天然富铁黑云母中Fe^(2+)、Fe^(3+)的有序——无序及其岩石学意义

The Order-Disorder of Fe^(2+) and Fe^(3+) in Natural Iron-Rich Biotite and Its Significance for Petrology

通过对天然富铁黑云母的化学成分及穆斯堡尔谱的分析测试,精确测定了Fe^(2+)、Fe^(3+)在黑云母八面体晶位M1、M2中的占位率,提出了描述铁的有序度参数OR及其物理意义。运用二元固溶体理想模型建立了OR值与平衡温度的关系图解及函数表达式。简略阐述了黑云母铁的有序度参数OR在花岗岩成岩作用研究中的应用。

This paper accurately determines the occupancy ratios of Fe^(2+) and Fe^(3+) in octahedral sites M1 and M2 of iron-rich biotites, respectvely, by means of measuring their compositions, Mossbauer spectra. A new parameter OR is suggested to describe the ordering of iron in iron-rich biotites. OR is an intense variable which depends on the equilibrium temperature. The functional relation between OR and the equilibrium temperature is eatablished by using the idealized model of binary solid solution. The higher OR values represent the higher ordering of iron ions in the octahedral sites of iron-rich biotite while the Iower equilibrium temperature keeps the structural states. It is convenient and effective to utilize OR of iron-rich biotite to explain petrogenic evolution of granite complex and its cooling history with petrological studies.