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1.
《Applied Geochemistry》2002,17(11):1457-1466
Ocean Drilling Program (ODP) Leg 169, which was conducted in 1996 provided an opportunity to study the gas geochemistry in the deeper part of the sediment-rich hydrothermal system in Escanaba Trough. Gas void samples obtained from the core liner were analyzed and their results were compared with analytical data of vent fluid samples collected by a submersible dive program in 1988. The gas geochemistry of the pore fluids consisted mostly of a hydrothermal component and was basically the same as that of the vent fluids. The He isotope ratios (R/RA=5.6–6.6) indicated a significant mantle He contribution and the C isotopic compositions of the hydrocarbons [δ13C(CH4)=−43‰, δ13C(C2H6)=−20‰] were characterized as a thermogenic origin caused by hydrothermal activity. On the other hand, the pore fluids in sedimentary layers away from the hydrothermal fields showed profiles which reflected lateral migration of the hydrothermal hydrocarbons and abundant biogenic CH4. Helium and C isotope systematics were shown to represent a hydrothermal component and useful as indicators for their distribution beneath the seafloor. Similarities in He and hydrocarbon signatures to that of the Escanaba Trough hydrothermal system were found in some terrestrial natural gases, which suggested that seafloor hydrothermal activity in sediment-rich environments would be one of the possible petroleum hydrocarbon generation scenarios in unconventional geological settings.  相似文献   

2.
Orthopyroxene, clinopyroxene, and olivine from a metasomatized mantle xenolith of garnet lherzolite in alkaline rocks at the Jetty Oasis, East Antarctica, contain numerous carbon dioxide-dominated composite melt-fluid and fluidized sulfide-silicate (±carbonate) inclusions. Although the maximum pressure under which the inclusions were captured by rock-forming minerals was evaluated at 13 kbar, its actual value should have been much higher, judging by the fact that the inclusions have lost part of their material (decrepitated) when the xenolith was brought to the surface. Two major fluid populations are distinguished. The fluids entrapped during the earlier episode have a more complicated composition. Dominated by CO2, these fluids contain much N2 (0.1–0.2 mole fractions), H2S, and perhaps, also H2O and are hosted by sulfide-silicate (±carbonate) inclusions produced by liquid immiscibility. As these inclusions evolved, they enriched in CO2 and depleted in H2S and N2. Although the concentrations of N2, H2S, and H2O were generally relatively low, these components played an important role in mantle metasomatism, as is reflected in the geochemistry of the derived magmas. The fluids of the younger episode (pressures lower than 7 kbar) are notably richer not only in CO2 but also in H2O (up to the appearance of inclusions with a liquid aqueous phase and the formation of CO2 gas hydrate when cooled in a cryometric stage by liquid N2). The effect of fluids on the mantle source in two discrete episodes is also confirmed by isotopic-geochemical data. Isotopic data on gases obtained immediately from fluid inclusions in minerals by the stepwise crushing technique provide evidence of the evolution of elemental and isotopic ratios of the gases in the course of the metasomatic processes. The high-pressure fluid inclusions of the earlier episode have low C/N2, C/Ar, and N2/Ar ratios, isotopically heavy N2, and somewhat elevated (to 530) 40Ar/36Ar ratios. The younger fluids typically have higher (by two to three orders of magnitude) C/N2 and C/Ar ratios, lower δ13C of CO2, and N2/Ar and 40Ar/36Ar ratios close to the atmospheric values. The nitrogen and argon isotopic compositions and elemental ratios suggest that the younger fluids could have been produced by two-component mixing in the mantle-atmosphere system. Comprehensive analysis of the data and in particular the 40Ar/36Ar ratios, which are atypical of the mantle, and an increase in the H2O concentration, suggests a subduction-related nature of the fluids.  相似文献   

3.
《Applied Geochemistry》1998,13(7):815-824
Various sources for hydrothermal CH4 have been proposed over the years. While C isotope studies have narrowed the possibilities, enough higher hydrocarbon gas data now exist both to supplement the isotopic data and to permit additional deductions regarding origins. Comparison of typical C1–C6 data for gases of various origins (from sedimentary and crystalline rocks, and hydrothermal systems) reveals certain characteristics. Apart from isotopic differences, hydrothermal hydrocarbons differ from sedimentary hydrocarbons mainly in possessing tendencies towards a relative excess of CH4, higher normal/iso ratios for butane and pentane, and relatively high amounts of C6 gases. Despite these differences, consideration of the evidence indicates that hydrothermal hydrocarbon gases in most cases originate like sedimentary basin gases by thermal degradation of organic matter in the relatively shallow subsurface. The principal characteristic of these hydrothermal gases, “excess” CH4, appears to have a geothermometric function. The following empirical relationship has been derived: t°C=57.8 log(CH4/C2H6)+96.8, which fits moderately well a range of geothermal fields worldwide. This gas geothermometer may be particularly applicable during geothermal exploration in areas where there is little direct knowledge of subsurface conditions.  相似文献   

4.
Studies of the mantle-derived iherzolites from Nushan show that in addition to CO2,there were present H2O and small amounts of CO, CH4, SO2,Cl and F in the initial mantlc fluids derived fron the asthenospheric mantlc plumc .The imitial fluids accumulated in some regions of the mantle, resulting in lowering of the mantle solidus (and liquidus) and partial melting of the upper mantle. Melts formed from low-degree of fluid-involved partial melting of the upper mantle would be highly enriched in incompatible elements.Fluies and melts are allthe metasomatic agents for mantle metasomatism, and the interaction between them and the depleted mantle could result in the substan-tial local enrichment of LREE and incompatible elements in the latter.In case that the concentration of H2O in the fluids (and melts) is lower ,only cryptic metasomatism would occur, in case that the concentration of H2O is higher,the degree of partial melting would be higher and hydrous metasomatic phases(e.g. amphiboles )would nucleate. Under such circumstances, there would occur model metasomatism.  相似文献   

5.
Deep fluids in a petroliferous basin generally come from the deep crust or mantle beneath the basin basement, and they transport deep substances(gases and aqueous solutions) as well as heat to sedimentary strata through deep faults. These deep fluids not only lead to large-scale accumulations of CO_2, CH_4, H_2, He and other gases, but also significantly impact hydrocarbon generation and accumulation through organic-inorganic interactions. With the development of deep faults and magmatic-volcanic activities in different periods, most Chinese petroliferous basins have experienced strong impacts associated with deep fluid activity. In the Songliao, Bohai Bay, Northern Jiangsu, Sanshui, Yinggehai and Pearl Mouth Basins in China, a series of CO_2 reservoirs have been discovered. The CO_2 content is up to 99%, with δ~(13)C_(CO2) values ranging from-4.1‰ to-0.37‰ and ~3He/~4He ratios of up to 5.5 Ra. The abiogenic hydrocarbon gas reservoirs with commercial reserves, such as the Changde, Wanjinta, Zhaozhou, and Chaoyanggou reservoirs, are mainly distributed in the Xujiaweizi faulted depression of the Songliao Basin. The δ~(13)CCH4 values of the abiogenic alkane gases are generally -30‰ and exhibit an inverse carbon isotope sequence of δ~(13)C_(CH4)δ~(13)C_(C2H6)δ~(13)C_(C3H8)δ~(13)C_(C4H10). According to laboratory experiments, introducing external H_2 can improve the rate of hydrocarbon generation by up to 147% through the kerogen hydrogenation process. During the migration from deep to shallow depth, CO_2 can significantly alter reservoir rocks. In clastic reservoirs, feldspar is easily altered by CO_2-rich fluids, leading to the formation of dawsonite, a typical mineral in high CO_2 partial pressure environments, as well as the creation of secondary porosity. In carbonate reservoirs, CO_2-rich fluids predominately cause dissolution or precipitation of carbonate minerals. The minerals, e.g., calcite and dolomite, show some typical features, such as higher homogenization temperatures than the burial temperature, relatively high concentrations of Fe and Mn, positive Eu anomalies, depletion of 18 O and enrichment of radiogenic ~(87)Sr. Due to CO_2-rich fluids, the development of high-quality carbonate reservoirs is extended to deep strata. For example, the Well TS1 in the northern Tarim Basin revealed a high-quality Cambrian dolomite reservoir with a porosity of 9.1% at 8408 m, and the Well ZS1 C in the central Tarim Basin revealed a large petroleum reserve in a Cambrian dolomite reservoir at ~6900 m. During the upward migration from deep to shallow basin strata, large volumes of supercritical CO_2 may extract petroleum components from hydrocarbon source rocks or deep reservoirs and facilitate their migration to shallow reservoirs, where the petroleum accumulates with the CO_2. Many reservoirs containing both supercritical CO_2 and petroleum have been discovered in the Songliao, Bohaiwan, Northern Jiangsu, Pearl River Mouth and Yinggehai Basins. The components of the petroleum trapped with CO_2 are dominated by low molecular weight saturated hydrocarbons.  相似文献   

6.
High pressure experimental studies of the melting of lherzolitic upper mantle in the absence of carbon and hydrogen have shown that the lherzolite solidus has a positive dP/dT and that the percentage melting increases quite rapidly above the solidus. In contrast, the presence of carbon and hydrogen in the mantle results in a region of ‘incipient’ melting at temperatures below the C,H-free solidus. In this region the presence or absence of melt and the composition of the melt are dependent on the amount and nature of volatiles, particularly the CO2, H2O, and CH4 contents of the potential C-H-O fluid. Under conditions of low (IW to IW + 1 log unit atP ∼ 20–35kb), fluids such as CH4+H2O and CH4+H2 inhibit melting, having a low solubility in silicate melts. Under these conditions, carbon and hydrogen are mobile elements in the upper mantle. At slightly higher oxygen fugacity (IW+2 log units,P∼20–35 kb) fluids in equilibrium with graphite or diamond in peridotite C-H-O are extremely water-rich. Carbon is thus not mobile in the mantle in this range and the melting and phase relations for the upper mantle lherzolite approximate closely to the peridotite-H2O system. Pargasitic amphibole is stable to solidus temperatures in fertile lherzolite compositions and causes a distinctive peridotite solidus, the ‘dehydration solidus’, with a marked change in slope (a ‘back bend’) at 29–30kb due to instability of pargasite at high pressure. Intersections of geothermal gradients with the peridotite-H2O solidi define the boundary between lithosphere (subsolidus) and asthenosphere (incipient melt region). This boundary is thus sensitive to changes in [affecting CH4:H2O:CO2 ratios] and to the amount of H2O and carbon (CO2, CH4) present. At higher conditions (IW + 3 log units), CO2-rich fluids occur at low pressures but there is a marked depression of the solidus at 20–21 kb due to intersection with the carbonation reaction, producing the low temperature solidus for dolomite amphibole lherzolite (T∼925°C, 21 to >31kb). Melting of dolomite (or magnesite) amphibole lherzolite yields primary sodic dolomitic carbonatite melt with low H2O content, in equilibrium with amphibole garnet lherzolite. The complexity of melting in peridotite-C-H-O provides possible explanations for a wide range of observations on lithosphere/asthenosphere relations, on mantle melt and fluid compositions, and on processes of mantle metasomatism and magma genesis in the upper mantle.  相似文献   

7.
Basalts interbedded with oil source rocks are discovered frequently in rift basins of eastern China, where CO2 is found in reservoirs around or within basalts, for example in the Binnan reservoir of the Dongying Depression. In the reservoirs, CO2 with heavy carbon isotopic composition (δ13C>-10‰ PDB) is in most cases accounts for 40% of the total gas reserve, and is believed to have resulted from degassing of basaltic magma from the mantle. In their investigations of the Binnan reservoir, the authors suggested that the CO2 would result from interactions between the source rocks and basalts. As the source rocks around basalts are rich in carbonate minerals, volcanic minerals, transition metals and organic matter, during their burial history some of the transition metals were catalyzed on the thermal degradation of organic matter into hydrocarbons and on the decomposition of carbonate minerals into CO2, which was reproduced in thermal simulations of the source rocks with the transition metals (Ni and Co). This kind of CO2 accounts for 55%-85% of the total gas reserve generated in the process of thermal simulation, and its δ13C values range from -11‰- -7.2‰ PDB, which are very similar to those of CO2 found in the Binnan reservoir. The co-generation of CO2 and hydrocarbon gases makes it possible their accumulation together in one trap. In other words, if the CO2 resulted directly from degassing of basaltic magma or was derived from the mantle, it could not be accumulated with hydrocarbon gases because it came into the basin much earlier than hydrocarbon generation and much earlier than trap formation. Therefore, the source rocks around basalts generated hydrocarbons and CO2 simultaneously through catalysis of Co and Ni transition metals, which is useful for the explanation of co-accumulation of hydrocarbon gases and CO2 in rift basins in eastern China.  相似文献   

8.
H2S and CO2 are found in elevated concentrations in the reservoirs near the Carboniferous–Ordovician unconformity in the Hetianhe Field of the Tarim Basin, NW China. Chemical and isotopic analyses have been performed on produced gases, formation waters and reservoir rocks to determine the origin of CO2 and H2S and to explain the heterogeneous distribution of isotopic and geochemical characteristics of petroleum fluids. It is unlikely that H2S and CO2 had a mantle component since associated helium has an isotope ratio totally uncharacteristic of this source. Instead, H2S and CO2 are probably the result of sulphate reduction of the light hydrocarbon gases (LHG). Increasing H2S concentrations and CO2/(CO2+ΣC1–4) values to the west of the Hetianhe Field occur commensurately with increasingly heavy hydrocarbon gas δ13C values. However, thermochemical sulphate reduction is unlikely because the temperatures of the reservoirs are too low, no H2S or rare pyrite was detected in deeper reservoirs (where more TSR should have occurred) and inferred δ34S values of H2S (from late-stage pyrite in the Carboniferous and Ordovician reservoirs) are as low as −24.9‰. Such low δ34S values discount the decomposition of organic matter as a major source of H2S and CO2. Bacterial sulphate reduction of the light hydrocarbon gases in the reservoir, possibly coupled indirectly with the consumption of organic acids and anions is most likely. The result is the preferential oxidation of 12C-rich alkanes (due to the kinetic isotope effect) and decreasing concentration of organic acids and anions. Modern formation water stable isotope data reveal that it is possible that sulphate-reducing bacteria were introduced into the reservoir by an influx of meteoric water from the west by way of an inversion-related unconformity. This may account for the apparently stronger influence of bacterial sulphate reduction to the west of the Hetianhe Field, and the consequent greatest decrease of the δ13C-CO2 values and the greatest increase in δ13C values of the alkane gases.  相似文献   

9.
The Higher Himalayan Leucogranites (HHLG) intruded into the high grade rocks of the Higher Himalayan Crystallines (HHC) in western Arunachal Pradesh, eastern Himalaya, yield distinctive field data, petrography, geochemical and mineral chemistry data. The HHLG mostly occur as sill like bodies of limited thickness and lateral extent within the HHC. The Arunachal HHLG are characterized by the presence of two micas; normative corundum; high contents of SiO2 (67–78 wt.%), Al2O3 (13–18 wt.%), A/CNK (0.98–1.44) and Rb (154–412 ppm); low contents of CaO (0.33–1.91 wt.%) and Sr (19–171 ppm), and a high ratio of FeO(tot)/MgO in biotite (2.54–4.82). These distinctive features, along with their strong depletion in high field strength elements (HFSE), suggest their affinity to peraluminous S-type granite generated by the partial melting of crustal material. Since the HHLG associated with high grade rocks of HHC and lack of basaltic magmatism, strongly suggests that the high grade rocks of HHC might represent the melt source and HHLG are product of pure crustal melt without any contamination of mantle material. Geothermobarometric estimations and mineral assemblages of the HHC metapelites confirm that the HHLG were probably generated in the middle crust (～20 km) and the produced melts intruded the HHC in the form of sills/dykes.  相似文献   

10.
Simulation results of the equilibrium state of systems water-carbonaceous chondrite material, water-primary mantle material, water-ultramafic rock material, and water-mafic rock material open with respect to carbon dioxide and methane at 25°C, 1 bar indicate that highly alkaline reduced aqueous solutions with K/Na > 1 can be formed only if water is in equilibrium with compositions close to those of continental crust and primitive mantle. Yu.V. Natochin’s hypothesis that the living cell can be formed only in an aqueous environment with K/Na > 1 leads to the conclusion that terrestrial life could arise and further evolve on the Earth during the differentiation of primary chondritic material into the Earth’s core and mantle (during the first few million years of the planet’s lifetime) in an alkaline (pH 9–10) reduced (Eh = −400–500 mV) aqueous solution at a temperature of 50–60°C, in equilibrium with an N2-bearing atmosphere, which also contained CH4 (partial pressure from 10−2 to 10−8 bar), CO2 (partial pressure from 10−5 to 10−8 bar), NH3, H2, H2S, CO, and other gases.  相似文献   

11.
Literature data suggest that concentrated naphthides (CN)—bitumen and oil—can occur in intrusive and volcanic rocks of various silicity and alkalinity whose age ranges from the Proterozoic to Recent. The qualitative composition of heavy (high-molecular) hydrocarbons (HHC) in CN is the same in various rocks: heavy alkanes, polycyclic aromatic hydrocarbons (PAH), oxygen-bearing derivatives of hydrocarbons, etc. The presence of CN in rock-forming minerals in magmatic rocks and pegmatites confirms that CN condensed during the epimagmatic stage, and the molecular mass of the CN, for example, in the Khibina alkaline massif decreased with decreasing temperature simultaneously with the evolution of its mineral assemblages. The synthesis of CN continues during the hydrothermal stage, but high-temperature associations of HHC gave way during this stage to low-temperature ones. During all evolutionary stages of magmatic and related processes, the contents of CN are correlated with those of trace elements, which likely occur as organoelement compounds (OEC). Hypotheses of endogenic and exogenic genesis of CN in magmatic rocks are discussed. The endogenic hypotheses include HHC synthesis from inorganic gases and light hydrocarbons (HC) on catalytic minerals. The fact that HHC and CN occur in mantle xenoliths and high-pressure minerals and the results of experimental and thermodynamic modeling are discussed as supporting the hypothesis of the mantle genesis of CN in magmatic rocks. The metastable ascent of gaseous HHC, the low oxygen fugacity, and the high alkalinity of the melts could be favorable for the partial preservation of HHC in these rocks at crustal depth levels. Endogenic CN can serve as a nutrient medium for microorganisms in the upper lithosphere. Exogenic hypotheses for the genesis of HHC in magmatic rocks assume that the melts should have assimilated sedimentary rocks rich in organic matter and that biogenic oil could be transported from sedimentary reservoirs to magmatic rocks. An important role in determining the genesis of CN in magmatic rocks is played by endogenic and biogenic markers.  相似文献   

12.
Reconnaissance surface geochemical survey for adsorbed soil gas analysis conducted in Proterozoic Bhima and Kaladgi Basins, have revealed occurrence of anomalous concentrations of light gaseous hydrocarbons i.e. C1 to C4 (CH4, C2H6, C3H8, i-C4H10 and n-C4H10) in the near surface soils. The concentrations of C1 and ΣC2+(C2H6+C3H8+ i-C4H10+ n-C4H10) in Bhima and Kaladgi Basins are in the range of 1–2594 ppb and 1 to 57 ppb and 1–1142 ppb and 1–490 ppb, respectively. The carbon isotopic data of adsorbed soil gas methane in few selected samples are in the range of −29.9 to −39‰ (PDB). The evaluation of adsorbed soil gas data indicates that all the gas components are cogenetic and hydrocarbon ratios of C1/(C2+C3) < 10 and C3/C1*1000 between 60–500 and 20–60 suggest that the adsorbed gases are derived from oil and gas-condensate zones. The carbon isotopic values of methane further support thermogenic origin of these migrated gases. The concentration distribution of C1 and ΣC2+ in the study areas illustrate C1 and ΣC2+ anomalies near Katamadevarhalli, Andola and Talikota in Bhima Basin and near Kaladgi, Lokapur and north of Mudhol in Kaladgi Basin. The hydrocarbon anomalies near the surface coincide with the favourable subsurface structural features and correlate with existing geochemical and geophysical data in these basins suggesting seepage related anomalies.  相似文献   

13.
Previous research has shown that the Kaapvaal lithospheric mantle is generally reduced and characterised by a decreasing redox state with increasing depth. As a consequence, C-O-H fluids in the Kaapvaal lithospheric mantle are dominated by H2O, CH4, and C2H6. Thermodynamic calculations demonstrate that diamond precipitation from such a fluid during ascend is possible as it is exposed to a more oxidised environment and both CH4 and C2H6 are oxidised. However, the calculations also demonstrate that the diamond precipitation potential from such a fluid decreases when: (1) the mantle is either more reduced or oxidised compared to the Kaapvaal mantle, or (2) the change in temperature with pressure is smaller compared to that of the Kaapvaal mantle. Therefore, the presence of reduced mantle fluid species and a generally decreasing oxygen fugacity with increasing depth do not necessarily warrant diamond precipitation from a rising reduced fluid.  相似文献   

14.
The Dovyren layered dunite–troctolite–gabbro massif (northern Transbaikalia region, Russia) contains precious metal mineralization related to sparsely disseminated sulfides (Stillwater type). The distribution of gases trapped in micro-inclusions and intergranular pores of the Dovyren massif has been investigated. This type of study had previously only been undertaken on the traps or peridotite–pyroxenite–norite intrusions hosting copper–nickel sulfide deposits. A novel method of analyzing trapped gases, involving the grinding of samples under high vacuum at room temperature, was employed. A modified gas-chromatography and mass-spectrometry approach was used to analyze the composition of the extracted gases. The concentrations of reduced gases (CH4 and H2) are higher in inclusions trapped by silicate minerals, whereas oxidized gases (H2O, CO2) are less common. The content of reduced gases (H2, CH4, CO), N2, He, radiogenic Ar, and C2H6 increases upward through the layered series of the massif. The distribution of all gases, especially methane and hydrogen, show peak concentrations coincident with the PGE and gold reef type horizons. A correlation of the gas peaks and noble metal contents appears to be related to their geochemical affinities. This conclusion is supported by the experimental modeling. Received: 4 August 1999 / Accepted: 13 January 2000  相似文献   

15.
This study is focused on geothermal heat flow and the origin of non-hydrocarbons in natural gases in terms of the isotope geochemical characteristics of Ar, He, CO2 and N2 in natural gases from the Sanshui Basin, Guangdong Province. China.3He/4He ratios are of (1.60-6.39) × 10-6, and40Ar/36Ar ratios of 450–841. The carbon isotopic composition (δl3C PDB) of carbon dioxide ranges from -20‰ to -2‰. δl5N(air) ratios have a wider range of-57 ‰- +95 ‰. The isotope geochemical characteristics of non-hydrocarbons indicate that He, Ar and N2 in the gas reservoirs enriched in non-hydrocarbons were derived largely from the upper mantle. Non-hydrocarbons in gaseous hydrocarbon reservoirs consist mainly of crustal radiogenic He and40Ar and some mantle-derived He and Ar, as well as of13C-depleted carbon dioxide and nitrogen generated as a result of thermal decomposition of organic matter in strata. Carbon dioxide enriched in13C was derived largely from carbonate rocks and partially from the lower crust and upper mantle. Based on the relationship between geothermal heat flow (Q) and3He/4 He ratio in natural gases, the Q values for the area studied have been calculated. Similar Q values are reported from the upper mantle uplift area (77 mWm-2) in Huabei and the Tancheng-Lujiang Rift Zone (88 mWm-2). More than 60 percent of geothermal heat flow in the Sanshui Basin may have been derived from the upper mantle. The project is financially supported by the National Natural Science Foundation of China.  相似文献   

16.
Fugacities of H2, N2, O2, CH4, H2O, H2S, NH3, CO, and CO2 are calculated on the basis of the extrapolation of the caloric properties, and those of the compressibility of substances into the region of pressures up to 2 Mbar and of temperatures up to 4000K. Several equilibrium mineralogical reactions are calculated. The most probable sequence of decreasing the magnitudes of the equilibrium molar fractions (masses) of these gases in the lower mantle of the earth is predicted.  相似文献   

17.
Carbonic fluid inclusions were observed in quartz-bearing veins at the Proterozoic Bidjovagge AuCu deposit within the Kautokeino greenstone belt in Norway, where mineralization occurred in oxidation zones of graphitic schists. A primary fluid inclusion zonation was observed with C02-rich fluid inclusions in the structural footwall of the deposit, and CH4-rich inclusions within the ore zone in the oxidation zone. Microthermometry of the primary hydrocarbon inclusions revealed 2 groups; (1) a group which homogenized between −125°C and the critical temperature of CH4 (−82.1°C), which indicated the presence of pure CH4, and (2) a group which homogenized between the critical temperature of CH4 and −42°C, which indicated the presence CH4 and higher hydrocarbons (HHC). Raman microprobe analyses of the first group confirmed the presence of CH4. The second inclusion group were fluorescent, and Raman spectra clearly displayed CH4,C2H6, and rarer C3H8 peaks. A typical feature of the Raman spectra were elevated baselines at the hydrocarbon peaks. Carbon peaks were also usually detected in each inclusion by Raman analysis. Bulk gas chromatography analyses of samples containing the first group (CH4) indicated the presence of CH4 and low concentrations of C2H6 and C3H8. Gas chromatography analyses of samples containing the second group (CH4 and higher hydrocarbons) confirmed the presence of CH4, and higher hydrocarbons such as C2H6 and C3H8 and also butanes. Based on the spacial zonation of hydrocarbons and the estimated PT conditions of 300 to 375°C and 2 to 4 kbars, the authors suggest an abiotic origin for the hydrocarbons. It is suggested that the hydrothermal fluids oxidized the graphitic schist, precipitated Cu and Au and formed light gas hydrocarbons.  相似文献   

18.
长白山火山区是我国具有潜在喷发危险的活火山,在2002~2005年火山活动性增强出现了岩浆房扰动。利用卫星遥感技术具有观测范围大、观测时间长且连续的优势。因此,本文利用对流层污染探测仪（MOPITT）和大气红外探测仪（AIRS）高光谱遥感数据提取了2002~2005年长白山天池火山区CO总量、O3总量、水汽总量和地表温度异常信息,讨论了高光谱遥感气体地球化学异常信息与火山活动性之间的关系,并对2002~2005年长白山天池火山区火山活动性进行了研究。结果表明,高光谱遥感数据观测到的气体地球化学（CO、O3、水汽）异常与地震、形变监测结果以及地面流体（CO2、He、H2）观测结果相一致,表明MOPITT和AIRS高光谱遥感卫星观测到的气体异常变化较好地反映了2002~2005年大规模的深部岩浆局部扰动。在2002~2005年火山活动期间,CO总量、O3总量、水汽总量和地表温度均出现了显著异常且异常出现时段相应准偏差显著增大,反映了气体逸出量在时间上具有不均一性,可能与火山、地震活动过程中地应力的作用和变化有关。从气体异常持续的时间以及地面观测结果综合分析,2002~2005年岩浆房扰动并没有产生长时间的地幔物质流的上升和迁移。在火山活动性增强的时间段内,地表温度出现异常低值,这可能与太平洋板块俯冲过程中引起的断裂拉张增强有关。此外,火山活动过程中逸出的气体进入大气圈产生大气化学反应也会导致高光谱遥感所观测到的气体地球化学异常。研究结果为2002~2005年长白山火山活动性的研究提供了来自高光谱遥感数据的气体地球化学新证据,也对高光谱分辨率遥感数据在火山活动规律的研究以及火山监测中的应用具有一定意义。  相似文献   

19.
活动热流体与成藏、成矿动力学研究进展   总被引：12，自引：1，他引：12  
陈红汉  李思田 《地学前缘》1996,3(4):259-262
地壳乃至上地幔的流体活动以及与成岩／成矿和人类密切相关的环境关系正日益受到国内外地质学家的高度关注。文章侧重介绍沉积盆地中活动热流体与成岩／成矿动力学的研究进展，并结合南海莺—琼盆地的活动热流体与天然气成藏研究成果，认为盆地热流体的动力学特征不仅控制了烃类和稀有气体、稀有金属的成藏、成矿过程，而且对盆地的动力学演化具明显的影响。  相似文献   

20.
The two Alpine orogenic phases of the Eastern Alps, in the Cretaceous and in the Tertiary, were both accompanied by the formation of mineral deposits. However, subduction-related magmatic belts as well as the typical “Andean” ore deposits are missing. Therefore, the role of metamorphism in East Alpine metallogeny was tentatively explored for more than 60 y, although for a long time without tangible results. Microthermometric, geochemical and isotopic investigations of fluid inclusions from selected Alpine mineral deposits presented allow a preliminary confirmation of the involvement of metamorphic fluids in their origin. Deposits which were formed immediately after the first, Cretaceous orogeny, were produced at high pressures by fluids of very high salinity and high density, and with an isotopic composition of the water falling into the metamorphic field. These fluids are best understood as products of metamorphic de-volatilization of rocks of the subducted South Pennine domain. In contrast to this, the deposits formed after the second, Tertiary orogeny, originated at relatively low pressures from fluids with an appreciable content of CO2 and of low to moderate salinities. Isotopic compositions of this carbon indicate a deep crustal or even mantle source for CO2, while the water is isotopically more heterogeneous and may have mixed sources, both surficial and metamorphic. Tectonic control of these mineralizations is late-orogenic trans-tensional faulting, which exposed hot metamorphic rocks to fluid convection along brittle structures. These deposits conform best to the model of metamorphogenic metallogenesis by retrograde leaching, although ponded metamorphic fluids and mantle volatiles may also have been involved. Received: 4 August 1998 / Accepted: 5 January 1999  相似文献   

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