The dependence of alumina and silica contents on the extent of alteration of weathered ilmenites from Western Australia
The dependence of alumina and silica contents on the extent of alteration of weathered ilmenites from Western Australia
复制标题
氧化铝和二氧化硅含量对西澳大利亚风化钛铁矿蚀变程度的依赖性
DOI：
10.1180/minmag.1983.047.343.10
复制
发表时间：
1983
影响因子：
2.7
通讯作者：
K. Mason
中科院分区：
文献类型：
--
作者：
M. T. Frost;I. Grey;I. Harrowfield;K. Mason
本文用扫描电镜和电子探针研究了西澳大利亚三个地区蚀变钛铁矿中微量杂质铝和硅在共存相之间的分布。观察到Ti/（Ti + Fe）分数上的杂质水平的显著依赖性。对于Ti/（Ti + Fe）在0.45和0.60之间的组合物，即在亚铁钛铁矿和假金红石之间的组合物，杂质含量实际上与Ti/（Ti + Fe）无关，并且非常低（0.2wt. %的Al 2 O3。0.05重量% SiO2）。对于金红石和假金红石之间的组合物，有一个直接的相关性之间的杂质含量和蚀变相的钛含量。杂质水平随着Ti/（Ti+Fe）增加至约3 wt. %的Al 2 O3和lwt. %的SiO2，组成接近于TiO 2。因此，在钛铁矿蚀变的后期阶段，从周围环境中提取氧化铝和二氧化硅，并与蚀变产物共沉淀或吸附在蚀变产物上。所观察到的氧化铝和二氧化硅含量对蚀变程度的依赖性与早期提出的两阶段蚀变机制一致（Grey和Reid，1975）。
Abstract The distribution of the minor impurities, aluminium and silicon, between co-existing phases in altered ilmenite grains from three Western Australian localities has been investigated using SEM and electronmicroprobe analyses. A striking dependence of the impurity levels on the Ti/(Ti + Fe) fraction is observed. For compositions with Ti/(Ti + Fe) between 0.45 and 0.60, i.e. between ferrian-ilmenite and pseudorutile, the impurity content is virtually independent of Ti/(Ti + Fe), and is very low (0.2 wt. % Al2O3. 0.05 wt. % SiO2). For compositions between those of rutile and pseudorutile, there is a direct correlation between the impurity contents and the Ti content of the alteration phase. The impurity levels increase with increasing Ti/(Ti+Fe) to about 3 wt. % Al2O3 and 1 wt. % SiO2 for compositions close to TiO2. Thus during the latter stages of ilmenite alteration, alumina and silica are extracted from the ambient environment and are coprecipitated with, or adsorbed on to, the alteration products. The observed dependence of the alumina and silica contents on extent of alteration is consistent with a two-stage alteration mechanism earlier proposed (Grey and Reid, 1975).