engleski

Hydrothermal activity associated with off-axis volcanism in the Peru basin

Products of low temperature hydrothermal activity are widespread in the Peru Basin and are associated with late Tertiary oceanic island type intraplate volcanics. Hydrothermal activity is still taking place as indicated by a series of sharp, high and narrow temperature anomalies over one of the volcanic cones. Submarine hydrothermal activity associated with off-axis volcanism has been frequently observed elsewhere, but was usually found to be limited to seamounts. In the Peru Basin a hydrothermal halo was found in sediments surrounding hydrothermally active seamounts in addition to hydrothermal precipitates on the tops of the seamounts. Todorokite, birnessite, Fe-nontronite, goethite, and silica were found on top of young volcanic edifices and occur as coatings on volcanic rocks and in nuclei of manganese nodules. The hydrothermal precipitates in the sediments are Mg--Fe silicates, as is the case in the adjacent Bauer Basin. The proportion of hydrothermal precipitates in the sediments increases with depth in the cores, down to the appearance of the basalt that indicates the beginning of intraplate volcanism 5 million years ago. Sediments overlying Late Tertiary volcanic rocks are locally enriched in hydrothermal material by solutions percolating upwards directly into the sediment. In these sediments, apatite and phillipsite appear to have been precipitated directly from these ascending hydrothermal solutions.

Nazca Plate; interplate volcanism; hydrothermal processes; hydrothermal haloes in sediment

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