Position Of South China Research Articles

Yangtze and Cathaysia blocks of South China: Their separate positions in Gondwana until early Paleozoic juxtaposition

The position of South China in Gondwana remains controversial. In all previous models, the Yangtze and Cathaysia blocks, the two major components of South China, were amalgamated by the Tonian, and South China was considered to be a single coherent block in Gondwana. Based on a summary and critical reevaluation of available paleomagnetic, paleontological, stratigraphic, and detrital zircon data, we propose that the Yangtze and Cathaysia blocks were not juxtaposed until the early Paleozoic and were located at two separate parts of the northern margin of Gondwana before that time. The Yangtze block was located to the northwest of India in the Ediacaran and early Cambrian. Cathaysia was close to or a part of northern Australia in the Ediacaran, when Australia and India were separated by the Kuunga Ocean, and amalgamated with the eastern margin of India in the late Ediacaran to early Cambrian when the ocean closed. Our model implies that the early Paleozoic orogenesis in South China could have been related to two distinct events, the late Ediacaran to early Cambrian collision of Cathaysia/Australia with India (the Kuunga orogeny) and the Late Ordovician amalgamation of Cathaysia with Yangtze. It also implies that the Yangtze and Cathaysia blocks likely occupied two separate positions in Rodinia.

Position of South China and Indochina along northern Gondwana margin during the Ediacaran–Silurian period

The South China Block (SCB) has often been taken as an integral member of Gondwana at its northern margin, but it remains contentious regarding when and how it joined Gondwana, its precise position in Gondwana, and what other continent(s) might have been adjacent to it at the time. This study reports new detrital zircon U-Pb and Hf isotopic data of twelve Ediacaran-Silurian siliciclastic samples from three field regions along the western margin of the SCB. They show two prevailing age populations of 810–790 Ma and 550–520 Ma, and minor ca. 2500 Ma, ca. 1850 Ma, ca. 1200 Ma and ca. 980 Ma peaks in various units. In combination with the regional lithofacies evolution, provenance analysis demonstrates that the uplifted western SCB provided a persistent supply of 810–790 Ma zircons from local Tonian granites to the Ediacaran-Silurian sediments, whereas the 550–520 Ma zircons were probably derived exotically from a magmatic arc. Provenance analysis also reveals that the SCB and Indochina have a close provenance linkage. We interpret that the exotic magmatic arc was along the northern Indian margin with the subducting lower plate carrying SCB-Indochina to eventually collide with Indian Gondwana during Cambro-Ordovician time. The uplift of the western SCB during the time likely reflects the far-field tectonic compression of the collision.

South China in Rodinia: Constrains from the Neoproterozoic Suixian volcano-sedimentary group of the South Qinling Belt

The South Qinling Belt, incorporating the northern margin of the Yangtze Block, South China Craton, records a series of Neoproterozoic to Triassic cycles of ocean opening and closing. The Neoproterozoic Suixian Group provides a record of breakup of the Rodinia supercontinent. New zircon U-Pb ages, Hf isotopes and whole-rock elemental data from the group constrain the broader tectonic evolution of the South Qinling Belt and the position of South China within Rodinia. The Suixian Group comprises sandstone and siltstone associated with minor interlayered volcanic rocks. Detrital zircons show three U-Pb age peaks at ∼2450 Ma, ∼1990 Ma and ∼750 Ma, with a minimum age of ∼700 Ma. Their εHf(t) values range from –22.5 to +11.1. Zircon U-Pb and Hf isotopic data are similar to the age range and Hf isotopic character of magmatic zircons from the Precambrian igneous rocks in the South Qinling Belt, which in combination with the euhedral to subhedral apperance of the detrital zircons, suggests local derivation from rock units within the belt. The sedimentary rocks from the Suixian Group have high La/Sc (0.91–7.28), Th/Sc (0.56–2.16) and low Cr/Th ratios (0.94–5.28), implying derivation from felsic volcanic rocks. Their elemental contents and ratios are similar to those accumulating in a continental arc environment. Similarly, the detrital zircons from the late Neoproterozoic sedimentary rocks along the margins of the Yangtze Block show a dominant U-Pb age peak of 770 Ma to 710 Ma, suggesting significant input from an approximately syn-depositional magmatic source. The Neoproterozoic detrital zircons show similar age distributions and εHf(t) values to those of the Neoproterozoic igneous rocks around of the Yangtze Block, suggesting that these sedimentary rocks were sourced from a magmatic arc. The Yangtze Block and northern India preserve similar Neoproterozoic sedimentary successions and detrital age populations indicating that they were closely connected and located along either the margin of Rodinia or on a plate isolated from Rodinia.

An Andean-type arc system in Rodinia constrained by the Neoproterozoic Shimian ophiolite in South China

The configuration of the supercontinent Rodinia has long been a matter of debate; the key controversy is the position of South China in Rodinia. We report an incomplete Neoproterozoic ophiolite sequence, including gabbros and serpentinized peridotites intruded by mafic dikes, near Shimian (Sichuan Province), along the western margin of the Yangtze Block in South China. Serpentinized peridotites have very low REE (0.14–1.16ppm) and trace element concentrations, and are interpreted as parts of a depleted mantle sequence. Chromites from the serpentinized peridotites have low TiO2 (<0.3wt%) and Fe2O3 (<7.6wt%), and moderate Cr/(Cr+Al) (0.48–0.67) and Mg/(Mg+Fe2+) (0.42–0.67) ratios and are clearly indicative of strong depletion of the host peridotites, similar to those of supra-subduction zone (SSZ). Mafic dikes and gabbros contain zircon grains with similar U-Pb ages of ∼800Ma, and are chemically akin to MORB-like tholeiitic basalts and boninite-series volcanic rocks reported in other SSZ ophiolites and in the Izu-Bonin-Mariana arc system. Therefore, the serpentinized peridotite, mafic dikes and gabbros together appear to form a SSZ-type ophiolite assemblage preserving the accretion of oceanic lithosphere to the western Yangtze Block. The age and location of the Shimian ophiolite rule out the possibility that South China was located in the centre of Rodinia. Instead, the Neoproterozoic arc-affinity igneous rocks at the western margin of the Yangtze Block are well correlated with those in Greater India and Madagascar. These three blocks thus together formed a giant Andean-type arc system along the NW margin of Rodinia that existed for more than 100Mys.

Precambrian crustal evolution of the South China Block and its relation to supercontinent history: Constraints from U–Pb ages, Lu–Hf isotopes and REE geochemistry of zircons from sandstones and granodiorite

The unified South China Block, comprising the Yangtze Block to the northwest and the Cathaysia Block to the southeast, has been central to recent studies on the Precambrian crustal evolution and position of South China in Proterozoic supercontinents. Here we present results from detailed U–Pb geochronology, Lu–Hf isotopes and rare earth geochemistry on zircons from three Ordovician and Devonian sandstone samples of southeastern Yangtze, together with those from a granodiorite sample and three Triassic sandstone samples in northeast and southeast Cathaysia. The southeastern Yangtze Block is characterized by extensive tectono-thermal events during 850–730Ma and 470–410Ma, which corresponded to the breakup of Rodinia and the Caledonian orogenic event, respectively. Major zircon populations with ages of 2800–2500Ma, 1990–1580Ma and 1260–920Ma are recorded from southeastern Yangtze, which are correlated, respectively, with the Neoarchean crustal growth, and histories of the Paleo-Mesoproterozoic Columbia and Neoproterozoic Rodinia supercontinents. In contrast, zircon U–Pb ages from southeast Cathaysia reveal prominent magmatic events during 2630–2300Ma, 2030–1770Ma and 280–190Ma, correlated with Neoarchean continental growth and the tectonothermal regimes associated with the history of the Columbia supercontinent as well as the Indosinian movement. The sector-zoned zircons from the granodiorite in northeast Cathaysia yielded weighted mean ages of 846.7±9.8Ma and 826.4±7.6Ma and positive ɛHf values, constraining the initial breakup of South China at ca. 848 Ma and extensive rift-related magmatism at ca. 826Ma. The Hf data suggest important episodes of juvenile magmatic addition at 3.1–2.8Ga and 2.4–1.5Ga for Yangtze, and at 3.3–2.3Ga for Cathaysia, indicating the existence of older crustal components in South China. The Hf data suggest that most zircons in both the blocks were derived from crustal magmas. Our results suggest distinct crustal evolution histories for the Yangtze and Cathaysia Blocks albeit with close affinities.

Position of South China in configuration of Neoproterozoic supercontinent

Configuration and evolution of Neoproterozoic su- percontinent and the position of South China within it have been very important targets in earth sciences concerning many forefront topics of general interest. In the common reconstruction of the supercontinent Rodinia, South China was located between Australia and Laurentia, and thus lies in the center of the supercontinent and southeast of Aus- tralia

Position of South China in configuration of Neoprotero-zoic supercontinent

Position of South China in configuration of Neoprotero-zoic supercontinent