Research Article| February 26, 2019 No collision between Eastern and Western Gondwana at their northern extent Wei Wang; Wei Wang * 1State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China.2School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria 3800, Australia *E-mail: wwz@cug.edu.cn Search for other works by this author on: GSW Google Scholar Peter A. Cawood; Peter A. Cawood 2School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria 3800, Australia Search for other works by this author on: GSW Google Scholar Manoj K. Pandit; Manoj K. Pandit 3Department of Geology, University of Rajasthan, Jaipur 302004, India Search for other works by this author on: GSW Google Scholar Jun-Hong Zhao; Jun-Hong Zhao 1State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China. Search for other works by this author on: GSW Google Scholar Jian-Ping Zheng Jian-Ping Zheng 1State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China. Search for other works by this author on: GSW Google Scholar Geology (2019) 47 (4): 308–312. https://doi.org/10.1130/G45745.1 Article history received: 24 Oct 2018 rev-recd: 14 Jan 2019 accepted: 15 Jan 2019 first online: 27 Feb 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Wei Wang, Peter A. Cawood, Manoj K. Pandit, Jun-Hong Zhao, Jian-Ping Zheng; No collision between Eastern and Western Gondwana at their northern extent. Geology 2019;; 47 (4): 308–312. doi: https://doi.org/10.1130/G45745.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Upper Neoproterozoic to lower Paleozoic sedimentary successions in northwestern India are thought to record collision between the continental fragments of Western and Eastern Gondwana, and contain detritus derived from the East African orogen. However, paleocurrent analysis together with U-Pb age distribution and Hf isotopic signatures of detrital zircons from these successions indicate derivation from proximal sources within Eastern Gondwana. Time-equivalent successions from the Qiangtang terrane (Tibetan Plateau) and the northern margin of Neoproterozoic India show a similar provenance record, along with additional input of late Mesoproterozoic and Neoproterozoic detritus from East Antarctica–East India and West Australia. Detritus from the rising East African orogen is abundant in deposits in northern Africa, which constitutes part of Western Gondwana, but absent from equivalent successions in Indian Eastern Gondwana. The consistency in sedimentary provenance of the late Neoproterozoic to early Paleozoic strata in northwestern India, combined with the lack of evidence for deformation or metamorphism since at least ca. 760 Ma, argues against collision between the eastern and western segments of Gondwana in this northern region. These regions remained as passive continental margins separated by a large-scale embayment of the proto-Tethys ocean until late Paleozoic fragmentation of the continental blocks. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Abstract Late Tonian to Cambrian sedimentary sequences in northwestern India and South China provide vital evidence for modeling their paleogeographic linkage, including their juxtaposition and subsequent separation during the transition from the Rodinia to the Gondwana supercontinents. Similarities in lithostratigraphy and detrital zircon U-Pb-Hf-O isotopic characteristics in the late Tonian sedimentary units from both regions underline a common provenance. A substantial decrease in zircon δ18O values from super- to sub-mantle compositions and simultaneous increase in the zircon εHf(t) values in South China and northwestern India for the 800–700 Ma time window suggest a common Neoproterozoic extensional magmatic event, corresponding with the Rodinia breakup. A distinct change in sedimentary provenance is noted during the Cryogenian period. Sedimentation along the northwestern margin of India for the remainder of the Neoproterozoic encompasses large volumes of clastic detritus dominated by old zircon ages, derived inboard from the Indian craton. In contrast, contemporaneous sedimentary units in the Yangtze region of South China are dominated by Neoproterozoic zircons. The detrital zircon age data underline a close paleogeographic linkage between northwestern India and South China (Yangtze and Cathaysia regions) in the Rodinia supercontinent configuration and argue for their separation through continental rifting during the Cryogenian. Northwestern India developed into a passive margin, whereas the South China block partially rifted, rotated, and migrated dextrally along the Gondwana margin toward northeastern India and Western Australia, such that the Cathaysia block continued to receive detritus from Gondwana continental regions.
The Marwar Supergroup (NW Peninsular India) is thought to be of Ediacaran-Cambrian age, based on previous paleontological and geochronological studies. However, direct constraints on the onset of sedimentation within the Marwar basin are still scarce. In this study, we report U–Pb zircon, LA-ICP-MS, and SIMS ages from the Chhoti Khatu felsic volcanic rocks, interlayered with the Jodhpur Group sandstones (Lower Marwar Supergroup). The cathodoluminescence images of the zircons indicate complex morphologies, and core-rim textures coupled with the wide range of ages indicate that they are likely inherited or in the case of thin poorly indurated ash-beds, detrital in origin. The age spectra of 68 zircon analyses from our sampling display a dominant 800–900 Ma age peak corresponding to the age of basement "Erinpura granite" rocks in the region. The youngest inherited zircon from a felsic ash layer yielded a U–Pb age of 651 Ma ± 18 Ma that, together with previous studies and paleontological evidence, indicates a post-Cryogenian age for the initiation of Marwar sedimentation following a ~125 Ma hiatus between the end of Malani magmatism and Marwar deposition.
Oxygen and hafnium isotopic compositions, measured *in-situ* on U-Pb dated zircon grains from Paleoproterozoic to early Cambrian successions in NW India have implication for regional crustal evolution and supercontinent cycles. Analyzed zircon grains have high Th/U ratios (\>0.1), display strongly fractionated REE patterns, metamorphic overprint, and evidence of interaction with low temperature fluids. Their positive Ce and negative Eu anomalies preclude any Pb loss after zircon crystallization. The U-Pb age spectra (concordance between 90 and 110%) indicate prominent peaks at 2.6 to 2.4 Ga, 1.9 to 1.7 Ga, 1.6 to 1.5 Ga, 1.2 to 1.0 Ga and 0.9 to 0.7 Ga that coincide with the assembly and breakup of Precambrian supercontinents. The Hf model ages of zircon grains with mantle like δ^18^O values reveal continuous generation of the continental crust from 3.3 to 1.3 Ga in NW India with major episodes during 3.3 to 2.7 Ga and 1.7 to 1.5 Ga. These ages correspond well with the 3.4 to 2.9 Ga and 2.2 to 1.6 Ga age peaks recognized in detrital zircon populations from eastern Australia and North America, underlining the significance of these time brackets in continental crust generation during the global continental evolution. Magmatic episodes at 1.9 to 1.7, 1.2 to 1.0 and 0.9 to 0.7 Ga are considered to represent crustal reworking rather than juvenile addition and the former two phases correspond with periods of supercontinent assembly. However, a progressive depletion in ^18^O from supra-mantle to mantle values in the 1.7 to 1.5 Ga zircons, coupled with their mantle-like ε~Hf(t)~ values, indicate at least some juvenile input. Moreover, the 1344 to 1120 Ma zircon grains with low δ^18^O (3.7--1.5‰) but high ε~Hf(t)~ (+8.1− +1.9 with one exception of −2.5) values signify rapid reworking of mantle derived materials in an extensional setting during this period. The 0.9 to 0.7 Ga peak, corresponding to the fragmentation of Rodinia supercontinent, documents crustal reworking that is in contradiction to the generally considered juvenile crustal addition in extensional setting associated with supercontinent breakup.
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