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1.
As a useful approach for hydrocarbon exploration,the sequence stratigraphy has been commonly accepted.The concepts of sequence and parasequence provide a state-of -the-artframe-work for studying the distribution and characters of depositional system,and analyzing the occurrence,distribution,characteristics of source,reservoir and seal-play elements.The newly-developed geochemical -sequence stratigraphy focuses mainly on the occurrence,distribution and characters of source rocks and reservoir hydrocarbons within a chronostratigraphic framework,Integrated with sequence wtratigraphy,geochemistry can be used to study the surce rock potential within a sequence wtratigraphic framework and to describe the characteristics of hydrocarbons accumulated in reservoirs,which were predicted by way of sequence stratigraphy.The concept of geochemical-sequence wtratigraphy was proposed by Peters et al.(2000).Constructing a reliable sequence stratigraphic framework is the basis of geochemical-sequence wtratigraphic study although it is not the main goal.High-resolution biomarker analysis is critrical to the construction of a geochemical-sequence stratigraphic model.The geochemical-stratigraphic study involves mainly:(1) the distribution and geochemical characteristics of source rocks with relative sea (lake)-level change;(3) to prodict if these reservoirs bear hydrocarbons and their geochemical features;(4) to be used to construct the time-stratigraphic framework.This paper also summarizes the lake basin types,and introduces their facies associatons,source potential and organic geochemical features.At the end,the authors offer some suggestions about how to carry out geochemical-sequence stratigraphic study in ladcustrine strata.  相似文献   

2.
The theory of dissipative structures is applied in this paper to probing into the dynamics, temporal struc-tures and spatial structures of ore-forming processes and the inherent relationships among them. Areas of oreformation are large dynamic systems in development and evolution. The core of ore formation is the "onset ofore-forming processes". and the crux of it is the "transition from mineralization to ore formation". The theoryof bifurcation and theory of fluctuation make possible the access to the solution of this problem. The multiord-er or successive bifurcation of dissipative structures introduces dynamic geochemical processes into geosciencesand inverses the dynamic evolution and temporal rhythms of ore-forming processes. The localization ofdissipative structures introduces dynamic geochemical fields into geosciences and brings to light the causes andmechanisms of the formation and development of geochemical areas of ore formation (regions and zones of oreformation) and their spatial dynamic patterns.  相似文献   

3.
This paper describes the aim and principle of element geochemical division,the source of samples and data processing,the choice of divisional indices and the division of index value ranges.According to the geological structures and characteristic values(the accumulated value of enrichment coefficient)of the mantle-type elements(KT)this region can be divided into seven geochemical zones,i.e.,the Yangtze basement,the Yangtze cover,the Jinshajiang paleo-Tethys,the Lancangjiang paleo-Tethys,the Lanping Mesozoic basin,the Indosinian granite,and the Himalayan granite.Again in accordance with the different characteristic values of high field strength elements(HFSE)(KNb) or radiogenic elements(KTh)16 geochemical sub-zones can be divided.Meanwhile,this paper discusses the rules of variation in characteristic value of the various sub-zones and points out the characteristics of enrichment of oreforming elements in some of the sub-zones.  相似文献   

4.
Previous studies have shown that the ascending, oxidizing brines play a very important role in Kupferschiefer mineralization. Fractures could be the pathway of the brines. In order to clarify the influences of the brines on bulk organic matter, aromatic hydrocarbons and Kupferschiefer mineralization, one veinlet Kupferschiefer profile from the Lubin mine, southwestern Poland was studied with the microscopic, geochemical and Rock-Eval methods. The microscopic results indicate that organic matter of the veinlet sample consists dominantly of bitumen. Its extract content is higher than in other samples. The dominant aromatic compounds are naphthalene and alkylated naphthalenes (Na-PAH), which have migrated into the veinlet sample from other sediments. The content of phenanthrene and its methylated derivatives (Ph-PAH) is much lower than in other samples. The reason may be due to their heavier mass than Na-PAH. It is more difficult for Ph-PAH to migrate. The Na-PAH was probably removed from the shale by dist  相似文献   

5.
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   

6.
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.  相似文献   

7.
Guizhou is one of the dominating karst regions,where laterite is widespread,in China.Seventy-two laterite samples were taken from twelve laterite sections in the karst areas of Guizhou Province,which are possessed of typical subtropical karst geomphological and ecological environmental features and have evolved completely from dolostones and limestones.In terms of the major,trace and REE deta for thd samples this paper discusses the geochemical characteristics of laterite in the karst areas with an attempt to disclose the geochemical process and evolutionary rule of laterite formation.There have been involved three important pedogenetic geochemical precesses in the formation of laterite in the karst areas:(1)enrichment of silicon and aluminum and depletion of calcium and magnesium;(2)enrichment of iron and manganese;and(3) enrichment of aluminum and depletion of silicon.During the formation and evolution of laterite,obvious enrichment and differentiation of trace elements such as Cu,Pb,Zn,Ni,Co,Cr,Pb,F,Cl,and As can be observed,but for the rare-earth elements,their enrichment is remarkable against a weak differentiation.The REE distribution patterns in the laterite are similar to those of its parental carbonate rocks.  相似文献   

8.
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   

9.
Based on the geological and geochemical information about migmatites,the following lines of evidence have been proposed for discriminating the anatectic leucosome in the Dabieshan Complex:(1)its width is larger than that derived from the subsolidus genesis,cutting across regional foliation,thus giving rise to complicated folds and wider selvages;(2)it is composed of melanic and accessory minerals in addition to quartz and feldspars;(3)the significant dfference in anorthites of plagioclase between paleosome and leucosome;(4)temperature and pressure(P/T) conditions revealed by the mineral compositions and assemblages are over those for the onset of anatexis;and (5)it is enriched in the major elements(e.g.Al2O3.Fe2O3and TiO2)and immobile and incompatible elements(e.g.LREE,Th,Hf and Zr).Finally,by combining the geological and geochemical features with the statistical data for the spatial distribution of minerals and mass-balance in the migatites,it is concluded that anatexis is the cardinal mechanism of migmatization in the Dabieshan Complex.  相似文献   

10.
The commonesttask in m ineral exploration is to separateanomalies to reflect distinct geochemical processes (and geo-physical objects) such as m ineralization of various types.Thispaper introduces the recently- developed“multifractal- spec-trum”filters(MSF) for separating various types of geochemi-cal and geophysical anomalies from their the background basedon the distributions of their two- dimensional power spectra(Cheng et al.,1999) . The processing of lake- sediment geo-chemical data an…  相似文献   

11.
The chemical compositions of and the contents of CaCO3, free Fe2O3 and REE in the sediments of the Salawusu section have been analyzed to investigate the geochemical features of different sedimentary facies and explore their sedimentary enironmetnts during the Late Pleistocene.The con-tents of CaCO3, free Fe2O3 and ∑REE in lacustrine deposits of the middle part of the section are higher than those in the other parts ,except SiO2 which shows an opposite trend.According to the distribution characteristics of the components mentioned above, the section may be divided into four parts which are equivalent to those divided in terms of lithologic characters and sedimentary facies.More remarkable characteristics were observed with respect to the distribution of CaCO3, free Fe2O3,∑REE and SiO2/Al2O3 and FeO/Fe2O3 ratios, which can be adopted as the geochemical indices for paleoclimate division.From the above, four paleoclimate stages have been distinguished for the deposition process.The first stage ,dated at 0.20-0.15Ma, is characterized by a dry and cold climate,the second stage, ranging from 0.15 to 0.07 Ma ,by a warm and slightly dry climate,the third stage ,about 0.07-0.01Ma ,by a cold and humid climate;and prevailing in the last ten thorsand years is the fourth stage,with the climate changing graduall from warm-humid to warm-dry.  相似文献   

12.
Multifractal Simulation of GeochemicalMap Patterns   总被引：3，自引：0，他引：3  
INTRODUCTIONThe mathematical modeling of geochemical data continuesto present an important challenge to earth scientists. Basically,the available data are 2-dimensional realizations of 3dimensional patterns, which are the results of one or more genetic processes that usually are poorly understood. It may bedifficult to project from the observations into the rock mass. Inthis paper, multifractal modeling is advocated as a methodologyto characterize geochemical patterns. If a geochemical pa…  相似文献   

13.
Regional stream sediment surveys at a 1:200,000 scale reveal positive and negative regional multi-element geochemical anomalies over medium to large copper-polymetallic orefields of different genetic types in China. Regional geochemical anomalies of orefield refer to those geochemical anomalies that are related to metallogenesis of an orefield in a certain area. The anomaly area is typically 10 to 100 km2. The regional multi-element anomalies related to mineralization can be divided into three groups, that is, the ore-element anomaly association, indicator element anomaly association, and metallogenic environmental element anomaly association. Their common spatial distributions over ore deposits or orefields possess unique structures.The model of spatial structure of regional multi-element geochemical anomalies (RAGSS) of an orefield delineates structural feature possessed by orderly spatial distributions of different groups of multi-element anomaly associations related to orefield metallogenesis. It is  相似文献   

14.
Geochemical Mapping—Evolution of Its Aims, Ideas and Technology   总被引：1，自引：1，他引：0  
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.  相似文献   

15.
It has been suggested that eclogites in the Dabie orogenic belt are exhumation prod-ucts, which had subducted into the deep-seated mantle and undergone ultra-high pressure meta-morphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometem. The Late Cretaceous basalts studied in the pres-ent paper, however, have provided some geochemical evidence for crust-mantle interaction in the area. These basalts are distributed in Mesozoic faulted basins in central and southern Dabieorogenic belt. Since little obvious contamination from continental crust and differentiation-crys-tallization were observed, it is suggested, based on a study of trace elements, that the basaltsare alkaline and resultant from batch partial melting of the regional mantle rocks, and share thesame or similar geochemical features with respect to their magma source. In the spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrated in the continental crust, such as Pb, K,Rb and Ba, and slightly depleted in some HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic com-positions further suggest the mantle is the mixture of depleted mantle (DM) and enriched one(EMI EMII). This interaction can .explain the trace element characteristics of basaltic mag-mas, i.e.,the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpre-ted by the blending of the eclogites in DOB (enriched in Pb and depleted in Hf, P and Nd)with the East China depleted mantle (As compared to the primitive mantle, it is neither en-riched in Pb nor depleted in Hf, P and Nb). It is also indicated that the eclogites in the Dahieorogenic belt were surely derived from the exhumation materials, which had delaminated into thedeep-seated mantle. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes) , as revealed by the late mantle-derivedbasalts in the Dabie orogenic belt.  相似文献   

16.
Anomaly separation using geochemical data often involves operations in the frequency domain, such as filtering and reducing noise/signal ratios. Unfortunately, the abrupt edge truncation of an image along edges and holes (with missing data) often causes frequency distribution distortion in the frequency domain. For example, bright strips are commonly seen in frequency distribution when using a Fourier transform. Such edge effect distortion may affect information extraction results; sometimes severely, depending on the edge abruptness of the image. Traditionally, edge effects are reduced by smoothing the image boundary prior to applying a Fourier transform. Zero-padding is one of the most commonly used smoothing methods. This simple method can reduce the edge effect to some degree but still distorts the image in some cases. Moreover, due to the complexity of geoscience images, which can include irregular shapes and holes with missing data, zero-padding does not always give satisfactory results. This paper proposes the use of decay functions to handle edge effects when extracting information from geoscience images. As an application, this method has been used in a newly developed multifractal method (S-A) for separating geochemical anomalies from background patterns. A geochemical dataset chosen from a mineral district in Nova Scotia, Canada was used to validate the method.  相似文献   

17.
弓长岭富磁铁矿床成因的地球化学模型   总被引：4，自引：0，他引：4  
李曙光 《地球化学》1982,(2):113-121
Based upon geological and geochemical data on the genesis of Gongchangling rich magnetite deposit, it is suggested that the deposit is of multigenesis, and a three-stage geochemical model for the genesis of the deposit is proposed : (1) Depositional stage : the deposition of banded low-grade ores (magnetite-quartzite) was accompanied by high-grade magnetite (hematite)-siderite ores which are intercalated with magnetite-quartzites as lenses or stratoid shoots. (2) Metaamorphic stage: In response to metamorphism, siderite was decomposed into magnetite and graphite with decreasing fo2 and increasing PCO2. On the margin of magnetitc-siderite ores or within the thin intercalated layers where fO2, was high relative to PCO2 were formed graphite-free rich magnetite ores. (3) Hydrothermal stage: As a result of later hydrothermal process diffusive metasomatism between the shoots and host rocks anti silica leaching took place, thus giving rise to the rich magnetite ores of metasomatic type, and altered rocks.  相似文献   

18.
The regional lithospheric chemical heterogeneity in-ers that the East Qinling and its adjacent cratonic re-ions,as suggested by some authors,belong to twoeotectonic units,the North China subdomain includinghe North China Craton and its southern continentalhargin(the North Qinling Belt),and the Yangtzeanubdomain comprising the Yangtze Craton and itsorthern continental margin(the South Qinling Belt).In the North Qinling Belt the metamorphosedolcanic rocks and graywackes of the Early Paleozoicanfeng Group south of the Early Proterozoic QinlingGroup show geochemical characteristics resemblinghose of the are volcanies and are graywackes,espectively.The Early Paleozoic granites intruding in hehe Qinling Group also show similar geochemical fea-tures and similar compositional polarities to theare-type granites.The Erlangping Group north ofthe Qinling Group is a volcanic-sedimentary sequenceproduced in an Early Paleozoic back-are basin basedon geochemical evidence.It is therefore believed thatthe North Qinling B  相似文献   

19.
Lagos lagoon is underlain by the Tertiary to recent coastal plain sands of the Dahomey Basin and receives a huge volume of sediments from surface runoffs, canals, rivers and other drainage networks. The dumping of domestic and industrial wastes into these drainage channels open up the possibility of deleterious materials, which carry with them toxic metallic ions, being discharged as wastes into the channels, these eventually find their ways into the lagoon. Sediments being sinks for metals, the identification and quantitative evaluation of metallic ions in the Lagos lagoon sediments is desirable. This study aimed at ascertaining the concentrations of these metallic ions in the sediments. One hundred samples of sediment were systematically obtained along the banks, drainage channels （waste discharge points）, shelves and the center of the lagoon. These samples were dried, disaggregated and sieved for grain size （granulometric） analysis to evaluate the transport and depositional mechanism; X-ray diffraction and heavy mineral separation were used to determine the mineralogy. The 〈75 μm sieved portions of the samples were digested using aqua regia at 96℃ for two hours. The resulting clear solutions were analyzed for major oxides and trace metals using the Inductively Coupled Plasma-Optical Emission Spectrometry （ICP-OES）. X-ray diffraction analysis revealed quartz as the preponderant mineral. The geochemical result revealed that SiO2 ranges from 78.57%-98.88%; TiO2, 0.01%-0.32%; A1203, 0.15%-6.32%; Fe2O3, 0.44%-11.62%; K2O, 0.10%-9.60%; CaO, 0.04%-5.50%; MgO, 0.04%-0.98% and P2O5, 0.01%-0.30%, The major oxide compositions indicate the dominance of sand particles over clay in the sediments.  相似文献   

20.
Developed in the Mt.Kunlun orogenic belt at the northern margin of the Tibetan Plateau is an active Cenozoic volcanic zone which is more than 1000km in length and some ten to hundred kilometers in width.It extends east-westwards and is roughly parallet to the strike of Mt.Kunlun.The Cenozoic volcanic rocks are divided into the northern(N-)and southern(S-)subzones.Eruptions of volcanic lavas in the S-subzone are related to an initial rift zone within the north Qiangtang terrane,but the volcanic rocks in the N-subzone are relatively close to the contact zone between the Mt.Kunlun and the Tarim terrane.The space-time distribution,petrological and geochemical features can be explained by a model of southward intraplate subduction of the Tarim terrane.  相似文献   

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