Alkali feldspars as a main phosphorus reservoirs in rare-metal granites: three examples from the Bohemian Massif (Czech Republic) |
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| Authors: | J Frýda K Breiter |
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| Institution: | Czech Geological Survey, Klárov 3, 118 21 Praha 1, Czech Republic |
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| Abstract: | Phosphorus-rich alkali feldspars were found in three peraluminous highly differentiated albite-topaz-Li-mica granites in the W and S parts of the Bohemian Massif. The average contents of P2O5 in K-feldspars (K?í?ovy kámen 0.57 wt%, Homolka 0.77 wt%, and Podlesí 0.83 wt%) are higher than the average contents of P2O5 in albites (K?í?ovy kámen 0.23 wt%, Homolka 0.23 wt%, and Podlesí 0.39 wt%). The analyses of feldspars indicate that partition coefficient of phosphorus between K-feldspar and albite range from 1.5 to 2.5. Measured data in K-feldspars suggest a statistically significant difference from the Al3++P5+=2 Si4+ substitution mechanism for higher phosphorus concentration. The P-content in K-feldspars from the Podlesí-granite represent the highest P-content in natural feldspar known to date (up to 2.5 wt% of P2O5)- It is suggested that all studied granites retained nearly all phosphorus of granitic melts and that their alkali feldspars represent major reservoirs of phosphorus. |
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