Lithium in spilites |
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| Authors: | Denis M Shaw Nicole Vatin-Pérignon |
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| Institution: | 2. Department of Geology, McMaster University, Hamilton, Ontario, Canada, L8S 4M1;3. Institut Dolomieu, Université de Grenoble, 38031 Grenoble, France |
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| Abstract: | During spilitisation the abundance of Li increases from about 12 ppm in normal basaltic rocks to an average of 75 ppm, with some spilites containing up to 190 ppm. This is relatively far greater than the increase of <50% in Na. Also the ratio CaO/Al2O3 decreases from about 1.0 to <0.1 and the H2O content increases markedly.Alteration of this kind requires waters rich in both Na and Li, with the material added having a ratio 105 Li/Na of about 750: the ratio for seawater is 1.8 but most subsurface waters have higher ratios and are more likely agents of spilitisation.Volcanic hydrothermal brines have suitable Li and Na abundances and are known to have reacted with fresh basalts to produce spilitic alteration: in cases of spilitisation of volcanogenic sediments, reaction with non-volcanic brines may have occurred. In both cases the waters must initially have high CO2 and low Ca activities. |
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