First mid-Neoproterozoic paleomagnetic results from the Tarim Basin (NW China) and their geodynamic implications
Résumé
In order to improve the understanding of the configuration and breakup history of the Rodinia supercontinent, a paleomagnetic study has been carried out on the 807 ± 12 Ma Aksu dyke swarm (ADS) in Aksu area, northwestern Tarim Block (NW China). The magnetic mineralogical investigations show that the magnetic remanence is principally carried by automorphous titanium-poor magnetite. The measured samples from nine dykes present stable magnetic directions with both normal and reversed magnetic polarities. Because of the monoclinal bedding of overlying sedimentary rocks, no fold test can be provided. However, a positive reversal test is obtained. The magnetic site-mean direction in geographic coordinates is close to, but significantly different from, the present earth field (PEF). A tilt-corrected paleomagnetic pole, therefore, is computed: 19°N, 128°E, DP = 6°, DM = 7° with N = 9. This new paleomagnetic observation reveals that the Tarim Block was located at an intermediate latitude of 43 ± 6°N. Integrating the geochronological studies of dyke swarms from Australia and the Aksu area and referring to the configuration of the Rodinia supercontinent proposed by Moores [Geology 19 (1991) 425] and Li and Powell [Earth Sci. Rev. 53 (2001) 237], the Tarim Block was placed north of Australia with the Aksu dykes being a possible northward continuation of lamprophyre dykes and kimberlite pipes in the northeast part of the Kimberley Craton, Western