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

巴西波科斯迪卡尔达斯稀土和放射性矿物研究。

• 批准号: 63043014
• 负责人: TOKONAMI Masayasu
• 金额: $ 1.41万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Overseas Scientific Research
• 财政年份: 1987
• 资助国家: 日本
• 起止时间: 1987 至 1988
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63043014/
• 关键词: Rocks and Minerals in Brazil; Pocos de Caldas; Alkalic Rock; Carbonatite; Rare-earth Mineral; Mineral Texture; Weathered Soil; 燐・チタン鉱床

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

对散布在巴西地幔中的碳酸盐岩-碱性杂岩中的矿物进行了调查和采集，以分析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。稀土元素的集中是该络合物的特征。(1)在圣保罗以北200公里的Pocos de Caldas地区进行了调查。(A)在Serrote和Brigidas采集到了一种含有大量锆石或斜方铅矿的“方解石”岩石。具体地说，斜方辉石具有胶体结构，表明水溶液中的次生矿物中有大量的锆质元素。(B)在Morro do Ferro，发现了特别富Fe的侵入岩。这些岩石主要由磁铁矿组成。很明显，Th等放射性元素在土壤中富含，这被认为是由碱性岩石的绢云母化提供的，这些岩石的m…更主要的成分是辉石。(C)辉石是在不同地点观察到的碱性岩石或形成本区周围索玛的辉石的主要成分，从细粒到粗粒不等。这意味着这些岩石的建造种类繁多。(2)在圣保罗以北400公里的Tapira和Araxa地区的调查中，在P、Ti和Nb矿床下面发现了一个新的未风化杂岩。这种新鲜的杂岩对研究组成矿物种类是最重要的。此外，在闪锌矿中，扫描电子显微镜观察到钙钛矿逐渐向锐钛矿转变的结构，这可能表明风化作用的过渡阶段，也发现了钙-锆-钛氧化物或含铝钙磷酸盐等稀有矿物。(3)在圣保罗以北600公里的卡塔劳地区，有一些生产钙磷酸盐作为肥料的矿山。此外，大量的稀土元素作为风化产物聚集在土壤中，因此这些矿山的进一步开发需要组成矿物的基础数据。在矿业公司GOIASFERTIL的帮助下，我们获得了大量的土壤钻探岩心进行分析。(4)在圣保罗西南200公里处贾佩皮兰加附近的卡贾蒂地区，收集了最新的复合体标本。围岩主要由富含钛的辉石组成，被称为“碧玉”。上述岩石和矿物是最有价值的，因为在日本地质环境中找不到这样的标本。有必要进行持续的、更详细的研究，以解释这种复合体的形成原因。较少