薄片观察、地球化学元素分析等手段,对该区火山岩的喷发环境展开研究。基于75个火山岩样品数据,对火山岩的氧化系数进行分析,并充分考虑了喷发环境、岩浆性质、风化及埋藏作用等因素对氧化系数的影响,改进了传统的基于氧化系数的火山喷发环境判别图。实际应用结果与其他判别依据得到的结果进行对比,符合率达到92.86%,仅两例不符。这一判识图可供其他相似地质背景地区参考使用,所获认识为研究区火山岩储层评价提供了新思路。

Accurate discrimination of the volcanic eruption environment is the foundation of volcanic reservoir evaluation. Many typesof Lower Permian volcanic rocks are developed in the northwestern margin of Junggar Basin,which are mainly distributed along thefault zone of the basin margin,and is an important type of petroleum reservoirs. In this paper,the eruptive environment of volcanicrocks in study area is studied by means of cores analysis,thin-sections observation and geochemical element analysis. The oxidationindex has been studied from the 75 volcanic rock samples around the world,and thus improved the traditional method of volcaniceruption environment discrimination with full consideration of its influencing factors such as the eruption environment,magmaticproperties,weathering and burial diagenesis. Finally,the coincidence rate of actual application results with the results of otherdiscriminators ups to 92.86%,with only two cases discrepant.The discrimination chart established in this paper is available for otherregions with similar geological background and the results of this paper could provide a new idea for the evaluation of volcanic rockreservoirs in the study area.