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David A D Evans - One of the best experts on this subject based on the ideXlab platform.
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a pan latitudinal Rodinia in the tonian true polar wander frame
Earth and Planetary Science Letters, 2020Co-Authors: David A D Evans, Xianqing Jing, Zhenyu Yang, Yabo Tong, Heng WangAbstract:Abstract A new paleomagnetic and geochronological study was conducted on the Tonian Chengjiāng Formation from Yunnan Province, South China, to examine the recent reported true polar wander event (TPW) during 825–750 Ma and clarify the position of South China in the Rodinia supercontinent. Detailed thermal demagnetization revealed two remanent magnetic components. A low-temperature component separated below 300 °C is interpreted as a recent viscous remanence. Additionally, a high-temperature component (H1) with unblocking temperature up to 690 °C is revealed. Passing both the fold test and reversal test, and recording at least two and half magnetochrons, H1 is suggested to be a primary remanence. The paleomagnetic pole (CJH1, 33.4°N, 56.1°E, d p / d m = 7.3 ° / 8.9 ° ) calculated from component H1 has no similarities to the Phanerozoic apparent polar wander path of South China. SHRIMP II U-Pb zircon data from a tuff bed near the paleomagnetic sampling sites suggest that the H1 pole has an age of ca. 800 Ma. Combining the reported Tonian paleomagnetic results from South China and Svalbard, we suggest a ∼63° TPW event during 825–790 Ma. Under this TPW paleomagnetic frame and using the reliable Tonian paleomagnetic results from other continents, we reconstruct the main part of Rodinia. This new configuration of Rodinia reconstructs South China and India at its northern periphery, and within the polar or high latitude zone during ca. 900–750 Ma. The polar location of those cratons, together with the mid-high latitudinal distribution of Australia, Congo and Baltica, suggests that Rodinia was a pan-latitudinal rather than an equatorially distributed supercontinent. The reconstruction also suggests that the breakup of the Rodinia should have been after 750 Ma but before 720 Ma. Despite similarities of their assembly and configuration, Rodinia and Pangea affected the Earth system differently.
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neoproterozoic paleogeography of the tarim block an extended or alternative missing link model for Rodinia
Earth and Planetary Science Letters, 2017Co-Authors: Bin Wen, David A D EvansAbstract:Abstract Recent reconstructions of the Rodinia supercontinent and its breakup incorporate South China as a “missing link” between Australia and Laurentia, and place the Tarim craton adjacent to northwestern Australia on the supercontinent's periphery. However, subsequent kinematic evolution toward Gondwana amalgamation requires complex geometric shuffling between South China and Tarim, which cannot be easily resolved with the stratigraphic records of those blocks. Here we present new paleomagnetic data from early Ediacaran strata of northwest Tarim, and document large-scale rotation at near-constant paleolatitudes during Cryogenian time. The rotation is coeval with Rodinia breakup, and Tarim's paleolatitudes are compatible with its placement between Australia and Laurentia, either by itself as an alternative “missing link” or joined with South China in that role. At the same time, indications of subduction-related magmatism in Tarim's Neoproterozoic record suggest that Rodinia breakup was dynamically linked to subduction retreat along its northern margin. Such a model is akin to early stages of Jurassic fragmentation within southern Gondwana, and implies more complicated subduction-related dynamics of supercontinent breakup than superplume impingement alone.
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paleomagnetic evidence for a large rotation of the yukon block relative to laurentia implications for a low latitude sturtian glaciation and the breakup of Rodinia
Geological Society of America Bulletin, 2017Co-Authors: Athena Eyster, David A D Evans, Justin V Strauss, Charlie F Roots, R R Fu, B P Weiss, Galen P Halverson, Francis A MacdonaldAbstract:Understanding the tectonic history of the supercontinent Rodinia is crucial for testing proposed links among Neoproterozoic tectonics, supercontinent cycles, climate, and biogeochemistry. The Neoproterozoic Mount Harper volcanics of the Ogilvie Mountains, Yukon, Canada, interfinger with Sturtian-age (ca. 717−660 Ma) glacial deposits that were deposited in narrow, fault-bounded basins related to the breakup of Rodinia. Here, we present new paleomagnetic data from the Mount Harper volcanics and isolate four paleomagnetic directions: a low-temperature direction recording the present geomagnetic field, a mid-temperature direction consistent with a Cretaceous overprint, and two high-temperature directions, one of which is carried by hematite and likely represents a chemical overprint, and the other of which is carried by magnetite and likely is a primary direction. This primary pole passes the fold and conglomerate tests and includes a reversal but is 50° away from the coeval 721−712 Ma Laurentian Franklin large igneous province pole. This difference can be reconciled using a 50° counterclockwise rotation of the Yukon block relative to Laurentia. The prerotation reconstruction of the Yukon block relative to Laurentia aligns Neoproterozoic fault orientations and facies belts between the Wernecke and Mackenzie Mountains, rectifies paleoflow measurements in Mesoproterozoic and Paleoproterozoic strata, and realigns the orientation of the ca. 1260 Ma Bear River dikes with the Mackenzie dike swarm of northern Canada. This reconstruction also facilitates future studies that relate Neoproterozoic sedimentary and structural patterns to the fragmentation of Rodinia. Finally, this low-latitude pole supports the snowball Earth interpretation of the ca. 717 Ma Sturtian glacial deposits.
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paleomagnetism of mesoproterozoic margins of the anabar shield a hypothesized billion year partnership of siberia and northern laurentia
Precambrian Research, 2016Co-Authors: David A D Evans, Roman Veselovsky, Peter Yu Petrov, V. E. Pavlov, A. V. ShatsilloAbstract:Abstract Siberia and Laurentia have been suggested as near neighbors in Proterozoic supercontinents Nuna and Rodinia, but paleomagnetic evidence has been sparse and ambiguous. Here we present four new paleomagnetic poles from undeformed Paleo-Mesoproterozoic (lower Riphean) sedimentary rocks and mafic intrusions of the northwestern Anabar uplift in northern Siberia. Combining these results with other Proterozoic data from Siberia and Laurentia, we propose a tight juxtaposition of those two blocks (Euler parameters 77°, 098°, 137° for Anabar to North America) spanning the interval 1.7–0.7 Ga, constituting a long-lived connection that outlasted both the Nuna and Rodinia supercontinental assemblages.
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Assembly and breakup of the core of Paleoproterozoic-Mesoproterozoic supercontinent Nuna
Geology, 2011Co-Authors: David A D Evans, Ross N MitchellAbstract:Idealized conceptual models of supercontinent cyclicity must be tested against the geologic record using pre-Pangean reconstructions. We integrate tectonostratigraphic records and paleomagnetic data from Siberia, Laurentia, and Baltica to produce a quantitative reconstruction of the core of the Nuna supercontinent at 1.9–1.3 Ga. In our model, the present southern and eastern margins of Siberia juxtapose directly adjacent to, respectively, the arctic margin of Laurentia and the Uralian margin of Baltica. Consistent tectonostratigraphic records of the three cratons collectively indicate the history of Nuna9s assembly and breakup. According to this reconstruction, the late Mesoproterozoic transition from Nuna to Rodinia appears to have been much less dramatic than the subsequent late Neoproterozoic transition from Rodinia to Gondwana.
M. Santosh - One of the best experts on this subject based on the ideXlab platform.
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a type granites in the western margin of the siberian craton implications for breakup of the precambrian supercontinents columbia nuna and Rodinia
Precambrian Research, 2019Co-Authors: I I Likhanov, M. SantoshAbstract:Abstract The tectonic evolution of the Siberian Cratonic margins offers important clues for global paleogeographic reconstructions, within the complex continental collage of Central Asia. The Yenisey Ridge fold–and–thrust belt at the western margin of the Siberian Craton forms part of the Central Asian Orogenic Belt (CAOB) and is a key to understand the Precambrian tectonic evolution of the Siberian Craton and crustal growth in the CAOB, the world's largest Phanerozoic accretionary orogenic belt. Here we report the occurrence of A-type granites with geochemical features indicating intraplate setting from the Yenisey Ridge and provide evidence for rift-related magmatism. Zircon SHRIMP U–Pb analyses coupled with in situ U–Th–Pb geochronology of monazite constrain the timing of emplacement of the rift–related granitoids and suggest two consequential breakup events. The magmatic events at 1380 Ma and 800–720 Ma along the western margin of the Siberian Craton and other continental blocks can be associated with the breakup of the Precambrian supercontinents Nuna-Columbia (1.8–1.3 Ga) and Rodinia (1.2–0.7 Ga). These pre-Grenville and post-Grenville episodes of regional crustal evolution are correlated with the synchronous successions and similar style of rocks along the Arctic margin of Nuna–Columbia and Rodinia and supports the spatial proximity of Siberia and North Atlantic cratons (Laurentia and Baltica) over the long period 1.38–0.72 Ga. Our data confirm the proposed Neoproterozoic paleogeographic reconstructions of Columbia and Rodinia as constrained from the large igneous province (LIP) record.
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neoproterozoic intraplate magmatism along the western margin of the siberian craton implications for breakup of the Rodinia supercontinent
Precambrian Research, 2017Co-Authors: I I Likhanov, M. SantoshAbstract:Abstract The fold-and-thrust belt of Yenisey Ridge is a key to understand the Precambrian tectonic evolution of the Siberian Craton as well as crustal evolution in the Central Asian Orogenic Belt. Here we report the occurrence of felsic and mafic dyke swarms in the Yenisey Ridge providing evidence for rift-related magmatism. The dikes and sills occur in narrow linear zones along faults, and show bimodal composition with geochemical features indicating intraplate settings. Zircon SHRIMP U-Pb analyses constrain the timing of emplacement of the dykes as 797–792 Ma. The magmatic event at c. 800 Ma along the western margin of the Siberian Craton and other continental blocks can be correlated with the onset of the breakup of the Neoproterozoic Rodinia supercontinent. Post-Grenville episodes of regional crustal evolution are correlated with the synchronous successions and similar style within the Valhalla orogen along the Arctic margin of Rodinia and supports the spatial proximity of Siberia and North Atlantic cratons (Laurentia, Baltica, Svalbard) at c. 800 Ma, as proposed for the Neoproterozoic paleogeographic reconstructions for the Rodinia supercontinent and as robustly constrained from large igneous province (LIP) record.
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superplume supercontinent and post perovskite mantle dynamics and anti plate tectonics on the core mantle boundary
Gondwana Research, 2007Co-Authors: Shigenori Maruyama, M. Santosh, Dapeng ZhaoAbstract:Abstract The Western Pacific Triangular Zone (WPTZ) is the frontier of a future supercontinent to be formed at 250 Ma after present. The WPTZ is characterized by double-sided subduction zones to the east and south, and is a region dominated by extensive refrigeration and water supply into the mantle wedge since at least 200 Ma. Long stagnant slabs extending over 1200 km are present in the mid-Mantle Boundary Layer (MBL, 410–660 km) under the WPTZ, whereas on the Core–Mantle Boundary (CMB, 2700–2900 km depth), there is a thick high-V anomaly, presumably representing a slab graveyard. To explain the D″ layer cold anomaly, catastrophic collapse of once stagnant slabs in MBL is necessary, which could have occurred at 30–20 Ma, acting as a trigger to open a series of back-arc basins, hot regions, small ocean basins, and presumably formation of a series of microplates in both ocean and continent. These events were the result of replacement of upper mantle by hotter and more fertile materials from the lower mantle. The thermal structure of the solid Earth was estimated by the phase diagrams of Mid Oceanic Ridge Basalt (MORB) and pyrolite combined with seismic discontinuity planes at 410–660 km, thickness of the D″ layers, and distribution of the ultra-low velocity zone (ULVZ). The result clearly shows the presence of two major superplumes and one downwelling. Thermal structure of the Earth seems to be controlled by the subduction history back to 180 Ma, except in the D″ layer. The thermal structure of the D″ layer seems to be controlled by older slab-graveyards, as expected by paleogeographic reconstructions for Laurasia, Gondwana and Rodinia back to 700 Ma. Comparison of mantle tomography between the Pacific superplume and underneath the WPTZ suggests the transformation of a cold slab graveyard to a large-scale mantle upwelling with time. The Pacific superplume was born from the coldest CMB underneath the 1.0–0.75 Ga supercontinent Rodinia where huge amounts of cold slabs had accumulated through collision-amalgamation of more than 12 continents. A high velocity P-wave anomaly on a whole-mantle scale shows stagnant slabs restricted to the MBL of circum-Pacific and Tethyan regions. The high velocity zones can be clearly identified within the Pacific domain, suggesting the presence of slab graveyards formed at geological periods much older than the breakup of Rodinia. We speculate that the predominant subduction occurred through the formation period of Gondwana, presumably very active during 600 to 540 Ma period, and again from 400 to 300 Ma during the formation of the northern half of Pangea (Laurasia). We correlate the three dominant slab graveyards with three major orogenies in earth history, with the emerging picture suggesting that the present-day Pacific superplume is located at the center of the Rodinian slab graveyard. We speculate the mechanism of superplume formation through a comparison of the thermal structure of the mantle combined with seismic tomography under the Western Pacific Triangular Zone (WPTZ), Laurasia (Asia), Gondwana (Africa), and Rodinia (Pacific). The coldest mantle formed by extensive subduction to generate a supercontinent, changes with time of the order of several hundreds of million years to the hottest mantle underneath the supercontinent. The Pacific superplume is tightly defined by a steep velocity gradient on the margin, particularly well documented by S-wave velocity. The outermost region of the superplume is characterized by the Rodinia slab graveyard forming a donut-shape. We develop a petrologic model for the Pacific superplume and show how larger plumes are generated at shallower depths in the mantle. We link the mechanism of formation of the superplume to the presence of the mineral post-perovskite, the phase transformation of which to perovskite is exothermic, and thus aids in transporting core heat to mantle, and finally to planetary space by plumes. We summarize the characteristics of tectonic processes operating at the CMB to propose the existence of an “anti-crust” generated through “anti-plate tectonics” at the bottom of the mantle. The chemistry of the anti-crust markedly contrasts with that of the continental crust overlying the mantle. Both the crust and the anti-crust must have increased in volume through geologic time, in close relation with the geochemical reservoirs of the Earth. The process of formation of a new superplume closely accompanies the process of development of anti-crust at the bottom of mantle, through the production of dense melt from the partial melting of recycled MORB, observed now as the ULVZ. When CMB temperature is recovered to near 4000 K through phase transformation, the recycled MORB is partially melted imparting chemical buoyancy of the andesitic residual solid which rises up from CMB, leaving behind the dense melt to sink to CMB and thus increase the mass of anti-crust. These small-scale plumes develop to a large-scale superplume through collision and amalgamation with time. When all recycled MORBs are consumed, it is the time of demise of superplume. Immediately above the CMB, anti-plate tectonics operates to develop anti-crust through the horizontal movement of accumulated slab and their partial melting. Thus, we speculate that another continent, or even a supercontinent, has developed through geologic time at the bottom of the mantle. We also evaluate the heating vs. cooling models in relation to mantle dynamics. Rising plumes control not only the rifting of supercontinents and continents, but also the Atlantic stage as seen by anchored ridge by hotspots in the last 200 Ma in the Atlantic. Therefore, we propose that the major driving force for the mantle dynamics is the heat supplied from the high-T core, and not the slab pull force by cooling. The best analogy for this is the atmospheric circulation driven by the energy from Sun.
Michael T.d. Wingate - One of the best experts on this subject based on the ideXlab platform.
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age and composition of neoproterozoic diabase dykes in north altyn tagh northwest china implications for Rodinia break up
International Geology Review, 2020Co-Authors: Shuguang Song, Michael T.d. Wingate, Chao Wang, Xiaoyong Yang, Zifu Zhao, Jinlong Dong, Xiaofeng Gao, Mengqi JinAbstract:Whether or not the Altyn Tagh terranes in northwest China were part of the Rodinia supercontinent is unclear due to the apparent absence of rift-related igneous rocks. We present U-Pb geochronology...
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global record of 1600 700 ma large igneous provinces lips implications for the reconstruction of the proposed nuna columbia and Rodinia supercontinents
Precambrian Research, 2008Co-Authors: Richard E Ernst, Michael T.d. Wingate, Kenneth L BuchanAbstract:Abstract Large igneous provinces (LIPs) are commonly associated with breakup of continents, and therefore, are a critical source of information to constrain paleocontinental reconstructions. We review the record of LIPs emplaced during the 1600–700 Ma interval. Regional-scale magmatic events at 1460, 1380, and 1280 Ma can be associated with the breakup of the proposed late-Paleoproterozoic supercontinent, Nuna (Columbia), events at 1300–900 Ma overlap with the assembly of Rodinia, and events at 825, 800, 780, 755, and possibly 720 Ma, are associated with the breakup of Rodinia. Furthermore, the extensional events at 1000 and 900 Ma are associated with breakups suggesting simultaneous assembly and breakup of different parts of the supercontinent. The possibility of spatially separated (independent) LIPs having the same age complicates the use of LIPs to constrain specific aspects of reconstructions. This study identifies such spatially separated but coeval LIPs at 1460, 1380, 1270, and 1115–1070 Ma (and possibly at 825, 780, and 755 Ma). Regionally grouped LIPs, possibly representing superplume events, are recognized at 825–755 Ma, and at 1280–1235 Ma. The use of the LIP record to assist the reconstruction of Rodinia will improve as numerous remaining poorly characterized magmatic units are dated using precise methods.
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models of Rodinia assembly and fragmentation
Geological Society London Special Publications, 2003Co-Authors: Sergei Pisarevsky, Michael T.d. Wingate, Chris Mca Powell, Simon P Johnson, David A D EvansAbstract:Amongst existing palaeogeographic models of the Rodinia supercontinent, or portions thereof, arguments have focused upon geological relations or palaeomagnetic results, but rarely both. A new model of Rodinia is proposed, integrating the most recent palaeomagnetic data with current stratigraphic, geochronological and tectonic constraints from around the world. This new model differs from its predecessors in five major aspects: cratonic Australia is positioned in the recently proposed AUSMEX fit against Laurentia; East Gondwanaland is divided among several blocks; the Congo-Sao Francisco and India-Rayner Cratons are positioned independently from Rodinia; Siberia is reconstructed against northern Laurentia, although in a different position than in all previous models; and Kalahari-Dronning Maud Land is connected with Western Australia. The proposed Rodinia palaeogeography is meant to serve as a working hypothesis for future refinements. There is general agreement that the Earth's continental crust may have been assembled to form the supercontinent, Rodinia, in the Late Mesoproterozoic and Early Neoproterozoic. Rodinia is thought to have been produced by collisional events of broadly Grenvillian (Late Mesoproterozoic) age, and to have been relatively long-lived (c. 1100-750Ma) (McMenamin & McMenamin 1990; Hoffman 1991). Nonetheless, there are several versions of its composition and configuration (e.g. Hoffman 1991 ; Dalziel 1997; Weil et al. 1998). Laurentia is thought to have formed the core of Rodinia because it is surrounded by passive margins formed during Late Neoproterozoic breakup of the supercontinent (Bond et at. 1984). Most Rodinia models propose that Australia, Antarctica and possibly South China (Li et al. 1999) may have been situated along Laurentia's western margin (unless otherwise stated, all geographic references are in present coordinates); Baltica and Amazonia, and the Rio de la Plata Craton may have lain along its eastern margin. The precise position of Siberia is disputed, but it is generally shown as lying along either the northern or the western margin of Laurentia. The position of the Congo and Kalahari Cratons is uncertain, with at least four reconstructions having been shown for Kalahari in the last few years (Powell et al. 2001). An alternative Neoproterozoic supercontinent, Palaeopangaea, was proposed by Piper (2000), based mainly on palaeomagnetic data. This model is similar to earlier reconstructions by the same author (Piper 1987 and refs cited therein), which were criticized by both Van der Voo & Meert (1991) and Li & Powell (1999). In addition, the recent publication about Palaeopangaea (Piper 2000) contains no references for the poles employed, making the model difficult to assess. For these reasons, it will not be discussed further in this paper. Several important results have been published recently that provide new geological, geochronological and palaeomagnetic constraints on Mesoproterozoic-Early Neoproterozoic palaeogeography. Palaeomagnetic data are necessary for quantitative constraints on Precambrian reconstructions. Unfortunately, these data are distributed very non-uniformly in time and space (Meert & Powell 2001 table 1). The majority of palaeomagnetic results for the interval during which Rodinia may have existed (c. ll00-750Ma) come from Laurentia and Baltica, and fragments of apparent polar wander paths (APWP) can be constructed for these two blocks. Data from other cratons are sparse, making it impossible to construct an APWP for each block. The palaeopositions of these blocks are based on comparisons of individual palaeopoles, hence relative palaeolongitudes are not constrained. The objective of this paper is to create a new model of the Rodinia supercontinent. Palaeomagnetism has been used to determine permissible fits for Rodinia; geological constraints, such as continuity of tectonic belts, and the presence of passive or active continental margins have been used to refine permissible fits into plausible reconstructions. There is also the global balance of Late Neoproterozoic rifted margins that needs to be accounted for in any acceptable reconstruction. Selection of reliable palaeomagnetic data is the key issue for many MesoproterozoicNeoproterozoic reconstructions (e.g. Powell et at. From YOSHIDA, M., WINDLEY, B. F. & DASGUPTA, S. (eds) 2003. Proterozoic East Gondwana: Supercontinent Assembly and Breakup. Geological Society, London, Special Publications, 206, 35-55. 0305-8719/03/$15 © The Geological Society of London. 36 SERGEIA. PISAREVSKY ET AL. 1993; Torsvik et al. 1996; Smethurst et al. 1998; Weil et al. 1998; Piper 2000). In the present synthesis (Table 1), only palaeomagnetic results with Q~4 are used (Van der Voo 1990). There are fewexceptions where less reliable data is referred to and all such cases are explained individually. However, existing data are insufficient to provide robust reconstructions for all cratons except Laurentia and Baltica. In addition, there are no reliable palaeomagnetic data for Amazonia, West Africa and Rio de la Plata in the interval 11 00-700 Ma. In attempting to reconstruct Rodinia, available information from the majority of Precambrian continental blocks was used. Because very little is known about the Rodinian connections of North China, NE Africa and Arabia, Avalonia, Cadornia, Omolon, and other fragments of continental crust from the Russian Far East, northern Alaska and southeastern Table 1. Palaeomagnetic poles at 1100-700 Ma
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Rodinia connections between australia and laurentia no sweat no auswus
Terra Nova, 2002Co-Authors: Michael T.d. Wingate, David A D EvansAbstract:Although geological comparisons between Australia and North America have provided a basis for various Neoproterozoic Rodinia reconstructions, quantitative support from precisely dated palaeomagnetic poles has so far been lacking. We report U–Pb ages and palaeomagnetic results for two suites of mafic sills within the intracratonic Bangemall Basin of Western Australia, one of which is dated at 1070 ± 6 Ma and carries a high-stability palaeomagnetic remanence. Comparison of the Bangemall palaeopole with Laurentian data suggests that previous reconstructions of eastern Australia against either western Canada (SWEAT) or the western United States (AUSWUS) are not viable at 1070 Ma. This implies that the Pacific Ocean did not form by separation of Australia–Antarctica from Laurentia, and that up to 10 000 km of late Neoproterozoic passive margins need to be matched with other continental blocks within any proposed Rodinia supercontinent. Our results permit a reconstruction (AUSMEX) that closely aligns late Mesoproterozoic orogenic belts in north-east Australia and southernmost Laurentia.
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a high quality mid neoproterozoic paleomagnetic pole from south china with implications for ice ages and the breakup configuration of Rodinia
Precambrian Research, 2000Co-Authors: David A D Evans, Joseph L Kirschvink, Michael T.d. WingateAbstract:Neoproterozoic (Sinian) sediments are exceptionally well preserved in the Three Gorges region (western Hubei Province) of the South China block. We report new paleomagnetic results, obtained independently by two separate laboratories, from a total of 157 samples of the 748±12 Ma, basal Sinian Liantuo Formation at its type locality. Detailed thermal demagnetization procedures and least-squares line analyses reveal three distinct magnetic components among the suite of samples. Two overprint components can be distinguished from each other by their laboratory unblocking temperatures. The first to be removed (‘C’), always annihilated below 600°C, is common throughout the dataset but is amenable to least-squares line-fitting in only 37 samples. It yields a pole which in present coordinates resembles Mesozoic overprints identified from previous studies in the Three Gorges region (75.7°N, 174.3°E, d_p=6.0°, d_m=8.3°, Q=4). The higher unblocking-temperature overprint (‘B’), always subsidiary to the ‘A’ component, is more prevalent than ‘C’ and was identified by line-fitting in 67 samples. The ‘B’ direction is very steep and generates a paleopole whose in situ coordinates do not resemble the Mesozoic–Cenozoic apparent polar wander path for South China, and whose tilt-corrected coordinates (20.3°N, 106.2°E, d_p=7.2°, d_m=7.3°, Q=5) bear no resemblance to any reliable Phanerozoic paleopoles from the South China block. The steep ‘B’ direction, if an unbiased representative of an ancient geomagnetic dipole field, was probably acquired some time in the 200 m.y. interval between deposition of the Liantuo Formation at ∼750 Ma and Cambrian time. The most stable component is a two-polarity remanence, removed at temperatures predominantly >630°C, which we infer to reside in hematite. A change in polarity of this component occupies a similar stratigraphic position (within 5 cm) among three outcrops separated by ∼100 m lateral distance. We calculate a mean paleomagnetic pole from each of the laboratories' datasets and combine these with a previously determined pole from correlative rocks in Yunnan [‘N1’ of Zhang and Piper, Precambrian Res. 85 (1997) 173–199], to obtain an overall weighted mean paleomagnetic pole (04.4°N, 161.1°E, A95=12.9°, Q=7) for the South China block at 748±12 Ma. The combined ‘Z1’ pole is considered to be primary based on its thermal stability, its magnetostratigraphic consistency, and a soft-sediment fold test determined by previous work. Results from individual sampling areas constrain the depositional paleolatitude of the Liantuo Formation and equivalent Sinian rocks to 30–40°. This result applies to one or both of the stratigraphically adjacent Chang'an and Nantuo glacial deposits; unfortunately, it is neither high nor low enough to refute any of the conceptual models for the enigmatic Neoproterozoic glaciations. The new basal Sinian paleopole, in the context of recent paleomagnetic and geochronological results from Australia, suggests that the Nantuo glaciation is pre-Marinoan. The new ‘Z1’ pole may also provide constraints on the various proposed reconstructions of South China's position in Rodinia. In particular, a paleoposition adjacent to northwestern Australia at ∼750 Ma requires a specific relative orientation between the two blocks. Likewise, if Rodinia were still intact by 750 Ma, South China may have lain between Australia and Laurentia only in an orientation different from that originally proposed in the ‘missing link’ hypothesis. As a final alternative, the new paleomagnetic data could be used to position South China, Australia, and Laurentia in an immediately post-Rodinian paleogeography around the nascent Pacific Ocean.
Fraukje M Brouwer - One of the best experts on this subject based on the ideXlab platform.
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meso neoproterozoic arc related sediments of the xiahe group in the qinling block central china implications for the paleogeographic reconstruction of Rodinia
Precambrian Research, 2021Co-Authors: Limin Zhao, J P Zheng, Hua Xiang, Guoqing Wang, Wenjiao Xiao, Ming Chen, Fraukje M BrouwerAbstract:Abstract The Meso-Neoproterozoic Rodinia supercontinent formed a coherent large landmass, which was later dispersed over all current major continents and a number of microcontinents. The Qinling block is a Precambrian continental mass, located in the Qinling orogenic belt, which marks the junction of the North China and South China cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of metasedimentary rocks from the Xiahe Group, which is a key unit of the Precambrian basement in the Qinling block, to constrain the paleogeographic reconstruction of Rodinia. The studied metasedimentary rocks have detrital zircon ages of 3054–1082 Ma that peak at 1172 Ma and 1582 Ma. The protoliths of the metasedimentary rocks are mainly shales and wackes with maximum depositional ages from 1147 to 1082 Ma, representing a part of a continental arc-related sedimentary sequence. Combining our results with existing data, we propose that their protoliths constituted a sedimentary series including an older sequence of basement and a younger sequence with depositional ages between 1262 and 840 Ma. The detritus that is older than 1266 Ma was sourced from the continental margin of the Indian craton, which was part of the Columbia supercontinent. There was a Paleo-Mesoproterozoic continental nucleus in the Qinling block that split from the margin of the Indian craton during the breakup of Columbia. The source rocks for the younger detritus were arc magmatic rocks in the Qinling block, which formed in a continental arc by oceanic lithosphere subduction during the assembly of Rodinia. A sequence of oceanic subduction beneath the continental nucleus of the Qinling block (1262–981 Ma), arc-continent collision between the continental nucleus and the Indian craton (981–911 Ma), continuous subduction of oceanic crust beneath the block with formation of a mature volcanic arc (929–833 Ma), and continental rifting (833–774 Ma) during the formation of the Qinling block was identified. The block faced the Neoproterozoic ocean during the assembly of Rodinia, and finally rifted off the supercontinent during its breakup to form an isolated arc terrane
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geochemical and zircon u pb hf isotopic study of metasedimentary rocks from the huangyuan group of the central qilian block nw china implications for paleogeographic reconstruction of Rodinia
Precambrian Research, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Fraukje M BrouwerAbstract:Abstract We present a systematic study of micaschists and felsic gneisses from the Huangyuan Group of the Central Qilian block in NW China, with aims to unravel the connection with the Rodinia supercontinent. The micaschists have detrital zircon ages of 2895–928 Ma that peaking at 1.80–1.40 Ga. They show strongly increasing zircon eHf(t) values of −8.1 to +12.1 from 1.6 Ga to 1.4 Ga. Detrital zircon ages from the felsic gneisses are dominantly 960–913 Ma with eHf(t) values of −0.1 to −10.7. The micaschists have a wide range of whole-rock major element compositions, and the felsic gneisses have higher SiO2 contents, combined with lower other major element contents than those of the micaschists. All samples have trace element compositions consistent with upper continental crustal origin. The protoliths of the micaschists are dominantly shales and minor wackes with maximum depositional ages from ca. 1317 to 928 Ma. The protoliths of the felsic gneisses are mostly wackes with a maximum depositional age of ca. 927 Ma. The source materials for these metasedimentary rocks originated from intermediate to felsic igneous rocks. The variable maximum depositional ages of the metasedimentary rocks in the Huangyuan Group indicate that their protoliths constituted a sedimentary series with a long history of deposition starting at ca. 1317 Ma in an oceanic island arc-related basin that developed through a transitional continental arc-related basin into an active continental marginal basin at ca. 927 Ma. It is inferred that the 1795–1321 Ma detritus was sourced from juvenile arc crust at the margin of the Indian or the Western Australian craton. The source rocks for 1317–913 Ma detritus were arc magmatic rocks formed during assembly of Rodinia. A sequence of initial intra-oceanic subduction (ca. 1317–967 Ma) and continuous oceanic crust-continent subduction with formation of a mature continental arc (ca. 967–896 Ma) at the margin of Rodinia during the formation of the Central Qilian block is suggested.
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early neoproterozoic magmatism in the central qilian block nw china geochronological and petrogenetic constraints for Rodinia assembly
Geological Society of America Bulletin, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Ke Wang, Fraukje M BrouwerAbstract:The supercontinent Rodinia existed as a coherent large landmass from 900 to 750 Ma and is now dispersed over all current major continents. Controversy has long surrounded the reconstructions of the East Asian blocks in Rodinia, especially the South China craton and nearby microcontinents. The Central Qilian block is a Precambrian microcontinent in the early Paleozoic Qilian orogenic belt, which is located in the northeastern part of the Qinghai-Xizang (Tibet) Plateau and marks the junction of the North China, South China and Tarim cratons. The formation and tectonic affinity of the Precambrian basement in the Central Qilian block is unclear, which affects our understanding of the assembly of Rodinia. The Huangyuan Group and the Maxianshan Group crop out in the eastern part of the block and represent the lower part of the basement. In this paper, we present a systematic study of the petrology, whole-rock geochemistry, and geochronology of amphibolites and orthogneisses from the Huangyuan and Maxianshan Groups. The protolith of the amphibolites was tholeiitic and calc-alkaline gabbro or gabbroic diorite formed in a continental arc environment, with laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) zircon U-Pb ages of 967–957 Ma, a wide range of eHf(t) values of –3.74 to +5.06 and TDM1 model ages peaking at 1470 Ma and 1607 Ma. Minor inherited zircon grains with older ages of 1207–1515 Ma were collected from the amphibolites. The primitive magma was derived from partial melting of a spinel-facies fertile (lherzolite) lithospheric mantle that was modified by fluids and melts from a subducted slab. Fractionation of olivine, Fe-Ti oxides and plagioclase played a dominant role in the magma differentiation for gabbroic rocks in the Huangyuan Group, while fractionation of olivine and clinopyroxene controlled differentiation to form Maxianshan Group gabbros. The protolith of orthogneisses includes weakly peraluminous I-type and A2-type granites with consistent LA-ICPMS zircon U-Pb ages of 963–936 Ma, a wide range of eHf(t) values of –3.86 to +6.15 and TDM2 model age peaks at 2001 Ma and 1772 Ma. A few inherited zircon grains yield ages of 1033–2558 Ma. The peraluminous I-type granites resulted from a low-pressure partial melting process and the peraluminous A-type granites were derived from a charnockite source heated by large-scale magmatic underplating. Fractionation of plagioclase, biotite, and K-feldspar from the magma played the main role during the generation of the granitoids. The intrusion of these granites is related to a back-arc extension. It is inferred that the lower part of Precambrian basement of the Central Qilian block is composed mainly of early Neoproterozoic rock assemblages formed in a trench-arc-basin system during the assembly of the Rodinia supercontinent, with probable existence of late Paleoproterozoic to Mesoproterozoic continental nuclei. Combining our results with existing data, we identify a sequence of initial intra-oceanic subduction (ca. 1121–967 Ma) in front of a continental nucleus, continuous subduction of oceanic crust beneath the continental mass with formation of a mature continental arc and a back-arc basin (ca. 967–896 Ma) and continental rifting (
Rodinia and faced the Neoproterozoic Mirovoi Ocean. The breakup of the supercontinent left the Central Qilian block as a late Neoproterozoic isolated arc terrane.
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mid neoproterozoic diabase dykes from xide in the western yangtze block south china new evidence for continental rifting related to the breakup of Rodinia supercontinent
Precambrian Research, 2015Co-Authors: Jian Wang, Xiaozhuang Cui, Xinsheng Jiang, Xuance Wang, Jiewen Zhuo, Qi DengAbstract:The petrogenesis of widespread Mid-Neoproterozoic mafic dykes is crucial for the paleographic position of the South China Block (SCB) in Rodinia supercontinent and the mechanism of Rodinia breakup. Here, new detailed geochronological and geochemical data on the diabase dykes from Xide in the western Yangtze Block are presented. Zircon SHRIMP/LA-ICP-MS U-Pb dating shows that four diabase samples yield uniform crystallization age varying from 796 +/- 6 Ma to 809 +/- 15 Ma, while one sample gives a slight older age of 824 +/- 11 Ma that is overlapped with ca. 810 Ma within uncertainties. This suggests that the Xide diabase dykes emplaced at ca. 800-810 Ma and were coeval with regional bimodal magmatism (e.g., the Suxiong bimodal volcanics). The Xide diabase dykes are characterized by low SiO2 contents, high Mg# values and Cr, Ni contents, relative enrichment of light rare-earth elements, and slight depletion of high field strength elements (e.g., Nb, Ta, Zr, and Hf) and nearly constant Zr/Hf, Nb/Ta and Nb/La ratios. Our analyses indicate that the diabase was mainly produced by interaction between lithospheric and asthenospheric mantle. Moreover, the diabase samples display geochemical characteristics affinity with typical intra-plate basalts. Together with the widespread coeval bimodal magmatic suite and sedimentary records in the Kangdian Rift, we proposed that the western Yangtze Block once experienced continental rifting during the Mid-Neoproterozoic, which also occurred in other Rodinia blocks, such as Tarim, Australia and North America. In addition, the Grenville-aged magmatism records throughout SCB with the widespread Mid-Neoproterozoic rift-related magmatism and sedimentation records imply that SCB probably played a key role in the assembly and breakup of Rodinia supercontinent. (C) 2015 Elsevier B.V. All rights reserved.
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the willouran basic province of south australia its relation to the guibei large igneous province in south china and the breakup of Rodinia
Lithos, 2010Co-Authors: Zhengxiang Li, Xuance Wang, Xianhua Li, Yueheng YangAbstract:Abstract The Willouran Basic Province in South-Central Australia and the Guibei large igneous province (LIP) in the South China Block are two of the most prominent Neoproterozoic LIPs related to the breakup of the supercontinent Rodinia. The Willouran Basic Province is dominated by tholeiitic mafic dykes (the Gairdner dykes), flood basalts (the Wooltana basalts), and mafic intrusions. The basaltic suites across a distance of more than 1000 km have similar immobile major element compositions, uniform tholeiitic OIB-type trace element distribution patterns, and identical Hf–Nd isotopic signatures. Geochemical analyses from this study imply that their generation may have involved both depleted and enriched mantle sources, similar to that of the Guibei LIP. The age distributions of the two LIPs are also comparable, peaking at ca. 825 Ma. This simultaneous flare-up of mafic magmatism in the two continents, including high-temperature lavas found in the South China Block, coincides with the starting up of widespread continental rifting in Rodinia. We thus speculate that the two LIPs could have been parts of a once contiguous LIP, which was dismembered during the breakup of Rodinia. This work thus provides additional support for the proposed South China–Australia connection in Rodinia.
