Mineralogical Studies of Carbonatites.

对碳酸盐岩和碱性岩石的组成矿物的结构和化学成分进行了研究，主要使用了Monbusho国际科学研究计划“巴西碱性杂岩的稀土和放射性矿物研究”(首席研究员：Masayasu Tokonami教授)获得的样品。主要内容是观察到以下现象：(1)辉石与碳酸盐岩接触处的变质作用使辉石转变为蛇纹石；(2)碱金属和碱土金属离子不仅从碳酸盐中而且从硅酸盐、氧化物等中显著地浸出；(3)独居石、红柱石等磷酸盐矿物中稀土元素的特征浓度，以及由于风化作用而进入方晶石、金刚石、高晶石等的浓度。在这个项目中，我们还为微区X射线衍射技术的发展做出了贡献。应用这种方法，我们可以在不破坏样品的情况下，识别出最小为5-10微米的晶相。此外，它还可以确定在结构中观察到的不同晶相之间的晶体取向关系。因此，该方法将有助于通过光学显微镜、扫描电子显微镜等联合观察来阐明碳质岩浆的固化及其与碱性岩石的变质作用、风化过程等各种复杂的成矿过程。

Studies on textures and chemical conpositions of constituent minerals of carbonatites and alkaline rocks were performed mainly using specimens obtained by the Monbusho International Scientific Research Program entitled "Studies on rare-earth and radioactive minerals of alkaline complexes in Brasil" (Head Investigator : Professor Masayasu TOKONAMI). Main subjects are the observations of following phenomena : (1) alteration of pyroxene into serpentine by a metamorphism at the contact of jacupirangite with carbonatite, (2) remarkable leaching phenomena of alkaline metal and alkaline-earth metal ions not only from carbonates but also from silicates, oxides, etc., (3) characteristic concentrations of rare-earth elements in such phosphate minerals as monazite, cheralith, etc., and concentrations into rhabdophane, crandallite, goyazite, etc. as a result of weathering.In this project, we also contributed to the development of a microarea X-ray diffraction technique. By applying this method, we can identify minerals up to the minimum of 5-10 mum crystalline phases without destroy of the specimen. Furthermore, it is possible to determine the crystallo-graphic orientation relationship among different crystalline phases which are observed in textures.Thus, this method will contribute to clarify various complicated mineralization processes such as solidification of carbonaceous magmas and its metamorphism with alkaline rocks, weathering processes, etc., by combined observations of an optical microscope, scanning electron microscope, etc..