The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts
The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts
复制标题
DOI：
10.1016/j.epsl.2018.01.023
复制
发表时间：
2018-04-01
影响因子：
5.3
通讯作者：
Dingwell, D. B.
中科院分区：
文献类型：
--
作者：
Kolzenburg, S.;Di Genova, D.;Dingwell, D. B.
硅酸盐熔体在地壳中的储存和运输以及它们在地球表面的就位几乎完全发生在低于液相线的温度下。在这些条件下，熔体在宽范围的冷却速率、变形速率和氧逸度（fO（2））下进行结晶。已知氧逸度影响岩浆和熔岩结晶的热力学和动力学。然而，它对亚液相线流变学的影响在很大程度上仍然是未知的。我们提出了第一个流变学表征结晶熔岩沿着自然冷却路径和变形速率，并在不同的fO（2）。具体而言，我们报告了两种结晶岩浆悬浮液的表观粘度测量结果：1）log fO（2）为-9.15（石英-铁橄榄石-磁铁矿缓冲液，QFM，-2.1）和2）在空气中。这些逸度跨越一系列的还原到氧化的条件有关的岩浆迁移和熔岩侵位。我们发现：1）在恒定冷却速率下的结晶导致岩浆悬浮液的表观粘度的准指数增加，直到它们达到它们的流变截止温度（T-cutoff），其中熔体有效地固化; 2）流变偏离和T-cutoff随着fO（2）的增加而增加; 3）增加fO（2）导致结晶速率降低。根据实验结果，并与以往的流变学等温研究进行比较，我们提出了fO（2）对天然岩浆和火山岩悬浮液动态流变学演化的影响的概括。我们进一步讨论了在管道和存储系统（如导管，堤坝和岩浆房）和熔岩流侵位过程中的岩浆运输的影响。(C)2018作者由爱思唯尔公司出版
Storage and transport of silicate melts in the Earth's crust and their emplacement on the planet's surface occur almost exclusively at sub-liquidus temperatures. At these conditions, the melts undergo crystallization under a wide range of cooling-rates, deformation-rates, and oxygen fugacities (fO(2)). Oxygen fugacity is known to influence the thermodynamics and kinetics of crystallization in magmas and lavas. Yet, its influence on sub-liquidus rheology remains largely uncharted.We present the first theological characterization of crystallizing lavas along natural cooling paths and deformation-rates and at varying fO(2). Specifically, we report on apparent viscosity measurements for two crystallizing magmatic suspensions 1) at log fO(2) of -9.15 (quartz-fayalite-magnetite buffer, QFM, -2.1) and 2) in air. These fugacities span a range of reduced to oxidized conditions pertinent to magma migration and lava emplacement. We find that: 1) crystallization at constant cooling-rates results in a quasi-exponential increase in the apparent viscosity of the magmatic suspensions until they achieve their rheological cut off temperature (T-cutoff ), where the melt effectively solidifies 2) the rheological departure and T-cutoff increase with increasing fO(2) and 3) increasing fO(2) results in decreased crystallization-rates. Based on the experimental results and by comparison with previous rheological isothermal studies we propose a generalisation of the effect of fO(2) on the dynamic rheological evolution of natural magmatic and volcanic suspensions. We further discuss the implications for magmatic transport in plumbing and storage systems (e.g. conduits, dikes and magma chambers) and during lava flow emplacement. (C) 2018 The Authors. Published by Elsevier B.V.