Showing papers in "Journal of Mineralogy and Petrology in 2006"

Active tectonics of the eastern margin of the tibet plateau

Abstract: The eastern margin of the Tibet Plateau is composed of the Minshan Block and Longmenshan.Studies on tectonic landform show that the average sinister slip rate is 1.4 mm/a with a vertical rate of 0.3 mm/a along the Huya fault since late Quaternary.The average vertical slip rate is between 0.37 mm/a and 0.53 mm/a along the Minjiang fault and the sinister slip is similar to the vertical one.Among the Longmenshan Tectonic Zone,the Wenchuan-Maowen fault,Beichuan-Yingxiu and Penxian-Guanxian faults have the average vertical slip rates of 1 mm/a respectively,and show same amount of right and vertical offsets.Based on the data of focal mechanism and GPS survey,a tectonic deformation model of southeastwards extrusion of the eastern marigin of the Tibet Plateau is proposed.

ORIGIN OF THE LUOBUSA OPHIOLITE,SOUTHERN TIBET:Sr-Nd-Pb ISOTOPIC CONSTRAINTS ON CRUST LAVAS

Abstract: The Luobusa ophiolite is one of well-outcroped and well-studied rock in the eastern segment of Yarlung Zangbo ophiolite belt.The Sr-Nd-Pb isotopic compositions of crust lavas are characterized by higher initial Sr isotopic ratios,lower Nd isotopic ratios,large e_(Nd)(t) and enrichment in radiogenic lead.The reasons for higher initial Sr isotopic ratios are probably that there is enriched mantle endmember and the ophiolite underwent metasomatism of fluid from the melting of terrestrial matter in the course of formation.Nd isotope and Sr-Nd isotope demonstrate that the source of crust lavas in Luobusa ophiolite has not only the characteristics of N-MORB,but also the contribution of EMⅡ enriched mantle endmember.On the Pb-Pb diagram,the analytical spots are all plotted above NHRL,ΔSr=47.4~73.0(58.4 in average),Δ7/4Pb=0.69~12.20(5.87 in average),Δ8/4Pb=12.78~58.39(35.23 in average),indicating that there is Dupal isotopic anomaly.The Sr-Nd,Pb-Pb and Nd-Pb isotopic relationships of the crust basalts suggest a mixing source of magmas with the properties of the depleted mid-ocean ridge basalt mantle endmember(DMM) and EMⅡ enriched mantle endmember in Luobusa ophiolite.

GEOCHEMICAL CHARACTER OF DISPERSED ELEMENT IN SPHALERITE FROM FULE Pb-Zn POLYMETAL DEPOSIT,YUNNAN PROVINCE

Abstract: The dispersed elements have great economic value,and are widely applied to high and new-technology industries.However it is difficult for them to accumulate and form ore deposits because of their low assay and dispersivity in the crust.Four dispersed elements Cd,Se,Ge and Ga have economic value in Fule PbZn deposit which is localed in the southeast part of Sichan-Yunnan-Guihzou polymetallogenic district.The dispersed elements mainly occurred in sphalerites with average content of w(Cd) 16 183×10~(-6),w(Se) 163×10~(-6),w(Ge) 135×10~(-6) and w(Ga) 86×10~(-6) resectively,and with the content of Cd being the highest in China.The colour of sphalerite can be divided into dark-brown,red-brown and yellow-brown.Cd occurs mostly in dark colour sphalerite,Ge and Ga in light colour one,the content of Se does not change in different colour sphalerite.Mainly occurred as allomerism form,Cd,Ge,and Se occur in crystal lattice of sphalerite,where Cd and Ge occupy the position of Zn and Se occupies the position of S.Ga usually are adsorbed in lattice defect as microadsorption form,and the other enter sphalerite crystal lattice in place of Zn in sphalerite Cd-Zn are negative correlation,Ge-Zn are positive correlations,but Se-Zn are independent.The geochemical characters of the dispersed elements indicate that the deposit belongs to sedimentation-reformation type.

The character of upper paleozoic reservoir fractures and the evaluation of their distribution in tabamiao area of ordos basin

Abstract: According to core of well drilling,study in thin section fracture,and analysis of fracture explanation from well logging,combined with history of the regional tectonic stress and the isotope character of filling,from well logging the genesis of fracture is determined.That the fractures are typical regional fractures which have following characters:1)There are extension high-angle or vertical fractures in core,which appear in group;2)Both sandstone and shale,develop fractures,with the former better than the latter;3)The formation period of fracture coincides with active period of Yanshan tectonic movement;4)The attitude of fractures are stable and coincide with the principal stresses of Yanshan tectonic movement;5)The growth of fracture is not constricted by local deformation.Based on the summary of geological factors controlling the development of fractures,finite element technique is employed to simulate the structural stress field and the distribution characteristics of regional fractures is evaluated in line with the stratigraphic feature.

Albitization of the volcanic rocks of the xiong′er group,western henan,and its implications

Abstract: The albitization of the volcanic rocks of the Xiong′er Group,western Henan,was studied based on rock thin section observations and electron-probe microanalysis(EPMA).Alteration textures are found through petrographic studies.EPMA results indicate that the feldspars in the intermediate volcanic rocks of the Xiong′er Group are mainly albite or oligoclase,and dominantly albite,and the feldspars in the felsic rocks are compositonally pure albite(~Ab97).These albite-rich feldspars are the products of widespread albitization processes.The event of albitization possibly took place during the eruption of the Xiong′er Group,which was revealed through the comparison of the volcanic rocks of the Xiong′er Group volcanics with the later intermediate intrusions.It is suggested that the albitization might attribute mainly to deuteric alteration,and minor seawater may make contribution also.The alteration processes have somewhat increased the total alkali(Na_2O+K_2O) content of the volcanic rocks of the Xiong′er Group,which may be initially composed of basaltic andesite-andesite-dacite-rhyolite suite.

Geochemical characteristics and tectonics mechanism of the meta-basic rocks for ophiolite complex in wandashan orogenic belt

Abstract: The original rock of meta-basic rocks in ophiolite complex of Wandashan orogenic belt can be divided into two sorts.The meta-basalt rocks in ophiolite nappe around the Dadingzishan and Xianrentai show following geochemical characteristics:high content of TiO_2,enrichment in HFSE,such as Nb,Ta,Zr,Hf and enrichment in LILE,such as Rb,Sr,Ba and LREE.The geochemical characteristics Indicate that the meta-basalt rocks belong to the OIB.The geochemical characteristics of the samples of the meta-basic rocks in the Yuejinshan metamorphic complex belt near the Yuejinshan block fault Indicate that the meta-basalt rocks belong to the tholeiite series of MORB,with enrichment in Rb,Ba,Th etc.The fact that the elements of Rb,Ba,Th are rich and active in the crust indicates that the rocks were subjected to erosive metamorphism during the collision of two blocks.

Dissolution of calcite cement and its contribution to the secondary pores of reservoir in the kela 2 gas field in the tarim basin

Abstract: Precipitation and dissolution of carbonate cements within clastic rocks are directly related to pore volume and permeability of the rocks,and also have an important impaction on reserves and transportation of oil and gas.On the basis of vertical examination,this study reveals that there is an inverse relation between the porosity,permeability and the carbonate cements in the reservoir from the Kuche depression of the Tarim Basin,that is,the more the carbonate cement content is,the lower the porosity and permeability is.It is the calcite cementation that results in the variation of carbonate mineral contents.The microstructures of the clastic rocks indicate that the variation of calcite with depth is resulted from the early intergrain precipitation of calcite,the dissolution during deep burial and then the later recementation.Moreover,the calcite cement dissolution produced the abnormally high porosity and permeability zone around the depth of 3 800 m in the well K201.There are ground water type zones on the vertical direction with the variation of calcite content.Based on the water-rock interaction thermodynamic phase equilibrium theory and the mass conservation law,the relation between calcite solubility and water types was discussed in this study.It is showed that the calcite solubility depends on the value of -[Ca~(2+)] of the ground water.The lower the water [ΣCO_2]-[Ca~(2+)] is,the higher the calcite solubility is.The Na_2SO_4 type water with [ΣCO_2]-[Ca~(2+)]≈0 is a typical saturated fluid in which calcite content is stable,so neither precipitation nor dissolution happens.The NaHCO_3 type water,-[Ca~(2+)]0,is a typical supersaturated fluid,and a large volume of calcite cement precipitates resulting in the decrease of porosity and permeability of rocks.The CaCl_2 type water,-[Ca~(2+)]0,represents a kind of unsaturated fluid in which no calcite precipitates and the early calcite cement can be dissolved so that a large quantity of secondary pore space can be formed with high porosity and permeability.In the Kela 2 gas field the CaCl_2 type water zone proves to be of the highest quality reservoir.

Pollutant characteristics and pollution control of heavy metal contaminants in sediments of moshui lake,wuhan,china

Abstract: Moshui Lake has been seriously polluted by heavy metalsBased on the analysis of heavy metals(Cu,Cr,Pb,Zn,As and Hg) in the bottom sediments,their horizontal and vertical distribution characteristics are discussedThe change pattern,causes and pollution degree of different heavy metals are synthetically studied by using the index of geoaccumulation(I_(geo))The results showed that the order of pollution intensity of the bottom sediments in the Moshui Lake is Zn Hg CuCr Pb AsCompared to the area near the centre of lake which are less contaminated,the lake sediments near lakeshore are contaminated heavilyThe contents of major heavy metals in the bottom sediments decrease with depth,and the changes are mainly affected by the status of pollution,not by the size of the sediment particles,remobilization or transformation of trace heavy metals during early diagenetic processesIn order to prevent Moshui Lake from heavy metal pollution,more efficient measures such as control of external pollutant sources,dredge of sediments and waters circulation by introduing river water into the lake,especially the restoration of aquatic vegetation should be taken to fundamentally improve the water quality

Composition of organic carbon isotope of early cambrian black shale in the xiang-qian area and its significances

Abstract: This paper mainly demenstrated the composition of organic carbon isotope of Early Cambrian black shales from the ″Xiang-Qian″ area,Yangtze Platform.Detailed study showed that the Dengying Formation dolomites of Late Sinian were deposited in carbonate platform environment,whereas the Niutitang Formation black shales of Early Cambrian in continental shelf facies.In Ganziping area,Hunan Province,the water may be deeper than that in Songlin area,Guizhou,and perhaps it was transited into slope facies.Organic carbon contents(TOC/%)) rang from 0.05% to 12.31% with an average of about 4.97%.The organic carbon isotopic values(δ~(13)C_(org)) fluctuate sharply from-29.49‰ to-34.41‰ PDB with a mean value of-31.78‰ PDB,showing a negative excursion close to 4.3‰.In Niutitang Formation black shales,the changes of δ~(13)C_(org) values and TOC contents are more obvious than those in Dengying Formation dolomites of Late Sinian.They show three remarkable fluctuation in the whole profiles,which indicates that the sea-level changes were in the transgression or regression.In Late Sinian,the δ~(13)C_(org) values of the dolomites are slightly higher than those in Early Cambrian black shales,showing the desecent of sea level.The carbon isotope curves exhibit the changes of sea level,primary productivity and rise oceanic currents,therefore,this study provides some significant information about Early Cambrian palaeocean in south China.

Ree geochemistry of hydrothermal calcite from tinpolymetallic deposit and its indication of source of hydrothermal ore-forming fluid

Abstract: Calcite is the dominant gangue mineral in the Furong tin-polymetallic deposit.The calcites associated with greisen type ore,altered rock type ore and skarn type ore from Bailashui and Goutouling mineral district,are characterized by two types of REE distribution patterns,LREE-enriched pattern and flat REE pattern.LREE-enriched pattern of calcites accompanying greisen type ore and skarn type ore are very similar to those of Qitianling granite.It implied that this REE behavior of calcite inherited from the characteristics of LREE-enriched magmatic hydrothermal fluid derived from the Qitianling granite plution.The calcites associated with altered rock type ore with flat REE distribution patterns indicate LREE of the hydrothermal fluid extracted during the alteration or mineralization process.Therefore,the data of calcites suggest a magmatic source for the or-forming hydrothermal fluid.

Provenance analysis of paleogene gyachala formation in southern tibet:implication for the initiation of collision between india and asia

Abstract: Gyachala Formation is Paleogene marine strata in Gyangze area,which belongs to the northern subzone of the Tethyan Himalaya.The paper studied the lithology of sandstones and the type of disperision pattern of sediment,analyzed the chemical composition of volcanic grains found in the sandstones by electron microprobe analysis.The data show that the provenance of the Gyachala Formation is proximal recycled orogen,with the lithic detritus comprised by andesitic igneous rocks,derived from an erosoin of a volcanic arc.The Tethyan Himalaya tectonically belongs to the India passive continental margin.The sedimentary facies on this margin vary from shallow water shelf in the southern subzone of the Tethyan Himalaya to deep water basin in the northern subzone of the Tethyan Himalaya.In the period from Jurassic to Cretaceous,the terrigenous clastics of the Tethyan Himalaya were mainly comprised by quartzose sandstones of very high maturity,derived from cratonic areras of India continental plate.In contrast,the composition of volcaniclastic sandstone of Gyachala Formation was from Gangdese volcanic arc area,which is located on the Asian continental margin.This interpretation is also supported by the south-direction palaeocurrent data.During the Gyachala Formation deposition time the detrital material eroded from Gandese volcanic arc was transported across the Yarlung Zangbo Suture Zone and deposited on the India continental plate passive margin.Such development requires presence of a foreland basin or remanent basin.Therefore,the Gyuchala Formation provides evidence that at the time of its deposition Tethyan oceanic crust was already completely subducted and India and Asia continental plates collided,resulting in the development of a foreland basin or remanent basin.Therefore the presence of Gyachala Formation provides evidence that the initial collision between India and Asia plate occurred at about 65 Ma.

Strontium isotope composition and control factors of global seawater in triassic

Abstract: Triassic is a period with a great change in global environment,so it is more difficult to study its strontium isotopic composition of seawater.The Strontium isotope curve of Triassic seawater evolves in an elusory form.The()~(87)Sr/()~(86)Sr value of seawater changed rapidly in a short time of early Triassic,but varied little from middle Triassic to early period of late Triassic.The published Strontium isotope curves of global seawater are different.It is difficult to understand why the sharp rise in the()~(87)Sr/()~(86)Sr values at early Triassic(about 10 Ma) was coupled with the global sea-level rise.It is thought that the most important reason should be the absence of a dense protective land plant cover following the mass extinction occurred in the latest Permian,leading to the enhanced erosion of land.The recovery in ecology,especially recovery of land vegetation during the latest early Triassic,coupled with the volcanism and transgression is the reason for the decrease of(()~(87)Sr)/()~(86)Sr value at the boundary of early/middle Triassic.During middle Triassic to early period of late Triassic(approximately 235 Ma to 220 Ma),with the global sea-level constant rising,the stabilization of()~(87)Sr/()~(86)Sr value of seawater are caused by the protection from extensive epicontinental seas to radiogenic Strontium.The closure of Paleo-tethys,the collision of Cimmerian continent with Eurasia,and the global sea-level falling make the()~(87)Sr/()~(86)Sr value ascend again after the middle period of Late Triassic.

Carbon isotopic reversed distribution of the soluble organic components for the cambrian and ordovician carbonate rocks in tabei and tazhong areas,tarim basin

Abstract: Carbon isotopic compositions of the soluble organic components for the sedimentary organic matter have the inherited effect of parent materials,which can be affected by the thermal and the biodegradation factors.In this paper,the carbon isotopic compositions of the soluble organic components for the Cambrian and Ordovician carbonate rocks collected from Tabei and Tazhong Areas in Tarim Basin were analyzed by MAT252 Isotope Mass Spectrometer.The results show that their carbon isotopic compositions have apparently reversed distribution.The saturated hydrocarbons,with δ~(13)C values ranging from-29.7‰ to-26.2‰(average-28.5‰),obviously enriched in()~(13)C.However,the asphaltenes,with δ~(13)C values ranging from-37.8‰ to(-27.1‰)(average-31.9‰),obviously enriched in()~(12)C.The distribution of δ~(13)C values of the soluble organic components is as follows: saturated hydrocarbonsaromaticsnon-hydrocarbonsasphaltenes.This appearance of carbon isotopic reversed distribution,based on the previous studies and the geological setting,is regarded to result from the heating effects and the long-term thermal evolution,and it may be an important geochemical characteristics for the sedimentary organic matter in high evolution stage.

Confirmation and implications of structural water in ultra-high pressure eclogites from dabie mountains

Abstract: The nominally anhydrous minerals(NAMs) such as garnets and omphacites in Ultra-high pressure eclogites in the Shima and Yingshan areas from Dabie Mountains were investigated by Fourier transform infrared spectroscopy(FTIR).It reveals that the NAMs could contain hydrogen occurring as hydroxyl(OH) or molecule H_2O.It was found that the water contents are not uniform in the NAMs from different areas,and from the different grains at the same area to the different position in the same grain.the structural water contents of the omphacites at Shima and Yingshan are varied from 90×10~(-6)～1 670×10~(-6) and from 110×10~(-6)～710×10~(-6) respectively;while the garnets are from 510×10~(-6)～830×10~(-6) and 0~180×10~(-6) respectively.The influence of structural water on the eclogites deformation and the relationship between structural water and fluid inclusions in NAMs are initially discussed in association with the related research result of former academicians.

~(40)Ar/~(39)Ar DATING AND GEOLOGICAL SIGNIFICANCE ON THE Cu-BEARING PORPYRITE OF SHAXI FROM SOUTHERN TAN-LU FAULT BELT

Abstract: The Shaxi porphyrites are composed of diorite-quartz diorite series,forming a medium scale copper deposit near south Tancheng-Lujiang(Tan-Lu) fault belt,central Anhui,east ChinaShaxi porphyry Cu-Au deposit occurs in a complex intrusive body composed of quartz diorite porphyry,biotite-quartz diorite porphyry and fine to mediumgrained porphyry diorite along the lower part of Yangtze metallogenic beltEach biotite and plagioclase samples were analyzed for age determination by the ~(40)Ar/~(39)Ar methodThe sample yield reproducible ages with a high level of confidence of both average plateau and average isochron ages of 13262 Ma±028 Ma and 13259 Ma±046 Ma respectively,which is more precise than K-Ar and Rb-Sr dating ages made previously and better constrains the times of the main event of porphyry formation of Yanshanian period of igneous intrusive in the Shaxi Cu-Au porphyry depositThe average minimum apparent age of 86 Ma may represent the thermal event related to Cu-Au mineralizaton in this regionIt is believed that the age of around 1326 Ma can represent the intrusive time in Shaxi region,and the Cu-Au mineralization should occur later by strong thermal event of magmatism

Geomorphic and sedimentary evidence for reversion of strike-slip direction in longmen shan fault zone

Abstract: Based on the evidence of migration of the depocentre and fan in the foreland basin,the active tectonics,geomorphy and paleomagnetism from Mesozoic to early Cenozoic and later Cenozoic,the direction of strike-slip faulting has been reversed from sinistral strike-slip in Mesozoic and early Cenozoic to dextral strike-slip in the later Cenozoic.According to stratigraphy and paleomagnetism,the reversion of the strike-slipping direction in Longmen Shan fault zone happened during 43 Ma to 3.6 Ma.It was considered that the dextral strike-slip in the later Cenozoic is due to the effect of post-India-Eurasian collision,and the sinistral strike-slip in Mesozoic and early Cenozoic is due to the effect of shorting of Songpan-Ganzi Fold Belt driven by accretion of the Cimmerian continents and the India/Eurasia collision.

Isotope dating of the be′erkuduke tin deposit in the eastern junggar area

Abstract: The Bei′erkuduke tin deposit in the eastern Junggar area occurred in Late Carboniferous granitoids.It is a tin deposit of quartz-vein and greisen types.K-Ar dating of mica from the tin-bearing quartz-vein yields an age of 296.3 Ma±2.6 Ma,representing the metallogenic time and suggesting the metallogenesis coeval with the continental collision.The K-Ar age for mica from greisen is 177.9 Ma±2.6 Ma,obviously late than the metallogenic time,reflecting a post-ore tectono-thermal disturbance event.

Characteristics of pore structure and reservoir evaluation in h2+3 tight gas reservoir,daniudi gas field

Abstract: The application of casting section,scanning electron microscope to the study of microscopic pore structure of H2+3 tight gas reservoir in Daniudi gas field indicates that the digenesis of compaction and cementation is the major controlling factors on the compact reser,while corrosion can improve the reservoir property to some extent.The reservoir mainly develops secondary porosity composed of intergranular dissolved pore,intragranular dissolved pore,intercrystal micro pore and intercrystal seam.Intergranular dissolved pore that can improve the porosity to 8% to 20% is the major pore type.The pore throat assemblage types are medium poresmall throat and small pore-thin throat.By means of factor analysis and cluster analysis,the microscopic pore structure can be classified into three basic types and four sub-types,of which typeⅠand typeⅡ are of good quality,and considered as the further targets for exploration and development of tight gas reservior.

Sequence stratigraphy of paleogene and exploration of blind reservoirs in the jizhong depression of langgu subdepression

Abstract: After exploration of oil and gas for more than twenty years,it is difficult to find out the ancient buried hill and paleogene structure trap.It has important theory and practical significance to explorate blind reservoirs by using the basic principles of sequence stratigraphy.Paleogene of Langgu subdepression is divided into one Megasequence,two supersequences and eleven third-order sequences.Evolution of tectonics and sequence experienced initial faulting period,strongly faulted period,the return of the rise faulted period and disappearing faulted period.Oil and gas assembly connected with sequence developed well in Langgu subdepression.Jiu zhou-Gu′an structure belt is the favorable belt to develop blind reservoirs.The intersection sites of submarine fan or fan delta which pinch out at mudstone and structural monoclinic are the favorable position to form the up-dip-pinch-out-lithologic deposit.Submarine fan sandstone or conglomerate developed in SQ1-SQ3(Es4)is the important directions to explorate Paleogene deep hydrocarbon in the Langgu subdepression,particularly natural gas.

Ar-Ar DATING OF POTASSIC ALKALI-ROCKS IN THE WESTERN KUNLUN-KALAKORUM MOUNTAINS——Example for the rocks of Yanghu,Zankan and Kuzigan

Abstract: Volcanic rocks occurred at Yanghu,Qiankan and kuzigan in the center of the northwestern Tibet and the southwestern Xinjiang,which is the western part of Ailaoshang-Jinshajiang Cenozoic potassic alkali magmatic rock zone.The Ar-Ar dating of the rocks shows the ages of 17 Ma,12 Ma and 18 Ma.Study on the chemical compositions of these rocks indicates that the time of magmatic activity in the Ailaoshang-Jinshajiang Cenozoic potassic alkali magmatic rock zone becomes younger gradually from east to west.The magmatic event starts from the middle of the Eocene to the Pleistocene.This phenomena reveals that there is some inherent relationship of the collision between the India slab and Europe-Asia slab.

Study on carbon and oxygen isotopes in granite-type hydrothermal uranium deposits:a case of the xiazhuang uranium ore field in northern guangdong

Abstract: The Xiazhuang uranium ore field is one of the most important ore fields with complex mineralization conditions.In this study,some carbonate samples in deposits are used to analyse carbon and oxygen isotopic composition.It is indicated that the mineralizer mainly comes from mantle degassing related to the regional deep faults,and part of carbon comes from organic matter in the crust.Strong fluid degassing occurred in uranium mineralization plays an important role in precipitation of pitchblende.

Characteristics of rare earth elements of lacustrine exhalative rock in the xiagou formation,lower cretaceous in qingxi sag,jiuxi basin

Abstract: The lacustrine "white smoke type" exhalative rock occurred in the Xiagou Formation of Lower Cretaceous in Qingxi sag,Jiuxi basin is a sort of infrequent lacustrine "white smoke type" exhalative rock full of Ferroan dolomites and albites.This paper discusses the REE geochemical characteristics of the rock and its connection with hydrothermal depositional environment.It is showed that the exhalative rock has basal character of hydrothermal depositional structure of "LREEHREE",with positive ΣREE and negative δCe,which different from character of marine exhalative rock.Since the REE patterns of rare earth element and exceptional distributal characters of δEu and δCe are highly similar to the characters of alkalescent tholeiite of the same layer,indicating that the exhalative rock of Xiagou Formation is closely related with the basalt of same layer.The fact that the amount of REE of exhalative rock decreases outwards indicates that exhalative rock of Xiagou formation may be connected with sublacustrine hydrothermal convection circulation.

The ftir spectra difference between biogenic and abiogenic aragonites

Abstract: The FTIR spectra of biogenic aragonites in crossed lamellar layers of 16 species of mollusk shells were statistically analyzed and compared with those of abiogenic aragonites which include the geological and synthetic aragonites.It is firstly observed that the internal vibration frequencies of carbonate ions of biogenic aragonite are clearly different from those of abiogenic aragonites.Particularly,the frequency of ν_2 band(out-of-plane bending of carbonate ions) in biogenic aragonites with a mean value of 863.4 cm~(-1) is clearly higher than that of abiogenic aragonites with a mean value of 855.5 cm~(-1).The mean frequency shift of ν_2 band between these two kinds of aragonite is up to 7.9 cm~(-1),so it is suggested that the ν_2 band can be used as a fingerprint band to discriminate the biogenic and the abiogenic aragonites.

Frequency division and the analyse of its application for sandstone ff continental fcies in seismic prospecting

Abstract: Interpretation principle of frequency division is used to identify the syntony energy corresponding to the seismic reflection along certain reservoir and fixed time-window,and determine the spatial distribution shape,sedimentary thickness and relative thickness of the reservoir beds.The a certain strata,which is characterized by river to delta sedimentation with thin alternation layers less than 20 meters,is taken as a target beds for the research.The traditional analysis of seismic property is restricted by effective resolution and detecting limit.So the interpretation of frequency division is,for the first time,used to precisely delineate the boundary of sand bodies and look for the favorable reservoir facies.It is showed that the final result of analysis images is very clear in demonstrating the shape and boundary of the ancient river courses,sheet-shape sand bodies in the front of delta and the thickness of the beds,even those beds with their thickness less than 10 meters.The precision of this technique is high and can reaches 95%.

Trace element characteristics of cenozoic basalts and their mantle xenoliths selected from aershan area in inner mongolia,china

Abstract: There were three times of Cenozoic volcanic eruptions which could be divided into Pliocene,Pleistocene and Holocene in Aershan area of Inner Mongolia.The nearest eruption activity happened in 1900a.B.P,which implies that it may erupt again in the future.In order to probe into the distribution feature of mantle fluid under the active volcanoes,rare elements and trace elements of basalts,xenoliths and melt inclusions were analyzed by INAA and Synchrotron Radiation X-ray Fluorescence(SRXF).Basalt samples from different locations in Aershan area analyzed by instrumental neutron activation analysis(INAA) have the same distribution patterns of REE and trace elements,such as Σ8REE=96.93~114.94,Eu/Sm=0.32~0.37,La_N/Lu_N=8.89~12.52.The similar Primary mantle-normalized patterns of incompatible elements for Cenozoic volcanic rocks with normal abnormity of element Ba,Ta,Sm and without Sr abnormity indicate that magma did not differentiate.The similar REE contents of the same minerals without inclusions from different xenoliths suggest that the mantle source of different active volcanoes have the same REE contents.The REE content differences between same minerals with and without melted inclusions selected from same mantle xenolith sample indicate that the melted inclusions are rich in REE.The same patterns of trace elements of the same inclusions and host minerals from different xenoliths analyzed by SRXF imply that the mantle fluid has no remarkable heterogeneity in Aershan area.

Study on chemical exfoliation of industrial vermiculite from weili mine,xinjiang

Abstract: This work discussed the chemical exfoliation on the industrial vermiculite samples from Weili Mine of XinjiangIndustrial grade hydrogen peroxide solutions are used as chemical exfoliation reagents,The characteristic and primary effect factors of the industrial vermiculite chemical exfoliating are discussed on the basis of the chemical composition and XRD of the industrial vermiculite sampleThe exfoliation results and structure change are described with the expand times and XRDThe results show that the industrial vermiculite can expand as big as 4 times when exfoliating with 25% hydrogen peroxide solutions,and the expanded industrial vermiculites samples are of no obvious structure change and preserve their ductility

Geochemistry and its tectonic significance of kaimeng ophiolites in jiali fault belt,tibet

Abstract: Kaimeng ophiolites locate in Jiali fault belt and expose along Kaimeng ridge with a E-W trend.The ophiolites mainly consist of harzburgite,clinopyroxene peridotite,pyrolite,troctolite and gabbo.Kaimeng ophiolites are low content in Si,K_2O+Na_2O and Ti and high content in Mg and Fe,low ΣREE(ΣREE=0.415×10~(-6)~3.273×10~(-6)) and enrichment of ΣLREE in the harzburgite and troctolites,and depletion of ΣLREE in the clinopyroxene peridotite and gabboes.The ΣREE patterns display almost a flat-model with "W" type, showing obvious Eu positive anomaly.In the curves of the trace element distribution patterns normalized by the primitive mantle,Kaimeng ophiolites exhibit Rb ,Ba,Sr enrichment and Nb,Ta depletion,showing that the ophiolites were formed in the island-arc circumstance.The existence of Jiali suture and Bangongcuo-Nujiang suture at the same time proved that the Meso-Tethyan ocean(T_3-J_2) was an archipelatic ocean.

A STUDY ON METASTABLE EQUILIBRIUM IN THE QUATERNARY RECIPROCAL SYSTEM OF Li~+/Cl~-,CO_3~(2-),B_4O_7~(2-)-H_2O AT 298 K

Abstract: This paper presents the experimental data of metastable phase equilibrium of Li~+/Cl~-,CO_3~(2-),B_4O_7~(2-)-H_2O quaternary system at 298 K for Zhabuye salt lake in Tibet,from which the metastable phase diagram and physicochechemical properties(density,pH value,conductivity and refractive index) vs composition diagram is drawn.This quaternary system is a simple evtonic type,no double saltor solid solution is formed.The isotherm diagram consists of one invariant point,three univariant curves and three crystallization fields corresponding to Li_2B_4O_7·3H_2O,Li_2CO_3 and LiCl·H_2O salt.

The characteristics of the mantle fluid metasomatism of the alkali-rich porphyries and its xenoliths in western yunnan

Abstract: Xenoliths derived from different depth were found in the alkali-rich porphyries in western Yunnan.The petrographic features and petrochemistry data from the porphyries(host rocks) and its xenoliths were studied.The research showed that the host rocks were rich in SiO_2,Al_2O_3,Na_2O and K_2O,the xenoliths were rich in CaO,MgO,Fe_2O_3 and FeO respectively.And amphibolization,saussuritization and silicification were main alteration characters.Cataclastic texture was found in the ultrabasic xenoliths.The texture was filled with microcrystalline siliceous matters,carbonaceous matter,carbonates and phlogolites,and these matters were intergrowth with amphibole resulted from replacement.The mineral assemblages indicates the characters of mantle fluids of obvious metasomatism.It is considered that the silicon-alkali-rich fluids,were mantle fluids.The fluids were consanguineous with alkali-rich magma and originated from enriched mantle,and its function and energy are much powerful than crust fluids.This paper revealed the deep geologic process of large-scale mineralization in studied areas.

Seismic detection and distribution of reef-bank complex in langlitage formation of upper ordovician,hetian river area,tarim basin

Abstract: Reef-bank bodies are favorable for developing carbonate reservoirs.By the study of seismic stratigraphy of Lanlitage Formantion through the data of drilling,well logging and seismic profiles in Hetian river area,the seismic indicators of reef-bank comolex were obtained,their distribution was described,and a retrograding model for the development of reef-bank complex was established.The analysis of the relationship between the reef-bank complex and paleo-uplift,as well as the edge of slope,indicates that the distribution of reef-bank complex was controlled by the paleo-uplift.The reef-bank complex generally distributed as belt along the axis of the paleo-uplift from SW to NE.Two sub-belts corresponded to local structural belt within the paleo-uplift was recognized,one is SW-NE,other one is SE-NW.The SW-NE is the main one,extending to Tazhong paleo-uplift.With the effect of successively rising of sea level in the early time of Later Ordovician,the reef-bank complex retrograded from the edge of platform to the top area of the paleo-uplift,so that their scope decreased upward,and they mainly occurred in the lower to middle para-sequences.As the slope was very flat,the reef-bank bodies detected from seismic profiles may be the banks mainly.It is not suitable for the development of reefs in this area.