The paper summarizes the results of thermomagnetic analysis concerning the distribution of metallic iron in the sediments
ranging in age from Miocene to Early Cretaceous sampled from the following sections: Gams (Austria); Verkhorech’e and Sel’bukhra
(the Crimea); Kvirinaki and Tetritskaro (Georgia); Aimaki, Dzhengutai, Madzhalis, and Gergebil (Ciscaucasia, Russia); Klyuchi
and Teplovka (Volga region, Russia); Koshak (Kazakhstan); and Khalats and Kara-Kala (Turkmenia). Small amounts of native iron
(from 10−5% to 0.05%) are identified in 521 samples of 921 studied; i.e., iron particles are almost pervasive. This fact traces the
origin of these particles to cosmic dust. Some established features point to the heterogeneous character of the cosmic dust:
(a) the samples clearly fall into two groups. One group comprises the rocks that contain iron particles; the rocks of the
other group are iron-free. In the first group, four intervals are distinguished where the sediments are globally enriched with iron with constant nickel content (5–6%); (b) in terms of composition, the iron particles are divided into
three groups. The first group contains pure iron; the particles pertaining to the second group contain iron with a minor amount
of nickel typical for kamacite; and the third group comprises the particles of Fe-Ni alloy with more than 20% nickel. The
first and the second groups are ubiquitous; the particles of the third group are spread locally. They bear no relation to
cosmic dust and are probably associated with the meteoritic impacts. 相似文献
The paper continues a cycle of petromagnetic investigations of epicontinental deposits at the Mesozoic-Cenozoic (K/T) boundary and is devoted to the study of the Gams section (Austria). Using thermomagnetic analysis, the following magnetic phases are identified: goethite (TC = 90–150°C), hemoilmenite (TC = 200?300°C), metallic nickel (TC = 350–360°C), magnetite and titanomagnetite (TC = 550–610°C), Fe-Ni alloy (TC = 640–660°C), and metallic iron (TC = 740–770°C). Their concentrations are determined from M(T). In all samples, ensembles of magnetic grains have similar coercivity spectra and are characterized by a high coercivity. An exception is the lower coercivity of the boundary clay layer due to grains of metallic nickel and iron. With rare exceptions, the studied sediments are anisotropic and generally possess a magnetic foliation, which indicates a terrigenous accumulation of magnetic minerals. Many samples of sandy-clayey rocks have an inverse magnetic fabric associated with the presence of acicular goethite. The values of paramagnetic and diamagnetic components in the deposits are calculated. According to the results obtained, the K/T boundary is marked by a sharp increase in the concentration of Fe hydroxides. The distribution of titanomagnetite reflects its dispersal during eruptive activity, which is better expressed in the Maastrichtian and at the base of the layer J. The along-section distribution of metallic iron, most likely of cosmic origin, is rather uniformly chaotic. The presence of nickel, most probably of impact origin, is a particularly local phenomenon as yet. The K/T boundary is not directly related to an impact event. 相似文献
Thermomagnetic and microprobe analyses are carried out and a set of magnetic characteristics are measured for 25 meteorites and 3 tektites from the collections of the Vernadsky Geological Museum of the Russian Academy of Sciences and Museum of Natural History of the North-East Interdisciplinary Science Research Institute, Far Eastern Branch of the Russian Academy of Sciences. It is found that, notwithstanding their type, all the meteorites contain the same magnetic minerals and only differ by concentrations of these minerals. Kamacite with less than 10% nickel is the main magnetic mineral in the studied samples. Pure iron, taenite, and schreibersite are less frequent; nickel, various iron spinels, Fe-Al alloys, etc., are very rare. These minerals are normally absent in the crusts of the Earth and other planets. The studied meteorites are more likely parts of the cores and lower mantles of the meteoritic parent bodies (the planets). Uniformity in the magnetic properties of the meteorites and the types of their thermomagnetic (MT) curves is violated by secondary alterations of the meteorites in the terrestrial environment. The sediments demonstrate the same monotony as the meteorites: kamacite is likely the only extraterrestrial magnetic mineral, which is abundant in sediments and associated with cosmic dust. The compositional similarity of kamacite in iron meteorites and in cosmic dust is due to their common source; the degree of fragmentation of the material of the parent body is the only difference. 相似文献
Results of investigation of the cosmic matter in the transitional clay layer at the Cretaceous-Paleogene boundary in the Gams
section, Eastern Alps, are presented. A great diversity of iron microspherules and particles of different morphologies, pure
nickel spherules, awaruite (Fe3Ni) particles, and diamond crystals are discovered. Iron microspherules are also met in the overlying Paleocene deposits,
but their diversity there is not great. The discovered metallic microspherules and particles are described, their chemical
compositions are presented, and their origin is discussed. 相似文献
The data on the distribution of native iron particles in sediments yielded by thermomagnetic analysis are explored. It is shown that the accumulation of iron particles in sediments is statistically inversely linked with the rate of sedimentation and the frequency of geomagnetic reversals and statistically directly linked to the intensity of the geomagnetic field. These dependences highlight the predominance of cosmic iron particles in the studied sediments. 相似文献
Thermomagnetic and microprobe studies of native iron in the terrestrial upper-mantle hyperbasites (xenoliths in basalts), Siberian traps, and oceanic basalts are carried out. The results are compared to the previous data on native iron in sediments and meteorites. It is established that in terms of the composition and grain size and shape, the particles of native iron in the terrestrial rocks are close to each other and to the extraterrestrial iron particles from sediments and meteorites. This suggests that the sources of the origin of these particles were similar; i.e., the formation conditions in the Earth were close to the conditions in the meteorites’ parent bodies. This similarity is likely to be due to the homogeneity of the gas and dust cloud at the early stage of the solar system. The predominance of pure native iron in the sediments can probably be accounted for by the fact that interstellar dust is mostly contributed by the upper-mantle material of the planets, whereas the lower-mantle and core material falls on the Earth mainly in the form of meteorites. A model describing the structure of the planets in the solar system from the standpoint of the distribution of native iron and FeNi alloys is proposed. 相似文献
The thermomagnetic and microprobe analyses of sedimentary samples from DSDP 386, 387, 391A, and 391C boreholes in the northwestern Atlantic reveal the ubiquitous occurrence of particles of native iron. The concentrations of native iron are bimodal everywhere with the zero mode necessarily present. The nickel admixture in native iron forms two groups, one represented by pure iron and the comprising native iron with 5–6% Ni. The redeposition of iron particles manifests itself in the correlation between the concentrations of these particles and terrestrial minerals (magnetite), as well as in the equalization and reduction of the concentration of the iron particles. Pyrite and pyrrhotite are widespread in the studied sediments, and the distribution of native iron does not depend on the presence of pyrite (i.e., on redox conditions) in them. At the same time, the distributions of pyrite and particles of magnetite + titanomagnetite are inversely correlated, which can probably be accounted for by the partial dissolution of magnetite and titanomagnetite in the reducing conditions. The increased concentration of particles of volcanogenic homogeneous titanomagnetite is revealed in the volcanoclastic turbidites of the Oligocene and early and middle Miocene age at the base of the Bermuda Rise (borehole 386). The titanomagnetite composition is characteristic of the basalts of plume magmatism; it corresponds to the depth of the magmatic source in the interval of 50–25 km. 相似文献
59Ni in 0.4 g of nickel from deep-sea sediments was measured with an extremely low-level X-ray spectrometer. The obtained specific activity was (5.9 ± 1.8) × 10?2 dpm/kg sediments. The59Ni activity induced by proton and alpha particle irradiation in outer space can be estimated as 300 dpm/kg dust. Hence, the content of extraterrestrial dust in deep-sea sediments was not more than 200 ppm. 相似文献
The paper presents results of detailed magnetomineralogical and microprobe studies of sediments at the Cretaceous/Paleogene (K/T) boundary in two epicontinental sections in the Eastern Alps (Austria), where deposits, including the K/T boundary, outcrop along the Gams River and its tributaries. K/T boundary layers in these sections are similar in the set of such magnetic minerals as iron hydroxides, ferrospinels, hemoilmenite, titanomagnetite, magnetite, hematite, and metallic iron. However, the boundary layer in the Gams-1 section is distinguished by the presence of metallic nickel and its alloy with iron and by the absence of iron sulfides, whereas nickel has not been discovered in the Gams-2 section, which, however, contains iron sulfides of the pyrite type. Therefore, these minerals occur locally. It is suggested that enrichment in iron hydroxides of a common origin can be regarded as a global phenomenon inherent in the K/T boundary and unrelated to an impact event. 相似文献
The implantation of artificial quartz with nickel ion has succeeded in using a heavy ion accelerator. The quartz with nickel
ion is called ”nickel quartz“. The sensitivity of their thermoluminescence (TL) response to the beta radiation was decreased
with the increasing of irradiating and heating times. Two TL characteristics have appeared: the sensitivity of TL response
at lower temperature (ll0°C) peaks of the nickel quartz to beta radiation is higher than that of the pure quartz, this results
from the Ni+1 ion entering the quartz lattice; and a new peak appearing at 445°C may be related with both Ni+1 and Ni+3. 相似文献
Improved estimates of the amount of subsurface gas hydrates are needed for natural resource, geohazard, and climate impact assessments. To evaluate gas hydrate saturation from seismic methods, the properties of pure gas hydrates need to be known. Whereas the properties of sediments, specifically sands, and hydrate‐bearing sediments are well studied, the properties of pure hydrates are largely unknown. Hence, we present laboratory ultrasonic P‐wave velocity and attenuation measurements on pure tetrahydrofuran hydrates as they form with reducing temperatures from 25°C to 1°C under atmospheric pressure conditions. Tetrahydrofuran hydrates, with structure II symmetry, are considered as proxies for the structure I methane hydrates because both have similar effects on elastic properties of hydrate‐bearing sediments. We find that although velocity increased, the waveform frequency content and amplitude decreased after the hydrate formation reaction was complete, indicating an increase in P‐wave attenuation after hydrate formation. When the tetrahydrofuran hydrate was cooled below the freezing point of water, velocity and quality factor increased. Nuclear Magnetic Resonance results indicate the presence of water in the “pure hydrate” samples above the water freezing point, but none below. The presence of liquid water between hydrate grains most likely causes heightened attenuation in tetrahydrofuran hydrates above the freezing point of water. In naturally occurring hydrates, a similarly high attenuation might relate to the presence of water. 相似文献
The native iron particles that were previously detected by thermomagnetic and microprobe analyses in the sediments of different age in many regions of the world are of extraterrestrial origin. The similarity in the compositions, grain shapes, and sizes observed in the extraterrestrial and terrestrial particles of native iron testifies to the common production conditions of iron particles during the formation of planets. In this paper, the single finding of terrestrial iron in the lacustrine sediments of the Zhombolok volcanic region, East Sayan, is discussed. The uniqueness of the results indicates that the spatial distribution of the particles of native iron is limited to a fairly narrow area around their source—volcanic eruption or/and the fall of a large meteorite. 相似文献
Results of petromagnetic studies of epicontinental sediments at the Mesozoic-Cenozoic (K/T) boundary are generalized. Their analysis shows that an abrupt rise in the concentration of iron hydroxides is confined to this boundary. Their concentration is highest at the base of the boundary layer and drops by more than two times at it top. As distinct from iron hydroxides, other magnetic minerals were variously accumulated, depending on their origin and local deposition conditions of terrigenous material (for example, accumulation of particles of metallic iron and nickel, aerial transport of titanomagnetite grains of volcanic origin, and deposition of terrigenous particles of magnetite and ilmenite). 相似文献
The paper is concerned with the detailed sectional petromagnetic study of boundary clay in four 1A, 1B, 2A, and 2B Gams sections (in Austria). The composition of basic magnetic minerals in the boundary clay of all sections is similar. They are composed of iron hydroxides, hemoilmenite, titanomagnetite, magnetite, hematite, and iron. The difference is the presence in the Gams-1 section of metallic nickel, which is absent in the Gams-2 section, and the presence in the latter of iron sulfides of the pyrite type. Grains of titanomagnetite and ilmenite, connected with volcanic activity, are nonuniformly distributed in the boundary layer, which indicates their irregular precipitation in time. The ensemble of magnetic grains is characterized by high coercitivity. The boundary layer is characterized by an increased content of iron hydroxides. This effect is a global phenomenon and is irrelevant to the local physicogeographical conditions. Such a characteristic of impact events as the particles of metallic iron is almost absent in the boundary layer. 相似文献
The kinetics of metamorphism of the Staroe Boriskino C2 chondrite heated at 450°C in an inert atmosphere of helium flow was investigated. After being heated at 450°C during 160 minutes one specimen was moreover heated for 10 minutes at 500°C. The phase distribution was determined by means of Mössbauer spectroscopy, X-ray diffraction analysis, and electron probe microanalysis.The material changes rapidly (1–2 minutes). As a result of dehydration, the iron of the phyllosilicate is oxidized, the charge compensation being realized through the removal of iron and magnesium cations with the formation of magnetite and forsterite. Upon 10 minutes additional heating at 500°C iron appears in the olivine structure, the degree of iron oxidation declines, and magnetite disappears. Possible trends of change of C2 chondrite material are:
Interstitial water samples from the Guatemala Basin and the coast of Baja California have been analyzed for manganese, iron, copper, nickel and nitrate. The data provide a systematic look at changes in trace metal diagenesis proceeding from red clay to highly reducing nearshore sediments.In red clay sediments, the nitrate concentrations suggest that only aerobic respiration is occurring. Manganese and iron are below detection. Nickel concentrations remain the same as in bottom seawater but copper shows a pronounced maximum just at the sediment/water interface. Proceeding to hemipelagic sediments, denitrification becomes increasingly important and manganese and iron remobilization occur in the sediments.The linear manganese and nitrate profiles suggest regions of production or consumption separated by zones of diffusion. This differs from the conventional picture of a continuous series of reactions within the sediments. Manganese reduction always occurs before iron reduction. The pore water nickel correlates well with manganese in these sediments, suggesting that nickel is associated with MnO2 in the solid phase. The pore water flux ratio of manganese and nickel agrees well with the ratio in solid phase authigenic oxides. Copper still displays a core top concentration maximum as well as a second maximum associated with the remobilized manganese. The calculated ratio of the Cu/C flux ratios support the argument for copper remobilization during organic carbon oxidation. Comparison of the upward and downward diffusive fluxes with the rate of copper buried by sedimentation shows that at least half of the copper buried must be of diagenetic origin and less than 25% of the copper reaching the sediments is buried. 相似文献
The potential relation between outdoor pollutants and the quality of indoor air was evaluated. A case study was carried out in the small town of Zyrardow situated south-west of Warsaw, Poland. The indoor dust from 20 apartments from several parts of the town that are anticipated to be exposed to various levels of pollution was investigated: a mildly polluted area (suburban), a heating plant area, a post-industrial area and the city center. For evaluation of indoor dust several magnetic parameters (mass-specific magnetic susceptibility χ, its temperature dependence, anhysteretic remanent magnetization, hysteresis loop parameters) were applied. Analysis of magnetic properties was supplemented by analysis of chemical elements: Cd, Cu, Co, Cr, Fe, Mn, Ni, Pb and Zn. Depending on the location of apartments, large variations in concentration, mineralogy and grain-size of magnetic particles were detected. The thermomagnetic analysis revealed magnetite as a primary magnetic phase. In indoor dust, the Curie temperature of ~760°C and soft hysteresis loops with relatively low coercivity values of ~1.5-5 mT are an attribute of metallic iron. The dust collected from apartments located near the local heating plant area, in contaminated post-industrial and suburban areas contains mainly magnetite and only a small amount of metallic iron. Mass-specific magnetic susceptibility is in the range from 40 to 200 × 10-8 m3kg-1 and linearly correlates with concentration of individual heavy metals: Ni, Cr, Co and Zn. Magnetic fraction of dust from the city center mainly consists of magnetite and variable amounts of metallic iron. Magnetic susceptibility shows linear correlations with concentration of Fe and concentration of individual heavy metals (Zn, Ni and Co) considered as traffic-related. The study demonstrates that metallic iron present in indoor dust is a potential marker of trafficrelated sources and it makes it possible to use magnetic methods as a tool for evaluation of traffic-related impact on indoor air levels. 相似文献
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