Inaugural UK Broadband OBS Experiments Nicholas Harmon-University of Southampton, UK

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1 Inaugural UK Broadband OBS Experiments Nicholas Harmon-University of Southampton, UK VOILA Volatile recycling In the Lesser Antilles arc PILAB/EuroLAB Passive Imaging of the Lithosphere Asthenosphere Boundary

2 Passive Imaging of the Lithosphere Asthenosphere Boundary (PILAB) Seismology (NERC, ERC) PI: Catherine Rychert, University of Southampton, UK Co-I: Nicholas Harmon, University of Southampton, UK Co-I: Mike Kendall, University of Bristol, UK Marine EM PI: Steve Constable

3 What makes a plate, plate-like What mechanism(s) define the tectonic plate, temperature, composition, melting in the asthenosphere?

4 Different ways the Lithosphere Asthenosphere is defined

5 Observations between seismic methods, resistivity are not straight forward to interpret, not all made at the same locations and with varying resolution.

6 Possibilities for the defining mechanisms for the LAB

7 PILAB/EUROLAB, BBOBS and OBMT

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9 Complementary Studies with International Partners Satish Singh, IPGP Deep Seismic Reflection Wayne Crawford, IPGP Seafloor Compliance Ingo Grevemeyer, GEOMAR Seismic Refraction

10 VoiLA Volatile recycling in the Lesser Antilles arc Processes and Consequences Oct 2015-Sep 2019 Funded by: Université des An-lles de la Guyane University of West Indies

11 Water affects: Plate Coupling Mantle Dynamics Wedge Flow 200 km UM LM Vola;le cycling into deep mantle

12 Climate Mineral resources Agriculture Earthquakes & Tsunami Eruptions

13 Subduction Zone Diversity Slow Fast US & Japan ( ) US & Japan ( ) Slow slab

14 Vola?le input: serpen?nised oceanic lithosphere Oceanic Core Complexes discovered in 1997 at the Atlan-s FZ, MAR. Only formed at slow-spreading oceanic crust. Completely different oceanic lithosphere architecture. Serpen?nisa?on of large areas at seabed. Mid-Atlan?c Ridge

15 Our understanding of oceanic lithosphere hydra-on is rudimentary. Global Subduc?on Water Budget Es?mate based on Pacific Insights Hacker (2008)

16 Why An?lles? VoiLA Expect slow-formed Atlan-c crust to have a fundamentally different water distribu-on than Pacific Ocean crust. An-lles most accessible slow subduc-on system Global end-member of subduc-on systems.

17 Variability along An?lles arc Seismicity increases from south to north Large historic interplate earthquakes in center only Double arc in north Largest islands, magma?c produc?vity in center Difference in back-arc bathymetry south to north Thick sediments in south, pelagic only in north Geochemical signatures reflects sediments in source + fluids? GPS indicates coupled forearc block in north, uncoupled in south.

18 Incoming plate characteris?cs North Age 90m.y., Vconv 2 cm/yr dip 50 Thin sediments ATLANTIC PLATE Thick sediments CARIBBEAN PLATE

19 WP1 INPUT Distribution of hydration of incoming plate Research programme VoiLA WP3 OUTPUT Arc structure volcanism WP4 CONSEQUENCES Relation of seismicity, volcanism and metal fractionation to fluid distribution WP5 SYNTHESIS Global comparison and broader implications earthquakes WP2 PATHWAYS Wedge structure and flow

20 Geophysical Experiments Bathymetry (m) WP2 Passivesource experiment FZ Marathon FZ WP1 Ac-vesource experiment WP3 Along-arc shoot 14 Mercurius FZ Vema FZ 12 Doldrums FZ km (is)land sta;ons earthquakes

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22 Project Team Seismology Mantle Geochemistry Collier, Rietbrock, Henstock, Kendall, Harmon, Rychert Blundy Crustal Petrology/Geochemistry Numerical modelling Davidson, Macpherson, Wilkinson, Wilson Van Hunen, Goes

23 VoiLA Ø produce the first high resolution image of slowspread (Atlantic) subduction-arc system Ø determine pathways of fluid subducted and recycled via serpentine Ø identify links between volatile recycling seismicity, volcanism and metal pathways First integrated analysis of an Atlantic subduction zone