Effects of the hydrous domain in the mantle wedge on magma formation and mixing at the Northeast Lau Spreading Centre, SW Pacific.

Haase, K. M., Schoenhofen, M. V., Storch, B., Beier, C., Regelous, M., Rubin, K. and Brandl, Philipp (2022) Effects of the hydrous domain in the mantle wedge on magma formation and mixing at the Northeast Lau Spreading Centre, SW Pacific. Open Access Geochemistry, Geophysics, Geosystems, 23 (3). e2021GC010066. DOI 10.1029/2021GC010066.

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Abstract

Abundant volcanic activity occurs in the back-arc region of the northern Tofua island arc where the Northeast Lau Spreading Centre (NELSC) propagates southwards into older crust causing the formation of numerous seamounts at the propagating rift tip. An off-axis volcanic diagonal ridge (DR) occurs at the eastern flank of the NELSC, linking the large rear-arc volcano Niuatahi with the NELSC. New geochemical data from the NELSC, the southern propagator seamounts, and DR reveal that the NELSC lavas are tholeiitic basalts whereas the rear-arc volcanoes typically erupt lavas with boninitic composition. The sharp geochemical boundary probably reflects the viscosity contrast between off-axis hydrous harzburgitic mantle and dry fertile mantle beneath the NELSC. The new data do not indicate an inflow of Samoa plume mantle into the NELSC, confirming previously published He isotope data. The NELSC magmas form by mixing of an enriched and a depleted Indian Ocean-type upper mantle end-member implying a highly heterogeneous upper mantle composition in this area. Most NELSC lavas are little affected by a slab component implying that melting is adiabatic beneath the spreading center. The DR lavas show the influence of a component from the subducted Louisville Seamount Chain, which was previously thought to be restricted to the nearby arc volcanoes Niuatoputapu and Tafahi. This signature is rarely detected along the NELSC implying little mixing of melts from the low-viscosity hydrous portion of the mantle wedge beneath the rear-arc volcanoes into the melting region of the dry mantle beneath the NELSC.

Document Type: Article
Funder compliance: DFG:BE4459/8-1 ; BMBF:03G0263A
Keywords: back-arc spreading, lithosphere rifting, slab component, Lau Basin, Tofua island arc
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS > Marine Mineralische Rohstoffe
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Main POF Topic: PT8: Georesources
Refereed: Yes
Open Access Journal?: Yes
Publisher: (AGU) American Geophysical Union, Wiley
Related URLs:
Expeditions/Models/Experiments:
  • SO263
Date Deposited: 28 Feb 2022 13:19
Last Modified: 07 Feb 2024 15:38
URI: https://oceanrep.geomar.de/id/eprint/55370

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