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1.
《Applied Geochemistry》1998,13(5):631-642
A new method for the determination of dissolved gas species in natural waters is presented. The method is suitable for field operations and ensures the preservation of the sample until analysis in the laboratory. This method is based on the equilibrium partition of gases between a liquid and a gaseous phase after the introduction of host gas. The host gas used depends on the gas species to be determined and on the technical features of the gas chromatograph. In this work pure Ar has been used. After shaking the sample for 5 min, a portion of gas was taken for gas chromatography analysis. From the concentration of gases in the gaseous phase and taking into account the partitioning coefficients of the various species, it is possible to derive the quantity of dissolved gases per litre of water and the partial pressures of the various gas species in equilibrium with water. This method has been applied to several samples of thermal water from Vulcano island. Helium and CO2 partial pressures of analysed samples were appreciably higher than those typical of waters in equilibrium with the atmosphere, thus indicating processes of interaction between the volcanic gases and groundwaters.  相似文献   

2.
天然气研究中的稀有气体地球化学应用模式   总被引：7，自引：1，他引：7  
沈平  徐永昌 《沉积学报》1995,13(2):48-58
在对天然气稀有气体地球化学特征进行系统研究的基础上，建立了有关氦、氩同位素组成的横“人”字型的成因模式并提出两种成因类型:Ａ、壳－幔复合型；Ｂ、壳源型。同时，还论述了稀有气体的年代积累效应与气源对比，进行了大、中型气区天然气地球化学综合研究。  相似文献   

3.
The geochemistry of formation waters in the Molasse basin of Upper Austria has been investigated to ascertain the extent of meteoric water replacement of the connate interstitial fluids in these sediments. The chemistry, isotopic composition, and dissolved gas contents of the groundwaters and of oil and gas associated brines have been determined. The most superficial sediments of the basin, the Innviertel (Miocene), have been completely flushed by meteoric waters within the last 200 ka. The underlying Hall and Puchkirchen formations (Miocene/Oligocene) form gas reservoirs for biogenic methane, and the associated formation waters are chemically and isotopically modified connate brines of the original marine deposition. In the northeastern part of the basin, the connate brines of the deeper sediments (Cretaceous/Jurassic) have been partially or completely replaced by meteoric waters, whereas in the south of the basin these sediments contain high salinity fluids which are substantially of connate origin. These conclusions are supported by the stable isotope composition of the various brines. Oil-associated brines from the Eocene sediments contain large amounts of dissolved radiogenic40Ar, which suggests that the oils have migrated from high-temperature environments. This is in contrast with the Puchkirchen, for which the observed absence of radiogenic40Ar suggests that the biogenic methane has been formed in situ. The4He contents of these brines and of the Cretaceous/Jurassic groundwaters are, however, less than those in the overlying Puchkirchen formation and suggest that He has been removed from the deeper sediments as a result of flushing by meteoric water. The ratios of dissolved methane and nitrogen to argon increase with increasing ammonium content of the formation waters. All of these parameters may be used as indices for the maturation of the system. The heavy noble gases, Kr and Xe, are abnormally abundant in the dissolved gases, and this is attributed to geochemical concentration of these gases by adsorption onto shales in the sediment sequence. The overall geochemical situation confirms the existence of separate hydraulic systems with little interconnection in the several overlying geological horizons.  相似文献   

4.
济阳坳陷高青-平南发育多个CO_2气藏,对气藏组分、同位素以及组分同位索相关组合进行分析,认为气藏中CO_2主要是幔源-岩浆成因.气藏同时具有高~(40)Ar/~(36)Ar和高~3He/~4He值表明:气藏中稀有气体主要来自幔源,同时有部分壳源混入;气藏中~4He/~(40)Ar~*平均值为2.15,说明该地区气藏形成主要以岩浆缓慢脱气为主,大规模CO_2及稀有气体是岩浆冷却结晶阶段所释放.其形成机理为:在随岩浆上升的过程中,随着压力和温度不断下降以及岩浆成分的变化,岩浆中CO_2及稀有气体溶解度也随之降低并析出,产生的大量CO_2及稀有气体沿着深大断裂及一些二、三级断裂交汇处输送至地层的各类圈闭中,并在适当的位置聚集成藏.  相似文献   

5.
The distribution of He and Ar isotopes has been studied in 41 rock samples and seven monomineralic fractions from ore-bearing layered units and poorly differentiated host gabbronorite of the Western Pana mafic–ultramafic pluton on the Kola Peninsula. The gases assigned for mass-spectrometric analysis were released by means of whole-rock sample melting and by comminution mainly from fluid microinclusions. The data show that the present-day isotopic composition of noble gases in rocks from the pluton is caused by many factors: the degree of melt degassing, various concentrations and retention of the trapped isotopes, the contents of radioactive elements, and the generation and loss of radiogenic gases. The hypabyssal conditions of pluton formation facilitate the loss of primary mantle-derived volatile components and the dilution of magmatic fluid with near-surface paleometeoric waters containing air dissolved therein. The correlation of noble gas isotopes and ore-forming chemical elements does not suggest derivation of the latter from crustal material and evidences their mantle origin. Variations in the geochemical indices of the gas corroborate previously established or proposed multistage formation of the pluton, mainly, the autometamorphic character of postmagmatic processes and the participation of fluids in ore formation.  相似文献   

6.
The contents and ratios of helium and argon isotopes were studied in rocks of the Lovozero Massif and related rare-metal (loparite) deposits. The gases were extracted by melting (from whole-rock and mineral samples) and crushing (mainly from fluid inclusions) methods. The wide variations in the He and Ar isotopic compositions can be explained by the fact that the trapped fluid represents a mixture of variable proportions of mantle, crustal, and atmogenic components and radiogenic in situ produced gas. The obtained gas-geochemical data reflect the complex evolution of the considered ore-magmatic system and the similar trends of melt evolution and complementary fluid phase in the magmatic chamber, in general, in three-rock (urtite-foyaite-lujavrite) units and, in each individual layers, the relative closeness of the system during magmatic crystallization and initial epimagmatic processes. It was also found that the earliest magmatic mineral was loparite and that ore units and mineralization could be partially transformed during a comparatively late postmagmatic stage. An important role of paleometeoric waters in the low-temperature mineral formation was shown.  相似文献   

7.
This paper reviews various coal seam gas (CSG) models that have been developed for the Sydney Basin, and provides an alternative interpretation for gas composition layering and deep-seated CO2 origins. Open file CSG wells, supplemented by mine-scale information, were used to examine trends in gas content and composition at locations from the margin to the centre of the basin. Regionally available hydrochemistry data and interpretations of hydrodynamics were incorporated with conventional petroleum well data on porosity and permeability. The synthesised gas and groundwater model presented in this paper suggests that meteoric water flow under hydrostatic pressure transports methanogenic consortia into the subsurface and that water chemistry evolves during migration from calcium-rich freshwaters in inland recharge areas towards sodium-rich brackish water down-gradient and with depth. Groundwater chemistry changes result in the dissolution and precipitation of minerals as well as affecting the behaviour of dissolved gases such as CO2. Mixing of carbonate-rich waters with waters of significantly different chemistries at depth causes the liberation of CO2 gas from the solution that is adsorbed into the coal matrix in hydrodynamically closed terrains. In more open systems, excess CO2 in the groundwater (carried as bicarbonate) may lead to precipitation of calcite in the host strata. As a result, areas in the central and eastern parts of the basin do not host spatially extensive CO2 gas accumulations but experience more widespread calcite mineralisation, with gas compositions dominated by hydrocarbons, including wet gases. Basin boundary areas (commonly topographic and/or structural highs) in the northern, western and southern parts of the basin commonly contain CO2-rich gases at depth. This deep-seated CO2-rich gas is generally thought to derive from local to continental scale magmatic intrusions, but could also be the product of carbonate dissolution or acetate fermentation.  相似文献   

8.
长白山天池火山区深部流体成分及其稳定同位素组成   总被引：17，自引：1，他引：17       下载免费PDF全文
天池火山区深部流体成分和稳定同位素组成特征指示,该区地下有相对独立的四个含水层。2.2km以上为冷水层,2.2-3.4km、3.5-3.9km、4km以下分别为上部、中部和深部热水层。现代水热活动均伴随强烈的深源气体释放,碳和氦同位素比值揭示,这些气体属幔源气体,其中仅混入少量大气,壳源物质混染不明显。大规模幔源气体释放主要集中在天池火山湖周围,这表明该区地壳浅部可能存在一定规模的热的幔源岩浆体。据碳同位素地质测温估算,该岩浆体的热变质带顶部距地面约5km.气体动态变化显示该岩浆体目前处在不稳定期,值得引起重视。  相似文献   

9.
本文对渤海湾盆地、四川盆地和鄂尔多斯盆地等天然气产区41个不同深度、不同时代和不同岩性的油气源岩和储集岩利用K-Ar年龄测定法进行K、Ar分析、表面年龄测定和粘土矿物分析,探讨了沉积岩中钾、氩的时代和区域分布特征及泥质岩钾含量与粘土矿物中伊利石含量的关系,并对泥质岩和碳酸盐岩的钾氩分布进行对比研究,指出了沉积岩钾丰度的时代演化旋回及其特点.并讨论了岩石中的钾氩来源及赋存状态以及天然气中氩的来源及其进入气藏的运移机理.  相似文献   

10.
李书舜  刘大成 《沉积学报》1988,6(3):112-117
四川晚二叠世龙潭期和长兴期具有特殊的硅质来源,属于富含硅质的台盆相。本文根据礁体生长的古构造和沉积环境的分析,探讨控制生物礁成群成排分布的机理。指出礁体的形成与成滩有密切关系。  相似文献   

11.
This work reports the results of noble gas (Ne, Ar, Kr, Xe) analyses of accidental mantle xenoliths from San Carlos, Arizona. Except for the addition of radiogenic 40Ar and mass fractionation effects, the isotopic structures of these gases are indistinguishable from atmospheric composition. The absence of 129Xe excesses in these rocks may reflect indirect mixing of atmospheric gases with the source region of the xenoliths. The dominant influence on the noble gas abundances in the San Carlos xenoliths appears to have been diffusive gas loss, which may have occurred in a mantle metamorphic event or during contact with the host basanite magma. Evidence is presented for the partitioning of significant amounts of the heavy noble gases into fluid inclusions in the xenolith minerals; the proportion of each gas in the inclusions increases with increasing atomic weight of the gas, possibly reflecting solubility effects. The noble gases are present in greater concentration in pyroxenes than in olivine, similar to the behavior of other incompatible elements.  相似文献   

12.
中国最古老的气藏--四川威远震旦纪气藏   总被引：15，自引：1，他引：15  
本文研究了中国最大的气田--四川威远气田的气体组分和碳、氢、硫、氩、氦同位素组成。其特征如下:（1）震旦纪气藏相对于其它气藏具有高氮（9％），高CO2+H2S（5％）和高氦（0.18％），高氩（0.05％）的特征；（2）震旦纪气藏的氩同位素组成为4400-9255，平均7000，显示了很高的年代积累效应。3He/4He比值低为n×10-8，这意味着威远气藏中的氦主要来自壳源物质；（3）He/Ar丰度为5.39-6.14，是笔者研究过的天然气中的最低值；（4）N2/Ar,N2/He浓度具有较好线性关系；（5）碳、氢、硫、氩同位素丰度比可将三叠纪、二叠纪、寒武纪、震旦纪气藏明显加以区分，证明各自属不同气源。（6）震旦系岩石吸咐烃和储气层气体的C2/C3有良好的对比性。因此，笔者认为:震旦系气藏为自生自储。稀有气体不具地幔物质特征，但不排斥有幔源物质加入的可能。  相似文献   

13.
测试并分析了柴北缘各油气田的14个天然气样品的氦、氩稀有气体同位素比值,并进行了气源对比。研究发现,柴北缘天然气40Ar/36Ar值分布在951～1712,平均1098,多数样品40Ar/36Ar较通常认为源于侏罗系的天然气40Ar/36Ar明显偏高,研究认为本区不存在幔源高40Ar/36Ar流体的介入,储层年代效应也不可能造成天然气40Ar/36Ar明显偏高,因此柴北缘天然气40Ar/36Ar明显偏高,主要是由于源岩年代积累效应引起的。据估算,气源岩年龄分布范围为164.7～460.8Ma,平均为345.1Ma,可能多数来源于石炭系。这一认识得到了柴北缘广泛分布有石炭系源岩和已发现源于石炭系原油的支持。柴北缘石炭系天然气的发现预示了柴北缘石炭系是一个新的油气勘探层系,从而拓展了柴北缘天然气勘探领域。  相似文献   

14.
Natural fluid phases at high temperatures and low pressures   总被引：1，自引：0，他引：1  
Gas phases at low pressures and high (magmatic) temperatures have certain peculiar properties. The fluid is mainly water vapour, which is usually observed during discharging of crystal magmatic melts. At >700°C and <100 bar these peculiar properties include: formation of near ‘dry' salt melts as second fluid phase, very strong fractionation of hydrolysis products between vapour and melts, subvalence state of metals during transport processes, and high sensitivity of the gas to conditions of sublimate precipitation. Phase diagram analysis as well as results of field and laboratory experiments are presented in this article. The processes could be a model for industrial technologies to clean wastes from toxic, rare and heavy metals. Transport forms of some elements in volcanic gases are very similar to the species which were formed first in the protosolar nebula.  相似文献   

15.
The concentration and the isotopic ratios of noble gases He, Ne, Ar, Kr and Xe were measured in porewater trapped in shallow sediments of the estuary of the St-Lawrence River, Québec, Canada. The gases are atmospheric in origin but most samples have gas concentrations 1.7-28 times higher than those expected in solution in water at equilibrium with the atmosphere. Elemental fractionation of heavier noble gases Kr and Xe compared to Ar strongly suggests that noble gases were adsorbed on sediments or organic matter and then desorbed into porewaters due to depressurization, as collected samples were brought to the surface. Atmospheric Ar in porewater is used as a reference to measure the N2-fluxes at the water-sediment interface. Ignoring the Ar enrichments observed in porewater could lead to a severe underestimation of the denitrification rate in oceans and estuaries.  相似文献   

16.
Geothermal systems ancient and modern: a geochemical review   总被引：1，自引：0，他引：1  
R.W. Henley  A.J. Ellis 《Earth》1983,19(1):1-50
Geothermal systems occur in a range of crustal settings. The emphasis of this review is on those occurring in regions of active or recently active volcanism, where magmatic heat at depths up to 8 km leads to convection of groundwater in the upper crust. Hot water (and steam) flows are controlled by the permeability of the crust and recent data have emphasised the dominance of secondary permeability, especially fractures. Drilling to depths of up to 3 km in these systems encounters near-neutral pH alkali chloride waters with temperatures up to about 350°C and chloride contents generally in the range 500 to 15,000 mg kg?1 although much higher salinities are encountered in some systems such as in the Imperial Valley, California. Stable isotope studies indicate the predominance of a meteoric source in the majority of geothermal systems although seawater predominates in some regions, such as Reykjanes, Iceland. Mixing of waters from both sources also occurs in some systems and some magmatic fluid may also be present.The major element geochemistry of geothermal fluids is determined by a set of temperature-dependent mineral-fluid equilibria although chloride and rare gas contents appear to be independent variables reflecting the sources of these components (sedimentary or volcanic rocks, seawater, magmatic fluids, etc).Boiling in the upper portion of geothermal systems is accompanied by the transfer of acidic gases (CO2 and H2S) to the resultant steam which may penetrate the surface as fumarolic activity or become condensed into shallow groundwaters giving rise, with oxidation, to distinctive low pH sulphate bicarbonate water.Fluid inclusion, stable isotope and mineral alteration studies have led to the recognition in many Tertiary hydrothermal ore deposits of physical and chemical environments analogous to those encountered in the present-day systems. The vein-type gold-silver, Carlin-type gold and porphyry-type copper-molybdenum deposits of the western United States are particularly well studied examples. Sub-ocean floor equivalents of the terrestrial geothermal systems have been recognized in ocean floor spreading centres such as the East Pacific Rise and deep-sea submersible vehicles have allowed visual observation of sea floor hot springs actively depositing metal sulphides. These environments may parallel those of the Cyprus-type massive sulphide depositing systems, while sub-sea floor systems of the type responsible for Kuroko-type massive sulphide deposits may eventually be encountered in island are settings.  相似文献   

17.
Two distinctive magmatic fluids were recognized in the Tatun volcanic group (TVG), Taiwan. One is a relatively reduced fluid represented by the fumarolic gases at Hsiao-you-ken (HYK) geothermal field. Another is an oxidized fluid containing high concentrations of HCl represented by the fumarolic gases at Da-you-ken (DYK). An intermediate gas was recognized at Gung-tze-ping (GTP) and She-hung-ping (SHP). The fumarolic gases at HYK and GTP possess the features of so-called primary steam generated on mixing of magmatic gas and meteoric groundwater. The fumarolic gases at DYK are a simple mixture between magmatic gas and water vapor of meteoric origin. The CO2/H2O molar ratio of the magmatic component in the fumarolic gases at DYK was estimated to be 0.018, meanwhile it was estimated to be 0.027 for the fumarolic gases at HYK and GTP, suggesting the magma beneath DYK is depleted in volatiles relative to the magma beneath HYK and GTP. The estimated CO2/H2O ratio for the magmatic component is comparable to that of some active volcanoes in Japan, suggesting the enrichment of volatiles in the magmas beneath TVG.  相似文献   

18.
广东三水盆地天然气非烃组分同位素地球化学   总被引：1，自引：0，他引：1  
根据广东省三水盆地天然气中氦、氩、二氧化碳和氮等非烃组分的稳定同位素地球化学特征,探讨了该区天然气的来源以及大地热流。测得天然气中3He/4He（R）值为（1.60-6.36）×10-6,比大气的3Ne/4He（Ra）值(1.4×10-6)大:氩的稳定同位素组成(40Ar/36Ar=450-841)较大气氩富40Ar;二氧化碳的δ13C（PDB）值在-20-2‰的范围内,δ13N（Air）值在-57-+95‰之间:根据（?）He,4He值求得研究区的大地热流值（Q）为72-82mWm-2。大地热流和非烃组分同位素组成的高值以及研究区特别发育的火山岩等地质资料表明三水盆地有较强的地球深部流体（物质的和热的）向上溢出。一些油气藏中相当一部分氦、氩和氮来自地幔,各种天然气中均混有地壳来源的非烃气体。贫13C的二氧化碳气主要为地层中有机质分解的产物;富13C的二氧化碳则主要来自岩石化学反应的产物,并混有深部来源的二氧化碳。相当一部分大地热流源于上地幔。  相似文献   

19.
Numerous present-day hot springs and associated ancient Lianghe gold deposit occur in the central Tengchong block, SW China, associated with oceanic crust subduction. From the center outwards, the alteration zones in the hot spring of the Rehai consist of alunite and silica in a breccia zone, a kaolinite and illite zone, and a chlorite, illite, kaolinite zone. The gas phase in the hot spring is dominated by CO2 with δ13C ranging from −4.5‰ to −7.2‰. These features indicate a major magmatic origin of the hot spring gas. The 3He/4He ratios in the gas from central Tengchong vary from 1.56 to 5.88, approaching to those of the MORB. This is probably related to the ongoing subduction of the Indian plate beneath the Tengchong block. The hot spring waters in the central Tengchong block have much higher content of Au and other elements, e.g., Ag, As, Sb, and Tl, than other typical hot springs, such as Hasbrouck, Sulfer, etc. in the world. The hot springs with more mantle gas contribution and higher water temperature show more elevated Au contents, which implies that the metal in the hot spring was most likely contributed from the magmatic gas. The compiled D-O isotopes of the hot spring waters from previous studies suggest that they are primarily derived from meteoric water. A genetic model for the hot spring system in the central of Tengchong has been tentatively established. The gold-charged hot spring is genetically connected to an active magma chamber, which was produced by subduction of oceanic crust. The chamber is driving long-term surface meteoric circulation and constantly releasing magmatic volatiles enriched with metals. As hot spring water mixed with magmatic volatiles, causing decompression-boiling and forming hydraulic fractures to penetrate the roof of siliceous sinter, which induced the continuing metal deposition and formed the Lianghe hot spring.  相似文献   

20.
Identification of the source of CO2 in natural reservoirs and development of physical models to account for the migration and interaction of this CO2 with the groundwater is essential for developing a quantitative understanding of the long term storage potential of CO2 in the subsurface. We present the results of 57 noble gas determinations in CO2 rich fields (>82%) from three natural reservoirs to the east of the Colorado Plateau uplift province, USA (Bravo Dome, NM., Sheep Mountain, CO. and McCallum Dome, CO.), and from two reservoirs from within the uplift area (St. John’s Dome, AZ., and McElmo Dome, CO.). We demonstrate that all fields have CO2/3He ratios consistent with a dominantly magmatic source. The most recent volcanics in the province date from 8 to 10 ka and are associated with the Bravo Dome field. The oldest magmatic activity dates from 42 to 70 Ma and is associated with the McElmo Dome field, located in the tectonically stable centre of the Colorado Plateau: CO2 can be stored within the subsurface on a millennia timescale.The manner and extent of contact of the CO2 phase with the groundwater system is a critical parameter in using these systems as natural analogues for geological storage of anthropogenic CO2. We show that coherent fractionation of groundwater 20Ne/36Ar with crustal radiogenic noble gases (4He, 21Ne, 40Ar) is explained by a two stage re-dissolution model: Stage 1: Magmatic CO2 injection into the groundwater system strips dissolved air-derived noble gases (ASW) and accumulated crustal/radiogenic noble gas by CO2/water phase partitioning. The CO2 containing the groundwater stripped gases provides the first reservoir fluid charge. Subsequent charges of CO2 provide no more ASW or crustal noble gases, and serve only to dilute the original ASW and crustal noble gas rich CO2. Reservoir scale preservation of concentration gradients in ASW-derived noble gases thus provide CO2 filling direction. This is seen in the Bravo Dome and St. John’s Dome fields. Stage 2: The noble gases re-dissolve into any available gas stripped groundwater. This is modeled as a Rayleigh distillation process and enables us to quantify for each sample: (1) the volume of groundwater originally ‘stripped’ on reservoir filling; and (2) the volume of groundwater involved in subsequent interaction. The original water volume that is gas stripped varies from as low as 0.0005 cm3 groundwater/cm3 gas (STP) in one Bravo Dome sample, to 2.56 cm3 groundwater/cm3 gas (STP) in a St. John’s Dome sample. Subsequent gas/groundwater equilibration varies within all fields, each showing a similar range, from zero to ∼100 cm3 water/cm3 gas (at reservoir pressure and temperature).  相似文献   

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