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Submarine hydrothermal activity along the mid-Kermadec arc, New Zealand: Large-scale effects on venting
A136
Goldschmidt Conference Abstracts 2006
Submarine hydrothermal activity along the mid-Kermadec arc, New Zealand: Large-scale effects on venting C.E.J. DE RONDE1, E.T. BAKER2, G.J. MASSOTH1, J.E. LUPTON3, I.C. WRIGHT4, R.J. SPARKS1, S.L. WALKER2, R.R. GREENE3, S.C. BANNISTER1, M.E. REYNERS1, J. ISHIBASHI5, K. FAURE1, J.A. RESING2, G.T. LEBON2 1
GNS Science, Lower Hutt ([email protected]) NOAA/PMEL, Seattle ([email protected]) 3 NOAA/PMEL, Newport ([email protected]) 4 NIWA, Wellington ([email protected]) 5 Kyushu University, Fukuoka ([email protected]) 2
The 2002 NZAPLUME II cruise surveyed 580 km of the mid-part of the Kermadec arc (MKA), NE of New Zealand. This included mapping of hydrothermal plumes for 12 submarine volcanic centers including: Kibblewhite, Sonne, Ngatoroirangi, Cole, Kuiwai, Hungaroa, Speight, Wright, Havre, Curtis, Macauley and Giggenbach. When combined with results from the 1999 NZAPLUME I cruise to the southern Kermadec arc (SKA), a total of 840 km of active arc front has now been investigated for hydrothermal emissions. A long-arc profile shows depth to the seafloor increases between White Island, immediately offshore of New Zealand, and the Kibblewhite volcanic center. Thereafter, the seafloor remains at a constant (3000 m) depth until the Hungaroa Volcanic Center. From here the active arc front merges with the Kermadec Ridge with the seafloor shoaling to the north, where the northern-most MKA centers such as Curtis and Macauley sit right on top of the ridge. Spacing of the volcanic centers increase, on average, from 30 km in the backarc of the SKA, to 45 km in the backarc of the MKA, to 58 km on the Kermadec Ridge. The centers are dominated by cones in the backarc and by caldera volcanoes where they merge with the ridge. Hydrothermal plume surveys show that the incidence of venting is 82% (9 of 11) for MKA volcanic centers. This compares with 67% (8 of 12, now including Kibblewhite) for centers of the SKA. However, the relative intensity of venting, as given by plume thickness, areal extent, and concentration of dissolved gases and ionic species, appears much weaker for most of the MKA centers than for the SKA centers, with more intense venting appearing again in the northern section of the MKA. Projection of the northern margin of the 17-km-thick Hikurangi Plateau towards the Kermadec arc shows that it intersects the arc near Kibblewhite. Subduction of the Hikurangi Plateau would ensure unusually large amounts of fluids are released by the down-going slab, initiating melting in the upper mantle wedge and supplying the magmas needed to sustain hydrothermal systems south of Kibblewhite. doi:10.1016/j.gca.2006.06.288
Origin of the Jan Mayen hotspot: An 187Os/188Os and PGE perspective V. DEBAILLE1, R.G. TRONNES2, A.D. BRANDON3, C.-T.A. LEE4 1
Lunar and Planetary Institute, Houston, USA (debaille@lpi. usra.edu) 2 University of Oslo, Natural History Museum, Norway ([email protected]) 3 NASA-Johnson Space Center, Houston, USA (alan.d.brandon@ nasa.gov) 4 Rice University, Houston, USA ([email protected]) Jan Mayen is a volcanic island located north of Iceland. Previous studies have shown that basalts from both Jan Mayen Island and Jan Mayen platform display an enriched isotopic signature, with a continuous gradient in Sr–Nd–Pb isotopes across the Jan Mayen Platform and further along the Mohns Ridge. It is at present unclear whether Jan Mayen Island can be explained by preferential melting of enriched continental material left over from the opening of the Atlantic Ocean and dispersed in the upper mantle, or instead is related to a mantle plume, and possibly associated with the Iceland mantle plume. In order to assess the origin of the Jan Mayen hotspot, 22 basalts from Jan Mayen and the Icelandic volcanic flank zones (VFZ) have been analyzed for Os isotope compositions and highly siderophile element concentrations (Re, Pt, Ir, Pd, and Os). The samples are primitive and olivine-phyric alkaline to transitional tholeiitic basalts with MgO ranging from 5.2 to 12.4 wt%. The Iceland VFZ samples range in 187Os/188Os from 0.12117 to 0.17581. Jan Mayen samples have a more restricted range from 0.12431 to 0.13436. The Os concentrations range from 7 to 365 ppt and correlate negatively with 187Os/188Os. All the 187 Os/188Os variation range is shown at lower concentrations (<100 ppt). The large range in 187Os/188Os is displayed by one heterogeneous sample from the Iceland Eastern VFZ, which also has the lowest concentration in Os and MgO and hence would have been likely contaminated by high 187Os/188Os material during AFC processes, and by samples from the Iceland Southern VFZ. All other samples from both Iceland and Jan Mayen, show no evidence for shallow level contamination processes from ancient subcontinental lithospheric mantle (low 187Os/188Os), nor by fragments of continental crust disseminated in the mantle (high 187Os/188Os), except in the unlikely possibility of a mixing of these two extreme components in the precisely adequate proportions to result in the medium 187Os/188Os of Jan Mayen lavas. We propose that 187Os/188Os variations are related to intrinsic Iceland plume heterogeneities and thus that Jan Mayen hotspot would not be related to subcontinental lithospheric fragments present within the upper mantle. PGE concentration ratios and Sr–Nd–Pb-isotope systematics will be used to investigate the deep mantle plume model and the precise melting conditions beneath Jan Mayen Island. doi:10.1016/j.gca.2006.06.289
Goldschmidt Conference Abstracts 2006
Submarine hydrothermal activity along the mid-Kermadec arc, New Zealand: Large-scale effects on venting C.E.J. DE RONDE1, E.T. BAKER2, G.J. MASSOTH1, J.E. LUPTON3, I.C. WRIGHT4, R.J. SPARKS1, S.L. WALKER2, R.R. GREENE3, S.C. BANNISTER1, M.E. REYNERS1, J. ISHIBASHI5, K. FAURE1, J.A. RESING2, G.T. LEBON2 1
GNS Science, Lower Hutt ([email protected]) NOAA/PMEL, Seattle ([email protected]) 3 NOAA/PMEL, Newport ([email protected]) 4 NIWA, Wellington ([email protected]) 5 Kyushu University, Fukuoka ([email protected]) 2
The 2002 NZAPLUME II cruise surveyed 580 km of the mid-part of the Kermadec arc (MKA), NE of New Zealand. This included mapping of hydrothermal plumes for 12 submarine volcanic centers including: Kibblewhite, Sonne, Ngatoroirangi, Cole, Kuiwai, Hungaroa, Speight, Wright, Havre, Curtis, Macauley and Giggenbach. When combined with results from the 1999 NZAPLUME I cruise to the southern Kermadec arc (SKA), a total of 840 km of active arc front has now been investigated for hydrothermal emissions. A long-arc profile shows depth to the seafloor increases between White Island, immediately offshore of New Zealand, and the Kibblewhite volcanic center. Thereafter, the seafloor remains at a constant (3000 m) depth until the Hungaroa Volcanic Center. From here the active arc front merges with the Kermadec Ridge with the seafloor shoaling to the north, where the northern-most MKA centers such as Curtis and Macauley sit right on top of the ridge. Spacing of the volcanic centers increase, on average, from 30 km in the backarc of the SKA, to 45 km in the backarc of the MKA, to 58 km on the Kermadec Ridge. The centers are dominated by cones in the backarc and by caldera volcanoes where they merge with the ridge. Hydrothermal plume surveys show that the incidence of venting is 82% (9 of 11) for MKA volcanic centers. This compares with 67% (8 of 12, now including Kibblewhite) for centers of the SKA. However, the relative intensity of venting, as given by plume thickness, areal extent, and concentration of dissolved gases and ionic species, appears much weaker for most of the MKA centers than for the SKA centers, with more intense venting appearing again in the northern section of the MKA. Projection of the northern margin of the 17-km-thick Hikurangi Plateau towards the Kermadec arc shows that it intersects the arc near Kibblewhite. Subduction of the Hikurangi Plateau would ensure unusually large amounts of fluids are released by the down-going slab, initiating melting in the upper mantle wedge and supplying the magmas needed to sustain hydrothermal systems south of Kibblewhite. doi:10.1016/j.gca.2006.06.288
Origin of the Jan Mayen hotspot: An 187Os/188Os and PGE perspective V. DEBAILLE1, R.G. TRONNES2, A.D. BRANDON3, C.-T.A. LEE4 1
Lunar and Planetary Institute, Houston, USA (debaille@lpi. usra.edu) 2 University of Oslo, Natural History Museum, Norway ([email protected]) 3 NASA-Johnson Space Center, Houston, USA (alan.d.brandon@ nasa.gov) 4 Rice University, Houston, USA ([email protected]) Jan Mayen is a volcanic island located north of Iceland. Previous studies have shown that basalts from both Jan Mayen Island and Jan Mayen platform display an enriched isotopic signature, with a continuous gradient in Sr–Nd–Pb isotopes across the Jan Mayen Platform and further along the Mohns Ridge. It is at present unclear whether Jan Mayen Island can be explained by preferential melting of enriched continental material left over from the opening of the Atlantic Ocean and dispersed in the upper mantle, or instead is related to a mantle plume, and possibly associated with the Iceland mantle plume. In order to assess the origin of the Jan Mayen hotspot, 22 basalts from Jan Mayen and the Icelandic volcanic flank zones (VFZ) have been analyzed for Os isotope compositions and highly siderophile element concentrations (Re, Pt, Ir, Pd, and Os). The samples are primitive and olivine-phyric alkaline to transitional tholeiitic basalts with MgO ranging from 5.2 to 12.4 wt%. The Iceland VFZ samples range in 187Os/188Os from 0.12117 to 0.17581. Jan Mayen samples have a more restricted range from 0.12431 to 0.13436. The Os concentrations range from 7 to 365 ppt and correlate negatively with 187Os/188Os. All the 187 Os/188Os variation range is shown at lower concentrations (<100 ppt). The large range in 187Os/188Os is displayed by one heterogeneous sample from the Iceland Eastern VFZ, which also has the lowest concentration in Os and MgO and hence would have been likely contaminated by high 187Os/188Os material during AFC processes, and by samples from the Iceland Southern VFZ. All other samples from both Iceland and Jan Mayen, show no evidence for shallow level contamination processes from ancient subcontinental lithospheric mantle (low 187Os/188Os), nor by fragments of continental crust disseminated in the mantle (high 187Os/188Os), except in the unlikely possibility of a mixing of these two extreme components in the precisely adequate proportions to result in the medium 187Os/188Os of Jan Mayen lavas. We propose that 187Os/188Os variations are related to intrinsic Iceland plume heterogeneities and thus that Jan Mayen hotspot would not be related to subcontinental lithospheric fragments present within the upper mantle. PGE concentration ratios and Sr–Nd–Pb-isotope systematics will be used to investigate the deep mantle plume model and the precise melting conditions beneath Jan Mayen Island. doi:10.1016/j.gca.2006.06.289