Geochemistry of marine sediments from the Lau Basin, Havre Trough, and Tonga—Kermadec Ridge

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Abstract
A geochemical survey of sediments from Lau Basin, Havre Trough, and Tonga–Kermadec Ridge has been undertaken in order to study the general pattern of sedimentation and to locate areas of possible metalliferous sediment occurrence. The study was based on the analysis of 206 surface sediment samples for 19 elements. The data were subject to detailed statistical (factor and cluster) analysis. Selected sediment samples from each cluster were also subjected to partition (differential leaching) studies. The bulk sediment composition appears to be dependent on the distribution of four components: 1. Biogenic carbonate occurs mainly in the west of the region. Ca and Sr are dominantly associated with this phase. 2. Volcaniclastic sediments are found on the western flanks of the Tonga–Kermadec Ridge and adjacent to White Island, New Zealand. Al, Mg, Ti, V, Fe, and Co are strongly associated in the Tonga–Kermadec Ridge sediments. The sediments around White Island are much higher in Cr and Ni but lower in Al, Mg, Ti, and Co and much lower in Fe and V than the Tonga-Kermadec Ridge sediments. This reflects the more andesitic volcanism around White Island. 3. Terrigenous sediment is found immediately north of New Zealand and is enriched in Li, Be, and La. 4. Semiopaque Fe-Mn oxides are found only in central Lau Basin sediments where they occur in concentrations of up to 15%. These sediments are enriched in Mn, Cu, Zn, Pb, and P, and, to a lesser extent, Fe, Co, and V. The data indicate the possible importance of the central Lau Basin as a zone of metalliferous sediments of exhalative origin but do not support a similar origin for Havre Trough sediments.