Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Sy...Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.展开更多
Geochemical survey data are essential across Earth Science disciplines but are often affected by noise,which can obscure important geological signals and compromise subsequent prediction and interpretation.Quantifying...Geochemical survey data are essential across Earth Science disciplines but are often affected by noise,which can obscure important geological signals and compromise subsequent prediction and interpretation.Quantifying prediction uncertainty is hence crucial for robust geoscientific decision-making.This study proposes a novel deep learning framework,the Spatially Constrained Variational Autoencoder(SC-VAE),for denoising geochemical survey data with integrated uncertainty quantification.The SC-VAE incorporates spatial regularization,which enforces spatial coherence by modeling inter-sample relationships directly within the latent space.The performance of the SC-VAE was systematically evaluated against a standard Variational Autoencoder(VAE)using geochemical data from the gold polymetallic district in the northwestern part of Sichuan Province,China.Both models were optimized using Bayesian optimization,with objective functions specifically designed to maintain essential geostatistical characteristics.Evaluation metrics include variogram analysis,quantitative measures of spatial interpolation accuracy,visual assessment of denoised maps,and statistical analysis of data distributions,as well as decomposition of uncertainties.Results show that the SC-VAE achieves superior noise suppression and better preservation of spatial structure compared to the standard VAE,as demonstrated by a significant reduction in the variogram nugget effect and an increased partial sill.The SC-VAE produces denoised maps with clearer anomaly delineation and more regularized data distributions,effectively mitigating outliers and reducing kurtosis.Additionally,it delivers improved interpolation accuracy and spatially explicit uncertainty estimates,facilitating more reliable and interpretable assessments of prediction confidence.The SC-VAE framework thus provides a robust,geostatistically informed solution for enhancing the quality and interpretability of geochemical data,with broad applicability in mineral exploration,environmental geochemistry,and other Earth Science domains.展开更多
Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies a...Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies associated with adverse geology provide a novel strategy for addressing these limitations.However,statistical methods for identifying geochemical anomalies are insufficient for tunnel engineering.In contrast,data mining techniques such as machine learning have demonstrated greater efficacy when applied to geological data.Herein,a method for identifying adverse geology using machine learning of geochemical anomalies is proposed.The method was identified geochemical anomalies in tunnel that were not identified by statistical methods.We by employing robust factor analysis and self-organizing maps to reduce the dimensionality of geochemical data and extract the anomaly elements combination(AEC).Using the AEC sample data,we trained an isolation forest model to identify the multi-element anomalies,successfully.We analyzed the adverse geological features based the multi-element anomalies.This study,therefore,extends the traditional approach of geological analysis in tunnels and demonstrates that machine learning is an effective tool for intelligent geological analysis.Correspondingly,the research offers new insights regarding the adverse geology and the prevention of hazards during the construction of tunnels and underground engineering projects.展开更多
Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geologi...Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geological features, it holds crucial information for understanding the evolution of the Saharan Meta craton (central Africa), which remains poorly studied. One of the objectives is to map the formations Precambrian age in Southeastern Chad. Based on the petrographic and geochemical results, we identified granitoids of pan-African age (biotite granite, aplite granite and pegmatite granite). This Precambrian basement is covered with sedimentary formations (clays, argillites, lateritic cuirasses, etc.). The mineral assemblage is characteristic of acid rocks. Geochemistry reveals rocks with a high SiO2 range (62% - 77%) giving sub-alkaline to calc-alkaline acid rocks with high k (4.62% to 6.39%). The granitoids are classified as S-type hyperaluminous granites. This classification is supported by the presence of peraluminous minerals (e.g., muscovite) within the Iro granitoids, which also have high (>1%). Geochemical variation within the granites is largely due to extensive crystal fractionation. The Pattern of REEs normalized to the primitive mantle shows a pronounced negative Eu anomaly, reflecting the crystallization process and fractional crystallization of plagioclase in the rock, and a positive Yb anomaly. The role of plagioclase fractionation was relatively major during the earlier intrusive stages (consistent with the presence of Eu anomalies) and slightly increased, together with biotite and K-feldspar fractionation, during the later (granitic) rock crystallization. The Pattern of the spider normalized to MORBs shows two pronounced negative anomalies in TiO2 and Cs and a slight negative anomaly in Ba. The loss of Ba, Ti and Cs may be caused by the plagioclase fractionation, apatite and ilmenite crystal. The Ba anomaly is also controlled by the presence of K-feldspar and mica. The observed Ti anomalies are due to the fractionation of magnetite indicating a subduction environment (or remelting of a source from a subduction environment).展开更多
The Malacca Strait(MS)is a vital conduit for the exchange of water and sediment between the Indian Ocean and the Pacific Ocean,serving as a critical‘gateway'for sediment transport.Here,we present the geochemical ...The Malacca Strait(MS)is a vital conduit for the exchange of water and sediment between the Indian Ocean and the Pacific Ocean,serving as a critical‘gateway'for sediment transport.Here,we present the geochemical characteristics of surface sediments in the MS to elucidate the relationship between terrestrial material inputs and modern oceanic dynamic transport processes in the strait.The results reveal that the MS can be divided into three distinct geochemical provinces.ProvinceⅠ,located in the central region of the strait,is characterized by residual deposits.The preservation of these residual deposits can be attributed to the restricted sediment supply and the relatively weaker modern sedimentary hydrodynamic conditions.ProvinceⅡ,situated to the north of ProvinceⅠ,exhibits provenance differences between its southern and northern regions.The northern region is primarily supplied by sediments originating from the eastern shelf of the Andaman Sea,whereas sediments derived from Sumatra and the Sunda Shelf are predominantly deposited in the southern part of ProvinceⅡ.ProvinceⅢextends along the western coast of the Malaysian Peninsula,with sediments primarily sourced from the Malaysian Peninsula and the Sunda Shelf,while contributions from Sumatra and the eastern shelf of the Andaman Sea are negligible.River sediments from the Malaysian Peninsula and Sumatra are transported northwestward along their respective coasts by prevailing currents,which also facilitate the transportation of Sunda Shelf sediments within the strait,while sediments from the eastern shelf of the Andaman Sea are delivered to the MS via southward coastal currents during the southwest monsoon period.The southward currents and well-developed eddies potentially impede the northward transport of sediments from the Sunda Shelf and restrict the distribution of Andaman Sea sediments within the strait.This study substantially enhances the understanding of source-to-sink processes in the Indo-Pacific region.展开更多
Lithium is a critical strategic metal with signifi-cant reserves in pegmatites,serving as the primary source for global Li production.Apatite has attracted increasing attention as an indicator in petrogenesis studies ...Lithium is a critical strategic metal with signifi-cant reserves in pegmatites,serving as the primary source for global Li production.Apatite has attracted increasing attention as an indicator in petrogenesis studies and for the exploration of ore deposits.In this study,we investigated the volatile compositions and major and trace elements of apatite from the Qiongjiagang pegmatite-type lithium deposit in Himalaya.Apatite derived from spodumene pegmatite exhibits relatively constant and high total rare earth element(ΣREE+Y)concentrations,ranging from 5899 to 8540 ppm.In contrast,apatite in barren pegmatite displays evidently lower(ΣREE+Y)concentrations,varying between 1345 and 3095 ppm.The REE patterns of apatite in spodumene pegmatite generally exhibit a flat shape[(La/Yb)N=1.55-2.15)],with distinctively negative Eu anomalies(Eu_(N)/Eu_(N)^(*)=0.14-0.22),slightly positive Ce anomalies(Ce_(N)/Ce_(N)^(*)=1.03-1.13),and low Y/Ho ratios(28-30).By contrast,apatite in barren pegmatite shows middle rare earth element(MREE)-depleted downward-convex patterns[(La/Yb)N=1.99-20.4)],strongly negative Eu anomalies(Eu_(N)/Eu_(N)^(*)=0.01-0.14),slightly positive Ce anomalies(Ce_(N)/Ce_(N)^(*)=1.10-1.24),and high Y/Ho ratios(30-55,with an average of 50).Overall,the high concentrations ofΣREE(and Y)and low Th/U and Y/Ho ratios can serve as diagnostic indicators to distinguish apatite in spodumene pegmatite from that in barren pegmatite.Furthermore,the flat REE pattern may represent a common feature of apatite from lithium deposits.Differences in the Ce and Eu anomalies between apatite from these two kinds of pegmatites likely reflect formation under different redox conditions.Consequently,based on calculations derived from apatite volatile compositions,the melt associated with spodumene pegmatite may contain higher water content compared to that of the barren one.Therefore,the mineralized pegmatite system may incorporate substantial amounts of H_(2)O-rich fluids,which play a crucial role in lithium mineralization.展开更多
Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margi...Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.展开更多
This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evol...This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evolution,petrogenesis,and mantle-source magama characteristics of the Mid-Pacific Mountains.The basalts from the Mid-Pacific Mountains are predominantly alkali basalts,rich in alkalies,and changing in potassium.They exhibit geochemical features of ocean island basalts(OIB),with distinct fractionation between light and heavy rare-earth elements and a pronounced Ce negative anomaly(δ_(Ce)=0.16–1.10,average 0.84),along with enrichment in large ion lithophile elements(LILEs).The Mid-Pacific Mountains are intraplate ocean island basalts formed by mantle plume(hotspot)activity,originating mainly from an enriched mantle magma source region,and most of them have undergone low degree of partial melting and a certain degree of crystalline differentiation,with negligible contamination from oceanic crust materials.The Mid-Pacific Mountains exhibit ratios of^(87)Sr/^(86)Sr(i)(0.702733–0.704313,average 0.703452)and^(143)Nd/^(144)Nd(i)(0.512698–0.512996,average 0.512846)which are close to the HIMU mantle endmember,and ratios of 206Pb/204Pb(18.953–19.803),^(207)Pb/^(204)Pb(15.54–15.62)and^(208)Pb/^(204)Pb(38.813–39.514)which are close to the EMII mantle end-member.Combined with the isotopic geochemical characteristics in the West Pacific Seamounts province,the basalts from the Mid-Pacific Mountains were considered to represent a certain proportion of mixing mantle end-members between the HIMU and EMII,possibly formed by the mixing of the HIMU superplume in the South Pacific hotspot region with the EMII secondary mantle plume in the transition zone during their ascent.展开更多
The Langrial iron ore deposits,located in the villages of Dubran and Darkot in Hazara,Pakistan,were evaluated using remote sensing,magnetic,and geochemical investigations.Data from ASTER,Landsat-8,and Sentinel-2 satel...The Langrial iron ore deposits,located in the villages of Dubran and Darkot in Hazara,Pakistan,were evaluated using remote sensing,magnetic,and geochemical investigations.Data from ASTER,Landsat-8,and Sentinel-2 satellites were utilized and processed through techniques such as band ratio analysis,band compositing,and NDVI masking to reduce vegetation effects and to delineate various lithological units and mineralogical signatures within the study area.Magnetic anomalies revealed multiple levels of iron mineralization,with the hematite zone showing the most significant potential for high-grade iron ore.Geochemical analyses confirmed the presence of iron,along with minerals such as chromium,calcium,magnesium,and lead.In Dubran,mean iron concentrations are recorded at 370.94 mg/kg,whereas in Darkot,they reach up to 2052 mg/kg.The integration of remote sensing,magnetic,and geochemical data delineates key mineralized zones in the various parts of the study area.This research highlights the importance of combining geophysical and geochemical methodologies to refine mineral exploration efforts.The findings enhance our understanding of the Langrial iron ore deposits and highlight their economic potential for sustainable mining practices.This study will contribute to meeting the growing demand for iron ore resources and reducing Pakistan's reliance on imports,thereby promoting the sustainable development of local industries.展开更多
The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and signi...The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and significantly variable gas contents of the drilled shales.Excitingly,the first major breakthrough in deep and ultra-deep Lower Cambrian shale gas was made recently in the well Z201 in the southern Sichuan Basin,with a gas yield exceeding 73×10^(4)m^(3)/d.The success of well Z201 provides a favorable geological case to reveal the distinct enrichment mechanism of deep and ultra-deep Lower Cambrian shale gas.In this study,at drilling site of well Z201,fresh shale core samples with different gasin-place contents were collected,and their geochemical,pore development and water-bearing characteristics were analyzed systematically.The results showed that the Z201 organic-rich shales reached an overmature stage,with an average Raman maturity of 3.70%.The Z201 shales with high gas-in-place contents are mainly located in the Qiongzhusi 12section and the upper Qiongzhusi 11section,with an average gas-in-place content of 10.08 cm^(3)/g.Compared to the shales with low gas-in-place contents,the shales with high gas-in-place contents exhibit higher total organic carbon contents,greater porosities,and lower water saturations,providing more effective pore spaces for shale gas enrichment.The effective pore structures of the deep and ultra-deep Lower Cambrian shales are the primary factors affecting their gas-in-place contents.Similar to the shales with high gas-in-place contents of well Z201,the deep and ultra-deep Lower Cambrian shales in the Mianyang-Changning intracratonic sag,especially in the Ziyang area,generally developed in deep-water shelf facies with high total organic carbon contents and thick sedimentary thickness,providing favorable conditions for the development and preservation of effective pores.Therefore,they are the most promising targets for Lower Cambrian shale gas exploration.展开更多
The intertidal zone of mangroves has a significant impact on the ecological environment by serving as a crucial habitat for a wide range of organisms.When assessing heavy metal contamination in sediments within this z...The intertidal zone of mangroves has a significant impact on the ecological environment by serving as a crucial habitat for a wide range of organisms.When assessing heavy metal contamination in sediments within this zone,it is essential to establish a regional geochemical baseline that accounts for natural variations.In this study,regional geochemical baselines of heavy metals were established based on core sediment samples collected from Dongzhai Harbor in November 2015.Linear regression analysis was employed to examine the correlations between heavy metals and potential normalized elements.Subsequently,the sediment quality and intensity of pollutant input in the sediments of a mangrove intertidal zone were evaluated with enrichment factor(EF)and excessive influx of heavy metals.The EF values for Cr,Cd,Pb,Zn,and Ni in the study area were all below 1.5,indicating minimal levels of contamination;however,minor Cu contamination was observed in the high tidal flat area due to potential terrestrial inputs.These findings suggest that the overall environmental quality about heavy metals was good within the intertidal zone of mangroves.Moreover,as for the excess fluxes of heavy metals in intertidal sediments,there was consistency between influence and intervention of human activities on sedimentary environment during the selected period when examining variation trends.展开更多
The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the Sout...The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the South Yellow Sea is located at the convergence of these plates,it becomes a pivotal area for understanding the tectonic evolution of East Asia.The characteristics and provenance of clastic rocks of the Middle Permian-the Early Triassic were analyzed and the strata in the Central Uplift including the Qinglong Formation(T_(1)q)and Talung Formation(P_(3)d),consisting of various mudstones and sandstones,were anatomized.Results show that quartz and feldspar are the main diagenetic minerals,while illite and chlorite show signs of secondary alterations.Geochemical imprints indicate a gradual shift in provenance from ancient sedimentary and mafic igneous rocks to intermediate igneous rocks.In the meantime,the tectonic background transformed from continent to continental island arc from the Middle Permian to the Early Triassic.Therefore,we inferred that a soft collision between the North China Plate and the Yangtze Plate likely occurred during the Late Permian,resulted in intensified collision between two plates in the Early Triassic,and shaped the South Yellow Sea.This study provided valuable information on the timing of plate collisions in the South Yellow Sea.展开更多
Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s ...Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s crust.Mud volcanism,as a dynamic manifestation of these processes,contributes CH_(4)emissions that influence the global methane budget and impact marine ecosystems.Although∼2000 CH_(4)-rich mud extrusions have been documented in subduction zones globally,the geological origins and subduction-related geochemical and tectonic mechanisms driving these emissions remain poorly understood.This research examines the Makran subduction zone which hosts one of the world’s largest accretionary wedge and extensive CH_(4)-rich mud extrusions,as a model system.Integrated geochemical,geophysical,and geological observations reveal that thermogenic CH_(4)and clay-rich fluidized muds originate from deeply buried Himalayan turbidites(underthrusted sediments),driven by organic-rich sediment maturation and high fluid overpressure.Key tectonic features,including thrust faults,overburden pressure of wedge-top sediments,normal faults,brittle fractures,and seismicity,facilitate CH_(4)-rich mud extrusions into the hydrosphere and atmosphere.The extruded gases are predominantly CH_(4),with minor C_(2)H_(6),C_(3)H_(8),i-C_(4)H_(10),and n-C_(4)H_(10)while the mud breccia exhibits a chemical composition dominated by SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3),enriched with trace elements(Rb,Zr,and V)and clay minerals,quartz,and carbonates.Geochemical indicators suggest intense chemical weathering and mature sediments classifying the mud breccia as litharenite and sub-litharenite,indicative of deep burial and compaction.These findings model the evolution of CH_(4)-rich mud extrusions through three geological stages:(i)Eocene to Early Miocene pre-thermogenic formation of the CH_(4)-rich source,(ii)Middle Miocene to Pliocene syn-thermogenic CH_(4)and fluidized mud generation,and(iii)Pleistocene to Recent post-thermogenic CH_(4)-rich fluidized mud migration.These findings underscore the critical yet often overlooked role of subduction-related geochemical and tectonic processes in CH_(4)generation and emission,with significant implications for the global CH_(4)budget and marine ecosystems.展开更多
Hydrocarbon contamination from oil spills presents geoenvironmental and geoengineering challenges,notably in Eleme,Nigeria.This study integrates electrical resistivity tomography(ERT),soil total petroleum hydrocarbon(...Hydrocarbon contamination from oil spills presents geoenvironmental and geoengineering challenges,notably in Eleme,Nigeria.This study integrates electrical resistivity tomography(ERT),soil total petroleum hydrocarbon(TPH)analysis,and geotechnical testing for treated spill site monitoring and characterization over six months.Four 100 m ERT lines,L1 to L4,with spacings at 1.5 m,3 m,6 m,9 m,12 m,and 15 m,were established for the first and second sampling phases.Twenty-one soil samples,12 TPH,and 9 mechanical analyses,were obtained from 5 boreholes,BH1 to BH4,for the study site and the BH5 control site across the phases at 0.5 m,3.0 m,and 5.0 m depths along ERT lines.ERT results reveal resistivity reductions averaging 18%in shallow zones of active degradation,correlating with an average 41%TPH-decrease.Specific gravity averaged 2.49 in the spill soils,compared to 2.58 in control samples,reflecting hydrocarbon-induced density reductions of 3.5%.Particle size showed spill soils contained>50%fines,increasing water retention and reducing permeability by 30%.Consolidation tests highlighted increased compressibility,with settlements of 1.89 mm in spill soils versus 1.01 mm in control samples,indicating a 47%increase in settlement from hydrocarbon reduction.Correlation analysis shows slower consolidation at BH3(−0.62 Cv)with moderate settlement increase(0.25),while BH4 exhibits much higher compressibility(0.95)but minimal Cv impact(0.23),indicating increased structural weakness with higher residual TPH.Spill degradation reduced TPH by 19%-64%in shallow zones,with persistent contamination at deeper layers exceeding the regulatory limits,emphasising the need for ongoing monitoring and targeted remediation for long-term stability and sustainability.展开更多
Regional geochemical division is a mapping technique to divide an area into slices where the associations between geochemical elements are relatively simple and uniform. The result of division is expressed on a 2 D ma...Regional geochemical division is a mapping technique to divide an area into slices where the associations between geochemical elements are relatively simple and uniform. The result of division is expressed on a 2 D map. The scheme of regional geochemical division includes non supervised pattern recognition, elementary statistics and factor analysis. A practical example in a gold prospecting area in Jilin, China, and the corresponding explanation are presented. Regional geochemical division is a basic approach to the delineation of the geochemical blocks as well.展开更多
Mineral resources prediction and assessment is one of the most important tasks in geosciences.Geochemical anomalies,as direct indicators of the presence of mineralization,have played a significant role in the search o...Mineral resources prediction and assessment is one of the most important tasks in geosciences.Geochemical anomalies,as direct indicators of the presence of mineralization,have played a significant role in the search of mineral deposits in the past several decades.In the near future,it may be possible to recognize subtle geochemical anomalies through the use of processing of geochemical exploration data using advanced approaches such as the spectrum-area multifractal model.In addition,negative geochemical anomalies can be used to locate mineralization.However,compared to positive geochemical anomalies,there has been limited research on negative geochemical anomalies in geochemical prospecting.In this study,two case studies are presented to demonstrate the identification of subtle geochemical anomalies and the significance of negative geochemical anomalies.Meanwhile,the opportunities and challenges in evaluating subtle geochemical anomalies associated with mineralization,and benefits of mapping of negative anomalies are discussed.展开更多
Crustal recycling at convergent plate boundaries is essential to mantle heterogeneity.However,crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily incorporated in the form of...Crustal recycling at convergent plate boundaries is essential to mantle heterogeneity.However,crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily incorporated in the form of liquid rather than solid phases.The physicochemical property of liquid phases is determined by the dehydration behavior of crustal rocks at the slab-mantle interface in subduction channels.Because of the significant fractionation in incompatible trace elements but the full inheritance in radiogenic isotopes relative to their crustal sources,the production of liquid phases is crucial to the geochemical transfer from the subducting crust into the mantle.In this process,the stability of specific minerals in subducting crustal rocks exerts a primary control on the enrichment of given trace elements in the liquid phases.For this reason,geochemically enriched oceanic basalts can be categorized into two types in terms of their trace element distribution patterns in the primitive mantle-normalized diagram.One is island arc basalts(IAB),showing enrichment in LILE,Pb and LREE but depletion in HFSE such as Nb and Ta relative to HREE,The other is ocean island basalts(OIB),exhibiting enrichment in LILE and LREE,enrichment or non-depletion in HFSE but depletion in Pb relative to HREE.In either types,these basalts show the enhanced enrichment of LILE and LREE with increasing their incompatibility relative to normal mid-ocean ridge basalts(MORB).The thermal regime of subduction zones can be categorized into two stages in both time and space,The first stage is characterized by compressional tectonism at low thermal gradients.As a consequence,metamorphic dehydration of the subducting crust prevails at forearc to subarc depths due to the breakdown of hydrous minerals such as mica and amphibole in the stability field of garnet and rutile,resulting in the liberation of aqueous solutions with the trace element composition that is considerably enriched in LILE,Pb and LREE but depleted in HFSE and HREE relative to normal MORB.This provides the crustal signature for the mantle sources of IAB.The second stage is indicated by extensional tectonism at high thermal gradients,leading to the partial melting of metamorphically dehydrated crustal rocks at subarc to postarc depths.This involves not only the breakdown of hydrous minerals such as amphibole,phengite and allanite in the stability field of garnet but also the dissolution of rutile into hydrous melts.As such,the hydrous melts can acquire the trace element composition that is significantly enriched in LILE,HFSE and LREE but depleted in Pb and HREE relative to normal MORB,providing the crustal signature for the mantle sources of OIB.In either case,these liquid phases would metasomatize the overlying mantle wedge peridotite at different depths,generating ultramafic metasomatites such as serpentinized and chloritized peridotites,and olivine-poor pyroxenites and hornblendites.As a consequence,the crustal signatures are transferred by the liquid phases from the subducting slab into the mantle.展开更多
The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines fro...The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.展开更多
[Objective] The aim was to investigate the effects of soil geochemistry on the quality of winter jujube.[Method]Based on the data of ecological geochemical survey in lower Yellow River Basin,the relevance of the geoch...[Objective] The aim was to investigate the effects of soil geochemistry on the quality of winter jujube.[Method]Based on the data of ecological geochemical survey in lower Yellow River Basin,the relevance of the geochemistry environment in top soils and the quality of winter jujubes was analyzed.[Result]Cd,Ni and other heavy metals in the soil more obviously affected the nutrition of winter jujubes.[Conclusion]B,Mn,MgO,Cd,Zn,K2O and other elements in the root soil played an important role in the enrichment of Cr and Hg of winter jujube fruit.And the absorption of heavy metals in winter jujube root could be interfered by improving fertilization method,to reduce the enrichment of harmful elements in jujube fruit.展开更多
The development of geochemical mapping progressed from local geochemical prospecting through regional geochemical exploration and regional geochemical mapping to national and global geochemical mapping. This paper dis...The development of geochemical mapping progressed from local geochemical prospecting through regional geochemical exploration and regional geochemical mapping to national and global geochemical mapping. This paper discusses the evolution of aims, ideas and methodology of geochemical mapping in Western countries, Russia and China. The sophistication of geochemical mapping methodology will make great contributions to solving resources and environmental problems in the 21^st century.展开更多
基金supported by Croatian Science Foundation Research Project Dinaridic Foreland Basin between Two Eocene Thermal Optima:A Possible Scenario for the Northern Adriatic BREEMECO(No.2019-04-5775)。
文摘Hemipelagic to pelagic(H/P)marls,representing pelitic deposits,accumulated within the foredeep sub-basin of the Dinaric Foreland Basin(northern Neotethyan margin,present-day Croatia)during the Middle to Late Eocene.Syn-sedimentary tectonic movements,paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits.Mineral(clay)assemblages bear signature of prevailing physical weathering with significant illite and chlorite content,but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content.Illite crystallinity varies significantly,and the lowest crystallinity is recorded by the Lutetian samples.Illite chemistry index is always bellow 0.5,being characteristic for Fe-Mg-rich illite.The geochemical records are the most prominent(CIA up to 76,CIW up to 91)for the Istrian Lutetian(42.3-40.5 Ma),but also for Priabonian(35.8-34.3 Ma)samples of Hvar Island.The ICV values(the lowest 1.40 and the highest 10.85)of all studied samples fall above PAAS(ICV=0.85)and point to their chemical immaturity.The Ga/Rb ratios are lower than 0.2 and K_(2)O/Al_(2)O_(3) ratios are also low(0.16-0.22),implying transition between cold and dry,and warm and humid climate,obviously trending among several warming episodes.
基金supported by the National Natural Science Foundation of China(Nos.42530801,42425208)the Natural Science Foundation of Hubei Province(China)(No.2023AFA001)+1 种基金the MOST Special Fund from State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(No.MSFGPMR2025-401)the China Scholarship Council(No.202306410181)。
文摘Geochemical survey data are essential across Earth Science disciplines but are often affected by noise,which can obscure important geological signals and compromise subsequent prediction and interpretation.Quantifying prediction uncertainty is hence crucial for robust geoscientific decision-making.This study proposes a novel deep learning framework,the Spatially Constrained Variational Autoencoder(SC-VAE),for denoising geochemical survey data with integrated uncertainty quantification.The SC-VAE incorporates spatial regularization,which enforces spatial coherence by modeling inter-sample relationships directly within the latent space.The performance of the SC-VAE was systematically evaluated against a standard Variational Autoencoder(VAE)using geochemical data from the gold polymetallic district in the northwestern part of Sichuan Province,China.Both models were optimized using Bayesian optimization,with objective functions specifically designed to maintain essential geostatistical characteristics.Evaluation metrics include variogram analysis,quantitative measures of spatial interpolation accuracy,visual assessment of denoised maps,and statistical analysis of data distributions,as well as decomposition of uncertainties.Results show that the SC-VAE achieves superior noise suppression and better preservation of spatial structure compared to the standard VAE,as demonstrated by a significant reduction in the variogram nugget effect and an increased partial sill.The SC-VAE produces denoised maps with clearer anomaly delineation and more regularized data distributions,effectively mitigating outliers and reducing kurtosis.Additionally,it delivers improved interpolation accuracy and spatially explicit uncertainty estimates,facilitating more reliable and interpretable assessments of prediction confidence.The SC-VAE framework thus provides a robust,geostatistically informed solution for enhancing the quality and interpretability of geochemical data,with broad applicability in mineral exploration,environmental geochemistry,and other Earth Science domains.
基金the support from the National Natural Science Foundation of China(Nos.52279103,52379103)the Natural Science Foundation of Shandong Province(No.ZR2023YQ049)。
文摘Geological analysis,despite being a long-term method for identifying adverse geology in tunnels,has significant limitations due to its reliance on empirical analysis.The quantitative aspects of geochemical anomalies associated with adverse geology provide a novel strategy for addressing these limitations.However,statistical methods for identifying geochemical anomalies are insufficient for tunnel engineering.In contrast,data mining techniques such as machine learning have demonstrated greater efficacy when applied to geological data.Herein,a method for identifying adverse geology using machine learning of geochemical anomalies is proposed.The method was identified geochemical anomalies in tunnel that were not identified by statistical methods.We by employing robust factor analysis and self-organizing maps to reduce the dimensionality of geochemical data and extract the anomaly elements combination(AEC).Using the AEC sample data,we trained an isolation forest model to identify the multi-element anomalies,successfully.We analyzed the adverse geological features based the multi-element anomalies.This study,therefore,extends the traditional approach of geological analysis in tunnels and demonstrates that machine learning is an effective tool for intelligent geological analysis.Correspondingly,the research offers new insights regarding the adverse geology and the prevention of hazards during the construction of tunnels and underground engineering projects.
文摘Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geological features, it holds crucial information for understanding the evolution of the Saharan Meta craton (central Africa), which remains poorly studied. One of the objectives is to map the formations Precambrian age in Southeastern Chad. Based on the petrographic and geochemical results, we identified granitoids of pan-African age (biotite granite, aplite granite and pegmatite granite). This Precambrian basement is covered with sedimentary formations (clays, argillites, lateritic cuirasses, etc.). The mineral assemblage is characteristic of acid rocks. Geochemistry reveals rocks with a high SiO2 range (62% - 77%) giving sub-alkaline to calc-alkaline acid rocks with high k (4.62% to 6.39%). The granitoids are classified as S-type hyperaluminous granites. This classification is supported by the presence of peraluminous minerals (e.g., muscovite) within the Iro granitoids, which also have high (>1%). Geochemical variation within the granites is largely due to extensive crystal fractionation. The Pattern of REEs normalized to the primitive mantle shows a pronounced negative Eu anomaly, reflecting the crystallization process and fractional crystallization of plagioclase in the rock, and a positive Yb anomaly. The role of plagioclase fractionation was relatively major during the earlier intrusive stages (consistent with the presence of Eu anomalies) and slightly increased, together with biotite and K-feldspar fractionation, during the later (granitic) rock crystallization. The Pattern of the spider normalized to MORBs shows two pronounced negative anomalies in TiO2 and Cs and a slight negative anomaly in Ba. The loss of Ba, Ti and Cs may be caused by the plagioclase fractionation, apatite and ilmenite crystal. The Ba anomaly is also controlled by the presence of K-feldspar and mica. The observed Ti anomalies are due to the fractionation of magnetite indicating a subduction environment (or remelting of a source from a subduction environment).
基金the National Natural Science Foundation of China(Nos.42206076,42476078)the National Program on Global Change and Air-Sea Interaction(No.GASI-02-SCSCJB01)the China-Malaysia Cooperation Project‘Effect on variability of seasonal monsoon on sedimentary process in Peninsular Malaysia waters’。
文摘The Malacca Strait(MS)is a vital conduit for the exchange of water and sediment between the Indian Ocean and the Pacific Ocean,serving as a critical‘gateway'for sediment transport.Here,we present the geochemical characteristics of surface sediments in the MS to elucidate the relationship between terrestrial material inputs and modern oceanic dynamic transport processes in the strait.The results reveal that the MS can be divided into three distinct geochemical provinces.ProvinceⅠ,located in the central region of the strait,is characterized by residual deposits.The preservation of these residual deposits can be attributed to the restricted sediment supply and the relatively weaker modern sedimentary hydrodynamic conditions.ProvinceⅡ,situated to the north of ProvinceⅠ,exhibits provenance differences between its southern and northern regions.The northern region is primarily supplied by sediments originating from the eastern shelf of the Andaman Sea,whereas sediments derived from Sumatra and the Sunda Shelf are predominantly deposited in the southern part of ProvinceⅡ.ProvinceⅢextends along the western coast of the Malaysian Peninsula,with sediments primarily sourced from the Malaysian Peninsula and the Sunda Shelf,while contributions from Sumatra and the eastern shelf of the Andaman Sea are negligible.River sediments from the Malaysian Peninsula and Sumatra are transported northwestward along their respective coasts by prevailing currents,which also facilitate the transportation of Sunda Shelf sediments within the strait,while sediments from the eastern shelf of the Andaman Sea are delivered to the MS via southward coastal currents during the southwest monsoon period.The southward currents and well-developed eddies potentially impede the northward transport of sediments from the Sunda Shelf and restrict the distribution of Andaman Sea sediments within the strait.This study substantially enhances the understanding of source-to-sink processes in the Indo-Pacific region.
基金funded by the Major Research Plan of the National Natural Science Foundation of China(92162323)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0430101)Guizhou Provincial Science and Technology Projects No.ZK[2023]052.
文摘Lithium is a critical strategic metal with signifi-cant reserves in pegmatites,serving as the primary source for global Li production.Apatite has attracted increasing attention as an indicator in petrogenesis studies and for the exploration of ore deposits.In this study,we investigated the volatile compositions and major and trace elements of apatite from the Qiongjiagang pegmatite-type lithium deposit in Himalaya.Apatite derived from spodumene pegmatite exhibits relatively constant and high total rare earth element(ΣREE+Y)concentrations,ranging from 5899 to 8540 ppm.In contrast,apatite in barren pegmatite displays evidently lower(ΣREE+Y)concentrations,varying between 1345 and 3095 ppm.The REE patterns of apatite in spodumene pegmatite generally exhibit a flat shape[(La/Yb)N=1.55-2.15)],with distinctively negative Eu anomalies(Eu_(N)/Eu_(N)^(*)=0.14-0.22),slightly positive Ce anomalies(Ce_(N)/Ce_(N)^(*)=1.03-1.13),and low Y/Ho ratios(28-30).By contrast,apatite in barren pegmatite shows middle rare earth element(MREE)-depleted downward-convex patterns[(La/Yb)N=1.99-20.4)],strongly negative Eu anomalies(Eu_(N)/Eu_(N)^(*)=0.01-0.14),slightly positive Ce anomalies(Ce_(N)/Ce_(N)^(*)=1.10-1.24),and high Y/Ho ratios(30-55,with an average of 50).Overall,the high concentrations ofΣREE(and Y)and low Th/U and Y/Ho ratios can serve as diagnostic indicators to distinguish apatite in spodumene pegmatite from that in barren pegmatite.Furthermore,the flat REE pattern may represent a common feature of apatite from lithium deposits.Differences in the Ce and Eu anomalies between apatite from these two kinds of pegmatites likely reflect formation under different redox conditions.Consequently,based on calculations derived from apatite volatile compositions,the melt associated with spodumene pegmatite may contain higher water content compared to that of the barren one.Therefore,the mineralized pegmatite system may incorporate substantial amounts of H_(2)O-rich fluids,which play a crucial role in lithium mineralization.
基金supported by the research grant from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2019-02)。
文摘Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.
基金Supported by the National Natural Science Foundation of China(No.U2244222).
文摘This study selects geochemical data of basalts from different seamounts in the Mid-Pacific Mountains province and conducts analyses of major and trace elements as well as Sr-Nd-Pb isotopes to explore the tectonic evolution,petrogenesis,and mantle-source magama characteristics of the Mid-Pacific Mountains.The basalts from the Mid-Pacific Mountains are predominantly alkali basalts,rich in alkalies,and changing in potassium.They exhibit geochemical features of ocean island basalts(OIB),with distinct fractionation between light and heavy rare-earth elements and a pronounced Ce negative anomaly(δ_(Ce)=0.16–1.10,average 0.84),along with enrichment in large ion lithophile elements(LILEs).The Mid-Pacific Mountains are intraplate ocean island basalts formed by mantle plume(hotspot)activity,originating mainly from an enriched mantle magma source region,and most of them have undergone low degree of partial melting and a certain degree of crystalline differentiation,with negligible contamination from oceanic crust materials.The Mid-Pacific Mountains exhibit ratios of^(87)Sr/^(86)Sr(i)(0.702733–0.704313,average 0.703452)and^(143)Nd/^(144)Nd(i)(0.512698–0.512996,average 0.512846)which are close to the HIMU mantle endmember,and ratios of 206Pb/204Pb(18.953–19.803),^(207)Pb/^(204)Pb(15.54–15.62)and^(208)Pb/^(204)Pb(38.813–39.514)which are close to the EMII mantle end-member.Combined with the isotopic geochemical characteristics in the West Pacific Seamounts province,the basalts from the Mid-Pacific Mountains were considered to represent a certain proportion of mixing mantle end-members between the HIMU and EMII,possibly formed by the mixing of the HIMU superplume in the South Pacific hotspot region with the EMII secondary mantle plume in the transition zone during their ascent.
文摘The Langrial iron ore deposits,located in the villages of Dubran and Darkot in Hazara,Pakistan,were evaluated using remote sensing,magnetic,and geochemical investigations.Data from ASTER,Landsat-8,and Sentinel-2 satellites were utilized and processed through techniques such as band ratio analysis,band compositing,and NDVI masking to reduce vegetation effects and to delineate various lithological units and mineralogical signatures within the study area.Magnetic anomalies revealed multiple levels of iron mineralization,with the hematite zone showing the most significant potential for high-grade iron ore.Geochemical analyses confirmed the presence of iron,along with minerals such as chromium,calcium,magnesium,and lead.In Dubran,mean iron concentrations are recorded at 370.94 mg/kg,whereas in Darkot,they reach up to 2052 mg/kg.The integration of remote sensing,magnetic,and geochemical data delineates key mineralized zones in the various parts of the study area.This research highlights the importance of combining geophysical and geochemical methodologies to refine mineral exploration efforts.The findings enhance our understanding of the Langrial iron ore deposits and highlight their economic potential for sustainable mining practices.This study will contribute to meeting the growing demand for iron ore resources and reducing Pakistan's reliance on imports,thereby promoting the sustainable development of local industries.
基金supported by the National Natural Science Foundation of China(41925014).
文摘The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and significantly variable gas contents of the drilled shales.Excitingly,the first major breakthrough in deep and ultra-deep Lower Cambrian shale gas was made recently in the well Z201 in the southern Sichuan Basin,with a gas yield exceeding 73×10^(4)m^(3)/d.The success of well Z201 provides a favorable geological case to reveal the distinct enrichment mechanism of deep and ultra-deep Lower Cambrian shale gas.In this study,at drilling site of well Z201,fresh shale core samples with different gasin-place contents were collected,and their geochemical,pore development and water-bearing characteristics were analyzed systematically.The results showed that the Z201 organic-rich shales reached an overmature stage,with an average Raman maturity of 3.70%.The Z201 shales with high gas-in-place contents are mainly located in the Qiongzhusi 12section and the upper Qiongzhusi 11section,with an average gas-in-place content of 10.08 cm^(3)/g.Compared to the shales with low gas-in-place contents,the shales with high gas-in-place contents exhibit higher total organic carbon contents,greater porosities,and lower water saturations,providing more effective pore spaces for shale gas enrichment.The effective pore structures of the deep and ultra-deep Lower Cambrian shales are the primary factors affecting their gas-in-place contents.Similar to the shales with high gas-in-place contents of well Z201,the deep and ultra-deep Lower Cambrian shales in the Mianyang-Changning intracratonic sag,especially in the Ziyang area,generally developed in deep-water shelf facies with high total organic carbon contents and thick sedimentary thickness,providing favorable conditions for the development and preservation of effective pores.Therefore,they are the most promising targets for Lower Cambrian shale gas exploration.
基金Supported by the Project of Investigation on the Background and Quality of Representative Intertidal Sediments in China and Compilation of Atlas,Ministry of Science and Technology of the People’s Republic of China(No.2014FY210600)the National Natural Science Foundation of China(No.41807247)。
文摘The intertidal zone of mangroves has a significant impact on the ecological environment by serving as a crucial habitat for a wide range of organisms.When assessing heavy metal contamination in sediments within this zone,it is essential to establish a regional geochemical baseline that accounts for natural variations.In this study,regional geochemical baselines of heavy metals were established based on core sediment samples collected from Dongzhai Harbor in November 2015.Linear regression analysis was employed to examine the correlations between heavy metals and potential normalized elements.Subsequently,the sediment quality and intensity of pollutant input in the sediments of a mangrove intertidal zone were evaluated with enrichment factor(EF)and excessive influx of heavy metals.The EF values for Cr,Cd,Pb,Zn,and Ni in the study area were all below 1.5,indicating minimal levels of contamination;however,minor Cu contamination was observed in the high tidal flat area due to potential terrestrial inputs.These findings suggest that the overall environmental quality about heavy metals was good within the intertidal zone of mangroves.Moreover,as for the excess fluxes of heavy metals in intertidal sediments,there was consistency between influence and intervention of human activities on sedimentary environment during the selected period when examining variation trends.
基金Supported by the National Natural Science Foundation of China(No.U 2344221)。
文摘The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the South Yellow Sea is located at the convergence of these plates,it becomes a pivotal area for understanding the tectonic evolution of East Asia.The characteristics and provenance of clastic rocks of the Middle Permian-the Early Triassic were analyzed and the strata in the Central Uplift including the Qinglong Formation(T_(1)q)and Talung Formation(P_(3)d),consisting of various mudstones and sandstones,were anatomized.Results show that quartz and feldspar are the main diagenetic minerals,while illite and chlorite show signs of secondary alterations.Geochemical imprints indicate a gradual shift in provenance from ancient sedimentary and mafic igneous rocks to intermediate igneous rocks.In the meantime,the tectonic background transformed from continent to continental island arc from the Middle Permian to the Early Triassic.Therefore,we inferred that a soft collision between the North China Plate and the Yangtze Plate likely occurred during the Late Permian,resulted in intensified collision between two plates in the Early Triassic,and shaped the South Yellow Sea.This study provided valuable information on the timing of plate collisions in the South Yellow Sea.
基金funded by the National Natural Science Foundation of China(Grants No.92058213 and No.U22A20581)the Specific Research Fund of the Innovation Platform for Academicians of Hainan Province(Grant No.YSPTZX202204)key R&D projects of Hainan Province(ZDYF2024GXJS022).
文摘Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s crust.Mud volcanism,as a dynamic manifestation of these processes,contributes CH_(4)emissions that influence the global methane budget and impact marine ecosystems.Although∼2000 CH_(4)-rich mud extrusions have been documented in subduction zones globally,the geological origins and subduction-related geochemical and tectonic mechanisms driving these emissions remain poorly understood.This research examines the Makran subduction zone which hosts one of the world’s largest accretionary wedge and extensive CH_(4)-rich mud extrusions,as a model system.Integrated geochemical,geophysical,and geological observations reveal that thermogenic CH_(4)and clay-rich fluidized muds originate from deeply buried Himalayan turbidites(underthrusted sediments),driven by organic-rich sediment maturation and high fluid overpressure.Key tectonic features,including thrust faults,overburden pressure of wedge-top sediments,normal faults,brittle fractures,and seismicity,facilitate CH_(4)-rich mud extrusions into the hydrosphere and atmosphere.The extruded gases are predominantly CH_(4),with minor C_(2)H_(6),C_(3)H_(8),i-C_(4)H_(10),and n-C_(4)H_(10)while the mud breccia exhibits a chemical composition dominated by SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3),enriched with trace elements(Rb,Zr,and V)and clay minerals,quartz,and carbonates.Geochemical indicators suggest intense chemical weathering and mature sediments classifying the mud breccia as litharenite and sub-litharenite,indicative of deep burial and compaction.These findings model the evolution of CH_(4)-rich mud extrusions through three geological stages:(i)Eocene to Early Miocene pre-thermogenic formation of the CH_(4)-rich source,(ii)Middle Miocene to Pliocene syn-thermogenic CH_(4)and fluidized mud generation,and(iii)Pleistocene to Recent post-thermogenic CH_(4)-rich fluidized mud migration.These findings underscore the critical yet often overlooked role of subduction-related geochemical and tectonic processes in CH_(4)generation and emission,with significant implications for the global CH_(4)budget and marine ecosystems.
基金funded by the Petroleum Technology Development Fund(PTDF),Nigeria.(Award No.:PTDF/ED/OSS/PHD/NOA/1714/20).
文摘Hydrocarbon contamination from oil spills presents geoenvironmental and geoengineering challenges,notably in Eleme,Nigeria.This study integrates electrical resistivity tomography(ERT),soil total petroleum hydrocarbon(TPH)analysis,and geotechnical testing for treated spill site monitoring and characterization over six months.Four 100 m ERT lines,L1 to L4,with spacings at 1.5 m,3 m,6 m,9 m,12 m,and 15 m,were established for the first and second sampling phases.Twenty-one soil samples,12 TPH,and 9 mechanical analyses,were obtained from 5 boreholes,BH1 to BH4,for the study site and the BH5 control site across the phases at 0.5 m,3.0 m,and 5.0 m depths along ERT lines.ERT results reveal resistivity reductions averaging 18%in shallow zones of active degradation,correlating with an average 41%TPH-decrease.Specific gravity averaged 2.49 in the spill soils,compared to 2.58 in control samples,reflecting hydrocarbon-induced density reductions of 3.5%.Particle size showed spill soils contained>50%fines,increasing water retention and reducing permeability by 30%.Consolidation tests highlighted increased compressibility,with settlements of 1.89 mm in spill soils versus 1.01 mm in control samples,indicating a 47%increase in settlement from hydrocarbon reduction.Correlation analysis shows slower consolidation at BH3(−0.62 Cv)with moderate settlement increase(0.25),while BH4 exhibits much higher compressibility(0.95)but minimal Cv impact(0.23),indicating increased structural weakness with higher residual TPH.Spill degradation reduced TPH by 19%-64%in shallow zones,with persistent contamination at deeper layers exceeding the regulatory limits,emphasising the need for ongoing monitoring and targeted remediation for long-term stability and sustainability.
文摘Regional geochemical division is a mapping technique to divide an area into slices where the associations between geochemical elements are relatively simple and uniform. The result of division is expressed on a 2 D map. The scheme of regional geochemical division includes non supervised pattern recognition, elementary statistics and factor analysis. A practical example in a gold prospecting area in Jilin, China, and the corresponding explanation are presented. Regional geochemical division is a basic approach to the delineation of the geochemical blocks as well.
基金supported by the National Natural Science Foundation of China(No.41772344)。
文摘Mineral resources prediction and assessment is one of the most important tasks in geosciences.Geochemical anomalies,as direct indicators of the presence of mineralization,have played a significant role in the search of mineral deposits in the past several decades.In the near future,it may be possible to recognize subtle geochemical anomalies through the use of processing of geochemical exploration data using advanced approaches such as the spectrum-area multifractal model.In addition,negative geochemical anomalies can be used to locate mineralization.However,compared to positive geochemical anomalies,there has been limited research on negative geochemical anomalies in geochemical prospecting.In this study,two case studies are presented to demonstrate the identification of subtle geochemical anomalies and the significance of negative geochemical anomalies.Meanwhile,the opportunities and challenges in evaluating subtle geochemical anomalies associated with mineralization,and benefits of mapping of negative anomalies are discussed.
基金supported by funds from the Chinese Academy of Sciences(XDB18020303)the Chinese Ministry of Science and Technology(2015CB856100)the National Natural ScienceFoundation of China(41590620)
文摘Crustal recycling at convergent plate boundaries is essential to mantle heterogeneity.However,crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily incorporated in the form of liquid rather than solid phases.The physicochemical property of liquid phases is determined by the dehydration behavior of crustal rocks at the slab-mantle interface in subduction channels.Because of the significant fractionation in incompatible trace elements but the full inheritance in radiogenic isotopes relative to their crustal sources,the production of liquid phases is crucial to the geochemical transfer from the subducting crust into the mantle.In this process,the stability of specific minerals in subducting crustal rocks exerts a primary control on the enrichment of given trace elements in the liquid phases.For this reason,geochemically enriched oceanic basalts can be categorized into two types in terms of their trace element distribution patterns in the primitive mantle-normalized diagram.One is island arc basalts(IAB),showing enrichment in LILE,Pb and LREE but depletion in HFSE such as Nb and Ta relative to HREE,The other is ocean island basalts(OIB),exhibiting enrichment in LILE and LREE,enrichment or non-depletion in HFSE but depletion in Pb relative to HREE.In either types,these basalts show the enhanced enrichment of LILE and LREE with increasing their incompatibility relative to normal mid-ocean ridge basalts(MORB).The thermal regime of subduction zones can be categorized into two stages in both time and space,The first stage is characterized by compressional tectonism at low thermal gradients.As a consequence,metamorphic dehydration of the subducting crust prevails at forearc to subarc depths due to the breakdown of hydrous minerals such as mica and amphibole in the stability field of garnet and rutile,resulting in the liberation of aqueous solutions with the trace element composition that is considerably enriched in LILE,Pb and LREE but depleted in HFSE and HREE relative to normal MORB.This provides the crustal signature for the mantle sources of IAB.The second stage is indicated by extensional tectonism at high thermal gradients,leading to the partial melting of metamorphically dehydrated crustal rocks at subarc to postarc depths.This involves not only the breakdown of hydrous minerals such as amphibole,phengite and allanite in the stability field of garnet but also the dissolution of rutile into hydrous melts.As such,the hydrous melts can acquire the trace element composition that is significantly enriched in LILE,HFSE and LREE but depleted in Pb and HREE relative to normal MORB,providing the crustal signature for the mantle sources of OIB.In either case,these liquid phases would metasomatize the overlying mantle wedge peridotite at different depths,generating ultramafic metasomatites such as serpentinized and chloritized peridotites,and olivine-poor pyroxenites and hornblendites.As a consequence,the crustal signatures are transferred by the liquid phases from the subducting slab into the mantle.
基金supported by "Technology of Comprehensive Prospecting and Exploitability for Elements in Crisis Mines" (Grant No. 2008EG115074)a special fund managed by the Ministry of Science and Technology for technical R&D of scientific research institutions, and the Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences
文摘The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.
基金Supported by China Geological Survey Project(121210310306)~~
文摘[Objective] The aim was to investigate the effects of soil geochemistry on the quality of winter jujube.[Method]Based on the data of ecological geochemical survey in lower Yellow River Basin,the relevance of the geochemistry environment in top soils and the quality of winter jujubes was analyzed.[Result]Cd,Ni and other heavy metals in the soil more obviously affected the nutrition of winter jujubes.[Conclusion]B,Mn,MgO,Cd,Zn,K2O and other elements in the root soil played an important role in the enrichment of Cr and Hg of winter jujube fruit.And the absorption of heavy metals in winter jujube root could be interfered by improving fertilization method,to reduce the enrichment of harmful elements in jujube fruit.
文摘The development of geochemical mapping progressed from local geochemical prospecting through regional geochemical exploration and regional geochemical mapping to national and global geochemical mapping. This paper discusses the evolution of aims, ideas and methodology of geochemical mapping in Western countries, Russia and China. The sophistication of geochemical mapping methodology will make great contributions to solving resources and environmental problems in the 21^st century.
