East Pacific Rise (8-11ºN): Recent EPR highlights

List new observations about EPR data (i.e. since the 2008 EPR ISS workshop) in 1-2 sentences

What do we know this year that we did not know last year???

– volcanic/crustal
    •    AST did not drastrically change shape since 2005-06 eruption (Soule, in press)
    •    Systematic variations in the tidal triggering of microearthquakes within the hydrothermal circulation cell at 9º50'N EPR is used to calculate the diffusive lengthscale, or how far in the lateral direction pore pressure perturbations can propagate through the hydrothermal cracking zone, to estimate crustal permeability at 10-13 to 10-12 m2 (Stroup et al., 2009).
    •    At finescale the AMC near 9 50’N is not fully homogenizing the geochemistry of magmas, as reflected in the 1991-92 and 2005-6 lava flows (Goss et al., in prep)
    •    New eruption lavas are different (more evolved and cooler), but no new pulse of mantle material
    •    2005-06 eruption
    ◦    Lava flows extend to 3 km from ridge axis on eastern side (Fundis & Soule, in prep).
    ◦    lavas display geographical variation in eruption ages, as they did in 1991-92 (Rubin et al., in prep) and patterns in short-lived radisotope signatures that constrain magma accumulation times to decades (Russo-Rubin in prep).
    •    Off-axis pillow ridges and “hummocky” topography appear to form 4 km and beyond (link to crustal seismics)
    •    New seismic data:
    ◦    There are off-axis magma lenses in a few locations on the flanks between 3-5 km off axis, 3-6 km at multiple levels in the crust
    ◦    Two series of off-axis lenses on east flank
    ◦    Small lens on west flank near 9 52’N and under youngest Lamont Smt (Sasha)
    ◦    Magma lens segmented along axis into en echelon that vary subtly in depth and dip. Are correlated with surface 4th order segmentation (offsets in the AST)
    •    Dacites and evolved compositions occur on the axis in southern part of the ISS (9 N)
    •    Model of magma convection and heat flux in order to maintain a hydrothermal system, magma chamber doubles in size on decade timescale (Liu and Lowell)- Currently looking at variable replenishment rates and non-basalt composition coupled with numerical models of two-phase flow

hydrothermal thruough the Water Column
    •    Higher Upper crustal permeability structure beneath vents and inferred down-flow zones (see Stroup et al., 2009 bullet above)
    •    Magmatic input felt by the h-therm system down to 9 39.5’N vent in volatile phase (Lilley) - (perturbations were felt even further south in 1991-92, but we didn't look that far south this time around)
    •    Perturbation by eruption is still seen in volatiles in the hydrothermal plumes after 2-3 years, from 1991 eruption the perturbation lasted 1 year
    •    Tica vent: tubeworms survived, mussels carried by lava flow 100 m; more kipukas left after 1991 eruption left more biota intact (Shank et al.,)
    •    Pre-eruption/post-eruption diffuse flow chemistry (Luther)
    •    Water column plume data from LADDER (Mullineaux-Thurnherr) and larval retention along EPR
    •    Inorganic/organic particle microaggregation is a significant process within EPR neutrally buoyant plumes – with important implications for particle/seawater reactions, particle transport, and water column microbial activity (Breier et al. in prep.). These results come from a novel suspended particulate timeseries collected within 25m of Tica and a 3 day, 24 point time-series data for plume particulate major and trace element composition.
    •    Hydrothermal Flow measurements (Lowell et al) of EPR diffuse flow sites on December cruise
    •    Microbial colonization experiments at diffuse flow vents show similar succession where chemistry is similar
    •    KVD group update (contact J. Bryce for details):
    ◦    M & Q temp, Cl, Si vent time series paper (in prep)
    ◦    All vents time series Temp, Cl, Si, H2S paper (in prep)
    ◦    Major element data - Planned manuscripts submission for spring of 2010
    ◦    Trace Metal and Metal budget analysis for high temperature and diffuse flow fluids from the Nov. 2004, Jun-Jul. 2006, Nov-Dec. 2006, Nov-Dec. 2007 cruises is ongoing. A manuscript based on a subset of this work focusing on degassing metals and including 210Pb activities for fluids is currently in prep.
    ◦    Sr isotope analysis multiple vents and time series
    ◦    Finally, we plan to archive in VentDB individual analyses of fluid in support of endmember vent compositions previously published by Von Damm (with the support of a Ridge2000 award) as well as all data from future publications.

Pre and post eruption - temporal and spatial linkages?:
What stayed the same?
    •    AST shape
    •    Many of the Hi-T vent locations
    •    Expression of mantle source composition in the magmas
    •    Segmentation signal in geochemical tracers in the lava
    •    Megafauna sequence basically the same (some new species, maybe new to 9N or maybe better sampling resolution)
    •    V (marker 7) vent: mussels survived (although colonization)
    •    No detectable change in the depth and width of AMC
    •    Segmentation of melt in AMC has not changed from 1985 to 2008

What changed?
Everything else…

List new publications (e.g. published papers, theses, abstracts, manuscripts in prep)

Breier, J.A., B. M. Toner, S. Fakra, S. J. Manganini, and C. R. German, The influence of micro-aggregate formation on deep-sea hydrothermal plume chemistry and particle transport: 9° 50' N East Pacific Rise, Earth and Planetary Science Letters, In Prep.

Dziak, R.P., D.R. Bohnenstiehl, H. Matsumoto, M. Fowler, J. Haxel, M. Tolstoy, F. Waldhauser, Recent Volcanic Eruptions, Properties and Behaviour of the EPR 8 degrees-11degrees N, Geochem., Geophys. and Geosyst., 10, Q06T06, doi:10.1029/2009GC002388, 2009.

Goss, AR Perfit, MR, Kamenov, GD, Rubin, KH, Fundis, AT, Soule, SA Fornari, D J(2008) Geochemical Characterization of Axial and Off-axis Lavas From the 2005-06 Eruption Along the East Pacific Rise (9̊46-56' N): Implications for AMC Composition Over Decadal Time Scales and Mantle Heterogeneity Along Fast Spreading Centers, Eos Trans. AGU, 89, Fall Meet. Suppl., Abstract # B21A-0330

Monigle, P.W., D.R. Bohnenstiehl, M. Tolstoy, and F. Waldhauser (2009), Seismic Tremor at the 9°50’N East Pacific Rise Eruption Site, G-cubed, doi:10.1029/2009GC002561, in press.

Rubin, KH, Soule, SA, Fornari, DA, Perfit, M, Russo, C, Tolstoy, M (2009) "Spatial and Temporal Pulses of a Recent Mid-Ocean Ridge Eruption Revealed by Radiometric Dating and in Situ Observation", in prep.

Rubin, KH, Tolstoy, M, Fornari, D J, Dziak, R P, Soule, S A, Waldhauser, F, Von Damm, K L (2008) Integrating Radiometric, Geophysical and Thermal Signals of Volcanic Unrest and Eruption in 2005-06 at 9 deg 50'N EPR, Eos Trans. AGU, 89, Fall Meet. Suppl., Abstract # B23F-07

Stroup, D. F., M. Tolstoy, T. J. Crone, A. Malinverno, D. R. Bohnenstiehl, and F. Waldhauser (2009), Systematic along-axis tidal triggering of microearthquakes observed at 9°50′N East Pacific Rise, Geophys. Res. Lett., 36, L18302, doi:10.1029/2009GL039493.

Soule, S.A., Escartin, J.E., Fornari, D.J. (2009) A record of eruption and intrusion at a fast-spreading ridge axis: the axial summit trough of the East Pacific Rise 9˚-10˚N, G-cubed, doi:10.1029/2008GC002354, in press.

White, S, Soule, SA, Tolstoy, M, Waldhauser, F, Rubin, K (2008) Volcanic Eruptions of the EPR and Ridge Axis Segmentation: An Interdisciplinary View, Eos Trans. AGU, 89, Fall Meet. Suppl., Abstract # B21A-0329

White, Scott M., Jessica L. Mason, Ken C. Macdonald, Michael R. Perfit, V. Dorsey Wanless, Emily M. Klein (2009) Significance of widespread low effusion rate eruptions over the past two million years for delivery of magma to the overlapping spreading centers at 9°N East Pacific Rise, Earth and Planetary Science Letters xxx, xxx–xxx

2008 EPR Integration & Synth Workshop Report
http://www.ridge2000.org/science/downloads/meetings/reports/epr08.pdf