ALBERT

Description: Constraining the positions of, and interrelationships between, Earth’s major continental blocks has played a major role in validating the concept of the supercontinent cycle. Minor continental fragments can provide additional key constraints on modes of supercontinent assembly and dispersal. The Tarim craton has been placed both at the core of Rodinia or on its periphery, and differentiating between the two scenarios has widespread implications for the breakup of Rodinia and subsequent assembly of Gondwana. In the South Tarim terrane, 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 northern 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, arguing against a position within the heart of the two supercontinents. Ages and Hf isotopes of Tarim’s detrital zircons argue for a position on 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 periodic drift of South Tarim from north India in Rodinia and Gondwana, emphasizing the importance of retreating subduction in supercontinent dispersal. Moreover, the Rodinia-related orogenic belts spatially overlap the Gondwana-related orogenic belts in the two blocks, indicating no significant relative rotation of India and Tarim during the evolution from Rodinia to Gondwana.