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地球化学学报（英文版）
中国科学院地球化学研究所
地球化学学报（英文版）

中国科学院地球化学研究所

涂光炽

季刊

2096-0956

hzl@mail.gyig.ac.cn cjgc@vip.skleg.cn

0851-5891358

550002

贵州省贵阳市观水路46号地球化学研究所

地球化学学报（英文版）/Journal Acta GeochimicaCSCD北大核心EI
查看更多>>本刊由中科院地化所和中矿物岩石地球化学学会主办，科学出版社出版，荷兰VSP出版公司向世界各国发行，中外颇具影响的地学刊物，多次获全国及中科院优秀期刊奖，并被国外多家检索系统收录。
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    The discovery of Late Triassic hypabyssal mafic dykes in the Huozhou complex and their geological significance:Evidence from petrology,geochemistry,and geochronology

    Haiyan LiuChong Peng
    1013-1036页
    查看更多>>摘要：The Huozhou complex in the Trans-North China Orogen exhibits two events of mafic magmatism(separated by ca.700 Ma):Neoproterozoic(920±15 Ma)Shimenyu diabase and Late Triassic(217±2.5 Ma)Xingtangsi dia-base.Investigations have focused on systematic petrology,zircon U-Pb dating,Lu-Hf isotopes,and lithogeochemistry.The research findings indicate that the Late Triassic Xing-tangsi diabase of the Huozhou complex can be classified as a transitional type between intermediate and mafic rocks based on their SiO2 content.This classification is supported by an average SiO2 content of 53.94％,ranging from 53.33％to 54.28％.In the Zr/TiO2 vs.Ce diagram,all samples lie within the range of basalt.The zircons from the Late Trias-sic Xingtangsi diabase have low eHf(t)values ranging from-12.7 to-8.7,with an average of-11.1.Additionally,the single-stage model age TDM1 is estimated to be between 1207 and 1701 Ma.These findings suggest that the magma responsible for the dyke originated from either partial melt-ing or an enriched mantle source inside the Meso-Protero-zoic lithospheric mantle.The elevated concentrations of Th(thorium)and LREEs(light rare earth elements),as well as the Th/Yb and Th/Nb ratios,suggest the potential incor-poration of subducted sediments within the magma source region.The rock displays negative Nb,Ta,Zr,Hf,and Ti anomalies.These geochemical attributes align with the dis-tinctive traits observed in volcanic rocks found within island arcs.The formation of the Late Triassic Xingtangsi diabase is likely associated with the geological context of an arc setting,which arises from the collision between the Yangtze plate and the North China Craton.
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    Hydrothermal alteration of the surface volcanic rocks at the Acoculco geothermal field,Mexico:a multi-parametric approach

    America Yosiris García-SotoKailasa PandarinathE.SantoyoEduardo Gonzalez-Partida...
    1037-1053页
    查看更多>>摘要：The studies on hydrothermal alteration-induced effects in surface and subsurface rocks provide useful infor-mation in the characterization and exploitation of a geother-mal reservoir.Generally,these studies are based on tradi-tional,and reliable methods like petrography(primary and secondary minerals,and grade of alteration),and geochemis-try(mobility of elements,changes in mass and concentration of elements,and fluid inclusions).Recently,apart from these established methods,some methods based on the geochemi-cal(Chemical Index of Alteration,CIA;Weathering Index of Parkar,WIP;Loss on Ignition,LOI;and Sulfur,S)and rock magnetic properties(magnetic susceptibility,xlf;and percentage frequency-dependent susceptibility,xfd％)are also being applied in the identification of whether a rock is an altered or a fresh one.The Acoculco Geothermal Field(AGF),Mexico,is characterized by high temperature and very low permeability,and it is considered a promissory Enhanced Geothermal System.The following changes are observed in the rocks as a result of an increase in hydro-thermal alteration:(1)an increase in CIA,LOI,and S val-ues,and a decrease in WIP;(2)an increase in quartz and quartz polymorph minerals(silicification),and clay minerals(argillization);and(3)decrease in xlf values.At AGF,the most altered surface acid rocks are characterized by entirely quartz and its polymorphs,and clay minerals.The present study also indicates the applicability of the binary plots of major elements(felsic vs mafic component)and rock mag-netic parameters(xlf vs.xfd％).The rock with xfd％value of 2-10 and xlf value＜0.5 × 10-6 m3 kg-1 indicate the presence of single domain and stable single domain grains,which in turn suggests that it is an altered rock.These methods are simple to apply,rapid,reliable,and have the potential to become effective tools for the identification of hydrother-mally altered rocks during the initial stage of geothermal exploration.
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    Precise and accurate Ga isotope ratio measurements of geological samples by multi-collector inductively coupled plasma mass spectrometry

    Yuxu ZhangPan QiaoChuanwei ZhuHaifeng Fan...
    1054-1064页
    查看更多>>摘要：Gallium isotope is a potential geochemical tool for understanding planetary processes,environmental pol-lution,and ore deposit formation.The reported Ga isotope compositions(δ71GaNIST994 values)of some international geological standards,such as BCR-2 and BHVO-2 basalts,exhibit inconsistencies between different laboratories.Dur-ing mass spectrometry analysis,we found that δ71GaNIST994 values of geological standards with or without the correc-tion of the interference of 138Ba2+(mass/charge ratio=69)on 69Ga show significant isotope offsets,and thus efficient separation of Ba and correcting the interference of 138Ba2+are both crucial to obtain accurate δ71Ga values.By com-paring δ71GaNIST994 values(relative to NIST SRM 994 Ga)of the same geostandards from different laboratories,we suggest that the isotopic heterogeneity from NIST SRM 994 Ga is one of the key reasons for the inconsistencies inδ71GaNIST994 values of BCR-2 and BHVO-2.To facilitate inter-laboratory comparisons,we measured the Ga isotopic compositions of 11 geological reference materials(includ-ing Pb-Zn ore,bauxite,igneous rocks,and loess)and two Ga solution standards(NIST SRM 3119a and Alfa Aesar).The 871GaNIST994 and δ71GaIPGP values of these reference materials vary from 1.12 ‰ to 2.63 ‰ and-0.13 ‰ to 1.38‰,respectively,and can be used to evaluate the precision and accuracy of Ga isotope data from different laboratories.
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    Harnessing machine learning tools for water quality assessment in the Kebili shallow aquifers,Southwestern Tunisia

    Zohra KraiemKamel ZouariRim Trabelsi
    1065-1086页
    查看更多>>摘要：An integrated method that implements multivari-ate statistical analysis and ML methods to evaluate ground-water quality of the shallow aquifers of the Djerid and Kebili district,Southern Tunisia,was adopted.An evaluation of their suitability for irrigation and/or drinking purposes is necessary.A comprehensive hydrochemical assessment of 52 samples with entropy weighted water quality index(EWQI)was also proposed.Eleven water parameters were calculated to ascertain the potential use of those resources in irrigation and drinking.Multivariate analysis showed two main components with Dim1(variance=62.3％)and Dim.2(variance=22％),due to the bicarbonate,dissolu-tion,and evaporation and the intrusion of drainage water.The evaluation of water quality has been carried out using EWQI model.The calculated EWQI for the Djerid and Kebili waters(i.e.,52 samples)varied between 7.5 and 152.62,indicating a range of 145.12.A mean of 79.12 was lower than the median(88.47).From the calculation of EWQI,only 14 samples are not suitable for irrigation because of their poor to extremely poor quality(26.92％).The bivariate plot showed high correlation for EWQI-TH(r=0.93),EWQI～SAR(r=0.87),indicating that water quality depended on those parameters.Different ML algo-rithms were successfully applied for the water quality clas-sification.Our results indicated high prediction accuracy(SVM＞LDA＞ANN＞kNN)and perfect classification for kNN,LDA and Naive Bayes.For the purposes of develop-ing the prediction models,the dataset was divided into two groups:training(80％)and testing(20％).To evaluate the models'performance,RMSE,MSE,MAE and R2 metrics were used.kNN(R2=0.9359,MAE=6.49,MSE=79.00)and LDA(accuracy=97.56％;kappa=96.21％)achieved high accuracy.Moreover,linear regression indicated high correlation for both training(R2=0.9727)and testing data(0.9890).This well confirmed the validity of LDA algorithm in predicting water quality.Cross validation showed a high accuracy(92.31％),high sensitivity(89.47％)and high speci-ficity(95％).These findings are fundamentally important for an integrated water resource management in a larger context of sustainable development of the Kebili district.
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    • 万方数据
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    Zircon U-Pb geochronologic,geochemical and Sr-Nd-Pb isotope characteristics of the Beidaban granites in the North Qilian Orogenic Belt:Petrogenesis and tectonic implications

    Tao YangZhi-yuan SunMing-liang WangXiao-qiang Zhu...
    1087-1104页
    查看更多>>摘要：The tectonic evolution and crustal accretion pro-cess of the North Qilian Orogenic Belt(NQOB)are still under debate because of a lack of integrated constraints,especially the identification of the tectonic transition from arc to initial collision.Here we present results from zir-con U-Pb geochronology,whole-rock geochemistry,and Sr-Nd-Pb isotope geochemistry of the Beidaban granites to provide crucial information for geodynamic evolution of NQOB.Zircon U-Pb dating yields an age of 468±10 Ma for the Beidaban granites and most of the Beidaban samples contain amphibole,are potassium-rich,and have A/CNK values ranging from 0.7 to 0.9,illustrating that the Middle Ordovician Beidaban granites are K-rich,metaluminous,calc-alkaline granitoid.The geochemical characteristics indicate that the Beidaban granites are transitional I/S-type granitoids that formed in an arc setting.The isotopic com-positions of initial(87Sr/86Sr)i values ranging from 0.70545 to 0.71082(0.70842 on average)and eNd(t)values ranging from-10.9 to-6.7(-8.8 on average)with two-stage Nd model ages(TDM2)of 1.74-2.08 Ga suggest that the Bei-daban granites originated from Paleoproterozoic crustal materials.In addition,the initial Pb isotopic compositions(206Pb/204Pb=19.14-20.26;207Pb/204Pb=15.71-15.77;208Pb/204Pb=37.70-38.26)and geochemical features,such as high Th/Ta(17.43-30.12)and Rb/Nb(6.01-15.49)values,suggest that the Beidaban granite magma source involved recycled crustal components with igneous rocks.Based on these results in combination with previously pub-lished geochronological and geochemical data from other early Paleozoic igneous rocks,we suggest that the timing of the tectonic transition from arc to the initial collision to the final closure of the North Qilian Ocean can be constrained to the Middle-Late Ordovician(ca.468-450 Ma).
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    Origin and geochemical characteristics of beryllium mineralization in the Zabara-Wadi El Gemal region,South Eastern Desert,Egypt

    Gehad M.SalehFarrage M.KhalealMohammed Z.El-BialyMohamed S.Kamar...
    1105-1122页
    查看更多>>摘要：Beryl is the commercial source of beryllium and several varieties of it are valued as a gemstone.To contribute to understanding the mechanism of beryl forma-tion,we carried out detailed geological,petrographical,and geochemical investigations on beryl mineralization occur-rences in the Zabara-Wadi El Gemal(Z-WG)region.This region is an NW-SE trending tract that includes six beryl-hosting areas.The green gem variety of beryl(emerald)is restricted to phlogopite schist,pegmatite,and quartz veins.Prismatic hexagonal emerald crystals are well-developed in phlogopite schist and pegmatite.The gem variety emerald examined is sodic and Cr-dominant.It contains high con-centrations of chromophore transition elements ordering Cr(up to 1511 ppm)＞V(up to 242 ppm)＞Sc(up to 245 ppm),giving rise to its vivid green color,reflecting mafic-ultra-mafic source contribution.Among the investigated emeralds,the Sikait area contains the highest BeO(av.10.76wt.％)concentration.The compositional variability of emeralds is most likely attributed to the contribution from the host rocks.This is revealed by the examined emerald mineralization,for instance;the Abu Rusheid area(one of the best areas expos-ing rare metal-bearing granitoids)possesses the highest average of trace and REEs concentrations.In contrast,Um Kabu emerald has the highest contents of Co(av.20 ppm),Ni(av.299 ppm),MgO(av.8.2wt.％),Fe2O3(av.3.12wt.％),and CaO(avg.3.4wt.％)relative to other areas,which may be linked to contribution of ultramafic rocks exposed there.The proposed mechanism we suggest for emerald genesis is metasomatic interaction between felsic(intrusions,that are enriched with K,Na,Be,Li,and B,with mafic-ultramafic rocks that are enriched in Cr,V,Mg,Fe,and Ca.This inter-action is marked by the formation of phlogopite schist,the growth of emerald crystals,and desilicated pegmatite.
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    Can soil remediation agents synergistically mitigate rice Cd content and CH4 emission from karst paddies?

    Wangbiao LuGuangneng ZengWeijun LuoJiangju Song...
    1123-1132页
    查看更多>>摘要：Rice(Oryza sativa L.)paddies are increasingly threatened by cadmium(Cd)pollution,and potentially serve as CH4 emitters to the atmosphere.Remediation agents widely mitigate Cd pollution in paddy soil,however,we know little about their regulations on CH4 emission.Here,via adding biochar(B),sulfhydryl-modified palygorskite(SMP),and selenium foliar fertilizer(SFF),we conducted a pot experiment to investigate soil and rice Cd contents together with in-situ CH4 fluxes.Compared to CK,the addition of SMP,SFF,and B-SMP reduced Cd in brown rice by 25％to 50％,25％,and 50％to 75％,respectively.Agents 7％B,7％B-0.01％SMP,and SFF reduced CH4 emissions by 8.46％,5.30％,and 4.11％,respectively.CH4 emission increased gradually along the growing season,with the cumulative CH4 fluxes ranging between 338.82 and 619.13 kg hm-2.Our results highlight that mixed 7％B-0.01％SMP and SFF showed collaborative effects on Cd remediation and CH4 emission.This study reveals the fea-sibility of reducing Cd pollution and CH4 emission in karst rice paddies,which hopes to supplement the knowledge of collaborative controls on soil remediation and carbon emission.
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    Catagenetic type of manganese ores:REE and isotope(δ13C,δ18O)geochemical features(on the example of the Usa deposit,Russia)

    Vladimir N.KuleshovAndrey Yu.BychkovIrina Yu.NikolaevaMaria E.Tarnopolskaia...
    1133-1152页
    查看更多>>摘要：Chemical(REE and major elements)and isotope(δ13C,δ18O)composition of carbonate manganese ores and manganese-bearing carbonates of the Usa deposit(Siberia,Russia)were studied.Received data on the composition of REE exhibit both the distinct negative(Ce/Ce*PAAS＜1)and positive(Ce/Ce*PAAS＞l)cerium anomalies and the positive Eu-anomaly(Eu/Eu*PAAS＞1).Negative Eu-anomalies are not observed.The contents of Mn,Fe,REE,and Ce-anomalies show a positive correlation with each other.Ce-anomalies and the amount of manganese and REE in relation to the car-bon isotope composition(δ13C)show a negative relationship and indicate that oxidized carbon of organic matter played an important role in the concentration of manganese and REE in manganese ores.The chemical and isotope composition of examined rocks indicates on secondary formation of Mn-ores.Two major phases and sources are distinguished in the ore-forming process characterized by different chemical(REE and ore elements)and isotope composition:(ⅰ)high-grade manganese ores(with high contents of REE and light carbon isotope composition)and(ⅱ)low-grade manganese ores(with low contents of REE and heavy carbon isotope composition).
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    Fluid inclusion and H-O-S-Pb isotope systematics of the Chayong Cu-polymetallic deposit,Sanjiang Metallogenic Belt,Qinghai Province,China

    Jian WangHao WangFengyue SunFei Wang...
    1153-1168页
    查看更多>>摘要：The Chayong Cu-polymetallic deposit is a recently discovered Cu-polymetallic deposit hosted in the Sanjiang Metallogenic Belt within the Tibetan Plateau of China to the northeast of the North Qiangtang terrane.The ore body occurs in siltstone and is controlled by a north-west-trending fault structure.According to the associations,assemblages,and cutting relationships between ore veins,the hydrothermal mineralization period can be divided into three mineralization stages:(1)a molybdenite mineralization stage,(2)a Cu-polymetallic sulfide stage,and(3)a quartz-carbonate stage.Two types of fluid inclusions(FIs),namely,liquid and vapor-rich inclusions,are present in quartz associated with sulfide minerals.Early-stage FIs are both liquid and vapor-rich,homogenized at temperatures ranging from 364.1 to 384.2 ℃,and have salinities ranging from 0.70％to 9.60％NaCl equivalent(eqv).The middle-stage FIs are also both liquid-and vapor-rich,homogenized at tem-peratures ranging from 272.4 to 355.6 ℃,and have salinities ranging from 0.53％-17.10％NaCl eqv.The late-stage FIs are liquid,homogenized at temperatures ranging from 209.4 to 255.3 ℃,and have salinities ranging from 0.35％-6.87％NaCl eqv.The samples from the deposit have δ34S values of-21.8‰ to-19.2‰ and-5.5‰ to-6.0‰,suggesting that sulfur was derived from the host sediments and mag-matic fluids,respectively.The metallic minerals within the deposit have 206Pb/204Pb,207Pb/204Pb,and 208Pb/204Pb val-ues of 18.439-18.458,15.656-15.679,and 38.772-38.863,respectively,suggesting that the metals were derived from the upper crust and orogenic belts.The samples from the deposit have δ18OW values of 2.99‰-7.99‰ and δDW val-ues ranging from-84.4‰ to-73.9‰,indicating that the ore-forming fluids were magmatic and mixed with minor amounts of meteoric water.The ore-forming fluid of the Chayong copper polymetallic deposit was a high-temper-ature,medium-to low-salinity H2O-NaCl-CH4-N2±CO2 fluid system.The early high-temperature magmatic fluid,due to boiling,decreased in temperature,and via the mixing of meteoric water,gradually evolved towards the later-stage medium-to low-temperature and low-salinity fluid,causing molybdenite mineralization and forming copper polymetallic sulfide veins and quartz carbonate veins.
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    Mineralogical and geochemical characterization of the Wadi Natash volcanic field(WNVF),Egypt:Alkaline magmatism in a Late Cretaceous continental rift system

    Adel A.SurourAhmed A.MadaniMohamed A.El-Sharkawi
    1169-1191页
    查看更多>>摘要：The Wadi Natash volcanic field(WNVF)in the south of the Eastern Desert of Egypt is a typical example of well-preserved intraplate alkaline magmatism during the Late Cretaceous,i.e.,prior to the Oligo-Miocene Red Sea rift.We compiled stratigraphic sections at two sec-tors;namely East Gabal Nuqra and West Khashm Natash(WKN)where the volcanic flows are intercalated with the Turonian Abu Agag sandstone with occasional paleosols when volcanic activity is intermittent.Peridotite mantle xenoliths are encountered in the first sector whereas flows in the second sector are interrupted by trachyte plugs and ring dykes.On a geochemical basis,the mafic melt origi-nating from the lithospheric mantle beneath the WNVF practiced～5％partial melting of phlogopite-bearing garnet peridotite.Basalts dominate in the two sectors and highly evolved(silicic)rocks are confined to the WKN sector.Rejuvenation of ancient Precambrian fractures following the NW-SE and ENE-WSW trends facilitated the ascend of Late Cretaceous mantle-derived alkaline magma.Struc-turally,the WNVF developed at the eastern shoulder of the so-called"Kom Ombo-Nuqra-Kharit rift system"that represents a well-defined NW-trending intracontinental rift basin in the southern Eastern Desert.In such a structural setup,the Natash volcanic are confined to half-grabens at the East Gabal Nuqra sector whereas the West Khashm Natash sector is subjected to extensional stresses that propagated eastwards.The WNVF is a typical example of fluvial clastics(Turonian)intercalation with rift-related alkaline volcanic rocks in northeast Africa.
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