Summary
Silica-poor, iron-rich liquids like those estimated for Skaergaard by Wager and Brown are preserved in Labrador as chilled pillows. Iron-rich rocks in the Kiglapait Intrusion have likewise been produced by liquids poor in silica. There is no reason to expect such liquids in volcanoes, so their absence as lavas means nothing about their possible plutonic occurrence. Successful tests of the siliceous liquid hypothesis would include showing that the proposed rhyolitic liquids can produce the observed olivines in the range Fo 10–40. They would require showing that the observed low-f O 2 oxide mineral assemblages can occur at the high silica contents proposed, and that the silicate mineral assemblages and compositions can represent high-silica liquids. I doubt very much that these critical tests can be met.
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Morse, S.A. A discussion of Hunter and Sparks (Contrib Mineral Petrol 95:451–461). Contr. Mineral. and Petrol. 104, 240–244 (1990). https://doi.org/10.1007/BF00306447
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DOI: https://doi.org/10.1007/BF00306447