Compositional dependence of the rheology of halogen (F, Cl) bearing aluminosilicate melts
Compositional dependence of the rheology of halogen (F, Cl) bearing aluminosilicate melts
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DOI：
10.1016/j.chemgeo.2012.09.020
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发表时间：
2013-05-27
期刊：
影响因子：
3.9
通讯作者：
Webb, S. L.
中科院分区：
文献类型：
--
作者：
Baasner, A.;Schmidt, B. C.;Webb, S. L.
用微渗透和平行板技术研究了三种含不同含量氟（F）和氯（Cl）或两者的熔体组合物的流变性。测定了熔体的热容和构型熵。观察到的粘度范围在10（5.5）和10（13）Pa s之间。在1个大气压的炉中，在1523和1923 K之间的温度下，使用氧化物和碳酸盐化合物的熔体。使用卤化物和含卤素的铵化合物掺入卤素。第一种组合物是过铝的Na 2 O-CaO-Al 2 O3-SiO2熔体（ANCS），其表观NBO/T类似于-0.08，第二种组合物是过碱性的Na 2 O-CaO-Al 2 O3-SiO2熔体（NACS）（NBO/T =类似于0.24），其是六方晶系的类似物，第三种组合物是无铝的Na 2 O-CaO-SiO2熔体（NCS）（NBO/T类似于0.68）。研究了5种含卤素ANCS熔体（含1.10mol%Cl和1825mol%F）、6种含卤素NACS熔体（含138mol%Cl和2.58mol%F）和3种含卤素NCS熔体（含2.15mol%Cl和2.04mol%F）的粘度，发现氟降低了所有组成的粘度，但强度不同。内插到1摩尔%，F在过铝熔体（ANCS）中使粘度降低0.31 +/- 0.08对数单位，在过碱性熔体（NACS）中降低0.57 +/- 0.11对数单位，在NCS熔体中降低0.47 +/- 0.14对数单位。内插到1摩尔%，氯降低粘度0.57 +/- 0.13对数单位的过铝熔体，但增加粘度0.87 +/- 0.10对数单位的过碱性熔体。由于向无铝熔体中加入氯，对粘度没有可测量的影响。在过铝熔体中，F和Cl的作用几乎是线性叠加的，使熔体粘度降低;在过碱性熔体中，Cl使熔体粘度增加，而F使熔体粘度降低，如果两者都存在，则两种作用似乎相互平衡，结果是加入等量（mol%）的F和Cl时，熔体粘度没有变化。这些结果是从卤素含量比以前大多数研究更高和更多样化的样品中获得的，因此它们适用于两种元素的广泛浓度范围，并应考虑到建模岩浆过程。(C)2012爱思唯尔有限公司版权所有。
The rheology of three melt compositions containing different amounts of fluorine (F) and chlorine (Cl) or both was investigated with micropenetration and parallel-plate techniques. The heat capacity and configurational entropy of the melts were also determined. The observed viscosity range is between 10(5.5) and 10(13) Pa s. The melts were produced in a 1 atm furnace at temperatures between 1523 and 1923 K using oxide and carbonate compounds. The halogens were incorporated using halides and halogen-bearing ammonium compounds. The first composition is a peraluminous Na2O-CaO-Al2O3-SiO2 melt (ANCS) with an apparent NBO/T of similar to-0.08, the second composition is a peralkaline Na2O-CaO-Al2O3-SiO2 melt (NACS) (NBO/T = similar to 0.24), which is an analogue for phonolites, and the third is an aluminium-free Na2O-CaO-SiO2 melt (NCS) (NBO/T of similar to 0.68). Five halogen-bearing ANCS melts with up to 1.10 mol% Cl and 1825 mol% F, 6 halogen-bearing NACS melts with up to 138 mol% Cl and 2.58 mol% F and 3 halogen-bearing NCS melts with up to 2.15 mol% Cl and 2.04 mol% F were investigated in this study.Fluorine was found to decrease the viscosity for all compositions, but not with equal strength. Interpolated to 1 mol%, F decreases the viscosity by 0.31 +/- 0.08 log units in the peraluminous melt (ANCS), 0.57 +/- 0.11 log units in the peralkaline melt (NACS) and 0.47 +/- 0.14 log units in the NCS melt.The effect of Cl on rheology depends on the melt composition. Interpolated to 1 mol%, Cl decreases the viscosity by 0.57 +/- 0.13 log units in the peraluminous melt, but increases viscosity by 0.87 +/- 0.10 log units in the peralkaline melt. There is no measurable effect on viscosity due to the addition of chlorine to the aluminium-free melt. In the peraluminous melts the effects of F and Cl add almost linearly to decrease viscosity.In the peralkaline melts, Cl increases the viscosity while F decreases it, if both are present, the effects appear to balance each other; resulting in no change in viscosity for the addition of equal amounts (in mol%) of fluorine and chlorine. The results were obtained from samples with higher and more varied halogen contents than in the most previous studies, therefore they hold true for a wide range of concentrations of both elements and should be taken into account for modelling magmatic processes. (C) 2012 Elsevier B.V. All rights reserved.