Turmalinas pegmatíticas y metasomáticas de
Sierra Albarrana, Córdoba (España).
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1992
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Instituto Geológico y Minero de España (Madrid)
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Abstract
Se describen las principales características de las turmalinas pegmatíticas de Sierra Albarrana, distinguiendo dos poblaciones: las que forman parte integral de estos cuerpos originadas desde la fase silicatada y acuosa y las generadas por el metasomatismo de la fase acuosa en el encajante. Composicionalmente, se caracterizan por no contener Li y pertenecer a la serie chorlo - dravita con bajos contenidos en elbalta. Aunque forman un conjunto sin solución de continuidad, se puede distinguir dos grupos diferentes, parcialmente solapados, que se corresponden con los tipos anteriores cuyas composiciones medias respectivas son:
Si5,87 Al6,13 B3 (Fe1,36 Mg1,07 Mn0,01 Ti0,08 Al0.37) Na0,63 Ca0,07 K0.01
Si5,96 Al6,05 B3 (Fe1,11 Mg1,57 Mn0,02 Ti0,09 Al0.11) Na0,64 Ca0,12 K0.01
Se estudian aspectos de sus zonados cromático y composicional con disminución hacia el borde de la relación Mg/Fe; se proponen reacciones formadoras en las que interviene biotita y plagioclasa y se utiliza la relación Fe/(Fe + Mg) para discriminar su diferente origen.
This work discribes the main features of the pegmatitic tourmalines in Sierra Albarrana. Two populations are distinguished: one of these is found in the pegmatitic bodies formad from the silicated and aqueous phases and the other one is in the sourrounding rocks, and is generated by a metasomatic process. The tourmalines belong to the schorl - dravite serie with low elbaite contents, and are Li free terms. Their trend of evolution is continuous but two groups can be established with partial overlapping as mentioned above. The average compositions are: Si5,87 Al6,13 B3 (Fe1,36 Mg1,07 Mn0,01 Ti0,08 Al0.37) Na0,63 Ca0,07 K0.01 Si5,96 Al6,05 B3 (Fe1,11 Mg1,57 Mn0,02 Ti0,09 Al0.11) Na0,64 Ca0,12 K0.01 Their cromatic zoning features are studied. The Fe/Mg relation decreases from the core to the rim. Forming tourmaline reactions are proposed, and biotite, plagioclase and Fe/Fe+ Mg) ratio is used to decide the different origin.
This work discribes the main features of the pegmatitic tourmalines in Sierra Albarrana. Two populations are distinguished: one of these is found in the pegmatitic bodies formad from the silicated and aqueous phases and the other one is in the sourrounding rocks, and is generated by a metasomatic process. The tourmalines belong to the schorl - dravite serie with low elbaite contents, and are Li free terms. Their trend of evolution is continuous but two groups can be established with partial overlapping as mentioned above. The average compositions are: Si5,87 Al6,13 B3 (Fe1,36 Mg1,07 Mn0,01 Ti0,08 Al0.37) Na0,63 Ca0,07 K0.01 Si5,96 Al6,05 B3 (Fe1,11 Mg1,57 Mn0,02 Ti0,09 Al0.11) Na0,64 Ca0,12 K0.01 Their cromatic zoning features are studied. The Fe/Mg relation decreases from the core to the rim. Forming tourmaline reactions are proposed, and biotite, plagioclase and Fe/Fe+ Mg) ratio is used to decide the different origin.