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首页> 外文期刊>Contributions to Mineralogy and Petrology >Felsic lavas or rheomorphic ignimbrites: is there a chemical distinction?
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Felsic lavas or rheomorphic ignimbrites: is there a chemical distinction?

机译：长石质熔岩或变质火成岩：有化学区别吗？

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In the environment of felsic magma generation associated with continental flood basalt (CFB) provinces there is a close association between magma composition, phenocryst assemblage, temperature and eruption mechanism. In this paper we propose that by examining the chemical composition and, in particular the high field strength element (Zr and Nb) contents of the high silica rocks, we can identify those that contained halogen-rich volatiles and which degassed at different levels (deep versus shallow). The degassing depth has a direct influence on the type of eruption, with shallow degassing promoting explosive rather than effusive behaviour and consequentially the former is more likely to give rise to ignimbrites. Thus, we can infer likely eruption mechanisms, as high concentrations of F and Cl dramatically decrease magma viscosities and should favour deep degassing and hence promote lava effusion rather than explosive pyroclastic eruption. This hypothesis is tested by constraining the other possible variables which have an effect on the mode of eruption, and by examining the nature and composition of melt and fluid inclusions in quartz from CFB-associated felsic volcanic rocks.
机译：在与大陆洪水玄武岩（CFB）省相关的长岩浆岩浆形成的环境中，岩浆成分，表晶组合，温度和喷发机制之间有着密切的联系。在本文中，我们建议通过检查化学成分，尤其是高硅岩石的高场强元素（Zr和Nb）含量，我们可以鉴定出那些富含卤素的挥发物并且在不同浓度下脱气的物质（深相对浅）。脱气深度对喷发类型有直接影响，浅层脱气促进爆炸而不是喷射行为，因此前者更有可能引起火成岩。因此，我们可以推断出可能的喷发机理，因为高浓度的F和Cl会显着降低岩浆粘度，应该有利于深层除气，从而促进熔岩喷出而不是爆发性火山碎屑喷发。通过限制对喷发模式有影响的其他可能变量，并通过检查CFB相关的长英质火山岩石英中的熔体和流体包裹体的性质和成分，来检验该假设。

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