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

碳酸盐岩是一种以碳酸盐矿物为主要成分的火成岩侵入岩。利用本基金购买的偏光显微镜阴极发光（CL）附着物，研究了巴西南部碳酸盐精细矿物结构中微量元素的分布。碳酸盐矿物、碳酸盐中的磷灰石等均存在Mn^<2+>和REE（稀土元素）的CL。将可见光分光计通过光学显微镜应用于CL光，成功测定了CL发射波长。含有100 ~ 5000ppm Mn^<2+>的方解石显示黄色CL，含有微量Mn^<2+>的白云石显示橙黄色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使得区分它们非常容易。对白云石在方解石中的溶蚀结构进行了清晰、快速的观察。碳酸盐中的磷灰石也发出白色到蓝色的CL光。它们的活化剂是Mn^<2+>和REE离子，如Eu^<2+>和Sm^<3+>。利用电子探针微量分析仪（EPMA）对碳酸盐岩薄片中的组成矿物进行了定量分析，准确度达到百分比级。用偏光显微镜对矿物种类进行了测定。利用同步辐射x射线进行微束x射线荧光分析，绘制了薄片中微量元素的二维分布。这表明锰和铁在白云岩中的分布比在方解石中的分布要多。半定量分析表明，白云石颗粒中Mn含量约为5000 ppm。方解石和白云岩中Mn - k边XANES的化学位移表明，在这些菱形碳酸盐晶体中Mn^<2+>取代了Ca^<2+>或Mg^<2+>。痕量稀土的分布行为研究

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