Studies in Rare-earth and Radioactive Minerals of Pocos de Caldas in Brazil.

对点缀巴西盾的碳酸盐岩-碱性复合体进行了矿物调查和采集，分析了这些矿物的赋存状态、结构、化学成分和晶体结构之间的关系。稀土元素的富集是配合物的特征。研究结果总结如下：(1)在圣保罗以北200 km的Pocos de Caldas地区进行了调查。(a)在Serrote和Brigidas收集到一种称为“钙辉石”的岩石，其中含有大量的锆，可形成锆石或坏辉石。特别是坏辉石呈胶状结构，表明Zr富集于水溶液中的次生矿物中。(b)在Morro do Ferro，观察到特别富铁的侵入岩。这些岩石主要由磁铁矿组成。很明显，土壤中富集了放射性元素，如Th，这应该是由碱性岩石的绢云母化提供的，而碱性岩石的主要成分是辉石。(c)辉石岩是在不同地点观察到的碱性岩石的主要成分，或者是在这个地区周围形成岩脉的主要成分，其颗粒从细到粗不等。这意味着这些岩石有各种各样的构造。(2)目前在圣保罗以北400公里的Tapira和Araxa地区的调查中，在P、Ti和Nb矿床下方发现了一个新的非风化复合体。这种新的络合物对研究其组成矿物种类具有重要意义。此外，在闪辉岩中还发现了钙钛矿向锐钛矿逐渐转变的织构，这可能是风化过程的过渡阶段，或者还发现了Ca-Zr-Ti氧化物或含铝磷酸钙等稀有矿物。在圣保罗以北600公里的Catalao地区，有一些生产磷酸钙作为肥料的矿山。此外，大量稀土元素作为风化产物被富集到土壤中，因此，这些矿山的进一步开发需要组分矿物的基本资料。由GOIASFERTIL矿业公司提供，我们获得了大量的土壤钻孔岩心进行分析。(4)在圣保罗西南200 km的Jacupiranga附近的Cajati地区采集到了最新鲜的标本。乡村岩石主要由富钛辉石组成，称为“jacupirangite”。上述岩石和矿物是最有价值的，因为这样的标本在日本的地质环境中是找不到的。为了解释这类复合物形成的起源，需要进行持续的、更详细的研究。少

Survey and collection of minerals were carried out in the carbonatite-alkaline complexes which dot Brazilian shields, so as to analyze the relation among occurrence, texture, chemical composition or crystal structure of those minerals. Concentration of rare-earth elements is characteristic of the complexes. The results of the present research are summarized as follows:(1) Survey in the area of Pocos de Caldas, 200 km north of Sao Paulo.(a) A rock called"caldasite" containing much amount of Zr, which forms zircon or baddeleyite, was collected at Serrote and Brigidas. Particularly, the baddeleyite shows a colloform texture which suggests that Zr is concentrated in secondary minerals from water solution.(b) At Morro do Ferro, intrusive rocks particularly rich in Fe were observed. These rocks are composed chiefly of magnetite. It has become clear that radioactive elements such as Th are enriched in the soil, which is supposed to have been supplied by sericitization of alkalic rocks whose m … More ajor constituent is pyroxenes.(c) Pyroxenes, the main constituent of the alkalic rocks observed at various points or those forming the somma surrounding this area range from fine- to coarse-grained. It means a great variety of formations of these rocks.(2) In the present survey of the area of Tapira and Araxa, which lie 400 km north of Sao Paulo, a fresh non-weathered complex was found below the P, Ti and Nb ore deposits. Such a fresh complex is most important to investigate the constituent mineral species. Besides, a texture showing the gradual change from perovskite to anatase was observed by SEM in glimmerite which is supposed to indicate a transition stage in weathering, or rare minerals such as Ca-Zr-Ti oxides or Al-bearing Ca-phosphates were also identified.(3) In the area of Catalao, 600 km north of Sao Paulo there are some mines yielding Ca-phosphates as fertilizer. Besides, a great quantity of rare-earth elements are concentrated to the soils there as the weathering products, and therefore basic data of the constituent minerals are required for the more development of these mines. We obtained plenty of boring cores of the soils for analysis by the courtesy of the mining company, GOIASFERTIL.(4) In the area of Cajati near Jacupiranga, 200 km southwest of Sao Paulo the most fresh specimens of the complex were collected. The country rock is the one mainly consisting of pyroxene rich in Ti, which is called "jacupirangite".The above-described rocks and minerals are most valuable, since such specimens are not to be found in Japanese geological environments. Continuous,more detailed research is necessary to explain the origin of formation of such complexes. Less