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1.
Sediments of the western part of the Valjevo-Mionica basin(Serbia)were examined both geochemically and mineralogically to explain,on the basis of their sedimentologicai characteristics,the causes of changes in their qualitative and quantitative composition.A total of 62 samples obtained from the drilihole at depths up to 400 m was investigated.Using correlation of the obtained data,six geochemical zones were defined,two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics.The first one,upper zone A,consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite.These minerals and very high contents of Na_2O indicate sedimentation in alkaline conditions with increased salinity in arid climate.That provided pronounced water stratification,as well as higher bioproductivity in the basin and sedimentary organic matter preservation.Therefore,the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons.Another specific zone,zone F,contains sediments with very high MgO,K_2O and Li concentrations.Their geochemical correlation,as well as almost complete absence of illite in this zone,indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite).  相似文献   

2.
The geochemistry data show that the total organic carbon （TOC） contents are high in the surface sediments in the eastern part of the Moknine＇ s Sebkha. Low decreasing of organic matter （ OM ） with increasing depth indicates the good preservation of OM in modern sediments. ＂Lignite levels＂ inserted in the sand sequence and deposited at the edge and in the intermediate zone are considered as lithologic and organic markers. It is characterized by high TOC and poor hydrogen index （HI） , indicating a higher plant origin and good preservation of OM in thin beds under anoxic condition. In all samples low values of HI are typical for strong terrigenous input in the Sebkha. Gas chromatography （GC） of saturate fraction showed that OM in the border zone is provided from plants but in the central zone OM is a mixture of terrestrial fraction and little fraction from microalgae. The study of free lipids indicated that this environment was influenced by intense bacterial and microbial activities, as evidenced by the abundance of n-alkanes and nC18-nC22.  相似文献   

3.
The Cenomanian-Turonian oceanic anoxic event(C/T OAE) is developed in southern Tibet.Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri aress shows that the mid-Cretaceous black shales in southern Tibet are enriched in organic carbon.Te molecular analyses of organic matter indicate marine organic matter was derived from algae and bacteria.In the Gamba area,the organic matter is characterized by abundant tricyclic terpanes and pregane,which are predominant in 191 and 217 mass chromatograms,respectively,Pristane/phytane(Pr/Ph)ratios in the C/T OAE sediments are less than 1, demonstrating the domination of phytane.The presence of carotane can be regarded as a special biomarker indicating oxygen depletion in the C/T OAE sediments in the Tethyan Himalayas.In anoxic sediments,β-carotane and γ－carotane are very abundant.The β-and γ-carotane ratios relative to nC17 in the Cenomanian-Turonian anoxic sediments vary from 32.28-42.87and 5.10-11.01.  相似文献   

4.
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   

5.
This paper,based on the fundamental inorganic chemical and organic geochemical characteristics of oilfield waters from the Turpan Depression,presents the contents of organic matter,the distribution of low-carbon fatty acids and the contents of aromatic hydrocarbons as well as their principal ultraviolet absorption spectral and fluorescence spectral characteristics in oilfield waters from different oil/gas-bearing areas.The oil/gas reservoirs in this depression are classified in terms of their conserving conditions.In additon,the paper also discusses the chemical characteristics of oilfield waters from different types of oil/gas reservoirs with an emphasis on the characteristics of their localization in the γNa/γCa-γN a/γCl correction diagram.On this basis it is attempted to expound the fundamental geochemical characteristics of oilfield waters from the Turpan Depression and their geological significance.  相似文献   

6.
Through the analysis of ocean organisms, the distribution characteristics and enrichment of organic matters in modern marine sediments and ancient marine strata, this paper shows that the main factors influencing the formation of excellent marine source rocks are the paleoclimate, biologic productivity, terrestrial organic matter, oxidation–reduction environment, sedimentation rate, and the type of the basin. In addition to those factors,high biologic productivity or high content of terrestrial organic matter input is a requirement for the enrichment of the organic matter in a marine environment. Reducing environment was favorable for organic matter accumulation and preservation in depositing and early diagenesis stage, which is an important element for the formation of high-quality marine source rocks. Paleoclimate also influences the marine source rocks formation, as humid subtropical and tropical climates are the most favorable regimes for the formation of marine source rocks. Wind transports some vascular plant materials into the marine environment. Furthermore, upwellings driven by steady wind can cause high biologic productivity, thus formingorganic-C-rich mud. Suitable sedimentation rate is beneficial for marine organic matter accumulation. Moreover, the type of the basin also plays an important role in the development of marine source rocks. Silled basins with a positive water balance often act as nutrient traps, thus enhancing both productivity and organic matter preservations, while in open oceans, organic matter enrichment in sediments has just been found in the oxygen minimum layers.  相似文献   

7.
The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.  相似文献   

8.
Samples of Continetal shelf sediments from the East China Sea have been studied in an attempt to eluciate the relationship of metallie element enrichment with organoclay complexes. Investigations of the distribution patterns and modes of existence of such elements as Cu, Pb, Zn, Ni, Fe, Mn, etc. in the sediments demonstrate that there exist remarkable positive eorrelations between tha distribution of all elements except for Mn,and the content of clay minerals and organic matter and its type. Experimental results show that the removal of combined organic matter will lead to a rapid decrease in the content of these elements (up to mote than 50%). Organoelay chemistry study indicates that the enrichment of metallic elements in the sediments may involve the following processes: (1) the formation of organic metallic complexes by the ineraction between organic matter and metallic ions in the water body; (2) the production of organoclay complexes by the interaction between the organic metallic complexes and clay minerals in the same medium, (3) the deposition of the organoelay complexes due to the variation of water medium conditions during their migration, thus enabling the sediments to be enriched in some metallic elements. From the above, it can be seen that organoclay complexes may be one of the important forms of existense of metallic elements concentrated in the sediments, and also of significance in eluciating the mechanism of fineralization of metallic elements.  相似文献   

9.
The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic- poor sediments. The geochemical characteristics of the Honggang member have been documented to determine the organic matter types and depositional environments in this paper. The organic matter of the black shales mainly consists of a mixture of land plant-derived and phytoplankton-derived organic matter. Total organic carbon content (TOC)–sulfur–iron (Fe) relationships suggest that the organic- rich black shales were deposited under dysoxic-to-euxinic water conditions. The time that iron minerals remained in contact with H2S in anoxic waters possibly influenced the formation of syngenetic pyrite, and organic carbon controlled the formation of diagenetic pyrite. Organic-poor intervals usually show pyrite sulfur enrichment and higher degree of pyritization values relative to low organic carbon contents. This resulted from HS– diffusing downward from overlying organic-rich sediments and formed Fe sulfides through reactions with sufficient Fe. Trace elements generally exhibit low concentrations and little TOC dependence, suggesting some degree of depletion in these elements in the early Paleogene sediments of the Sanshui Basin. This probably resulted from cyclic recurrences of oxic benthic conditions, which promoted the remobilization of trace elements and caused the low concentration of trace elements.  相似文献   

10.
Gld deposits occurring in metamorphosed microcelastic rocks are distributed extensively at home and abroad.Some deposits of this type are of superlarge tonnage.The formation of gold deposits in metamorphosed microclastic rocks involves three stages:the sedimentary stage,the regionally metamorphic stage,and the ore-forming stage.At the first stage,microclastic sedimentary source rocks were developed in a relatively semi-enclosed reducing sea basin and were enriched in carbon,sulfur and gold.At the second stage,the gold adsorbed on organic matter and clay minerals was relesed and poorly concentrated during the destruction of organic matter and the depletion of clay minerals by regional metamorphism with increase temperature and pressure.At the third stage,a tectono-hydrothermal event took place.As a result,gold was leached from metamorphosed microclastic rocks,transported to ore depositional locus and/or mixed with gold of other sources in the course of migration,and finally precipitared as ores.Gold deposits of this type were eventually formed at the third stage,and they also can be classified as the orogenic belt type and the activation zone type.The gold deposits occurring in metamorphosed microcalastic rocks are the products of reworking processes and the influence of magmatism should be taken into consideration in some cases.  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.
Generally, sandstone-type uranium deposits can be divided into three zones according to their redox conditions: oxidized zone, ore zone and reduced zone. The Dongsheng uranium deposit belongs to this type. In order to study its geochemical characteristics, 11 samples were taken from the three zones of the Dongsheng uranium deposit. Five samples of them were collected from the oxidized zone, four samples from the ore zone and two samples from the reduced zone. These samples were analyzed using organic and inorganic geochemical methods. The results of GC traces and ICP-MASS indicate that the three zones show different organic and inorganic geochemical characteristics.  相似文献   

13.
四川盆地天然气地球化学特征   总被引：8，自引：3，他引：8  
黄籍中 《地球化学》1984,(4):307-321
The Sichuan Basin is one of the largest gas-oil-bearing basins in China. Oil and gas reservoirs occur in Mesozoic, Paleozoic and Proterozoic strata in this basin, with natural gases being dominant. A good wealth of data from 2,000 drill wells on the distribution of natural gases(hydrocarbons: CH4, C2H6^ ; non-hydrocarbons: H2S, CO2, N2; rare gases: He, At,Hg) show that natural gases in the basin are predominated by oil-thermoeraeked and coal-series gases.Geological-factor analysis of the geochemical characteristics of natural gases pro-vide evidence suggesting that the oceurrence of natural gases, especially dry gas, is attributed to the high maturity of organic matter, and the multi-productive formation has a great bearing on the multi-source rocks; the anomalies of some. components(e.g. H2S) are related not only to the type of primary organis matter, but also to the lithological characters of reservoir beds. Also discussed in this paper are some geochemical characteristics of coal-series and non-coal-series gases at the same degree of maturation, demonstrating that the former is characterized by high proportions of CH4, and Hg vapor, high C2/C2, ratio, high δ^13C8,low C2^ , and high iC4/nC4.  相似文献   

14.
The Songliao Basin is one of the most important petroliferous basins in northern China. With a recent gradual decline in conventional oil production in the basin, the exploration and development of unconventional resources are becoming increasingly urgent. The Qingshankou Formation consists of typical Upper Cretaceous continental strata, and represents a promising and practical replacement resource for shale oil in the Songliao Basin. Previous studies have shown that low-mature to mature Qingshankou shale mainly preserves type Ⅰ and type Ⅱ1 organic matter, with relatively high total organic carbon(TOC) content. It is estimated that there is a great potential to explore for shale oil resources in the Qingshankou Formation in this basin. However, not enough systematic research has been conducted on pore characteristics and their main controlling factors in this lacustrine shale reservoir. In this study, 19 Qingshankou shales from two wells drilled in the study area were tested and analyzed for mineral composition, pore distribution and feature evolution using Xray diffraction(XRD), scanning electron microscopy(SEM), low-pressure nitrogen gas adsorption(N2-GA), and thermal simulation experiments. The XRD results show that clay, quartz, and feldspar are the dominant mineral constituents of Qingshankou shale. The clay minerals are mostly illite/smectite mixed layers with a mean content of 83.5%, followed by illite, chlorite, and kaolinite. There are abundant deposits of clay-rich shale in the Qingshankou Formation in the study area, within which many mineral and organic matter pores were observed using SEM. Mineral pores contribute the most to shale porosity;specifically, clay mineral pores and carbonate pores comprise most of the mineral pores in the shale. Among the three types of organic matter pores, type B is more dominant the other two. Pores with diameters greater than 10 nm supply the main pore volume;most are half-open slits and wedge-shaped pores. The total pore volume had no obvious linear relationship with TOC content, but had some degree of positive correlation with the content of quartz + feldspar and clay minerals respectively. However, it was negatively correlated with carbonate mineral content. The specific surface area of the pores is negatively related to TOC content, average pore diameter, and carbonate mineral content. Moreover, it had a somewhat positive correlation with clay mineral content and no clear linear relationship with the content of quartz + feldspar. With increases in maturity, there was also an increase in the number of carbonate mineral dissolution pores and organic matter pores, average pore diameter, and pore volume, whereas there was a decrease in specific surface area of the pores. Generally, the Qingshankou shale is at a low-mature to mature stage with a TOC content of more than 1.0%, and could be as thick as 250 m in the study area. Pores with diameters of more than 10 nm are well-developed in the shale. This research illustrates that there are favorable conditions for shale oil occurrence and enrichment in the Qingshankou shale in the study area.  相似文献   

15.
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16.
The Jiujiang-Ruichang area in northwestern Jiangxi extends along the western part of the minerogenic belt of the middle-lower Yangtze Valley in a terrain of sediments ranging from Ordovician to Triassic in age with NEE-folda,and NW-compressive,NNW-tensile and NEE-compressive-shearing faults as the major structures .Igneous rocks are mostly intermediate-acid epizonal intrusive bodies.Typical copper mineralizations in this area include the skarn-type and stratiform Cu-bearing pyrite-type deposits at Wushan and the porphyry and breccia-pipe type copper-molybdenum deposits at Chengmenshan.Silurian strata,with a great thickness and an average copper content of 51 ppm,are considered to be the source bed of copper mineralization,as is evidenced,among other things,by the presence of an envelope which is notably impoverished in Cu aroud most of the deposits.Magmatic rocks which intruded into the Silurian strata often have relatively high alkali contents and K2O/Na2O ratios ,with extensive potash alteration.Magmatic rocks in the area are of co-melting type or mixed type.The magma assimilated a large quanity of country rocks while ascending.They are characterized by high REE contents,absence of Eu anomalies and high LREE/HREE ratios.Ancient lead and strontium isotopes were detected in feldspar megaphenocrysts from the granodiorite porphyry.Hydrothermal convective circulation systems of magmatic water of magmatic water and supergenic water was extensively developed in the magmatic and country rocks,in which copper,potassium and other ore-forming components were extracted from the country rocks and concentrated through heating,boiling and evaporating.When the ore-forming fluids found their way into the skarn zone or the unconformity between the Wutong Formation and the Huanglong Formation,ore precipitation would have occurred as a result of changing media,If the concentration of KCl exceeded 9%,copper and other ore-forming components might have been deposited in magmatic rocks,forming the porphyry-type ore deposits.  相似文献   

17.
The present research on karst rocky desertification is mainly focused on qualitative analysis and obviously lack of quantitative and successive mechanism studies. Currently, classification of rocky desertification grades mainly depends on ratio of rocky coverage or ratio of plant and soil coverage. The process of rocky desertification was divided into latent, slight, medium and serious grades without mention of soil degradation. The Cha＇eryan catchment in the Huajiang Gorge of Guizhou Province was selected as the research area in this paper. Soil basic physical characteristics, nutrient element contents of soil and plant were studied in the process of rocky desertification. The karst soil characteristics elucidated that the clay content was high, the contents of soil organic matter, nutrient element （except potassium and sodium）, available contents of elements （except of potassium） were also high; ashes of plants were rich in calcium and nitrogen, and poor in iron, zinc, potassium and phosphorus. Meanwhile, the contents of plant ashes showed a significant positive relationship with calcium content of plant. There were no clear relations between soil degradation and succession of rocky desertification according to current classification standard. Soil particle size distribution, specific gravity, soil organic matter content, total and available nutrient element contents did not vary with the succession of rocky desertification.  相似文献   

18.
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   

19.
The volcano-sedimentary succession around Wadi Zaghra in Sinai, at the northernmost segment of the Arabian Nubian Shield, comprises volcanic rocks interbedded with rather immature sediments. The succession is dominated by intermediate to silicic volcanics of medium-to high-K calc-alkaline affinity. It is divided into two units, the lower unit includes intermediate rocks and dacites interbedded with graywackes, semi-pelites and pelites and topped by polymict conglomerates. This unit is subjected to folding and regional metamorphism(up to garnet zone) and is intruded by quartz diorite-granodiorite inducing, locally, low-pressure contact thermal metamorphism. The unmetamorphosed upper unit encompasses acid volcanics intercalated with litharenite, sublitharenite and minor arenite. The rhyolites of this unit pertain to the highly fractionated granites and are characterized by an agpaitic index(NK/A) ranging from 0.87 to 0.96. They may reflect either extensive interaction of subduction-related magmas with the continental crust or a change in the tectonic regime. The present lithological and geochemical characteristics of the studied sediments together with available zircon ages indicate rather distal provenance of their detritus. This detritus comprises fluvial-alluvial sediments accumulated in the intermontane basins, which are half-grabens or tilted fault blocks. The tectonic setting of the depositional basins is active continental margin and continental island arcs. Geochemical patterns of the Zaghra volcano-sedimentary succession indicate their correlation with the Dokhan Volcanics-Hammamat Clastics sequence of the Eastern Desert of Egypt. Also, the Zaghra volcanics display geochemical similarities with those exposed in Sinai, at the Rutig, Ferani and Iqna Shar'a areas. The Zaghra succession is dated as Ediacaran but is not related either to the ensimatic island arc assemblage or to the rift-related assemblage formed during the early stages of the break-up of Rodinia as previously thought.  相似文献   

20.
Lead （Pb） is normally considered as a trace element in soils and sediments for geochemical study. However, the concentration of Pb in firing range soils is generally so high that it should be considered as a major element during the evaluation of the soil geochemical properties. Soil organic matter （SOM） has been reported as one of the major factors to expedite the corrosion of metallic lead （Pb） in acidic and organic-rich soils. The main impacts of SOM on the fate and transport of Pb in firing range soils lie in the following two aspects; （1） the complexation of organic matter with Pb, which has received lots of attention, and; （2） changes in soil redox potential due to the transformation of SOM and its subsequent impact on Pb speciation, which has rarely been investigated. Soils from 6 different firing ranges are selected for this study. These samples have been stored under a closed condition for more than 3 years. The soil moisture contents were well-retained, as all the samples were kept in closed plastic buckets. The analytical data showed that the summation of the soil total organic carbon content （TOC） and inorganic carbon contents （TIC） were consistent with soil total carbon contents （TC） measured in previous years, although the TOC and TIC contents have changed respectively after years of storage. In general, it is observed that the soil TOC decreased against an increase of TIC. The mass balance on such a transformation suggested a major conversion of organic carbon （Corg） to inorganic carbon （CO3^2-） in the stored soils.  相似文献   

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