熔结凝灰岩的液态熔离—泡沫熔岩流成因

若干地区的研究证明,熔结凝灰岩是液体熔离——泡沫熔岩流生成的。无色玻屑及其间隙中的褐色玻璃质胶结物为物质的熔体属性提供了证据。熔浆中丰富的水主要来自火山口湖水的向下渗漏,部分属岩浆水。未脱玻化的岩石中无色玻屑和褐色玻璃质胶结物成分分析以及褐色玻璃为主要组分的火焰石的结构和成分分析表明,熔浆中发生过熔离作用。贫水较富铁的液体球滴因密度大发生了重力分异,于负荷压力及粘性流动条件下凝结为火焰石。成岩后岩石发生了广泛的重结晶和自变质作用。德兴地区发现大量的排气筒为一奇景。

IGNIMBRITES FROM LIQUID IMMISCIBILITY: ORIGINATION OF PUMICEOUS LAVA FLOW

Research in several regions shows that the ignimbrites may be the solidified pro ducts related to liquid immiscibility. The properties of the colourless vitric clasts and the brown glassy cements of the rocks demonstrate that the original materjalfro-ming ignimbrites is pumiceous melts rich in water(some rich in CO2)and saticand very low in viscosity .The vast amount of water in melts was coming from the cauldron lak mainly which permeated and fed to the magma chamber, and partly from the magm itself. The textures and compositionsof colourless vitric clasts,brown glassy cement and fiammes indicate that liquid immiscibility was happened in the melts. Because o the liquid globules are poorer in water and richer in iron,they are denser and cau s gravitational differentiation. Under load pressure and out from viscous flow th fiammes were solidified. The rock was recrystallized and autometamorphosed widely. The fumarole pipes and cones generated in the case of devolatization in Dexing area Jiangxi Province offer the excellent example.