Results 1 - 10 of 447
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[en] The conclusions about the wolfeite mineral monocrystal study (Fe,Mn)2 (PO4) (OH), from the Bela Vista pigmatite, Minas Gerais State were described. Reticular Parameters were determined and through the reflection levels analysis the space group was confirmed. (L.M.J.)
[pt]Relatam-se, nesta comunicacao, as conclusoes a que se chegou atraves do estudo de mono-cristal do mineral wolfeita, (Fe, Mn)2 (PO4) (OH), proveniente do pegmatito de Bela Vista, Estado de Minas Gerais. Foram determinados os parametros reticulares e, atraves da analise dos indices das reflexoes presentes nos diversos niveis reciprocos fotografados, confirmou-se o grupo espacial citado na literatura. (Autor)
[en] The objective of this paper is to show the use of cintilometry in the delimitation of pegmatites of the region of Cristais, northeast of Ceara State. It is a part of the Project Litium-Ce and it receives a financial aid from FINEP. Four on-the-spot surveys have been made with a rectangules 5 x 15 m mesh on heterogeneous and little or not exploited pegmatite revealed on the surface by a residual mantle of milky quartz and slabs of muscovite. A cintilometer Saphyro Srat, model SPP-2 was used for readings in counts per second (c/s). Three of the surveys were performed on medium-sized pegmatites ( 5 - 15 m of width) and show that their measurement are in the 15-60 c/s range while those on the host rock (biotite-gneiss) vary from 70 to 130 c/s. One of the surveys was made over a pegmatitic dyke, with 1,5 meter width, in a sand-covered area of 1 meter, and it shows that the portion of the pegmatite may hardly by suggested, pointing out only at the southwest corner of the area the presence of biotite-gneiss through the increase in the readings. The cintilometry may be used on a more detailed scale in areas with superficial signs of the presence of pegmatites, in order to determine their position and to guide a superficial prospection. The low value reading (15 - 60 c/s) on the pegmatites are bound to be related to the absence of U and Th minerals and to the presence of a nucleus of quartz and albite, replacing largely the potassium feldspars. The reading in the 70 - 130 c/s range on the biotite-gneiss should be linked with the presence in their mineralogic composition of biotite muscovite, potassium feldspars and zircon. A sandy corer disguises the anomalies. (author)
[pt]Este trabalho tem por objetivo a utilizacao da cintilometria na delimitacao de pegmatitos da regiao de Cristais, nordeste do Ceara. Faz parte do Projeto Litio-CE e conta com o apoio financeiro da FINEP. Foram realizados quatro levantamentos de detalhe, com malha retangular 5 x 15 m, sobre pegmatitos heterogeneos pouco ou nao explorados, evidenciados em superficie por um manto residual de quartzo leitoso e placas de muscovita. Utilizou-se um cintilometro marca Saphymo Srat, modelo SPP-2, com leituras em choques por segundo (c/s). Tres dos levantamentos foram realizados sobre pegmatitos de porte medio (5-15m de espessura) e mostram que as medidas sobre os encaixante (biotita-gnaisse) as leituras estao na faixa de 70-130 c/s. Um dos levantamentos foi realizado sobre um dique pegmatitico com espessura de 1,5 m, em uma area com uma cobertura arenosa de 01 m e mostra que nao e possivel que se sugira a posicao do pegmatito, evidenciando apenas no canto sudoeste da area a presenca do biotita-gnaisse pelo aumento das leituras. A cintilometria pode ser utilizada em escala de detalhe em areas com evidencias superficiais de pegmatito com o objetivo de determinar sua posicao e orientar a prospeccao superficial. As leituras baixas (15-60 c/s) sobre os pegmatitos devem estar relacionadas a ausencia de minerais de U e Th e a presenca do nucleo de quartzo e da albita, substituindo em grande proporcao os feldspatos potassicos. As leituras na faixa de 70-130 c/s sobre o biotita-gnaisse devem estar relacionadas a presenca em sua composicao mineralogica de biotita, muscovita, K-feldspato e zircao. Uma cobertura arenosa mascara as anomalias. (autor)
[en] Conclusions through the mono-crystal of the arrojadite mineral study Na2 (Fe,Mn)5 (PO4)4, from Bela Vista pegmatite, Governador Valadares, Minas Gerais State were related. Reticular parameters were evaluated and through the reflection levels analysis, present in the different reciprocal levels photographyed, a space group C2/C were found, different from the literature, c2/m. (L.M.J)
[pt]Relatam-se, nesta comunicacao, as conclusoes a que se chegou atraves do estudo de mono-cristal do mineral arrojadita, Na2(Fe,Mn)5(PO4)4, proveniente do pegmatito de Bela Vista, Municipio de Governador Valadares, Estado de Minas Gerais. Foram determinados os parametros reticulares, e, atraves da analise dos indices das reflexoes, presentes nos diverso niveis reciprocos fotograficos, chegou-se ao grupo espacial C2/c, diverso daquele citada na literatura, C2/m. (Autor)
[en] Wadi Abu Had area is located at the northern part of the Eastern Desert of Egypt. It covers about 55 km2 of the crystalline basement rocks stretching between latitudes 28o 15'- 28o 25' N and longitudes 32o 25' - 32o 35' E. Abu Had younger granites are fertile (uraniferous) granites as they possess U-contents greater than 11 ppm. Their associated pegmatites show higher U-contents than those of granitoid rocks and hosting secondary uranium minerals. Numerous unzoned and zoned pegmatite pockets are associated with the marginal parts of granodiorite and within younger granites. Zoned pegmatites are the most radioactive ones. They are composed of extremely coarse-grained milky quartz core, intermediate zone of mica and wall zone of feldspars. An alteration zone with secondary uranium minerals (uranophane and beta-uranophane) is found at the contact between quartz core and the intermediate zone.
[en] Pseudomorphism of secondary uranium minerals with uraninite are investigated in detail. On the basis of chemical analysis, microprobe analysis, debayegrams, electron-microscopic investigations, IR-apectroscopy, thermal analysis it is established that macroscopically homogeneous pseudomorphism is in reality polycomponent. The main phase has Si, U, Pb, Th, Y composition and it is characterized by a set of interplane distances corresponding to minerals of the isomorphous challonite-cheralite-monazite series. Secondary phases are presented diagnosed before as thorogummite and kasolite. UO22+, SiO44-, OmHn are main components of pseudomorphism judging by IR-spectra
[en] This paper reports on lithium metallogeny in geological time. The geochronological analysis was conducted on the basis of data on 71 lithium deposits distributed globally. These deposits contain almost all Li resources, which are industrially significant and of potential interest in terms of the economy. It was established that these deposits were formed in different geological epochs, from the Late Mesoarchean to the Holocene. The distribution of their resources on the scale of geological time is distinctly discrete. In the Kenoran, Columbian, and Rodinian supercontinent cycles, only pegmatite deposits of lithium were formed. In the Pangean cycle, the main resources are also attributed to pegmatite deposits, but some of them are concentrated in lithium–fluorine rare-metal granites. In the incomplete Amasian cycle, salars of geodynamically active areas play a main role in the resource base; the epithermal stratiform deposits, pegmatites, and lithium-fluorine granites are of much less significance.
[en] Fluid Inclusion studies of mineralization process have been carried out on Lampung pegmatite. The pegmatite veins contain some radioactive minerals and its associate minerals of pyrite, magnetite, and molybdenite. Those occurrences have to be a prove of the existent of uranium and base metals bearing mineralizing solution within the cretaceous granitic batholith of Lampung. The goal of the study is to understand the mechanism of uranium mineralizing solution deposition by observing and measuring freezing and homogenization temperatures of the inclusion using micro thermometers apparatus. Six fluid inclusions includes primary and secondary types have been identified within 20 pegmatite samples. Five groups of the homogenization temperatures measured were (25.9-31.5)0c, (208.4-276.3)0c, (234.2-296.0)0c, (256.6-379.4)0c, and (231.4-314.2)0c. The fluids compose of silicate melt, water, and carbon dioxide gas. Maximum salinity of the aqueous fluids is relatively high is about 18 % (wt) NaCl. Trapping temperatures of the mineralizations are around (231.4-314.2)0c
[en] The study of the elements in 31 accessory apatites in pegmatite field illustrates the usefulness of PIXE in the measurement of elements in rocks and minerals. Based on the elemental composition results, the behavior of REE and other trace elements within the pegmatite system is discussed, the concentration distribution of the substitution elements in apatite to their locations in the field and to the geochemical characteristics of the K-feldspars. The average cK/cRb value for the core margin K-feldspars is considered as a reliable indicator of the general level of the fractionation by the pegmatite. Consequently the element concentration distribution trend due to fractionation may be illustrated by a plot of it against the cK/cRb ratio