期刊
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
卷 147, 期 3, 页码 319-329出版社
SPRINGER-VERLAG
DOI: 10.1007/s00410-004-0559-1
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Recent experimental evidence is used to assess the conditions under which fluorite forms an early crystallising phase in silicic magmas. Fluorite solubility primarily depends on the (Na + K)/Al balance in the coexisting silicic melt, reaching a minimum in metaluminous melts. It can display reaction relationships with topaz and titanite, depending on changes in melt composition during crystallisation. An empirical model of fluorite stability in Ca-poor peralkaline rhyolite melts is derived and applied to selected rocks: F-melt(wt%) = [(Na + K/Al) {2.1110(-3)T(degreesC) + 1.5778}] -2.789 At the F contents preserved in most silicic rocks, fluorite should normally appear late in the crystallisation sequence, in agreement with petrographic observations. During fluid-absent crustal anatexis, fluorite should melt at a relatively early stage and restitic fluorite is unlikely to persist during prolonged melting. Fluorite may, however, exert a decisive control on the alkali/alumina balance of sub-aluminous anatectic melts and it can affect the liquid line of descent of silicic magmas once extracted from source.
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