A planetary perspective on Earth's space environment evolution

The planet Earth is an integrated system, in which its multi-spheres are coupled, from the space to the inner core. Whether the space environment in short to long terms has been controlled by the earth's interior process is contentious. In the past several decades,space weather and space climate have been extensively studied based on either observation data measured directly by man-made instruments or ancient data inferred indirectly from some historical medium of past thousands of years. The acquired knowledge greatly helps us to understand the dynamic processes in the space environment of modern Earth, which has a strong magnetic dipole and an oxygen-rich atmosphere. However, no data is available for ancient space weather and climate(>5 ka). Here, we propose to take the advantage of " space-diversity" to build a " generalized planetary space family", to reconcile the ancient space environment evolution of planet Earth from modern observations of other planets in our solar system. Such a method could also in turn give us a valuable insight into other planets' evolution.

Multi-spherical interactions and mechanisms of hydrocarbon enrichment in the Southeast Asian archipelagic tectonic system

Global cooling began since 50 Ma,but a warm climate was maintained in the archipelagic tectonic system in Southeast Asia where a wealth of Cenozoic oil and gas resources was formed and preserved.From the perspective of Earth system,this study analyzes Cenozoic tectonic activities,climatic and environmental evolution,and petroleum enrichment in Southeast Asia,and provides the following insights:(1)Subduction of oceanic plates and the extension of overlying continental lithosphere resulted in widespread volcanic eruptions as well as the formation of rift basins and shallow marine shelves,leading to complex interactions between deep tectonic processes and Earth’s surface including mountains,basins,and seas.(2)Microcontinental accretion and prolonged stay in equatorial low-latitude regions have changed trade winds into monsoons,altered ocean current pathways and flow rates,and profoundly affected rainfall and climate.(3)The archipelagic tectonic system,coupled with a hot and rainy climate,fostered tropical rainforests,mangroves,and phytoplankton,providing abundant organic matter and promoting the development of petroleum resources.(4)Combinations of rift basin development and marine transgression and regression led to an effective superposition of source-reservoir-seal combinations from multiplepetroleum systems.Rapid deep burial of organic matter and high geothermal gradients facilitated the generation and large-scale accumulation of oil and gas.(5)Multi-spherical(such as atmosphere,biosphere,hydrosphere and lithosphere)interactions on the Earth,which resulted from the convergence of multiple tectonic plates,are believed as the primary driver for exceptional enrichments of Cenozoic oil and gas resources in Southeast Asia.These understandings are significant for developing theories of oil and gas enrichment under the guidance of Earth System Science.In order to continue making significant oil and gas exploration discoveries in the deep-layers,deep-waters,and unconventional oil and gas fields of Southeast Asia,attention should be paid to the oil and gas resource effects of the collision between Australia and Sunda blocks and the high-temperature and high-rainfall climate environment,and efforts should be made to develop economic development and CO_(2)sequestration technologies for offshore CO_(2)-rich gas fields.

The genesis and resource potential of gold deposits in the Liaodong Peninsula

Plenty of gold deposits related to Late Mesozoic craton destruction are widely distributed in eastern North China Craton. However, significant differences in research degrees, ore-forming characteristics, and proven reserves exist among different regions in the North China Craton. The Liaodong Peninsula has similar regional geological characteristics to those of the Jiaodong Peninsula, with both experiencing craton destruction during Late Mesozoic, but the two areas have substantial differences in terms of gold mineralization and the proven gold resources. Based on regional geology, Mesozoic magmatictectonic evolution and ore geology, combined with integrated geophysical exploration and big data AI resource prediction, in this paper, we propose that the ore-forming materials of Late Mesozoic gold deposits in Liaodong were mainly originated from mantle-derived melts and/or fluids induced by craton destruction. The gold deposits were primarily controlled by NE-NNEtrending faults, mainly classified as fracture-controlled altered rock-type and sulfide-bearing quartz vein-type. Moreover, our study predicts that the Yalu River fault zone and its related secondary faults, as well as the periphery and deeper parts of known goldfields, are the important regions for future gold resource exploration. The Yalu River metallogenic belt has an enormous potential for gold resources, and the Liaodong Peninsula has a potential to add thousands of tons of gold resources.

Erratum to:Geodynamic processes of the southeastern Neo-Tethys Ocean and the formation mechanism of the curved subduction system in Southeast Asia

The research paper"Geodynamic processes of the southeastern Neo-Tethys Ocean and the formation mechanism of the curved subduction system in Southeast Asia"(Sci China Earth Sci,2023,66:703-717)contained errors.The corrections in an erratum do not change or affect the result or conclusion of the paper.

新特提斯单向俯冲的动力学机制

新特提斯洋向北单向俯冲的机制涉及两个核心问题,分别是南侧冈瓦纳被动大陆的不断裂解和拼贴到欧亚大陆南缘陆块诱发的俯冲起始.本文统计了大火成岩省的分布规律,发现200~80 Ma期间,与地幔柱相关的大火成岩省主要分布于南半球,暗示该时期南半球地幔温度高于北半球地幔温度.在南北半球地幔温差和地幔柱/大火成岩省作用下,引起上覆岩石圈抬升、破裂,结合新特提斯洋的北向俯冲,共同诱发冈瓦纳大陆的多期裂解.由于南北半球地幔温差会造成地幔柱头岩浆向北扩散并与新特提斯洋中脊发生相互作用,在特殊情况下,会引发原来大洋中脊的堵塞和跃迁,形成新的洋中脊,促进了陆块不断向北漂移.在古特提斯洋闭合后洋壳持续俯冲引发的应力作用下,欧亚大陆南缘具有高含水特性的洋陆过渡带率先破裂并产生向北的俯冲起始.驱动新特提斯大洋岩石圈持续向北俯冲的动力,除俯冲板片的拖曳力/重力外,还应该包含南半球高地幔温度和洋中脊产生的向北推力.

Geodynamic processes of the southeastern Neo-Tethys Ocean and the formation mechanism of the curved subduction system in Southeast Asia

Southeast Asia is located at the intersection of the Tethys and Pacific domains. The superimposed effects of the two tectonic domains have resulted in complicated deep structure, surface magma responses, and dynamic processes of Southeast Asia. Based on the latest long-term passive seismic experiment and numerical modeling, this study reconstructs the dynamic processes of the closure of the Neo-Tethys Ocean and the formation of the curved subduction system in Southeast Asia since the Late Mesozoic. P-wave velocity structure shows a remnant of the Neo-Tethys subducted slab in the lower mantle beneath Southeast Asia at a depth of approximately 1500 km. On the Java-East Timor subduction zone, the remnant slab is coupled with the Indo-Australian subducting slab in the upper mantle with the same direction, while on the Sumatra subduction zone, the remnant slab is decoupled from the Indo-Australian subducting slab in different directions. The formation of the curved subduction system in Southeast Asia is resulted from the northward subdcutions of previous Neo-Tethys and current IndoAustralian Plate, and the westward subduction of the Pacific Plate since Mesozoic. The former is characterized by continuous subduction and subsequent continental block collision, forming the current continental lithosphere in Southeast Asia and the curve-shaped Sumatra-Java subduction zone;the latter is characterized by subduction retreat and back-arc spreading, forming the eastern Philippine subduction zone and a series of marginal sea basins. Since the Early Cretaceous, the opening of the North Australian Sea resulted in stagnation of the Australian Block in the high latitude area of the southern hemisphere for a long time.The North Australian Sea was dominated by out-dipping double subduction from 45 Ma, which resulted in rapid northward drifting of the Australian Block and final collision with the Sundaland.

The influence of Tethyan evolution on changes of the Earth's past environment

Understanding changes in Earth's past can provide valuable insights into prediction of its future.An example is the interactions between the internal and external spheres of Earth.The cyclical northward breakup-drift of Gondwana,driven by the opening and closure of Proto-,Paleo-,and Neo-Tethyan oceans,facilitated the transfer of landmasses from the southern to the northern hemisphere,traversing the tropic region.We have observed a compelling correlation between episodic increases in landmass area within the tropic regions(those lying at less than 20°latitude)and a subsequent temperature decrease during the three major glacial periods in the last 500 million years.This phenomenon can be attributed to low latitude regions receiving more solar energy influx on Earth's surface than high latitude areas.In addition,an increase of landmass in tropic regions(low latitude)attenuates the net energy absorption by the Earth's surface,consequently impeding the conduction and convection of absorbed energy toward the poles.The result is a decrease in global surface temperature.The tropic regions,benefiting from abundant sunlight,create an ideal environment for the proliferation of marine plankton species.These species are important in the generation of organic-rich sediment.Massive biological debris is therefore deposited on continental margins when a continent drifts across the tropic region.This creates favorable conditions for future hydrocarbon and reservoir formation.Northward subduction of organic-rich sediments during the closure of the Tethyan oceans results in the generation of mafic arc magmas with low oxygen fugacity.This chemical environment helps the mineralization of reduced-type ore deposits such as tungsten,tin,and lithium.Subducted-driven plate tectonics in the Tethys realm changes the distribution of oceans and landmass,subsequently affecting the balance and distribution of solar energy across Earth's surface.These changes trigger consequential environmental shifts which in turn,impact the composition of rock and mineral along the Eurasian margin due to subduction.Consequently,the Tethyan realm and its history is an ideal natural laboratory for comprehending the processes and changes of the entire Earth's system.

Dynamic modeling of tectonic carbon processes:State of the art and conceptual workflow

Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time provides solid restrictions and standards for testing tectonic carbon processes against global measurements.Despite this,modeling the causal relationship between tectonic events and atmospheric CO_(2)levels remains a challenge.We examine the current state of the global tectonic CO_(2)research and suggest a conceptual workflow for numerical experiments that integrates plate tectonics and deep carbon dynamics.Future tectonic carbon cycle modeling should include at least four modules:(1)simulation of carbon-carrying processes,such as carbon ingassing and outgassing at the scale of minerals;(2)calculation of CO_(2)fluxes in tectonic settings like subduction,mantle plume,and plate rifting;(3)reconstruction of carbon cycling within the plates-scale tectonic scenario,particularly involving the processes of supercontinent convergence and dispersion;and(4)comparison with atmospheric CO_(2)history data and iterations,aiming to find the coincidental link between different tectonic carbon fluxes and climate changes.According to our analysis,the recent advancements in each of the four modules have paved the path for a more general assembly.We envision that the large variety of carbon transportation parameters across more than ten orders of magnitude in both time and space is the primary technical hurdle in simulating tectonic carbon dynamics.We propose a boundary-condition-connected approach for simulating the global carbon cycle to realize carbon exchange between the solid earth and surface spheres.

宜居地球的过去、现在与未来——地球科学发展战略概要

人类对地球和生命起源的好奇心与探索精神促使近代科学的启蒙,从古希腊到文艺复兴,再到工业革命,始终如此.回顾20世纪地球科学发展史,板块构造理论揭示了行星地球的动力学特征,引发了20世纪的地学革命,极大地改变了人类对地球演化历史的认知[1,2].面对第四次工业革命的前夜,地球科学前沿问题究竟是什么?近年来天文学与深空探测将"宜居性:适宜生命存在的空间"作为首要研究目标.

华北克拉通破坏对地表地质与陆地生物的影响

晚中生代古太平洋板块俯冲导致东亚古大地幔楔形成和华北克拉通破坏,该动力过程引发华北克拉通发生强烈伸展和岩浆活动,广泛形成裂谷盆地和变质核杂岩,并造成燕辽和热河生物群的繁盛与消亡.古太平洋板块俯冲角度的变化导致东亚大陆经历了三次短暂挤压事件和两次强烈伸展构造.多学科综合研究进一步揭示,晚中生代燕辽和热河生物群的演化与华北克拉通的破坏强度、岩浆活动强弱以及盆地发展存在明显的时空相关性.上述现象表明地球深部动力过程不仅控制了克拉通破坏和地壳构造演化,而且也极大地影响了地表环境的变迁和陆地生态系统的演变.因此,地球生命是与环境协同演化,并且共同受地球深部过程的控制.

The subduction of the west Pacific plate and the destruction of the North China Craton

While a general concensus has recently been reached as to the causal relationship between the subduction of the west Pacific plate and the destruction of the North China Craton, a number of important questions remain to answer, including the initial subduction of west Pacific plate beneath the eastern Asian continent, the position of west Pacific subduction zone during the peak period of decratonization(i.e., Early Cretaceous), the formation age of the big mantle wedge under eastern Asia, and the fate of the subducted Pacific slab. Integration of available data suggests that the subduction of the western Pacific plate was initiated as early as Early Jurrasic and the subduction zone was situated to 2,200 km west of the present-day trench in the Early Creataceous, as a result of eastward migration of the Asian continent over a distance of ca. 900 km since the Early Cretaceous.The retreat of the subducting west Pacific plate started ~145 Ma ago, corresponding to the initial formation of the big mantle wedge system in the Early Cretaceous. The subduction of the Pacific slab excerted severe influence on the North China Craton most likely through material and energy echange between the big mantle wedge and overlying cratonic lithosphere. The evolution history of the west Pacific plate was reconstructed based on tectonic events. This allows to propose that the causes of phases A and B for the Yanshanian orogeny were respectively related to rapid low-angle subduction and to lowering subduction angle of the west Pacific plate. At ca. 130–120 Ma, the subduction of the west Pacific plate was characterized by increasing subducting angle, slab rollback and rapid trench retreat, leading to the final stagnation of the subducting slab within the mantle transition zone. This process may have significantly affected the physical property and viscosity of the mantle wedge above the stagnant slab, resulting in non-steady mantle flows. The ingression of slab-released melts/fluids would significantly lower the viscosity of the mantle wedge and overlying lithosphere, inducing decratonization. This study yields important bearings on the relationship between the subduction of the west Pacific plate and the evolution of the lithospheric mantle beneath the North China Craton.

Cyclical one-way continental rupture-drift in the Tethyan evolution: Subduction-driven plate tectonics

Numerous continents have rifted and drifted away from Gondwana to repeatedly open ocean basins over the past-500 millionyears.These Gondwana-derived continents drifted towards and collided with components of the Eurasian continent to successively close the preexisting oceans between the two.Plate tectonics satisfactorily describes the continental drift from Gondwana to Eurasia but does not define the geodynamic mechanism of continuously rifting to collisions of continents in the Tethy an Realm.After reappraisal of geological records of the rift,collision and subduction initiation from the surface and various geophysical observations from depth,we propose that Eurasia-directed subducting oceanic slabs would have driven Tethyan system in the Phanerozoic.The Eurasia-directed subduction would have dragged the passive Gondwana margin to rift and drift northwards,giving birth to new oceans since the Paleozoic.The closure of preexisting oceans between the Gondwana-derived continents and Eurasia led to continental collisions,which would have induced the initiation of oceanic subduction in the Tethyan Realm.Multiple episodic switches between collision-subduction-rift repeatedly led to the separation of continental fragments from Gondwana and dragged them to drift towards Eurasia.The final disappearance of Neo-Tethy s would have induced collision of the Gondwana-derived continents with the Eurasian continent,giving rise to the Cenozoic Alpine-Zagros-Himalayan collisional system.Therefore,the Eurasia-directed oceanic subduction would have acted as a’one-way train’that successively transferred the ruptured Gondwana continental fragments in the south,into the terminal in the north.In this regard,the engine of this"Tethyan one-way train"is the negative buoyancy of subducting oceanic slabs.

SIMS U-Pb zircon age of a tuff layer in the Meishucun section, Yunnan, southwest China: Constraint on the age of the Precambrian-Cambrian boundary

Determination of the age of the Precambrian-Cambrian boundary is critical in understanding early evolution of life on Earth. SIMS U-Pb zircon analyses of the Bed 5 tuff layer of the Meishucun section were carried out closely following the guidance of cathodoluminescence images, and the majority of analyses were conducted on the oscillatory zircon grains. Thirteen measurements yield a highly reliable Concordia U-Pb age of 536.7 ± 3.9 Ma for the Bed 5 horizon. A grand mean of 206Pb/238U age of 535.2± 1.7 Ma (MSWD = 0.53) is calculated based on 13 concordant SIMS measurements of this study and 4 nano-SIMS measurements of Sawaki et al., which is the best estimate of the deposition age of the tuff layer within Bed 5 in the Meishucun section. This age has provided a robust age constraint on the significant Precambrian-Cambrian boundary strata in southern China, which independently suggested the placement of the Precambrian-Cambrian boundary at the bottom of the Xiaowaitoushan Member (Marker A).

Tectonic evolution and geodynamics of the Neo-Tethys Ocean

The Neo-Tethys Ocean was an eastward-gaping triangular oceanic embayment between Laurasia to the north and Gondwana to the south.The Neo-Tethys Ocean was initiated from the Early Permian with mircoblocks rifted from the northern margin of Gondwana.As the microblocks drifted northwards,the Neo-Tethys Ocean was expanded.Most of these microblocks collided with the Eurasia continent in the Late Triassic,leading to the final closure of the Paleo-Tethys Ocean,followed by oceanic subduction of the Neo-Tethys oceanic slab beneath the newly formed southern margin of the Eurasia continent.As the splitting of Gondwana continued,African-Arabian,Indian and Australian continents were separated from Gondwana and moved northwards at different rates.Collision of these blocks with the Eurasia continent occurred at different time during the Cenozoic,resulting in the closure of the Neo-Tethys Ocean and building of the most significant Alps-Zagros-Himalaya orogenic belt on Earth.The tectonic evolution of the Neo-Tethys Ocean shows different characteristics from west to east:Multi-oceanic basins expansion,bidirectional subduction and microblocks collision dominate in the Mediterranean region;northward oceanic subduction and diachronous continental collision along the Zagros suture occur in the Middle East;the Tibet and Southeast Asia are characterized by multi-block riftings from Gondwana and multi-stage collisions with the Eurasia continent.The negative buoyancy of subducting oceanic slabs can be considered as the main engine for northward drifting of Gondwana-derived blocks and subduction of the Neo-Tethys Ocean.Meanwhile,mantle convection and counterclockwise rotation of Gondwana-derived blocks and the Gondwana continent around an Euler pole in West Africa in non-free boundary conditions also controlled the evolution of the Neo-Tethys Ocean.

Quaternary integrative stratigraphy and timescale of China

Quaternary strata in China mainly comprise continental deposits in a variety of depositional settings. The continental Quaternary in temperate northern China consists mainly of eolian and fluvio-lacustrine deposits; that in subtropical southern China, mainly of vermiculated red soils, cave/fissure deposits, and fluvio-lacustrine deposits; and that in the alpine Tibetan Plateau, mainly of fluvio-lacustrine and piedmont deposits. The marine Quaternary in China consists of detrital deposits and biogenic reef deposits. The integration of biostratigraphy, magnetostratigraphy, climatostratigraphy and an astronomically calibrated chronology has led to the establishment of high-precision climatochronostratigraphic timescales for the detrital marine Quaternary in the South China Sea and the loess-paleosol sequence in the Chinese Loess Plateau. Extremely high-precision230 Th dating has provided a high-precision absolute age model for cave stalagmites over the past 640000 years as well as highresolution oxygen isotope records representing orbital-to suborbital-scale climate changes. By combining magnetic stratigraphy and biostratigraphy, robust chronostratigraphic frameworks for non-eolian continental Quaternary deposits on the scale of Quaternary geomagnetic polarities have been established. The continental Pleistocene Series consists, from oldest to youngest,of the Nihewanian Stage of the Lower Pleistocene, the Zhoukoudianian Stage of the Middle Pleistocene, and the Salawusuan Stage of the Upper Pleistocene. Stages of the continental Holocene Series have not yet been established. This review summarizes recent developments in the Quaternary chronostratigraphy of representative Quaternary strata and associated faunas, and then proposes an integrative chronostratigraphic framework and a stratigraphic correlation scheme for Quaternary continental strata in China. In the near-future, it is hoped to establish not only a Chinese continental Quaternary climatochronostratigraphic chart on the scale of glacial-interglacial cycles but also a Quaternary integrative chronostratigraphic chart including both continental and marine strata in China.

The big mantle wedge and decratonic gold deposits

The Circum-Pacific subduction zone is a famous gold metallogenic domain in the world,with two important gold metallogenic provinces,the North China Craton and Nevada,which are related to the destruction of the North China Craton and the Wyoming Craton,respectively.Their ore-forming fluids were possibly derived from the stagnant slab in the mantle transition zone.The oceanic lithospheric mantle usually contains serpentine layers up to thousands of meters thick.During plate subduction,serpentine is dehydrated at depths of<200 km and transformed into high-pressure hydrous minerals,known as Phases A to E,which carries water to the depth of>300 km.The overlying big mantle wedge is hydrated during the breakdown of these hydrous facies in the mantle transition zone.The dehydration of the subducted slab in the big mantle wedge releases sulfur-rich fluid,which extracts gold and other chalcophile elements in the surrounding rocks,forming gold-rich fluid.Because the cratonic geotherm is lower than the water-saturated solidus line of lherzolite,the fluid cannot trigger partial melting.Instead,it induces metasomatism and forms pargasite and other water-bearing minerals when it migrates upward to depths of less than 100 km in the cratonic lithospheric mantle,resulting in a water-and gold-rich weak layer.During the destruction of craton,the weak layer is destabilized,releasing gold-bearing fluids that accelerate the destruction.The ore-forming fluids migrate along the shallow weak zone and are accumulated at shallow depths,and subsequently escape along deep faults during major tectonic events,leading to explosive gold mineralization.The ore-forming fluids are rich in ferrous iron,which releases hydrogen at low pressure through iron hydrolysis.Therefore,decratonic gold deposits are often reduced deposits.

The use of fire at Zhoukoudian:evidence from magnetic susceptibility and color measurements

In order to provide direct evidence for the use of fire by humans at Locality 1,Zhoukoudian,we examine the burnt and unburnt sediments of newly excavated area in Layer 4 by detailed measurements of magnetic susceptibility,color,and diffuse reflectance spectrum.Results show that the magnetic susceptibility and redness of the burnt sediments are remarkably higher than those of other areas on the same level:up to*22 times for magnetic susceptibility and*3 times for redness of those of the adjacent unburnt sediments.Fine-grained(superparamagnetic/stable single-domain)magnetite and hematite grains make dominant contributions to the distinctly high values of magnetic susceptibility and redness in the burnt sediments.Diffuse reflectance spectroscopy results show that the burnt sediments contain more hematite than those of other areas and localities 2 and 3.High-temperature magnetic susceptibility measurements demonstrate that the burnt sediments have been heated above 700°C.Those changes in low-frequency magnetic susceptibility and redness are impossibly resulted from natural fires,thus most likely signaling the human activities of controlled use of fire.However,further work is needed to confirm whether or not these heat-affected sediments were produced in situ.

He and Ar isotope geochemistry of pyroxene megacrysts and mantle xenoliths in Cenozoic basalt from the Changle–Linqu area in western Shandong

We performed a combined study of He–Ar isotopes and element geochemistry for pyroxene megacrysts and mantle xenoliths from Cenozoic basalt in the Changle–Linqu area in western Shandong.The results are used to trace the evolution of subcontinental lithospheric mantle after destruction of the North China Craton.The3He/4He ratios of pyroxene megacrysts,websterite,and dunites are 7.0–7.7 Ra,7.4 Ra,and 7.0–7.7 Ra,respectively.They are related to the origin of host basalts,and are slightly lower than that of mid-ocean ridge basalts(MORB).Their40Ar/36Ar ratios are much lower than that of MORB and close to that of air.The lherzolites and wehrlites represent the fragments of the newly accreted lithospheric mantle,and their REE and trace elements indicate that they experienced melt metasomatism and partial melting.The3He/4He ratios of their olivine are slightly lower than that of MORB,but3He/4He ratios of their clinopyroxene are low(2.3–7.1 Ra)and display an inverse correlation with(La/Yb)N.The40Ar/36Ar ratios of these clinopyroxene are much lower than that of MORB and close to the air ratio.Combining existing studies of petrology,Sr–Nd–Pb isotopes,O isotopes,trace elements,and Mg isotopes,we infer that the juvenile lithospheric mantle in the Changle–Linqu area was metasomatized by oceanic crust-derived melts,which transfer the supracrustal Ar isotope signatures to the mantle sources.The low4He abundance and low3He/4He ratios of clinopyroxene in the lherzolites and wehrlites are ascribed to metasomatism by crustal melts from the subducted Pacific plate.

Link between the geomagnetic polarity reversal and global-geology events

The origin of the earth’s magnetic field is one of the five most important unsolved problems in physics, especially geomagnetic polarity reversal remains one of Nature’s most enigmatic phenomena. It is proposed that the geomagnetic polarity reversal links with some global-geology events, although it is difficult to clarify the mechanism of this correlation. The history of continental structures in eastern China would be also linked with some global-geology events.

Testing the mantle plume hypothesis： an IODP effort to drill into the Kamchatka-Okhotsk Sea basement

The great mantle plume debate(GPD) has been going on for ~15 years(Foulger and Natland, 2003;Anderson, 2004; Niu, 2005; Davies, 2005; Foulger, 2005; Campbell, 2005; Campbell and Davies, 2006),centered on whether mantle plumes exist as a result of Earth's cooling or whether their existence is purely required for convenience in explaining certain Earth phenomena(Niu, 2005). Despite the mounting evidence that many of the so-called plumes may be localized melting anomalies, the debate is likely to continue. We recognize that the slow progress of the debate results from communication difficulties.Many debaters may not truly appreciate(1) what the mantle plume hypothesis actually is, and(2) none of the petrological, geochemical and geophysical methods widely used can actually provide smoking-gun evidence for or against mantle plume hypothesis. In this short paper, we clarify these issues, and elaborate a geologically effective approach to test the hypothesis. According to the mantle plume hypothesis, a thermal mantle plume must originate from the thermal boundary layer at the core-mantle boundary(CMB), and a large mantle plume head is required to carry the material from the deep mantle to the surface. The plume head product in ocean basins is the oceanic plateau, which is a lithospheric terrane that is large(1000's km across), thick(>200 km), shallow(2–4 km high above the surrounding seafloors), buoyant(~1% less dense than the surrounding lithosphere), and thus must be preserved in the surface geology(Niu et al., 2003). The Hawaiian volcanism has been considered as the surface expression of a type mantle plume, but it does not seem to have a(known) plume head product. If this is true, the Hawaiian mantle plume in particular and the mantle plume hypothesis in general must be questioned. Therefore, whether there is an oceanic plateau-like product for the Hawaiian volcanism is key to testing the mantle plume hypothesis, and the Kamchatka-Okhotsk Sea basement is the best candidate to find out if it is indeed the Hawaiian mantle plume head product or not(Niu et al., 2003; Niu, 2004).