The dataset consists of the bulk chemical and mineral compositions of hydrothermal ferromanganese oxides obtained from a petit-spot volcano in the western North Pacific Ocean and Pb isotopic compositions of the hydrothermal ferromanganese oxides, present hydrogenetic ferromanganese crusts and lavas of petit-spot volcanoes in the western North Pacific Ocean. The bulk chemical analysis was performed using X-ray fluorescence spectrometry (Primus II, Rigaku, Tokyo, Japan) and inductively coupled plasma mass spectrometry (ICP–MS; iCAP-Q, Thermo Fisher Scientific, Bremen, Germany) at The University of Tokyo. Pb isotopic analysis was performed using a multicollector ICP–MS (Neptune Plus, Thermo Fisher Scientific, Bremen, Germany) at Chiba Institute of Technology. The details of the samples and the analytical methods are shown in the reference article.

The dataset consists of elemental mapping data of hydrothermal ferromanganese oxides (D05-20 and D05-21) obtained from a petit-spot volcano in the western North Pacific Ocean. The elemental mapping of Al, Ca, Cu, Fe, K, Mg, Mn, Ni, Rb, S, Si, and Zn was performed on polished cross sections of the samples using micro-XRF (XGT7000V, Horiba, Kyoto, Japan) with energy-dispersive X-ray spectroscopy at Kyoto University. The analysis was repeated 15 times at a tube voltage of 50 kV, a tube current of 0.9 A, and an X-ray beam diameter of 100 µm. Scanning was performed in ~75 µm intervals (pixel size) at a rate of 9 ms/pixel. The intensity was determined as the cumulative intensity of the 15 analyses (total analysis time = 135 ms/pixel).

The dataset consists of IC (independent component) sores and IC loadings as the results of ICA (independent component analysis) on elemental mapping data of hydrothermal ferromanganese oxides obtained from a petit-spot volcano in the western North Pacific Ocean (https://doi.org/10.6084/m9.figshare.22559677). ICA was implemented using the “fastICA” function in the “fastICA” package developed for R software. The number of extracted ICs is 6.

The dataset consists of the bulk chemical and mineral compositions of hydrothermal ferromanganese oxides obtained from a petit-spot volcano in the western North Pacific Ocean and Pb isotopic compositions of the hydrothermal ferromanganese oxides, present hydrogenetic ferromanganese crusts and lavas of petit-spot volcanoes in the western North Pacific Ocean. The bulk chemical analysis was performed using X-ray fluorescence spectrometry (Primus II, Rigaku, Tokyo, Japan) and inductively coupled plasma mass spectrometry (ICP–MS; iCAP-Q, Thermo Fisher Scientific, Bremen, Germany) at The University of Tokyo. Pb isotopic analysis was performed using a multicollector ICP–MS (Neptune Plus, Thermo Fisher Scientific, Bremen, Germany) at Chiba Institute of Technology. The details of the samples and the analytical methods are shown in the reference article.

The dataset is the results of powder X-ray diffraction analysis (consisting of columns of degree of 2θ and X-ray diffraction intensity of each sample) for hydrothermal ferromanganese oxides obtained from a petit-spot volcano in western North Pacific Ocean. The analysis was performed using an Ultima IV instrument (Rigaku, Tokyo, Japan) at the University of Tokyo with CuKα radiation (40 kV and 30 mA) at the University of Tokyo. The scan range was 3°–75°(2θ) at a scan rate of 1°per minute. The mineral compositions of the samples are shown in the reference dataset (https://doi.org/10.6084/m9.figshare.22559803).

The dataset is the results of powder X-ray diffraction analysis (consisting of columns of degree of 2θ and X-ray diffraction intensity of each sample) for hydrothermal ferromanganese oxides obtained from a petit-spot volcano in western North Pacific Ocean. The analysis was performed using an Ultima IV instrument (Rigaku, Tokyo, Japan) at the University of Tokyo with CuKα radiation (40 kV and 30 mA) at the University of Tokyo. The scan range was 3°–75°(2θ) at a scan rate of 1°per minute. The mineral compositions of the samples are shown in the reference dataset (https://doi.org/10.6084/m9.figshare.22559803).

The dataset consists of IC (independent component) sores and IC loadings as the results of ICA (independent component analysis) on elemental mapping data of hydrothermal ferromanganese oxides obtained from a petit-spot volcano in the western North Pacific Ocean (https://doi.org/10.6084/m9.figshare.22559677). ICA was implemented using the “fastICA” function in the “fastICA” package developed for R software. The number of extracted ICs is 6.

The dataset consists of elemental mapping data of hydrothermal ferromanganese oxides (D05-20 and D05-21) obtained from a petit-spot volcano in the western North Pacific Ocean. The elemental mapping of Al, Ca, Cu, Fe, K, Mg, Mn, Ni, Rb, S, Si, and Zn was performed on polished cross sections of the samples using micro-XRF (XGT7000V, Horiba, Kyoto, Japan) with energy-dispersive X-ray spectroscopy at Kyoto University. The analysis was repeated 15 times at a tube voltage of 50 kV, a tube current of 0.9 A, and an X-ray beam diameter of 100 µm. Scanning was performed in ~75 µm intervals (pixel size) at a rate of 9 ms/pixel. The intensity was determined as the cumulative intensity of the 15 analyses (total analysis time = 135 ms/pixel).

Numerous large igneous provinces formed in the Pacific Ocean during Early Cretaceous time, but their origins and relations are poorly understood. We present new geochronological and geochemical data on rocks from the Manihiki Plateau and compare these results to those for other Cretaceous Pacific plateaus. A dredged Manihiki basalt gives an 40Ar-39Ar age of 117.9+/-3.5 Ma (2 sigma), essentially contemporaneous with the Ontong Java Plateau ~2500 km to the west, and the possibly related Hikurangi Plateau ~3000 km to the south. Drilled Manihiki lavas are tholeiitic with incompatible trace element abundances similar to those of Ontong Java basalts. These lavas may result from high degrees of partial melting during the main eruptive phase of plateau formation. There are two categories of dredged lavas from the Danger Islands Troughs, which bisect the plateau. The first is alkalic lavas having strong enrichments in light rare earth and large-ion lithophile elements; these lavas may represent late-stage activity, as one sample yields an 40Ar-39Ar age of 99.5+/-0.7 Ma. The second category consists of tholeiitic basalts with U-shaped incompatible element patterns and unusually low abundances of several elements; these basalts record a mantle component not previously observed in Manihiki, Ontong Java, or Hikurangi lavas. Their trace element characteristics may result from extensive melting of depleted mantle wedge material mixed with small amounts of volcaniclastic sediment. We are unaware of comparable basalts elsewhere.