Sample locations, Ar-Ar ages and major and trace element and isotope compositions for igneous rocks dredged during the VESPA scientific cruise
The SW Pacific region contains several ridges and basins that are inferred to represent pre-Quaternary volcanic arcs and back-arc basins. The geology of these features is less well characterized than that of the active Tonga-Kermadec and Vanuatu arcs. We report new major and trace element, and Pb, Hf, Sr and Nd isotope data for 27 lavas dredged from the Loyalty and Three Kings ridges during the 2015 VESPA cruise of R/V l'Atalante. Low-K basalts were dredged from the seabed deeper than 3300 m, and high-K to shoshonitic suites from shallower ridge crests at 2000–3300 m. The samples are mainly basalts, with lesser trachybasalts, basaltic andesites, trachyandesites andesites, dacites, and one granite (anhydrous SiO2 and K2O + Na2O range from ~47 to 64 and 1.5 to 11 wt% respectively). Trace element patterns allow discrimination of three geochemical signatures, identified as i) depleted, ii) transitional and iii) enriched, based on their light to heavy rare earth element (REE) ratios (with La/Sm ranging from 0.4 to 8). Depleted and transitional samples are basalts, featuring REE concentrations similar to MORB, but with high field strength element and large ion lithophile element contents, typical of back-arc basin basalts. The most enriched samples are basaltic andesites, andesites, trachyandesites and trachytes with island arc magma trace element signatures. Pb isotope ranges are limited (208Pb/204Pb ~38 to 39.8, 207Pb/204Pb ~15.51 to 15.64 and 206Pb/~17.9 to 20.1), while Hf isotopes display more diverse compositions (eHf ranging from +7.7 to +14). Both Nd (eNd = 2.8–9.3) and Sr (87Sr/86Sr = 0.7026–0.7048) isotopes are correlated with Hf data. Trace element and isotopic compositions can be explained in terms of mixing between three distinct geochemical endmembers in the mantle resembling DMM, HIMU and EM-2 sources. Our study confirms voluminous subduction-related magmatism on the Loyalty and Three Kings ridges, mostly of Late Oligocene – Early Miocene age. The issue of polarity of subduction to generate these rocks remains open, but the composition-space-time distribution of the igneous rocks can be explained in the context of SW Pacific geodynamics using a west-dipping Pacific slab model.
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Date | 2022-12-01 |
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Date type | Creation: Date identifies when the resource was brought into existence |
Date | 2023-01-10 |
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Date | 2023-04-14 |
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Unique resource identifier | a53ad03f-3930-9303-3030-000000090050 |
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Organisation name | SEA scieNtific Open data Edition |
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Delivery point | By address: IFREMER / IDM / SISMER - Scientific Information Systems for the SEA, IFREMER Centre de Bretagne, ZI Pointe du diable CS 10070 |
City | PLOUZANE |
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Organisation name | Ifremer, Scientific Information Systems for the sea |
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Delivery point | IFREMER Centre de Bretagne ZI Pointe du diable CS 10070 |
City | PLOUZANE |
Postal code | 29280 |
Country | France |
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Organisation name | Ifremer, Scientific Information Systems for the sea |
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Delivery point | IFREMER Centre de Bretagne ZI Pointe du diable CS 10070 |
City | PLOUZANE |
Postal code | 29280 |
Country | France |
Electronic mail address | sismer@ifremer.fr |
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SeaVoX salt and fresh water body gazetteer | Southwest Pacific Ocean (140W) |
SeaDataNet Agreed Parameter Groups | Rock and sediment chemistry |
SeaDataNet device categories | rock dredges |
SeaDataNet Parameter Discovery Vocabulary | Geological sample major element chemistry |
CRUISE SUMMARY REPORT INVENTORY (CSR) | 486_15001100 |
SeaVoX Platform Categories | research vessel |
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File identifier | a53ad03f-3930-9303-3030-000000090050 | ||||||||||||||
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Metadata language | English | ||||||||||||||
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Date stamp | 2024-03-26T00:00:00 | ||||||||||||||
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