FROM RODINIA TO GONDWANALAND: A TALE OF DETRITAL ZIRCON PROVENANCE ANALYSES FROM THE SOUTHERN NANHUA BASIN, SOUTH CHINA

The paleogeographic positions of the South China Block (SCB) during the Neoproterozoic and early Paleozoic are important for understanding the transition from the break-up of the supercontinent Roclinia to the formation of Gondwanaland. Integrated in situ U-Pb ages and Hf-O isotope analyses of detrital zircons from Cambrian sedimentary rocks in the southwestern SCB reveal major age populations at 2500 Ma, 1100 to 900 Ma, 850 to 750 Ma and 650 to 500 Ma, with a predominant group at similar to 980 Ma that counts for similar to 50 percent of all analyses. Zircon Hf-O isotopic results suggest three Precambrian episodes of juvenile crustal growth for the source area(s) (3.0 Ga, 2.5 Ga and 1.0 Ga), with major crustal reworking at 580 to 500 Ma. The source provenance as defined by the U-Pb and Hf analyses is distinctly different from the known tectonomagmatic record of the SCB, or that of western Australia or western Laurentia, but matches well with that of the Ediacaran (latest Neoproterozoic) Cambrian clastic sedimentary rocks and granitic intrusions in the NW Indian Himalaya. The SCB NW India provenance linkage appears to have started from the Ediacaran. We propose that after breaking away from central Rodinia, the SCB collided with NW India during the Ediacaran Ordovician time, causing the "Pan-African" Kurgiakh/ Bhimphedian orogeny at the northern margin of India as well as the intraplate Wuyi-Yunkai orogeny (>460 Ma - 415 Ma) in South China. The Ediacaran lower Paleozoic clastic sedimentary rocks in the Nanhua Basin are therefore interpreted to be foreland deposits formed during the collision of the SCB with Gondwanaland.