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| Titel |
Tristan da Cunha: informing future eruption scenarios using high-precision Ar/Ar dating |
| VerfasserIn |
A. Hicks, D. F. Mark, J. Barclay, S. Loughlin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069080
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| Zusammenfassung |
| Fifty years ago the remote volcanic ocean island of Tristan da Cunha (South Atlantic)
erupted. Although this was the first recorded historical eruption, the volcano exhibits
a complex and dynamic eruptive history, with numerous, often compositionally
distinct, parasitic centres punctuating the large edifice. However, the precise timing of
differing styles of activity remains uncertain. Any attempt at forecasting future eruptive
scenarios is dependent upon appraisal of the past eruptive phases of Tristan, however
this is challenging due to the dispersal of young parasitic centres (< 50 ka) with a
relatively low radiogenic component. This contribution presents 15 new Ar/Ar
ages from Tristan, which when coupled with compositional information and vent
distribution, place important constraints on spatio-temporal relationships of recent
volcanism and provide information into the manner in which the volcanic edifice was
constructed.
The youngest dated lava flow was 3 ± 1 ka (1Ïă), although further stratigraphically
younger deposits exist. The oldest dated lava was 118 ± 4 ka (1Ïă) and a large-scale sector
collapse was constrained to a 13 kyr window. Data also imply that edifice construction was
rapid and piecemeal. No spatio-temporal pattern to parasitic centre activity was found and
recent volcanism from these centres varies in style, volume and composition with time,
unlike recent activity from other well-dated ocean island systems. The random
distribution and compositions of eruptive material suggests that the plumbing system
beneath Tristan resembles small pockets of magma that source rapidly from depth.
Of particular significance to hazard assessment is the discovery that the summit
was contemporaneously active with recent parasitic centre activity on the flanks
and coastal strips. A summit eruption has very different hazard implications to
localized coastal lava flows, due partly to the steep slopes (20-30Ë ) and deeply incised
gulches capable of rapidly channelling eruptive products towards inhabited coastal
areas.
These data show with continued developments in Ar isotope extraction tools and noble
gas mass spectrometer technology .....................(e.g., Mark et al., 2009; Mark et al., 2011),
the Holocene will become increasingly accessible to the Ar/Ar geochronologist and precision
and accuracy will continue to improve. |
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