RECONSTRUCTION OF THE CRYOGENIAN PALEOGEOGRAPHY IN THE YANGTZE DOMAIN: CONSTRAINS FROM DETRITAL AGE PATTERNS

Detrital zircons are often used to constrain the maximum sedimentary age of strata and sedimentary provenance. This study aimed at reconstructing the Cryogenian Paleogeography of the Yangtze Domain (YGD) based on U-Pb ages and Lu-Hf isotopic signatures of detrital zircons from sandstones in the Southeastern part of the Yangtze Domain. U-Pb ages of the youngest detrital zircon grains from the Niuguping, Gucheng, and Datangpo formations yielded average ages of 712 ± 24 Ma, 679.2 ± 6.2 Ma and 665.1 ± 7.4 Ma, respectively, which are close to the depositional ages of their respective formations. The magmatic rocks in the SQB (South Qinling Block) were emplaced during ca. 941 Ma to 667 Ma. The magmatic rocks recorded four major Neoproterozoic magmatic events: (1) ca. 940 Ma, the formation of arc-related high Nb titanite-bearing diorites; (2) ca. 885 Ma, the formation of gabbroic to dioritic arc-related rocks; (3) 785-740 Ma, widespread magmatism with the emplacement of intermediate to felsic granitoids, showing typical arc-related characteristics; and (4) ca. 667 Ma gabbroic magmatism, formed in an extensional setting (Hu et al. 2016). Four Neoproterozoic magmatic stages were recognized in the uplift zone of the SQB, corresponding to four magmatic stages in the northern margin of the YZD (Hu et al. 2016. and references therein). An integrated study of detrital zircon Lu-Hf isotopes and U-Pb ages from three samples revealed six main peak ages in the samples from the Anhua section at ca. 680 Ma, ca. 780 Ma, ca. 820 Ma, ca. 940 Ma, ca. 2000 Ma, and ca. 2500 Ma. The characteristics of U-Pb age and Hf isotopes indicate a link between the north and southeast margins of Yangtze as early as ca. 680 Ma, and the provenance of the coeval sedimentary sequences in southeast Yangtze was from the South Qinling in the north margin of Yangtze. Furthermore, the ca. 2.0 Ga metamorphic zircon also indicates that the source of the study area is South Qinling. The provenance analysis on the ca. 680 Ma detritus of late Neoproterozoic strata in Yangtze revealed that the detritus were transported southward from South Qinling to the southeast margin of Yangtze through the Exi strait, but they were hindered by the Jiangnan Orogenic.