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Isotopic evidence for a link between the Lyra Basin and Ontong Java Plateau

By
Maria Luisa G. Tejada
Maria Luisa G. Tejada
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan, and National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City 1101, Philippines
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Kenji Shimizu
Kenji Shimizu
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Katsuhiko Suzuki
Katsuhiko Suzuki
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Takeshi Hanyu
Takeshi Hanyu
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Takashi Sano
Takashi Sano
Department of Geology and Paleontology, National Museum of Nature and Science, Tsukuba 305-0005, Japan
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Masao Nakanishi
Masao Nakanishi
Graduate School of Science, Chiba University, Chiba 263-8522, Japan
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Shun'ichi Nakai
Shun'ichi Nakai
Earthquake Research Institute, University of Tokyo, Tokyo 153-8902, Japan
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Akira Ishikawa
Akira Ishikawa
Department of Earth Science and Astronomy, University of Tokyo, Tokyo 153-8902, Japan
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Qing Chang
Qing Chang
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Takashi Miyazaki
Takashi Miyazaki
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Yuka Hirahara
Yuka Hirahara
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Toshiro Takahashi
Toshiro Takahashi
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Ryoko Senda
Ryoko Senda
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan
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Published:
May 01, 2015

The few geological and geophysical studies of the Lyra Basin at the western margin of the Ontong Java Plateau (OJP; Pacific Ocean) revealed that it is underlain by thicker than normal oceanic crust. The unusually thick oceanic crust is attributed to the emplacement of massive lava flows from the OJP. Dredging was conducted to sample the inferred OJP crust on the Lyra Basin but instead recovered younger extrusives that may have covered the older plateau lavas in the area. The Lyra Basin extrusives are alkalic basalts with (87Sr/86Sr)t = 0.704513–0.705105, (143Nd/144Nd)t= 0.512709–0.512749, εNd(t) = +3.0 to +3.8, (206Pb/204Pb)t = 18.488–18.722, (207Pb/204Pb)t= 15.558–15.577, and (208Pb/204Pb)t = 38.467–38.680 that are distinct from those of the OJP tholeiites. They have age-corrected (187Os/188Os)t = 0.1263–0.1838 that overlap with the range of values determined for the Kroenke-type and Kwaimbaita-type OJP basalts, but their (176Hf/177Hf)t = 0.28295–0.28299 and εHf(t) = +7.9 to +9.3 values are lower. These isotopic compositions do not match those of any Polynesian ocean island volcanics. Instead, the Lyra Basin basalts have geochemical affinity and isotopic compositions that overlap with those of some alkalic suite and alnöites in the island of Malaita, Solomon Islands. Although not directly related to the main plateau volcanism at 120 Ma, the geochemical data and modeling suggest that the origin of the Lyra Basin alkalic rocks may be genetically linked to the mantle preserved in the OJP thick lithospheric root, with magmatic contribution from the Rarotongan hotspot.

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GSA Special Papers

The Origin, Evolution, and Environmental Impact of Oceanic Large Igneous Provinces

Clive R. Neal
Clive R. Neal
Department of Civil & Environmental Engineering & Earth Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
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William W. Sager
William W. Sager
Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas 77204-5007, USA
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Takashi Sano
Takashi Sano
Department of Geology and Paleontology, National Museum of Nature and Science, Tsukuba 305-0005, Japan
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Elisabetta Erba
Elisabetta Erba
Department of Earth Sciences, Università degli Studi di Milano, 20133 Milan, Italy
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Geological Society of America
Volume
511
ISBN print:
9780813725116
Publication date:
May 01, 2015

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