碳酸盐矿物阴极发光性的控制因素分析

Controlling factors of cathodeluminescence of carbonate minerals

关键词:  碳酸盐矿物  阴极发光  Mn²⁺/Fe²⁺值

Key words:  carbonate mineral  cathodeluminescence  Mn²⁺/Fe²⁺ ratio

摘要:

碳酸盐矿物的阴极发光性主要受其Mn²⁺和Fe²⁺含量,以及Mn²⁺/Fe²⁺值的综合控制,但Mn²⁺/Fe²⁺值的控制作用强一些。研究中充填裂缝的方解石胶结物样品主要采自北京西山寒武系和奥陶系的碳酸盐岩地层中。此外,还从北京石花洞中采集了现代溶洞的石笋样品。样品的阴极发光强度可分为不发光、暗、中等和亮,阴极发光颜色也相应地分为不发光、橙红色、橙黄色和亮黄色。通过对野外露头样品进行电子探针研究,测定其中的Mn²⁺和Fe²⁺的含量,并结合样品的阴极发光颜色和强度,得出Mn²⁺含量要在0.01%以上,Fe²⁺含量至少在0.8%以下,Mn²⁺/Fe²⁺在0.05以上,方解石胶结物才能发光。经研究发现,充填裂缝中方解石胶结物的阴极发光性与Mn²⁺和Fe²⁺含量,以及Mn²⁺/Fe²⁺值之间存在如下关系:不含Mn²⁺,Fe²⁺微量,Mn²⁺/Fe²⁺为0时,不发光;0.052+/Fe²⁺<0.2时,发光强度暗,发光颜色为橙红色;0.22+/Fe²⁺<2时,发光强度中等,发光颜色为橙黄色;Mn²⁺/Fe²⁺>2时,发光强度亮,发光颜色为亮黄色。

Abstract:

Cathodelum inescence of carbonate minerals tends to be constrained by the Mn²⁺ and Fe²⁺ contents and Mn²⁺ /Fe²⁺ ratios.In this study,the calcite cement samples were mostly collected from the Cambrian and Ordovician carbonate rock strata in the Western Hills,Beijing.The cathodeluminescence intensities of these samples can be divided into nonluminous,weak,moderate and bright types.Correspondingly,the cathodeluminescence colours include nonluminescence,salmon,orange and bright yellow colours.The correlation of the cathodeluminescence intensities and colours based on the microprobe analysis,and the Mn²⁺ and Fe²⁺ contents and Mn²⁺ /Fe²⁺ ratios has led us to the following conclusions.The calcite cement exhibits no luminescence when there is no Mn²⁺ or only a trace amount of Fe²⁺ in the samples,and the Mn²⁺/Fe²⁺ ratios is 0.The calcite cement exhibits a weak luminescence and salmon when the Mn²⁺/Fe²⁺ ratios range between 0.05 and 0.2.The calcite cement exhibits a moderate luminescence and orange when the Mn²⁺/Fe²⁺ ratios range between 0.2 and 2.The calcite cement exhibits a bright luminescence and bright yellow when the Mn²⁺/Fe²⁺ ratios go up to more than 2.