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New Zealand’s lithospheric mantle

The islands of New Zealand represent portions of a largely undersea continent known as Zealandia (Fig. 1). We have focused on characterising the composition and isotopic evolution of the base of this young continent though examination of ophiolitic rocks, orogenic peridotites (Czertowicz et al., 2016a, b), xenoliths in alkaline volcanic rocks (Scott et al., 2014a, 2014b, 2016a, 2016b; Dalton et al., 2016), and the alkaline basalts themselves (Scott et al., 2013; van der Meer et al., 2013, 2016, 2017).


The Zealandia mantle to be heterogeneous, with large of fertile and depleted domains (Scott et al., 2016a). Os and Hf isotopes indicate that portions of this mantle have Proterozoic to Archean depletion ages (Scott et al., 2016a; Liu et al., 2015), although these appear to be embedded within younger depleted mantle. Sr-Nd-Pb-Hf isotopes and trace element analyses of clinopyroxene reveal that domains have, for the most part, been variably enriched either by CO2-bearing fluids (Scott et al., 2014a, b, Dalton et al., 2017) (Fig. 2) or by hydrous fluids (Czertowicz et al., 2016a). The CO2-bearing fluids have imparted a HIMU-like composition on the lithospheric mantle. Whether or not these enriched domains could have melted to provide intraplate basalts remains unclear (Scott et al., 2016a; Dalton et al., 2017), although pyroxene diffusion modelling suggests that the lithospheric mantle shows little rise in temperature accompanying magmatism. Orthopyroxene trace element compositions provide a tool for interpreting depletion and enrichment in refractory samples; investigation of two highly refractory suites indicates that even the depleted rocks show some enrichment history (Scott et al., 2016b). Mg isotopes on basalts and xenoliths suggest crustal carbonate in the source (Wang et al., 2016). Together with Dr. Steven Smith, we are now investigating nature of fluid flow around fault zones that affect ultramafic rocks.

Students, listed below, have played a key role in the research.

  • Alice Hodgkinson (BSc Hons, 2013)
  • Jordan Crase (BSc Hons, 2015)
  • Haydon Dalton (BSc Hons, 2016)
  • Tom Czertowicz (PhD, 2016)
  • Tom Dwight (BSc Hons, 2016)
  • Chris Tulley (BSc Hons, 2016)
  • Matthew Tarling (PhD, 2016- )
  • Steph Junior (PhD, 2017- )

Fig. 1. The continent of Zealandia, with some of the ultramafic mantle localities indicated.
Fig. 1. The continent of Zealandia, with some of the ultramafic mantle localities indicated.

Fig. 2. Schematic section through the crust and lithosphere beneath the Dunedin Volcanic Group, illustrating the different mantle domains. Figure from Dalton et al. (2017).
Fig. 2. Schematic section through the crust and lithosphere beneath the Dunedin Volcanic Group, illustrating the different mantle domains. Figure from Dalton et al. (2017).

Tom Dwight surveys the Broughton Arm Peridotite in central Fiordland.
Tom Dwight surveys the Broughton Arm Peridotite in central Fiordland.

The boundary between ultramafic rocks and schist at Mt Richards (background) and Mt Raddle (foreground).
The boundary between ultramafic rocks and schist at Mt Richards (background) and Mt Raddle (foreground).

View of the ultramafic portion of the Dun Mountain Ophiolite Belt at Red Mountain in the Southern Alps.
View of the ultramafic portion of the Dun Mountain Ophiolite Belt at Red Mountain in the Southern Alps.

Publications

  1. van der Meer, Q.H.A., Waight T.E., Scott, J.M., Munker, C. (2017). Variable sources for Cretaceous to recent HIMU and HIMU-like intraplate magmatism in New Zealand. Earth and Planetary Science Letters 469, 27-41. http://dx.doi.org/10.1016/j.epsl.2017.03.037
  2. Dalton, H.B., Scott, J.M., Liu, J., Waight, T.E., Pearson, D.G., Le Roux, P., Palin, J.M. (2017). Diffusion-zoned pyroxenes in a heterogeneous mantle lithosphere under the Dunedin Volcanic Group and their implications for intraplate alkaline magmatic sources. Lithosphere,  in press. http://dx.doi.org/10.1130/L631.1
  3. Scott, J.M., Brenna M., Crase J.A., Waight, T.E., van der Meer, Q.H.A., Cooper A.F., Palin J.M., Le Roux, P., Münker, C. (2016a). Peridotitic lithosphere metasomatised by volatile-bearing melts, and its association with intraplate alkaline HIMU-like magmatism. Journal of Petrology, 57, 2053-2078. https://doi.org/10.1093/petrology/egw069
  4. Scott, J.M., Liu, J., Pearson, D.G., Waight, T.E. (2016b). Mantle depletion and metasomatism recorded in orthopyroxene in highly depleted peridotites. Chemical Geology, 441, 280-291. http://dx.doi.org/10.1016/j.chemgeo.2016.08.024
  5. van der Meer, Q.H.A., Storey, M., Scott, J.M., Waight, T.E. (2016). Abrupt spatial and geochemical changes in lamprophyre magmatism related to Gondwana fragmentation prior, during and after opening of the Tasman Sea. Gondwana Research, 36:129-143.  http://dx.doi.org/10.1016/j.gr.2016.04.004
  6. Czertowicz, T.A., Scott, J.M., Waight T.E., Palin J.M., Van der Meer, Q.H.A., Le Roux, P., Münker, C., Piazolo, S. (2016a). The Anita Peridotite, New Zealand: Ultra-depletion and subtle enrichment in the sub-arc mantle. Journal of Petrology, 57 (4): 717-750. http://dx.doi.org/10.1093/petrology/egw001
  7. Czertowicz, T.A., Toy, V.G., Scott, J.M. (2016b). Recrystallization, phase mixing and strain localization in peridotite during rapid extrusion of sub-arc mantle. Journal of Structural Geology, 88:1-19. http://dx.doi.org/10.1016/j.jsg.2016.04.011
  8. Wang, S.-J., Teng, F.-Z., Scott, J.M. (2016). Tracing the origin of continental HIMU-like intraplate volcanism using magnesium isotope systematics. Geochemica et Cosmochimica Acta, 185:78-87. http://dx.doi.org/10.1016/j.gca.2016.01.007
  9. Liu, J., Scott, J.M., Martin, C.E., Pearson, D.G. (2015). The longevity of Archean mantle residues in the convecting upper mantle and their role in young continent formation. Earth & Planetary Science Letters, 424, 109-118. http://dx.doi.org/10.1016/j.epsl.2015.05.027
  10. Scott, J.M., Waight, T.E., Van der Meer, Q.H.A., Palin, J.M., Cooper, A.F., Münker, C. (2014). Metasomatized ancient lithospheric mantle beneath the young Zealandia microcontinent and its role in HIMU-like intraplate magmatism. Geochemistry, Geophysics, Geosystems, 15(9), 3477-3501. http://dx.doi.org/10.1002/2014GC005300
  11. Scott, J.M., Hodgkinson, A., Palin, J.M., Waight, T.E., Van der Meer, Q.H.A., Cooper, A.F. (2014). Ancient melt depletion overprinted by young carbonatitic metasomatism in the New Zealand lithospheric mantle. Contributions to Mineralogy & Petrology, 167, 963. http://dx.doi.org/10.1007/s00410-014-0963-0 
  12. Scott, J.M., Turnbull, I.M., Auer, A., Palin, J.M. (2013). The Sub-Antarctic Antipodes Volcano: A < 0.5 Ma HIMU-like Surtseyan volcanic outpost on the edge of the Campbell Plateau, New Zealand. New Zealand Journal of Geology & Geophysics, 56(3), 134-153. http://dx.doi.org/10.1080/00288306.2015.1023810
  13. van der Meer, Q.H.A., Scott, J.M., Waight, T.E., Sudo, M., Scherstén, A., Cooper, A.F., Spell, T.L. (2013). Magmatism during Gondwana break-up: New geochronological data from Westland, New Zealand. New Zealand Journal of Geology & Geophysics, 56(4), 229-242. http://dx.doi.org/10.1080/00288306.2013.826699