The Lord Howe Volcanic Complex, Australia: its geochemistry and origins

The Lord Howe Volcanic Complex (LHVC) is part of a seamount chain associated with the detached continental crust of Zealandia. We present petrographic and geochemical data for the LHVC, including the first reported data for Balls Pyramid and the first trace element data for Lord Howe Island, clarify...

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Bibliographic Details
Published in:New Zealand journal of geology and geophysics 2024-01, Vol.67 (1), p.84-104
Main Authors: Williams, Megan L., Jones, Brian G.
Format: Article
Language:English
Subjects:
Alkali basalts
Balls Pyramid
Basalt
basalts
Continental crust
Dysprosium
Earth mantle
enriched mantle
Field strength
Garnet
Geochemistry
igneous petrology
Lord Howe Island
Lord Howe Seamount Chain
mantle metasomatism
Mantle plumes
Peridotite
petrography
Phosphorus pentoxide
Plumes
Probability theory
Seamount chains
Seamounts
Slabs
Subduction (geology)
Tectonics
Titanium dioxide
Trace element geochemistry
Trace elements
Transition zone
Volcanic fields
Zealandia
Zirconium
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Summary:The Lord Howe Volcanic Complex (LHVC) is part of a seamount chain associated with the detached continental crust of Zealandia. We present petrographic and geochemical data for the LHVC, including the first reported data for Balls Pyramid and the first trace element data for Lord Howe Island, clarifying the tectonic affiliation and general mantle source characteristics. Classification and discrimination diagrams based on concentrations and ratios of immobile elements, such as rare earth and high field strength elements, Th, Ti, Y, and Mg, show the LHVC comprises transitional to alkali basalts and at least two, and probably three, shield building complexes, consistent with an intraplate tectonic setting. Primitive-mantle normalised trace element patterns, variation in Dy/Yb for a restricted range of Dy/Dy*, Zr/Yb > 90, and variations in Zr/Hf and P 2 O 5 /TiO 2 through the eruptive sequences indicate the mantle source may be a laterally heterogeneous enriched garnet peridotite that has undergone varying degrees of partial melting and carbonatitic metasomatism, both within the LHVC and along the Lord Howe Seamount Chain. The LHVC is thus an ideal natural laboratory for probing the probability of small intraplate volcanic fields originating via mantle plumes or from previously subducted slabs stagnating at the mantle transition zone.
ISSN:0028-8306
1175-8791
DOI:10.1080/00288306.2022.2108068