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Dredged igneous rocks from the northern termination of the Tofua magmatic arc, Tonga and adjacent Lau Basin

Citation

Falloon, TJ and Green, DH and Crawford, AJ, Dredged igneous rocks from the northern termination of the Tofua magmatic arc, Tonga and adjacent Lau Basin, Australian Journal of Earth Sciences, 34, (4) pp. 487-506. ISSN 0812-0099 (1987) [Refereed Article]

DOI: doi:10.1080/08120098708729428

Abstract

Fresh igneous rocks were dredged from six stations during the 1984 cruise of the Natsushima to the North Tonga Ridge and Lau Basin. Samples were recovered from inner trench wall, forearc, arc ridge and backarc basin settings in water depths >2000 m. The volcanics are unlike those of the subaerial volcanoes of the Tofua magmatic arc, and provide a glimpse of the petrological diversity present in the submarine levels of this intra‐oceanic arc‐backarc system. Amongst the dredged lavas are unusual olivine‐ and pyroxene‐bearing vitrophyres with high‐MgO (1320 wt%) and SiO2 (5256 wt%) contents. These primitive lavas are distinct petrographically and geochemically from boninites in their high CaO/Al2O3ratios (0.70.9), high‐CaO (>7 wt%) contents, and the presence of abundant olivine phenocrysts, but are similar to low‐Ti ophiolitic basalts such as those of the Upper Pillow Lavas of the Troodos ophiolite, Cyprus. The dredged Tongan high‐Mg lavas are therefore an in situ occurrence of a low‐Ti ophiolitic lava suite, and support an intra‐oceanic island arc origin for the Troodos and other ophiolites with these lavas.

Item Details

Item Type:Refereed Article
Keywords:boninite, Fiji, high -Mg lavas, Lau Basin, Lau-Colville Ridge. low-Ti lavas, ophiolites, Tofua magmatic arc, Tonga, Troodos
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Falloon, TJ (Dr Trevor Falloon)
Author:Green, DH (Professor David Green)
Author:Crawford, AJ (Professor Anthony Crawford)
ID Code:99092
Year Published:1987
Web of Science® Times Cited:29
Deposited By:Earth Sciences
Deposited On:2015-03-12
Last Modified:2015-04-21
Downloads:0

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