The subcontinental mantle beneath southern New Zealand, characterised by helium isotopes in intraplate basalts and gas-rich springs

Hoke, Leonore; Poreda, Robert J.; Reay, A.; Weaver, S. D.

doi:10.1016/s0016-7037(00)00346-x

Cited by 44 publications

(40 citation statements)

References 69 publications

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“…Hoernle et al (2006) and Timm et al (2009Timm et al ( , 2010 associated volcanism near New Zealand with the removal of mantle lithosphere and partial melting of some of it. In support of this view, Hoke et al (2000) reported 3 He/ 4 He ratios consistent with upper mantle sources, but not enrichment associated with hotspots or plumes from the deep mantle. The occurrence of volcanism 200Á300 km from the most intense deformation along the Alpine Fault and its continuation into the Marlborough fault zone might indicate ongoing deformation spread over a much wider zone than seems to be seismically active.…”

Section: Submarine Volcanoes Near the Urry Knollsmentioning

confidence: 80%

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Collins

Molnár

Sheehan

2011

New Zealand Journal of Geology and Geophysics

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Multibeam bathymetric surveys east of the South Island of New Zealand yield images of submarine volcanoes and pockmarks west of Urry Knolls on the Chatham Rise, and evidence of submarine erosion on the southern margin of the Chatham Rise. Among numerous volcanic cones, diameters of the largest reach c. 2000 m, and some stand as high as 400 m above the surrounding seafloor. The tops of most of the volcanic cones are flat, with hints of craters, and some with asymmetric shapes may show flank collapses. There are hints of both northeastÁsouthwest and northwestÁsoutheast alignments of volcanoes, but no associated faulting is apparent. Near and to the west of these volcanoes, huge pockmarks, some more than c. 1 km in diameter, disrupt bottom topography. Pockmarks in this region seem to be confined to seafloor shallower than c. 1200 m, but we see evidence of deeper pockmarks at water depths of up to 2100 m on profiles crossing the Bounty Trough. The pockmark field on the Chatham Rise seems to be bounded on the south by a trough at almost 1200 m depth; like others, we assume that contour currents have eroded the margin and created the trough.

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Section: Submarine Volcanoes Near the Urry Knollsmentioning

confidence: 80%

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Collins

Molnár

Sheehan

2011

New Zealand Journal of Geology and Geophysics

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“…7.7 km/s. Similarly low mantle velocities in the SIGHT region nearby have been interpreted as thermal perturbations in the upper mantle (Hoke et al, 2000;Godfrey et al, 2001). Unfortunately, the profile of Godfrey does not have upper mantle velocities at the cross-point of the two profiles.…”

Section: Comparison With Sight Resultsmentioning

confidence: 98%

Extensional and magmatic nature of the Campbell Plateau and Great South Basin from deep crustal studies

et al. 2009

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“…4; Hoke et al 2000). Hence, the very low 3 He/ 4 He ratios derived from the Macraes sulphide sample (R/Ra ∼0.03; Fig.…”

Section: Discussionmentioning

confidence: 86%

“…4, Table 1) suggest that there was essentially no mantle helium component in the mineralising fluid. Some modern surface springs have R/Ra as high as 7, reflecting ongoing mantle helium passage to the surface (Hoke et al 2000). The extensional structures that control those springs were initiated in the middle Cretaceous at the earliest, and the Macraes data suggest that prior to that extensional event, there was negligible mantle He passing into the Otago Schist belt.…”

Section: Discussionmentioning

confidence: 99%

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Noble gases fingerprint a metasedimentary fluid source in the Macraes orogenic gold deposit, New Zealand

et al. 2016

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Ar ratios up to 200 times greater than air. Similarly, I/Cl ratios for fluids extracted from mineralised quartz are similar to those of brines from marine sediments that have interacted with organic matter and are ten times higher than typical magmatic/mantle fluids. The Macraes mineralising fluids were compositionally variable, reflecting either mixing of two different crustal fluids in the metasedimentary pile or a single fluid type that has had varying degrees of interaction with the host metasediments. Evidence for additional input of meteoric water is equivocal, but minor meteoric incursion cannot be discounted. The Macraes deposit formed in a metasedimentary belt without associated coeval magmatism, and therefore represents a purely crustal metamorphogenic end member in a spectrum of orogenic hydrothermal processes that can include magmatic and/or mantle fluid input elsewhere in the world. There is no evidence for involvement of minor intercalated metabasic rocks in the Macraes mineralising system. Hydrothermal fluids that formed other, smaller, orogenic deposits in the same metamorphic belt have less pronounced noble gas and halogen evidence for crustal fluid-rock interaction than at Macraes, but these deposits also formed from broadly similar metamorphogenic processes.

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The subcontinental mantle beneath southern New Zealand, characterised by helium isotopes in intraplate basalts and gas-rich springs

Cited by 44 publications

References 69 publications

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Extensional and magmatic nature of the Campbell Plateau and Great South Basin from deep crustal studies

Noble gases fingerprint a metasedimentary fluid source in the Macraes orogenic gold deposit, New Zealand

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