FN Archimer Export Format PT J TI Implications of high-Mg# adakitic magmatism at Hunter Ridge for arc magmatism of the Fiji - Vanuatu region BT AF McCarthy, A. Falloon, T.J. Danyushevsky, L.V. Sauermilch, I. Patriat, Martin Jean, M.M. Maas, R. Woodhead, J.D. Yogodzinski, G.M. AS 1:1,2;2:3;3:3;4:1,4;5:5;6:6,7;7:8;8:8;9:9; FF 1:;2:;3:;4:;5:PDG-REM-GEOOCEAN-ALMA;6:;7:;8:;9:; C1 Institute of Marine and Antarctic Studies, University of Tasmania, Australia Institute of Geochemistry and Petrology, ETH Zurich, Switzerland CODES and Earth Sciences, School of Natural Sciences, University of Tasmania, Australia Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands Geo-Ocean, Univ Brest, CNRS, Ifremer, UMR6538, F-29280 Plouzané, France Western Colorado University, Department of Geology, 1 Western Way, Hurst Hall 128, Gunnison, CO 81231, United States of America Ohio University, Lancaster, 1570 Granville Pike, Lancaster, OH 43130, United States of America School of Earth Sciences, University of Melbourne, Victoria 3010, Australia School of the Earth, Ocean, and Environment, University of South Carolina, United States of America C2 UNIV TASMANIA, AUSTRALIA ETH ZURICH, SWITZERLAND UNIV TASMANIA, AUSTRALIA UNIV UTRECHT, NETHERLANDS IFREMER, FRANCE UNIV WEST COLORADO, USA UNIV OHIO, USA UNIV MELBOURNE, AUSTRALIA UNIV SOUTH CAROLINA, USA SI BREST SE PDG-REM-GEOOCEAN-ALMA UM GEO-OCEAN IN WOS Ifremer UMR copubli-europe copubli-int-hors-europe IF 5.3 TC 1 UR https://archimer.ifremer.fr/doc/00772/88369/93999.pdf https://archimer.ifremer.fr/doc/00772/88369/94000.pdf LA English DT Article DE ;high-Mg# magmatism;adakitic magmatism;Vanuatu arc;Hunter Ridge;slab melting AB The mostly submarine Hunter Ridge, located in the SW Pacific records a ∼12 Myr to present history of magmatism related to the opening of the North Fiji Basin and subduction of oceanic lithosphere of the South Fiji Basin. Although the Hunter Ridge is probably composed primarily of an older Vitiaz-related basement, young volcanic features are present from Matthew Island to Kadavu Island. Some dredged volcanic rocks from these features have low-FeO and high-Mg# affinities, ranging from picrites to high-Mg# andesites and dacites. Elevated Sr (500 – 3400 ppm) and Sr/Y (50 – 240) coupled to fractionated (adakitic) rare-earth element patterns (La/Yb = 5 – 40, Gd/Yb = 1.5 – 5.7) indicate a garnet-signature derived from the melting of eclogite-facies basalt. Pacific-type MORB Nd-Hf-Pb isotopic ratios of these rocks contrast with the Indian-type MORB nature of the underlying North Fiji mantle but match closely the subducted South Fiji ocean crust. Low values of Th/La (< 0.15), Ba/La (< 22), unradiogenic 87Sr/86Sr (0.7026 – 0.7032) and Pacific-MORB Nd-Hf-Pb isotopic ratios indicate that sediment is a minor contributor to the source. The isotopic data clearly connect Hunter Ridge arc rocks of all compositions (picrites, low- to medium K2O arc lavas, basalts, high-Mg# andesites and dacites) to source components predominantly within the subducting plate. Unradiogenic 87Sr/86Sr (0.7026 – 0.7029) at high Sr abundances (700 – 1400 ppm) are common in hot-slab localities and are interpreted to reflect flux-melting of MORB under eclogite-facies conditions driven by dehydration in the underlying mantle of the subducting plate. Such an adakitic slab-melt component can be detected in more common (non-adakitic) arc rocks along the Hunter Ridge and Vanuatu arc as well. Evidence of slab melting along the western Pacific indicates that melting of subducting oceanic lithosphere is likely a common occurrence at convergent margins. PY 2022 PD JUN SO Earth And Planetary Science Letters SN 0012-821X PU Elsevier BV VL 590 UT 000808234800002 DI 10.1016/j.epsl.2022.117592 ID 88369 ER EF