The Morphology of the Tasmantid Seamounts: Interactions Between Tectonic Inheritance and Magmatic Evolution

Basement structure is known to exert strong magmatic and morphological control on continental volcanoes, but relatively little is known about the structural control of submarine volcanoes. Here we investigate the morphology of the Tasmantid Seamounts, a >2,400 km long chain of age‐progressive int...

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Published in:Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2018-10, Vol.19 (10), p.3870-3891
Main Authors: Richards, F. D., Kalnins, L. M., Watts, A. B., Cohen, B. E., Beaman, R. J.
Format: Article
Language:English
Subjects:
Channeling
Continents
Control
Correlation
east Australian volcanism
Evolution
Fault lines
Faults
flexure and rheology of oceanic lithosphere
Fracture zones
Gravity
gravity anomalies and Earth structure
Gravity data
Interactions
intraplate volcanism
Lava
Lithosphere
Magma
Mantle
Morphology
Ocean floor
Orientation
Seafloor spreading
seamount morphology
Seamounts
Spreading centres
Submarine volcanoes
tectono‐magmatic interaction
Transform faults
Trends
Volcanoes
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Summary:Basement structure is known to exert strong magmatic and morphological control on continental volcanoes, but relatively little is known about the structural control of submarine volcanoes. Here we investigate the morphology of the Tasmantid Seamounts, a >2,400 km long chain of age‐progressive intraplate volcanoes, ranging from 56 to 7 Ma. The seamounts are emplaced over the extinct Tasman Sea spreading center, which was active between 84 and 52 Ma. While thick sediment (∼1 km) obscures much of the basement, detailed morphological and geophysical analyses of the seamounts reveal a strong correlation between tectonic setting, seamount orientation, and volcanic structure, despite the ≥20 Ma interval between spreading cessation and seamount emplacement. Seamounts emplaced on fracture zones or spreading segment‐transform fault inside corners are typically large and elongate. Where original morphology is preserved, they often appear rugged and predominantly fissure‐fed. By contrast, comparatively smooth, conical seamounts with isolated dike‐fed flank cones are often found midsegment and at outside corners. Volcanic fabrics also align closely with the expected principal stress directions for strong mechanical coupling across transform faults. This behavior suggests the lithosphere is dissected by numerous deep faults, channeling magma along preexisting structural trends. Generally, low effective elastic thicknesses (
ISSN:1525-2027
1525-2027
DOI:10.1029/2018GC007821