Internal 238U-series systematics of pumice from the November 13, 1985, eruption of Nevado del Ruiz, Colombia

Stephen J. Schaefer, Neil C. Sturchio, Michael T. Murrell, Stanley Williams

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38 Scopus citations


High-precision mass spectrometer and alpha scintillation measurements of 238U-series nuclides were obtained for whole-rock pumice and constituent mineral and glass separates to help interpret the timing and nature of magmatic processes that led up to the 1985 eruption of Nevado del Ruiz volcano. Internal isochron diagrams for (226Ra) Ba vs. (230Th) Ba and ( 230Th 232Th) vs. ( 238U 232Th) show that data define linear arrays, indicating an average crystallization age of 6.1 ± 0.5 ka (Ra-Th isochron) and 7 ± 6 ka (Th-U isochron). Stratigraphic, petrographic, geochemical, repose time, and eruption volume data for the Holocene eruptive sequence of Nevado del Ruiz indicate that significant changes occurred in the subvolcanic magma chamber between eruptions R9 (≈8.6 ka) and R8 (≈3.0 ka). This coincides with the average crystallization age derived from the U-series data and may represent the injection of a new batch (or batches) of mantle-derived magma into the subvolcanic magma chamber.

Original languageEnglish (US)
Pages (from-to)1215-1219
Number of pages5
JournalGeochimica et Cosmochimica Acta
Issue number6
StatePublished - Mar 1993

ASJC Scopus subject areas

  • Geochemistry and Petrology


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