Abstract
Abstract In the Rodinia supercontinent, Laurentia is placed at the center because it was flanked by late Neoproterozoic rifted margins; however, the conjugate margin for western Laurentia is still enigmatic. In this study, new paleomagnetic results have been obtained from 15 ca. 775 Ma mafic dikes in eastern Hebei Province, North China craton (NCC). Stepwise thermal demagnetization revealed a high-temperature component, directed northeast or southwest with shallow inclinations, with unblocking temperatures of as high as 580 °C. Rock magnetism suggests the component is carried by single-domain and pseudo-single-domain magnetite grains. Its primary origin is supported by a positive reversal test and regional remanence direction correlation test, and the paleomagnetic pole (29.0°S, 64.7°E, A95 = 5.4°) is not similar to any published younger poles of the NCC. Matching the late Mesoproterozoic to early Neoproterozoic (ca. 1110–775 Ma) apparent polar wander paths of the NCC and Laurentia suggests that the NCC could have been the conjugate margin for northwestern Laurentia in Rodinia, rather than sitting off the northeast coast of the main Rodinian landmass. Geological data indicate that breakup of the NCC and Laurentia occurred between ca. 775 and 720 Ma.
Highlights
Laurentia is placed at the center of the Rodinia supercontinent because it is flanked by Neoproterozoic passive margins (Hoffman, 1991; Li et al, 2008, and references therein)
In earlier published papers for Rodinia reconstructions (Dalziel, 1991; Hoffman, 1991; Moores, 1991), Australia-Antarctica was linked to the western margin of Laurentia, named the “SWEAT” model, but subsequent paleomagnetic data excluded a tight configuration of Australia against the western Laurentia margin
Ca. 780 Ma mafic dikes or plutons were reported from the Yili block, which is 300 km to the north of Tarim and was possibly associated with Tarim during the Neoproterozoic (Wang et al, 2014). These results suggest the North China craton (NCC), Tarim, and Yili block together could have formed the conjugate margin for western Laurentia
Summary
Laurentia is placed at the center of the Rodinia supercontinent because it is flanked by Neoproterozoic passive margins (Hoffman, 1991; Li et al, 2008, and references therein). Owing to a series of high-quality late Mesoproterozoic to early Neoproterozoic paleomagnetic and geochronological data reported from the North China craton (NCC), a ca. Two generations of unmetamorphosed Precambrian mafic dikes exist in the Lulong region, eastern Hebei Province, the northeastern NCC (Fig. 1).
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