Diffusion-zoned pyroxenes in an isotopically heterogeneous mantle lithosphere beneath the Dunedin Volcanic Group, New Zealand, and their implications for intraplate alkaline magma sources

Dalton, Hayden; Scott, James M.; Liu, Jingao; Waight, Tod E.; Pearson, D. Graham; Brenna, Marco; Roux, Petrus le; Palin, J. Michael

doi:10.1130/l631.1

Cited by 32 publications

(22 citation statements)

References 65 publications

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“…As the metamorphic event is present only in the lower crust, one option is that some change in the configuration of the subduction zone led to interaction and conductive heating of the lower crust by hot upper mantle (e.g., Collins, ). Calculated equilibration temperatures for Late Cretaceous to Cenozoic peridotite xenoliths exhumed across southern Zealandia, including some extracted from the Kakanui Mineral Breccia, have revealed that this mantle lithosphere was hot and relatively thin (Dalton et al., ; Scott, Brenna, et al., ; Scott, Hodgkinson, et al., ; Scott, Liu, et al., ; Scott, Waight et al., ). The geodynamic plausibility of mantle heating is investigated below.…”

Section: Discussionmentioning

confidence: 99%

High‐ to ultrahigh‐temperature metamorphism in the lower crust: An example resulting from Hikurangi Plateau collision and slab rollback in New Zealand

Jacob

Scott

Turnbull

et al. 2017

Journal Metamorphic Geology

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Lower crustal xenoliths erupted from an intraplate diatreme reveal that a portion of the New Zealand Gondwana margin experienced high‐temperature (HT) to ultrahigh‐temperature (UHT) granulite facies metamorphism just after flat slab subduction ceased at c. 110–105 Ma. P–T calculations for garnet–orthopyroxene‐bearing felsic granulite xenoliths indicate equilibration at ~815 to 910°C and 0.7 to 0.8 GPa, with garnet‐bearing mafic granulite xenoliths yielding at least 900°C. Supporting evidence for the attainment of HT and UHT conditions in felsic granulite comes from re‐integration of exsolution in feldspar (~900–950°C at 0.8 GPa), Ti‐in‐zircon thermometry on Y‐depleted overgrowths on detrital zircon grains (932°C ± 24°C at aTiO2 = 0.8 ± 0.2), and correlation of observed assemblages and mineral compositions with thermodynamic modelling results (≥850°C at 0.7 to 0.8 GPa). The thin zircon overgrowths, which were mainly targeted by drilling through the cores of grains, yield a U–Pb pooled age of 91.7 ± 2.0 Ma. The cause of Late Cretaceous HT‐UHT metamorphism on the Zealandia Gondwana margin is attributed to collision and partial subduction of the buoyant oceanic Hikurangi Plateau in the Early Cretaceous. The halt of subduction caused the fore‐running shallowly dipping slab to rollback towards the trench position and permitted the upper mantle to rapidly increase the geothermal gradient through the base of the extending (former) accretionary prism. This sequence of events provides a mechanism for achieving regional HT–UHT conditions in the lower crust with little or no sign of this event at the surface.

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Section: Discussionmentioning

confidence: 99%

High‐ to ultrahigh‐temperature metamorphism in the lower crust: An example resulting from Hikurangi Plateau collision and slab rollback in New Zealand

Jacob

Scott

Turnbull

et al. 2017

Journal Metamorphic Geology

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“…This implies that the intraplate magmas are unlikely to be derived from melting of ancient pyroxenite/eclogite residing in the asthenospheric mantle. Under the proposed asthenosphericsource model (Hoernle et al, 2006;Timm et al, 2010;McGee et al, 2013), the observed enrichment of lithospheric mantle documented by Scott et al (2014aScott et al ( , 2014b, McCoy-West et al (2016), Scott et al (2016) and Dalton et al (2017) would have occurred when enriched basaltic melts derived from melting of carbonated pyroxenite in the asthenosphere ascended through the lithosphere. However, this is inconsistent with (1) the lack of radiogenic 207 Pb/ 204 Pb ratios associated with ancient enriched domains; (2) the presence of cooling diffusion profiles of pyroxenes in the Cenozoic-erupted peridotite xenoliths which require that lithospheric mantle enrichment occurred before xenolith entrainment (Scott et al, 2014a(Scott et al, , 2014bMcCoy-West et al, 2016;Dalton et al, 2017); and (3) the unradiogenic Pb isotopic compositions for the local asthenosphere in the Cretaceous, as approximately represented by Tasman MORB (Mortimer et al, 2012).…”

Section: Mantle Source Of the Westland Dike Swarmmentioning

confidence: 96%

“…La/Yb) and carbonatitic signatures e.g. low Ti/Eu (Scott et al, 2014a(Scott et al, , 2014bMcCoy-West et al, 2016;Dalton et al, 2017). Unmetasomatised portions of lithosphere under the former fore-arc area have distinctly more radiogenic Nd (>+15.5) and extend to less radiogenic Sr (∼0.702) compositions (Scott et al, 2014b;McCoy-West et al, 2016;Dalton et al, 2017).…”

Section: Zealandia's Lithospheric Mantlementioning

confidence: 98%

“…At typical temperatures for spinel facies lithosphere (900-1100 • C), slow diffusion of REE and related elements will result in isotopic disequilibrium in Nd and Hf between metasomatised and depleted domains within the lithosphere (e.g. Dalton et al, 2017). Therefore, melts from fusible and enriched lithosphere domains will dominate melt compositions.…”

Section: Mantle Source Of the Westland Dike Swarmmentioning

confidence: 98%

“…A suite of Sr-Nd-Pb-Hf isotope data from the most geographically extensive -but least studied -intraplate occurrence in New Zealand (the Cretaceous Westland Dike Swarm, Waight et al, 1998a;van der Meer et al, 2013van der Meer et al, , 2016, coupled with published data from elsewhere in Zealandia, is used here to examine the mantle sources for these intraplate alkaline magmas. Our dataset comprises 49 new samples and >150 published samples and is the first to be compared against the Zealandia peridotite mantle SrNd-Pb-Hf isotope reference frames recently established by Scott et al (2014aScott et al ( , 2014bScott et al ( , 2016, Czertowicz et al (2016), McCoy-West et al (2016) and Dalton et al (2017). This dataset permits analysis of the temporal and spatial isotopic variability of intraplate magma sources on a continental-scale.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Variable sources for Cretaceous to recent HIMU and HIMU-like intraplate magmatism in New Zealand

Meer

Waight²,

Scott

et al. 2017

Earth and Planetary Science Letters

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Anatomy of Intraplate Monogenetic Alkaline Basaltic Magmatism

Brenna

Ubide

Nichols

et al. 2021

Geophysical Monograph Series

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Intraplate basaltic systems, often occurring as fields of small monogenetic volcanoes, are dominated by eruption of alkaline basaltic rocks, ranging from nephelinite/basanite to transitional/subalkaline. Their generally primitive erupted compositions imply limited crustal modification, and hence they provide an important probe into deep, lithospheric mantle and partial melting processes. Partial melting and magmatic ascent processes can be investigated using the composition of crystals, glass and wholerock, although a combination of these is preferable. The whole-rock chemical variability within single eruptions or over the temporal and spatial extent of a volcanic field is controlled by the characteristics of the primary melting source, as well as near source percolative/reaction processes. Coupled crystaland -whole-rock detailed investigations are most promising to constrain the processes that modify primary melts into the primitive magmas that accumulate before ascent. Complex crystal textures and chemistry have so far demonstrated that basaltic magmas are principally processed and modified within the lithospheric mantle with minor modification en-route through the crust. Fractional crystallization and magma mixing modify melts throughout ascent, and can imprint secondary chemical intra-eruptive variability. Quantifiable temperature and pressure parameters based on crystalmelt compositions constrain the depth of formation, and hence provide information about the role of different mineral phases in deep versus shallow chemical evolution. Volatile components in the melt (e.g. H2O and CO2) can be quantified on glass and melt inclusions. These analyses, coupled with solubility models, may help to reconstruct initial dissolved volatile content to further constrain the source characteristics and magmatic ascent dynamics. Integrated studies of crystals and melt paint a picture of extended lithospheric mantle to minor crustal processing resulting from the complex deep plumbing of monogenetic basaltic systems. This highlights the need for improved resolution to characterize true primary signatures and hence elucidate the formation of intraplate alkaline basalts.

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Diffusion-zoned pyroxenes in an isotopically heterogeneous mantle lithosphere beneath the Dunedin Volcanic Group, New Zealand, and their implications for intraplate alkaline magma sources

Cited by 32 publications

References 65 publications

High‐ to ultrahigh‐temperature metamorphism in the lower crust: An example resulting from Hikurangi Plateau collision and slab rollback in New Zealand

High‐ to ultrahigh‐temperature metamorphism in the lower crust: An example resulting from Hikurangi Plateau collision and slab rollback in New Zealand

Variable sources for Cretaceous to recent HIMU and HIMU-like intraplate magmatism in New Zealand

Anatomy of Intraplate Monogenetic Alkaline Basaltic Magmatism

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