Dr Marco Brenna

Research Interests

My research spans the interface of magmatic and volcanic processes. I investigate the chemical and petrologic characteristics of igneous rocks to unravel their history. I focus mainly on intraplate alkalic systems such as the Auckland Volcanic Field or the Dunedin Volcano, but have also studied recent eruptions at calc-alkalic arc volcanoes, at Mount Tongariro and Hunga Ha'apai (Tonga). Outlined here are some of my ongoing research projects:

• Magma generation and ascent dynamics in small-volume intraplate basaltic volcanic systems. My study of the Jeju Island intraplate volcano in South Korea left me with several questions on the mechanisms that allow small-volume and diverse magma batches to erupt in laterally and temporally dispersed volcanic systems. I am currently measuring rates of elemental diffusion in xenocrystic mantle olivines in the Auckland Volcanic Field to estimate rates of magma ascent. The next step will be to model the process of magma accumulation in the mantle and mechanisms triggering ascent.
• Formation of phonolite-trachyte lineages in intraplate alkalic volcanoes. The Dunedin Volcano (and many others) is composed of lavas ranging in composition from basalt to trachyte and phonolite. Some of these lavas contain mantle peridotite xenoliths, indicative of their fast ascent. Together with colelagues at INGV Rome we are experimentally investigating the conditions that lead to the formation of different magmatic liquid lines of descent.
• Characterization and eruption dynamics of the 2014-2015 eruption of Hunga Ha'apai (Tonga). I visited and sampled the newly born volcanic cone at Hunga Ha'hapai together with colleagues from the University of Auckland. We collected data ranging from rock samples to characterize the eruption both chemically and physically, underwater bathymetry to reveal features of previous eruption, and drone images of the whole island to generate a 3D model of erosional features.

In addition to these specific projects, I also work on intrusive and extrusive igneous rocks as far afield as Western Australia, Saudi Arabia, Korea and Japan.

A section through a small basaltic volcano at Jeju Island showing the transition from phreatomagmatic-dominated to magmatic-dominated eruption phases.

Precipitous basalt and trachyte cliffs at Ulleung Island.

Inspecting the volcanic deposits from the 2009 and 2015 eruptions at Hunga Ha'apai, Tonga.

Peeking into the crater of the 2012 Te Maari eruption at Mount Tongariro

Teaching

• GEOL 112 Dynamic Earth: A New Zealand Perspective
• GEOL 251 Minerals and Rocks
• GEOL 276 Geological Resources for a Sustainable New Zealand
• GEOL 344 Advanced Field Studies
• GEOL 376 Geological Resources for a Sustainable New Zealand
• GEOL 422 Geochemistry, Petrology, Volcanology
• GEOL 464 Advanced topics in Igneous Processes

View available student research opportunities