Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.14/112639
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- Title
- (²¹⁰Pb/²²⁶Ra) variations during the 1994-2001 intracaldera volcanism at Rabaul Caldera
- Related
- Journal of volcanology and geothermal research, Vol. 184, No. 3-4 (2009), p.416-426
- DOI
- 10.1016/j.jvolgeores.2009.04.018
- Publisher
- Elsevier
- Date
- 2009
- FoR/RFCD Code(s)
-
040200 Geochemistry
040300 Geology
040400 Geophysics
- Author/Creator
- Cunningham, H. S
- Author/Creator
- Turner, S. P
- Author/Creator
- Patia, H
- Author/Creator
- Wysoczanski, R
- Author/Creator
- Nichols, A. R. L
- Author/Creator
- Eggins, S
- Author/Creator
- Dosseto, A
- Description
- Determining the timing and source of gas transfer during intermittent intracaldera volcanism can aid in our understanding of degassing in these large systems. Using (²¹⁰Pb/²²⁶Ra) ratios, (parentheses denote activity ratios) as a time-sensitive tracer, injections of ²²²Rn and the subsequent time scales of gas accumulation and loss can be determined. Variations in (²¹⁰Pb/²²⁶Ra) have been measured for 15 volcanic products erupted at Rabaul Caldera over the period 1994 to 2001. In addition, one basaltic enclave from the 1937 eruption was also analyzed. Water and carbon dioxide contents determined from olivine hosted melt inclusions erupted in 1997 are < 1% and suggest extensive shallow-level degassing. Both ²¹⁰Pb excesses and deficits are found in andesites and dacites, whereas the basaltic enclave displays an (²¹⁰Pb/²²⁶Ra)0 ratio of 7. Between 1994 and 1997 three samples with (²¹⁰Pb/²²⁶Ra) deficits were erupted which indicate open system gas loss since 1992 and 1994. No correlation exists between (²¹⁰Pb/²²⁶Ra) and lava chemistry, eruptive style or date. ²¹⁰Pb excesses are more common than deficits in Rabaul samples but cannot be explained by plagioclase feldspar accumulation, Pb sublimate accumulation or differentiation. Instead, a model of intra-magma ²²²Rn transfer can produce ²¹⁰Pb excesses of the appropriate magnitude if gas transfer occurs over 1–5 years from an underlying body of magma that is 2–10 times larger than the volume of erupted material and that is consistent with geophysical estimates. Although intermittent gas transfer events can be inferred by the development of ²¹⁰Pb excess, there is no evidence at Rabaul for a direct link between eruptive style, gas flux and (²¹⁰Pb/²²⁶Ra).
- Description
- 11 page(s)
- Subject Keyword
- 040200 Geochemistry
- Subject Keyword
- 040300 Geology
- Subject Keyword
- 040400 Geophysics
- Subject Keyword
- ²¹⁰Pb/²²⁶Ra
- Subject Keyword
- volatiles
- Subject Keyword
- Rabaul Caldera
- Subject Keyword
- U-series
- Subject Keyword
- gas transfer
- Subject Keyword
- timescales
- Resource Type
- journal article
- Organisation
- Macquarie University. National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC)
- Identifier
- http://hdl.handle.net/1959.14/112639
- Identifier
- ISSN:0377-0273
- Identifier
- mq-rm-2009004280
- Language
- eng
- Reviewed
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