NATURAL REMANENT MAGNETIZATIONS OF GRANITE AND SYENITE FROM PINGVINANE AND LUNCKERYGGEN IN THE SOR RONDANE MOUNTAINS, EAST ANTARCTICA

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The characteristics of the natural remanent magnetizations (NRMs) of granite and syenite from Pingvinane and Lunckeryggen in the western Sor Rondane Mountains were elucidated. In order to endorse the NRMs, AF and thermal demagnetization, thermomagnetic and magnetic hysteresis properties were analyzed. Furthermore, microscopic observations were carried out for identification of the magnetic grains.Consequently, reliable mean NRM directions acquired in early Silurian period were given from the Pingvinane granite as I=68.3°, D=315.3°, α_<95>=4.1° and the Lunckeryggen syenite as I=74.0°, D=327.3°, α_<95>=7.0°. Part of the syenite and granite from Lunckeryggen showed different NRM directions as I=79.8°, D=201.3°, α_<95>=9.3°, and as I=39.8°, D=178.9°, α_<95>=12.1°, respectively, although their meaning was not elucidated in this paper. The syenite and granite from Lunckeryggen include magnetite for NRM carriers with heterogeneous size distributions, which would cause a wide scattering of their NRMs. The virtual geomagnetic pole positions calculated from the established NRMs were at 37.4°S, 10.5°W, for the Pingvinane granite and 44.6°S, 1.0°E, for the Lunckeryggen syenite. These positions are consistent with the previous result reported by J.D.A. ZIJDERVELD (J. Geophys. Res., 73,3773,1968).
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