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Electrical anisotropy may be indicative of the successive lateral accretion of oceanic crust beneath the continental shelf followed by shortening.
The enhanced mantle conductivity mechanism is unknown, although it may be associated with metasomatic modification of the subcontinental lithosphere subsequent to collisional thickening and followed by delamination or convective removal of some lithosphere.
This work was done in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the Department of Geology, University of Chicago.
Potassium-Argon Dating Potassium-Argon dating is the only viable technique for dating very old archaeological materials.
Argon is a gas that does not ordinarily combine with other elements.
So, when a mineral forms – whether from molten rock, or from substances dissolved in water – it will be initially argon-free, even if there is some argon in the liquid.
While the Indo-EurasianLaurentia tectonic analogy is incomplete, it is sufficiently compelling in explaining the electromagnetic and other data that it is a useful basis for understanding the Proterozoic assembly of Laurentia. Although carefully collected, accuracy cannot be guaranteed. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
That is, a fresh mineral grain has its K-Ar "clock" set at zero.If one of these protons is hit by a beta particle, it can be converted into a neutron.With 18 protons and 22 neutrons, the atom has become Argon-40 (Ar-40), an inert gas.Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.This work was supported in part by AEC contract number AT(11-1)-101 and in part by National Science Foundation grant number G-208.