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

ABSTRACT

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 P₂O₅/TiO₂ 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.

KEYWORDS:

• Trace element geochemistry
• enriched mantle
• mantle metasomatism
• Lord Howe Island
• Balls Pyramid
• igneous petrology
• petrography
• basalts
• Lord Howe Seamount Chain
• Zealandia

Acknowledgements

We wish to thank Mr Ross Pogson from the Australian Museum for access to and assistance with the samples from that institution, and Mr Jose Abrantes at the University of Wollongong for sample and thin section preparation. The two reviewers provided valuable comments that improved the presentation and interpretations within the manuscript.

Credit author statement

Megan Williams: Conceptualisation, Methodology, Formal analysis, Investigation, Data curation, Writing – Original Draft, Writing – Review and Editing, Visualisation, Project administration. Brian Jones: Conceptualisation, Methodology, Formal analysis, Investigation, Resources, Writing – Original Draft, Writing – Review and Editing, Funding acquisition.

Data availability statement

The supplementary data that support the findings of this study are openly available in Zenodo at https://doi.org/10.5281/zenodo.6770635 in the following two files:

Supplementary file 1.xlsx – geochemical data for the samples examined in this study.

Supplementary file 2.docx – petrographic descriptions, XRD analyses, and microphotographs for the samples examined in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

Financial support was received from the GeoQuEST Research Centre, School of Earth, Atmospheric and Life Sciences, University of Wollongong.