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1.
Fly ash samples were collected from a Portuguese power plant that burns low-sulphur coals from South Africa, U.S.A., Colombia, and Australia. The fly ashes were collected from the hoppers of the economizers, air heaters, electrostatic precipitators, and from the stack. The power plant air monitoring system was also sampled. The fly ash characterization was conducted by micro-Raman spectroscopy (MRS). The micro-Raman spectroscopic analysis permitted an efficient identification and characterization of different inorganic and organic materials present in fly ash: quartz, hematite, magnetite, calcite, glass, aluminium and calcium oxides, and different types of organic constituents.The study of the structural evolution of the unburned carbon/char material during their path through the power plant, though the use of Raman spectra and Raman parameters reveal that despite the high temperatures they reached, these materials are still structurally disordered. However, a structural evolution occurs in the char from the economizer up to the electrostatic precipitators where the char is structurally more disordered.The different features of the Raman spectra observed for carbon particles collected from the stack, together with the high range of variation of the Raman parameters, confirm the existence of different carbon particles in the stack, i.e., char and others (probably soot).The filters from the surroundings contain a variety of carbon particles with Raman parameters different from the ones obtained in the fly ash hoppers and stack. These are diesel particles as indicated by the values of WD1, FWHMD1, FWHMG, WG and ID1/IG obtained.  相似文献   

2.
This study deals with a detailed geochemical characterization of three crude oils from the Upper Indus Basin, Punjab, Pakistan. The samples were obtained from three productive oil fields of the Datta Formation (Jurassic), Lochhart (Palaeocene) and the Dhak Pass zone (Palaeocene). The GC parameters for and the bulk properties of Datta Formation oils are essentially coincident with those of the oils from the Dhak Pass Formation in the Upper Indus Basin, Pakistan and the oils likely originate from a marine source rock. In contrast, the Lockhart Formation oils show different behaviors and seem to be originated from dirty carbonate rocks although all three crude oils are mature, being of non-biodegraded and somewhat mixed organic matter origin. Low Pr/Ph values and high C35 homohopane index for the Lockhart Formation oils suggest a source of anoxic environment with low Eh while oils from the Datta Formation and Dhak Pass Formation showed different trends, i.e., lower values of C35 homohopane index indicating different depositional environment than oil from the Lockhart Formation. All three crude oils from the Upper Indus Basin are mature for the hopane ratios, i.e., Ts/Ts+Tm, C3222S/(S+R) and C30 αβ/(αβ+βα) and sterane ratios, i.e., C2922S/(S+R) and C29ββ/(ββ+αα) but oils from the Lockhart Formation seem to be less mature than those from the Palaeocene and Datta Formation according to plots like API° vs. homohopane Index, Pr/Ph vs. sterane. The relative composition of 5α(H), 14β(H), 17β(H)-24-ethylecholestanes and the C2920S/20S+20R index, indicate that all three crude oils are equally mature, which makes it unlikely with respect to the above said plots. This difference is may be due to the migratory chromatography which alters the concentrations of sterane and hoapnes and hence gives different results. These oils do not exhibit UCM and have complete n-alkane profiles indicating non-biodegradation.  相似文献   

3.
The lower part of Shayi Member (Es1x Sub-Member) composed mainly of dark mudstones and shales is the dominant source rocks for the Lixian Slope. Based on organic petrology, organic and inorganic geochemistry analyses of several mudstone and shale samples selected from Es1x Sub-Member, this research provides an overview on type, origin and thermal maturity of organic matters, as well as depositional environment of Es1x Sub-Member. Kerogen microscopy observation shows that the macerals are dominated by sapropelinite with a significant mixture of vitrinite and inertinite, indicating that aquatic algal-bacterial organic matter inputs are dominate with a significant contribution of terrigenous organic matter inputs. This statement is supported by n-alkane patterns distribution characteristics, high (n-C21 + n-C22)/(n-C28 + n-C29) values (average = 1.77), the plot of high Ph/n-C18 values (average = 4.15) versus low Pr/n-C17 values (average = 1.13), and high proportion of C27 sterane and C29 sterane (average = 37.7 and 42.0%, respectively). In addition, the rather low Pr/Ph values (average = 0.38), high gammacerane index values (average = 0.30), high V/Ni and V/(V + Ni) values (average = 11.84 and 0.89, respectively), high Sr/Ba and Sr/Cu values (average = 8.54 and 108, respectively), indicative of a saline water condition and a anoxic depositional environment. The low C29 sterane ααα 20S/(20S + 20R), C29 sterane αββ/(αββ + ααα), C31 homohopane 22S/(22S + 22R), C32 homohopane 22S/(22S + 22R), Ts/(Ts + Tm) values and relatively high moretane/hopane values show that the level of thermal maturity of organic matters in Es1x Sub-Member are low.  相似文献   

4.
Hydrocarbon distributions and stable isotope ratios of carbonates (δ13Ccar, δ18Ocar), kerogen (δ13Cker), extractable organic matter (δ13CEOM) and individual hydrocarbons of Liassic black shale samples from a prograde metamorphic sequence in the Swiss Alps were used to identify the major organic reactions with increasing metamorphic grade. The studied samples range from the diagenetic zone (<100°C) to amphibolite facies (∼550°C). The samples within the diagenetic zones (<100 and 150°C) are characterized by the dominance of C<20n-alkanes, suggesting an origin related with marine and/or bacterial inputs. The metamorphic samples (200 to 550°C) have distributions significantly dominated by C12 and C13n-alkanes, C14, C16 and C18n-alkylcyclopentanes and to a lesser extend C15, C17 and C21n-alkylcyclohexanes. The progressive 13C-enrichment (up to 3.9‰) with metamorphism of the C>17n-alkanes suggests the occurrence of cracking reactions of high molecular weight compounds. The isotopically heavier (up to 5.6‰) C<17n-alkanes in metamorphic samples are likely originated by thermal degradation of long-chain homologous with preferential release of isotopically light C1 and C2 radicals. The dominance of specific even C-number n-alkylcyclopentanes suggests an origin related to direct cyclization mechanism (without decarboxylation step) of algal or bacterial fatty acids occurring in reducing aqueous metamorphic fluid conditions. The regular increase of the concentrations of n-alkylcycloalkanes vs. C>13n-alkanes with metamorphism suggests progressive thermal release of kerogen-linked fatty acid precursors and degradation of n-alkanes. Changes of the steroid and terpenoid distributions are clearly related to increasing metamorphic temperatures. The absence of 18α(H)-22,29,30-trisnorneohopane (Ts), the occurrence of 17β(H)-trisnorhopane, 17β(H), 21α(H)-hopanes in the C29 to C31 range and 5α(H),14α(H),17α(H)-20R C27, C29 steranes in the low diagenetic samples (<100°C) are characteristic of immature bitumens. The higher thermal stress within the upper diagenetic zone (150°C) is marked by the presence of Ts, the disappearance of 17β(H)-trisnorhopane and thermodynamic equilibrium of the 22S/(22S + 22R) homohopane ratios. The increase of the ααα-sterane 20S/(20S + 20R) and 20R ββ/(ββ + αα) ratios (from 0.0 to 0.55 and from 0.0 to 0.40, respectively) in the upper diagenetic zone indicates the occurrence of isomerization reactions already at <150°C. However, the isomerization at C-20 (R → S) reaches thermodynamic equilibrium values already at the upper diagenesis (∼150°C) whereas the epimerisation at C-14 and C-17 (αα → ββ) arrives to constant values in the lower anchizone (∼200°C). The ratios Ts vs. 17α(H)-22,29,30-trisnorneohopane [(Ts/(Ts + Tm)] and 18α(H)-30-norneohopane (C29Ts) vs. 17α(H),21β(H)-30-norhopane [C29Ts/(C29Ts + C29)] increase until the medium anchizone (200 to 250°C) from 0.0 to 0.96 and from 0.0 to 0.44, respectively. An opposite trend towards lower values is observed in the higher metamorphic samples.The occurrence of specific hydrocarbons (e.g., n-alkylcyclopentanes, cadalene, hydrogenated aromatic compounds) in metamorphic samples points to kerogen degradation reactions most probably occurring in the presence of water and under reducing conditions. The changes of hydrocarbon distributions and carbon isotopic compositions of n-alkanes related to metamorphism suggest that the organic geochemistry may help to evaluate the lowest grades of prograde metamorphism.  相似文献   

5.
Surma Group is the most important geological unit of Bengal basin, Bangladesh, because petroleum resources occur within this group. It is mainly composed of alternation of shale and sandstone and the shale fraction has long been considered as source rocks and the sandstone fraction as reservoir. These source and reservoir rocks have been studied by different authors by different approach but none of them adopted organic geochemistry and organic petrology as a means of study of source rock and their possible depositional environment. A total of thirty shale core samples have been collected from eight different gas fields to fulfill the short coming. The collected samples have been subjected to Source Rock Analysis (SRA) and/or Rock-Eval (RE) followed by pyrolysis gas chromatography (PyGC), gas chromatography mass spectrometry (GCMS), elemental analysis (EA) and organic petrological study such as vitrinite reflectance measurement and maceral analysis. The analyzed organic matter extracted from the shales of Surma Group consists mainly of Type III along with some Type II kerogen. The studied shales are mostly organically lean (TOC ±1%) and the extracted organic matter is fair to moderate. Based on these results, the analyzed shales have been ranked as poor (mostly) to fair quality source rock. The organic matter of the analyzed shale samples is thermally immature to early mature for hydrocarbon generation considering their Tmax and measured mean vitrinite reflectance values. The hopane 22S/(22S + 22R), moretane/hopane ratio and sterane parameters are also in good agreement with these thermal maturity assessments. The predominance of odd carbons over even carbons (most common) and/or even carbons over odd carbon numbered n-alkanes, moderate Pr/Ph ratio, low to high Tm/Ts ratio, comparative abundance of sterane C29 (i.e., C29 >C27>C28), Pr/nC17 — Ph/nC18 values, C/S ratio and dominance of vitrinite macerals group with the presence of liptinite macerals demonstrate that the organic matter has derived mainly from terrestrial inputs with an insignificant contribution from the marine sources. The condition of deposition alternates from oxic to anoxic.  相似文献   

6.
The upper part of Madbi Formation organic-rich shale is considered an important regional source rock in the Masila Basin, Yemen. Ten cutting samples from this Upper Jurassic organic-rich shale were collected from wells drilled in the Kharir Oilfield, Masila Basin in order to geochemically assess the type of organic matter, thermal maturity and depositional environment conditions. Results reveal that Upper Jurassic organic-rich shale samples contain high organic matter more than 2.0 wt.% TOC and have very good to excellent hydrocarbon potential. Marine algae organic matter is the main source input for the Upper Jurassic shale sequence studied. This has been identified from organic petrographic characteristics and from the n-alkane distributions, which dominated by n-C14-n-C20 alkanes. This is supported by the high value of the biomarker sterane/hopane ratio that approaches unity, as well as the relatively high C27 sterane concentrations. A mainly suboxic depositional environment is inferred from pr/ph ratios (1.75–2.38). This is further supported by relatively high homohopane value, which is dominated by low carbon numbers and decrease towards the C35 homohopane. The concentrations of C35 homohopane are very low. The depositional environment conditions are confirmed by some petrographic characteristics (e.g. palynofacies). Detailed palynofacies analysis of Madbi shales shows that the Madbi shale formation is characterised by a mix of amorphous organic matter, dinoflagellates cysts and phytoclasts, representing a suboxic, open marine setting. The Upper Jurassic marine shale sequence in the Masila Basin is thermally mature for hydrocarbon generation as indicated by biomarker thermal maturity parameters. The 22 S/22 S + 22R C32 homohopane has reached equilibrium, with values range from 0.58 to 0.62 which suggest that the Upper Jurassic shales are thermally mature and that the oil window has been reached. 20 S/(20 S + 20R) and ββ/(ββ + αα) C29 sterane ratios suggest a similar interpretation, as do the moretane/hopane ratio. This is supported by vitrinite reflectance data ranging from 0.74% to 0.90%Ro and thermal alteration of pollen and spore. The thermal alteration index value is around 2.6–3.0, corresponding to a palaeotemperature range of 60–120°C. These are the optimum oil-generating strata. On the basis of this study, the Madbi source rock was deposited under suboxic conditions in an open marine environment and this source rock is still within the oil window maturity range.  相似文献   

7.
The Masila Basin is an important hydrocarbon province in Yemen, but the origin of hydrocarbons and their generation history are not fully understood. In this regard, 10 crude oils from different petroleum reservoir sections in the Masila Basin were characterized by a variety of biomarker and non-biomarker parameters using GC, GC-MS and stable carbon isotope techniques. Oils from the Masila Basin display pristane/phytane (Pr/Ph) ratios ranging from 1.7 to 2.0, low sulfur content, high C35 homohopane index, relatively high C27 sterane concentrations and relatively high tricyclic terpanes suggesting a marine clay source rock that was deposited in mildly anoxic to suboxic conditions with dominantly algal organic matter. C29 20S/(20S + 20R) steranes and ββ/(ββ + αα) sterane ratios indicate that the Masila oils have reached peak oil window maturity. Another related feature of these oils is the absence of 18α (H)-oleanane, which suggests a source age older than Cretaceous. The carbon isotope compositions are similar to those of the potential source rocks, which range from −25.4‰ to −28.3‰, indicating a marine environment. The new data presented in this paper suggest that the Masila oils constitute one oil family and that the oil originated from the Upper Jurassic Madbi source rock in the basin.  相似文献   

8.
This new study was carried out in order to accurately characterize the geochemical pattern of Ousselat organic-rich facies from the Ypresian basin in central-northern Tunisia. It has been found that the organic matter is located towards the end of diagenesis/beginning of catagenesis. This assumption is supported by the relative low T max values (429–439°C) and by steranes maturity parameters such as C29 αα 20S/(20S + 20R), and C29 ββ/(ββ + αα). High HI values and the abundance of saturates (1–83%) compared to aromatics (2–27%) are unequivocal evidence of type-II organic matter as indicated by a high abundance of cholestane and the predominance of short-chain n-alkanes centred at n-C18 and at n-C20. Total organic carbon (TOC) content and petroleum potential values suggest that the Ypresian period corresponds to an anoxic event which led to the accumulation and preservation of large quantities of organic matter with high primary production. Due to their geochemical characteristics, the Lower Eocene facies represent a new potential source rocks in central-northern Tunisia.  相似文献   

9.
In this study, organic matter content, type and maturity as well as some petrographic and physical characteristics of the Jurassic coals exposed in the eastern Taurus were investigated and their depositional environments were interpreted.The total organic carbon (TOC) contents of coals in the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc areas are 24.54, 66.78 and 49.15%, respectively. The Feke–Akkaya and Kozan–Kizilinc coals have low Hydrogen Index (HI) values while the Kozan–Gedikli coals show moderate HI values. All coal samples display very low Oxygen Index (OI) values. The Kozan–Gedikli coals contain Type II organic matter (OM), the Feke–Akkaya coals contain a mixture of type II and type III OM; and the Kozan–Kizilinc coals are composed of Type III OM. Sterane distribution was calculated as C27 > C29 > C28 from the m/z 217 mass chromatogram for all coal samples.Tmax values for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 439, 412 and 427 °C. Vitrinite reflectance values (%Ro) for the Feke–Akkaya and Kozan–Kizilinc coal samples were measured as 0.65 and 0.51 and these values reveal that the Feke–Akkaya and Kozan–Kizilinc coals are at subbituminous A or high volatile C bituminous coal stage. On the basis of biomarker maturity parameters, these coals have a low maturity.The pristane/phytane (Pr/Ph) ratios for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 1.53, 1.13 and 1.25, respectively. In addition, all coals show a homohopane distribution which is dominated by low carbon numbers, and C35 homohopane index is very low for all coal samples. All these features may indicate that these coals were deposited in a suboxic environment.The high sterane/hopane ratios with high concentrations of steranes, low Pr/Ph ratios and C25/C26 tricyclic ratios > 1 may indicate that these coals formed in a swamp environment were temporarily influenced by marine conditions.  相似文献   

10.

The paper highlights the importance of using site-specific shear modulus reduction (G/Gmax versus shear strain, γ) curves and damping ratio (D versus shear strain, γ) curves for ground response analysis. In order to develop comprehensive G/Gmax–γ and D–γ curves (i.e. over a wide range of strain level), two types of apparatus, viz. resonant column and cyclic simple shear, have been used. The case study considered the geological deposits from the river beds of Yamuna River originating from the Himalayan seismic zone of North India. The tests results have been analysed to develop G/Gmax–γ and D–γ curves and compared with standard curves. It has been observed that upper and lower boundaries for the standard curves are remarkably different for the geological deposit under consideration. In order to assess the impact of using standard curves rather than site-specific curves, ground response analysis has been carried out at five sites along the Yamuna River using two types of curves (standard and site-specific developed in this study). The study showed that the amplification of shear waves at these sites based on the experimentally derived curves is much higher as compared to the standard curves. The proposed curves better represent dynamic behaviour of the soil deposits of the region and will provide a realistic response as far as practically possible, for the structures constructed in the states of Haryana and Delhi and nearby areas. It is anticipated that the data presented in this paper will have wide application and usage.

  相似文献   

11.
The hematite mineralization under investigation is located 11 km NE of Sarical (Yavu) village of the Yildizeli town (Sivas Province) in central Turkey. The region is within the Central Anatolian Thrust Zone and is comprised of metamorphic units, ophiolitic rocks and overlying Tertiary volcanic and volcanosedimentary rocks in addition to Neogene terrestrial deposits. The mineralization occurs as lenticular or bedded bodies and is composed chiefly of hematite and a lesser amount of goethite. Quartz, calcite, and dolomite are the gangue minerals. Kaolinite and zeolite are the common alteration products. In this study, geochemical and mineralogical investigations were carried out using an X-ray diffractometer analysis (XRD), Raman spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX). The V/(V + Ni) ratio increases in parallel to the detritic contribution, and when this ratio is less than 0.60, deposition conditions are said to be anoxic. Considering the V/(V + Ni) ratio and Ceanom values of the studied samples, we suggest that the environment is both oxic and anoxic in character. The overall assessment of the field observations, mineral paragenesis, major, trace, and rare earth element (REE) data indicates that the Sarical hematite mineralization is of a hydrothermal-sedimentary type.  相似文献   

12.
The aliphatic hydrocarbon composition (acyclic isoprenoids, hopanoids and steroids) of oils from the most productive fields in the southern geological Province of Cuba have been studied. This province is defined by its position with respect to the Cretaceous overthrust belt generated during the formation of oceanic crust along the axis of the proto-Caribbean Basin. The relative abundances of 18α(H)-22,29,30-trisnorneohopane, gammacerane and diasteranes suggest that Pina oils are related to the carbonate oils from the Placetas Unit in the northern province (low Ts/(Ts+Tm) and C27,29 rr/(rr+sd) ratios). The Cristales and Jatibonico oils exhibit some differentiating features such as higher Ts/(Ts+Tm) and absence of gammacerane. The oils from this province do not exhibit significant differences in either hopane, C32 22S/(S+R) and C30 αβ/(αβ+βα), or sterane, C29 αα 20S/(S+R), maturity ratios. However, the relative content of 5α(H),14β(H),17β(H)-cholestanes (C29 ββ/(ββ+αα) ratio) indicates that Pina oils are more mature than Cristales and Jatibonico oils. Several of these oils (Cristales, Jatibonico and Pina 26) are heavily biodegraded, lacking n-alkanes, norpristane, pristane and phytane (the two former oils do not contain acyclic isoprenoid hydrocarbons). Other biodegradation products, the 25-norhopanes, are found in all the oils. Their occurrence is probably due to mixing of severely biodegraded oil residues with undegraded crude oils during accumulation in the reservoir.  相似文献   

13.
In this paper, an attempt has been made to highlight the influence of different parameters such as number of cycles, confining pressure, void ratio, gradation, initial anisotropy and stress path on the dynamic properties of granular materials using Discrete Element Method (DEM). A series of strain controlled cyclic triaxial numerical simulations using three dimensional DEM have been carried out on an assembly of spheres. Dynamic properties such shear modulus (G) and damping ratio (D) were determined from the typical hysteresis loop obtained during cyclic triaxial test simulation. It has been observed from the test results that the numerical simulation using DEM has captured the variation of dynamic properties over a wide range of shear strain values for different parameters considered for the current investigation. Maximum shear modulus (G max) was found to be influenced by initial confining pressure, void ratio, gradation and initial anisotropy. Whereas, the damping ratio (D) was found to be influenced by number of cycles, initial confining pressure, gradation and stress path. Further it has been shown that the variation of shear modulus with shear strain can be divided into three distinct zones such as Isotropic Zone (IZ), Anisotropic Zone (AZ) and Stable Anisotropic Zone (SAZ). A drastic reduction of shear modulus with shear strain has been observed in the Anisotropic Zone (AZ). In addition, the results obtained using numerical simulations have been compared with the laboratory experimental values.  相似文献   

14.
The right-rectangular parallelepiped resonance (RPR) form of resonant ultrasound spectroscopy (RUS) is applied to monoclinic crystal symmetry to determine the 13 adiabatic elastic constants, Cij, of single-crystal chrome-diopside Di0.93Hd0.03Ur0.02X0.02 (Di, diopside; Hd, hedenbergite; Ur, ureyite; X, other or unknown). These data represent the first published values of the elastic tensor for a monoclinic single-crystal determined by the RPR method, thus demonstrating the feasibility of this method for studying elasticity of low-symmetry crystals. The lowest 62 modal frequencies of a gem-quality specimen were measured and identified at ambient temperature and pressure. Inverting the modal frequencies results in, respectively C11, C22, C33, C44, C55, C66, C12, C13, C23, C15, C25, C35, C46 values (GPa) of 228.1(1.0), 181.1(0.6), 245.4(1.3), 78.9(0.3), 68.2(0.2), 78.1(0.2), 78.8(0.5), 70.2(0.7), 61.1(0.7), 7.9(0.5), 5.9(0.5), 39.7(0.4), and 6.4(0.2), where numbers in parentheses indicate experimental uncertainty. The corresponding isotropic bulk, KS, and shear, G, moduli are 116.5 (0.9) and 72.8(0.4) GPa, respectively. When comparing these results with other pyroxene data, we find systematic correlations between M2 site composition and Cij values for most, but not all, moduli. Unusual compositional dependence near end-member diopside is seen for a few moduli, and is propagated to the KS and G moduli, which should prompt a reexamination of some Cij values of end-member diopside.  相似文献   

15.
A suite of 27 oils from the Qinjiatun–Qikeshu oilfields in the Lishu Fault Depression of the Songliao Basin was analyzed using whole oil gas chromatography. In combination with the relative distribution of C27, C28, and C29 regular steranes, detailed geochemical analyses of light hydrocarbons in oil samples revealed crude oils characterized by the dual input of lower aquatic organisms and higher terrestrial plants. Several light hydrocarbon indicators suggest that the liquid hydrocarbons have maturities equivalent to vitrinite reflectances of around 0.78%–0.93%. This is consistent with the maturity determination of steranes C29 20S/(20S + 20R) and C29 ααβ/(ααα + αββ). Crude oils derived from the two distinct oilfields likely both have source rocks deposited in a lacustrine environment based on light hydrocarbon parameters and on higher molecular weight hydrocarbon parameters. The results show that light hydrocarbon data in crude oils can provide important information for understanding the geochemical characteristics of the Qinjiatun–Qikeshu oils during geologic evolution.  相似文献   

16.
The relationship between pyritic sulfur content (Spyr) and organic carbon content (Corg) of shales analyzed from the New Albany Group depends upon Corg. For samples of <6 wt.% Corg, Spyt, and Corg are strongly correlated (r = 0.85). For Corg-“rich” shales (>6 wt.%), no Spty-Corg, correlation is apparent. The degree of Fe pyritization (DOP) shows similar relationships to Corg. These C-S-Fe relationships suggest that pyrite formation was limited by the availability of metabolizable organic carbon in samples where Corg < 6 wt.% and by the availability of reactive Fe for samples where Corg > 6 wt.%. Apparent sulfur isotope fractionations relative to contemporaneous seawater sulfate (Δ34S) for pyrite formation average −40% for non-calcareous shales and −25%. for calcareous shales. Δ34S values become smaller with increasing Corg, Spyt, and DOP for all Corg-“poar” (<6 wt%) and some Corg-“nch” (<6 wt.%) shales. These trends suggest that pyrite formation occurred in a closed system or that instantaneous bacterial fractionation for sulfate reduction decreased in magnitude with increasing organic carbon content. The isotopic trends observed in the New Albany Group are not necessarily representative of other shales having a comparable range of organic carbon content, e.g. Cretaceous shales and mudstones from the western interior of North America (GAUTIER, 1986). Δ34S values in the remainder of the Corg-rich New Albany Group shales are relatively large (−38 to −47%.) and independent of Corg, Spyr, and DOP, which suggests that pyrite in these shales formed mostly at or above the sediment-water interface by precipitation from an isotopically uniform reservoir of dissolved H2S.  相似文献   

17.
The black shale samples collected from two Neogene formations in the Klias Peninsula area, West Sabah, have been assessed and characterized in details by gas chromatography, gas chromatography-mass spectrometry and a variety of organic geochemical parameters. The aims of this study are to describe the characteristics of organic matter of these sediments in terms of source/type of the organic matter, assess its thermal maturity and paleoenvironment of deposition, based primarily on biomarker distributions. The results of both formations do not reveal significant differences within the rock extracts. The gas chromatograms of the saturated hydrocarbon fractions of the Setap Shale and the Belait formations displayed monomodal n-alkane distributions and nearly identical regular sterane compositions with a predominance of C27 regular steranes. These are consistent with open marine depositional environments dominated by marine biological matter. Another related feature of these rock extracts is the presence of a high relative abundance of gammacerane, indicating anoxic marine hypersaline source depositional environment. The relatively high abundance of common land plant-derived biomarkers, such as bicadinanes and oleananes, is a clear indication of a major terrigenous input to the source of the extractable organic matter. The predominance of oleanane biomarkers in both formations is indicative of angiospermis input and Tertiary source rocks. The high C29/C30 hopane ratios, moderate development of C33–C35 hopanes, high abundance of tricyclic terpanes and a slight predominance of C27 regular sterane over C28 and C29 steranes are characteristic features tending to suggest a significant marine influence on these source rocks, thereby suggesting a mixed source input. The 22S/(22S+22R)C32 hopane ratio has reached equilibrium, and this is supported by the high maturity level as indicated by the 22S/22SC31–33 extended hopane ratios and 20S/(20S+20R)C29 regular steranes ratios.  相似文献   

18.
The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ~(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ~(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4~(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4~(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ~(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4~(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba~(2+) concentrations,CO_2 in the fluids,low HS~- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids.  相似文献   

19.
Goethite, hematite and intermediate products of goetite thermal decomposition were studied by IR and Raman spectroscopy to identify these products used as catalysts of some chemical reactions. The presence of a small number of OH-groups in the products of the decomposition up to 900–1000° C was supposed to hinder the formation of perfect hematite structure. The hypothesis concerning C 3v 6 space group of protohematite indistinguishable from D 3d 6 space group of hematite by X-Ray diffraction was suggested. This hypothesis explains both the additional lines in IR and Raman spectra compared to hematite spectra and the same position of peaks in X-Ray diffraction picture.  相似文献   

20.
The single crystal elastic constants of nonmetamict zircons have been measured as a function of pressure to 12 kb at room temperature and also as a function of temperature between 25 and 300° C at atmospheric pressure. The pressure derivatives of the elastic constants are: C 11=10.78, C 33=5.88, C 44=0.99, C 66=?0.31, C 12=3.24, C 13=6.20. The anomalous negative behaviour of C 66 versus pressure could be associated with a high pressure phase transition. The pressure and temperature derivatives of the isotropic elastic wave velocities and elastic moduli for nonmetamict zircon are calculated from the present single crystal data by the Voigt, Ruess, and Hill approximations and compared with the values of some other oxides and silicates. The pressure derivative of the isotropic adiabatic bulk modulus is relatively high (dK S/dP=6.50), and the pressure derivative of the shear modulus is relatively low, (dG/dP=0.78), compared to the corresponding values for some other oxides and silicates. The Debye temperature, ?D, and the high temperature limit of the Grüneisen parameter, γHt, calculated from the elastic constants and their pressure derivatives, agrees well with the Debye temperature and the thermal Grüneisen parameter, γth, calculated from the thermal expansion, heat capacity, and compressibility data.  相似文献   

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