Formation of dense pyroclasts by sintering of ash particles during the preclimactic eruptions of Mt. Pinatubo in 1991.
Formation of dense pyroclasts by sintering of ash particles during the preclimactic eruptions of Mt. Pinatubo in 1991.
复制标题
1991 年皮纳图博火山爆发前的火山灰颗粒通过烧结形成致密的火山碎屑。
DOI：
10.1007/s00445-020-01427-y
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发表时间：
2021
影响因子：
3.5
通讯作者：
Hoblitt, Richard P
中科院分区：
文献类型：
--
作者：
Wang, Yining;Gardner, James E;Hoblitt, Richard P
来自1991年火山爆发前的致密玻璃质英安岩火山碎屑（英安岩岩屑）。皮纳图博进行了分析，其泡状和晶体结构和溶解H2O和CO2含量。磨粒玻璃挥发物含量（在500 μm范围内，H2O的差异为0.9wt%）的大尺度不均匀性被观察到，并认为英安岩岩屑的部分在最终建造之前在不同的深度平衡。更大的囊泡和更大和更大的数量密度的囊泡观察到磨粒玻璃斑晶周围的磨粒玻璃远离斑晶，类似的纹理在实验中产生的烧结双峰分布的颗粒。此外，越来越大比例的拉伸和扭曲的囊泡中观察到石从后来的爆炸，这平行于爆炸之间的休息时间越来越短。最后，微米大小的晶体碎片在所有英安岩岩屑的基质玻璃中无处不在。纹理，连同可变的挥发分含量，导致我们提出一个模型，英安岩岩屑形成的快速和重复烧结的灰颗粒来自各种深度的管道壁以上的碎片水平。我们推测，管道材料的烧结产生了不渗透层，阻碍了气体通过管道的流动，导致压力增加，直到盖子失效，下一次爆炸发生。
Dense, vitric, dacitic pyroclasts (dacite lithics) from the 1991 preclimactic explosions of Mt. Pinatubo were analyzed for their vesicular and crystal textures and dissolved H2O and CO2contents. Micron-scale heterogeneities in groundmass glass volatile contents (0.9 wt% differences in H2O within 500 μm) are observed and argue that parts of the dacite lithics equilibrated at different depths before finally being constructed. Greater vesicularities and larger and greater number densities of vesicles are observed in groundmass glass around phenocrysts compared to groundmass glass away from phenocrysts, similar to textures produced in experiments that sintered bimodal distributions of particles. Furthermore, increasingly greater proportions of stretched and distorted vesicles are observed in lithics from the later explosions, which parallels the increasingly shorter reposes between explosions. Finally, micron-sized crystal fragments are ubiquitous in groundmass glass of all dacite lithics. The textures, together with the variable volatile contents, lead us to propose a model that the dacite lithics formed by rapid and repetitive sintering of ash particles derived from a variety of depths on the conduit walls above the fragmentation level. We speculate that sintering of conduit material produced impermeable layers that retarded gas flow through the conduit, causing pressure to build until the cap failed and the next explosion occurred.