一种计算NaAlSi_3O_8熔体粘度的理论方法  

A Theoretical Method to Calculate the Viscosity of NaAlSi 3O 8 Melt

作　　者：朱永峰[1] 赵永超[1] 郭光军[1] 

机构地区：[1]北京大学地质学系

出　　处：《岩石学报》1997年第2期173-179,共7页Acta Petrologica Sinica

基　　金：北京大学自然科学基金

摘　　要：硅酸岩熔体的结构特征是制约熔体粘度的主要因素，熔体结构的变异是其中粘流作用发生的原因，化学成分对熔体粘度的控制是通过改变熔体结构而实现的。ＳｉＯ２熔体中仅存在Ｓｉ－Ｏ键，而ＮａＡｌ－Ｓｉ３Ｏ８熔体中存在Ｓｉ－Ｏ键，Ａｌ－Ｏ键和Ｎａ－Ｏ键，Ｎａ－Ｏ键在熔体结构中通过Ｏ与Ｓｉ－Ｏ键相联结，并且使与之相联的Ｓｉ－Ｏ键的键强变弱。因此，熔体结构单元中与Ｎａ－Ｏ键相联结的Ｓｉ－Ｏ键最易断开，并因此导致流变作用的发生。文中计算了不同温度条件下ＮａＡｌＳｉ３Ｏ８熔体中Ｓｉ－Ｏ键的键强，以ＳｉＯ２熔体中的Ｓｉ－Ｏ键的键强和ＳｉＯ２熔体的粘度为标准，建立了计算了ＮａＡｌＳｉ３Ｏ８熔体粘度的理论模型。It is believed that the viscosity of silicate melt dependents on the characters of its chemical composition, however, the change of melt structure is the reason for the change of viscosity. The relationship between viscosity and chemical composition, actually, is the reflection of the relationship between viscosity and melt structure. There is only Si-O bond in SiO 2 melt, and in NaAlSi 3O 8 melt exist Si-O, Al-O, and Na-O bonds. In the structure of NaAlSi 3O 8 melt, Na-O bond associated with Si, which can low the strength of Si-O bond, in the result, the Si-O bond associated with Na-O bond will be weaker than that of the separate Si-O bond, therefore, NaAlSi 3O 8 melt has a lower viscosity than SiO 2 melt. Based on this principle, we designed a model for the viscosity calculation of NaAlSi 3O 8 melt, which can give a good result for NaAlSi 3O 8 melt at suitable geological temperature.

关 键 词：粘度 NaAlSi3O8熔体 熔体结构 硅酸岩 岩石熔体 

分 类 号：P588.121[天文地球—岩石学] P588.11[天文地球—地质学]