Noble gas and carbon studies of intraplate volcanoes, strike- slip, convergent and divergent plate boundaries Evelyn Füri, December 9 th 2008

Introduction Matterhorn Tschingelhörner – Glarus thrust Garnet peridotiteGneiss

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 (CO 2 )  Powerful tools to better understand the evolution of the Earth’s interior, its chemical structure, its volatile fluxes

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: 3 He and 4 He 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: 3 He and 4 He 3 He is “primordial” 4 He produced by radioactive decay of U and Th Measure 3 He/ 4 He ratio on a mass spectrometer Noble gases “inert” (chemically non- reactive)

3 He is primordial 4 He produced by radioactive decay of U and Th Mid-ocean ridge basalts (MORB) Degassed (depleted) source  Low 3 He content  Low 3 He/ 4 He Shallow source Ocean islands basalts (OIB) (e.g. Hawaii, Iceland, Réunion) Less degassed (primitive) source  Higher 3 He content  Higher 3 He/ 4 He Deep source? Plume? Introduction

Which (if any) of these views of the mantle are correct? Tackley, Science (2000) Introduction

Noble gas geochemistry of mantle-derived rocks and fluids on land Sampling fumaroles Sampling hot springs and wells Mineral separates Sampling pillow basalts Mini-DOAS: SO 2 flux

Noble gas geochemistry of submarine oceanic basalts Dredging (R/V Revelle) Pillow basalt fragment with glassy rim

Sampling of submarine cold seep fluids with Chemical and Aqueous Transport (CAT) meter ROV Ventana (Monterey Bay, CA) DSV Alvin (Costa Rica) Noble gas geochemistry of cold seep fluids

Monterey Bay (CA) Fluids associated with the San Andreas and companion faults have high 3 He/ 4 He ratios  Fluids enter the fault system from the mantle Kennedy et al., 1997 Monterey Bay Tryon et al., Oceanographic Research Papers, 2001

Costa Rica Complete a volatile mass balance for the Costa Rican Arc

Central Indian Ridge KNOX11RR, R/V Revelle (NOV 07)

KNOX11RR, R/V Revelle (NOV 07)

Murton et al., G 3, 2005 KNOX11RR, R/V Revelle (NOV 07) Nauret et al., EPSL, 2006 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)

Murton et al., G 3, 2005 KNOX11RR, R/V Revelle (NOV 07)

Seafloor mapping: Multibeam surveying Instrumentation Viewpoint, Sarti News Bulletin

KNOX11RR, R/V Revelle (NOV 07) Magnetic surveying Magnetometer aturalDisasters/Science121/SCI03.ppt

KNOX11RR, R/V Revelle (NOV 07) Dredging 

KNOX11RR, R/V Revelle (NOV 07) ~1mm

Results – Helium on-axis vs. off-axis

The End

Iceland Ito, Nature (2001) Interaction between the Mid-Atlantic Ridge and the Icelandic Hotspot Bubbling mud pot Subglacially erupted pillow basalts