Journal of Petrology Advance Access originally published online on July 13, 2005
Journal of Petrology 2005 46(11):2337-2366; doi:10.1093/petrology/egi058
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Volcán Popocatépetl, Mexico. Petrology, Magma Mixing, and Immediate Sources of Volatiles for the 1994Present Eruption
1 DEPARTMENT OF EARTH AND SPACE SCIENCES, UNIVERSITY OF WASHINGTON, SEATTLE, WA 98195, USA
2 USGS-DEPARTMENT OF EARTH AND SPACE SCIENCES, UNIVERSITY OF WASHINGTON, SEATTLE, WA 98195, USA
RECEIVED APRIL 17, 2005; ACCEPTED MAY 23, 2005
Volcán Popocatépetl has been the site of voluminous degassing accompanied by minor eruptive activity from late 1994 until the time of writing (August 2002). This contribution presents petrological investigations of magma erupted in 1997 and 1998, including major-element and volatile (S, Cl, F, and H2O) data from glass inclusions and matrix glasses. Magma erupted from Popocatépetl is a mixture of dacite (65 wt % SiO2, two-pyroxenes + plagioclase + FeTi oxides + apatite,
3 wt % H2O, P = 1·5 kbar, fO2 =
NNO + 0·5 log units) and basaltic andesite (53 wt % SiO2, olivine + two-pyroxenes,
3 wt % H2O, P = 14 kbar). Magma mixed at 46 km depth in proportions between 45:55 and 85:15 wt % silicic:mafic magma. The pre-eruptive volatile content of the basaltic andesite is 1980 ppm S, 1060 ppm Cl, 950 ppm F, and 3·3 wt % H2O. The pre-eruptive volatile content of the dacite is 130 ± 50 ppm S, 880 ± 70 ppm Cl, 570 ± 100 ppm F, and 2·9 ± 0·2 wt % H2O. Degassing from 0·031 km3 of erupted magma accounts for only 0·7 wt % of the observed SO2 emission. Circulation of magma in the volcanic conduit in the presence of a modest bubble phase is a possible mechanism to explain the high rates of degassing and limited magma production at Popocatépetl.
KEY WORDS: glass inclusions; igneous petrology; Mexico; Popocatépetl; volatiles
* Corresponding author. E-mail: witt_98103{at}yahoo.com