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Doctoral Thesis
DOI
10.11606/T.44.1988.tde-19062015-143258
Document
Author
Full name
Ana Helena Pacheco Moreira
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1988
Supervisor
Committee
Valarelli, Jose Vicente (President)
Candia, Maria Angela Fornoni
Delbove, Francois
Figueiredo, Mario Cesar Heredia de
Guttler, Rainer Aloys Schultz
Title in Portuguese
Síntese de leucita, sanidina e vidro sanidínico a 930 - 1030°C e 2kb: coeficientes de partição de Rb, Ca, Sr e Ba entre essas fases e solução hidrotermal de KCl. Aplicações geológicas
Keywords in Portuguese
Mineralogia
Petrologia
Abstract in Portuguese
Realizaram-se quatro séries de sínteses (2Kbar de pressão total): sanidina a '930 GRAUS'C, leucita a '930 GRAUS'C e '1030 GRAUS'C e de vidro sanidínico a '1030 GRAUS'C, em contato com solução hidrotermal contendo KCl e traços de cloretos de metais alcalinos e alcalino-terrosos marcados com seus isótopos radiativos ('ANTPOT. 86 Rb','ANTPOT. 45 Ca', 'ANTPOT. 85 Sr', 'ANTPOT. 133 Ba'). Em cada série de experimentos, a titulação total da solução foi mantida constante e as concentrações elemento traço/potássio variaram de '10 POT. -1' a '10 POT. -6'. Foram estabelecidos os vários coeficientes de distribuição dos oligoelementos entre cristais e solução entre vidro (magma) e solução, dentro dos critérios de idealidade (Leis de Henry e Berthelot-Nernst). Esses coeficientes experimentais foram relacionados para obtenção indireta de coeficientes de partição dos elementos trações entre sanidina e "magma sanidínico" e entre leucita e esse mesmo "magma". Com essas aproximações concluimos que: a) durante a cristalização da leucita, quantidades importantes de Ba e pouco menos importantes de Rb são fixadas na leucita, empobrecendo o líquido residual nesses elementos. O Sr e o Ca apresentam comportamento oposto. b) durante a cristalização da sanidina, o Ba é ainda mais fixado nessa fase, seguido de perto pelo Sr. O Rb concentra-se ligeiramente mais no líquido (vidro) e o Ca, segue o mesmo comportamento, porém, de forma marcante. Os dados experimentais acham-se em perfeito acordo com a história magmática dos complexos alcalinos de Tanguá e de Itaúna no Estado do Rio de Janeiro.
Title in English
Not available.
Keywords in English
Not available.
Abstract in English
This work shows results of hydrothermal experiments to determine the distribution coefficients of alcali and alcaline earth elements in trace concentrations between sanidine and liquids of same composition and between leucite and liquid. At 2 kb pressure and 930°C for sanidine, 930° and 1030°C for leucite and 1030°C for a melt of sanidine composition the concentration of trace elements (TE) in the coexisting potassium bearing aqueous fluid phase was varied between '10 POT.-1' to '10 POT. -6' mole to one mol of 'K POT.+'. By use of radioactive tracers ('Rb POT.86', 'Ca POT. 45', 'Sr POT. 85', 'Ba POT. 133') the concentrations in TE of the aqueous phase, the solids and melts has been determined. Under the assumption of Henry-and Bertholet-Nernst law behavior for the trace elements the following distribution coefficient between solids and aqueous fluid phase (HS) and melt and aqueous fluid phase (HS) have been determined ('KD POT. Solid-HS' = TE/'K POT +'; 'KD POT. Melt-HS' = TE/'K POT. +'). Under the assumption of equal bahaviour of trace elements in the aqueous fluid phase of the experiments with solids and with melts coexisting, the division of the distribution coefficients of 'KD POT. solid-SH' and 'KD POT. melt-SH' gives directly the distribution coefficient 'KD POT. solid-melt'. This indirect method will give a good approximation of the behaviour of TE between a melt and crystallising solids. These aprotimations lead to following conclusions: a) during the crystallisation of leucite, this phase incorporates large quantities of Ba and Rb, depleting the residual melt in those elements. Sr and Ca, on the other hand are enriched in the residual melt. b) the crystallisation of sanidine depletes even more the residual melt in Ba, Sr shows similias behaviour, Rb and Ca, however, are enriched in the residual melt phase. The application of these data to the igneous history of the alkaline rocks de Tanguá and Itaúna, state of Rio de Janeiro showed good correspondence between natural observation and experimental work.
 
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Publishing Date
2015-06-22
 
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