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

Maria Luisa G. Tejada, Kenji Shimizu, Katsuhiko Suzuki, Takeshi Hanyu, Takashi Sano, Masao Nakanishi, Shun'Ichi Nakai, Akira Ishikawa, Qing Chang, Takashi Miyazaki, Yuka Hirahara, Toshiro Takahashi, Ryoko Senda

Research output: Chapter in Book/Report/Conference proceedingChapter

8 Citations (Scopus)


The few geological and geophysical studies of the Lyra Basin at the western margin of the Ontong Java Plateau (OJP; Pacifi c 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 fl ows 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 affi nity and isotopic compositions that overlap with those of some alkalic suite and alnoïtes 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.

Original languageEnglish
Title of host publicationThe Origin, Evolution, and Environmental Impact of Oceanic Large Igneous Provinces
EditorsWilliam W. Sager, Clive R. Neal, Takashi Sano, Elisabetta Erba
PublisherGeological Society of America
Number of pages19
ISBN (Electronic)9780813725116
Publication statusPublished - 2015
Externally publishedYes

Publication series

NameSpecial Paper of the Geological Society of America
ISSN (Print)0072-1077

All Science Journal Classification (ASJC) codes

  • Geology


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