BARRETTO Pau サンパウロ大学, 宇宙地球物理学教室, 教授
FUJIMORI Kenkichi Instituto Astronomico e Geofisico, Universidade de Sao Paulo, Brasil, 宇宙地球物理学教室, 教授
AIKAWA Nobuyuki Faculty of Science, Osaka City University, 理学部, 助教授 (20047327)
OZAWA Tohru Faculty of Science, University of Tokyo, 理学部, 講師 (00011651)
HORIUCHI Hiroyuki Faculty of Science, University of Tokyo, 理学部, 助教授 (80029892)
BARRETTO Paulo M. de Cam Instituto Astronomico e Geofisico, Universidade de Sao Paulo, Brasil
|Budget Amount *help
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1988: ¥2,200,000 (Direct Cost: ¥2,200,000)
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
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