Volcanic arc initiation and evolution

The process of Plate Tectonics began nearly 3 billion years ago and since had a profound effect on the environment of our planet. One of the fundamental questions in Earth Sciences is associated with the knowledge of how this process began and what are the conditions tolerating its operation that is blamed for the creation of the continents. The Izu-Bonin-Marianas (IBM) arc-basin intraocenic system in the Western Pacific provides a unique opportunity to address some of these vital questions as it is away from any continental landmass and its tectonic and volcanic history from inception of subduction-related volcanism (~52 M.yrs. ago) to its current state are accessible via modern deepsea drilling. Accordingly, the IBM has been extensively studied in the last 3 decades via DSDP, ODP and now IODP drilling and dredging. As a result the tectonic and volcanic processes operating in the IBM arc in the last 23 M.yrs. (Neogene) are relatively well understood. Problematic is the fact that the early (Paleogene) arc record immediately following the birth of the IBM arc-basin system is currently not available and thus the first part of the story of arc inception and the subsequent creation of arc crust remains incomplete.

It is anticipated that during IODP expedition 351 (Site IBM-1) the entire Cenozoic volcanogenic sedimentary record will be recovered. This 1.3 km thick sequence will include the first 25 M.yrs. of volcanic arc activity immediately after the subduction zone began to operate in the Eocene. Using nanofossil evidence (and Ar-Ar dating- not this proposal) will allow the reconstruction of the progressive compositional variations associated with the profound changes following the transition from pure mid-ocean-ridge type environment to gradually maturing arc crust created at volcanic fronts (IBM). One particularly powerful tool to explore this transition is by the use of (now classical) geochemical tracers sensitive to all major constituents involved in the magma generation at arcs- mantle, altered oceanic crust, sediments, seawater and slab fluid.

I have chosen a combination of Sr-Nd-Pb and B isotopes to study carefully selected (fresh and with known ages) and well characterised (shipboard ICP data and Leeds electron microscopy-this study) Paleogene volcanic ash and volcaniclasts from Site IBM-1. Boron is not abundant in the mantle and its isotopes fractionate tremendously and in unique fashion during seawater alteration and/or dehydration of the subducted sediments, oceanic crust or serpentinites. The isotopes of Pb have been shown to be an excellent tracer for the nature and provenance of the mantle in the Western Pacific (Indian Ocean versus Pacific Ocean domains) and Sr, Nd and B are all sensitive to the variety of types of subducted sediments and fluids/melts originating from them that may be involved in all stages of the subduction process. My goal will be to complete the gap in the existing isotope records across the IBM. This will uniquely allow the quantitative assessment of the volumes and roles that particular end-members in the "Subduction Factory" play in the development of the IBM arc crust. Indirectly these results will be applicable to any other subduction zone setting. They will provide the geodynamic modelling community with insights for the currently unknown rates and volumes of ingredients involved in the crust generation.

Specific beneficiaries are:

-Mineral Resources industry: Sulphide minerals host a large fraction of the crustal budget of economically important elements, including many of the critical raw materials identified by both NERC ('Sustainable use of Natural Resources' Theme) and the EU ('EU-14 Critical Raw Materials') as those on which the European (and in fact the global) economy depends upon, but which might be at risk of supply disruptions. Island arcs host the largest copper deposits in the world as well as large quantities of the important sulphide minerals for extraction of lead, zinc and gold, among others. Fundamental understanding of the creation and maturation of the volcanic arc environments in comparison to the precursor oceanic crust and mantle will help understand the conditions and circumstances leading to formation of sulphide deposits and the accumulation of the related economically important elements. How are these elements transported, stored and distributed in the arc crust is often the key for finding and successfully exploring commercially important mineral resources. I envision the biggest impact to be achieved by publishing the results of my findings in journals shown to have impact in the mining industry and to disseminate knowledge to people currently employed by the mineral industry at international scientific conferences such as the AGU and IAVCEI. I plan to speak directly with representatives from the mineral industry, who Univ. of Leeds is very well connected with via its "Minerals Pathway" degree (http://www.see.leeds.ac.uk/admissions-and-study/undergraduate-degrees/career-paths/pathways/minerals). Recently my institute hosted a workshop on this topic related to the rare metals and planning of consortium within the scope of NERC call "Security of Supply (SoS) of Minerals. I plan to report my findings for IBM at their next meetings and become involved. I shall promote the importance of the links between mineral deposits and the understanding of arc volcanic basement evolution. A talk to the Leeds Student Society of Economic Geologists (SEG) will also be arranged.

-Schools and Universities: The plate tectonic cycle and the initiation and maturation of island arcs are fundamental to planet habitability but are also important in terms of natural hazards, mineral resources and Earth processes. I believe there is an opportunity to use IODP research in the IBM as the perfect tool for demonstrating the interconnectedness of Earth processes and how they can affect us. How the Earth's mantle can transition and change so fundamentally in order to give birth to the volcanoes of the very active "Pacific Ring of Fire"? Please see our "Pathways for Impact" statement on how this can be achieved with the use of the IODP and University of Leeds infrastructure.

-Hazard Prediction & Prevention Centers /Volcano Observatories/Insurance Industry: What are the hazards related to the maturation of the arc volcanism? How understanding of the IBM arc evolution may lead to better hazard predictions? Because my results will be directly linked to important parameters used by the volcanic hazard evaluations (eruption frequencies, eruption styles- above versus below sea level, distribution and properties of the volcanic ash, volcano explosiveness, volcanic regional structure and longevity of eruptive vents, etc.) I think my study will have direct impact on the models of volcanic hazards in the W. Pacific and more specifically in Japan. The best way for impact is for my science to be communicated at international scientific meetings that organise sessions dedicated on volcanic hazards. I plan to attend the IAVCEI General Assembly' 2015 in Prague. This is the largest volcanological congress and I feel it will be an excellent exposure for my research findings to be noticed by volcanic hazard modellers and representatives of volcano observatories and the insurance industry (who usually attend the IAVCEI meetings).