Cenozoic intraplate volcanism on New Zealand: Upwelling induced by lithospheric removal

Amphiboles from suprasubduction and intraplate lithospheric mantle

Author Posting. © The Author, 2006. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Petrology 27 (2006): 1673-1704, doi:10.1093/petrology/egl024.

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The Origin of HIMU in the SW Pacific: Evidence from Intraplate Volcanism in Southern New Zealand and Subantarctic Islands

Spatial distribution and alignments of volcanic centers: Clues to the formation of monogenetic volcanic fields

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Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia

The South Auckland Volcanic Field is a Pleistocene (1 59– 0 51Ma) basaltic intraplate, monogenetic field situated south of Auckland City, North Island, New Zealand. Two groups of basalts are distinguished based on mineralogy and geochemical compositions, but no temporal or spatial patterns exist in the distribution of various lava types forming each group within the field: Group A basalts are silica-undersaturated transitional to quartz-tholeiitic basalts with relatively low total alkalis (3 0–4 6 wt %), Nb (7–29 ppm), and (La/Yb)N (3 4–7 6); Group B basalts are strongly silicaundersaturated basanites to nepheline-hawaiites with high total alkalis (3 3–7 9 wt %), Nb (32–102 ppm), and (La/Yb)N (12–47). Group A has slightly higher Sr/Sr, similar eNd, and lower Pb/Pb values compared with Group B. Contrasting geochemical trends and incompatible element ratios (e.g. K/Nb, Zr/Nb, Ce/Pb) are consistent with separate evolution of Groups A and B from dissimilar parental magmas derived from distinct subcontinental lithospheric mantle sources. Differentiation within each group was controlled by olivine and clinopyroxene fractionation. Group B magmas were generated by <8% melting of an ocean island basalt (OIB)-like garnet peridotite source with high U/Pb mantle (HIMU) and enriched mantle (EMII) characteristics possibly inherited from recycled oceanic crust. Group A magmas were generated by <12% melting of a spinel peridotite source also with HIMU and EMII signatures. This source type may have resulted from subduction-related metasomatism of the sub-continental lithosphere modified by a HIMU plume. These events were associated with Mesozoic or earlier subductionand plume-related magmatism when New Zealand was at the eastern margin of the Gondwana supercontinent.

Petrology and Geochemistry of Intraplate Basalts in the South Auckland Volcanic Field, New Zealand: Evidence for Two Coeval Magma Suites from Distinct Sources

Roger M. Briggs

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Petrology and Geochemistry of Intraplate Basalts in the South Auckland Volcanic Field, New Zealand: Evidence for Two Coeval Magma Suites from Distinct Sources