New Early Neoproterozoic Paleomagnetic Constraints of the Northwestern China Blocks on the Periphery of Rodinia.

Recent studies highlight the debates about the role of the northwestern China blocks, for example, north Tarim block, south Tarim block (STB), Altyn Tagh block (ATB) and Qaidam‐Qilian block (QQB) during the assembly of Rodinia. We herein present a combined paleomagnetic, geochronological, and geochemical study on 16 mafic dikes in the northern ATB. After removing a recent viscous remanent magnetization, three characteristic remanent magnetization components (CHs) were isolated. CH1 was identified in eight NW‐trending diabase dikes, one of which was newly dated at 895.3 ± 7.7 Ma through use of SHRIMP baddeleyite U‐Pb methodology. It yields a mean direction (D/I) of 123.3°/−42.2° (α95 = 12.1°). The paleopole (40.9°S/184.6°E, A95 = 11.7°) was calculated by averaging eight virtual geomagnetic poles (VGPs) from each dike. A partial baked‐contact test supports the primary origin of CH1. CH2 was isolated from three E‐W trending diabase dikes, pointing northwest with considerably shallower downward inclinations. CH3 was obtained from five lamprophyre dikes, directing southeast with moderate to shallow upward inclinations. However, the VGPs of either CH2 or CH3 are insufficient to average a precise mean pole. Geochemical analyses also reveal petrogenetic discrepancy among the dikes with distinct CHs. Combining the new ∼895 Ma pole of CH1 with the global paleomagnetic database and being aided by geological evidence, we propose that the STB‐ATB‐QQB and the north China craton were located along the northwestern side of Laurentia in Rodinia at ∼895 Ma, and suggest the connection might have been intact until ∼780 Ma. Plain Language Summary: The paleogeographic positions of the northwestern China blocks, including the north Tarim block, the south Tarim block, the Altyn Tagh block (ATB) and the Qaidam‐Qilian block in the Rodinia supercontinent, remain enigmatic and highly controversial. Here we present new paleomagnetic geochronological and geochemical data from three groups of the mafic dikes in the northern ATB. Our new results, in combination with other coeval paleomagnetic poles and geological evidence, support a specific proximity among the south Tarim, Altyn Tagh, Qaidam‐Qilian blocks and the north China craton along the northwestern side of Laurentia between ∼895 and ∼780 Ma. Key Points: A new paleomagnetic pole was obtained from eight early Neoproterozoic mafic dikes in the northern Altyn Tagh blockThe pole was dated at 895.3 ± 7.7 Ma using baddeleyite U‐Pb SHRIMP methodologyThe adjacent south Tarim‐Altyn Tagh‐Qaidam‐Qilian block and north China craton were located at NW side of Laurentia on the periphery of Rodinia [ABSTRACT FROM AUTHOR]