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Noble gas and carbon studies of intraplate volcanoes, strike-slip, convergent and divergent plate boundaries. Evelyn Füri, December 9 th 2008. Introduction. Tschingelhörner – Glarus thrust. Matterhorn. Garnet peridotite. Gneiss. Introduction. Geysir, Iceland. R/V Atlantis. SIO.
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Noble gas and carbon studies of intraplate volcanoes, strike-slip, convergent and divergent plate boundaries Evelyn Füri, December 9th 2008
Introduction Tschingelhörner – Glarus thrust Matterhorn Garnet peridotite Gneiss
Introduction Geysir, Iceland R/V Atlantis SIO Volcan Irazu, Costa Rica
Introduction The Fluids and Volatiles Laboratory, SIO • Noble gases (He, Ne, Ar) • Major volatiles (CO2) Powerful tools to better understand the evolution of the Earth’s interior, its chemical structure, its volatile fluxes
Introduction Questions • What are the isotopic and elemental distributions of the noble gases (He, Ne, Ar) in the Earth? • What do the noble gases tell us about the present geodynamic structure of the Earth? Is the mantle layered? Is there a primordial component left in the mantle? • What do the noble gases tell us about the history of the Earth system? Where did the atmosphere come from? When did the atmosphere form? When did the Earth form/differentiate?
Introduction Helium • two stable isotopes: 3He and 4He Isotopes Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers. Noble gases “inert” (chemically non-reactive)
Introduction Helium • two stable isotopes: 3He and 4He • 3He is “primordial” 4He produced by radioactive decay of U and Th • Measure 3He/4He ratio on a mass spectrometer Noble gases “inert” (chemically non- reactive)
Introduction 3He is primordial 4He produced by radioactive decay of U and Th • Ocean islands basalts (OIB) • (e.g. Hawaii, Iceland, Réunion) • Less degassed (primitive) source • Higher 3He content • Higher 3He/4He • Deep source? Plume? • Mid-ocean ridge basalts (MORB) • Degassed (depleted) source • Low 3He content • Low 3He/4He • Shallow source
Introduction • Which (if any) of these views of the mantle are correct? Tackley, Science (2000)
Noble gas geochemistry of mantle-derived rocks and fluids on land Sampling hot springs and wells Sampling fumaroles Sampling pillow basalts Mini-DOAS: SO2 flux Mineral separates
Noble gas geochemistry of submarine oceanic basalts Dredging (R/V Revelle) Pillow basalt fragment with glassy rim
Noble gas geochemistry of cold seep fluids ROV Ventana (Monterey Bay, CA) Sampling of submarine cold seep fluids with Chemical and Aqueous Transport (CAT) meter DSV Alvin (Costa Rica)
Monterey Bay (CA) Fluids associated with the San Andreas and companion faults have high 3He/4He ratios Fluids enter the fault system from the mantle Monterey Bay Tryon et al., Oceanographic Research Papers, 2001 Kennedy et al., 1997
Costa Rica Complete a volatile mass balance for the Costa Rican Arc http://www.sfb574.uni-kiel.de/php/goto/Home/
KNOX11RR, R/V Revelle (NOV 07) Goals: - Determine the flow pattern of Réunion hotspot material towards the CIR - Test the hypotheses of Murton et al. (2005) and Nauret et al. (2006) Nauret et al., EPSL, 2006 Murton et al., G3, 2005
KNOX11RR, R/V Revelle (NOV 07) Murton et al., G3, 2005
KNOX11RR, R/V Revelle (NOV 07) Seafloor mapping: Multibeam surveying Instrumentation Viewpoint, Sarti News Bulletin
KNOX11RR, R/V Revelle (NOV 07) Magnetic surveying https://frontpage.northseattle.edu/jmasura/NaturalDisasters/Science121/SCI03.ppt Magnetometer
KNOX11RR, R/V Revelle (NOV 07) Dredging
Iceland Interaction between the Mid-Atlantic Ridge and the Icelandic Hotspot Bubbling mud pot Ito, Nature (2001) Subglacially erupted pillow basalts
