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地学前缘(英文版)
地学前缘(英文版)

莫宣学

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1674-9871

geofrontier@cugb.edu.cn

010-82322283,82321855

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北京市海淀区学院路29号中国地质大学（北京）期刊中心

地学前缘(英文版)/Journal GEOSCIENCE FRONTIERSCSCDCSTPCD北大核心SCI
查看更多>>GEOSCIENCE FRONTIERS (GSF) is a quarterly journal that publishes in English significant original research articles and high quality reviews of recent advances in all fields of Earth Sciences — including stratigraphy and paleontology, mineralogy and petrology, economic geology and minerals and fuel exploration, structural geology, lithospheric tectonics, environmental and engineering geology, hydrogeology, astrogeology, marine geology, and geophysics and geochemistry. Technical papers, case histories, reviews, and discussions are welcomed.
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    Chemical weathering processes in the Chinese Loess Plateau

    Ningpan ChaiZhiqi ZhaoXiaoke LiJun Xiao...
    199-211页
    查看更多>>摘要：Covered by erodible loess and affected by significant seasonal climate variations,chemical weathering in the Chinese Loess Plateau(abbreviated as CLP)has important effects on the hydrochemistry of the Yellow River and the global carbon cycle.However,chemical weathering processes in the CLP are still unclear.Based on 296 river water samples in the CLP in the different seasons,hydrochemistry,weathering pro-cesses,and their controlling factors were revealed.River waters in the CLP exhibited slightly alkalinity(pH=8.4±0.5)with much high total dissolved solids(TDS)values(691±813 mg/L).The water types of river water in the CLP were primarily SO42--Cl--Na+,HCO3--Ca2+-Mg2+,and SO42--Cl--Ca2+-Mg2+.According to the forward model,evaporite dissolution has the largest contri-bution(55.1％±0.2％)to riverine solutes in the CLP,then followed by carbonate weathering(35.6％±0.2％)and silicate weathering(6.5％±0.1％).For spatio-temporal variations,the contribution of evaporite disso-lution in the CLP decreased from northwest to southeast with higher proportion in the dry season,car-bonate weathering increased from northwest to southeast with a higher proportion in the wet season,and silicate weathering showed minor spatio-temporal variations.Ca2+and Mg2+were affected by car-bonate precipitation and/or incongruent calcite dissolution,and about 50％of samples exhibited cation exchange reactions.The physical erosion rate in the CLP,which was 372±293 t km-2·yr-1,varied greatly and was greater than those of other worldwide rivers.Chemical weathering rates in the CLP showed an increasing trend southward.During the wet season,high runoff led to the release of evaporite and car-bonate from loess,while the interfacial reaction kinetic limited the increase of the silicate weathering rates.The CO2 consumption budget by carbonate weathering(6.1×1010 mol/yr)and silicate weathering(1.6 ×1010 mol/yr)in the CLP accounted for 0.29％and 0.08％of the global carbon cycle,respectively.Meanwhile,the weathering proportion by sulfuric acids was relatively high with a CO2 release flux of 6.5 × 109 mol/yr.By compiling the data,we propose that the interfacial reaction kinetic and runoff con-trol CO2 consumption rate by silicate and carbonate weathering,respectively.These results contribute to the understanding of modern weathering processes of loess in the CLP,thus helping to deduce the envi-ronmental and climatic evolution of the basin.
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    Effects of source facies and maturity on individual carbon isotopic compositions of oil

    Jingkun ZhangJian CaoBaoli Xiang
    213-224页
    查看更多>>摘要：Carbon isotopes have been used extensively in tracing the sources of oil.However,primary source facies and secondary alteration controls on oil isotopic compositions have not been well resolved,resulting in application uncertainties.A case study was undertaken for an alkaline lacustrine oil system in a lower Permian formation in the Junggar Basin,NW China.Results indicate that increasing maturity causes the carbon isotopic composition to become heavier for only short-middle-chain compounds,whereas source facies-related carbon assimilation controls the compositions of short-,middle-,and long-chain compounds.In particular,light-carbon assimilation during organic-matter degradation makes the iso-topic composition lighter,whereas heavy carbon from the water mass makes it heavier.Accordingly,oils in this study area were divided into Type U and Type N oils based on individual compound carbon iso-topic compositions,reflecting the difference in source facies in a highly saline and reducing stratified water environment.The results provide a better understanding of the controls on carbon isotopes in oil in sedimentary basins,reducing the uncertainty in oil-source correlation and addressing the origin of oil.
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    Understanding arsenic behavior in alluvial aquifers:Evidence from sediment geochemistry,solute chemistry and environmental isotopes

    Shailesh Kumar YadavAL.RamanathanChidambaram SabarathinamAlok Kumar...
    225-241页
    查看更多>>摘要：The hydro-geochemistry and isotopic variations in groundwater,coupled with sediment geochemistry,were investigated in the Middle Gangetic Plain,India,to better understand the aquifer dynamics that influence the arsenic(As)evolution and mobilization.Eighty-four groundwater samples,thirteen River water samples,and two sediment cores(33 mbgl)were studied.The samples were analyzed for major ions and trace metals,including As and stable isotopic variability(δ2H,δ18O,and δ13C).The study area was categorized into older and younger alluvium based on existing geomorphological differences.Younger alluvium exhibits higher As enrichment in sediment and groundwater,ranging of 2.59-31.52 mg/kg and bdl to 0.62 mg/L.Groundwater samples were thermodynamically more stable with As(OH)3 species ranging from 88.5％to 91.4％and FeOOH from 69％to 81％,respectively.PHREEQC and mineralogical analysis suggested goethite and siderite act as a source and sink for As.However,statistical analysis suggested reductive dissolution as the primary mechanism for As mobilization in the study area.Spatio-temporal analysis revealed elevated concentrations of As in the central and northeastern regions of the study area.Stable isotope(δ2H and δ18O)analysis inferred active recharge conditions primarily dri-ven by precipitation.The depleted d-excess value and enriched δ18O in the groundwater of younger allu-vium indicate the effect of groundwater recharge with significant evaporation enrichment.Groundwater recharge potentially decreased the quantity of arsenic in groundwater,whereas evaporation enrichment increased it.Rainwater infiltration during recharge introduces oxygenated water into the aquifer,leading to changes in the redox conditions and facilitating biogeochemical reactions.The carbon isotope(δ13C)results suggest that high microbial activity in younger alluvium promotes As leaching from sediment into the groundwater.
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    Comparative analysis of CO2 emissions and economic performance in the United States and China:Navigating sustainable development in the climate change era

    Khalid MehmoodSyed Tauseef HassanXuchun QiuShahid Ali...
    243-259页
    查看更多>>摘要：Economic growth has brought a global climate change into the spotlight,and CO2 emissions demonstrate significant challenges in reducing environmental shifts worldwide.Globally,the United States and China contribute the largest amount of CO2 emissions.The purpose of this study is to examine the relationship between different types of CO2 emissions and economic growth by using a modeling approach.We ana-lyze total CO2 emissions,coal CO2 emissions,oil CO2 emissions,the global share of coal CO2 emissions,the global share of oil CO2 emissions,and economic growth.This study provides unique insights into how to simultaneously reduce CO2 emissions and sustain economic growth.A bootstrap autoregressive dis-tributed lag(BARDL)simulation method is utilized to examine the long-and short-run effects of predic-tors on CO2 emissions.Coal CO2 emissions are found to have a significant positive effect on economic growth in the short run but a negative impact on economic growth over the long run in the United States.The United States needs to implement stronger measures to balance coal CO2 emissions with eco-nomic growth for sustainable development.In contrast,oil CO2 emissions have positive effect for China in both the long run and short run.Thus,China can continue to reduce CO2 emissions from oil while main-taining positive economic growth.The China's policies promoting cleaner energy alternatives can be adapted and implemented to maintain a balance between economic growth and carbon reduction.The study has valuable insights for policymakers seeking to balance economic growth with carbon reduction strategies.It emphasizes the need to better understand the complex relationship between CO2 emissions and economic growth.
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    Late Neoproterozoic to early Cambrian high-grade metamorphism from Mikir Hills(Assam-Meghalaya gneissic Complex,northeast India):Implications for eastern Gondwana assembly

    Rahul NagH.HrushikeshNathan CognéN.Prabhakar...
    261-287页
    查看更多>>摘要：Mikir Hills region,which represents the eastern segment of the Assam-Meghalaya Gneissic Complex(AMGC)in northeast India,constitutes part of the Eastern Gondwana.The Mikir Hills preserves multiple metamorphic and magmatic events ranging from Early Mesoproterozoic to Early Cambrian.Out of these events,documenting the late Neoproterozoic to early Cambrian tectonothermal events is helpful in correlating the continental blocks of Eastern Gondwana.We present an integrated study involving field relations,petrology,P-T history and zircon-monazite geochronology of hitherto poorly studied pelitic and quartzo-feldspathic gneisses from the Mikir Hills region.These gneisses have experienced at least three deformation events(D1,D2 and D3)with dominant foliation indicated by ENE-WSW striking and shallow-moderately dipping(＜40°)S2 gneissic foliation.The peak metamorphism in pelitic and quartzo-feldspathic gneisses is characterized by garnet(core)-K-feldspar-sillimanite-plagioclase-bio tite-rutile-quartz-ilmenite-melt and garnet-plagioclase-K-feldspar-biotite-quartz-ilmenite-melt assemblages,respectively.The application of thermobarometric methods constrains the peak P-T conditions of 7.5-8.4 kbar at 674-778 ℃ and 6.7-7.4 kbar at 601-618 ℃ for pelitic and quartzo-feldspathic gneisses,respectively.These results are consistent with the values estimated using phase equilibria modelling and melt reintegration approach.The results of pseudosection modelling suggests a clockwise P-T path for pelitic gneisses involving migmatisation during peak metamorphism followed by near isothermal decompression from 8.0 to 8.6 kbar at 768-780 ℃ to 4.0-5.0 kbar at 720-765 ℃.In contrast,quartzo-feldspathic gneisses preserved slightly lower peak P-T conditions at 3.8-4.6 kbar and 590-650 ℃.The U-Pb zircon dating of migmatised pelitic and quartzo-feldspathic gneisses yielded concordant ages of 1647±11 Ma and 1590±7 Ma,respectively.These dates represent the inherited igneous protolith components,possibly equivalent to the Mesoproterozoic granulite facies metamorphism in the western AMGC.The rarely preserved cores of monazite in pelitic gneisses yielded an older population of 1058±35 Ma,most likely representing a weak tectonic imprint associated with the amalgamation of India with Western Australia and East Antarctica in the Rodinia assembly.However,the majority of monazite grains in pelitic and quartzo-feldspathic gneisses show high Th/U ratios with ages between 496±7 Ma and 467±16 Ma,indicating the timing of migmatisation that is contemporary with voluminous～500 Ma granite magmatism in and around the Mikir Hills.The similarities in P-T-t histories estimated in this study(eastern AMGC)and those obtained from the Sonapahar-Umpretha region(central AMGC)confirm that these domains experienced common tectonometamorphic history during Pan-African orogeny.The dominance of Late Neoproterozoic migmatisation and magmatism in the Mikir Hills region indicate that the eastern AMGC represent an active convergent margin with Western Australia and East Antarctica and evolved as a hot orogen during the assembly of Western and Eastern Gondwana continental fragments.
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    Selective metasomatism of ultramafic cumulates within Archean supracrustal sequences

    Lingyu ZhangSampriti BasakDavid ZakharovKristoffer Szilas...
    289-305页
    查看更多>>摘要：The Neoarchean Storø Supracrustal Belt in SW Greenland comprises a sequence of mature quartzite,metapelite,amphibolite,and ultramafic rocks that underwent amphibolite facies metamorphism during the amalgamation of the Mesoarchean Akia Terrane and the Eoarchean Færingehavn Terrane.In this belt,tourmaline is found in a transition zone between ultramafic and metapelitic rocks,but also occurs as orbicules within the ultramafic rocks.These tourmaline orbicules hosted by ultramafic rocks are reported for the first time in the North Atlantic craton,thus indicating a unique formation mechanism.We con-ducted a comprehensive examination of the petrology,whole-rock and mineral chemistry,and oxygen isotope compositions from borehole samples in the Storø Supracrustal Belt,to elucidate the metasomatic events associated with the formation of the orbicular tourmalines.The Storø ultramafic rocks have high MgO,Cr,and Ni contents,with low abundances of REE and HFSE,and preserve a typical cumulate texture.These features are similar to those of ultramafic cumulates found in other Archean supracrustal belts,suggesting a cumulate origin for the Storø ultramafic rocks.Furthermore,the morphology and composi-tion of the tourmaline orbicules within these cumulates indicate that they originated from melts with high boron and high water concentrations that infiltrated the ultramafic rocks.The main factor influenc-ing the morphology of the tourmaline orbicules is the silicification of the ultramafic rocks,driven by their lower chemical potential of SiO2 compared to the surrounding rocks.This silicification process,in com-bination with compositional variations of cumulates during fractional crystallization,has contributed to the geochemical diversity observed in Archean ultramafic rocks.Thus,it is crucial to understand the effects of such selective metasomatism on Archean ultramafic rocks,as this will facilitate the extraction of original information preserved in the early rock record.
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    Regional trends and petrologic factors inhibit global interpretations of zircon trace element compositions

    Nick M.W.RobertsChristopher J.SpencerStephen PuetzC.Brenhin Keller...
    307-314页
    查看更多>>摘要：The trace element composition of zircon reveals information about the melt that they are derived from,as such,detrital zircon trace element compositions can be used to interrogate melt compositions,and thus the evolution of the continental crust in time and space.Here,we present a global database of detrital zircon compositions and use it to test whether average global trends for five common petrogenetic prox-ies truly represent secular changes in continental evolution.We demonstrate that the secular trend is broadly comparable across continental regions for Ti-in-zircon temperatures,but for other trace element ratios interrogated,secular trends are highly variable between continental regions.Because trace element ratios result from multiple petrologic variables,we argue that these petrogenetic proxies can be overin-terpreted if projected to global geologic processes.In particular,we caution against the interpretation of crustal thickness from trace elements in zircon,and we argue that our results negate current hypotheses concerning secular changes in crustal thickness.
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    Kaapvaal lamproite melts(aka orangeites):A new type of alkali-carbonate liquid?insights from olivine-hosted multiphase inclusions(Silvery Home,South Africa)

    Adam AbersteinerAlexey TarasovAlexander GolovinGeoffrey H.Howarth...
    315-329页
    查看更多>>摘要：Kaapvaal lamproites(aka orangeites)are a group of volatile-rich(H2O,CO2),micaceous,ultrapotassic igneous rocks that are unique to the Kaapvaal craton in southern Africa.However,the composition of the melts that give rise to these rocks remains poorly understood due to overprinting effects of contam-ination by mantle and crustal material,volatile exsolution,fractional crystallisation and post-magmatic alteration.Consequently,this lack of reliable data on the initial composition of the Kaapvaal lamproite melts hampers our understanding of their source,petrogenesis and ascent mechanisms.Olivine is a common mineral comprising the Kaapvaal lamproites that has both xenocrystic(i.e.,man-tle)and magmatic origins.Multiphase inclusions(melt/fluid)entrapped within olivine have been consis-tently demonstrated as an effective tool for gaining fundamental insights into the composition and evolution of melts that produce both kimberlites and lamproites,prior to processes,such as eruption,devolatization and syn-/post-magmatic alteration.In this study,multiphase inclusions of both secondary and pseudosecondary origin hosted in olivine from a Kaapvaal lamproite(Silvery Home,South Africa)provide novel insights into the composition of the melt(s)that initially transported olivine to the surface and then crystallised after emplacement to form the lamproite groundmass.The inclusions in our study contain daughter mineral assemblages con-sisting of diverse Ca-Mg carbonates,including K-,Na-,Ba-,and Sr-bearing varieties,moderate K-rich sil-icates(phlogopite,tetraferriphlogopite),and subordinate oxides,phosphates,sulphides,sulphates,and halides.Based on these daughter mineral assemblages,we suggest that the composition of the melt entrapped by olivine was SiO2-poor,Ca-Mg carbonate-rich and contained elevated concentrations of K,Na,Ba,Sr,P and Cl.The mineral and reconstructed melt compositions are in stark contrast to the mineral association of the groundmass and the bulk-rock composition of the Silvery Home lamproite,respec-tively.We suggest that alkali-/alkali-earth carbonates,phosphates,sulphides,sulphates,and halides rep-resented a potentially significant,or even dominant,component of the melt that crystallised the Silvery Home lamproite but were likely removed by degassing and/or interaction with syn-/post-magmatic flu-ids.We show that olivine-hosted multiphase inclusions from the Silvery Home lamproite share many compositional similarities to melt inclusions hosted in olivine from kimberlites but are distinct from'classic'cratonic olivine lamproites worldwide.
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    Frontier of the Paleo-Tethys Ocean in the western Mediterranean:Isotopic(Sm-Nd)constraints on sources of Devonian units from Menorca Island

    Ricardo ArenasJosé M.FuenlabradaCristian TimonerRubén Díez Fernández...
    331-346页
    查看更多>>摘要：The c.1000-m-thick pre-orogenic Devonian mainly metapelitic sequence of North Menorca Island shows a fairly complete stratigraphic succession.The rocks of this sequence indicate gradually increasing deeper marine conditions of sedimentation towards its uppermost levels.Furthermore,the obtained sedimen-tary characteristics resemble those related to a deep and narrow basin-associated deposit.Thin sills of Ti-augite-bearing alkaline gabbros occur within the Devonian sequence.The intensity of Variscan defor-mation increases downwards through the structure.According to the characteristics of the Devonian sequence and its location within the Variscan Orogen,a correlation with similar units located in the southern sectors of the Central Iberian Zone(Iberian Massif)is suggested.The Devonian metapelitic rocks have geochemical characteristics suggesting that they represent moderately recycled mature siliciclastic sediments,generated from erosion of distant source areas belonging to an upper continental crust.The relatively narrow range of variation observed in initial 143Nd/144Nd ratios supports a similar source for the Menorcan slates(0.51165-0.51182).However,a marked trend is observed in these isotope ratios,from lower values at the base of the stratigraphic column(minimum value of 0.511941)to higher values at the top(maximum value of 0.512131).The 147Sm/144Nd ratios vary between 0.1074 and 0.1238,within the range defined for siliciclastic rocks with felsic crustal provenance.The Nd model ages define a narrow range between 1496 Ma and 1754 Ma(Late Paleoproterozoic-Early Mesoproterozoic),and they are con-sistently younger up-section.These data rule out a provenance from the erosion of the West Africa Craton,as they are more compatible with a provenance from regions located in the Trans-Saharan Belt or Sahara Metacraton.The characteristics of the Menorcan Devonian sequence are compatible with its deposition in a narrow and deep peri-Gondwanan transtensional basin,generated to the south of an advancing Variscan orogenic wedge.Systematic variations in the Nd isotopic composition indicate the progressive and continuous denudation of increasingly more easterly North African sectors in a colli-sional context between Laurussia and Gondwana with a marked dextral component.These data must be interpreted in the sense that there was not a large oceanic domain during Devonian times to the south of Iberia,able to block the arrival of detrital material from North Africa.A large tract of the Paleo-Tethys Ocean would therefore not have existed during the Devonian south of Iberia.This ocean must therefore have had limited extent in this period towards the westernmost sectors.The Devonian peri-Gondwanan shelf was apparently continuous around Iberia.This platform was progressively affected by Variscan deformation advancing from north to south and incorporated into the Variscan orogenic wedge with the same vergence.
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    In situ apatite and carbonate Lu-Hf and molybdenite Re-Os geochronology for ore deposit research:Method validation and example application to Cu-Au mineralisation

    Alexander SimpsonStijn GlorieMartin HandSarah E.Gilbert...
    347-362页
    查看更多>>摘要：The development of laser ablation inductively coupled plasma quadrupole tandem mass spectrometry(LA-ICP-Q-MS/MS)opens new opportunities to rapidly date a variety of hydrothermal minerals.Here we present in situ Lu-Hf and Re-Os dates for hydrothermal apatite and molybdenite,respectively.We fur-ther report the first in situ Lu-Hf dates for bastnäsite,dolomite,and siderite,and assess their potential for constraining ore deposit geochronology.For method validation,we report isotope-dilution Lu-Hf dates for apatite reference material Bamble-1(1102±5 Ma)and calcite reference material ME-1(1531±7 Ma),enabling improved accuracy on matrix-matched calibration for LA-ICP-MS/MS Lu-Hf dat-ing.The new methods are applied to the Vulcan Iron-Oxide Copper-Gold(IOCG)prospect in the Olympic Cu-Au Province of South Australia.Such deposits have been difficult to accurately date,given the general lack of reliable mineral geochronometers that are cogenetic with IOCG mineralisation.Hydrothermal apatite Lu-Hf dates and molybdenite Re-Os dates demonstrate that mineralisation at Vulcan largely occurred at ca.1.6 Ga,contemporaneous with the world class Olympic Dam deposit.Our data also indi-cates that the Lu-Hf system in apatite is more robust than the U-Pb system for determining the timing of primary apatite formation in an IOCG system.We further demonstrate that dolomite can retain Lu-Hf growth ages over an extended time period(＞1.5 billion years),providing constraints on the timing of pri-mary ore mineral crystallisation during brecciation and IOCG mineralisation.Finally,late Neoproterozoic(ca.589-544 Ma)and Carboniferous(ca.334±7 Ma)Lu-Hf dates were obtained for texturally late Cu-bearing carbonate veins,illustrating that the carbonate Lu-Hf method allows direct dating of Cu remobil-isation events.This has important implications for mineral exploration as the remobilised Cu may have been transferred to younger deposits hosted in Neoproterozoic sedimentary basins overlaying the Olympic IOCG province.
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