Geochemical evidence for relict degassing pathways preserved in andesite
Geochemical evidence for relict degassing pathways preserved in andesite
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DOI：
10.1016/j.epsl.2013.10.044
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发表时间：
2014-01
影响因子：
5.3
通讯作者：
Melissa Plail;M. Edmonds;M. Humphreys;J. Barclay;R. Herd
中科院分区：
文献类型：
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作者：
Melissa Plail;M. Edmonds;M. Humphreys;J. Barclay;R. Herd
安山质弧火山脱气大量的挥发物，在喷发的熔岩蒸汽运输的证据很少保存和了解甚少，但了解喷发风格是至关重要的。我们目前的地球化学证据运输的含金属的蒸汽在剪切带保存在火山喷发从苏弗里耶尔山火山，蒙特塞拉特的熔岩。纹理证据表明，剪切引起的脆性破坏发生在一个狭窄的区域（在管道壁或熔岩圆顶）。金属浓度（Cu，Au，Ag，Pb，Zn）的区域内表明，断裂作为一个短暂的通道，含金属的岩浆气体。在滑动过程中，摩擦加热到>1000 °C的温度导致滑动表面部分熔化。挥发分和金属的再吸收进入部分熔体保存了剪切带中岩浆蒸汽的地球化学特征。堇青石在火山岩中非常罕见，它是从过铝质部分熔体中结晶出来的，含有含金属的硫化物和氧化物。剪切带提供了第一个地球化学证据的蒸汽隔离和运输通过粘性安山岩岩浆，并提供了一个洞察控制喷发风格。
Andesitic arc volcanoes degas large quantities of volatiles; evidence for vapour transport in the erupted lavas is rarely preserved and poorly understood, but is crucial for understanding eruption style. We present geochemical evidence for the transport of metal-bearing vapour in shear zones preserved in lavas erupted from Soufrière Hills Volcano, Montserrat. Textural evidence suggests that shear-induced brittle failure occurred in a narrow zone (at the conduit wall or in the lava dome). Elevated metal concentrations (Cu, Au, Ag, Pb, Zn) within the zones indicate that the fractures acted as a transient pathway for metal-bearing magmatic gases. During slip, frictional heating to temperatures of >1000 °C caused partial melting at the slip surface. Resorption of volatiles and metals into the partial melt preserved the geochemical signature of magmatic vapour in the shear zone. Cordierite, which is highly unusual in volcanic rocks, crystallised from the peraluminous partial melt, with metal-bearing sulphides and oxides. The shear zones provide the first geochemical evidence for vapour segregation and transport through viscous andesite magmas and provide an insight into controls on eruption style.