Seminar

Constraining the positions of, and interrelationships between the Earth’s major continental blocks has played a major role in validating the concept of the supercontinent cycle. Minor continental fragments provide additional key constraints on modes of supercontinent assembly and dispersal. The Tarim Craton has been placed at both the core of Rodinia or on its periphery, and differentiating between the two has widespread implications for the breakup of Rodinia and subsequent assembly of Gondwana. In South Tarim, detrital zircon grains from Neoproterozoic-Silurian strata display two dominant populations at 950-750 and 550-450 Ma. Similarly, two main peaks at 1000-800 and 600-490 Ma characterize Neoproterozoic-Ordovician strata in North India. Moreover, the two dominant peaks of South Tarim and North India lag two global peaks at 1200-1000 and 650-500 Ma, which reflect Rodinia and Gondwana assembly, by about 200-100 million years, precluding a position within the heart of two supercontinents. Ages and Hf isotopes of Tarim’s detrital zircons argue for a position of the margin of both supercontinents adjacent to North India with periodic dispersal through opening and closing of small ocean basins (e.g., the Proto-Tethys). Alternating tectonic transitions between advancing and retreating subduction in North Tarim coincide with the drift timing of South Tarim from North India in Rodinia and Gondwana, respectively, emphasizing the importance of retreating subduction in supercontinent dispersal. Moreover, the Rodinia-related interior orogenic belts spatially overlap the Gondwana-related interior orogenic belts, indicating no significant relative rotation of India and Tarim during the evolution from Rodinia to Gondwana.

Additional information: Mr. Peng WANG, wangp@hku.hk