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  • mantle
  • and 70±10 Kcal/mole, log Do = +2.1±1.2, respectively), but are still too low to transport or homogenize helium in the mantle or even in magma chambers. (mblwhoilibrary.org)
  • However, diffusion equilibrates melts and mantle minerals within decades, and interaction with wall-rocks may be enhanced for helium in comparison to other isotopic tracers because of its greater mobility. (mblwhoilibrary.org)
  • Upper-mantle dynamics revealed by helium isotope variations along the southeast Indian ridge. (ucsb.edu)
  • A global, coarse-resolution ocean model previously fitted to geostrophic shear estimates and to data of 10 hydrographic parameters and tracers has been used to simulate the 3 He and 4 He distributions resulting from the release of mantle helium from mid-ocean ridges. (royalsocietypublishing.org)
  • Parts of these magma oceans may have crystallized and sunk to the boundary between the mantle and the core, preserving the ancient tungsten and helium signatures. (phys.org)
  • within the isotopic variations or N lid-Ocean Ridge Basalt, thus, we could not detect helium of lower mantle origin. (nii.ac.jp)
  • Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents1. (phys.org)
  • crustal
  • Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. (phys.org)
  • It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. (phys.org)
  • timescales
  • The corresponding timescales for 50% helium loss or exchange with seawater (1 cm spheres) are about one million years for mid-ocean-ridge- basalts, and about 100,000 years in seamount alkali basalts. (mblwhoilibrary.org)
  • Equations for simultaneous helium production and diffusive loss allow model ages for surface exposure to be corrected for helium loss, and demonstrate that cosmogenic 3He geochronology will not be limited by helium loss for timescales of approximately 1 million years in quartz and 10 million years or more in olivine. (mblwhoilibrary.org)
  • Carbon
  • Publications] Xu, Nakai et al: 'Carbon isotopes of hydrocarbons and carbondioxide in natural gases in China' Jour.Southeast Asian Earth Sci.15. (nii.ac.jp)
  • volcanic rocks
  • Mundl, Walker and their co-authors suggest a few different scenarios that could have produced the tungsten and helium anomalies they observed in volcanic rocks from Hawaii and Samoa. (phys.org)
  • variations
  • Variations in the isotopic composition of helium have been long known, but have never been correlated with other geochemical parameters," said Richard Walker, professor and department chair of geology at UMD and a co-author of the paper. (phys.org)
  • basalt
  • factor of 5 uncertainty) and that U+Th/4He geochronology of fresh seafloor basalt glasses is unlikely to be hampered by helium loss. (mblwhoilibrary.org)
  • atomic
  • Helium is the chemical element with atomic number 2 and an atomic weight of 4.0026, which is represented by the symbol He . (statemaster.com)
  • Isotopes of elements having atomic numbers greater than 80 are capable of undergoing fission. (virginia.edu)
  • source
  • This helium source may have been isolated at the core- higher in Ni than olivines that are expected to crystallize from anymantle boundary region since Earth's accretion4-6. (slideshare.net)
  • Depending on the source type, isotopes of just about any element can be analysed, and the different sources allow a wide variety of types of materials to be sampled: solids, liquids, gasses, solutes in liquids, etc. (blogspot.com)
  • chemical
  • In reality, there is generally more than one possible process, but the nice thing about isotopes is that because they have similar chemical behavior, we can generally rule out a lot of processes that rely on chemical differences in the ancient earth, so that the isotopic signal suggest only a few (or if we are lucky, one) process was at work in the past. (blogspot.com)
  • An additional benefit of isotopes is that because they have similar chemical behaviors, their chemistry doesn't separate them in our measurement device. (blogspot.com)
  • higher
  • In surveying the gasses that emanate from various parts of the famous park, the researchers discovered far higher amounts of the helium -4 isotope than was expected-approximately 60 tons every year. (phys.org)
  • samples
  • Measuring Helium Isotopes and Tritium in Seawater Samples by Jenkins et al. (columbia.edu)
  • 1998. Advances in analysis and shipboard processing of tritium and helium samples. (columbia.edu)
  • Helium-3 is extremely rare on Earth, and tends to show up in samples of rock that have not been melted or otherwise recycled since the planet first formed. (phys.org)
  • Eventually
  • That didn't happen until the area became volcanic-hot magma beneath the trapped helium pushed it upwards, eventually squeezing it through cracks, steam vents and geysers at the surface. (phys.org)