Other
Scientific paper
Oct 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011epsc.conf.1200p&link_type=abstract
EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France. http://meetings.copernicus.org/epsc-dps2011, p.1200
Other
Scientific paper
Identification of the superheated and lightweight material streams in the Earth interiors named as plumes, has put up the problem of the energy source for such overheating. Plume origin at core-mantle boundary suggests that such source is the core, which, apparently, is overheated in comparison with bottom of the low mantle. Magmatic derivatives of the mantle material sometimes contain primary noble gases and in particular the isotope 129J (the decay product of the short-lived 129J). It demonstrates that somewhere in the Earth there is a material which became geochemically closed with regard to noble gases before 129J complete decay, i.e. not later than through 150 million years after the beginning of accretion and which subsequently was never mixed with the mantle material. Properly speaking, such material is the material of the core, to be exact of its solid internal part. At the same time Hf-W and U-Pb isotope systems show that the formation of a liquid core has taken place during first 100-120 million years after accretion [2]. Along with it there are evidences of existence of an ancient geomagnetic field [3, 6, etc.] up to the early Archean [11], which intensity is identical to the modern one. This information contradicts the generally accepted ideas according to which the geodynamo, generating the modern magnetic field of the Earth, is produced by the compositional convection caused due to crystallization of a liquid core [1, 8, 10]. The most probable time of excitation of compositional convection is estimated about 1 Ga, but not earlier than 2 Ga [7, 10]. It follows that before this time the geomagnetic intensity should have had the lower value because it was generated only by inefficient thermal convection. Thus, if the compositional convection is required to generate the Archean geomagnetic field, intensity of which is close to the modern one, this convection should have any other nature.
Pushkarev Yu. D.
Starchenko Sergey V.
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