Understanding the Earth Using the Geochemistry of Volcanic Rocks
Jim in 2017 happily holding lava dredged from his volcano in the Havre Trough north of New Zealand (see below). It is a 1 Ma primitive rear-arc basalt, a rock type that he made famous for coming from enriched mantle to which a depleted slab component was added around 200 km beneath the volcano. The same process is now known to occur globally. This one swiftly followed splitting the Kermadec arc and removing the mantle that fed it (Gill et al., 2021).
Gill Volcano in the Havre Trough is roughly the same size as Taranaki Volcano in the SW North Island of New Zealand that lies in a similar tectonic setting and erupts similar magmas. The mountain is ~1700 m high, but its peak is ~1200 m below sea level. The main map is centered on coordinates 178°28.88′ E, 34°37.17′ S, with surrounding bathymetric data highlighting the edifice. Insets show different perspectives of the bathymetry. The red dots show dredge sampling sites.
