THE COMPRESSIBILITY OF SILICATE LIQUIDS CONTAINING FE2O3 AND THE EFFECT OF COMPOSITION, TEMPERATURE, OXYGEN FUGACITY AND PRESSURE ON THEIR REDOX STATES
THE COMPRESSIBILITY OF SILICATE LIQUIDS CONTAINING FE2O3 AND THE EFFECT OF COMPOSITION, TEMPERATURE, OXYGEN FUGACITY AND PRESSURE ON THEIR REDOX STATES
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DOI：
10.1007/bf00307328
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发表时间：
1991-01-01
影响因子：
3.5
通讯作者：
CARMICHAEL, ISE
中科院分区：
文献类型：
--
作者：
KRESS, VC;CARMICHAEL, ISE
氧化硅酸盐液体中的超声波纵向声速表明，在 1 bar 下，富铁碱金属、碱土金属和天然硅酸盐熔体组合物中 Fe2O3 的偏摩尔体积的压力导数是相同的。 多组分硅酸盐液体的 dV/dP 可表示为部分摩尔常数加上 Na2O-Al2O3 混合的正过量项的线性组合。 FeO 和 Fe2O3 组分的偏摩尔性质允许扩展 Sack 等人的经验表达式。 (1980) 允许计算天然硅酸盐液体中的铁氧化还原平衡作为成分、温度、f(O2) 和压力的函数；附录中提供了更正式的热力学表达式。 固定氧含量的天然硅酸盐熔体的预测平衡 f(O2) 与压强-温度空间中亚稳态组合铁橄榄石+磁铁矿+β-石英 (FMQ) 定义的平衡 f(O2) 非常相似。 硅酸盐熔体最初在 3 GPa 和 FMQ 下达到平衡，在其封闭系统上升过程中将保持在约 0.5 log10 单位的 FMQ 范围内。 因此，对于接近氧气的岩浆，缺乏晶体的原始玻璃熔岩中的铁氧化还原平衡代表了其源区相对氧化态的极好探针。
Ultrasonic longitudinal acoustic velocities in oxidized silicate liquids indicate that the pressure derivative of the partial-molar volume of Fe2O3 is the same in iron-rich alkali-, alkaline earth- and natural silicate melt compositions at 1 bar. The dV/dP for multicomponent silicate liquids can be expressed as a linear combination of partial-molar constants plus a positive excess term for Na2O-Al2O3 mixing. Partial-molar properties for FeO and Fe2O3 components allow extension of the empirical expression of Sack et al. (1980) to permit the calculation of Fe-redox equilibrium in a natural silicate liquid as a function of composition, temperature, f(O2) and pressure; a more formal thermodynamic expression is presented in the Appendix. The predicted equilibrium f(O2) of natural silicate melts, of fixed oxygen content, closely parallels that defined by the metastable assemblage fayalite+magnetite+beta-quartz (FMQ), in pressure-temperature space. A silicate melt initially equilibrated at 3 GPa and FMQ, will remain within approximately 0.5 log10 units of FMQ during its closed-system ascent. Thus, for magmas closed to oxygen, iron-redox equilibrium in crystal-poor pristine glassy lavas represents an excellent probe of the relative oxidation state of their source regions.