New geochemical insights into volcanic degassing
New geochemical insights into volcanic degassing
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DOI：
10.1098/rsta.2008.0185
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发表时间：
2008-12-28
期刊：
影响因子：
5
通讯作者：
Edmonds, Marie
中科院分区：
文献类型：
--
作者：
Edmonds, Marie
岩浆脱气作用在控制火山喷发样式中起着根本性的作用。火山爆发是爆炸性的还是喷发性的，对全世界生活在危险火山阴影下的大约5亿人至关重要。由于出现了更精确和自动化的方法来测量作为火山气体和溶解在喷发产物玻璃中的挥发性物质，对气体在喷发之前和喷发期间如何从岩浆中逸出和分离的研究得到了新的推动。火山气体的成分取决于许多因素，最重要的是岩浆成分和喷发前气体熔体分离的深度;后一个参数在过去被证明很难限制，但可以说是控制喷发风格的最关键因素。红外光谱技术在高时间分辨率测量气体成分方面具有重要价值。这些方法，当与喷发产物的微分析地球化学调查结合使用时，会导致更好地限制气体产生和从岩浆中分离的深度。最近的一些研究集中在爆炸和溢出活动之间的过渡，并导致更好地了解玄武岩火山的气体-熔体分离。其他研究集中在中期和中期喷发期间的脱气。重要的新成果包括认识到深源气体，缓冲量的溶解挥发物在熔体中的浅深度，并观察气体流动的渗透导管壁剪切带，这可能是主要的机制，气体损失的尖端最爆炸性和不可预测的火山爆发。在本文中，我回顾了火山脱气过程的地球化学研究领域的当前和未来的方向，并说明了新的见解是如何开始改变我们理解和分类火山喷发的方式。
Magma degassing plays a fundamental role in controlling the style of volcanic eruptions. Whether a volcanic eruption is explosive, or effusive, is of crucial importance to approximately 500 million people living in the shadow of hazardous volcanoes worldwide. Studies of how gases exsolve and separate from magma prior to and during eruptions have been given new impetus by the emergence of more accurate and automated methods to measure volatile species both as volcanic gases and dissolved in the glasses of erupted products. The composition of volcanic gases is dependent on a number of factors, the most important being magma composition and the depth of gas melt segregation prior to eruption; this latter parameter has proved difficult to constrain in the past, yet is arguably the most critical for controlling eruptive style. Spectroscopic techniques operating in the infrared have proved to be of great value in measuring the composition of gases at high temporal resolution. Such methods, when used in tandem with microanalytical geochemical investigations of erupted products, are leading to better constraints on the depth at which gases are generated and separated from magma. A number of recent studies have focused on transitions between explosive and effusive activity and have led to a better understanding of gas - melt segregation at basaltic volcanoes. Other studies have focused on degassing during intermediate and silicic eruptions. Important new results include the recognition of fluxing by deep-derived gases, which buffer the amount of dissolved volatiles in the melt at shallow depths, and the observation of gas flow up permeable conduit wall shear zones, which may be the primary mechanism for gas loss at the cusp of the most explosive and unpredictable volcanic eruptions. In this paper, I review current and future directions in the field of geochemical studies of volcanic degassing processes and illustrate how the new insights are beginning to change the way in which we understand and classify volcanic eruptions.