Subduction initiation terranes exposed at the front of a 2 Ma volcanically-active subduction zone

Type Article
Date 2019-02
Language English
Author(s) Patriat MartinORCID1, Falloon Trevor2, Danyushevsky Leonid2, Collot Julien3, Jean Marlon M.4, 5, Hoernle Kaj6, Hauff Folkmar6, Maas Roland7, Woodhead Jon D.7, Feig Sandrin T.8
Affiliation(s) 1 : IFREMER, Unite Geosci Marines, F-29280 Plouzane, France.
2 : Univ Tasmania, Sch Nat Sci Earth Sci, Coll Sci & Engn, Hobart, Tas 7001, Australia.
3 : DIMENC, Serv Geol Nouvelle Caledonie, 1 Ter Rue Unger,BP465, Noumea 98845, New Caledonia.
4 : Univ Rochester, Earth & Environm Sci, POB 270221, Rochester, NY 14627 USA.
5 : Leibniz Univ Hannover, Inst Mineral, Callinstr 3, D-30167 Hannover, Germany.
6 : GEOMAR Helmholtz Ctr Ocean Res Kiel, Wischhofstr 1-3, D-24148 Kiel, Germany.
7 : Univ Melbourne, Sch Earth Sci, Melbourne, Vic 3010, Australia.
8 : Univ Tasmania, Cent Sci Lab, Hobart, Tas 7001, Australia.
Source Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2019-02 , Vol. 508 , P. 30-40
DOI 10.1016/j.epsl.2018.12.011
WOS© Times Cited 12
Keyword(s) subduction zone, subduction initiation, forearc, ophiolites, boninites, adakites
Abstract

The development of ideas leading to a greater understanding of subduction initiation is limited by the scarcity of present-day examples. Furthermore, the few examples identified so far unfortunately provide few insights into the nature of magmatism at the inception of subduction. Here we report new observations from the Matthew and Hunter (M&H) subduction zone, a very young subduction zone located in the South-West Pacific. Tectonics of the area show it is younger than 2 Ma, making the M&H the youngest known volcanically-active subduction system and hence providing unique insights into the earliest stages of subduction initiation. Volcanism in this area comprises an exceptionally diverse range of contemporaneously erupting magma compositions which are spatially juxtaposed. Pb isotopic compositions and abundance of LILE and REE strongly suggest melting of upwelling asthenospheric mantle (Indian MORB) and subducted oceanic crust (Pacific MORB of the South Fiji Basin) and the mixing of these two components. Volcanism occurs much closer to the trench compared to volcanism in more mature subduction zones. We demonstrate that the M&H subduction zone is a modern example of an immature subduction system at the stage of pre-arc, near-trench magmatism. It is not yet building an arc but what we propose to call a Subduction Initiation Terrane (SITER). Today, the proto-forearc of the M&H subduction zone is a collage of these SITERs, coeval back-arc domains and remnants of pre-existing terranes including old Vitiaz Arc crust. The M&H area represents a modern analog of a Supra Subduction Zone setting where potentially a majority of ophiolites have formed their crustal and lithospheric components. Present-day magmatism in the M&H area therefore provides clues to understanding unforeseen distribution of contrasted magmatic rock types in fossil forearcs, whether they are at the front of mature subduction zones or in ophiolites.

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Patriat Martin, Falloon Trevor, Danyushevsky Leonid, Collot Julien, Jean Marlon M., Hoernle Kaj, Hauff Folkmar, Maas Roland, Woodhead Jon D., Feig Sandrin T. (2019). Subduction initiation terranes exposed at the front of a 2 Ma volcanically-active subduction zone. Earth And Planetary Science Letters, 508, 30-40. Publisher's official version : https://doi.org/10.1016/j.epsl.2018.12.011 , Open Access version : https://archimer.ifremer.fr/doc/00473/58422/