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Noble gas and carbon studies Noble gas and carbon studies of intraplate volcanoes, strike-of intraplate volcanoes, strike-slip, convergent and divergent slip, convergent and divergent
plate boundariesplate boundaries
Evelyn Füri, December 9th 2008
Introduction
Matterhorn
Tschingelhörner – Glarus thrust
Garnet peridotite Gneiss
Introduction
Geysir, Iceland
R/V AtlantisSIO
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
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
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.
Kr
Xe
Rn
Ne
Ar
He10
18
36
54
86
2
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
Kr
Xe
Rn
Ne
Ar
He10
18
36
54
86
2
Noble gases
“inert”
(chemically non- reactive)
3He is primordial4He produced by radioactive decay of U and Th
Mid-ocean ridge basalts (MORB)
• Degassed (depleted) source
Low 3He content
Low 3He/4He
• Shallow source
Ocean islands basalts (OIB)(e.g. Hawaii, Iceland, Réunion)
• Less degassed (primitive) source
Higher 3He content
Higher 3He/4He
• 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 fumarolesSampling hot springs and wells
Mineral separates
Sampling pillow basalts
Mini-DOAS: SO2 flux
Noble gas geochemistry of submarine oceanic basalts
Dredging (R/V Revelle) Pillow basalt fragment with glassy rim
Sampling of submarine cold seep fluids withChemical 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 3He/4He 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
http://www.sfb574.uni-kiel.de/php/goto/Home/
Central Indian Ridge
KNOX11RR, R/V Revelle (NOV 07)
KNOX11RR, R/V Revelle (NOV 07)
Murton et al., G3, 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., G3, 2005
KNOX11RR, R/V Revelle (NOV 07)
KNOX11RR, R/V Revelle (NOV 07)
Seafloor mapping:
Multibeam surveying
Instrumentation Viewpoint, Sarti News Bulletin
KNOX11RR, R/V Revelle (NOV 07)
Magnetic surveying
Magnetometerhttps://frontpage.northseattle.edu/jmasura/NaturalDisasters/Science121/SCI03.ppt
KNOX11RR, R/V Revelle (NOV 07)
Dredging
KNOX11RR, R/V Revelle (NOV 07)
~1mm
Results – Heliumon-axis vs. off-axis
The EndThe End
Iceland
Ito, Nature (2001)
Interaction between the Mid-Atlantic Ridge and the Icelandic Hotspot
Bubbling mud pot
Subglacially erupted pillow basalts