Cristobalite in a rhyolitic lava dome: evolution of ash hazard
Cristobalite in a rhyolitic lava dome: evolution of ash hazard
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DOI：
10.1007/s00445-009-0327-1
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发表时间：
2010-03-01
影响因子：
3.5
通讯作者：
Cressey, Gordon
中科院分区：
文献类型：
--
作者：
Horwell, Claire J.;Le Blond, Jennifer S.;Cressey, Gordon
长期和大量暴露于可吸入的富含硅的结晶火山灰颗粒中，可能会导致生活在火山灰频繁降落地区的个人患上慢性纤维化疾病，如矽肺病。在这里，我们展示了智利Chait火山喷发的流纹岩灰烬，在其圆顶形成阶段，与它最初的plinian喷发相比，含有更高水平的硅多晶方石。在最初的爆炸阶段（2008年5月2日至5日）爆发的火山灰含有大约2 wt.%的方石英，而在圆顶生长开始后（2008年5月21日）产生的火山灰含有13-19 wt.%的方石英。这项研究表明，活跃的黑曜石圆顶在几天到几个月的时间尺度上结晶了大量的方英石，可能是通过脱气通道壁上的气相结晶，而不是通过玻璃状黑曜石的球晶生长。灰分细粒（直径9.7 ~ 17.7 vol.% < 4 μ m，可吸入范围），颗粒多呈角状。稀疏的纤维状颗粒被证实是长石或玻璃。
Prolonged and heavy exposure to particles of respirable, crystalline silica-rich volcanic ash could potentially cause chronic, fibrotic disease, such as silicosis, in individuals living in areas of frequent ash fall. Here, we show that the rhyolitic ash erupted from Chait,n volcano, Chile, in its dome-forming phase, contains increased levels of the silica polymorph cristobalite, compared to its initial plinian eruption. Ash erupted during the initial, explosive phase (2-5 May 2008) contained approximately 2 wt.% cristobalite, whereas ash generated after dome growth began (from 21 May 2008) contains 13-19 wt.%. The work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time-scales of days to months, probably through vapour-phase crystallisation on the walls of degassing pathways, rather than through spherulitic growth in glassy obsidian. The ash is fine-grained (9.7-17.7 vol.% < 4 A mu m in diameter, the respirable range) and the particles are mostly angular. Sparse, fibre-like particles were confirmed to be feldspar or glass.