松辽盆地东南缘营城组流纹岩类型及其在火山岩地层分析中的意义

Classification of Rhyolite from Yingcheng Formation and Its Significance for Volcanic Stratigraphy Analysis in Southeastern Uplift of Songliao Basin

松辽盆地深层火山岩已经成为油气勘探的重要目的层位,研究火山岩在地层分析中的作用具有一定意义。盆地东南缘九台营城组出露区的流纹岩是本次的研究对象。可以根据岩石中发育的原生构造将流纹岩划分为流纹构造流纹岩、气孔流纹岩、石泡流纹岩、块状流纹岩4种基本类型,它们具有不同的成因机制,并可以从野外露头、手标本以及岩石薄片对其进行区分。流纹岩作为流动单元的组成要素,其理想序列从下至上依次为气孔流纹岩-石泡流纹岩-流纹构造流纹岩-块状流纹岩-流纹构造流纹岩-石泡流纹岩-气孔流纹岩,但实际中常有缺失。根据流纹岩序列确定的流动单元可以作为火山岩地层研究的基本单位。

T he vocanlic strata in deep of Songliao basin has been an important target for oil/gas exploration ,study of vocanlic rocks is of some significance for strata analysis .In this paper ,we focus on the rhyolite of Yingcheng Formation on outcrops in Jiutai , southeast margin of the Songliao basin . According to primary structure of rock , rhyolite is divided into four basic types ：rhyolitic structure rhyolites , vesicular rhyolites , lithophysa rhyolites , and massive rhyolites . Each type has specific forming mechanism and can be identified at the scale of outcrops ,hand specimens and thin sections . Rhyolite is constituent element of a cooling unit ,and the ideal rhyolite sequence is vesicular rhyolites-lithophysa rhyolites-rhyolitic structure rhyolites-massive rhyolites-rhyolitic structure rhyolites-lithophysa rhyolites-visicular rhyolites ,which is often incomplete in actual study . The cooling unit defined by the rhyolite sequence can be an elementary unit for volcanic strata analysis .