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Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS(Papua New Guinea–Australia–Canada–Manus)hydrothermal field, Eastern Manus Basin, have 87Sr/86Sr=0.708 079–0.708 581; εNd=5.149 833–6.534 826;208Pb/204Pb=38.245–38.440; 207Pb/204Pb=15.503–15.560; 206Pb/204Pb=18.682–18.783. 87Sr/86 Sr isotope ratios are relatively homogeneous and close to the value of the surrounding seawater(0.709 16). The content of Sr in the samples contributed by seawater was estimated to be 76.7%–83.1% of total amount. The mixing temperature of hydrothermal fluids and seawater were ranging from 53.2°C to 72.2°C and the hydrothermal activities were unstable when the samples precipitated. The εNd values of all the samples are positive, which differ from the values of ferromanganese nodules(crusts) with hydrogenic origin. Nd was mainly derived from substrate rocks leached by hydrothermal circulation and preserved the hydrothermal signature. Pb isotopic compositions of most samples show minor variability except Sample #9–2 that has relatively high values of Pb isotopes. The Pb may be derived from the Eastern Manus Basin rocks leached by the hydrothermal fluid. The slightly lower 208Pb/204 Pb and207Pb/204 Pb values of the samples indicated that the hydrothermal circulation in PACMANUS was not entire and sufficient, or that hydrothermal circulation had transient changes in the past. Si-Fe-Mn-oxyhydroxides in the samples preserved the heterogeneities of local rocks.
Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS (Papua New Guinea-Australia-Canada-Manus) hydrothermal field, Eastern Manus Basin, have 87Sr / 86Sr = 0.708 079-0.708 581; εNd = 5.149 833-6.534 826; 208Pb / 204Pb = 38.245-38.440; 207Pb / 204Pb = 15.503-15.560; 206Pb / 204Pb = 18.682-18.783. 87Sr / 86 Sr isotope ratios are relatively homogeneous and close to the value of the surrounding seawater (0.709 16). The content of Sr in the samples contributed by seawater was estimated to be 76.7% -83.1% of total amount. The mixing temperature of hydrothermal fluids and seawater were ranging from 53.2 ° C to 72.2 ° C and the hydrothermal activities were unstable when the samples precipitated. The εNd values of all the samples are positive, which differ from the values of ferromanganese nodules (crusts) with hydrogenic origin. Nd was mainly derived from substrate rocks leached by hydrothermal circulation and preserved the hydrothermal signature. Pb isotopic compositions of most samples show minor variabili The except lower Sample # 9-2 that has relatively high values of Pb isotopes. The Pb may be derived from the Eastern Manus Basin rocks leached by the hydrothermal fluid. The slightly lower 208 Pb / 204 Pb and 207 Pb / 204 Pb values of the samples indicate that the hydrothermal circulation in PACMANUS was not entire and sufficient, or that hydrh circulation transient changes in the past. Si-Fe-Mn-oxyhydroxides in the samples preserved the heterogeneities of local rocks.