New data on magmatic H2O contents of pantellerites,with implications for petrogenesis and eruptive dynamics at Pantelleria |
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Authors: | Jacob B Lowenstern Gail A Mahood |
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Institution: | (1) Department of Geology, Stanford University, 94305-2115 Stanford, CA, USA |
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Abstract: | Infrared spectroscopic analyses of melt inclusions in quartz phenocrysts from pantellerites erupted at Pantelleria, Italy, show that the magmas contained moderate pre-eruptive H2O contents, ranging from 1.4 to 2.1 wt.%. Melt H2O concentrations increase linearly with incompatible elements, demonstrating that H2O contents were not buffered significantly during fractionation by any crystalline or vapor phase. The relatively low H2O contents of pantellerites are consistent with an origin by partial melting of alkali gabbros rather than fractional crystallization of basalt. Preeruptive H2O concentrations do not correlate with the volume or explosivity of pantellerite eruptions; decompression history is critical in determining the style of pantellerite (and other) eruptions. |
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