Arc Rifting, metallogeny and microplate evolution: An integrated geodynamic, magmatic and hydrothermal study of the Bismarck Archipelago, Papua New Guinea
The metallogenic diversity of the Earth`s crust is closely related to complex tectonic processes at the plate margins. Some of the most metal-endowed continental crust on Earth is forming today in complex subduction zone settings of the Western Pacific. In easternmost Papua New Guinea, recent crustal growth and ore formation is driven by arc-continent collisions, subduction reversals, and continuous metasomatism of the mantle wedge, resulting in recycling and addition of volatiles and metals. Several of the world`s largest Cu and Au deposits have formed in this region over the last 2-3 million years, and some are still forming today. However, geodynamic models of the region are constructed at a very broad scale with an uncertain link to ongoing magmatism, the local neotectonic framework and the role of the lithospheric basement. The proposed project will use an integrated approach of high-resolution multibeam mapping, seismology, magnetotellurics, heat flow, geochronology and petrology/geochemistry to obtain the first comprehensive view of one of the world’s most complicated yet mineral-rich belts and attempt to address a major unsolved question about the region: why has so much metal been added to the crust at this location?
Sketch of the geodynamic situation around Lihir that led to the formation of a prospective corridor for gold-rich mineral mineralization. Cruise SO299 aims to scientifically test this conceptual model. Source: Brandl et al., 2020.
The cruise starts in Townsville and the duration of the transit to the work area is estimated at 3.5 days. The work program begins with the deployment of the Ocean Bottom Seismometer (OBS) and Ocean Bottom Electro-Magnetic (OBEM) network in the sea area around the Lihir island group. The following ~14 working days will be devoted to an intensive program of detailed exploration of the volcanic field south of Lihir. Here we will deploy heat flow probe, TV-guided grab and the ROV Kiel 6000. Further work will focus on the Feni Deep and the tectonics and structure of the crust south of New Ireland. Here a number of translithospheric fault systems (Weitin/Sapom faults) are present and their connection and possible tectonic link to the New Britain Trench shall be investigated. Areas (6-8 km water depth) that are inaccessible to ROV and TV-grab will be sampled using a chain bag dredge. Susequently, the New World Seamount northwest of Lihir and the so-called "Mussel Cliff" will be studied in detail. Finally, we will recover the OBS and OBEM equipment before transiting to the Mussau Trench. Here, initial mapping and rock sampling will be carried out at thus largely unknown lithospheric structure. The final transit to the port of Singapore is calculated with 13 days.
Brandl, P.A., Hannington, M.D., Geersen, J., Petersen, S.& Gennerich, H.-H.: The submarine tectono-magmatic framework of Cu-Au endowment in the Tabar-to-Feni island chain, PNG. Ore Geology Reviews 121, invited. doi:10.1016/j.oregeorev.2020.103491.(Open Access)