کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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4723042 | 1639630 | 2014 | 13 صفحه PDF | دانلود رایگان |
Paleomagnetic results are presented for two Paleoproterozoic mafic dykes in the Taivalkoski area in northern Karelia Province of the Fennoscandian shield where, based on K-Ar data, the crust has seen minimal effects of the otherwise pervasive 1.8–1.9 Ga Svecofennian orogeny. Within this study a new U–Pb baddeleyite age of 2339 ± 18 Ma has been determined for one of the E–W trending dykes (dyke AD13).The paleomagnetic results show that a strong Svecofennian overprinting is pervasive in the area. Upon thermal or AF demagnetization four remanence directions were obtained. Most typical are the secondary Svecofennian remanence direction A (intermediate down to the NNW) and remanence direction B (intermediate down to the NNE). Component D (D = 115.4°, I = 50.5°, α95 = 2.6°) yielding a virtual geomagnetic pole (VGP) D (Plat = −19.5°N, Plon = 263.3°, A95 = 3.1°) is obtained from baked rocks for dyke WD, and based on a positive baked contact test is interpreted to represent the primary magnetization dating from about 2.4 Ga. Dyke AD13 carries only secondary A and B components, its unbaked host migmatites carry reversed A (AR) component, and the baked host rock carries a component D′ (D = 134.5°, I = −7.3°, α95 = 8.8°), which yields a VGP pole D′ (Plat = −20.4°N, Plon = 257.3°, A95 = 7.6°), possibly representing magnetization at 2.3 Ga.The new paleomagnetic data from the Karelia Province compared to similar-aged paleomagnetic data from the Superior Province does not support the recently proposed Superia configuration, based upon dyke swarm trajectories.
Journal: Precambrian Research - Volume 244, May 2014, Pages 87–99