Neotectonics and Geochemistry of Alkalic Volcanic Centers in the Tabar-Lihir-Tanga-Feni Island Chain: Participation in Project EDISON


P.I. Michael R. Perfit


NSF collaborative research project with K. Farley and B.I.A. McInnes at Caltech


Rock and sediment samples from the New Ireland fore-arc basin were recovered during a very successful geological/geophysical cruise aboard the RV SONNE in March 1994. The purpose of the cruise was to locate submarine hydrothermal activity along the flanks of the Tabar, Lihir, Tanga and Feni volcanoes and to sample the forearc for mineral deposits and recent volcanic activity (Herzig et al., 1994).
Over 85 fresh volcanic rocks and mantle/crustal xenolith samples have been petrographically examined (McInnes et al., 1994a). A suite (50 samples) of fresh rocks from both the forearc and subaerial arc have been analyzed for major, trace and rare earth elements, and an initial group of 10 samples have been analyzed for and He, Sr, Nd and Pb isotopic compositions. Water and CO2 contents of glass-bearing samples are being determined by FTIR in collaboration with Dr. S. Newman (Caltech). Oxygen isotope compositions of phenocrysts are being determined by laser fluorination in collaboration with Dr. John Eiler (Caltech).
The zero-age xenolith assemblage is distinctly similar to samples reported from ophiolite suites, with lithologies that include spinel lherzolite, harzburgite, dunite, orthopyroxenite, wehrlite, serpentinite, gabbro, hornblende gabbro, anorthosite, plagiogranite, diabase, basalt, and deep water sediments (volcaniclastic and pelagic). The xenoliths appear to represent a 100 km thick cross-section of oceanic lithosphere sampled by the basalt during its ascent from the mantle to the ocean floor. Petrographic and geochemical examination indicates that rocks comprising the New Ireland fore-arc lithosphere were formed at a mid-ocean ridge, underwent an off-axis stage of low-T hydrous metamorphism that was subsequently followed by a period of sustained high-T thermal reactivation accompanied by oxidation in an arc environment.
Results of the chemical and isotopic analyses indicate that most of the volcanic rocks recovered from submarine volcanic edifices are similar to samples from the island chain. As on the islands, most of the rocks are extremely alkalic but retain arc-like geochemical signatures.

Publications related to the above award:

Farley, K., Patterson, D. and McInnes, B.I.A. 1995. He-isotopic investigation of geothermal gases from the Tabar-Lihir-Tanga-Feni arc and Rabaul, Papua New Guinea, in Farley, K.A. (ed.), Deep Earth and Planetary Volatiles , American Inst. Physics, NY (in press).

Ducea, M.N., McInnes, B.I.A., and Wyllie, P.J. 1995. Sulfur variations in glasses from volcanic rocks: Effect of melt composition on sulfur solubility. International Geology Review (in press, will appear in August, 1995 issue).

Herzig, P., Hannington, M, McInnes, B., Stoffers, P., Villinger, H., Seifert, R, Binns, R., and Liebe, T. 1994. Submarine volcanism and hydrothermal venting studied in Papua New Guinea, EOS, American Geophysical Union, V. 75 (44), 513-516.

McInnes, B.I.A., Binns, R.A., Browne, P. and Jonasson, I. 1994a. Petrology and volcanology of samples collected during SO-94 in the New Ireland fore-arc, pages 117-150, in Herzig, P.M. and Shipboard Scientific Party, Tectonics, petrology and hydrothermal processes in areas of alkaline island-arc volcanoes in the southwest Pacific: The Tabar-Lihir-Tanga-Feni island chain, Papua New Guinea. Cruise report SONNE-94, BMFT, Germany, 273 p. McInnes, B., Herzig, P., Hannington, M. and Binns, R. 1994b. Modern oceanic fore-arc lithosphere resembles ophiolite sequences, Eos 75 (44), 747 (abstract).

Patterson, D.B., Farley, K.A. and McInnes, B.I.A. 1994. Helium isotopes in samples from a unique tectonic environment: the Tabar-Lihir-Tanga-Feni island arc, NE Papua New Guinea, Eos 75 (44), 740 (abstract).

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Last update: July 19, 2000