Multicomponent diffusion in basaltic melts at 1350 °C
Multicomponent diffusion in basaltic melts at 1350 °C
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1350 °C 基础熔体中的多组分扩散
DOI：
10.1016/j.gca.2018.02.043
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发表时间：
2018
影响因子：
5
通讯作者：
Youxue Zhang
中科院分区：
文献类型：
--
作者：
Chenghuan Guo;Youxue Zhang
在SiO_2-TiO_2-Al_2O_3-FeO-MgO-CaO-Na_2 O-K_2 O八元系中，在1350 ℃和1GPa下进行了9次成功的扩散偶实验，研究了玄武岩熔体中的多元扩散。测量至少3次横穿以获得每个实验的扩散分布。通过对扩散偶实验的扩散曲线同时拟合，得到了1350 °C下的多元扩散矩阵。此外，为了更好地约束扩散矩阵和协调矿物溶解数据，矿物溶解实验在文献中和本研究的扩散偶实验，拟合在一起。扩散矩阵能很好地再现扩散偶和矿物溶解实验中扩散剖面的所有特征。从扩散矩阵的特征向量推断了扩散机制，表明网络形成者SiO2和Al 2 O3之间的扩散交换最慢，SiO2与其他氧化物组分的交换次之，特征向量仅大10%，然后二价氧化物组分和所有其它氧化物组分之间的交换是第三慢的，具有两倍最小的本征值特征值，则FeO + K2 O与所有其他氧化物组分的交换是第四慢的，特征值是最小特征值的5倍，然后MgO与FeO + CaO的交换是第三快的，特征值是最小特征值的6.3倍，则CaO + K2 O与所有其它氧化物组分的交换是第二快的，其本征值是最小本征值的7.5倍，Na_2 O与所有其他氧化物组分的交换最快，其特征值是最小特征值的31倍。最慢和最快的特征向量是一致的，在大多数文献中的简单系统。所得到的扩散矩阵被成功地应用于预测在玄武岩熔体矿物溶解过程中的扩散剖面。
Nine successful diffusion couple experiments were conducted in an 8-component SiO2–TiO2–Al2O3–FeO–MgO–CaO–Na2O–K2O system at ∼1350 °C and at 1 GPa, to study multicomponent diffusion in basaltic melts. At least 3 traverses were measured to obtain diffusion profiles for each experiment. Multicomponent diffusion matrix at 1350 °C was obtained by simultaneously fitting diffusion profiles of diffusion couple experiments. Furthermore, in order to better constrain the diffusion matrix and reconcile mineral dissolution data, mineral dissolution experiments in the literature and diffusion couple experiments from this study, were fit together. All features of diffusion profiles in both diffusion couple and mineral dissolution experiments were well reproduced by the diffusion matrix. Diffusion mechanism is inferred from eigenvectors of the diffusion matrix, and it shows that the diffusive exchange between network-formers SiO2and Al2O3is the slowest, the exchange of SiO2with other oxide components is the second slowest with an eigenvalue that is only ∼10% larger, then the exchange between divalent oxide components and all the other oxide components is the third slowest with an eigenvalue that is twice the smallest eigenvalue, then the exchange of FeO + K2O with all the other oxide components is the fourth slowest with an eigenvalue that is 5 times the smallest eigenvalue, then the exchange of MgO with FeO + CaO is the third fastest with an eigenvalue that is 6.3 times the smallest eigenvalue, then the exchange of CaO + K2O with all the other oxide components is the second fastest with an eigenvalue that is 7.5 times the smallest eigenvalue, and the exchange of Na2O with all other oxide components is the fastest with an eigenvalue that is 31 times the smallest eigenvalue. The slowest and fastest eigenvectors are consistent with those for simpler systems in most literature. The obtained diffusion matrix was successfully applied to predict diffusion profiles during mineral dissolution in basaltic melts.