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Plio-Pleistocene intra-plate magmatism from the southern Sulu Arc, Semporna peninsula, Sabah, Borneo: Implications for high-Nb basalt in subduction zones

Macpherson, C.G.; Chiang, K.K.; Hall, R.; Nowell, G.M.; Castillo, P.R.; Thirlwall, M.F.

Plio-Pleistocene intra-plate magmatism from the southern Sulu Arc, Semporna peninsula, Sabah, Borneo: Implications for high-Nb basalt in subduction zones Thumbnail


Authors

K.K. Chiang

R. Hall

P.R. Castillo

M.F. Thirlwall



Abstract

New analyses of major and trace element concentrations and Sr, Nd and Pb isotopic ratios are presented for Plio-Pleistocene basalts and basaltic andesites from the Semporna peninsula in Sabah, Borneo, at the southern end of the Sulu Arc. Depletion of high field strength elements (HFSE), which is characteristic of many subduction-related magmatic suites, is present in more evolved Semporna rocks but is associated with radiogenic Sr and Pb, and less radiogenic Nd isotopic ratios and results from contamination of mafic melt by, possibly ancient, crustal basement. The most mafic lavas from Semporna, and elsewhere in the Sulu Arc, display no HFSE depletion relative to other elements with similar compatibility. High-Nb basalt from Semporna formed when mantle resembling the source of Ocean Island Basalt (OIB) upwelled into lithospheric thin spots created during earlier subduction. This mantle did not experience enrichment by fluids or melt derived from subducted crust. The presence of similar lavas throughout the Sulu Arc and around the South China Sea suggests that the OIB-like component resides in the convecting upper mantle. Depletion of light rare earth elements, with respect to other incompatible elements, throughout the Sulu Arc could result from melt–mantle interaction during magma transport through the lithosphere. Such depletion is absent in suites from the South China Sea, where magma probably migrated along large, lithosphere-penetrating structures. Semporna high-Nb basalts are not associated with adakitic magmatism which is a frequent, but not ubiquitous, association in some active subduction zones. Both geochemical signatures are developed early in the history of a melt pulse, either in the source (high-Nb basalt) or during deep differentiation (adakite). Preservation of these distinctive geochemical signatures is favoured in settings that minimise (1) interaction with other, more copious melt types, and/or (2) subsequent differentiation in the shallow crust. Where found, the high-Nb basalt–adakite association is a result of transport through favourable lithospheric conditions and not due to any link between their mantle sources.

Journal Article Type Article
Publication Date Feb 1, 2010
Deposit Date Oct 27, 2010
Publicly Available Date Nov 15, 2010
Journal Journal of Volcanology and Geothermal Research
Print ISSN 0377-0273
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 190
Issue 1-2
Pages 25-38
DOI https://doi.org/10.1016/j.jvolgeores.2009.11.004
Keywords high-Nb basalt, Nb-enriched basalt, Sabah, Borneo, Subduction, OIB, Magmatism.
Public URL https://durham-repository.worktribe.com/output/1537948

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Copyright Statement
NOTICE: this is the author's version of a work that was accepted for publication in Journal of volcanology and geothermal research.






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