Brothers Arc Flux
Auckland to Auckland, New Zealand
Expedition 376 will investigate the fundamental, interrelated processes governing subseafloor hydrothermal activity at Brothers volcano, southern Kermadec arc (IODP proposal 818-Full2). The primary objectives are to (1) Characterize the subsurface, magma-derived volatile phase for testing models predicting the existence of either a single-phase gas or a two-phase brine-vapor; (2) Explore the distribution of base and precious metals and metalloids at depth as well as the reactions that have taken place during their precipitation along fluid migration pathways to the seafloor; (3) Quantify the mechanisms and extent of fluid-rock interaction, and what this implies for the mass flux of metals and metalloids to the ocean as well as the role of magma-derived carbon and sulfur species in acting as agents for those fluxes; and (4) Assess the diversity, extent, and metabolic pathways of microbial life in an extreme, acidic, and metal-toxic (sub)volcanic environment.
The ultimate scientific goal of Expedition 376 is to discover the key processes that distinguish submarine arc-hosted hydrothermal systems from those linked to spreading centers, which results from the flux of magmatic fluid commonly being much higher in volcanic arcs. As a consequence of their shallow water depths and high volatile contents, the magmatic-hydrothermal arc signature gives rise to different fluid compositions and thus mineralization compared to submarine extensional settings. This likely also has consequences for the associated biota. Additionally, given the very acidic fluids and high metal concentrations, submarine arc hydrothermal systems are thought to be important analogs to porphyry copper, epithermal gold, and various volcanic rock-hosted massive sulfide deposits mined on land. Drilling Brothers volcano will provide essential information for understanding the formation of those mineral deposits and will also reconstruct the volcanic stratigraphy of this arc volcano.
Operations will focus on discharge zones of geochemically distinct fluids in and around the caldera of Brothers volcano by drilling and logging to 100s of m. The drill sites show variable impact of magmatic volatiles, which will enable the expedition to directly study the implications of magma degassing for the transport of metals to the seafloor and how this affects the functioning of microbial life.
- Petrologists (igneous/metamorphic/sulfide)
- Structural geologists
- Borehole geophysicists
- Inorganic/organic geochemists
To learn more about the scientific objectives of this expedition and the technical plans, please join a web-based seminar on Wednesday, 15 March 2017 at 1:00 pm EDT (日本時間：3月16日 午前2時 ).
To participate in the webinar, you need access to the Internet and a computer with a speaker and microphone (optional). To register, click the following link: Exp 376 webinar.