Experimental sintering of ash at conduit conditions and implications for the longevity of tuffisites
Experimental sintering of ash at conduit conditions and implications for the longevity of tuffisites
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管道条件下灰分的实验烧结及其对凝灰岩寿命的影响
DOI：
10.1007/s00445-018-1202-8
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发表时间：
2018
影响因子：
3.5
通讯作者：
Gardner J
中科院分区：
文献类型：
--
作者：
Gardner J
在管道中，气体从岩浆中逸出在降低爆炸性方面起着至关重要的作用。凝灰岩脉是火山岩内部和周围形成的充满火山灰的裂缝，是重要的气体逃逸通道。灰填充物的烧结降低了其孔隙率，最终形成不透气的致密玻璃。我们提出了一个实验研究的表面张力驱动的流纹质灰在浅管道条件下的烧结和相关的致密化。运行一组等温（700-800 °C）和等压H2O压力（20和40 MPa）实验持续5-90分钟。使用具有两种不同粒度分布的黑曜石粉末：1-1600 μm（平均粒度= 89 μm）和63-400 μm（平均粒度= 185 μm）。所有样品类似地通过四个纹理阶段演变：阶段1-松散和无凝聚力的颗粒;阶段2-颗粒在接触处烧结并被高达~40%孔隙率的完全连接的曲折孔隙空间包围;阶段3-部分聚结的颗粒的连续基质，其包含孤立的球形囊泡和较大的扭曲囊泡的连接网络;相4-具有2-5%完全分离的主要为球形的囊泡的致密玻璃。在较高的温度和较高的H2O压力下，织构发展得更快。粗样品烧结更慢，并且在完全烧结时包含更少、更大的囊泡。我们通过测量孔隙率作为实验运行时间的函数来量化烧结过程，并且当运行时间通过烧结时间尺度归一化时，发现数据的良好崩溃，其中η是熔体粘度，是平均颗粒半径，并且σ是熔体-气体表面张力。因为扩散H2O平衡的时间尺度通常比烧结的时间尺度快，所以相关的熔体粘度是从实验温度和压力下的溶解度H2O含量计算的。我们使用我们的结果来开发一个框架，用于估计浅管道条件下的灰烧结速率，并预测灰烧结成致密玻璃可以在几分钟到几小时内密封凝灰岩，这取决于压力（即，深度）、温度和灰分大小。
Escape of gas from magma in the conduit plays a crucial role in mitigating explosivity. Tuffisite veins—ash-filled cracks that form in and around volcanic conduits—represent important gas escape pathways. Sintering of the ash infill decreases its porosity, eventually forming dense glass that is impermeable to gas. We present an experimental investigation of surface tension-driven sintering and associated densification of rhyolitic ash under shallow conduit conditions. Suites of isothermal (700–800 °C) and isobaric H2O pressure (20 and 40 MPa) experiments were run for durations of 5–90 min. Obsidian powders with two different size distributions were used: 1–1600 μm (mean size = 89 μm), and 63–400 μm (mean size = 185 μm). All samples evolved similarly through four textural phases: phase 1—loose and cohesion-less particles; phase 2—particles sintered at contacts and surrounded by fully connected tortuous pore space of up to ~40% porosity; phase 3—continuous matrix of partially coalesced particles that contain both isolated spherical vesicles and connected networks of larger, contorted vesicles; phase 4—dense glass with 2–5% fully isolated vesicles that are mainly spherical. Textures evolve faster at higher temperature and higher H2O pressure. Coarse samples sinter more slowly and contain fewer, larger vesicles when fully sintered. We quantify the sintering progress by measuring porosity as a function of experimental run-time, and find an excellent collapse of data when run-time is normalized by the sintering timescale, whereηis melt viscosity,is mean particle radius, andσis melt–gas surface tension. Because timescales of diffusive H2O equilibration are generally fast compared to those of sintering, the relevant melt viscosity is calculated from the solubility H2O content at experimental temperature and pressure. We use our results to develop a framework for estimating ash sintering rates under shallow conduit conditions, and predict that sintering of ash to dense glass can seal tuffisites in minutes to hours, depending on pressure (i.e., depth), temperature, and ash size.
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影响因子：
4.1
作者：
James E. Gardner
通讯作者：
James E. Gardner
影响因子：
5
作者：
P. Dobson;S. Epstein;E. Stolper
通讯作者：
P. Dobson;S. Epstein;E. Stolper
影响因子：
4.9
作者：
H. Wright;K. Cashman
通讯作者：
H. Wright;K. Cashman
Mule Creek 喷口岩浆上升过程中的脱气（美国）
DOI：
--
发表时间：
1996
期刊：
影响因子：
--
作者：
M. Stasiuk;J. Barclay;Michael R. Carroll;C. Jaupart;J. Ratte;R. Sparks;Stephen R. Tait
通讯作者：
Stephen R. Tait
DOI：
10.1098/rspa.2015.0780
发表时间：
2016-04
期刊：
Proceedings. Mathematical, physical, and engineering sciences
影响因子：
--
作者：
Wadsworth FB;Vasseur J;Llewellin EW;Schauroth J;Dobson KJ;Scheu B;Dingwell DB
通讯作者：
Dingwell DB