University of Tasmania
Browse

File(s) under permanent embargo

Petrology and geochemistry of back-arc basin basalts from Lau Basin spreading ridges at 15°, 17° and 19°S

journal contribution
posted on 2023-05-18, 05:16 authored by Trevor FalloonTrevor Falloon, Malahoff, A, Zonenshain, LP, Bogdanov, Y

Fresh back-arc basin lavas were recovered during five dives of the submersible ‘Mir’ during the 1990 cruise of the research vessel ‘Akademik Mstislav Keldysh’ to the Lau Basin. Three dives were conducted on the central spreading center of the ‘King's Triple Junction’ (KTJ) in the northeastern part of the Lau Basin east of Niuafo'ou Island at approximately 15°S. The lavas from the KTJ can be divided into types I and II based on their similarities to N-MORB and the BABB magma type of Sinton and Fryer (1987) respectively. One dive each was made on the Central Lau Spreading Center (CLSC) at 18°S and the Eastern Lau Spreading Center (ELSC) at 19°S. Lavas sampled on the CLSC were associated with active hydrothermal sulphide chimneys occurring at the base of a collapsed caldera structure on the central volcanic axial high. Sampled lavas from both the CLSC and ELSC are all of type I geochemistry.

The results of the ‘Keldysh’ 90 cruise are integrated with previous work to evaluate the geochemical characteristics of the Lau Basin crust as a whole and geochemical zonation models for back-arc basin development. An important part of this review of Lau Basin basalt geochemistry is the recognition of boninites and rocks of boninitic affinity which occur at off-ridge locations throughout the Lau Basin. These are suggested to erupt during the initial stages of development of new spreading ridges associated with episodes of ridge jump or the propagation of back-arc spreading ridges into arc crust.

Hf-Th-Ta systematics of the Lau Basin lavas are used to identify unmodified mantle source compositions and possible subduction-related enriched components. Unmodified mantle source compositions range from D-, N-, and E-MORB to OIB. All Lau Basin lavas show some evidence of enrichment by a H2O ± LILE ± LREE-enriched component, a slab derived hydrous fluid. The slab-derived fluid is not homogeneous in composition perhaps reflecting the presence or absence of a subducted sediment component.

The sampled lavas from the KTJ confirm the uniqueness of the BABB magma type of Sinton and Fryer (1987).

History

Publication title

Mineralogy and Petrology

Volume

47

Pagination

1-35

ISSN

0930-0708

Department/School

School of Natural Sciences

Publisher

Springer-Verlag Wien

Place of publication

Sachsenplatz 4-6, Po Box 89, Vienna, Austria, A-1201

Rights statement

Copyright 1992 Springer

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC