Correction:The escape mechanisms of the proto-atmosphere on terrestrial planets:“boil-off”escape,hydrodynamic escape and impact erosion

In the original publication of the article,the affiliation“College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing,People’s Republic of China”for author Ziqi Wang was missing and included in this correction article.

Early Silurian Wuchuan–Sihui–Shaoguan exhalative sedimentary pyrite belt, South China: constraints from zircon dating for K-bentonite of the giant Dajiangping deposit

The Wuchuan-Sihui-Shaoguan(WSS)exhalative sedimentary pyrite belt in the southwestern part of the Qinzhou-Hangzhou(Qin-Hang)belt is the most important sulfur industry base in China.However,a wide range of metallogenetic ages spanning from Ediacaran to Devonian has been reported in the literature.This age range does not support the idea that the typical character of"coeval mineralization"in an exhalative sedimentary mineralization belt in China and worldwide.Therefore,the precise determination of mineralization ages of representative deposits is necessary to provide guides for exploration and metallogenetic models.The Dajiangping pyrite deposit is a typical example of this kind of deposits and is also the largest deposit with a proven reserve of 210 Mt.This deposit was thought to have formed in Ediacaran or Devonian.In this study,2-3 layers of 10-25 cm thick 2M1-type microcrystalline muscovite slate abruptly embedded in the No.Ⅳmassive orebody of the deposit has been identified to be low-grade metamorphic K-bentonite.A Concordia zircon LA-ICP-MS U-Pb age of 432.5±1.3 Ma(mean standard weighted deviation of concordance and equivalence=1.2;N=11)has been yielded for the low-grade metamorphic K-bentonite.This age is distinctly different from the Rb-Sr isochron age of630.1±7.3 Ma for siliceous rock at the top of the No.Ⅲbanded orebody and the Re-Os isochron age of 389±62 Ma for pyrites from a laminated orebody.Instead,it is close to the intercept age(429 Ma)of the youngest detrital zircons from sandstone interlayers of the No.Ⅲbanded orebody.The Concordia age is also coincident with those of the Late Caledonian(400-460 Ma)magmatism-metamorphism events which are widely distributed in Cathaysia Block.Particularly,it agrees well with that of the Early Silurian extensional volcanism(434-444 Ma)which have been revealed in the Dabaoshan,Siqian-Hekou,and Nanjing volcanic basins in northern Guangdong Province and southern Jiangxi Province.Hence,the dating result in this study confirms that the sedimentary time of the ore-host Daganshan Formation is Early Silurian,and implies that the mineralization age of the Dajiangping pyrite deposit should also be Early Silurian.In combination with the Early Silurian age of Shezui pyrite deposit and the Dabaoshan volcanic basin along the WSS pyrite belt,it could be inferred that the WSS pyrite belt provides a record of the northern expanding of Qinzhou-Fangcheng trough in Early Silurian and that the exhalative pyrite mineralization was triggered by the postcollisional extension of the margin of Cathaysia Block after the intracontinental collision between Cathaysia Block and Yangtze Block during Late Caledonian stage.

A model of crust-mantle differentiation for the early Earth

The Archean continents,primarily composed of the felsic tonalite-trondhjemite-granodiorite(TTG)suite,were formed or conserved since~3.8 Ga,with significant growth of the continental crust since~2.7 Ga.The difficulty in direct differentiation of the felsic crustal components from Earth’s mantle peridotite leads to a requirement for the presence of a large amount of hydrated mafic precursor of TTG in Earth’s proto-crust,the origin of which,however,remains elusive.The mafic proto-crust may have formed as early as~4.4 Ga ago as reflected by the Hf and Nd isotopic signals from Earth’s oldest geological records.Such a significant time lag between the formation of the mafic proto-crust and the occurrence of felsic continental crust is not reconciled with a single-stage scenario of Earth’s early differentiation.Here,inspired by the volcanism-dominated heat-pipe tectonics witnessed on Jupiter’s moon Io and the resemblances of the intensive internal heating and active magmatism between the early Earth and the present-day Io,we present a conceptual model of Earth’s early crust-mantle differentiation,which involves an Io-like scenario of efficient extraction of a mafic proto-crust from the early mantle,followed by an intrusion-dominating regime that could account for the subsequent formation of the felsic continents as Earth cools.The model thus allows an early formation of the preTTG proto-crust and the generation of TTG in the continent by providing the favorable conditions for its subsequent melting.This model is consistent with the observed early fractionation of the Earth and the late but rapid formation and/or accumulation of the felsic components in the Archean continents,thus sheds new light on the early Earth’s differentiation and tectonic evolution.

How to estimate isotope fractionations of a Rayleigh-like but diffusion-limited disequilibrium process?

The Rayleigh distillation isotope fractionation(RDIF) model is one of the most popular methods used in isotope geochemistry. Numerous isotope signals observed in geologic processes have been interpreted with this model. The RDIF model provides a simple mathematic solution for the reservoir-limited equilibrium isotope fractionation effect. Due to the reservoir effect, tremendously large isotope fractionations will always be produced if the reservoir is close to being depleted. However, in real situations, many prerequisites assumed in the RDIF model are often difficult to meet. For instance, it requires the relocated materials, which are removed step by step from one reservoir to another with different isotope compositions(i.e., with isotope fractionation), to be isotopically equilibrated with materials in the first reservoir simultaneously. This ‘‘quick equilibrium requirement’’ is indeed hard to meet if the first reservoir is sufficiently large or the removal step is fast. The whole first reservoir will often fail to re-attain equilibrium in time before the next removal starts.This problem led the RDIF model to fail to interpret isotope signals of many real situations. Here a diffusion-coupled and Rayleigh-like(i.e., reservoir-effect included) separation process is chosen to investigate this problem. We find that the final isotope fractionations are controlled by both the diffusion process and the reservoir effects via the disequilibrium separation process. Due to its complexity, we choose to use a numerical simulation method to solve this problem by developing specific computing codes for the working model.According to our simulation results, the classical RDIF model only governs isotope fractionations correctly at the final stages of separation when the reservoir scale(or thickness of the system) is reduced to the order of magnitude of the quotient of the diffusivity and the separation rate. The RDIF model fails in other situations and the isotope fractionations will be diffusion-limited when the reservoir is relatively large, or the separation rate is fast. We find that the effect of internal isotope distribution inhomogeneity caused by diffusion on the Rayleigh-like separation process is significant and cannot be ignored. This method can be applied to study numerous geologic and planetary processes involving diffusion-limited disequilibrium separation processes including partial melting,evaporation, mineral precipitation, core segregation, etc.Importantly, we find that far more information can be extracted through analyzing isotopic signals of such ‘‘disequilibrium’’processes than those of fully equilibrated ones, e.g., reservoir size and the separation rate. Such information may provide a key to correctly interpreting many isotope signals observed from geochemical and cosmochemical processes.

A review of GEMC method and its improved algorithms

Gibbs Ensemble Monte Carlo(GEMC)is a molecular simulation method commonly used for simulating phase equilibrium.This method has been proposed since 1987 and applied in many fields,such as geology,planetary science,chemical engineering,material science,etc.GEMC method combines canonical(NVT),isobaricisothermal(NPT),and grand canonical(μVT)Monte Carlo techniques in a single simulation.The GEMC method was developed on the fundamental law of phase equilibrium that chemical potentials of each phase all equal.Two key factors affect the rationality and reliability of GEMC simulations:1.particles can be efficiently moved in/out from certain phase during simulation;2.samplings can represent the whole system well,in other words,samplings hold good ergodicity.In addition,various parallel methods have been developed to improve the simulation efficiency.In this review,an introduction to the theoretical fundamentals,improvements on particle movement and sampling protocols,acceleration techniques and some applications of the GEMC method will be presented.This is the first integrated review introducing the fundamentals,improvements and applications of the GEMC simulation method.

Equilibrium mercury and lead isotope fractionation caused by nuclear volume effects in crystals

To investigate equilibrium mercury(Hg)and lead(Pb)isotope fractionation caused by the nuclear volume effect(NVE)in crystals,the electron densities at nuclei(i.e.,|Ψ(0)|2)for Hg-or Pb-bearing crystalline compounds were investigated by using the relativistic spin orbit zeroth-order regular approximation(ZORA)method with a three-dimensional periodic boundary condition based on the density functional theory(DFT).Many isotope fractionation factors of crystalline compounds are provided for the first time.Our results show,even at1000℃,NVE-driven Hg and Pb isotope fractionation are meaningfully large,i.e.,range from 0.12‰to 0.49‰(202Hg/^(198)Hg),from-0.20‰to 0.17‰(208Pb/^(206)Pb)and from-0.08‰to 0.06‰(207Pb/^(206) Pb)relative to Hg0 vapor and Pb0 vapor,respectively.Specifically,the fractionations range from-0.06‰to-0.20‰(208Pb/^(206)Pb)and from-0.02‰to-0.08‰(207Pb/^(206)Pb)for Pb2+-bearing species,from 0.10‰to 0.17‰(208Pb/^(206)Pb)and from 0.04‰to 0.06‰(207Pb/^(206)Pb)for Pb4+-bearing species in crystals.All calculated Hg-bearing species in crystals will enrich heavier isotope(202Hg)relative to Hg0 vapor.Meanwhile,Pb4+-bearing species enrich heavier Pb isotopes(208Pb and 207Pb)than Pb^(2+)-bearing species in crystals,which the enrichment can be up to 0.37‰(208-Pb/^(206)Pb)and 0.14‰(207Pb/^(206)Pb)at 1000℃,due to their NVEs are in opposite directions.The NVE-driven MIFs of Hg isotopes,which are compared to the Hg202-Hg198baseline,are up to-0.158‰(ΔNV199Hg),-0.024‰(ΔNV200Hg)and-0.094‰(ΔNV201Hg)relative to Hg0 vapor at5000 C.For all studied Hg-bearing species in crystals,the MIFs of two odd-mass isotopes(i.e.,ΔNV199Hg andΔNV201Hg)will be changed proportionally and their ratio(i.e.,ΔNV199Hg/ΔNV201Hg)will be a constant 1.67.The NVE can also cause mass-independent fractionations for 207Pb and 204 Pb compared to the baseline of 208Pb and 206Pb.The largest NVEdriven MIFs are 0.043‰(ΔNV207Pb)and-0.040‰(ΔNV204Pb)among all the studied species relative to Pb0 vapor at 5000 C.The magnitudes of odd-mass isotope MIF(ΔNV207Pb)and even-mass isotope MIF(ΔNV204Pb)are almost the same but with opposite signs,leading to the MIF ratio of them(i.e.,ΔNV207Pb/ΔNV204Pb)is-1.08.

Origin of ULVZs near the African LLSVP: Implications from their distribution and characteristics

Ultra-low velocity zones(ULVZs)provide important information on the composition and dynamics of the core-mantle boundary(CMB).However,their global distribution and characteristics are not well constrained,especially near African large low-shear velocity provinces(LLSVPs).Here,we used ScS precursor(SdS)and postcursor(ScscS)phases recorded by various seismic networks in Africa and South America to investigate the ULVZ characteristics underlying the South Atlantic Ocean.We found no evidence of ULVZs near the SE boundary of South America,but an ULVZ was found within the SW boundary of the African LLSVP,with thicknesses ranging from 11–18 km and reductions in S-wave velocities of 18%–34%.Our results,combined with the global distribution of ULVZs,suggest that thermal activity may be essential to ULVZ formation.Moreover,subducted slab and mantle flow may also play a key role,depending on the location of the ULVZs.

Late veneer and the origins of volatiles of Earth

Late veneer is an important paradigm in early Earth and planetary studies.It refers to the late addition of extraterrestrial materials to the Earth’s mantle after the core formation,which leads to the overabundances of highly siderophile elements in the primitive upper mantle.In this review,the origin,evolution,and expansion of the late veneer hypothesis are summarized,including some unresolved problems.I hope this review would be helpful for the new entrants to this field.

The escape mechanisms of the proto-atmosphere on terrestrial planets:"boil-off" escape,hydrodynamic escape and impact erosion

Atmospheric escape is an essential process that affects the evolution of the proto-atmosphere.The atmospheric escape of early terrestrial planets was extremely rapid compared with the current scenarios,and the main atmospheric escape modes were also quite different.During the dissipation of the nebula disk,the primordial atmosphere experienced a brief but violent"boiling"escape,in which most of the primordial atmosphere was lost.After the nebula disk dissipates,hydrodynamic escape and impact erosion are the two most important mass-loss mechanisms for the proto-atmosphere.Hydrodynamic escape is a rapid atmospheric escape process caused by strong solar radiation,while impact erosion refers to the process in which small-large or giant impacts erode the proto-atmosphere.In the early solar system,there were other escape mechanisms,such as non-thermodynamic escape and Jeans escape,but it is generally believed that these mechanisms have relatively little impact.Here we systematically introduce the above-mentioned atmospheric escape mechanisms and then make some suggestions for the existing problems and future research for atmospheric escape models.

^(182)W anomalies in mantle:a brief review

With significant advances in mass spectrometry for isotope analysis in the last decade,e.g.,negative thermal ionization mass spectrometry and multi-collector inductively coupled plasma mass spectrometry,high-precision(ppm-level)measurements of tungsten(W)isotopes have been widely used for early earth differentiation processes,such as metal-silicate segregation,melting and crystallization processes during the magma ocean,and putative core-mantle exchange and dynamics.Here,we give a brief review of works on ^(182)W anomalies in terrestrial samples,including methods,results,explanations,implications,and prospects.The review will be presented by including the following parts:the introduction of W isotopes and the short-lived radioactive ^(182)Hf-^(182)W system;data notations and W isotope measurement methods;^(182)W anomalies observed in terrestrial samples;a summary of models developed for interpreting origins of positive and negative ^(182)W anomalies;future prospects.

Preface:the early stage of the early Earth study in China

This special issue is originated from two successive failures of our application of the major project of the National Natural Science Foundation of China(NSFC)under the discipline category of“Early Earth Evolution”.In the end,this major project was awarded to a research proposal titled“Early shale oil evolution”,and by that the NSFC closed the funding category“Early Earth Evolution”.

Electrical and thermal conductivity of Earth's core and its thermal evolution——A review

The Earth’s core is composed of iron,nickel,and a small amount of light elements(e.g.,Si,S,O,C,N,H and P).The thermal conductivities of these components dominate the adiabatic heat flow in the core,which is highly correlated to geodynamo.Here we review a large number of studies on the electrical and thermal conductivity of iron and iron alloys and discuss their implications on the thermal evolution of the Earth’s core.In summary,we suggest that the Wiedemann-Franz law,commonly used to convert the electrical resistivity to thermal conductivity for metals and alloys,should be cautiously applied under extremely high pressure-temperature(P-T)conditions(e.g.,Earth’s core)because the Lorentz number may be P-T dependent.To date,the discrepancy in the thermal conductivity of iron and iron alloys remains between those from the resistivity measurements and the thermal diffusivity modeling,where the former is systematically larger.Recent studies reconcile the electrical resistivity by first-principles calculation and direct measurements,and this is a good start in resolving this discrepancy.Due to an overall higher thermal conductivity than previously thought,the inner core age is presently constrained at~1.0 Ga.However,light elements in the core would likely lower the thermal conductivity and prolong the crystallization of the inner core.Meanwhile,whether thermal convection can power the dynamo before the inner core formation depends on the amounts of the proper light elements in the core.More works are needed to establish the thermal evolution model of the core.

The core-merging giant impact in Earth's accretion history and its implications

The Earth’s accretion process is accompanied by a large number of collisions.It is widely accepted that collisions dominate the Earth’s late accretion stage.Among all these collisions,there is a special type of collision called Core-merging giant impact(CMGI),in which much or most the impactor’s core merges directly with the protoEarth’s core.This core-merging scenario plays an important role in the Earth’s accretion process and deeply affects the formation of the Earth’s core and mantle.However,because CMGI is a small probability event,it has not been fully studied.Here we use the SPH method to comprehensively study all possible CMGIs in the Earth’s accretion history.We find that CMGI only occurs in the initial conditions with small impact angle,small impact velocity and big impactor.We further discuss the implications of CMGI.We are confident that CMGI inevitably causes the chemical disequilibrium of the Earth’s core and mantle.The CMGI process also brings many light elements into the Earth’s core.In particular,if the Moon-forming giant impact is a CMGI,then CMGI can also explain the abnormal content of HSEs in the Earth’s current mantle.

ε-FeOOH在中下地幔储存的证据及其对水循环的意义

地球内部转换带与核幔边界的水对地球的分层、元素循环以及地核组成等方面都有十分重要的影响.如果水是在地球表面与内部圈层间循环的话,那么理论上在下地幔也应该有水的通道,而且该水通道的地震地磁学特征应有别于其周围的下地幔环境.在本次工作中,利用动静高压结合的方法(二级轻气炮+金刚石压腔)并综合理论计算系统研究了ε-FeOOH在下地幔温压范围内的波速与电导率剖面及其内部机制.我们发现,在50 GPa左右由于铁的电子自旋相变的影响,ε-FeOOH的电导率有3个数量级的急剧升高而其纵波波速会突然下降16.8%左右.结合全球地震地磁学数据分析,ε-FeOOH在这个压力范围的高导低波现象恰好与全球范围内在1200 km深度左右的某些高导低波的冷俯冲带区域相吻合.含水ε-FeOOH或者其他含铁相可能具有的这些独特性质或许可以作为水在中下地幔通过的证据.