The Kinetics of Degassing-Induced Crystallization at Soufrière Hills Volcano, Montserrat
The Kinetics of Degassing-Induced Crystallization at Soufrière Hills Volcano, Montserrat
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蒙特塞拉特苏弗里耶尔火山脱气诱导结晶的动力学
DOI：
10.1093/petrology/44.8.1477
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发表时间：
2003
影响因子：
3.9
通讯作者：
M. Carroll
中科院分区：
文献类型：
--
作者：
S. Couch;R. Sparks;M. Carroll
在875 ℃下进行一系列减压实验，在160 MPa下退火16小时，并减压至125 - 30 MPa的最终水压（Pf），持续1至504小时。使用实验得出的斜长石液相线，减压估计施加38和151 C之间的过冷度（DT）。实验表明，减压后斜长石晶体的成核有1 - 4 h的延迟。在所考虑的压力范围内，形核速率变化高达32 sites/mm 3/s，并随过冷度增加。斜长石的生长速率随DT的增大而增大，在Pf = 75 MPa时达到最大值17 × 10 ~（-6）mm/s。实验结果与苏弗里埃山安山岩的天然样品的比较表明，浮石样品没有经历任何减压诱导结晶，因此从岩浆房上升必须在4小时内完成。穹状样品的结构是可变的，但都包含许多小的微晶晶体与低斜长石钙长石含量和较大的微晶与钠长石过度生长边缘。实验结果表明，这些纹理的差异可以与上升速率的变化。
A series of decompression experiments at 875C, with a 16h anneal period at 160MPa, and depressurizations to a final water pressure (Pf) of 125‐30MPa, were run for between 1 and 504h. Using an experimentally derived plagioclase liquidus, the depressurizations are estimated to impose an undercooling (DT) of between 38 and 151C. The experiments show that there is a delay of 1‐4h in the nucleation of plagioclase crystals after decompression. Over the range of pressures considered, nucleation rates vary up to 32sites/mm 3 per s, and increase with undercooling. The growth rate of plagioclase increases with DT, reaching a maximum of 17 10 ˇ6 mm/s at a Pf of 75MPa. Comparison of the experimental results with natural samples of the Soufriere Hills andesite suggests that pumice samples did not experience any decompression-induced crystallization and therefore ascent from the magma chamber must have been completed within 4h. Dome samples are variable in texture, but all contain numerous small microlite crystals with low plagioclase anorthite contents and larger microlites with albitic overgrowth rims. Experimental results show that these textural differences can be related to variations in ascent rate.