Alkaline Rocks and Carbonatites of the World

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La Primavera

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Occurrence number: 
108-00-013
Country: 
Mexico
Region: 
Jalisco
Location: 
Longitude: -103.53, Latitude: 20.07

La Primavera is a large Quaternary comenditic volcano situated at the western end of the dominantly andesitic Mexican Volcanic Belt. There is no central vent or cone but a multitude of low hills of rhyolite scattered over 220 km2 stand above an ignimbrite apron. The rhyolite hills consist of lavas and pyroclastic rocks and appear to lie along inner and outer rings; within the inner ring there are sedimentary rocks which were apparently deposited in a caldera lake. A general geological account, including a detailed stratigraphical history substantiated by numerous age determinations, will be found in Mahood (1980). Clough et al. (1982) describe the morphology and dimensions of the younger lavas, while Walker et al. (1981) have investigated the pyroclastic geology and distinguished more than 30 fall deposits totalling some 90 km3. The lavas are mildly peralkaline, those of the inner ring generally being porphyritic, those of the outer aphyric. Phenocrysts are sanidine, quartz, ferrohedenbergite, fayalite, ilmenite and rare titanomagnetite, zircon, and apatite (Mahood, 1981, p. 130). Major and minor element analyses of rocks and microprobe analyses of minerals will be found in Mahood (1981). The Guadalajara ignimbrite outcrops north and northeast of La Primavera, and consists of nearly equal proportions of aphyric and sparsely porphyritic peralkaline rhyolite (Mahood et al., 1985).

Age: 
Numerous K-Ar age determinations are given by Mahood (1980, Table 1) and range from 123 300+-2400 years to 25 500+-8000 years.
References: 
CLOUGH, B.J., WRIGHT, J.V. and WALKER, G.P.L. 1982. Morphology and dimensions of the young comendite lavas of La Primavera volcano, Mexico. Geological Magazine, 119: 477-85. MAHOOD, G.A. 1980. Geological evolution of a Pleistocene rhyolitic center - Sierra La Primavera, Jalisco, Mexico. Journal of Volcanology and Geothermal Research, 8: 199-230. MAHOOD, G.A. 1981. Chemical evolution of a Pleistocene rhyolitic center: Sierra La Primavera, Jalisco, Mexico. Contributions to Mineralogy and Petrology, 77: 129-49. MAHOOD, G.A., GILBERT, C.M. and CARMICHAEL, I.S.E. 1985. Peralkaline and metaluminous mixed-liquid ignimbrites of the Guadalajara region, Mexico. Journal of Volcanology and Geothermal Research, 25: 259-71. WALKER, G.P.L., WRIGHT, J.V., CLOUGH, B.J. and BOOTH, B. 1981. Pyroclastic geology of the rhyolitic volcano of La Primavera, Mexico. Geologische Rundschau, 70: 1100-18
Fig. 117 La Primavera (after Mahood, 1981, Fig. 1).
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