首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Samples of early Miocene Muara Wahau coal from three drill cores were investigated with respect to maceral composition. Huminite macerals are dominant in the coal, ranging from 73.3 to 88.0% (vol.) with an average value of 77.4% (vol.). Liptinite macerals account for lower amount, from 0.7 to 6.7 with an average value of 1.8% (vol.). Inertinite macerals vary from 4.3 to 34.0% (vol.), averaging at 15.3% (vol.). Some paleoenvironmental indices based on the maceral composition were determined. Groundwater index (GWI) and vegetation index (VI) were considered as indicators for hydrological regime and type of peat vegetation. Tissue preservation index (TPI) and gelification index (GI) were determined to indicate the degree of preservation and relative wetness of the peat forming conditions. The VI-GWI diagram suggest that the coal was developed from herbaceous plants in ombrotrophic type of peat. TPI-GI diagram shows that the preservation was low and the peat was relatively wet or limnic. However, ombrotrophic peat type have commonly been related to relatively drier or telmatic environments. It is therefore, interpreted that the limnic condition could occur in ombrotrophic peat type, as the water level was rising up during the development of a high moor peat.  相似文献   

2.
This paper attempts to characterize the coals of Satpura Gondwana basin using a large number of pillar coal samples drawn from the working coal mines of Pench, Kanhan, and Tawa (Pathakhera) Valley Coalfields of this basin. This westernmost Gondwana basin of Peninsular India is graben/half-graben type and occupies an area of 12 000 km2 with sedimentary fills (>5000 m) ranging in age from Permian to Cretaceous. The Barakar Formation (Permian) is exclusively coal-bearing with a total coal reserve of nearly 2000 Mt. The results show that the coals of this basin are equally rich in inertinite (22.8–58.7%, 24.5–62.0% mmf basis) and vitrinite (24.4–52.4%, 24.4–56.0% mmf basis). The concentration of liptinite ranges from 8.8% to 23.2% (9.0–26.0% mmf basis). The dominant microlithotypes of these coals are inertite and vitrite with comparatively low concentrations of vitrinertite and clarite. The vitrinite reflectance (Rom% values) suggests that the Pench Valley (0.30–0.58%) coals are subbituminous C to high volatile C bituminous in rank, while the Kanhan and Tawa Valley coals (0.52–0.92%) are subbituminous A to high volatile A bituminous in rank. The localized enhancement of rank in the latter two basins has been attributed to the extraneous heat flow from deep-seated igneous intrusions in the basin. The microlithotype composition of these coals is suggestive of their evolution in limno-telmatic zones, under fluvio-lacustrine control with the development of upper deltaic and lower deltaic conditions near the fresh water lacustrines. The floral input is characteristic of forest swamps with intermittent floods, leading to the development of reed moor and open moor facies, particularly in the Pench Valley basin. The Gelification Index (GI) and Tissue Preservation Index (TPI) are suggestive of terrestrial origin with high tree density. Further, moderately high GI and exceedingly high telovitrinite based TPI along with high ash content, particularly for the coals of Kanhan and Tawa Valley Coalfields, are indicative of the recurrence of drier conditions in the forested swamps. Furthermore, lateral variation in TPI values is indicative of increase in the rate of subsidence vis-à-vis depth of the basin from east to west (Pench to Tawa Valley Coalfield). The Ground Water Index (GWI) suggests that these coals have evolved in mires under ombotrophic to mesotrophic hydrological conditions. The Vegetation Index (VI) values are indicative of the dominance of herbaceous plants in the formation of Pench Valley coals and comparatively better forest input in the formation of Kanhan and Tawa Valley coals.  相似文献   

3.
The Tertiary basins of Gujarat have always been a potential target for their hydrocarbon resources. The lignite resources of the region have also been an important field of research. The present paper presents the results of the petrological study carried out on the lignites of the Saurashtra basin. For this purpose samples were collected from lower and upper lignite seams from the Surkha lignite mine of Bhavnagar, Saurashtra. These samples were subjected to detailed petrographic analysis (both maceral and microlithotype). The study reveals that these lignites are dominantly composed of huminite group macerals while liptinite and inertinite group macerals occur in subordinate amounts. These lignites have attained a thermal maturity up to 0.28-0.30 percent vitrinite reflectance (VRr) which classifies them as ‘low rank C’ coals. Moreover, Bhavnagar lower lignite seam shows relatively less gelification as compared to the upper seam which suffered relatively more biochemical degradation. These lignites are characterized by high gelification index (GI) and low tissue preservation index (TPI).With the help of petrography based facies models an attempt has been made to reconstruct the environment of the paleomire of these lignites.  相似文献   

4.
In the present study an attempt has been made to characterize the Gurha lignites employing petrographic and geochemical techniques on a large number of lignite samples. The data generated has been discussed to understand the hydrocarbon generation potential as well as the evolution of the paleomires of these lignites. The present investigation indicates that these lignites are mainly dominated by the huminite followed by inertinite and liptinites occurs in meager concentration. The huminite reflectance values rank the Gurha lignite as a low-rank B lignite.Petrographic result indicates these lignites are thermally immature in nature and comprised of Type-III kerogen and may generate only gas on maturation which is further supported by the rock-eval pyrolysis. The plots of rock eval data also indicates the same. The GI and TPI as well as GWI and VI values and the petrography-based facies critical models indicate that these lignites originated mostly under wet forest swamp condition. The microscopic constituents have also shown that these lignites are from herbaceous plants in wet forest swamp environment and ombrotrophic hydrological condition. The presences of framboidal pyrite in the study area infer the marine influence which also supported by the presence of high sulphur content.  相似文献   

5.
Organic petrology based petrographic indices (Tissue Preservation Index and Gelification Index) is a widely utilized tool in the study of depositional palaeoenvironment of coal. Evaluation of these petrographic indices suggests that, at present, utilize only vitrinite/huminite and inertinite macerals to interpret depositional environment of coal. Liptinite group macerals have important depositional environment implications, but liptinite macerals have not been taken into account in earlier petrographic indices (TPI and GI) formulations. This article examines the limitation of TPI and GI, and proposes improved TPI and GI indices, including the liptinite and inertinite macerals having depositional environment significance.  相似文献   

6.
The Cr and Ni contents are high in the Eocene lignite of the Shenbei coalfield, which is a small intracontinental basin located in Liaoning Province, China. In this paper, we studied the distribution, origin and occurrence of Cr, Ni and other hazardous trace elements in the Shenbei lignite on the basis of coal petrology, and geochemistry of the lignite and combustion products. The following conclusions on the Shenbei lignite can be drawn: (1) The dominant maceral group in the Shenbei coal is huminite (humodetrinite), accounting for 96%–99% of the total maceral. Inertinite content is less than 1%. Liptinite content (sporinite and cutinite) is 0.2–1.6%. Common minerals in the Shenbei lignite include clay minerals (kaolinite), pyrite and quartz, and calcite and siderite. Chromite is not present in the lignite. (2) Potentially hazardous trace elements such as Co (22 μg/g), Cr (79 μg/g), Cu (63 μg/g), Zn (93 μg/g), V (88 μg/g) and Ni (75 μg/g) are strongly enriched in the Shenbei lignite compared with average concentration of trace elements in the Chinese coal and worldwide lignite. These elements are mainly associated with fulvic acid (FA) and/or coal organic macromolecular compounds in most of the studied lignite samples, indicating an organic association and enrichment of these elements in the Shenbei lignite. (3) Unusually high trace elements contents in the Shenbei lignite are derived mainly from the olivine basalt (country rock of coal basin) that consists of 52.7% plagioclase, 17.8% pyroxene, 14% olivine and 15.5% Ti–Fe oxide minerals. These olivine basalts have higher Cr, Ni, Pb and Zn contents than other types of rock and worldwide basalts do. (4) Fly ash of the Shenbei lignite, with 90% 1–50 μm amorphous particles and 8% 1–10 μm cenosphere, has high contents of Zn (23,707 μg/g), Be (12 μg/g), Sr (1574 μg/g), Pb (486 μg/g) and Cr (349 μg/g). In particular, the ferruginous micro-cenoshperes contain 1–12.79% Zn. Fine bottom ash (<0.031mm) of the Shenbei lignite has higher contents for most of the elements with the exception of Mo, Sn and Zn. Therefore, the potentially environmental and health impact of the fly ash and fine bottom ash should constitute a major concern.  相似文献   

7.
采用反射光与透射光相结合的方法，通过研究区１４５个烃源岩样品的２１３块原岩和干酪根光片的显微观察及测定，建立了煤系烃源岩的显微组分分类方案。根据凝胶化指数（ＧＩ）和组织保存指数（ＴＰＩ），对上三叠统陆源有机质的原始形成环境进行了分析，并研究了上三叠统烃源岩的有机岩石学区域变化特征。研究表明，上三叠统陆源有机质的凝胶化指数高，而组织保存指数低，主要沉积在湖沼型滞水泥炭沼泽和草沼－低位泥炭沼泽环境中，形成了较多的富氢有机组分，为研究区油气的生成奠定了良好的物质基础  相似文献   

8.
我国华南的江西乐平、浙江长广和贵州水城地区以出产特种煤一树皮煤而闻名．其煤岩组分中含有特殊组分树皮体,该煤具有较高的挥发份、氢含量及焦油产率等化学特征,同时也具有良好的生烃潜力。相关的煤相研究可为该煤种树皮体的富集现象提供相应的成因信息。通过对各矿区煤层的煤岩学和矿物学的研究,发现主采煤层的显微组分均较富集树皮体,显微组分的形态特征及其组合关系反映主采煤层的形成环境为潮坪泥炭沼泽沉积环境。依据凝胶化指数（GI）、植物组织保存指数（TPI）、地下水流动指数（GWI）和植被指数（VI）力这4个煤相参数对其成因进行研究,根据各参数之间的关系图,确定了各矿区煤层成因信息的异同点．并对其所具有的不同地球化学特征进行了分析和解释。  相似文献   

9.
Samples from two lignite seams (Lower Seam, Upper Seam) of the Lavanttal basin (Austria) and additional xylite were investigated for variations in maceral composition, petrography-based facies indicators, bulk geochemical parameters, and molecular composition of hydrocarbons. Both seams originated in a topogenous mire and evolved within a transgressive setting. The final drowning of the mire is indicated by sapropelic shales. Whereas the sapropelic shale overlying the Lower Seam was deposited in a freshwater lake, the sapropelic shale above the Upper Seam represents a brackish lake.Numerous relationships are found between petrography-based facies indicators and the geochemical composition of organic matter. The contents of macerals of the liptinite group are positively correlated with soluble organic matter (SOM) yields and hydrogen index (HI). Consistent with maceral composition and high HI values, enhanced proportions of short-chain n-alkanes, which are predominantly found in algae and microorganisms, are obtained from samples of the sapropelic shales. The final drowning of the mire is reflected by decreasing pristane/phytane ratios, due to the rise in (ground)water table and the establishment of anaerobic conditions, as well as by decreasing ratios of diasterenes/sterenes, indicating increasing pH values in the mire. The degree of gelification of plant tissue (gelification index) is governed by the microbial activity in the mire, as indicated by the hopanes concentration. The differences in floral assemblage during the formation of the Lavanttal lignite seams are reflected by major differences in tissue preservation. Preservation of plant tissue (TPI) in the Lavanttal lignite is obviously controlled by the presence/absence of decay-resistant gymnosperms in the peat-forming vegetation, and additionally influenced by the relative contribution of wood to coal formation. The results provide evidence that valuable information for coal facies characterization could be obtained by petrography-based and geochemical facies indicators. An influence of the floral assemblage (gymnosperms/angiosperms ratio) and of the contribution of algal biomass on carbon isotopic composition of the organic matter (δ13C = − 24.2 to − 28.6‰) is proposed. Carbon cycling during biogeochemical decomposition of plant tissue by bacteria is suggested to affect the δ13C values of the coal. The chemotaxonomical classification of the xylites as gymnosperm remnants, based on the molecular composition of terpenoid biomarkers, is corroborated by the carbon isotopic composition of the xylites (mean δ13C = − 24.1‰) and the extracted cellulose (mean δ13C = − 20.2‰). The higher isotopic difference of about 3.9‰ between cellulose and total organic carbon of the xylites, compared to the difference between cellulose and wood found in modern trees, is explained by the smaller effect of decomposition on δ13C of cellulose.  相似文献   

10.
This work focuses on the relationship between the coal geology and coal quality of the Miocene Mugla basin, Southwestern Anatolia, Turkey. To this end, detailed petrographical, mineralogical and geochemical studies were performed on composite profile samples from the nine coal fields in the Mugla basin (Alatepe, Bagyaka, Bayir, Çakiralan, Ekizköy, Eskihisar, Hüsamlar, Sekköy and Tinaz coal fields). The Mugla lignite is a high ash (from 16 to 56%) and sulphur (from 2.1 to 5.7%) lignite which is petrographically characterised by a high huminite content, mainly gelinite macerals. The mineral matter of the studied lignite samples is made up mainly of clay minerals and quartz, with the exception of the Sekköy and Ekizköy lignites, in which calcite is the dominant mineral phase with minor amounts of quartz, clay minerals, pyrite and gypsum and traces of aragonite. Syngenetic opal is also frequently identified in these samples. The differentiation of these two types of lignite with specific mineralogical patterns is attributed to the contemporaneous development of peatlands with a high detrital input, dominated by the quartz and clay mineral setting, and peatlands with low detrital supply and a dominant carbonate-rich lacustrine environment. The higher water table of the latter allowed the precipitation of micritic carbonates and the development of lakes with abundant mollusc fauna. This differentiation is also evidenced by the geochemical data. Thus, the Sekköy, Ekizköy, Hüsamlar, Bayir and Alatepe lignites are characterised by relatively low Al and Fe contents (<1.4%) and high sulphur contents (4.2 to 5.7%). In addition Sekköy and Ekizköy show relatively high contents of Ca (6.3–7.1% compared to 1.6–3.8% in the other lignites). All the lignite samples studied are characterised by relatively high Mo and U contents when compared with the worldwide averages of trace elements in coal. Relatively high alkaline syngenetic conditions of the peat-forming environment of the Mugla coal are deduced from the following mineralogical, petrographical and geochemical evidence: (a) the precipitation of syngenetic opal (dissolution of quartz and re-precipitation as opal) and calcite; (b) minor and very early syngenetic sulphide precipitation (only framboidal and euhedral pyrite); (c) high bacterial activity, typical of high pH conditions, inferred from low preservation of tissue structures; (d) preservation of aragonite gastropod shells; and (e) the anomalous enrichment of U, Mo and W. A key result of the study of Mugla limnic coals (at least of the Sekköy and Ekizköy coal fields) is that a major influence was exerted on the early diagenetic evolution of the coal by the hydrochemistry of the lacustrine waters. This hydrochemistry was largely linked to the lithology of the surrounding source rock areas although the final evolutionary trend of the solute composition in the lake waters, characterized by very high carbonate and sulphate contents, was largely enhanced by the endorheic river drainage system and the arid–semiarid paleoclimatic situation under which organic matter accumulation took place.  相似文献   

11.
The petrography of lignitic, subbituminous and bituminous inertinitic coals (i.e. coals containing > 30 modal percent inertinite on a mineral-matter-free basis) derived from limnic and paralic facies in the Upper Silesian coal basin of Poland was investigated. Paralic coals were observed to contain small amounts of telinite and abundant pyrofusinite compared to limnic coals. The ratio of oxysemifusinite and oxyfusinite to pyrosemifusinite and pyrofusinite is lower in paralic coals as compared to limnic coals. The statistical analysis of the reflectances of the inertinite group macerals and of vitrinite shows that paralic coals are more heterogeneous than limnic coals. This greater degree of heterogeneity may explain the differences in reactivity among coals that otherwise have the same rank and elemental and petrographic composition.  相似文献   

12.
The Jinding Zn–Pb deposit occurs in Cretaceous and Paleocene siliciclastic rocks (mainly sandstones) in the Meso-Cenozoic Lanping basin, western Yunnan, China. With a reserve of approximately 200 Mt of ore containing 6.1% Zn and 1.3% Pb, Jinding is the largest sandstone-hosted Zn–Pb deposit in the world. Most previous studies assumed that the mineralizing fluids were derived from within the basin (including meteoric recharge), and the fluid flow was driven by topographic relief under a hydrostatic regime. In contrast, we propose that the mineralizing system was strongly overpressured based on observations of hydraulic fractures and fluid inclusion data. Numerical modeling results indicate that the overpressures could not have been produced by normal sediment compaction. Thrust faulting and input of mantle-derived fluids are likely responsible for the building-up of the high overpressures. The special hydrodynamic regime and potential contribution of mantle-derived fluids to the mineralizing system distinguish Jinding from other known sedimentary basin-related Pb–Zn deposits.  相似文献   

13.
This paper presents for the first time a petrological and geochemical study of coals from the Central Asturian Coal Basin (North Spain) of Carboniferous (Pennsylvanian), mainly of Moscovian, age. A paleoenvironmental approach was used, taking into account both petrographic and organic geochemical studies. Vitrinite reflectance (Rr) ranges from 0.5% to 2.5%, which indicates a high volatile bituminous to semianthracite and anthracite coal rank. The coal samples selected for paleoenvironmental reconstruction are located inside the oil–gas-prone phase, corresponding to the interval between the onset of oil generation and first gas generation and efficient expulsion of oil. This phase is represented by coals that have retained their hydrocarbon potential and also preserved biomarker information. Paleodepositional reconstruction based on maceral and petrographic indices points to a swamp environment with vitrinite-rich coal facies and variable mineral matter content. The gelification index (GI) and groundwater influence index (GWI) indicate strong gelification and wet conditions. The biomarkers exhibit a high pristane/phytane ratio, suggesting an increase in this ratio from diagenetic processes, and a high diterpanes ratio. This, in turn, would seem to indicate a high swamp water table and a humid climate. The maximum point of coal accumulation occurred during the regressive part of the Late Moscovian sequence and in the most humid climate described for this period of time in the well-known coal basins of Europe and North America.  相似文献   

14.
The Kuroko deposits of NE Honshu are a key type deposit for the study of volcanogenic massive sulfide deposits. However, these deposits have not been studied in detail since the early 1980's and knowledge of their mode of formation is now dated. In this study, we present the analysis of 12 samples of the Kuroko deposits, 12 samples of submarine hydrothermal minerals from the Sunrise deposit and 6 samples from Suiyo Seamount, both of which are located on the Izu-Ogasawara (Bonin) Arc, for 27 elements. For the Kuroko deposit, Cd>Sb>Ag>Pb>Hg>As>Zn>Cu are highly enriched, Au>Te>Bi>Ba>Mo are moderately enriched, In>Tl are somewhat enriched and Fe is not significantly enriched relative to the average continental crust. Within each of these deposits, a similar pattern of element associations is apparent: Zn–Pb with As, Sb, Cd, Ag, Hg, Tl and Au; Fe–Cu–Ba with As, Sb, Ag, Tl, Mo, Te and Au; Si–Ba with Ag and Au; CaSO4. The enrichment of the chalcophilic elements in these deposits is consistent with hydrothermal leaching of these elements from the host rocks which are dominantly rhyolite–dacite in the case of the Kuroko deposits, rhyolite in the case of the Sunrise deposit and dacite–rhyolite in the case of the Suiyo Seamount deposit. However, this pattern of element enrichment is also similar to that observed in fumarolic gas condensates from andesitic volcanoes. This suggests that there may be a significant magmatic contribution to the composition of the hydrothermal fluids responsible for the formation of the Kuroko deposits, although it is not yet possible to quantify the relative contributions of these two sources of elements.The compositional data show that Sunrise and Suiyo Seamount deposits are much closer compositionally to the Kuroko deposits from NE Honshu than are the submarine hydrothermal deposits from the JADE site in the Okinawa Trough which contain, on average, significantly higher concentrations of Pb, Zn, Sb, As and Ag than each of these deposits. In spite of the greater similarity in tectonic setting of the Hokuroku Basin in which the Kuroko deposits formed to the Okinawa Trough (intracontinental rifted back-arc basin) compared to Myojin Knoll and Suiyo Seamount (active arc volcanoes), it appears that submarine hydrothermal deposits from Myojin Knoll and Suiyo Seamount are closer analogues of the Kuroko deposit than are those from the Okinawa Trough. The present data are consistent with the magmatic hydrothermal model for the formation of Kuroko-type deposits as formulated by Urabe and Marumo [Urabe, T., Marumo, K., 1991. A new model for Kuroko-type deposits of Japan. Episodes 14, 246–251].  相似文献   

15.
The Neogene Beypazari basin is one of the important coal districts of Central Anatolia with approximately 600 million short tons lignite reserves. The coal-bearing Neogene sediments occurring in the Beypazari basin are divided into seven formations, in ascending order; Çoraklar, Hirka, Akpinar, Çayirhan, Bozbelen and Kirmir Formations with Sariyar Limestone and Teke volcanics.The Çoraklar Formation consists of cross-bedded sandstones, channel-fill conglomerates, mudstones, carbonaceous shales and volcanoclastic pebblestones, which are fluvial in origin. The lower lignite seam occurs in the lower part of the Çoraklar Formation.The upper lignite seam occurs in the uppermost part of the Çoraklar Formation and is overlain by the Hirka Formation with a sharp contact. The Hirka Formation consists mainly of alternating shale, mudstone, bituminous shale, claystone, tuffite and silicified limestone, and they all are apparently of lacustrine origin.The lignite deposite occur in the Çayirhan and Koyunaǧili parts of the Beypazari Neogene basin. The Çayirhan coal field consists of lower and upper lignite seams, but the Koyunaǧili field contains only an upper lignite seam.The lower lignite seam, which does not crop out at the surface, indicates a fluvial origin of the lignite deposits, based on the lateral discontinuity and the lower sulphur content of the lower lignite seam, and the sedimentologic and stratigraphic features of the associated sediments. But the uniform stratigraphic and sedimentologic features, high sulphur content and wide-spread distribution of the upper lignite seam indicate that the upper lignites were deposited probably in a mud-flat facies of playa-lake environment. The lower and upper lignites are completely different in relation to the depositional environment, the geometry and degree of rank in lateral directions.The lateral spreading and geometry of the lower lignite deposits were controlled by channel, floodplain and well-drained marshes of a fluvial system. On the basis of recent drillings and field investigations, the lower lignite deposit has been demonstrated to be a linear spreading parallel to the axis of the channel fills and throughcross beds in clastic sediments of fluvial facies. Therefore, the lower lignite deposits trend along a northeastern direction and is not expected to be as widely spread as the upper lignites.  相似文献   

16.
Tadkeshwar lignite deposits are one of the important Lower Tertiary lignite deposits of Cambay Basin, Gujarat. These lignites are rich in huminite macerals followed by liptinite and inertinite with moderate to high proportions of associated mineral matter. Under fluorescence mode these are found to be rich in liptinite macerals, in particular the liptodetrinite and resinite. The type of huminite suggests that the lignite is formed from mixed vegetal source, i.e. woody forest vegetation and herbs, shrubs. The composition of macerals indicates the deposition of lignite in sub-aqueous condition in wet-reducing environment with intermittent exposure and subsidence of the peat surface. The rank of the Main and the Leader seams, determined through reflectance measurement, indicate that the lignite is less mature. The considerable amount of perhydrous huminite may have contributed to the lower reflectance values in some of the samples. Low rank and appreciable amount of mineral matter make the lignite suitable for its utilization in thermal power plants, however when upgraded or mixed with better quality coals it can be used for other industries.  相似文献   

17.
临沧超大型锗矿床有机质与锗矿化的地球化学特征   总被引：10，自引：3，他引：10  
庄汉平  刘金钟 《地球化学》1997,26(4):44-52,T002
临沧锗矿床是一产于第三系含煤岩系中的超大型矿床。矿床的最初锗源与盆地西缘的二云母花岗岩有关。主矿体产于下煤组沉积旋回的早期地层中，每一沉积阶段早期形成的褐煤和碳质泥岩中富含锗，最高含量达１４７０×１０＾－６。褐煤和碳质泥岩在矿化过程中平均富集了１６４－１６９倍。根据锗含量，褐煤和碳质泥岩可分为锗含量小于１２×１０＾－６的低锗煤（泥岩）和大于９０×１０＾－６的高锗煤（泥岩）。高锗煤中有机质富含氧官能  相似文献   

18.
The Rio Maior Basin (Portugal) is a tectonic depression, filled by a Pliocene sequence that comprises, from floor to roof: (i) kaoliniferous fine sands, (ii) diatomites and lignites, (iii) recent deposits of sandstone and clay. The diatomites and lignites form a small dissimetric syncline with alternating seams. Ten lignite seams were identified and named from floor to roof as F, E, D, C.2, C.1, C, B, A, a and a′. Seams A, D, E and F are considered to be the main seams.The organic fraction consists mainly of macerals of the huminite group, with small percentages of inertinite and liptinite groups. However, the petrographic composition of each seam is distinct, particularly with regards to macerals of the huminite and liptinite groups.Calculation of petrographic indices permitted to plot the coals in facies and palaeoenvironment diagrams. Five facies have been defined: (i) aquatic, (ii) herbaceous swamp, (iii) mixed swamp with forest and herbaceous vegetation, (vi) forest swamp (wetter) and (v) forest swamp (drier).These lignites are humic coals formed from organic matter of terrestrial origin. The peat biomass at the origin of these coals formed from a very diverse vegetation comprising gymnosperms and angiosperms. In seams F, and occasionally in seams E and D, Botryococcus algae have also contributed to the biomass. Peat deposition corresponded to a rheotrophic hydrological regime: the water level always remained above the topographic surface of the basin. Nevertheless, during the deposition of seam A in the northern part of the basin, the water level was slightly below the topographic surface. The organic matter was preserved in anaeorobic conditions.  相似文献   

19.
Micro-FTIR spectroscopy of liptinite macerals in coal   总被引：3，自引：0，他引：3  
Reflectance FTIR microspectroscopy has been used to investigate the chemical structure of the liptinite macerals, alginite, bituminite, sporinite, cutinite and resinite in bituminous coals of Carboniferous to Tertiary age. In comparison with the spectra of vitrinite in the same coals, the micro-FTIR spectra of liptinite macerals are characterized by stronger aliphatic CHx absorptions at 3000–2800 and 1460–1450 cm−1, less intense aromatic C=C ring stretching vibration and aromatic CH out of plane deformation at 1610–1560 and 900–700 cm−1 respectively and various intense acid C=O group absorptions at 1740–1700 cm−1. The peaks at 1000–900 cm−1 due to aliphatic CH2 wagging vibrations in olefins and at 730–720 cm−1 due to CH2 rocking vibration in long chain aliphatic substances ([CH2]n, n≥4), are characteristic of liptinite macerals. Collectively the micro-FTIR spectral characteristics indicate that liptinite is composed of greater numbers of long chain aliphatics, fewer aromatics and a broader range of oxygen-containing groups than other macerals. Marked differences exist in micro-FTIR spectra within the liptinite maceral group. Alginite has the strongest aliphatic and least aromatic absorptions followed by bituminite, resinite, cutinite and sporinite. The aliphatic components in alginite are the longest chained and least branched whereas those in sporinite are the shortest chained and most branched. Bituminite, resinite and cutinite are intermediate. Notable differences in micro-FTIR spectra of individual liptinite macerals, such as intensities and peak locations of aromatic C=C in alginite, C=O groups in bituminite and resinite and substituted aromatic CH and C–O–C groups in cutinite and sporinite, also exist, which are attributed to differences in depositional environments or biotaxonomy.  相似文献   

20.
With a reserve of  200 Mt ore grading 6.08% Zn and 1.29% Pb (i.e., a metal reserve of  15 Mt) hosted in Cretaceous and Tertiary terrestrial rocks, the Jinding deposit is the largest Zn–Pb deposit in China, and also the youngest sediment-hosted super giant Zn–Pb deposit in the world. The deposit mainly occurs in the Jinding dome structure as tabular orebodies within breccia-bearing sandstones of the Palaeocene Yunlong Formation (autochthonous) and in the overlying sandstones of the Early Cretaceous Jingxing Formation (allochthonous). The deposit is not stratiform and no exhalative sedimentary rocks have been observed. The occurrence of the orebodies, presence of hangingwall alteration, and replacement and open-space filling textures all indicate an epigenetic origin. Formation of the Jinding Zn–Pb deposit is related to a period of major continental crust movement during the collision of the Indian and Eurasian Plates. The westward thrusts and dome structure were successively developed in the Palaeocene sedimentary rocks in the ore district, and Zn–Pb mineralisation appears to have taken place in the early stage of the doming processes.The study of fluid inclusions in sphalerite and associated gangue minerals (quartz, celestine, calcite and gypsum) shows that homogenisation temperatures ranged from 54 to 309 °C and cluster around 110 to 150 °C, with salinities of 1.6 to 18.0 wt.% NaCl equiv. Inert gas isotope studies from inclusions in ore- and gangue-minerals reveal 2.0 to 15.6% mantle He, 53% mantle Ne and a considerable amount of mantle Xe in the ore-forming fluids. The Pb-isotope composition of ores shows that the metal is mainly of mantle origin, mixed with a lesser amount of crustal lead. The widely variable and negative δ34S values of Jinding sulphides suggest that thermo-chemical or bacterial sulphate reduction produced reduced sulphur for deposition of the Zn–Pb sulphides. The mixing of a mantle-sourced fluid enriched in metals and CO2 with reduced sulphide-bearing saline formation water in a structural–lithologic trap may have been the key mechanism for the formation of the Jinding deposit.The Jinding deposit differs from known major types of sediment-hosted Zn–Pb deposits in the world, including sandstone-type (SST), Mississippi Valley type (MVT) and sedimentary-exhalative (SEDEX). Although the fine-grained ore texture and high Zn/Pb ratios are similar to those in SEDEX deposits, the Jinding deposit lacks any exhalative sedimentary rocks. Like MVT deposits, Jinding is characterised by simple mineralogy, epigenetic features and involvement of basinal brines in mineralisation, but its host rocks are mainly sandstones and breccia-bearing sandstones. The Jinding deposit is also different from SST deposits with its high Zn/Pb ratios, among other characteristics. Most importantly, the Jinding deposit was formed in an intracontinental terrestrial basin with an active tectonic history in relation to plate collision, and mantle-sourced fluids and metals played a major role in ore formation, which is not the case for SEDEX, MVT, and SST. We propose that Jinding represents a new type of sediment-hosted Zn–Pb deposit, named the ‘Jinding type’.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号