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1.
Based on electron microscopic studies of minerals from iron-ore formations, a conclusion on different geneses of the composing rocks is made. Quartz of ferruginous quartzites originated through metasomatic transformation of primary biogenic limestones, while iron minerals were formed due to cyclic iron supply from deep-seated sources. Schists’ interlayers correspond to breaks in carbonate precipitation in periods of supply of terrigenous material from land or pyroclastics from volcanoes. 相似文献
2.
The article is dedicated to regularities in the distribution of sedimentary phosphorite and manganese deposits in the Lower Paleozoic and Proterozoic formations. Special attention is paid to co-occurrence of phosphate and manganese ores formed during the Vendian-Cambrian shale formation epoch. It is shown that shale formation in certain epochs of the Precambrian and Phanerozoic was determined by the excess influx of carbon and biogenic elements to seas and marginal parts of the oceans and by enhanced productivity of planktonic organisms in corresponding geological periods. 相似文献
3.
气源运聚通道与天然气水合物富集成藏关系密切。利用准三维地震资料并结合钻探成果,深入研究了神狐海域GMGS3钻探区高饱和度水合物站位气源运移疏导通道地质地球物理特征及其控藏作用。结果表明:高饱和度水合物产出站位发育多种类型运移疏导通道,且与BSR空间耦合关系较好;紧邻BSR之下为强振幅反射,强振幅下部游离气体充注现象明显,表明水合物稳定域下部存在气体运移的通道,且深部气体向浅层发生了运移。深大断裂、底辟及气烟囱构成了沟通深部热解气及浅层生物气与浅层温压稳定域的垂向通道,在这些通道上方可以直接形成水合物;浅部滑塌面、水道砂及海底扇构成的高孔渗连续性砂体为浅层生物气及深部运移而来的部分热成因气横向运移通道,气体的侧向运移扩大了气体供给范围,增加了矿体横向展布规模。文章认为,天然气运移疏导系统与其他成藏要素匹配良好的构造和区域是勘探高饱和度水合物的有利目标。 相似文献
4.
Reservoirs公司 《海相油气地质》2005,10(1):49-60
介绍了挪威埃科菲斯克油田的基本概况及油田勘探历史,描述了该盆地的演化、油气系统、区域地层及沉积相。该油田的构造类型为盐丘构造,主要的储集层为麦斯特里希特统(K2)—下古新统(丹麦阶)托尔组和埃科菲斯克组。埃科菲斯克组以构造裂隙为主,托尔组主要发育与缝合线有关的裂隙。白垩地层主要为生物成因,其成分为分解的贝壳或浮游的Cocccophorid藻颗石、浮游类和海底有孔虫类。 相似文献
5.
Igneous, metamorphic and biogenic apatite contains Lu and Hf in proportions that make this mineral suitable for dating by the 176Lu–176Hf method. We present a new method for separation of Lu and Hf from apatite that involves a single extraction column step for Hf and a second exchange column step for Lu. This procedure allows rapid sample processing prior to analysis by MC-ICP-MS. Results from the igneous Gardiner, Skaergaard and Khibina Intrusions indicate that the closure temperature for the Lu–Hf isotopic system in apatite is relatively high. The Lu–Hf isochron age of 60 Ma for the Skaergaard Intrusion, East Greenland, is older than the generally accepted emplacement age, but does not appear to be a product of mixing. A centimeter-sized apatite from the Otter Lake area, Grenvillian Province, yields high and variable 176Lu/177Hf ratios showing that metamorphic apatite may, in some cases, allow for mono-mineral dating. The most important application of the method is undoubtedly its potential use for dating sedimentary formations. Although we find biogenic apatite in porous matrix highly susceptible to post-depositional resetting of the Lu–Hf isotopic system, the preservation of a near-depositional age for a shark tooth from the impermeable London Clay and recent work on crystalline authigenic phosphorites [Earth Planet. Sci. Lett. 201 (2002) 203] show the Lu–Hf system to be a promising tool for direct dating of sedimentary formations. 相似文献
6.
Palynomorphs recovered from core and cuttings samples from five boreholes in the East Baghdad Oilfield indicate a mid Albian–early Cenomanian age-range for the Nahr Umr Formation and the lower part of the overlying Mauddud Formation. Two palynomorph zones and four types of palynofacies have been identified. The latter are interpreted to indicate delta-top swamp and marsh, silty–muddy deltaic, inner silty and carbonate-rich platform, and limestone-platform environments. The palynofacies of the two types of platform accumulations suggest that these are potential sources of biogenic methane and condensates, and may yield more liquid hydrocarbons in areas where the formations are at greater depths than within the region studied. 相似文献
7.
In order to assess the importance of siliceous sediments as a sink for oceanic B and to determine the effect of diagenesis on the mobilization of B, samples were analysed from chert nodules, bedded cherts, and siliceous banded iron formations from a variety of sedimentary environments and geologic ages. Boron analyses on bulk samples were made by prompt gamma neutron activation analysis. The distribution of B in rocks was mapped using α-track methods.Nodular Phanerozoic cherts typically contain 50–150 ppm B, and bedded cherts somewhat less. The B is initially concentrated in tests of silica-secreting organisms, but some is lost in early diagenesis as silica progressively recrystallises to quartz.Banded iron formation silica of Archean and Proterozoic age usually contains < 2 ppm B. This conforms with the view that such silica is not of biogenic origin but, since many iron formations are undoubtedly of marine origin, raises the question whether Precambrian oceans were impoverished in B. Analyses of Precambrian marine argillaceous sediments, averaging 70 ppm B, do not resolve this question. 相似文献
8.
The current state of the problem of oil genesis is discussed. The biogenic (sedimentary-migration theory) of oil genesis is shown to be valid based on the analysis of present-day data on the composition and properties of oil, the composition and distribution of organic matter (OM) in sedimentary rocks, and numerous calculations of the balance of oil-and-gas generation at different stages of catagenetic evolution. The confinement of oil and gas fields to sedimentary basins, as well as the relation of oil and/or gas reserves to volumes of oil-and-gas source rocks, which occur (or occurred) in the generation center, and/or to extremely high potential of oil source formations also indicate of the relationship between oil-and-gas fields and the “life” of former geological epochs. 相似文献
9.
Achievements in the study of modern carbonate sediments and ancient sedimentary carbonate rocks, as well as recent data pose new problems and generate a need for the revision of some seemingly unambiguous concepts. The prevalent role of biogenic and, first of all, microbial sedimentation of carbonate (including dolomitic) material and specific nontraditional settings of carbonate accumulation (intermediate and even high latitudes, deep-water basins) becomes more and more evident. The study of the internal structure of carbonate formations and its relationship with specific features of carbonate material deposition, climate, basin depth, and other factors represent a new important problem. The existing concepts of carbonate accumulation evolution need to be revised both from the standpoint of its factual reflection in sedimentary sequences and explanation. 相似文献
10.
The Cone-in-Cone Structure and Its Origin 总被引：1，自引：0，他引：1
Morphostructural investigation of carbonate cone-in-cone formations allows to conclude that they belong to self-organizing (dissipative, according to I. Prigogine's terminology) systems of the geological past formed in a thermogradient field at the expense of energy of heat and mass transfer (Prigogine and Stengers, 1984). First, the fluid-convective metasomatic hypothesis unites and reconciles the most well-known hypotheses that previously seemed to be incompatible and transforms them to rather consistent particular cases of a more intricate multistage geological phenomenon. Second, it helps to identify the morphologically and genetically analogous noncarbonate structures that mimic biogenic ones. The probable indicative role of cone-in-cone structure in the mapping of fluid-conducting systems is a consequence of the proposed hypothesis. 相似文献
11.
A. V. Dubinin V. N. Sval’nov E. D. Berezhnaya M. N. Rimskaya-Korsakova T. P. Demidova 《Lithology and Mineral Resources》2013,48(3):175-197
Indicator role of trace elements in sedimentation and ore formation is considered for sediments from Station 2182 in the Angola Basin. It is shown that pelagic sediments were formed from two main sources: biogenic calcium carbonate and lithogenic sediment component compositionally similar to the miopelagic clay. Increase of the Mn/Al ratio, Ce anomaly in the REE composition, Co/Ni and Mo/W ratios, and anomalous accumulation of Tl, Pb, Bi and other microelements indicate that sediments from horizons 15–20 and 30–35 cm contain significant amounts of hydrogenic material as Fe-Mn oxyhydroxides. Manganese micronodules (MN) were extracted from different horizons (10–15, 15–20, and 30–35 cm) and analyzed to study the hydrogenic component. Their development is related to retardation of biogenic and lithogenic sedimentation. The studied manganese micronodules are represented by the hydrogenic-diagenetic formations >100 μm in size with Mn/Fe = 2.0–2.8, Co/Ni = 0.2–0.4, Ce an = 4.2–5.7, and Mo/W = 5.2–7.9. The MN content is too low to affect the major and trace element composition of sediments. The main part of Fe and Mn is confined to fraction <10 μm. 相似文献
12.
Camomilia A. Bright Timothy W. Lyons Michael D. Glascock 《Geochimica et cosmochimica acta》2009,73(6):1609-190
Past workers have used rare-earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry. To explore the potency of this approach, we analyzed Pennsylvanian conodonts from limestones, gray shales, and black shales of the Fort Scott and Pawnee formations (Desmoinesian) and Swope and Dennis formations (Missourian) in Kansas, Missouri, and Iowa, U.S.A. Analysis of individual platform conodonts from seven taxa using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) revealed a consistent enrichment in the middle rare-earth elements (MREE). Analogous MREE enrichment has been observed in authigenic apatite and bulk samples of phosphate-rich black shales from the same formations. Importantly, however, phosphate-depleted shales intimately associated with the P-rich intervals are relatively depleted in MREE. These antithetic patterns argue convincingly for secondary migration from the bulk sediment into the phosphate, and the extent of MREE enrichment in the conodonts is correlated positively with the total REE content. MREE enrichment in conodonts does not vary systematically as a function of lithology, stratigraphic level, conodont genus, geographic location, or with independent estimates of paleoredox conditions in the bottom waters. Collectively, these results argue for postmortem (diagenetic) REE uptake resulting in a pronounced (and progressive) MREE enrichment. Any cerium anomalies, if initially present, were masked by diagenetic uptake of REE. Paleoenvironmental interpretations of conodont REE, particularly for samples exhibiting MREE enrichment, should therefore be viewed with caution. 相似文献
13.
Kenneth M. Towe 《Precambrian Research》1983,20(2-4)
Evidence and arguments increasingly in favor of free oxygen in the Earth's early atmosphere renew the constraints on the environmental significance of Precambrian banded iron formations. An early moist greenhouse atmosphere with a delay in, and gradual growth of, the world oceans offers a mechanism to provide a geochemically and mechanically segregated source of iron and silica for banded iron formation, while simultaneously ‘cannibalizing’ evidence for early Archean red beds. The model supports the high rates of weathering necessary to remove initially outgassed CO2 quickly, favors continuity in early biogenic evolution, provides a mechanism for hydrogen and strontium isotope partitioning, and is consistent with iron oxide facies that are devoid of organic carbon or stromatolites that are not encrusted by iron oxide. 相似文献
14.
Distinctive trace-metal concentrations characterize Cenomanian to Eocene marine carbonates from Israel. The Cenomanian-Turonian platform carbonates, including clayey formations, exhibit low average values ranging between 2 and 29 ppm for Zn, Cr, V, Ni, Cu, U and Co. The Santonian-Campanian and Early to Middle Eocene marine chalks show higher average concentrations of these trace-metals ranging between 3 and 56 ppm. The highest average concentrations of these metals (5–118 ppm) are found in the Maastrichtian and in the Palaeocene marine chalks and marls. The possible relationship between these metal background levels and the lithology, the biogenic productivity, the organic matter content, the iron oxide concentration, the rate of sedimentation of the studied time-rock units as well as the palaeogeographical changes are discussed. The extent of the exposed palaeo-landmasses due to tectonics, the intensity of weathering conditions and the detritus supply into the basin, control primarily the iron and trace-metal content in the studied sediments. 相似文献
15.
Palaeohydraulic estimates have been made using time-tested standard empirical formula involving channel dimensions, especially channel depth, in four Indian Proterozoic fluvial formations. These are the Mesoproterozoic Ramdurg, younger Mesoproterozoic Muchkundi and Neoproterozoic Cave Temple Arenite in Karnataka, and Upper Rewa Sandstone in central India. The basic data came from direct measurement of decompacted thicknesses of completely preserved channel-fills or bedforms, and more commonly of cross-sets. The result, in combination with data derived by others in a similar way from a few other Precambrian fluvial formations helps to provide a new insight into the palaeohydraulics of Precambrian rivers.River gradients appear to have been steeper during the Precambrian; the possibly continuous range of variation in river gradients from alluvial fans to the plains, as a whole shifted to higher values during the Precambrian epoch. The likely reason is a greater possibility of sediment bypassing on vegetation-free land. Concomitant downstream increase in discharge was enhanced in Precambrian rivers due to lack of withdrawal of groundwater through biogenic activity. Precambrian rivers were commonly ephemeral, but downstream the ephemerality index was reduced and some rivers might have been perennial where they debouched into standing bodies of water. The Precambrian river deposits studied generally had smaller width and depth with respect to Phanerozoic and modern rivers, possibly due to unstable substratum causing surface run-off tended to be impelled along multiple independent minor channels. 相似文献
16.
Sushmitha Baskar R. Baskar Natuschka Lee P. K. Theophilus 《Environmental Geology》2009,57(5):1169-1186
The Mawsmai cave and Krem Phyllut caves, East Khasi hills, Meghalaya, India has so far not yet attracted the attention of
geomicrobiologists. Observations and hypotheses on the possible influence of identified microorganisms for speleothem formations
in Meghalaya are reported for the first time. XRD studies identified calcite in speleothems and gypsum in cave wall deposits
as the dominant minerals. SEM-EDAX showed interesting microfabric features showing strong resemblance with fossilised bacteria,
calcified filaments, needle calcite and numerous nano scale calcite crystals, highly weathered and disintegrated crystals
of calcite, that point towards a significant microbial influence in its genesis. Thin section petrography showed laminated
stromatolitic features. The microorganisms identified by conventional isolation and further evaluation of isolates by molecular
techniques include Bacillus cereus, Bacillus mycoides, Bacillus licheniformis, Micrococcus luteus, and Actinomycetes. Microscopic observations also showed unidentifiable cocci and four unidentifiable strains of CaSO4 (gypsum) precipitating bacteria. Experimental studies confirmed that these bacteria are able to precipitate calcium minerals
(calcite, gypsum, minor amounts of dolomite) in the laboratory. These results allow us to postulate that species like these
may contribute to active biogenic influence in the cave formations at Meghalaya. 相似文献
17.
In the Neoarchaean intracratonic basin of the Kaapvaal craton, between approximately 2640 Ma and 2516 Ma, two successive
stromatolitic carbonate platforms developed. Deposition started with the Schmidtsdrif Subgroup, which is probably oldest in
the southwestern part of the basin, and which contains stromatolitic carbonates, siliciclastic sediments and minor lava flows.
Subsequently, the Nauga formation carbonates were deposited on peritidal flats located to the southwest and were drowned during
a transgression of the Transvaal Supergroup epeiric sea, around 2550 Ma ago. This transgression led to the development of
a carbonate platform in the areas of the preserved Transvaal and Griqualand West basins, which persisted for 30–50 Ma. During
this time, shales were deposited over the Nauga Formation carbonates in the southwestern portion of the epeiric sea. A subsequent
period of basin subsidence led to drowning of the stromatolitic platform and to sedimentation of chemical, iron-rich silica
precipitates of the banded iron formations (BIF) over the entire basin. Carbonate precipitation in the Archaean was largely
due to chemical and lesser biogenic processes, with stromatolites and ocean water composition playing an important role. The
stromatolitic carbonates in the preserved Griqualand West and Transvaal basins are subdivided into several formations, based
on the depositional facies, reflected by stromatolite morphology, and on intraformational unconformities; interbedded tuffs
and available radiometric age data do not yet permit detailed correlation of units from the two basins. Thorough dolomitisation
of most formations took place at different post-depositional stages, but mainly during early diagenesis. Partial silicification
was the result of diagenetic and weathering processes. Karstification of the carbonate rocks was related to periods of exposure
to subaerial conditions and to percolation of groundwater. Such periods occurred locally at the time of carbonate and BIF
deposition. Main karstification, however, probably took place during an erosional period between approximately 2430 Ma and
2320 Ma.
Received: 15 September 1996 · Accepted: 12 May 1998 相似文献
18.
生物成因煤层气的生成及其资源意义 总被引：13，自引：1，他引：13
生物成因煤层气一般可分为原生和次生生物成因，它们在生成机理上有许多相似之处，但也有所不同，导致后期保存和同位素组成上的差异。研究指出，原生生物成因气不能被大量保留在煤层中，气田中的生物成因气多为次生生物成因气；次生生物成因煤层气分布比较普遍，含量较为丰富，且生物成因煤层气埋藏深度浅，勘探成本低，因此次生生物成因煤层气具有不容忽视的巨大资源潜力。 相似文献
19.
生源物质作为影响水质的重要因素,其在河流中的迁移转换一直倍受关注。水沙界面物质交换过程受众多环境和水动力因素的影响,过程极其复杂,不仅影响着河流生源要素的通量演变规律,还关系到河流水环境问题。为探究水沙界面生源物质迁移转化过程及作用机制,结合国内外研究最新进展,对泥沙颗粒与生源物质的微界面作用、水沙界面对生源物质的迁移转化作用、水流条件对泥沙吸附解吸生源物质作用机理进行总结和概述,总结阐述了河流水质模型和闸坝泵条件下的水环境调控模型,最后指出平原河流水沙运动对生源物质输运作用机理及水环境调控。针对上述已有的研究成果和存在不足,对今后研究方向提出展望。 相似文献
20.
《China Geology》2019,2(2):227-237
Research on the biomineralization in modern seafloor hydrothermal systems is conducive to unveiling the mysteries of the early Earth’s history, life evolution, subsurface biosphere and microbes in outer space. The hydrothermal biomineralization has become a focus of geo-biological research in the last decade, since the introduction of the microelectronic technology and molecular biology technology. Microorganisms play a critical role in the formations of oxide/hydroxides (e.g. Fe, Mn, S and Si oxide/hydroxides) and silicates on the seafloor hydrothermal systems globally. Furthermore, the biomineralization of modern chemolithoautotrophic microorganisms is regarded as a nexus between the geosphere and the biosphere, and as an essential complement of bioscience and geology. In this paper, we summarize the research progress of hydrothermal biomineralization, including the biogenic minerals, the microbial biodiversity, and also the interactions between minerals and microorganisms. In the foreseeable future, the research on hydrothermal biomineralization will inspire the development of geosciences and biosciences and thus enrich our knowledge of the Earth’s history, life evolution and even astrobiology.© 2019 China Geology Editorial Office. 相似文献