1.86 Ga key paleomagnetic pole from the Murmansk craton intrusions - Eastern Murman Sill Province

• Published in: Precambrian Research
• Main Authors: Samsonov, Alexander V., Stepanova, Alexandra V., Salnikova, Ekaterina B., Larionova, Yulia O., Travin, Alexey V., Arzamastsev, Andrey A., Egorova, Svetlana V., Erofeeva, Kseniya G., Stifeeva, Maria V., Veselovskiy, Roman V., Shcherbakova, Valentina V., Shcherbakov, Valeriy P., Zhidkov, Grigoriy V., Zakharov, Vladimir S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Фенноскандинавский щит; ключевой палеомагнитный полюс; геохронология; геохимия; палеонапряженность; Barents Sea; Kola Peninsula; Murmansk; Fennoscandia; kola peninsula
• Online Access: https://doi.org/10.1016/j.precamres.2019.01.017; http://vital.lib.tsu.ru/vital/access/manager/Repository/vtls:000707449

We present the first 1.86 Ga paleomagnetic key pole of Fennoscandia obtained for the dolerite sills of the Murmansk craton – Eastern Murman Sill Province that outcrop in the northern part of the Kola Peninsula along the Barents Sea coast for a distance of 200 km (Slat = 68.5° Slong = 37.9° N = 16 sites Plat = 54.7° Plong = 234.7° dp/dm = 4.3°/6.3° Qv = 5). The age of the sills and their characteristic remanent magnetization (ChRM) was determined by four independent geochronometers: U-Pb – 1860 ± 4 and 1863 ± 7 Ma (ID-TIMS baddeleyite) Sm-Nd – 1889 ± 57 Ma Rb-Sr – 1850 Ma Ar/Ar – 1865 ± 8 and 1857 ± 20 Ma (biotite). The primary nature of the ChRM is confirmed by the results of petrographic geochemical paleo- and rock magnetic studies as well as by thermochronological data. The similarity of the petrographic and geochemical characteristics of sills from different localities indicates that these dolerite sills were formed during a single magmatic event and their cooling down to 580 °C occurred at depths of about 10 ± 2 km and lasted ∼2800 years or even faster. Paleogeographic reconstruction of Fennoscandia on the basis of the obtained paleomagnetic pole is in general agreement with the previously suggested configuration of core of the Nuna/Columbia supercontinent (Evans and Mitchell 2011 Meert and Santosh 2017). A new reliable Thellier-Coe paleointensity determination for this time reveals a rather low mean VDM = 1.8 (±0.1) × 1022 Am2 that supports the Proterozoic dipole low hypothesis (Biggin et al. 2009).