The distribution of elements of the igneous carbonate rock affected by alteration

碳酸盐岩是以碳酸盐矿物为主要成分的火成岩。用偏光显微镜阴极发光(CL)仪研究了巴西南部碳酸盐岩矿物结构中微量元素的分布。在碳酸盐矿物、磷灰石等碳酸盐矿物中观察到了Mn~(2+)、Lt~(2+)和稀土元素的化学发光。将可见光光谱仪应用于化学发光，通过光学显微镜，成功地测定了化学发光波长。方解石含100~5000ppm的Mn2+呈黄色CL，白云石含微量的Mn2+呈橙黄色CL，虽然在光学偏光显微镜下几乎不可能区分方解石和白云石的颗粒，但CL很容易区分它们。白云石在方解石中的出溶结构观察得非常清楚和迅速。碳酸盐岩中的磷灰石也会发出白色到蓝色的CL光。它们的活化剂为Mn^&lt；2+&gt；和稀土离子Eu^&lt；2+&gt；和Sm^&lt；3+&gt；用电子探针显微分析仪(EPMA)对碳酸盐岩薄片中的组成矿物进行了百分精度的定量分析。并用偏光显微镜测定了矿物的种类。利用同步辐射X射线微束X射线荧光分析技术绘制了微量元素在薄片上的二维分布图。这说明锰和铁在白云石中的分布比在方解石中的分布要多。半定量分析表明，白云岩颗粒中的锰含量约为5000ppm。方解石和白云石中MnK边的XANES化学位移表明，这些菱形碳酸盐晶体中的Ca^&lt；2+&gt；或Mg^&lt；2+&gt；；痕量稀土元素分布行为的研究

Carbonatite is the igneous intrusive rock whose main components are carbonate minerals. The distribution of the trace elements in fine mineral texture of the carbonatites from southern Brazil was investigated by means of cathodoluminescence (CL) attachment for polarized microscopy, which was purchased by this grant. The CL of Mn^<2+> and REE (rare earth elements) was observed in carbonate minerals, apatite and others in carbonatites. The spectrometer for visible light was applied for CL light through optical microscope, and results in the successful determination of the wavelength of CL emission. Calcite that includes 100 - 5000 ppm of Mn^<2+> shows yellow CL and dolomite, which also contains trace amount of Mn^<2+>, shows orange yellow CL.Although it is almost impossible to distinguish between the grains of calcite and dolomite under optical polarized microscope, CL makes to differentiate them very easy. The exsolution texture of dolomite in calcite was observed very clearly and quickly. Apatites in carbonatite also emit white to blue CL light. Their activators are found to be Mn^<2+> and REE ions such as Eu^<2+> and Sm^<3+>. The quantitative analyzes with the acuracy of percentage order were made using Electron Probe Micro Analyzer (EPMA) for constituent minerals in the carbonatite thin section. Also polarized microscope was used for the determination of the mineral species. The microbeam X-ray fluorescence analysis using the synchrotron radiation X-ray was used for mapping of the two-dimensional distribution of trace elements in thin section. This revealed Mn and Fe distributes in dolomite more than in calcite. Semi-quantitative analysis shows about 5,000 ppm content of Mn in dolonite grains. the chemical shift of XANES of Mn K-edge in calcite and dolomite suggests that Mn^<2+> substitutes in Ca^<2+> or Mg^<2+> sites in these rhombohedral carbonate crystals. The studies of behavior of distribution of trace rare earth