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1.
E. S. Bazilevskaya 《Doklady Earth Sciences》2009,429(2):1417-1419
This work is devoted to some problems of the genesis, chemical composition, and forming rates of iron-manganese ores (IMOs)
in the ocean bed due to real outlooks of their development in the years 2015–2020. It is particularly accentuated that ores
are continuously originating on the ocean bed with rates of several millimeters per million years. IMO accumulation in modern
oceans is greatly more than the age of the mobile ocean bed. These unique ores are not only sorbents of some strategic microelements,
but also store easily mobilized oxygen, which is able to supersaturate water in endogenic processes on the ocean bed, blocking
their expansion in a limited volume. Thus, iron-manganese ores must be mined only with nonpolluting methods and under the
control of competent authorities. 相似文献
2.
S. B. Misra 《Journal of Earth System Science》1984,93(4):447-464
Depositional environment of the Krol group varied temporally from subtidal in the Manora to intertidal in the Sleepy Hollow
times. The conditions that succeeded were peritidal in the Ayarpatta and supratidal in the Narainnagar times. These conditions
were the main controlling factors in the growth and development of the algal stromatolites. The Manora formation, due to subtidal
conditions, and the Sleepy Hollow formation, due to detrital influx, are almost devoid of stromatolites. The carbonates of
the Ayarpatta formation representing a peritidal complex possess columnar and oncolitic stromatolites, while the sediments
of the Narainnagar formation characterized by supratidal features contain blistered, domal and crinkled-laminar forms. The
types and sizes of stromatolites therefore are governed by the depositional conditions prevailing in the sedimentary basin. 相似文献
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Response of the interaction between groundwater and other components of the environment in Mexico 总被引:2,自引:0,他引:2
J. J. Carrillo-Rivera A. Cardona R. Huizar-Alvarez E. Graniel 《Environmental Geology》2008,55(2):303-319
This article reviews and discusses environmental aspects related to vertical upward and downward groundwater flow. Flow systems
are an important tool to understand groundwater functioning as related to the environment, in terms of obtaining indicators
of human impact and solving specific questions about a groundwater-environment system that has been influenced by anthropogenic
means. This involves two broad processes. First, groundwater changes due to activities of man in the surrounding environment
as a result of: (1) alteration of recharge by modification of native vegetation and original soil cover; (2) reduction of
groundwater discharge to coastal areas and to inland water bodies producing desiccation of wetlands, lakes and springs; (3)
groundwater contamination from sewage looses and uncontrolled waste disposal locations, and (4) up-welling of undesirable
water quality induced by extraction. Second, environmental alterations due to changes in the groundwater regime produce: (1)
increase in soil erosion through the disappearance of vegetation due to water-table decline, (2) water-table rise due to unplanned
artificial recharge resulting from water imports to a catchment, (3) decline in water levels for improper extraction regime,
(4) soil subsidence due to extraction mismanagement, and (5) disappearance of phreatofites caused by excessive extraction.
Unless further understanding between groundwater and the other components of the environment is sought, the relationship between
people and its environment will be subject to some of these effects, potentially endangering adequate human development and
sustainable water management. 相似文献
5.
该图通过区域地质环境条件差异和主要人类工程活动引起的地质灾害,来反映主要人类工程活动与地质环境相互作用的规律。从而,圈划出主要人类工程活动与地质环境相互作用强列地区,它们是沪宁杭地区、湘中南桂东地区、攀西一六盘水地区。 相似文献
6.
Robert L. McConnell 《Precambrian Research》1975,2(3):317-328
The Apache Group of central Arizona is subdivided into, from base upward, the Pioneer Formation, the Dripping Spring Quartzite and the Mescal Limestone. Radiometric age determinations by Silver, and Livingston and Damon indicate an age of 1.2–1.4 billion years. Within the Mescal Limestone, algal stromatolites form a conspicuous biostrome, commonly 20–25 m thick. The basal 1–5 m of the biostrome consists of up to three zones of digitate stromatolites, which often form discrete bush-like bioherms. These forms are interpreted as Baicalia baicalica, Parmites sp. and Tungussia sp.; the latter form previously reported by Cloud and Semikhatov (1969). The form Parmites is interpreted as a modification of digitate stromatolites probably by decrease in current velocity within the shallow marine environment, which allowed discrete heads to coalesce. Basal digitate forms are replaced upward in the biostrome by domal and undulatory laminated (stratiform) stromatolites, interpreted to represent gradual upward shoaling, with lower intertidal and subtidal forms (digitate morphology) being replaced by upper intertidal and possibly supratidal forms (stratiform types).The digitate form B. baicalica is suggested by Soviet workers to be indicative of Middle Riphean time (1350-950 m.y.). While many empirical data suggest the possibility of gross subdivision of Late Proterozoic time on the basis of algal stromatolite “zones”, the intercontinental applicability and the ultimate validity of this concept in unresolved. 相似文献
7.
The preservation potential of some recent stromatolites 总被引:3,自引:0,他引:3
ROBERT K. PARK 《Sedimentology》1977,24(4):485-506
Stromatolites are laminated organo-sedimentary structures, generally compared to present day blue-green algal mats. Their morphology, species composition and overall extent are largely governed by the amount of wetting, although other factors such as competition, predation and desiccation, also contribute. The Trucial Coast mats are essentially intertidal. Stromatolite accretion rates in this area are of the order of 0·2 mm p.a. but lamina growth is far from regular. The area is also characterized by the development of evaporites, especially gypsum which proves to be an important agent of mat destruction. The growth of crystals causes disruption within the upper portions of the stromatolite section with the result that none of the upper intertidal mat forms are preserved. Other agencies of destruction include bacterial decay, desiccation and dehydration, and compaction under burial which may depress and deform the original mat relief. Decay results in the almost total loss of cellular contents, only a few empty sheaths and the pigment surviving into the fossil record. Preservation may be effected via (a) burial or (b) lithification. However, few modern algal mat structures bear any resemblance to fossil stromatolite heads with the exception of those from Shark Bay. From this, one might infer that pene-contemporaneous lithification is a prerequisite for their preservation. 相似文献
8.
The results of the study of submicroscopic structures of oceanic oxide ores are described. The objects of study were Co-bearing Fe-Mn crusts from the Magellan Seamounts and Fe-Mn nodules from the Clarion-Clipperton province. The evolution of structural elements is traced in the crust section from the Lower Campanian-Maastrichtian to Pliocene-Quaternary layers. It was found that growing nodules actively entrap hosting sediments into the layered cover. The entrapment mechanism of sediments by nodules was revealed. 相似文献
9.
农业生态与土壤环境中锌元素的关系 总被引:12,自引:0,他引:12
本文论述了锌元素的地球化学特征和分布,农作物与锌元素的有关及锌元素有效态含量的控制因素:土壤的性质与母质,土壤的酸碱度,土壤的有机质含量以及锌肥的种类,施用方法与效果。 相似文献
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Michel Brossard Gustavo Adolfo de Freitas Fregonezi Maria de Fátima Guimarães Cristiane de Conti Medina Amarildo Pasini Lourival Vilela Miguel Angel Ayarza 《Comptes Rendus Geoscience》2012,344(1):41-49
Ferralsols are characterized by poorly-defined horizons, weak macrostructure and strong development of a fine granular structure comprising subangular micro-aggregates. In this study, the morphological and physical modifications caused by earthworm activity in a clayey ferralsol were analysed. After describing soil structures, undisturbed samples were taken for evaluating aggregates and determining clod bulk density and particle density. Soil water retention properties were measured and an inventory of soil invertebrate macrofauna was created. The structural and porous transformations were due to aggregates created by earthworm activity. Changes in bulk density can be associated with pore modifications caused by a change in the proportions of aggregate types, and a notable reduction of total porosity was measured, tending to increase soil volume with dense aggregates. Structural modifications affected the topsoil down to 0.5 m and water retention between −1 and −33 kPa, the principal water compartment of these soils. 相似文献
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自从Kalkowsky在1908年构筑了叠层石的术语之后,叠层石一直是地质学家采用不同方法研究和思考的主题,而且一直被当作证明地球早期生命历史的代表物而得到深入调查。叠层石确实为地球早期生命历史提供了间接而且复杂的证据,所以,现代叠层石确实代表着明显的生物信号而成为研究的焦点。最为引人注目的是,现代叠层石的多样化构成,确实表明了蓝细菌生物席建造了叠层石,而且进一步表明了微生物席转化成叠层石不是一个直接的作用过程。那些反映现代叠层石多样化构成的典型实例包括:(1)南极Untersee地区的湖泊相锥状泥质叠层石;(2)新西兰North群岛被称为煎锅湖的热水湖泊中以及美国黄石国家公园热泉中的硅质叠层石;(3)巴哈马台地、澳大利亚鲨鱼湾以及巴西东南部海湾碳酸盐沉积物构成的叠层石。由于蓝细菌微生物席是否代表了古代叠层石的形态学前体总是存在争议,而且在生命的图像中叠层石一直是一个迷惑的关键片段,因此,现代叠层石的多样化构成,将成为认识古代叠层石形成的关键和窗口。立足于前人的研究成果,追踪和总结现代叠层石的多样化构成,以及它们所代表的沉积作用和微生物新陈代谢活动丰富而复杂的信息,将不但丰富微生物沉积学的研究内容,还将拓宽沉积相分析的基本内容,对深入了解叠层石复杂的沉积学特征和生物学属性具有重要的科学意义。 相似文献
15.
《International Geology Review》2012,54(6):643-651
The chrome spinellids from ores associated with basic formations differ from chromites found in ultrabasic formations by their higher content of alumina and iron, and by the presence of FeAl204. Chromites of early and late magmatic origin differ in composition. During the formation of late magmatic chromites the filtration effect is accompanied by recrystallization of primary magmatic dunites and generation of rims around the ore zones. These rims contain more magnesium, because iron was extracted by the crystallizing chrome spinellids. -- E. A. Alexandrov. 相似文献
16.
矿物细颗粒物和微生物个体都是大气颗粒物(PM)重要组成部分,它们在形态、共生关系和空气动力学行为上均有高关联度.本文对可吸入颗粒物(IP)和可吸入矿物细颗粒(IMG)的颗粒特性、自由基和生物活性、IP和IMG与微生物相互作用效果的研究现状做了阐述,指出大气颗粒物与微生物的相互作用的重要性.提出今后应重点研究可吸入矿物细颗粒物的环境化学与微生物作用行为,研究IMG-微生物体系近尺寸作用体系中的尺寸效应、界膜作用等对矿物颗粒物表面形态、表面电性、表面基团及自由基等的影响,分泌蛋白质与相变、元素变价、溶解(络合)的关系以及由此引起的颗粒物活性和生物毒性的变化等. 相似文献
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In iron-manganese nodules from the floor of Pacific ocean, Baltic, White Sea and Kara Sea, iron bydroxide '-FeOOH was analysed in the laboratory. In buried ooze, reduction processes generate Fe(HCO3)2 which migrates into the upper part of the bottom ooze and into near bottom sea water where Fe(OH)2 is formed. The oxidation process of Fe2+ to Fe3+, without participation of iron bacteria, leads to the topotactic transformation of Fe(OH)2 to '-FeOOH. Marine water does not contain Fe2+ and cannot be a direct source of iron deposited in the nodules. Discovery of '-FeOOH in marine nodules permits the consideration that both iron and manganese were derived from the buried bottom mud, which during diagenetic processes led to the transfer of these metals in solutions and their upward migration. 相似文献
19.
V. A. Matveev 《Doklady Earth Sciences》2017,474(1):494-497
The morphology of fossilized biogenic particles and the elemental composition of biogenic formations, discovered for the first time in Lower Silurian deposits within the Timan–Northern Urals region, are considered. The diversity of biogenic formations identified in stromatolites indicates a high level of activity of microorganisms forming the cyanobacterial mat and confirms the microbial origin of the Wenlockian stromatolite buildups. 相似文献
20.
The role of endolithic cyanobacteria in the formation of lithified laminae in Bahamian stromatolites 总被引:5,自引:0,他引:5
The microboring activity of endolithic cyanobacteria plays a major role in the formation of the dominant lithified laminae in modern marine stromatolites in the Exuma Cays, Bahamas. These stromatolites are composed primarily of fine-grained carbonate sand that is trapped and bound by the filamentous cyanobacteria Schizothrix sp.. Periodic introduction of coccoid endolithic cyanobacteria Solentia sp. during hiatuses in stromatolite growth associated with very low rates of sedimentation results in the formation of lithified horizons, 200–1000 μm thick. These layers consist of micritized grains that are welded together at point contacts. The micritization is caused by extensive microboring and carbonate precipitation within boreholes concurrent with endolithic activity. Grain welding occurs when boreholes cross from one grain to another at point contacts. Thus, microboring destroys original grain textures but, at the same time, plays a constructional role in stromatolite growth by forming lithified layers of welded grains. These lateral bands of fused carbonate grains help to stabilize and preserve the stromatolite deposits. 相似文献