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| Titel |
The Morphology of the Tasmantid Seamounts: Interactions between Tectonic Inheritance and Magmatic Evolution |
| VerfasserIn |
Fred Richards, Lara Kalnins, Anthony Watts, Benjamin Cohen, Robin Beaman |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110817
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| Publikation (Nr.) |
 EGU/EGU2015-10857.pdf |
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| Zusammenfassung |
| The Tasmantid seamounts extend for over 2000 km off the east coast of Australia and
constitute one of three contemporaneous, sub-parallel Cenozoic hotspot tracks that traverse
the region (the Tasmantid, Lord Howe, and East Australian volcanic chains), locally
separated by as little as 500 km. Where dated, the three chains young from north to south,
spanning ca.Â34–6 Ma. At multiple locations, the Tasmantid chain intersects the extinct
Tasman Sea spreading centre, which was active from 84 Ma to 53 Ma. Detailed
morphological analysis reveals a strong correlation between tectonic setting, seamount
orientation, and volcanic structure. Seamounts at inside corners of the spreading
segment-transform intersections are more rugged and constructed via numerous intersecting
fissure-fed volcanic ridges, whereas off-axis seamounts tend to be conical with summit
craters and isolated dyke-fed flank cones.
In addition, the orientation of the Bouguer gravity anomaly highs, interpreted as
magmatic conduits, and the long axes of the seamounts align closely with the principal stress
directions expected for a ridge system in which strong mechanical coupling occurs across
transform faults. Such a strong connection between the long-lived mantle upwelling, ridge
structure, and subsequent dyke emplacement — despite the ≈¥ 20 Ma offset between
spreading cessation and initial seamount emplacement — suggests deep faulting of the
Tasman Sea oceanic lithosphere in order to channel melts along pre-existing structural
trends.
Despite the large size of the edifices, up to ~ 4000 m high, slope gradient and
backscatter analysis along the chain point to sluggish mass wasting rates with few
or no large sector collapse structures. In addition, most seamounts are associated
with Bouguer gravity highs. Together, these features suggest that the seamounts
have dense, coherent cores with high intrusive to extrusive volume ratios. This
indicates low rates of melt generation and intra-lithospheric transport, implying that the
thermal anomaly associated with the long-lived upwelling was relatively weak
compared to the melting anomalies invoked for Hawaii, the archetypal plume-generated
chain. |
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