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1.
The paper discusses results of the lithogeochemical examination of recent bottom sediments in the lower course of the Severnaya Dvina River and White Sea. It has been established that the average concentration of several trace elements (Hf, Sc, Co, Y, Ni, V, Cr, Zr, Ba, and others) therein correlates with the content of the silt-pelite fraction. Maximal concentrations of the majority of above elements are confined to the silty-clayey sediments at the Basin/Dvina Bay boundary. They localized near the coastal zone only for some clastophile (Zr, Cr, and others). Typical values of the hydrolyzate module, chemical index of alteration, and Al2O3/SiO2 ratio in the aleuropelitic and pelitic sediments of the Severnaya Dvina River delta, Dvina Bay, and the Dvina Bay Basin boundary suggest that these sediments are confined to sufficiently cold climate settings. Data points of sediment composition in discriminant paleotectonic diagrams are scattered over a large field probably due to high contents of the weakly weathered plagioclases, micas, and amphiboles, as well as the hydrogenic process promoting the accumulation of Fe and Mn. The PAAS-normalized spectra of rare earth elements (REE) in bottom sediments of the Pinega and Severnaya Dvina rivers, marginal filter of the latter river, Dvina Bay, and the Dvina Bay Basin boundary are similar to the REE distribution in clayey rocks of the ancient platform cover (except for a slight positive Eu anomaly). The REE systematics and distribution pattern of compositional data points of recent bottom sediments in the GdN/YbN-Eu/Eu* and Eu/Eu*-Cr/Th diagrams and values of several indicator ratios of trace elements suggest that the studied rocks were formed by the mixing of clastic materials from geochemically contrast provenances: northwestern provenance (Kola-Karelia geoblock), which is mostly composed of the Archean and Early Proterozoic crystalline complexes, and the southeastern provenance (northwestern periphery of the Mezen syncline), which is almost totally composed of Phanerozoic sedimentary rocks. The latter provenance likely played a crucial role in the geochemical signature of recent bottom sediments over a significant area of the White Sea.  相似文献   

2.
Dongping Lake area, located in the lower reaches of Yellow River, is an ideal place to study the changes of modern river and lake sedimentary environment. The sediment samples of Dawen River, Yellow River, and Dongping Lake were collected, and the major elements, trace elements and organic matter geochemical composition of the samples were analyzed. Cluster analysis, characteristic element ratio method and graphic method were used to explore the geochemical characteristics of sediments and their environmental implication. The results show that the contents of SiO_2, Na_2O, TiO_2 and Zr in sediments of Dawen River and Yellow River are relatively high, and the contents of iron and manganese oxides, organic matter, CaO, P_2O_5 and Sr in lake sediments are relatively high. That reveals the differences of sedimentary environments between the rivers and the lake. The contents of Sr and Zr in Dawen River are affected by the rapid migration of clastic materials in the upstream carbonate source area during the flood season; the δCe,ΣREE and REE's ratios in the sediments of the Yellow River reflect the influence of the Loess source; and the distribution of elements changes along the flow direction during the flood season. The characteristics of p H, element composition and LREE HREE fractionation of the lake sediments indicate that the sediment source is complex, and the lake environment is affected by the flood season. The study shows that the geochemical content and its variation characteristics of sediments effectively reveal the sedimentary environment, material composition and characteristics of flood season of rivers and the lake in the study area.  相似文献   

3.
The aim of this paper is to study the REE geochemistry of the Shenzhen Bay (SZB) and Dapeng Bay(DPB) modern sediments, discuss their REE distribution patterns, reveal the REE geochemical difference between the two bays which share the same material source but are deposited in different sedimentary environments, and expound their dynamic changes.It can be concluded that the SZB and DPB sediments are essentially of continental source.Their REE distribution patterns are quite different from those of Pacific pelagic sediments, but are very similar to those of South Chi-na granites.Because of different sedimentary environments prevailing in the SZB and DPB, some REE fractionation would have taken place in the sediments of the two bays.  相似文献   

4.
Study of the element composition of ten samples of modern terrigenous and carbonate sediments from the northern part of the Caspian Sea by the ICP-MS method showed that these sediments were enriched in sulfur, nonferrous metals, and some related minor elements including Se, Te, Re, and others in comparison with the average composition of sedimentary rocks. It is assumed that local hydrothermal seeps similar to those known on the Cheleken Peninsula and which may be formed in other areas of this tectonically active zone are the sources of these elements. In addition, such a composition of sediments may indicate the sporadic contamination of bottom water with hydrogen sulfide, which has been observed in areas of the South and Middle Caspian by many researchers.  相似文献   

5.
Thirty-eight sediment samples from 15 primary rivers on Taiwan were retrieved to characterize the rare earth element (REE) signature of fluvial fine sediment sources. Compared to the three large rivers on the Chinese mainland, distinct differences were observed in the REE contents, upper continental crust normalized patterns and fractionation factors of the sediment samples. The average REE concentrations of the Taiwanese river sediments are higher than those of the Changjiang and Huanghe, but lower than the Zhujiang. Light rare earth elements (LREEs) are enriched relative to heavy rare earth elements (HREEs) with ratios from 7.48 to 13.03. We found that the variations in (La/Lu)UCC–(Gd/Lu)UCC and (La/Yb)UCC–(Gd/Yb)UCC are good proxies for tracing the source sediments of Taiwanese and Chinese rivers due to their distinguishable values. Our analyses indicate that the REE compositions of Taiwanese river sediments were primarily determined by the properties of the bedrock, and the intensity of chemical weathering in the drainage areas. The relatively high relief and heavy rainfall also have caused the REEs in the fluvial sediments from Taiwan to be transported to the estuaries down rivers from the mountains, and in turn delivered nearly coincidently to the adjacent seas by currents and waves. Our studies suggest that the REE patterns of the river sediments from Taiwan are distinguishable from those from the other sources of sediments transported into the adjacent seas, and therefore are useful proxies for tracing the provenances and dispersal patterns of sediments, as well as paleoenvironmental changes in the marginal seas.  相似文献   

6.
A study of two classes of hydrocarbons (HCs)—aliphatic and polycyclic aromatic—in suspended matter of the surface waters and bottom sediments of the Northern and Middle Caspian Sea (R/V Nikifor Shurekov, October 2015) is described. It has been determined that oil pollution transported by river runoff and fluid streams flowing from sedimentary formations in the northeastern part are the main sources of hydrocarbons in the river–sea boundaries of the Volga, Terek, and Sulak rivers.  相似文献   

7.
Rare earth elements (REE) concentrations of Archean and Proterozoic chemical sediments are commonly used as proxies to study secular trends in the geochemistry of Precambrian seawater. In addition, similarities in the REE signatures of Archean chemical sediments and modern seawater have led researchers to argue that some Archean rocks originated as biochemical precipitates (i.e., microbial carbonates) in shallow marine (e.g., peritidal) environments. However, terrestrial waters, including river water and groundwater, also commonly exhibit REE fractionation patterns that resemble modern seawater. Here, we present the seawater-like REE data for groundwaters from central México as additional evidence that these patterns are not unique to the marine environment. The shale-normalized REE patterns of the groundwaters are compared to those of modern seawater (open ocean and nearshore), Holocene reefal microbial carbonates and corals, and Archean chemical sediments using statistical means (i.e., ANOVA and Wilcoxon analyses) in order to quantify the similarities and/or differences in the REE patterns. Shale-normalized (SN) Ce anomalies and measures of REE fractionation [i.e., (La/Yb)SN, (Pr/Yb)SN, (Nd/Yb)SN, and (Gd/Yb)SN] of the central México groundwater samples are statistically indistinguishable from those of modern seawater. Moreover, except for differences in the Ce anomalies, which are lacking in Archean chemical sediments, the REE patterns of the central México groundwaters are also statistically similar to REE patterns of Archean chemical sediments, especially those of the 3.45 Ga Strelley Pool Chert. Consequently, we suggest that without additional information, it may be premature to unequivocally conclude that Archean chemical sediments record REE signatures of an Archean ocean.  相似文献   

8.
A systematic study of the granulometric properties and the occurrence and distribution of rare earth elements (REE) within surface sediments from ten bays situated along the coast of Southeast China has facilitated a more rigorous understanding of constraints on sediment provenance in the area. The results show that REE concentrations are similar within a single bay, but vary considerably (133.58–251.77 mg/kg) among the bays. The chondrite-normalized distribution patterns show the typical enrichment of light REEs (LREEs: La–Eu) relative to heavy REEs (HREEs: Gd–Lu), and an apparent depletion of Eu, which is diagnostic of a terrigenous sediment source. Obvious enrichments of the middle REEs (MREEs: Sm–Ho) in the PAAS-normalized (Post-Archean Australian Shale) distribution patterns of these bay sediments are similar to results reported from large rivers in China. Comparing the REE composition of the bay sediments with those of adjoining fluvial sediments and with the bedrock of the surrounding drainage basins, the latter are indicated as the dominant sediment source. The uniform REE distribution patterns, and MREE enrichments, prove that the sediments are derived from the material transported by the streams and rivers that discharge into the bays.  相似文献   

9.
Doklady Earth Sciences - The systematics of REE, Sc, Cr, Zr, and Th in silty-pelitic and pelitic surface bottom sediments sampled during cruises 71, 75, 77, and 80 of the R/V Akademik Mstislav...  相似文献   

10.
REE示踪沉积物物源研究进展   总被引：101，自引：0，他引：101  
ＲＥＥ作为一种重要的沉积物物源示踪剂运用很广。在介绍了ＲＥＥ性质的基础上，对海水、河水、沉积岩、河流及边缘海沉积物中的ＲＥＥ元素丰度与配分模式特征进行了深入综述，概述了影响和控制ＲＥＥ丰度、模式及分馏特征的主要因素；论述了ＲＥＥ的物泊示踪意义以及在国内外应用情况与存在问题：源岩风化对ＲＥＥ分馏的影响；颗粒运及沉积时水动力分选对ＲＥＥ分馏可能造成的影响，即不同粒级中的ＲＥＥ不同的丰度与配分模式和碎屑  相似文献   

11.
This paper deals with the REE geochemical characteristics of Permian-Triassic marine carbonate rocks in Guizhou Province.It is found that there are two broad categories of strati-graphic units in the region studied in accordance with their ΣREE contents and REE distribu-tion patterns: one is characterized by LREE enrichment and slight Ce depletion,with the REE distribution patterns similar to those of North American shales,and the other featrures relative HREE enrichment and relatively remarkable Ce depletion,with the REE distribution patterns close to those of pelagic sediments.In terms of their different ΣREE contents,five types of stratigraphic units can be distinguished.Incorporation of detrital minerals,REE complexing ca-pability,oxidation-reduction conditions of the media are the main factors affecting the REE com-position and REE distribution patterns of marine carbonate rocks in the region studied.In the light of REE geochemical characteristics of carbonate rocks,coupled with sedimentary facies analysis,this paper discusses the characteristics of the Permian-Triassic marine sedimentary environment in Guizhou Province and its evolutional rules.  相似文献   

12.
REE geochemical studies of surficial sediment samples from the Yellow Sea of China have shown:(1)The average content of RE2O3 in the Yellow Sea sediments is 175 ppm,close to that in the East China Sea sediments.The REE distribution patterns in the Yellow Sea sediments are also similar to anomalies.These REE characteristics are typical of the continental crust.(2)The contents of REE are controlled mainly by the sediment grain size,i.e.,REE contents increase gradually with decreasing sediment grain size.REE are present mainly in clay minerals.In addition,REE contents are controlled obviously by heavy minerals.REE abundances in heavy minerals are much greater than those in light minerals.(3)Correlation analysis shows that REE have a close relationship with siderophile elements,especially Ti,which has the largest correlation coefficient relative to REE.Terrigenous clastic materials subjected to weathering and transport are suggested to be the main source of REE in the Yellow Sea sediments.  相似文献   

13.
Geochemical studies of the ecosystems of 184 Siberian lakes in three largest zones of northern Asia (humid, arid, and semiarid) and in mountainous area were carried out. The contents of natural radionuclides, radiocesium, and rare-earth elements in conjugate components of the systems and the types of the main sources of the bottom sediment material have been determined.Dating of the bottom sediments was made by the activity of radioisotopes 137Cs and 210Pb, which permitted estimation of the sedimentation rates in lakes in different regions of Siberia: 0.35 cm/year in the south and 0.25–0.3 cm/year in the north.Six main ions have been determined in the waters of the studied lakes: Ca2+, Mg2+, Na+, HCO3?, SO42?, and Cl?. The distribution of natural radionuclides in the stratified sections of bottom sediments of Siberian lakes evidences the stable sedimentation and characterizes their contents in the soils of water-catchment areas, which can be considered background contents there. Sediments enriched in organic matter have higher concentrations of U and lower ones of Th and K. The Th/K ratio in the studied bottom sediments is the same as in the soils. The Th/U ratios are somewhat lower than those in the soils because U is accumulated by chemogenic and organic components. The overall 137Cs pollution of bottom sediments of Siberian lakes is close to the global background (40 mCi /km2 in 2000), but in the Altai Territory and Buryatia and Altai Republics it is twice higher. The uneven areal and temporal distribution of residual radiocesium is observed not only in the lacustrine sediments but also in the lake water areas. The REE patterns of bottom sediments of different mineral types are similar to those of continental crust and clays of the Russian Platform, though organogenic and carbonate sediments have higher absolute REE contents than terrigenous ones. Pelitic fraction is the main REE concentrator in the bottom sediments.  相似文献   

14.
Rare earth elements in the sedimentary cycle: A summary   总被引：2，自引：0，他引：2  
The relative and absolute concentrations of rare earth elements (REE) in authigenic and biogenic phases of deep-sea sediments are quite different. Competition between these phases for REE has resulted in fractionation from the parent material, the latter consisting predominantly of terrigenous material, but with a contribution from marine volcanism. The strongest feature of this fractionation is a depletion of Ce, relative to La, in CaCO3, opalline silica, phillipsite, phosphorite, barite, and montmorillonitic clays; and a Ce enrichment in Fe/Mn nodules. The distribution of REE in different masses of seawater strongly reflects their fractionation in sediments. Whereas the relative concentration of REE in rivers resembles that of shale, their removal from seawater by authigenic and biogenic phases results in: (1) a decrease of their total concentration; (2) a depletion of Ce; and (3) an enrichment of heavy REE relative to light REE. The order of fractionation for water masses in the Atlantic Ocean is:Antarctic intermediate water > North Atlantic deep water > Antarctic bottom water> shelf water > river water ～ shale.The shale-normalized pattern for the sum of REE in the authigenic and biogenic phases of pelagic sediment and in seawater resembles that of an admixture of shale and basalt corresponding presumably to the realtive inputs from continents and marine volcanism respectively. The estimated rate of accumulation of each REE in the sediment, however, is approximately 12 times the estimated rate of input of REE from these two sources.  相似文献   

15.
The South Caspian sedimentary basin is a unique area with thick Mesozoic-Cenozoic sediments (up to 30–32 km) characterized by an extremely high fluid generation potential. The large amount of active mud volcanoes and the volumes of their gas emissions prove the vast scale of fluid generation. Onshore and offshore mud volcanoes annually erupt more than 109 cubic meters of gases consisting of CH4 (79–98%), and a small admixture of C2H6, C3H8, C4H10, C5H12, CO2, N, H2S, Ar, He. Mud volcanism is closely connected to the processes occurring in the South Caspian depression, its seismicity, fluctuations of the Caspian Sea level, solar activity and hydrocarbon generation.The large accumulations of gas hydrates are confined to the bottom sediments of the Caspian Sea, mud volcanoes crater fields (interval 0–0.4 m, sea depth 480 m) and to the volcanoes body at the depth of 480–800 from the sea bottom. Resources of HC gases in hydrates saturated sediments up to a depth of 100 m and are estimated at 0.2×1015–8×1015 m3. The amount of HC gases concentrated in them is 1011–1012 m3.The Caspian Sea, being an inland closed basin is very sensitive to climatic and tectonic events expressed in sea level fluctuations. During regressive stages as a result of sea level fall and the reducing of hydrostatic pressure the decomposition of gas hydrates and the releasing of a great volume of HC gases consisting mainly of methane are observed.From the data of deep drilling, seismoacoustics, and deep seismic mud volcanic activity in the South Caspian Basin started in the Lower Miocene. Activity reached its highest intensity at the boundary between the Miocene and Pliocene and was associated with dramatic Caspian Sea level fall in the Lower Pliocene of up to 600 m, which led to the isolation of the PaleoCaspian from the Eastern ParaTethys. Catastrophic reduction of PaleoCaspian size combined with the increasing scale of mud volcanic activity caused the oversaturation and intoxication of water by methane and led to the mass extinction of mollusks, fishes and other groups of sea inhabitants. In the Upper Pliocene and Quaternary mud volcanism occurred under the conditions of a semi-closed sea periodically connected with the Pontian and Mediterranean Basins. Those stages of Caspian Sea history are characterized by the revival of the Caspian organic world.Monitoring of mud volcanoes onshore of the South Caspian demonstrated that any eruption is predicted by seismic activation in the region (South-Eastern Caucasus) and intensive fluid dynamics on the volcanoes.  相似文献   

16.
Controversial genetical interpretations on the fluorite occurrences in the leadzinc deposits of the Nördliche Kalkalpen led to the present study. The distribution of the rare-earth elements (REE) in the fluorspar-carbonate assemblages and the fluorspar separates have been determined non-destructively by means of instrumental neutron activation analysis using high resolution γ-spectrometry. A geochemical model describing the distribution of the REE in the two mineral phases of CaCO3 and CaF2 formed syngenetically under marine conditions has been built up in order to elucidate the observed REE abundances in the carbonates and their fluorspar separates. The low and comparable concentrations of REE, the similarity in their relative distribution patterns in carbonate-fluorspar assemblages as compared to those in carbonate sediments observed by other authors and the sedimentary characterization via the Tb/Ca-Tb/La relation criterion revealed by the present study unequivocally suggest a synsedimentary nature of the fluorspar. In addition, the study showed that a diagenetic recrystallization results in a further fractionation of Tb and La with a preferential improverishment in La. Such a phenomenon opens a possible geochemical criterion for the identification of different generations of fluorspars.  相似文献   

17.
The supracrustal rocks of the Wuyang metamorphic terrain are divided into the Zhao anzhuang,Tieshanmiao and Yangshuwan Formations.These three Formations were dated at 3000-2550Ma,2550-2300Ma and 2300-2200Ma,respectively.∑REE and La/Yb)n of the Zhao anzhuang Formation volcanic rocks are obviously higher than those of the Tiesanmiao Formation equivalents,suggesting a sedimentary gap(2550 Ma boundary)between these two formations,The Zhao‘anzhuang Formation is older than the Tieshanmiao Formation.The sediments of these two Formations show no obvious differences in REE and are generally characterized by low ∑REE and positive Eu anomalies.On the contrary,the sediments of the Yangshuwan Formation are characterized by high ∑REE and negative Eu anomalies.Detailed discussions demonstrate that the Yangshuwan Formation was deposited in an oxidizing environment whereas the other two formations were formed in a reducing environment.At the end of the evolution of the Tieshanmiao Formation about 2300 Ma ago,the sedimentary environment was transformed from reducing to oxidizing .On the basis of the SHAB (soft/hard acid and base)theory,an oxidation-reduction model for sedimentary REE evolution has been established .It is proposed that the mantle tends to become gradually depleted in REE.especially in LREE,and the indices ∑REE and La/Yb) n of mantle-dervived volcanic rocks also tend to become lower and lower.  相似文献   

18.
元素地球化学是沉积物源判别和环境研究的重要手段,但河口海岸地区沉积动力环境复杂多变,人类活动影响强烈,全岩沉积地球化学的示踪研究存在局限性和多解性。选择长江下游干流悬浮物、东海陆架表层沉积物以及长江口具有一百多年沉积记录的ZK6孔,通过化学相态分析（1 N HCl处理）,探究酸溶态微量元素组成特征及其对河口环境变迁的指示。相较于钻孔全岩样品,酸溶态Sr/Ba比能更可靠地反映河口古盐度和海陆相沉积环境的变化。ZK6孔沉积物酸溶态稀土元素（REE）主要赋存于Mn氧化物中,Mn、ΣREE含量、Ce/Ce*以及Sr/Ba比在1899—2007年间呈三段式变化,主要反映长江河口流路分汊和主泓位置改变引起的河口沉积环境变化,进而影响河口环境中活跃元素和次生组分在沉积地层中的保存记录。该研究对今后深化认识复杂河口环境下微量元素地球化学行为以及微量元素示踪海洋环境变化具有借鉴意义。  相似文献   

19.
川西昌台地区上三叠统勉戈组中酸性火山岩之上主要为一套灰黑色至黑色沉积岩石组合,包括板岩、页岩和泥岩等。这套岩石组合可分为两类:底部为存在热水活动参与形成的沉积岩,厚度较薄;底部之上为无热水活动参与形成的沉积岩,厚度较大。本文取样上述两类岩石测得的稀土元素特征基本相似,无明显区别:两类样品稀土含量普遍偏高,与球粒陨石标准化的的配分曲线呈右倾型,LREE富集,基本无Ce正/负异常,具有明显的Eu负异常。有热水活动参与的沉积岩样品与太平洋SER地区现代海底典型热水沉积物的稀土元素特征明显不一致;与该区域内呷村矿区的典型热水沉积岩重晶石和硅质岩的稀土元素特征也不一致。但与秦岭志留系部分热水沉积岩样品和湘黔寒武系牛蹄塘组底部碳质伊利石页岩样品的稀土特征一致,呈现正常碎屑岩的稀土元素特征。综合分析认为,川西勉戈组碎屑页岩出现Eu负异常特征的主要原因是所测样品中的热液组分含量较少甚至无。  相似文献   

20.
稀土元素指标δCe－ΣREE对沉积相的指示研究   总被引：1，自引：1，他引：0       下载免费PDF全文
通过对内蒙古额济纳盆地小狐山剖面沉积物中酸溶组分稀土元素含量及其相关指标、分布模式的分析,讨论了剖面中稀土元素指标δCe－ΣREE与沉积相、沉积环境之间的关系。分析结果表明剖面沉积物酸溶组分中稀土元素丰度均值为7.24μg/g(不包括Y),其中LREE含量占稀土总量的88.67%; 且各层的稀土分布模式均为轻稀土适度富集缓右倾斜型、Eu呈负异常模式,但各相位地层的LREE富集程度与分配模式存在差异。由于小狐山剖面中沉积地层的自身岩性、沉积粒径、矿物结构组成以及气候环境变化等因素均可能会引起REE分异。因此,通过δCe－ΣREE图并结合三次回归曲线,可以很好地将不同沉积相得物质有效的区分开来。小狐山剖面除极少数的几个样品(水下沉积砂)之外,其余的均落在三次多项式回归曲线上部; 而风成砂层则几乎全部落在回归曲线之下; 此外,对于风沙－河流作用下的混合样品也有较好识别,河流过渡相的样品则分布在曲线上或与之相邻近。此研究结果得到了柴达木贝壳堤沉积物的REE数据的验证,运用此方法可以为直观的判别剖面中的不同沉积相,并为定量化划分地层提供依据。  相似文献   

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