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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Recent volatile evolution in the magmatic system of Hekla volcano, Iceland
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Recent volatile evolution in the magmatic system of Hekla volcano, Iceland

机译：冰岛赫克拉火山岩浆系统近期的挥发性演化

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摘要

Estimates of the volatile budgets for volcanic eruptions are often based on volatile concentrations measured in melt inclusions (MIs) versus groundmass glass. Here, we present new measurements and estimates of pre-eruptive volatile concentrations in magma from the Hekla volcano in Iceland based on MIs in recent basalts and basaltic icelandites from the 2000 eruption. The last eruption at Hekla occurred from 26 February to 8 March, 2000. It began with a short sub-Plinian phase followed by lava effusion that produced 0.17 km(3) of basaltic icelandite. Volatile (S, Cl, F and H2O) and major element concentrations were measured in MIs trapped in olivine and plagioclase phenocrysts contained in the basaltic icelandite from the 2000 eruption and in basalt erupted in 1913 from a fissure adjacent to the Hekla volcano. Same elements were measured in the groundmass glass from the 2000 tephra. The observed compositional range of MIs from the basalt (MgO <= 7.73%) to the basaltic icelandite (MgO <= 2.51%) is readily explained by fractional crystallisation, allowing the prediction of the evolution of dissolved volatile concentrations within the magma plumbing system beneath Hekla. The incompatible behaviour of the volatile elements controls their concentrations in MIs during the crystal fractionation, and consequently the highest concentrations are found in the most evolved basaltic icelandite MIs, with the notable exception of sulphur. Volatile concentrations in the basaltic MIs exhibit strong linear correlations with K2O and this relationship can be used to estimate the theoretical "expected" volatile contents in the basaltic icelandite melt just prior to eruption. Such an approach avoids underestimation of the pre-eruptive volatile contents measured in MIs and improves constraints on the volatile mass release into the atmosphere. The difference of volatile contents between "expected" concentrations and those present in the groundmass, scaled to the mass of erupted magma, yields maximum atmospheric mass loading of 0.10 Mt HCl, 0.17 Mt HF and 3.77 Mt SO2 during the 2000 Hekla eruption, whereas calculations using the measured values in the inclusions give a significant lower mass yields of 0.05 Mt HCl, 0.17 Mt HF and 0.6 Mt SO2. These results are discussed and compared to the data derived from remote sensing and snow (proxy of the gas phase) measurements. (c) 2007 Elsevier B.V. All rights reserved.
机译：火山喷发挥发物预算的估算通常基于熔体夹杂物（MIs）与地面玻璃中测得的挥发物浓度。在这里，我们根据2000年爆发的玄武岩和玄武质冰岛岩中的MIs，提出了冰岛Hekla火山岩浆喷发前挥发物浓度的新测量值和估计值。最后一次喷发发生在Hekla，发生于2000年2月26日至3月8日。它始于短暂的次普林期，随后是熔岩喷出，产生了0.17 km（3）的玄武质冰岛岩。在2000年爆发的玄武岩冰岛岩中所含橄榄石和斜长石的隐晶岩中以及1913年从邻近赫克拉火山的裂缝中喷出的玄武岩中所捕集的MI中，测定了挥发性有机物质（S，Cl，F和H2O）和主要元素的浓度。在2000 tephra的地面玻璃中测量了相同的元素。分数结晶很容易解释所观测到的从玄武岩（MgO <= 7.73％）到玄武质冰岛岩（MgO <= 2.51％）的MIs组成范围，从而可以预测下方岩浆管道系统中溶解挥发物浓度的演变。嘿啦挥发性元素的不相容行为控制了晶体分级分离过程中MI中的浓度，因此，在演化最广的玄武质冰岛MI中发现了最高的浓度，但硫例外。玄武质MIs中的挥发物浓度与K2O表现出很强的线性相关性，该关系可用于估算火山爆发前玄武质冰岛熔岩中理论上的“预期”挥发物含量。这种方法避免了低估了以MIs为单位的喷发前挥发性物质的含量，并改善了对释放到大气中的挥发性物质的限制。计算得出的“预期”浓度与地下物质中挥发性物质之间的挥发物含量之差，按喷出的岩浆质量定出，在2000年Hekla喷发期间，最大大气质量负荷为0.10 Mt HCl，0.17 Mt HF和3.77 Mt SO2。使用夹杂物中的测量值可得出较低的质量产率，即0.05 Mt HCl，0.17 Mt HF和0.6 Mt SO2。对这些结果进行了讨论，并将其与从遥感和降雪（气相代理）测量得出的数据进行了比较。 （c）2007 Elsevier B.V.保留所有权利。

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