Positions are estimated from map. Analyses done on a Cameca SX-50 wavelength dispersive electron microprobe operating at 15 kV accelerating voltage, 20-mm beam diameter, 6nA beam current, and counting times of 20-55 s with Na and Al being analyzed first, as recommended by Morgan and London (1996). Standardization achieved by use of mineral and glass standards. Analyses recast to 100% on a water-free basis. All samples are rhyolites (IUGS classification, Le Bas et al., 1986).