Comparisons of the Paleo-Mesoproterozoic large igneous provinces and black shales in the North China and North Australian cratons.

ABSTRACT

Comparisons of large igneous provinces (LIPs) and black shales from different cratons can provide important constraints on Precambrian paleogeographic reconstructions and a better understanding of the environmental effects of large-scale volcanic events. A comparison of intraplate mafic events mostly interpreted as LIPs or portions of LIPs (LIP fragments/remnants due to continental breakup or erosion) from the North China Craton (NCC) and North Australian Craton (NAC) shows good correlation in the age range from 1800 Ma to 1300 Ma, and four robust age matches at ca. 1790-1770 Ma, ca. 1730 Ma, ca. 1680-1670 Ma and ca. 1320 Ma have been identified. Most notably, the coeval ca. 1320 Ma Yanliao LIP in the eastern-northern NCC and the Derim Derim-Galiwinku LIP in the NAC are also characterized by similar field occurences and dominantly subalkaline tholeiitic basalts and intraplate geochemical compositions, and are interpreted as portions of the same LIP, separated by continental breakup. Subsequent to 1300 Ma, the NCC and NAC exhibit very different magmatic histories, indicating that separation of these two cratons occurred, likely subsequent to the ca. 1320 Ma LIP event. A comparison of Paleo-Mesoproterozoic black shales from the NCC and NAC provides further evidence for close connections between these regions during this period. Black shales of the Chuanlianggou Formation in the northern NCC and the Cuizhuang Formation in the southern NCC were deposited in the age range ca. 1650-1635 Ma and can be correlated with ca. 1640-1635 Ma black shales in the Barney Creek Formation of the NAC. Deposition of black shales within the Xiamaling Formation in the NCC and the Velkerri and Kyalla formations of the McArthur Basin in the NAC occurred synchronously at ca. 1380-1360 Ma. Our results from matching of LIP ages and black shales combined with paleomagnetic data show that the northern-northeastern margin of the NCC was connected to the northern margin of the NAC from ca. 1800 Ma to 1300 Ma. This long-lived late Paleoproterozoic to mid-Mesoproterozoic connection lasted for at least 500 million years until separation of the NCC from the NAC between ca. 1320 and ca. 1230-1220 Ma.