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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka
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Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka

机译：堪察加半岛贝兹米尼火山岩浆上升期间斜长石边缘生长的数值模拟

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Slow CaAl-NaSi interdiffusion in plagioclase crystals preserves chemical zoning of plagioclase in detail, which, along with strong dependence of anorthite content in plagioclase on melt composition, pressure, and temperature, make this mineral an important source of information on magma processes. A numerical model of zoned crystal growth is developed in the paper. The model is based on equations of multicomponent diffusion with diagonal cross-component diffusion terms and accounts for mass conservation on the melt-crystal interface and growth rate controlled by undercooling. The model is applied to the data of plagioclase rim zoning from several recent Bezymianny Volcano (Kamchatka) eruptions. We show that an equilibrium growth model cannot explain crystallization of naturally observed plagioclase during magma ascent The developed non-equilibrium model reproduced natural plagioclase zoning and allowed magma ascent rates to be constrained. Matching of natural and simulated zoning suggests ascent from 100 to 50 MPa during 15-20 days. Magma ascent rate from 50 MPa to the surface varies from eruption to eruption: plagioclase zoning from the December 2006 eruption suggests ascent to the surface in less than 1 day, whereas plagioclase zoning from March 2000 and May 2007 eruptions are better explained by magma ascent over periods of more than 30 days). Based on comparison of diffusion coefficients for individual elements a mechanism of atomic diffusion during plagioclase crystallization is proposed.
机译：CaAl-NaSi在斜长石晶体中的缓慢扩散可以详细保留斜长石的化学区带，而斜长石中的钙长石含量对熔体组成，压力和温度的强烈依赖性，使该矿物成为岩浆过程信息的重要来源。本文建立了分区晶体生长的数值模型。该模型基于具有对角交叉组分扩散项的多组分扩散方程，并说明了熔体晶体界面上的质量守恒和过冷控制的生长速率。该模型已应用于最近几次Bezymianny火山（堪察加半岛）喷发的斜长石边缘区带数据。我们表明，平衡增长模型不能解释岩浆上升期间自然观测到的斜长石的结晶。发达的非平衡模型再现了天然斜长石的分区，并允许岩浆上升的速率受到限制。自然和模拟分区的匹配表明，在15到20天内，上升幅度为100至50 MPa。从喷发到喷发，从50 MPa到地表的岩浆上升速率各不相同：2006年12月喷发的斜长石分区表明在不到1天的时间内上升到地表，而2000年3月和2007年5月喷发的斜长石分区可以用岩浆上升更好地解释。 30天以上）。在比较各个元素的扩散系数的基础上，提出了斜长石结晶过程中原子扩散的机理。

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