Abrupt spatial and geochemical changes in lamprophyre magmatism related to Gondwana fragmentation prior, during and after opening of the Tasman Sea

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

“…Locations of intraplate magmatic activity are indicated with colour corresponding to type, see legend. After Storey et al (1999), Tulloch et al (2009, Timm et al (2010) and van der Meer et al (2016). CMIP: Central Marlborough Igneous Province, a location of alkaline intraplate magmatism in the Eastern Province, Cretaceous location is uncertain.…”

“…There is no evidence for mantle plume activity, since magmatism has occurred repeatedly in restricted areas over 10's of Ma (e.g., Panter et al, 2006) and has a small total volume (e.g., Finn et al, 2005). Furthermore, age progressive hot spot tracks are absent (Timm et al, 2010) and some magmatism appears to be controlled by local tectonics (e.g., Cooper et al, 1987;Waight et al, 1998a;van der Meer et al, 2016). Current hypotheses on the cause of melting a HIMU-like source either invoke delamination of enriched mantle from near the base of lithosphere due to gravitational instabilities, promoting melting of amphibole veins + peridotite (Panter et al, 2006;Sprung et al, 2007) or melting of peridotite ± pyroxenite in the asthenosphere due to decompression (Hoernle et al, 2006;Timm et al, 2009Timm et al, , 2010McGee et al, 2013).…”

“…Whereas the Eastern Province occurrences are concentrated in volcanic eruptive centres, Cretaceous intraplate magmatism in the Western Province occurs as widely distributed predominantly lamprophyric dikes (Waight et al, 1998a;van der Meer et al, 2013van der Meer et al, , 2016. The oldest intraplate dikes occur in the south Westland area and were emplaced at 102-100 Ma (van der Meer et al, 2016) (Fig.…”

“…New Zealand contains a prolonged record of repeated continental alkaline intraplate volcanism erupting over the last ∼100 Ma (e.g., Timm et al, 2010;van der Meer et al, 2016). This time period spans from when the now largely undersea continent of Zealandia was part of the Gondwana margin, through Late Cretaceous extension and separation from Antarctica and Australia, up to the present day (Fig.…”

“…There is, however, no consensus on the origin of this HIMU-like source, where it resides, and why it is repeatedly tapped. 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).…”