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Siegburg, Melanie; Klügel, Andreas; Rocholl, Alexander; Bach, Wolfgang (2018): Analytical data from North Su volcano (eastern Manus basin). PANGAEA, https://doi.org/10.1594/PANGAEA.895987, Supplement to: Siegburg, M et al. (2018): Magma plumbing and hybrid magma formation at an active back-arc basin volcano: North Su, eastern Manus basin. Journal of Volcanology and Geothermal Research, 362, 1-16, https://doi.org/10.1016/j.jvolgeores.2018.07.001

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Abstract:
North Su is the central volcanic edifice of the SuSu Knolls hydrothermal district, located in an extensional transform zone of the eastern Manus back-arc basin. The submarine volcano hosts a vigorous hydrothermal system with black and white smokers, diffuse fluid discharge, and accumulation of native sulfur. Among its dacitic to andesitic lavas are remarkable hybrid rocks, containing highly magnesian olivine (Fo81–94) phenocrysts with thin orthopyroxene reaction rims in a dacitic matrix. We investigated these rocks in order to understand their formation, to constrain temperature and depth of magma storage, and to identify links between magmatic processes and hydrothermal activity. The compositions, zonations and reaction rims of phenocrysts suggest that the hybrid lavas formed by mixing when dacitic to rhyodacitic magma was invaded by Mg-rich andesite to basaltic andesite with boninite affinities. The resulting melts show strong enrichment of large ion lithophile elements, moderate enrichment of light rare earth elements and depletion of Nb, Ta and Ti relative to N-MORB, characterizing them as back-arc basin magmas. Compositional zonations at the outermost rims of olivine phenocrysts suggest a period of no more than a few days between the inferred mixing event and eruption. Mineral-melt thermometers indicate a temperature of ∼1010 °C for the hybrid magma. Mineral-melt barometers give a wide range of pressures with a mean of 19 ± 217 MPa, reflecting equilibration at shallow depths as well as limited barometer performance at low pressures. In addition, many clinopyroxene phenocrysts lack equilibrium between their strongly zoned rims and the host melt. The H2O (0.9–5.3 wt%) and CO2 (70–4730 ppm) contents of melt inclusions in clinopyroxene and plagioclase phenocrysts provide better constraints on the pressure range for pre-eruptive magma storage. The data suggest that dacite phenocryst crystallization and magma mixing occurred at 40–140 MPa pressure, about 1–5 km beneath the summit of North Su. The sulfur–H2O relationship in melt inclusions reflect a degassing trend that is consistent with formation of an aqueous-sulfurous magmatic fluid, inferred to produce highly acidic vent fluids at North Su (Seewald et al., 2015). The melt inclusion data also indicate significant fractionation between F, Cl and H2O after magma degassing, possibly reflecting formation of a high-salinity brine at depth and fluorine fixation in minerals formed in the subsurface. Our results suggest that the dynamic magmatic system, with magma mixing occurring shortly before ascent and eruption, causes rapid changes in composition and quantity of exsolved fluids. Due to the short distance to the seafloor, such fluid fluctuations are rapidly transferred to the hydrothermal systems. This may be the main cause for the observed temporal, spatial and compositional variations in hydrothermal activity at North Su, and possibly at other vent fields of the Manus basin.
Coverage:
Median Latitude: -3.800503 * Median Longitude: 152.100664 * South-bound Latitude: -3.801200 * West-bound Longitude: 152.100417 * North-bound Latitude: -3.799300 * East-bound Longitude: 152.100983
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21 datasets

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Datasets listed in this publication series

  1. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5a) Clinopyroxene-hosted melt inclusions, host clinopyroxene composition adjacent to inclusion, and thermobarometry of melt inclusion - host mineral pairs. https://doi.org/10.1594/PANGAEA.895966
  2. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5b) Plagioclase-hosted melt inclusions, host plagioclase composition adjacent to inclusion, and thermobarometry of melt inclusion - host mineral pairs. https://doi.org/10.1594/PANGAEA.895967
  3. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5c) Clinopyroxene-hosted melt inclusions analyzed for their volatile contents by SIMS, host clinopyroxene composition adjacent to inclusion, and results of SIMS analyses (volume-corrected for daughter crystals). https://doi.org/10.1594/PANGAEA.895985
  4. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5d) Plagioclase-hosted melt inclusions analyzed for their volatile contents by SIMS, host plagioclase composition adjacent to inclusion, and results of SIMS analyses (volume-corrected for daughter crystals). https://doi.org/10.1594/PANGAEA.895986
  5. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5e) Olivine-hosted melt inclusions (corrected for post-entrapment crystallization), host olivine composition adjacent to inclusion, and thermometry of melt inclusion - host mineral pairs. https://doi.org/10.1594/PANGAEA.895983
  6. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S5f) Olivine-hosted melt inclusions (uncorrected composition). https://doi.org/10.1594/PANGAEA.895968
  7. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Tabel S8) Details of SIMS analyses of volatiles. https://doi.org/10.1594/PANGAEA.895964
  8. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table 1) Major element composition of groundmass and compositional range of equilibrium clinopyroxene, orthopyroxene and plagioclase. https://doi.org/10.1594/PANGAEA.895775
  9. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table 2) Volatile concentrations of clinopyroxene- and plagioclase-hosted melt inclusions. https://doi.org/10.1594/PANGAEA.895776
  10. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1a) Clinopyroxene phenocryst rims, group 1 composition (average of up to 6 single analyses) and thermobarometers applied to rim and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895936
  11. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1b) Clinopyroxene phenocryst cores, group 1 composition (average of up to 37 single analyses) and thermobarometers applied to core and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895937
  12. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1c) Clinopyroxene phenocryst cores, group 2 or transitional composition (average of up to 28 single analyses) and thermobarometers applied to core compositions and average corrected olivine-hosted melt inclusions. https://doi.org/10.1594/PANGAEA.895938
  13. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1d) Clinopyroxene cumulus crystal rims, group 1 composition (average of up to 3 single analyses) and thermobarometers applied to rim and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895939
  14. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1e) Clinopyroxene cumulus crystal cores, group 1 composition (average of up to 36 single analyses) and thermobarometers applied to core and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895940
  15. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1f) Orthopyroxene phenocryst rims (average of up to 8 single analyses) and thermobarometers applied to rim and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895941
  16. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1g) Plagioclase phenocryst and cumulus crystal rims (single analyses or average of 2 analyses) and thermobarometers applied to rim and host groundmass compositions. https://doi.org/10.1594/PANGAEA.895943
  17. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1h) Olivine phenocrysts (average of between 3 and 34 single analyses). https://doi.org/10.1594/PANGAEA.895945
  18. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S1i) Spinel inclusions in olivine phenocrysts (average of up to 14 analyses), and Fo% of host olivine. https://doi.org/10.1594/PANGAEA.895946
  19. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S2) Data for compositional traverses perpendicular to olivine rims, and results of diffusion modelling. https://doi.org/10.1594/PANGAEA.895810
  20. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S3) Major element composition of groundmass (LA-ICPMS analyses) and of matrix glasses (EMP analyses). https://doi.org/10.1594/PANGAEA.895778
  21. Siegburg, M; Klügel, A; Rocholl, A et al. (2018): (Table S4) Trace element composition of matrix glasses and one melt inclusion as determined by LA-ICPMS. https://doi.org/10.1594/PANGAEA.895816