South Tarim tied to north India on the periphery of Rodinia and Gondwana and implications for the evolution of two supercontinents

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.

Thermal Structure Beneath the Tarim Craton and Its Tectonic Implications

The lateral distribution of the magnetic layer beneath the Tarim Craton and its environs was estimated from spectral analysis using the newest high-resolution aeromagnetic dataset of mainland China, which is enlarged by EMAG2. As a proxy, the Curie point depth (CPD) provides a comprehensive view of a crust-scale thermal regime, accounted for the depth at which magnetite becomes paramagnetic, and the correspondence of the CPD with the tectonic regime indicates that the CPD is useful for delineating the regional crustal thermal structure. Furthermore, lateral variations in CPD provide useful insights into the lithospheric thermal state of the Tarim Craton and its surrounding areas and can be related to ancient and active tectonics, such as geothermal activity, seismicity, and mineral-petroleum generation. In the Tarim interior, the NW domain covering the Bachu Uplift and its surrounding areas corresponds to the minimum magnetic CPD signature geometry of this area, which is most likely linked to the Permian Tarim plume-lithosphere interaction. In contrast, the other domains are characterized by large CPD values (up to 50 km), which are floored by a Precambrian basement without the Permian magmatism modification. Moreover, the estimated CPD values are consistent with surface heat flow measurements with an inverse correlation, which can assist in identifying the potential area for mineral deposits and hydrocarbon fields. Earthquakes are mostly concentrated in the gradient and transition zones of the Curie surface, suggesting that these abrupt variation domains in the crustal thermal structure act as a secondary mechanism for earthquake generation.

Early Neoproterozoic (870–820 Ma) amalgamation of the Tarim craton (northwestern China) and the final assembly of Rodinia

In the paleogeographic configuration of the Neoproterozoic supercontinent of Rodinia, the Tarim craton (northwestern China), traditionally seen as a single block, is placed either on the periphery near northern Australia or India or in a central position between Australia and Laurentia. To distinguish between these possibilities, we present here new primary paleomagnetic results from ca. 900 Ma volcanics in the Aksu region of the northwestern Tarim craton. The data reveal a ~28° latitudinal difference between the North Tarim and South Tarim blocks at ca. 900 Ma and constrain the age of amalgamation of the Tarim craton to between 870 and 820 Ma. Combining paleomagnetic poles from Tarim and major cratons of Rodinia with geological evidence, a two-stage orogenic model is proposed for the assembly of Rodinia. Late Mesoproterozoic orogenesis (1.3–1.0 Ga) led to the assembly of Australia–East Antarctica, Baltica, Umkondia, South Tarim, and Cathaysia with Laurentia, forming the core of Rodinia. Thereafter, the Jiangnan–Central Tarim Ocean separating North Tarim and Yangtze from South Tarim and Cathaysia was closed before ca. 820 Ma. This second Jiangnan–Central Tarim orogeny caused nearly coeval amalgamation of the peripheral Tarim and South China cratons by the welding of North Tarim and Yangtze to South Tarim and Cathaysia, respectively. The supercontinent of Rodinia was thus assembled by two orogenic phases separated by ~200 m.y.

Supplemental Material: Early Neoproterozoic (870–820 Ma) amalgamation of the Tarim craton (northwestern China) and the final assembly of Rodinia

Supplemental text, Figures S1 and S2, and Tables S1–S3.<br>

Supplemental Material: Early Neoproterozoic (870–820 Ma) amalgamation of the Tarim craton (northwestern China) and the final assembly of Rodinia

Supplemental text, Figures S1 and S2, and Tables S1–S3.<br>