Journal article
Dacite formation at Ilopango Caldera, El Salvador: U‐series disequilibrium and implications for petrogenetic processes and magma storage time
Geochemistry, Geophysics, Geosystems, Vol.13(6), pp.np-n/a
06/2012
DOI: 10.1029/2012GC004107
Abstract
Ilopango Caldera was formed ∼1810 years ago by eruption of the Tierra Blanca Joven (TBJ) dacite (70 km3) in central El Salvador. A subsequent eruption in 1880 produced a cluster of dacite domes in the center of Lago Ilopango that contain olive‐bearing enclaves of basaltic andesite. The purpose of this study is to use trace element, isotope, and U‐series data from the TBJ and 1880 eruptions to assess petrogenesis and the timescale of magma storage. We find that although the range of trace element data in the TBJ dacite can be reproduced by simple crystal fractionation of a plagioclase‐ and amphibole‐rich mineral assemblage, the87Sr/86Sr and 207Pb/204Pb data suggest that the 1880 basaltic andesite enclave has a different source than the dacites. This is consistent with U‐series data that show the TBJ dacites have lower (230Th/232Th) than the 1880 basaltic andesite enclave (1.5 versus 1.6, respectively). All Ilopango rocks have 230Th excesses, and the range in (238U/232Th) of the TBJ dacites can be modeled by crystal fractionation of a mineral assemblage including accessory zircon and allanite from a magma that is similar in composition to the enclave. Mineral isochrons yield crystallization ages of <10,000 years, and disequilibrium (226Ra/230Th) values suggest a similarly short residence time. Our data suggest that the large volumes of erupted dacite at Ilopango Caldera are generated very rapidly. Key Points U‐series data show that magma production is very rapid at Ilopango, > 10 ka U‐series disequilibrium in this system is caused by accessory phase fractionation Rhydoacites formed by ~50% fractional crystallization of a basaltic magma
Details
- Title: Subtitle
- Dacite formation at Ilopango Caldera, El Salvador: U‐series disequilibrium and implications for petrogenetic processes and magma storage time
- Creators
- Jennifer M GarrisonMark K ReaganKenneth W. W Sims
- Resource Type
- Journal article
- Publication Details
- Geochemistry, Geophysics, Geosystems, Vol.13(6), pp.np-n/a
- DOI
- 10.1029/2012GC004107
- ISSN
- 1525-2027
- eISSN
- 1525-2027
- Number of pages
- 20
- Grant note
- National Science Foundation; MARGINS (OCE 0405262)
- Language
- English
- Date published
- 06/2012
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9983983650002771
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