Paleomagnetism of the Neoproterozoic diamictites of the Tarim Block

The Neoproterozoic is characterized by the breakup of supercontinent Rodinia, the subsequent assembly of another supercontinent Gondwana, and the accompanying widespread glaciations over the fragmentary landmasses. Nearly continuous Neoproterozoic successions, including diamictites intervals that are attributed to major glaciations, are well exposed along the northern margin of the Tarim Block and provide an excellent archive for unraveling the tectonic history of the Tarim Block during this critical interval of the Earth's history. As high-precision U-Pb zircon dates are increasingly reported from the interbedded volcanics of the Neoproterozoic strata of the Tarim Block, it is now possible to quantitatively reconstruct the tectonic history of the Tarim Block by paleomagnetic investigations of the Neoproterozic strata with the improved chronologic constraints. We have conducted a detailed paleomagnetic study of the Neoproterozoic successions exposed in the Quruqtagh area of Xinjiang, China with particular focus on the diamictites intervals representing major glaciations in the Neoproterozoic. The studied strata include the Altungol, Tereeken, Zhamoketi, and Hankalchough Formations. All samples are subjected to stepwise thermal demagnetization to isolate the Characteristic Remanent Magnetizations (ChRM). Preliminary results show that rocks from the Altungol Fm and the lower and the middle part of the Hankalchogh Fm yield errantic directions upon demagnetization. Eight clasts from the Tereeken Fm, which is dominated by the Marinoan-age diamictites, yield ChRMs that constitute a positive conglomerate test, suggesting that these rocks likely retain the primary remanence and thus hold promise to reconstruct the tectonic history of the Tarim Block. Further analysis is being performed and paleogeographic reconstructions of the Tarim Block during the Neoproterozoic will be discussed.