Internal dynamics of magma ocean and its linkage to atmospheres

Geological and astronomical observations on the‘‘lava world’’of the rocky planet,with additional theoretical interpretation of Moon’s crustal formation,bring up to the occurrence of the magma ocean and lava ponds,which inherits accretion energy of rocky planetesimal and evolves with subsequent energy releases.Hemispherical or global oceans of silicate melt could be a widespread lava phase after rocky planet accretion as well as large impact and could persist on planets on orbits around other stars for various time scales.The processes of magma ocean formation and solidification change the phases,cause element segregations,and strongly affect the earliest compositional differentiation and volatile content of the terrestrial planets.They form the starting point for cooling to mildly habitable conditions and for the onset of thermally driven solid-state mantle convection.The formation and crystallization of magma oceans also influence the assembly of a core,the origin of a crust,initiation of tectonics,and formation of an atmosphere.It is inevitable to investigate the magma ocean dynamics of such an early period of Earth evolution.This review focuses on the internal dynamics of magma oceans after planetesimal accretion and planetary formation including turbulence,particle motion,and solid-state convection,which determine the associated processes of cooling,crystallization,and convection of magma ocean.Geochemical differentiation is discussed correspondingly.The thermodynamics of equilibration between a magma ocean and an overlying,outgassed atmosphere is also discussed,highlighting the need for more data on volatile solubility in silicate melts.The effect of coupling between magma ocean and solid-state mantle convection is also discussed.

Late Eocene–early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

There are many large-scale Cenozoic sedimentary basins with plentiful river deltas,deep-water fans and carbonate platforms in the southern South China Sea.The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene,and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area.However,systematic analyses are still lacking regarding its sediment composition and potential source suppliers.No consensus has been reached yet on the provenance evolution and sedimentary infilling processes,which seriously impeded the oil-and-gas exploration undertakings.By combining with sedimentaryfacies identification,heavy mineral assemblages,elemental geochemistry and detrital zircon U-Pb dating,this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan.In general,the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity.The continual southward subduction of the protoSouth China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo.The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts.From the late Eocene to the early Miocene,the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland.The Zengmu Basin was widely deposited with delta plain and neritic facies sediments,while the Brunei-Sabah Basin,to the farther east,was ubiquitously characterized by turbiditic sequences.The Crocker Fan successions are overall thick layers of modest-grained sandstones,which formed high-quality reservoirs in the southern South China Sea region.

New interpretation on the provenance changes of the upper Pinghu–lower Huagang Formation within Xihu Depression,East China Sea Shelf Basin

Both Pinghu and Huagang formations are important hydrocarbon reservoirs of the Xihu Depression in the East China Sea Shelf Basin.Clarifying the source suppliers and restoring source-to-sink transport routes are of great significance to the future petroleum and gas undertakings.Previous researchers were largely confined by either limitation of geological records,highly dependence on a singular method or low-precision dating techniques.Our study integrated heavy mineral assemblages,geochemical analyses and detrital zircon U-Pb dating to reconstruct multiple source-to-sink pathways,and to provide a better understanding on the provenance evolution for the upper Pinghu–lower Huagang depositions of the Xihu Depression.At least three major provenances have been confirmed and systematically investigated for their separate compositional features.The Hupijiao Uplift(or even farther northern area)was dominated by a major Paleoproterozoic population peaked at ca.1830 Ma along with minor Mesozoic clusters.The Haijiao Uplift to the west and the Yushan Low Uplift to the southwest,on the other hand,generate opposite U-Pb age spectra with apparently larger peaks of Indosinian and Yanshanian-aged zircons.To be noted,both Indosinian and Paleoproterozoic peaks are almost identical in proportion for the Haijiao Uplift.The overall sedimentary pattern of late Eocene-early Oligocene was featured by both spatial and temporal distinction.The Hupijiao Uplift was likely to cast limited impact during the late Eocene,whereas the broad southern Xihu Depression was transported by a large abundance of materials from the nearby Haijiao and Yushan Low Uplifts.The northern source substantially extended its influence to the farther south during the early Oligocene by delivering plentiful sediments of higher-degree metamorphic parent rocks.Combined with the proximal western and southwestern suppliers,the overall Xihu Depression was under control from both distant and local provenances.

利用加速度响应连续小波变换的时变系统物理参数识别

基于小波理论,推导了函数积分运算的连续小波变换计算方法,应用此方法仅用线性时变结构的振动加速度响应信号,就可计算出速度和位移响应信号的连续小波变换值,并将振动微分方程组转换成用小波表示的线性方程组,求解不同时刻的线性代数方程组识别出时变结构的物理参数(质量、刚度和阻尼)。以5自由度时变结构为仿真算例,利用添加噪声的采集信号,识别了突变、线性变化和周期变化3种不同类型的时变物理参数,算例验证了识别方法的正确性、有效性和抗噪声能力。最后还研究了多尺度分析对参数识别的影响,给出了尺度参数区间选取和离散的依据。

基于加速度响应连续小波变换的线性时变结构瞬时频率识别

推导了函数积分运算的连续小波变换计算方法。借助此法,假设线性时变结构的质量系数为时不变常数,或者其随时间变化的规律已被经验掌握,仅利用线性时变结构自由振动的加速度响应信号,就可以计算出速度响应和位移响应信号的连续小波变换值。将一小段时刻点的线性代数方程组构造成最小二乘问题,求解最小二乘解识别出结构的时变阻尼和时变刚度,从而确定时变结构的瞬时频率。通过对5层剪切梁楼房模型和3自由度密集模态时变结构瞬时频率的识别,验证了识别方法的正确性、有效性和抗噪声能力。

Visualising data distributions with kernel density estimation and reduced chi-squared statistic

The application of frequency distribution statistics to data provides objective means to assess the nature of the data distribution and viability of numerical models that are used to visualize and interpret data.Two commonly used tools are the kernel density estimation and reduced chi-squared statistic used in combination with a weighted mean.Due to the wide applicability of these tools,we present a Java-based computer application called KDX to facilitate the visualization of data and the utilization of these numerical tools.

The dominant driving force for supercontinent breakup: Plume push or subduction retreat?

Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth＇s geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered： the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling（superplume） systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that：（1） at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;（2） an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;（3） the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.

Seismic damage zone and width-throw scaling along the strike-slip faults in the Ordovician carbonates in the Tarim Basin

Understanding the scaling relation of damage zone width with displacement of faults is important for predicting subsurface faulting mechanisms and fluid flow processes. The understanding of this scaling relationship is influenced by the accuracy of the methods and types of data utilized to investigate faults. In this study, seismic reflection data are used to investigate the throw and damage zone width of five strike-slip faults a ecting Ordovician carbonates of the Tarim intracraton basin,NW China. The results indicate that fault slips with a throw less than 200 m had formed wide damage zones up to 3000 m in width. Also, damage zone width is found to have both a positive correlation and a power-law relation with throw of two orders of magnitude, with a ratio of these values varying in a range of 2–15. The relationship between throw and damage zone width is not a simple power-law and changes its slope from small to larger size faults. The results indicate that throw scales well with damage zone width for the studied faults, and hence these can be used to predict fault geometries in the Tarim Basin. The study of the wide carbonate damage zones presented here provides new insights into scaling of large-size faults, which involve multiple faulting stages.

Formation of Hengchun Accretionary Prism Turbidites and Implications for Deep-water Transport Processes in the Northern South China Sea

Located at the end of the northern Manila Trench,the Hengchun Peninsula is the latest exposed part of Taiwan Island,and preserves a complete sequence of accretionary deep-sea turbidite sandstones.Combined with extensive field observations,a’source-to-sink’approach was employed to systematically analyze the formation and evolutionary process of the accretionary prism turbidites on the Hengchun Peninsula.Lying at the base of the Hengchun turbidites are abundant mafic normal oceanic crust gravels with a certain degree of roundness.The gravels with U-Pb ages ranging from 25.4 to23.6 Ma are underlain by hundreds-of-meters thickness of younger deep-sea sandstone turbidites with interbedded gravels.This indicates that large amounts of terrigenous materials from both the’Kontum-Ying-Qiong’River of Indochina and the Pearl River of South China were transported into the deep-water areas of the northern South China Sea during the late Miocene and further eastward in the form of turbidity currents.The turbidity flow drastically eroded and snatched mafic materials from the normal South China Sea oceanic crust along the way,and subsequently unloaded large bodies of basic gravel-bearing sandstones to form turbidites near the northern Manila Trench.With the Philippine Sea Plate drifting clockwise to the northwest,these turbidite successions eventually migrated and,since the Middle Pleistocene,were exposed as an accretionary prism on the Hengchun Peninsula.

Evolution of the Pearl River and its Implication for East Asian Continental Landscape Reversion

As the link connecting the South China Continent and the northern South China Sea(SCS),the Pearl River is the focus of sedimentology and petroleum geology research.Its evolutionary process and controlling factors are of great significance in revealing the East Asian continental landscape reorganization during the Late Cenozoic.Based on published data,’source-to-sink’provenance analyses allow systematic deliberation on the birth and evolutionary history of the Pearl River.Close to the Oligocene/Miocene boundary,an abrupt shift in the sedimentary composition indicates significant westward and northward expansion of the river’s watershed area,followed by the establishment of a near-modern fluvial network.This sedimentary change generally concurred with a series of regional geological events,including the onset of the Yangtze throughflow,large-scale development of the loess plateau,and formation of the northwestern arid zone and Asian Monsoon system.These major changes in the geology-climate-ecoenvironment system are in close response to the process of the Cenozoic Xizang(Tibetan)Plateau uplift.Consequently,the East Asian continental landscape and most of midCenozoic drainage systems underwent critical reversion into east-tilting,or east-flowing networks.

Deconvolving the pre-Himalayan Indian margin-Tales of crustal growth and destruction

The metamorphic core of the Himalaya is composed of Indian cratonic rocks with two distinct crustal affinities that are defined by radiogenic isotopic geochemistry and detrital zircon age spectra. One is derived predominantly from the Paleoproterozoic and Archean rocks of the Indian cratonic interior and is either represented as metamorphosed sedimentary rocks of the Lesser Himalayan Sequence(LHS) or as slices of the distal cratonic margin. The other is the Greater Himalayan Sequence(GHS) whose provenance is less clear and has an enigmatic affinity. Here we present new detrital zircon Hf analyses from LHS and GHS samples spanning over 1000 km along the orogen that respectively show a striking similarity in age spectra and Hf isotope ratios. Within the GHS, the zircon age populations at 2800-2500 Ma,1800 Ma, 1000 Ma and 500 Ma can be ascribed to various Gondwanan source regions; however, a pervasive and dominant Tonianage population(～860-800 Ma) with a variably enriched radiogenic Hf isotope signature(eHf = 10 to-20) has not been identified from Gondwana or peripheral accreted terranes. We suggest this detrital zircon age population was derived from a crustal province that was subsequently removed by tectonic erosion. Substantial geologic evidence exists from previous studies across the Himalaya supporting the Cambro-Ordovician Kurgiakh Orogeny. We propose the tectonic removal of Tonian lithosphere occurred prior to or during this Cambro-Ordovician episode of orogenesis in a similar scenario as is seen in the modern Andean and Indonesian orogenies, wherein tectonic processes have removed significant portions of the continental lithosphere in a relatively short amount of time. This model described herein of the pre-Himalayan northern margin of Greater India highlights the paucity of the geologic record associated with the growth of continental crust. Although the continental crust is the archive of Earth history, it is vital to recognize the ways in which preservation bias and destruction of continental crust informs geologic models.

Crustal reworking and orogenic styles inferred from zircon Hf isotopes:Proterozoic examples from the North Atlantic region

Zircon Hf evolutionary patterns are powerful tools to investiage magma petrogenesis and crustal evolution. The ^(176)Hf/^(177)Hf isotopic signature of a rock is particularly informative and can be used to derive an estimation of the time when mantle extraction and diagnose closed system reworking where successive samples through time define an Hf evolution array dependant on the source Lu/Hf ratio. However, many magmatic events require new mantle addition as the thermal impetus for melting pre-existing crust. In this situation, rather than simply reflecting reworking, the isotopic signature indicates mixing with contributions from both reworked crust and new radiogenic input. Different geodynamic settings have different propensities for either reworking or addition of new mantle-derived magma. Hence, Hf-time trends carry within them a record, albeit cryptic, of the evolving geodynamic environment as different tectonic configurations recycle and add new crust at different rates, magnitudes, and from different sources. As an example of the difference in apparent Hf evolution slopes, we present Hf-time compilations from three geographically distinct Meso-to Neoproterozoic orogenic belts in the North Atlantic Region whose geodynamic configurations remain a subject of debate. We use the εHf/Ma trajectory to assist in understanding their evolution. The εHf/Ma trajectory of the Sveconorwegian Orogen corresponds to a ^(176)Lu/^(177) Hf ratio of 0.012, which implies a process driven primarily by reworking of preexisting crust that is balanced with input from the depleted mantle resulting in a relatively shallowεHf/Ma slope. The Valhalla Orogen reveals a similar comparatively shallow εHf/Ma path. In stark contrast to these patterns is the steep εHf/Ma trajectory of the Grenville Orogen that requires a mixing process involving a greater contribution of old crust of at least ～ 1.8 Ga age. The degree of reworking required to produce the εHf/Ma trend of the Grenville Orogen is consistent with a continent-continent collisional orogeny whereas both Sveconorwegian and Valhalla orogens appear more consistent with accretionary margins.

Decoding earth’s plate tectonic history using sparse geochemical data

Accurately mapping plate boundary types and locations through time is essential for understanding the evolution of the plate-mantle system and the exchange of material between the solid Earth and surface environments.However,the complexity of the Earth system and the cryptic nature of the geological record make it difficult to discriminate tectonic environments through deep time.Here we present a new method for identifying tectonic paleo-environments on Earth through a data mining approach using global geochemical data.We first fingerprint a variety of present-day tectonic environments utilising up to 136 geochemical data attributes in any available combination.A total of 38301 geochemical analyses from basalts aged from 5-0 Ma together with a well-established plate reconstruction model are used to construct a suite of discriminatory models for the first order tectonic environments of subduction and mid-ocean ridge as distinct from intraplate hotspot oceanic environments,identifying 41,35,and 39 key discriminatory geochemical attributes,respectively.After training and validation,our model is applied to a global geochemical database of 1547 basalt samples of unknown tectonic origin aged between 1000-410 Ma,a relatively ill-constrained period of Earth’s evolution following the breakup of the Rodinia supercontinent,producing 56 unique global tectonic environment predictions throughout the Neoproterozoic and Early Paleozoic.Predictions are used to discriminate between three alternative published Rodinia configuration models,identifying the model demonstrating the closest spatio-temporal consistency with the basalt record,and emphasizing the importance of integrating geochemical data into plate reconstructions.Our approach offers an extensible framework for constructing full-plate,deeptime reconstructions capable of assimilating a broad range of geochemical and geological observations,enabling next generation Earth system models.

Thermal evolution of an ancient subduction interface revealed by Lue Hf garnet geochronology, Halilba■? Complex(Anatolia)

The thermal structure of subduction zones exerts a major influence on deep-seated mechanical and chemical processes controlling arc magmatism, seismicity, and global element cycles. Accretionary complexes exposed inland may comprise tectonic blocks with contrasting pressureetemperature(Pe T)histories, making it possible to investigate the dynamics and thermal evolution of former subduction interfaces. With this aim, we present new Lue Hf geochronological results for mafic rocks of the Halilbag?Complex(Anatolia) that evolved along different thermal gradients. Samples include a lawsoniteeepidote blueschist, a lawsoniteeepidote eclogite, and an epidote eclogite(all with counter-clockwise Pe T paths),a prograde lawsonite blueschist with a "hairpin"-type Pe T path, and a garnet amphibolite from the overlying sub-ophiolitic metamorphic sole. Equilibrium phase diagrams suggest that the garnet amphibolite formed at w0.6 -0.7 GPa and 800 -850℃, whereas the prograde lawsonite blueschist records burial from 2.1 GPa and 420℃ to 2.6 GPa and 520℃. Well-defined Lue Hf isochrons were obtained for the epidote eclogite(92.38 ± 0.22 Ma) and the lawsoniteeepidote blueschist(90.19 ± 0.54 Ma),suggesting rapid garnet growth. The lawsoniteeepidote eclogite(87.30 ± 0.39 Ma) and the prograde lawsonite blueschist(ca. 86 Ma) are younger, whereas the garnet amphibolite(104.5 ± 3.5 Ma) is older.Our data reveal a consistent trend of progressively decreasing geothermal gradient from granulite-facies conditions at ~104 Ma to the epidote-eclogite facies around 92 Ma, and the lawsonite blueschist-facies between 90 Ma and 86 Ma. Three Lue Hf garnet dates(between 92 Ma and 87 Ma) weighted toward the growth of post-peak rims(as indicated by Lu distribution in garnet) suggest that the HP/LT rocks were exhumed continuously and not episodically. We infer that HP/LT metamorphic rocks within the Halilbag?Complex were subjected to continuous return flow, with "warm" rocks being exhumed during the tectonic burial of "cold" ones. Our results, combined with regional geological constraints, allow us to speculate that subduction started at a transform fault near a mid-oceanic spreading centre. Following its formation, this ancient subduction interface evolved thermally over more than 15 Myr, most likely as a result of heat dissipation rather than crustal underplating.

Lunar cratering asymmetries with high lunar orbital obliquity and inclination of the Moon

Accurate estimation of cratering asymmetry on the Moon is crucial for understanding Moon evolution history.Early studies of cratering asymmetry have omitted the contributions of high lunar obliquity and inclination.Here,we include lunar obliquity and inclination as new controlling variables to derive the cratering rate spatial variation as a function of longitude and latitude.With examining the influence of lunar obliquity and inclination on the asteroids population encountered by the Moon,we then have derived general formulas of the cratering rate spatial variation based on the crater scaling law.Our formulas with addition of lunar obliquity and inclination can reproduce the lunar cratering rate asymmetry at the current Earth-Moon distance and predict the apex/ant-apex ratio and the pole/equator ratio of this lunar cratering rate to be 1.36 and 0.87,respectively.The apex/ant-apex ratio is decreasing as the obliquity and inclination increasing.Combining with the evolution of lunar obliquity and inclination,our model shows that the apex/ant-apex ratio does not monotonically decrease with Earth-Moon distance and hence the influences of obliquity and inclination are not negligible on evolution of apex/ant-apex ratio.This model is generalizable to other planets and moons,especially for different spin-orbit resonances.

Himalayan Tectonics:Preface

The Himalayan-Tibetan orogen system serves as the modern paradigm for understanding convergence-related processes in orogenic belts. The advancements made studying the region have been applied to other ancient orogenic belts leading not only to a better understanding of their development, but also of secular changes in collisional processes. As more advanced methodologies are introduced and utilized in geological research, the type, scale, and quality of data available enable quantification of geological processes not previously possible. These complex and robust datasets now form the core of many of the research projects undertaken across the Himalaya and continue to provide unprecedented insight into the myriad different aspects of the evolution of the collisional system.

Trial by fire:Testing the paleolongitude of Pangea of competing reference frames with the African LLSVP

Paleogeography can be reconstructed using various crust-or mantle-based reference frames that make fundamentally different assumptions.The various reconstruction models differ significantly in continental paleolongitude,but it has been difficult to assess which models are more valid.We suggest here a "LLSVP test",where an assumed correlation between present-day large low velocity shear-wave provinces and the paleogeography of supercontinent Pangea at breakup ca.200 million years ago can be used to assess the relative accuracy of published reconstructions.Closest correlations between continental paleolongitude and the African LLSVP are achieved with mantle-based reference frames(moving hotspots and true polar wander),whereas shallower crustbased reference frames are shown to be invalid.The relative success of mantle-based frames,and thus the importance of the depth of reference frame,supports the notion that mantle convection is largely vertical compared to the horizontal plate motion of tectonics.

Machine learning and tectonic setting determination:Bridging the gap between Earth scientists and data scientists

Technological progress and the rapid increase in geochemical data often create bottlenecks in many studies,because current methods are designed using limited number of data and cannot handle large datasets.In geoscience,tectonic discrimination illustrates this issue,using geochemical analyses to define tectonic settings when most of the geological record is missing,which is the case for most of the older portion of the Earth’s crust.Basalts are the primary target for tectonic discrimination because they are volcanic rocks found within all tectonic settings,and their chemical compositions can be an effective way to understand tectonics-related mantle processes.However,the classical geochemical discriminant methods have limitations as they are based on a limited number of 2 or 3-dimensional diagrams and need successive and subjective steps that often offers non-unique solutions.Also,weathering,erosion,and orogenic processes can modify the chemical composition of basalts and eliminate or obscure other complementary geotectonic records.To address those limitations,supervised machine learning techniques(a part of artificial intelligence)are being utilized more often as a tool to analyze multidimensional datasets and statistically process data to tackle big data challenges.This contribution starts by reviewing the current state of tectonic discrimination methods using supervised machine learning.Deep learning,especially Convolutional Neural Network(CNN)is the most accurate approach.However,it requires a large dataset and considerable processing time,and the gain of accuracy can be at the expense of interpretability.Therefore,this study designed guidelines for data pre-processing,tectonic setting classification and objectively evaluating the model performance.We also identify research gaps and propose potential directions for the application of supervised machine learning to tectonic discrimination research,aimed at closing the divide between earth scientists and data scientists.

Earth’s tectonic and plate boundary evolution over 1.8 billion years

Understanding the intricate relationships between the solid Earth and its surface systems in deep time necessitates comprehensive full-plate tectonic reconstructions that include evolving plate boundaries and oceanic plates.In particular,a tectonic reconstruction that spans multiple supercontinent cycles is important to understand the long-term evolution of Earth’s interior,surface environments and mineral resources.Here,we present a new full-plate tectonic reconstruction from 1.8 Ga to present that combines and refines three published models:one full-plate tectonic model spanning 1 Ga to present and two continental-drift models focused on the late Paleoproterozoic to Mesoproterozoic eras.Our model is constrained by geological and geophysical data,and presented as a relative plate motion model in a paleomagnetic reference frame.The model encompasses three supercontinents,Nuna(Columbia),Rodinia,and Gondwana/Pangea,and more than two complete supercontinent cycles,covering40%of the Earth’s history.Our refinements to the base models are focused on times before 1.0 Ga,with minor changes for the Neoproterozoic.For times between 1.8 Ga and 1.0 Ga,the root mean square speeds for all plates generally range between 4 cm/yr and 7 cm/yr(despite short-term fast motion around 1.1 Ga),which are kinematically consistent with post-Pangean plate tectonic constraints.The time span of the existence of Nuna is updated to between 1.6 Ga(1.65 Ga in the base model)and 1.46 Ga based on geological and paleomagnetic data.We follow the base models to leave Amazonia/West Africa separate from Nuna(as well as Western Australia,which only collides with the remnants of Nuna after initial break-up),and South China/India separate from Rodinia.Contrary to the concept of a“boring billion”,our model reveals a dynamic geological history between 1.8 Ga and 0.8 Ga,characterized by supercontinent assembly and breakup,and continuous accretion events.The model is publicly accessible,providing a framework for future refinements and facilitating deep time studies of Earth’s system.We suggest that the model can serve as a valuable working hypothesis,laying the groundwork for future hypothesis testing.

The position of Cathaysia in Nuna and during the Nuna-Rodinia transition

The assembly and breakup of Nuna and Rodinia, two successive supercontinents in the Proterozoic, provide key evidence for the establishment of supercontinent cycles. Reliable palaeogeographic reconstructions at the cores of the two supercontinents are critical for understanding the evolution and geodynamics of the supercontinent cycles. In addition, there are fundamental aspects of the Nuna-Rodinia transition that remain poorly understood, including the ways in which Nuna broke up and Rodinia assembled, either through introversion [1] or extroversion [2].