Reconstruction of the North China Craton within the Meso-Neoproterozoic supercontinents: evidence from large igneous provinces and rift sediments

Shuan-Hong Zhang1, Jun-Ling Pei1, Zai-Zheng Zhou2, Zhen-Yu Yang3, Yue Zhao1, Yuhang Cai1, Qi-Qi Zhang1, Guo-Hui Hu1, Sheng-Guang Zhuo4

1Institute of Geomechanics, Chinese Academy of Geological Sciences, Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resources, Beijing 100081, China;  2College of Earth Sciences and Engineering, Shandong University of Science and Technology, Qingdao 266590, China; 3College of Resources, Environment and Tourism, Capital Normal University, Beijing 100048, China; 4College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China

Large igneous provinces (LIPs) and rift sediments can provide robust tools for paleographic reconstructions of Precambrian supercontinents. In this presentation, we use correlations of the Meso-Neoproterozoic LIPs and magmatism and sedimentation in continental margin rift basins in North China Craton (NCC) and other continents, combined with the previously published paleomagnetic data, in order to give better constraints on paleopositions of the NCC within the Nuna (Columbia) and Rodinia supercontinents. Our results show that the NCC was adjacent to Siberia, Laurentia, Baltica, North Australian Craton (NAC) and India in the Nuna (Columbia) supercontinent, and the northern–northeastern margin of the NCC was connected with the northern margin of the NAC during the early-middle Mesoproterozoic period. Global spatial distributions of the 1.4-1.3 Ga LIPs and rift sediments and paleographic reconstructions suggested existence of a 1.4-1.3 Ga continental rift system between Laurentia, Siberia, Baltica, NAC and NCC, which resulted in breakup of the Nuna (Columbia) supercontinent. Interestingly, the ca. 1.30 Ga Bayan Obo world’s largest REE deposit and carbonatites in the northern NCC and the ca. 1.38–1.33 Ga Mountain Pass world’s second largest REE deposit and carbonatites in western margin of Laurentia are distributed in this rift system and are most likely related to 1.4–1.3 Ga continental rifting in the Nuna (Columbia) supercontinent.

New detrital zircon U-Pb and Hf isotopic data from the late Mesoproterozoic to Neoproterozoic sedimentary rocks in the eastern-southeastern NCC combined with paleomagnetic data suggest that during the late Mesoproterozoic to early Neoproterozoic period, the eastern-southeastern margin of the NCC was most likely connected to the western-southern Australian cratons in the Rodinia supercontinent. Breakup of the eastern-southeastern margin of the NCC from the western-southern Australian cratons occurred during 0.92-0.89 Ga as suggested by the Sariwon-Liaodong-Xuhuai mafic LIP in rifting basins in the eastern-southeastern NCC. During “Earth’s Middle Age” from 1.7 Ga to 0.75 Ga, the core of the Nuna (Columbia) and Rodinia supercontinents (including Laurentia, Siberia and Baltica) remains stable and these long-lived connections between Laurentia, Siberia and Baltica as the core of both Nuna and Rodinia suggest that the transition from Nuna to Rodinia was much less dramatic than the subsequent transition from Rodinia to Gondwana and Pangea, which is consistent with relatively lithospheric stability in “Earth’s Middle Age” that contrasts with the dramatic changes in preceding and succeeding eras.


Biography

Dr. Shuan-Hong Zhang’s research focuses mainly on Mesoproterozoic large igneous provinces and supercontinental reconstruction. He has published over two papers in Geology, Earth and Planetary Science Letters, Earth-Science Reviews and Precambrian Research in last 10 years.

Reconstruction of a Paleoproterozoic greenstone belt and tectonic implications (Toumodi Greenstone Belt, West Africa)

Hayman, Patrick1, Asmussen, Pascal1, Senyah, Gloria1, Tegan, Eudes2, Coulibaly, Inza3, Denyszyn, Steven4, Jessell, Mark4

1Queensland University of Technology, Brisbane, Australia, 2 Institut National Polytechnique Felix Houphouet Boigny, Yamoussoukro, Côte d’Ivoire, 3Université Nangui Abrogoua, Abidjan, Côte d’Ivoire, 4University of Western Australia, Perth, Australia

Despite many similarities between late Archean and Paleoproterozoic greenstone belts, volcanological, compositional, temporal and geometric variations reflect differences in lithospheric strength and geodynamics. We present new field, geochemical and geochronological (U-Pb LA-ICPMS and ID-TIMS) data of the Toumodi Greenstone Belt (Ivory Coast, West Africa) to reconstruct the stratigraphic, paleo-depositional environment and structural history of a well-preserved greenstone belt that represents one of the first post-Archean supracrustal sequences. We then compare and contrast results with a typical 2.7 Ga greenstone belt (Agnew, Western Australia) and highlight some important differences across the A-P boundary. The Toumodi Belt is 130 km long and >5 km wide and preserves a sequence 5-10 km thick, for which there is no evidence of pre-existing continental basement. The stratigraphy consists of three main stages: I) an initial (ca. 2.35-2.30 Ga) tholeiitic lava flow and sill succession intercalated with minor cherts and black mudstones, representing a mafic event in an open, anoxic and deep-water setting (mid-oceanic ridge basalt or oceanic island?); II) a diverse volcano-sedimentary package (ca. 2.30-2.15 Ga) of basalt/andesite lavas and turbidites that formed in deep water, as well as pyroclastic (scoria/tuff cones) and epiclastic deposits, including debris avalanche flow deposits, that formed in a subaerial setting; and III) an uppermost (ca. 2.15-2.05 Ga) sequence of felsic pyroclastic and epiclastics rocks that formed in a subaerial setting, as well as coeval and distal turbidites. Stages II and III form a synclinal sequence, while stage I forms only on the western edge of the belt. Similarities with 2.7 Ga greenstones include transitions from mafic to felsic volcanism and subaqueous to subaerial environments. Important differences include the protracted history (>250 vs 70 Myrs), belt asymmetry, and abundance of emergent stratigraphy (especially during stage II) that reflect multiple thermal events, accretionary tectonics, and stiffer continents, respectively.


Biography

Dr Hayman’s principal research focuses on field data and geochemical techniques to resolve volcanic, terrane and ore forming processes of the Earth at a range of scale, from outcrops to terranes.

Reconstructing the Mesoproterozoic palaeogeography of northern Australia through coupled detrital thermo- and geo-chronometers

Yang, Bo1, Collins, Alan1, 2, Blades, Morgan1, Jourdan, Fred3

 1Tectonics and Earth Systems Research Group, Mawson Centre for Geosciences (MCG), Department of Earth Sciences, The University of Adelaide, SA 5005, Australia, 2Mineral Exploration Cooperative Research Centre (MinEX CRC), WA 6151, Australia, 3Western Australian Argon Isotope Facility, Department of Applied Geology, Curtin University, Perth, WA 6845, Australia.

This study presents detrital muscovite 40Ar/39Ar data from the Mesoproterozoic Roper Group and the overlying latest Mesoproterozoic to early Neoproterozoic unnamed successions in the Beetaloo Sub-basin, northern Australia. Detrital muscovite chronology, compiled with the previous detrital zircon data, is used to identify basin source regions, providing integrated thermo- and geo- constraints on the basin provenance. The coupled detrital thermo- and geo-chronometers illustrate a dynamics tectonothermal history of the North Australia Craton (NAC) through the Mesoproterozoic. 

Data show that the Bessie Creek Sandstone, the oldest analysed formation from the Roper Group, provenance from multiple sources, whereas the overlying formation (the Velkerri Formation) consists of detritus from a dominant source. The predominant ca. 1.48 Ga muscovite and ca. 1.60 Ga zircon analyses seen in the Velkerri Formation closely match the published data from the exposed basement rocks to the southeast of the basin (e.g. Mt Isa Region, South Australia Craton (SAC), and the palinspastically adjacent Georgetown Province).These southeast source regions are located along the eastern margin of the Proterozoic Australia, and would have been uplifted, as rift-shoulders, during the separating between the Proterozoic Australia and the Laurentia at ca. 1.45 Ga. The uplifted southeast sources then became the most significant topographic highs, and subsequently swamped the basin with ca. 1.47 Ga detrital muscovite grains as well as the ca. 1.60 Ga detrital zircon grains, as those seen in the Velkerri Formation. The successions overlying the Velkerri Formation exhibit a gradually increased introduction of southern sources derived detritus. Data show that the Kyalla Formation, the youngest analysed formation from the Roper Group, was predominately sourced from the southern sources (e.g. Aileron Province and Tanami Region). The coeval absence of ca.1.47 Ga detrital muscovite and ca. 1.60 Ga detrital zircon grains indicates the Kyalla Formation received little contributions from the southeast sources. Further, detrital muscovite 40Ar/39Ar data show that the cumulated lag time of the Kyalla Formation is distinctly longer than the underlying formations. This is interpreted to reflect a different exhumation mechanism within source regions corresponding to a changed tectonic setting. The change in provenance and tectonic background is interpreted to relate to the closure of an ocean basin during the period 1.35–1.25 Ga, which resulted in uplift of the southern margin of the North Australia Craton. 

The latest Mesoproterozoic to early Neoproterozoic sandstone successions overlying the Roper Group provenance from the Musgrave Province. Coupled detrital zircon and muscovite data imply a rapid cooling at ca. 1.20–1.15 Ga that is interpreted to reflect a syn-orogenic exhumation during the Musgrave Orogeny. This quick exhumation is temporally consistent with the syn-orogenic cooling and exhumation in the Albany-Fraser Orogen. The synchronous orogenic exhumation events, seen in the Albany-Fraser Orogen and the Musgrave Province respectively, might represent a coeval collision of the West Australia Craton with the combined NAC and SAC, at ca. 1.20 Ga.


Biography

Bo Yang works in tectonics, basin evolution, sedimentary geochronology and geochemistry. He completed his PhD at the University of Adelaide in 2019 and is currently working as a post-doc in the same university.

A late Tonian plate reorganization event revealed by a full-plate Proterozoic reconstruction

Collins, Alan S.1, Blades, Morgan L.1, Merdith, Andrew S.2, Foden, John D.1

1Tectonics and Earth Systems (TES), Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia, 2EarthByte Group, School of Geosciences, The University of Sydney, Sydney, Australia

Plate reorganization events are a characteristic of plate tectonics that punctuate the Phanerozoic. They fundamentally change the lithospheric plate-motion circuit, influencing the planet’s lithosphere-mantle system and both ocean and atmospheric circulation through changes in bathymetry and topography. The development of full-plate reconstructions for deep time allows the geological record to be interrogated in a framework where plate kinematic reorganizations can be explored. Here, we interpret the geological record of the one of the most extensive tracts of Neoproterozoic crust on the planet (the Arabian-Nubian Shield) to reflect a late Tonian plate reorganization at ca. 800–715 Ma that switched plate-convergence directions in the Mozambique Ocean. This caused Neoproterozoic India to move towards both the African cratons and Australia-Mawson, instigating the closure of the intervening ocean and the future amalgamation of central Gondwana ca. 200 million years later. This plate kinematic change is coeval with constraints on break-up of the core of Rodinia between Australia-Mawson and Laurentia and Kalahari and Congo.


Biography

Alan Collins is a tectonic geologist with wide interests that diverge from a fascination of how our planet took the path it did because of plate tectonics.

Dynamics of arc-continent collision: The role of crustal-mantle dynamics on controlling the formation of basins in continental margins

Rodriguez-Corcho, Andres1,2 Móron-Polanco, Sara1,2; Farrington, Rebecca1; Beucher, Romain3; Moresi, Louis; Montes3, Camilo4.

1The University of Melbourne, Melbourne, Parkville, Australia, 2The University of Sydney, Sydney, Camperdown, Australia, 3Australian National University, Canberra, Australia, 4Universidad del Norte, Barranquilla, Colombia

Arc-continent collision is the process by which intra-oceanic arc crust is accreted to continental margins. It is a process which commonly occurs in the tectonic-cycle and the most important mechanism that enables the growth of the continental crust since Phanerozoic times. We use numerical visco-plastic mechanical models to explore how compositional density contrasts and crustal-mantle dynamics control the formation of basins in continental margins during arc-continent collision. We performed a series of simulations only varying the thickness of the arc as it has been suggested to control the density profile (buoyancy) and rheology of intra-oceanic arcs and therefore the dynamics of collision. Modelling results show that arc-continent collision can evolve into two mechanisms: i) arc transference in dense arcs (15-31km in thickness), where the middle-lower arc crust is at least 2.1% denser than the adjacent continental crust-lithosphere; and ii) slab break-off in buoyant arcs (32-35 km in thickness), where the density contrast between the middle-lower intra-oceanic arc crust and the adjacent continental crust-lithosphere is lesser than the 2.1%. In turn, these two mechanisms trigger the partition of stress into extension in the continental margin and compression towards the subducting plate. We interpret that the partitioning in stress into compression and extension in all simulations is caused by a gravity-driven flow that equilibrates the contrasts in gravitational potential energy (GPE) stored in the lithosphere during arc-continent collision and episodes of lithospheric thickening. We argue that this gravity-driven flow applies a horizontal gravitational force directed from the collided arc towards the subducting plate (compressional) and the continental margin (extensional). This simultaneous occurrence of compression and extension in an active plate boundary allows the formation of basins in the continental margin without the need of the fore-arc or back-arc extension mechanisms. Finally, we conclude that the large-scale mantle return flow emerged from crustal-mantle dynamics (slab-anchoring) facilitates the stress partitioning by enhancing: i) compression and lithospheric thickening; and ii) the contrast in GPE between the accreted arc and the continental margin during collision.


Biography

Andres is a 3rd year PhD student at the University of Melbourne which research interests are the understanding of the evolution and dynamics of subduction zones and accretionary continental margins. Specifically, his research focus on the dynamics of arc-continent collision and how this process relates to basin formation

Mapping and modelling a future passive margin in Afar, East Africa

Zwaan, Frank1,2; Corti, Giacomo3, Keir, Derek1,4, Sani, Federico1, Muluneh, Ameha5, Illsley-Kemp, Finnigan6, Papini, Mauro1.

1University of Florence, Florence, Italy; 2University of Bern, Bern, Switzerland; 3National Italian Research Council, Florence, Italy; 4University of Southampton, Southampton, United Kingdom;         5Addis Ababa University, Addis Ababa, Ethiopia; 6Victoria University Wellington, Wellington, New Zealand (email: frank.zwaan@geo.unibe.ch)

This multidisciplinary research project (Zwaan et al. 2020a, b) focuses on the tectonics of the Western Afar Margin (WAM), which is situated between the Ethiopian Plateau and Afar Depression in East Africa. The WAM represents a developing passive margin in a highly volcanic setting, thus offering unique opportunities for the study of rifting and (magma-rich) continental break-up so that our results have both regional and global implications.

We show by means of earthquake analysis that the margin is still deforming under a ca. E-W extension regime (a result also obtained by analysis on fault measurements from recent field campaigns), whereas Afar itself undergoes a more SW-NE extension (Zwaan et al. 2020a). Together with GPS data, we see Afar currently opening in a rotational fashion. This opening is however a relatively recent and local phenomenon, due to the rotation of the Danakil microcontinent modifying the regional stress field (since 11 Ma). Regional tectonics is otherwise dominated by the rotation of Arabia since 25 Ma and should cause SW-NE (oblique) extension along the WAM. This oblique motion is indeed recorded in the large-scale en echelon fault patterns along the margin, which were reactivated in the current E-W extension regime. We thus have good evidence of a multiphase rotational history of the WAM and Afar.

Furthermore, analysis of the margin’s structural architecture reveals large-scale flexure towards Afar, likely representing the developing seaward-dipping reflectors that are typical for magma-rich margins. Detailed fault mapping and earthquake analysis show that recent faulting is dominantly antithetic (dipping away from the rift), bounding remarkable marginal grabens, although a large but older synthetic escarpment fault system is present as well.

By means of analogue modelling efforts (Zwaan et al. 2020b) we find that marginal flexure indeed initially develops a large escarpment, whereas the currently active structures only form after significant flexure. Moreover, these models show that marginal grabens do not develop under oblique extension conditions. Instead, the latter model boundary conditions create the large-scale en echelon fault arrangement typical of the WAM. We derive that the recent structures of the margin could have developed only after a shift to local orthogonal extension. These modeling results support the multiphase extension scenario as described above.

Altogether, our findings are highly relevant for our understanding of the structural evolution of (magma-rich) passive margins. Indeed, seismic sections of such margins show very similar structures to those of the WAM. However, the general lack of marginal grabens, which are so obvious along the WAM, can be explained by the fact that most rift systems undergo or have undergone oblique extension, often in multiple phases during which structures from older phases affect subsequent deformation.

References

Zwaan, F., Corti, G., Sani, F., Keir, D., Muluneh, A., Illsley-Kemp, F., Papini, M. 2020(a): Structural analysis of the Western Afar Margin, East Africa: evidence for multiphase rotational rifting. Tectonics. http://doi.org/10.1029/2019TC006043

Zwaan, F., Corti, G., Keir, D., Sani, F. 2020(b). An analogue modeling study of marginal flexure in Afar, East Africa: implications for passive margin formation. Tectonophysics. https://doi.org/10.1016/j.tecto.2020.228595


Biography

Frank Zwaan is a structural geologist and analogue modeller specialized in rift tectonics. He studied earth sciences in the Netherlands and France, finished his PhD in Switzerland, did a Postdoc in Italy and is currently working at the University of Bern in Switzerland

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

As a broadly based professional society that aims to represent all Earth Science disciplines, the GSA attracts a wide diversity of members working in a similarly broad range of industries.