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1.
The edifice of Mount Rainier, an active stratovolcano, has episodically collapsed leading to major debris flows. The largest debris flows are related to argillically altered rock which leave areas of the edifice prone to failure. The argillic alteration results from the neutralization of acidic magmatic gases that condense in a meteoric water hydrothermal system fed by the melting of a thick mantle of glacial ice. Two craters atop a 2000-year-old cone on the summit of the volcano contain the world's largest volcanic ice-cave system. In the spring of 1997 two active fumaroles (T=62°C) in the caves were sampled for stable isotopic, gas, and geochemical studies.Stable isotope data on fumarole condensates show significant excess deuterium with calculated δD and δ18O values (−234 and −33.2‰, respectively) for the vapor that are consistent with an origin as secondary steam from a shallow water table which has been heated by underlying magmatic–hydrothermal steam. Between 1982 and 1997, δD of the fumarole vapor may have decreased by 30‰.The compositions of fumarole gases vary in time and space but typically consist of air components slightly modified by their solubilities in water and additions of CO2 and CH4. The elevated CO2 contents (δ13CCO2=−11.8±0.7‰), with spikes of over 10,000 ppm, require the episodic addition of magmatic components into the underlying hydrothermal system. Although only traces of H2S were detected in the fumaroles, most notably in a sample which had an air δ13CCO2 signature (−8.8‰), incrustations around a dormant vent containing small amounts of acid sulfate minerals (natroalunite, minamiite, and woodhouseite) indicate higher H2S (or possibly SO2) concentrations in past fumarolic gases.Condensate samples from fumaroles are very dilute, slightly acidic, and enriched in elements observed in the much higher temperature fumaroles at Mount St. Helens (K and Na up to the ppm level; metals such as Al, Pb, Zn Fe and Mn up to the ppb level and volatiles such as Cl, S, and F up to the ppb level).The data indicate that the hydrothermal system in the edifice at Mount Rainier consists of meteoric water reservoirs, which receive gas and steam from an underlying magmatic system. At present the magmatic system is largely flooded by the meteoric water system. However, magmatic components have episodically vented at the surface as witnessed by the mineralogy of incrustations around inactive vents and gas compositions in the active fumaroles. The composition of fumarole gases during magmatic degassing is distinct and, if sustained, could be lethal. The extent to which hydrothermal alteration is currently occurring at depth, and its possible influence on future edifice collapse, may be determined with the aid of on site analyses of fumarole gases and seismic monitoring in the ice caves. 相似文献
2.
Koichiro Fujimoto Hidemi Tanaka Takayuki Higuchi Naoto Tomida Tomoyuki Ohtani Hisao Ito 《Island Arc》2001,10(3-4):401-410
Abstract Mineralogical and geochemical studies on the fault rocks from the Nojima–Hirabayashi borehole, south-west Japan, are performed to clarify the alteration and mass transfer in the Nojima Fault Zone at shallow depths. A complete sequence from the hornblende–biotite granodiorite protolith to the fault core can be observed without serious disorganization by surface weathering. The parts deeper than 426.2 m are in the fault zone where rocks have suffered fault-related deformation and alteration. Characteristic alteration minerals in the fault zone are smectite, zeolites (laumontite, stilbite), and carbonate minerals (calcite and siderite). It is inferred that laumontite veins formed at temperatures higher than approximately 100°C during the fault activity. A reverse component in the movement of the Nojima Fault influences the distribution of zeolites. Zeolite is the main sealing mineral in relatively deep parts, whereas carbonate is the main sealing mineral at shallower depths. Several shear zones are recognized in the fault zone. Intense alteration is localized in the gouge zones. Rock chemistry changes in a different manner between different shear zones in the fault zone. The main shear zone (MSZ), which corresponds to the core of the Nojima Fault, shows increased concentration of most elements except Si, Al, Na, and K. However, a lower shear zone (LSZ-2), which is characterized by intense alteration rather than cataclastic deformation, shows a decreased concentration of most elements including Ti and Zr. A simple volume change analysis based on Ti and Zr immobility, commonly used to examine the changes in fault rock chemistry, cannot account fully for the different behaviors of Ti and Zr among the two gouge zones. 相似文献
3.
Florie A. Caporuscio Jamie N. Gardner Emily S. Schultz-Fellenz Richard E. Kelley 《Bulletin of Volcanology》2012,74(5):1023-1037
The objective of this study is to demonstrate the relationships among devitrification, vapor phase alteration, localization of gas emanations into fumarolic pipes, and initial deformation of the ash flow sheet during cooling and lithification. Utilizing a unique and temporary exposure of the Tshirege Member of the Bandelier Tuff near Los Alamos, New Mexico, we identify several zones of distinctly preserved fossil fumarolic activity. The fumarolic zones vary in width from a few centimeters to more than a meter. Almost ubiquitously, these zones demonstrate fines-depletion, induration of the margins, upward-flaring geometries, and intense fracturing of overlying geologic units. The fumaroles were preferentially located on post welding, early formed cooling joints that vented to the surface after the vapor phase alteration stage. The pipes were regularly spaced at distances of approximately 4.5?m (N–S) to 7?m (E–W). In turn the pipes were covered by a surge deposit and overlying tuff which rapidly lithified. The overlying tuff was then brecciated during continued fumarolic pipe emissions. Geochemical evaluations confirm the presence of high-temperature mineral (scapolite) indicative of transport of hot volcanic gases through these zones. The pipe centers and walls are depleted in SiO2, and enriched in Al2O3 and FeO. The overlying tuff breccia zones are enriched in Al2O3, FeO and MgO, and depleted in SiO2, NaO, and K2O. From comparison to other ignimbrite cooling histories, the fissures, fumaroles, and structures observed all likely formed in the first few decades after the deposition of the upper Tshirege subunits. This may have significant implications as to timing of initial cooling fractures and subsequent consolidation of gas emission pathways. 相似文献
4.
《Journal of Volcanology and Geothermal Research》1999,88(4):325-342
This work reports a study on the rare-earth element (REE) behaviour in the high-sulfidation-type superficial alteration and in the phyllic and propylitic alteration in the subsurface of the island of Vulcano. The results of this study demonstrate notable differences in the REE behaviour in the different alteration facies. In silicic alteration, all REE are equally strongly depleted; in advanced argillic alteration, LREE are quite immobile whereas HREE are strongly depleted; in intermediate argillic, phyllic and propylitic alteration, REE patterns are almost unchanged compared with their fresh rock equivalents. These features indicate that the behaviour of REE in hydrothermal alteration facies at La Fossa is mainly controlled by pH, availability of complexing ions in the fluid (mainly SO42− and, in the silicic facies, F−) and the presence of secondary minerals able to host REE in their structures. The origin of the acid fluids is related to the hypogenic introduction of prevalently magmatic acid gases produced by the degassing of the shallow magmatic system of La Fossa volcano. In the active high-temperature fumarolic field of La Fossa, REE behaviour illustrates the transition from a dry vapor system, corresponding to the high-temperature fumaroles, to a wet condensing system in the surrounding area. The results of this research, carried out on an active high-sulfidation system, provide a useful tool for the study of high-sulfidation epithermal ore deposits and particularly help to understand the alteration processes during the main stage of hypogene wall rock alteration. 相似文献
5.
Minerals that occur as incrustations in cooling lavas are formed by fractional condensation of volatile halides. Sulfates are of secondary origin formed during oxidation of the degassing volatiles. The trace metal compositions of the incrustations are controlled by the F/Cl ratio of the transporting gas phase rather than by element abundances in the silicate melt. The F/Cl ratio of the gas phase, inferred from incrustation mineral equilibria, indicates regional differences in the halogen contents of Icelandic magmas. The rift zone volcanism (tholeiites) is distinguished by low halogen content and very low F/Cl ratios, while the off-rift volcanism (alkaline rocks) is associated with high halogen content and high F/Cl ratios. 相似文献
6.
7.
Jessica L. Ball Eliza S. Calder Bernard E. Hubbard Marc L. Bernstein 《Bulletin of Volcanology》2013,75(1):1-18
A combination of field mapping, geochemistry, and remote sensing methods has been employed to determine the extent of hydrothermal alteration and assess the potential for failure at the Santiaguito lava dome complex, Guatemala. The 90-year-old complex of four lava domes has only experienced relatively small and infrequent dome collapses in the past, which were associated with lava extrusion. However, existing evidence of an active hydrothermal system coupled with intense seasonal precipitation also presents ideal conditions for instability related to weakened clay-rich edifice rocks. Mapping of the Santiaguito dome complex identified structural features related to dome growth dynamics, potential areas of weakness related to erosion, and locations of fumarole fields. X-ray diffraction and backscattered electron images taken with scanning electron microscopy of dacite and ash samples collected from around fumaroles revealed only minor clay films, and little evidence of alteration. Mineral mapping using ASTER and Hyperion satellite images, however, suggest low-temperature (<150 °C) silicic alteration on erosional surfaces of the domes, but not the type of pervasive acid-sulfate alteration implicated in collapses of other altered edifices. To evaluate the possibility of internal alteration, we re-examined existing aqueous geochemical data from dome-fed hot springs. The data indicate significant water–rock interaction, but the Na–Mg–K geoindicator suggests only a short water residence time, and δ18O/δD ratios show only minor shifts from the meteoric water line with little precipitation of secondary (alteration) minerals. Based on available data, hydrothermal alteration on the dome complex appears to be restricted to surficial deposits of hydrous silica, but the study has highlighted, importantly, that the 1902 eruption crater headwall of Santa María does show more advanced argillic alteration. We also cannot rule out the possibility of advanced alteration within the dome complex interior that is not accessible to the methods used here. It may therefore be prudent to employ geophysical methods to make further assessments in the future. 相似文献
8.
Mualla Cengiz Cinku Dieter Rammlmair Mümtaz Z. Hisarli Naci Orbay 《Studia Geophysica et Geodaetica》2009,53(4):475-494
Upper Cretaceous volcanic rocks were collected at 24 sites along the Pontides, N-NE Turkey, for rock magnetic and geochemical
studies. Rock magnetic and petrographic methods showed that the lavas are characterized predominantly by titanomagnetites
with a mixture of pseudo-single and multi-domain grains, whereas in tephrite single domain titanohematite was dominant. Measurements
of magnetic susceptibility and the geochemical properties on different volcanic rock types provide important knowledge about
the magnetic stability of the rocks. The magnetic properties are interpreted in terms of the composition, concentration, magma
generation. Tephrite and phonotephrites with the highest intensities (5200 mA/m) and high magnetic susceptibility values (2585
× 10−5), largest grain sizes and Fe/Ti values, showing minor or no alteration are the most magnetic stable samples in contrast to
dacites with the lowest intensity-magnetic susceptibility (520 mA/m − 573 × 10−5) and high alteration degree. The basanite samples show very low NRM (48–165 mA/m) but very high magnetic susceptibility (2906–3100
× 10−5) values suggesting the alteration of Fe-Ti minerals. It is shown that the magnetic properties of the basic to acidic rocks
show a systematic variation with magma differentiation and could be related to fractional crystallization. Major and trace
elements revealed that the lavas are compatible with complex magma evolution, with mineral phases of olivine+magnetite+clinopyroxene
in basic series, amphibole+ +clinopyroxene in intermediate rocks and plagioclase+clinopyroxene+biotite in acidic series. 相似文献
9.
Behaviour of rare earth elements during hydrothermal alteration at the Buena Esperanza copper-silver deposit, northern Chile 总被引：1，自引：0，他引：1
A study of the REE behaviour in alteration zones of the Buena Esperanza subvolcanic CuAg deposit, located in the Coastal Range of northern Chile, reveals that the elements are mobile in the rocks during alteration. The ore-forming process developed in three different stages of alteration-mineralization.
The hydrothermal alteration of the early and middle stages affected basaltic fragments of a breccia pipe. La and Ce were leached from the rock fragments located at the bottom and at the middle part of the breccia pipe and partly redeposited at the top during alteration. Sm, Eu and Tb were released selectively and the heavy REE behaved as relatively immobile elements. Sericite is the most important alteration mineral for fixing the REE during this stage. The incoming fluids had low REE contents.
The late stage of hydrothermal alteration happened simultaneously with the intrusion of a gabbroic volcanic neck, affecting mainly these subvolcanic rocks. REE patterns of samples from the top and bottom of the alteration zone exhibit roughly parallel trends, but are systematically enriched in REE in comparison to unaltered samples. This enrichment seems to be more intensive at the top of the altered area coinciding with the enrichment of Rb, K and Cu in these rocks. Epidote plays the most important role for fixing this hydrothermal input of REE during the latest stage of alteration. 相似文献
10.
Prior to the recent discovery of high-temperature vanadium sublimates at the fumaroles of Izalco volcano, El Salvador, the only vanadium minerals known were those formed at low-temperature surface conditions. Six new vanadium compounds have already been discovered at Izalco volcano, and five of these have been elevated to mineral status. Two of the minerals are among the most vanadium-rich compounds known in nature.Field studies and studies of the crystal chemistry of the sublimate phases have allowed delineation of the conditions of exsolution of vanadium-bearing gases from the magma and conditions of sublimation of the vanadium compounds. A vanadium halogen or oxyhalogen gas phase was exsolved from a basaltic magma when the magma was 550 m below the summit crater. As the gas rose to the fumaroles and mixed with the atmosphere, the oxygen fugacity rose from that of the magma to at least 10−3,5 bar. At the fumaroles, the vanadium compounds sublimated at various temperatures, but a minimum temperature of 760° can be determined for one of the phases based on geothermometry determined from phase relations in the system CuO-V2O5. The studies have demonstrated that a vanadium-bearing gas can segregate from a magma with normal basaltic concentrations of vanadium. 相似文献
11.
The spatial distribution of iron incrustations around an abandoned water well after 38 years of use was studied by analyzing the iron content of soil samples from 12 core borings. Three of these were performed inside the gravel pack, the rest at different distances in the adjacent aquifer. Incrustations had preferentially accumulated at the bottom of the screen coinciding with a zone of higher aquifer permeability. As expected, all cores from the annulus show buildup of iron oxides but the ones outside also showed elevated iron content up to 4 m away from the screen. Such distant incrustations are very difficult to remove, by mechanical or chemical methods. The common procedure of removing tubing and annulus material to install a new well at the same location could therefore give the replacement well a hydraulic disadvantage as the incrustations in the aquifer remain in place. 相似文献
12.
A reaction set of possible mineral weathering reactions is proposed to explain observed cation and silica export for the Emerald Lake watershed, a small Sierra Nevada, California catchment. The reaction set was calculated through a stoichiometric mole‐balance method, using a multiyear record of stream flow and snowpack chemical analyses and site‐specific mineral compositions. Reaction‐set calculations were intended to explore how the processes controlling stream cation and silica export depend on differing bedrock mineralogy across the catchment as snowmelt and runoff patterns change over the year. Different regions within the watershed can be differentiated by lake inflow subdrainages, each exhibiting different stream‐flow chemistry and calculated weathering stoichiometry, indicating that different silica and cation generation processes are dominant in wet steep portions of the catchment. Short‐term differences in stream concentrations were assumed to reflect ion exchange equilibria and rapid biological processes, whereas long‐term persistent stream concentration differences in different areas of the catchment were assumed to reflect spatial variability in mineral weathering stoichiometry. Mineralogical analyses of rock samples from the watershed provided site‐specific chemical compositions of major mineral species for reaction calculations. Reaction sets were evaluated by linear regression of calculated versus observed differences between snowmelt and stream‐flow chemistry and by a combined measure. Initially, single weathering reactions were balanced and evaluated to determine the reactions that best explained observed stream chemical export. Next, reactions were combined, using mineral compositions from different rock types to estimate the dependence of ion fluxes on lithology. The seasonal variability of major solute calculated fluxes is low, approximately one order of magnitude, relative to the observed three orders of magnitude variability in basin discharge. Reaction sets using basin‐averaged lithology and Aplite lithologies gave superior explanations of stream chemical composition. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
Previous studies have shown how biogenic silica particles undergo conversion to aluminosilicate phases in large tropical deltaic systems, thus affecting the world ocean budget of major seawater cations. This study tackles the important question of the silica budget in the coastal zone of the Mississippi River Delta, providing evidence for the role of biogenic silica diagenesis in this subtropical system from direct examination of individual diatom particles, sediment leachates and pore-water composition. The estimated reactive silica stored in the study area (5990 km2) is based on operational leaches that account for altered biogenic silica particles and other authigenic aluminosilicate phases in addition to fresh biogenic silica. Early diagenesis of silica in the delta front occurs mainly where more siliceous material is deposited. An inner-shelf area, where hypoxic conditions are found, significantly contributes to the formation of authigenic products of Si alteration. Data suggest that the limiting factor of silica alteration processes is the availability of detrital phases such as Al and Fe. The estimated total reactive silica accumulation in the study area is 1.45×1010 mol Si year−1, representing ∼2.2% of the long-term bulk sediment accumulation. On the basis of a conservative appraisal, the authigenic mineral components account for ∼40% of the long-term reactive silica storage. This study shows that non-tropical deltaic systems are significantly more important sinks of silica than previously thought and that, where conditions are favourable, a consistent portion of reactive silica not leaving the shelf is stored within the delta in the form of authigenic components. 相似文献
14.
《Journal of Volcanology and Geothermal Research》1988,35(3):227-235
Sulfur isotope ratios were measured in eight lava incrustations and three volcanic gas samples and their corresponding lava flows. The lava incrustations of sulfate composition are from five recent eruptions and occur as thenardite or as aphtitalite-thenardite mixtures, with abundant trace elements. The incrustations show small sulfur isotope fractionation of 1–2‰ compared with corresponding lavas and the volcanic gas samples. The sulfate incrustations are formed through oxidation of SO2 from the emitted volcanic gas and subsequent reaction with metal halides. The volcanic gas samples show a distribution of decreasing δ34S through time from +3.4 to −1.8‰; sulfate was preferentially degassed compared to sulfide. The data indicate that sulfate incrustations serve as a late-stage volcanic gas sample with respect to sulfur isotopes. 相似文献
15.
Previous research on rock weathering crusts has revealed their large variability depending on the type of host rocks and development of weathering processes. The composition of crusts developed on natural sandstone exposures is less documented in the literature in comparison to those developed on architectonic stones. In both cases, previous research has focused mainly on the progress of salt weathering. This study considers the surfaces of sandstone tors in the Polish Outer Carpathians. The exposed parts of the rocks in this area are often covered by crust, which is up to several centimetres thick, and differs from the internal part in colour and composition. The crusts were characterized using light and electron microscopy, X‐ray diffractometry, thermal analyses, Mössbauer spectroscopy, bulk chemical analyses and sequential chemical extractions. Porosity was estimated by digital image processing. The following two hardened zones were observed: (1) thin (up to 30 µm), black, external layer, rich in carbon and composed of opal‐type silica, covered in places by sulphate incrustations and numerous spherical particles of anthropogenic origin; (2) thicker (up to several millimetres), internal part composed of a set of laminae of variable colouration, enriched in iron (oxyhydr)oxides (goethite and hematite) in comparison to the rock interior. Development of the crust results from silicon and iron redistribution during the sandstone alteration. The chief source of silica is hydrolysis of aluminosilicates, whilst that of iron is decomposition of aluminosilicates, carbonates and sulphides. Hematite is probably a result of goethite transformation. However, air pollutants may play an important role in the formation of sulphates. Silica and iron compounds affect the properties of the rock, hardening the surface and lowering porosity by formation of secondary cement. Crystallization of sulphate salts, in turn, may contribute to mechanical disintegration of the rock. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
More attention has been paid to the formation conditions of petroleum and gas[1,2]. It is gen-erally accepted that various types of organic materials have served as the most important source of petroleum and gas in sediments. The formation of hydrocarbons… 相似文献
17.
Shinya Oana 《Bulletin of Volcanology》1962,24(1):49-57
Volcanic gases from Showashinzan are qualitatively the same as those liberated from igneous rocks when they are heated in vacuum. Their main components are H2O, CO2, and H2. Then follow HCl, HF, N2, SO2, H2S, S, CH4, CO, Ar, Si, B, Mg, Na, K, Ca, Al, Fe, P, Br, NH3, As, Zn, Sr, Ba, Cu, Pb, Sn, Sb, Bi, Ge, Ag, Cr, Ni, Mo, Rn, Ra, etc. They come through fumaroles of high temperature (～750°C.). Metallic compounds deposit as sublimates around the outlet of fumaroles. They are fractionated there according to their thermodynamic properties. When the temperature of gases falls, heavy metal elements deposit before reaching the surface of the earth. Ra is among them. Owing to the contribution of Ra thus depositted, Rn content of vapor is larger in low temperature fumaroles than in high temperature ones. Chemical compounds of H, C, N, O, and S vary their composition according to the condition of temperature and pressure. Sulfur exists as SO2 more than H2S. As the temperature of gases falls, SO2 and H2 decrease and H2S increases. Mutual relation among them is ruled by the chemical equilibrium: SO2+3H2=H2S+2H2O. The structure of Showashinzan is not simple. Some deviations from the general rule are explained in connection with ground water. 相似文献
18.
This study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in Ghana. Q‐mode hierarchical cluster analysis (HCA) was applied to 57 hydrochemical data from the Buem formation in the northern part of the Volta Region in Ghana. R‐mode HCA and R‐mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation. Results of both the Q‐ and R‐mode analyses were backed by graphical methods. The analyses revealed two major water types, differentiated by salinity levels into four spatial groundwater associations. The characteristics of the four groundwater types are discussed. The recharge areas are characterized by Ca? HCO3 low salinity waters which evolve through rock–water interactions to Na? HCO3 high salinity waters in the discharge areas. This study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals, principally silicates in the aquifer matrix. The effects of the chemistry of recharging precipitation are higher in the recharge areas, while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime. All the four spatial groundwater associations have low sodium content, but salinity levels increase towards the discharge areas, such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
19.
The partitioning of major and minor elements between augite and melt was determined as a function of cooling rate for two high-titanium basalt compositions. The results of this study of lunar rock systems 10017 and 75055 were compared with the results of other kinetic studies of augite-liquid partitioning in other rock systems. It was found that the partitioning of major elements (i.e., Ca, Fe, Mg) is essentially rate independent and is insensitive to bulk rock composition and to the nature and order of appearance of coexisting phases for cooling rates of less than 100°C/hr. The partitioning behavior of minor elements (i.e., Al, Cr, Ti) for the same range of cooling rates is complex, being dependent on cooling rate and bulk rock composition. Consideration of these factors is important when augite chemistry and/or partitioning behavior are used in modeling certain magmatic processes or in estimating the thermal history of basaltic rocks. 相似文献
20.
Odin D. Christensen Regina A. Capuano Joseph N. Moore 《Journal of Volcanology and Geothermal Research》1983,16(1-2)
Chemical interaction of thermal fluids with reservoir rock in the Roosevelt Hot Springs thermal area, Utah, has resulted in the development of characteristic trace-element dispersion patterns. Multielement analyses of surface rock samples, soil samples and drill cuttings from deep exploration wells provide a three-dimensional perspective of chemical redistribution within this structurally-controlled hot-water geothermal system.Five distinctive elemental suites of chemical enrichment are recognized, each characteristic of a particular combination of physical and chemical conditions within the geothermal system. These are: (1) concentrations of As, Sb, Be, and Hg associated with siliceous material at locations of liquid discharge, fluid mixing or boiling; (2) concentrations of Mn, Ba, W, Be, Cu, Co, As, Sb and Hg in manganese and iron oxide deposits; (3) high concentrations of Hg in argillized rock near fumaroles and lower concentrations in a broad diffuse halo surrounding the thermal center; (4) concentrations of As in sulfides and Li in silicate alteration minerals immediately surrounding high-temperature fluid flow-controlling fractures; (5) deposits of CaCO3 at depth where flashing of brine to steam has occurred due to pressure release. The geochemical enrichments are not, in general, widespread, pervasively developed zones of regular form and dimension as are typical in many ore-forming hydrothermal systems.As the geothermal system develops, changes and eventually declines through time, the chemical deposits are developed, remobilized or superimposed upon each other, thus preserving within the rocks a record of the history of the geothermal system. Recognition of trace-element distribution patterns during the exploration of a geothermal system may aid definition of the present geometry and interpretation of the history of the system. 相似文献