Internal [sup 238]U-series systematics of pumice from the November 13, 1985, eruption of Nevado de Ruiz, Colombia

Conference · Mon Mar 01 04:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

OSTI ID:6341784

Schaefer, S J; Williams, S N ^[1]; Sturchio, N C ^[2]; Murrell, M T ^[3]

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1. Arizona State Univ., Tempe (United States)
2. Argonne National Lab., IL (United States)
3. Los Almos National Lab., NM (United States)

High-precision mass spectrometer and alpha scintillation measurements of [sup 238]U-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 de Ruiz volcano. Internal isochron diagrams for [sup 226]Ra/Ba vs. [sup 230]Th/Ba and [sup 230]Th/[sup 232]Th vs. [sup 238]U/[sup 232]Th 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 ([approx]8.6 ka) and R8 ([approx]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. 26 refs., 4 figs., 2 tabs.

• OSTI ID: 6341784
• Report Number(s): CONF-911017--; CNN: EAR-8608977; EAR-8721206
• Conference Information: Journal Name: Geochimica et Cosmochimica Acta; (United States) Journal Volume: 57:6
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
58 GEOSCIENCES
580000 -- Geosciences
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTINIDES
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
CARBON 14 DECAY RADIOISOTOPES
CHEMICAL ANALYSIS
COUNTING TECHNIQUES
ELEMENTS
ERUPTION
EVEN-EVEN NUCLEI
HEAVY ION DECAY RADIOISOTOPES
HEAVY NUCLEI
ISOTOPE RATIO
ISOTOPES
MAGMA
MASS SPECTROSCOPY
METALS
NEON 24 DECAY RADIOISOTOPES
NUCLEI
PUMICE
QUANTITATIVE CHEMICAL ANALYSIS
RADIOISOTOPES
RADIUM 226
RADIUM ISOTOPES
SCINTILLATION COUNTING
SPECTROSCOPY
SPONTANEOUS FISSION RADIOISOTOPES
THORIUM
THORIUM 230
THORIUM 232
THORIUM ISOTOPES
URANIUM
URANIUM 238
URANIUM ISOTOPES
VOLCANOES
YEARS LIVING RADIOISOTOPES