共查询到20条相似文献,搜索用时 78 毫秒
1.
Received: 24 May 1999 · Accepted: 19 July 1999 相似文献
2.
R. Scherreiks 《International Journal of Earth Sciences》2000,89(1):90-107
Received: 25 June 1999 / Accepted: 30 November 1999 相似文献
3.
Received: 19 April 1999 · Accepted: 19 July 1999 相似文献
4.
Received: 3 May 1999 · Accepted: 13 July 1999 相似文献
5.
Received: 10 May 1999 / Accepted: 16 October 1999 相似文献
6.
A. Aydin 《Environmental Geology》2001,40(6):672-677
This review focuses on studies of flow, transport and deformation processes at a scale of a single discontinuity. The paper
provides an evaluation of: (1) various methods suggested for geometrical characterization of void structure; and (2) theoretical
and practical problems arising from significant differences between the actual geometry of fracture void structure and its
parallel plate representation. The use of an equivalent aperture concept is shown to be seriously misleading in: (a) evaluation
of flow regime, and hence selection of appropriate flow laws; (b) correlating tracer and hydraulic tests, and assessment of
solute transport properties; and (c) relating hydraulic and mechanical apertures, and predicting influence of stress perturbation
and deformability.
Received: 2 August 1999 · Accepted: 30 November 1999 相似文献
7.
新疆巴里坤县三塘湖北卡拉岗组火山岩特征 总被引:6,自引:0,他引:6
新疆东准噶尔巴里坤县三塘湖盆地以北老爷庙额仁山一带,广泛分布一套红色、红褐、黄色酸性火山岩,前人(1:20万)将其归为下石炭统黑山头组(C1h)和中一上石炭统哈尔加乌组(C2~P1h),1999-2001年在这一带开展1:5万区调时发现,这一套火山岩不整合于下伏地层之上,从而将火山岩从老爷庙组(D3l),黑山头组和哈尔加乌组中解体出来,划归为卡拉岗组(P1k),为一套陆相酸性火山岩.以喷溢相流纹岩、霏细岩为主,是造山后弛张期大陆板内火山岩,时代为早二叠世. 相似文献
8.
A. Pulido-Bosch P. Pulido-Leboeuf L. Molina-Sánchez A. Vallejos W. Martin-Rosales 《Environmental Geology》2000,40(1-2):163-168
The intensive agricultural activities that have developed over the last 50 years in the Campo de Dalias (Almeria region)
have required large quantities of gravel and clay as the basic materials for the substrate over which crops are raised. With
this motive, numerous gravel pits have been opened that have extracted several million cubic metres of material in recent
years. Similar quantities of clay have been extracted from the distal sectors of the alluvial fans that descend from the Sierra
de Gador, and from within a large endoreic basin. In the latter quarries, some wetlands have developed, probably because of
the rise in the water-table level in the aquifer over which they lie. The gravel pits are situated in the apical sectors of
the alluvial fans, overlying hydrogeological units that are widely overexploited. For this reason the gravel pits could be
used for artificial recharge; in addition to increasing the availability of water in the aquifer, the risk of catastrophic
flooding would also be reduced.
Revision received: 19 November 1999 · Accepted: 28 December 1999 相似文献
9.
Tidal freshwater marshes exist at the interface between watersheds and estuaries, and thus may serve as critical buffers
protecting estuaries from anthropogenic metal pollution. Bi-weekly samples of newly deposited marsh sediments were collected
and analyzed for Cu, Zn, and Fe concentrations over 21 months from July 1995 to March 1997 in five distinct habitats at the
head of Bush River, Maryland. Bi-weekly anthropogenic metal enrichments ranged from 0.9–4.7. Anthropogenic excess metal loadings
averaged over 1996 ranged from 6–306 and 25–1302 μg cm−2 year−1 between sites for Cu and Zn, respectively. Based on Fe-normalized trace metal signatures, Susquehanna River sediment does
not significantly contribute to upper Bush River. Organic matter was found to dilute total metal concentrations, whereas past
studies suggested organics enhance labile metal content. Analysis of metal input pathways shows that marsh metals are primarily
imported from nearby subtidal accumulations of historic watershed material by tidal flushing.
Received: 29 April 1999 / Accepted: 7 December 1999 相似文献
10.
V. P. Parnachev D. Banks A. Y. Berezovsky D. Garbe-Schönberg 《Hydrogeology Journal》1999,7(6):546-560
The Shira region of Khakassia in southern Siberia exhibits many features governing the evolution of groundwater and surface-water
chemistry that are common to other cold, semi-arid areas of the world: (1) a continental climate, (2) location in a rain shadow,
(3) low density of surface-water drainage, (4) occurrence of saline lakes, and (5) occurrence of palaeo- and modern evaporite
mineralisation. In lowland areas of Shira, the more saline groundwaters and lake waters have a sodium-sulphate (-chloride)
composition. Results of thermodynamic modelling suggest that these evolve by a combination of silicate weathering and gypsum
and halite dissolution, coupled with carbonate precipitation to remove calcium and bicarbonate ions. An approximately 1:1
sodium:sulphate ratio occurs even in groundwaters from non-evaporite-bearing aquifers. This may indicate the formation of
secondary sodium sulphate evaporites (in or near saline lakes or in soil profiles where the water table is shallow), which
are subsequently distributed throughout the study area by atmospheric transport. Several urban groundwaters are characterised
by very high nitrate concentrations, conceivably derived from sewage/latrine leakage.
Received, June 1998 /Revised, May 1999, August 1999 /Accepted, August 1999 相似文献
11.
Colour origin of upper cretaceous pelagic red sediments within the Eastern Pontides, northeast Turkey 总被引:3,自引:0,他引:3
Characteristic samples of Upper Cretaceous pelagic red sediments from different parts of the Eastern Pontides (NE Turkey)
have been investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy coupled with
energy dispersive analyses (SEM/EDAX). The red sediments are composed of limestone and muddy limestone, and characterized
by abundant planktonic foraminifers. Hematite content ranges from 0.5 to 3.0 wt.%. Electron microscope observations suggest
that the hematite pigment has a diagenetic origin. The red colour is due to presence of hematite pigment, and indicates oxidizing
conditions during early diagenesis in a relatively deep marine environment.
Received: 4 January 1999 / Accepted: 8 July 1999 相似文献
12.
The assessment of the aluminosilicate buffering potential during acid weathering of the Estonian alum shale is provided.
It is found that the stoichiometric interaction between dissolved pyrite oxidation products and illite of the shale best describe
the buffering process and are consistent with earlier field studies. The scheme includes incongruent dissolution of illite
with smectite and K-jarosite precipitating. This complex mechanism involves buffering of 8% of the acidity by K+ and temporary precipitation of 25% of the acidity as K-jarosite. Dissolution proceeds at a low pH (1.5–3) until all pyrite
in the shale particle is oxidised. Hence, if the total amount of illite present is larger than needed for stoichiometric interactions,
only part of it is involved in a buffering process, neutralising a certain percentage of acidity. The next stage in shale
weathering is the incongruent dissolution of K-jarosite with the release of the precipitated acidity and the formation of
ferric oxyhydroxide.
Received: 3 August 1998 · Revised paper: 26 January 1999 · Accepted: 23 February 1999 相似文献
13.
Received: 23 March 1999 / Accepted: 25 August 1999 相似文献
14.
M. Friberg A. Larionov G. A. Petrov D. G. Gee 《International Journal of Earth Sciences》2000,89(1):21-39
Received: 7 May 1999 / Accepted: 2 November 1999 相似文献
15.
J. F. W. Bowles 《Mineralium Deposita》2000,35(6):583-586
The primary source of the alluvial platinum-group minerals (PGM) of the Freetown Layered Intrusion, Sierra Leone, has been
unknown since their discovery 70 years ago. This is a report on work in progress to establish a primary occurrence related
to the igneous layering. New whole-rock major and minor element analyses and precious metal assays show that at key horizons
there is a significant change in the silicate mineral compositions and in Cu, Cr and Ni, as well as in Pt and Pd, comparable
to those encountered in other PGM-bearing layered intrusions. Anomalous (0.1 to 0.4 g/t) Pt levels occur in pyroxene troctolites,
which maintain these levels along strike.
Received: 30 July 1999 / Accepted: 2 December 1999 相似文献
16.
This study evaluates the geological, hydrogeological and hydrological conditions at the open waste dump site of the Van municipality
in eastern Anatolia, Turkey. A geological map and a three-dimensional view of the project site have been prepared. All lithological
units exposed at and near the dump site have been determined and their boundary relationships identified. Drainage basin characteristics
of the dump site along with the water bearing properties of different lithological units have been assessed. For the rehabilitation
of the existing dump site, material availability (clay as a liner, cap, and daily cover material; granular soil as a filter
material) has been researched. Based on the geological, hydrogeological, morphological and hydrological conditions of the
existing waste dump site, recommendations to minimize its environmental impact are presented.
Received: 8 March 1999 · Accepted: 3 May 1999 相似文献
17.
Environmental mercury and arsenic sources in fossil hydrothermal systems, Northland, New Zealand 总被引:2,自引:0,他引:2
Northland, New Zealand has been affected by natural hot water spring systems depositing elevated concentrations of mercury
and arsenic over the past 5 million years. Due to the different erosion levels of these hot water systems, four principal
types of mercury and arsenic occurrences are found: active hot springs; layered surface deposits (sinters) deposited by hot
springs; highly fractured rock zones formed immediately beneath hot springs; and chemically altered and mineralized rock from
the deeper roots of hot spring systems. Mercury occurs principally as cinnabar and as a minor impurity (<1 wt%) in phosphate
minerals and iron sulfides, particularly marcasite. Mercury is irregularly distributed through limonitic cements formed during
oxidation. Arsenic occurs as a minor impurity (<1 wt%) in phosphate minerals and iron sulfides, particularly marcasite. Arsenic
is also variably dispersed through limonite, but not necessarily with mercury. Decomposition of marcasite constitutes the
most significant source of mercury and arsenic pollution from the studied sites. Release of mercury and arsenic into the environment
from marcasite, phosphates and limonite is enhanced by acidification of the sites (down to pH of 2), caused by oxidation of
iron sulfides. Mercury and arsenic concentrations of up to 100 parts per billion should be expected in waters near the deposits;
these concentrations are in excess of recommended drinking water levels.
Received: 9 April 1999 · Accepted: 2 August 1999 相似文献
18.
The results of a temperature-dependent electron diffraction study of the low frequency modes of distortion of Ba-hexacelsian
and their relationship to the α-β polymorphic phase transition therein are presented. Cs- and Rb-doped Ba-hexacelsian specimens
are also investigated. An extremely strong and characteristic diffuse intensity distribution in the form of polarized sheets
of diffuse intensity perpendicular to the <1 1 0> directions is found for the high temperature polymorph and the doped specimens.
The diffuse distribution appears to result from coupled tetrahedral rotation of <1 1 0> columns of corner-connected (Al,Si)O4 tetrahedra about the [0 0 1] axis (uncorrelated from column to column as a result of the positioning of the rotation axes).
Received: 25 January 1999 / Revised, accepted: 13 July 1999 相似文献
19.
Hydrochemical evolution and environmental features of Salso River catchment, central Sicily (Italy) 总被引:2,自引:0,他引:2
A hydrogeochemical study of the Salso River highlighted the chemical and isotopic space-time evolution along its flow path
and the main contamination processes. Within the basin, three different hydrogeochemical facies have been individuated: (1)
Ca-Mg-HCO3, (2) Ca-Mg-SO4 and (3) Na-Cl. The first facies reflects the chemical composition of the groundwaters hosted in the carbonate reliefs that
belong to the Madonie Mountains. The second and the third facies are the result of the interaction processes between surface
waters and the gypsum and salty clays, respectively. Two pollution sources have been also located in the basin downstream
from the salt mine and downstream from a discharge area of wastewater from the town of Gangi. On the basis of the location
of natural and anthropogenic pollution sources, the waters available for drinking and irrigation use are also indicated.
Received: 16 July 1999 · Accepted: 22 December 1999 相似文献
20.
Platinum-group elements in Cu-sulphide ores at Carolusberg and East Okiep, Namaqualand, South Africa 总被引:1,自引:0,他引:1
W. D. Maier 《Mineralium Deposita》2000,35(5):422-429
Cu-sulphide ores at Carolusberg and East Okiep have Cu/Ni ratios of up to 80, an order of magnitude higher than most magmatic
sulphide ores elsewhere. In contrast, Se/S ratios (500–1700 × 10−6) and PGE tenors (up to 5 ppm) of the sulphides are in the range of more typical magmatic sulphide ores. The observed metal
patterns may be explained by a process of monosulphide solid solution (mss) fractionation of a magmatic sulphide melt at depth,
but this model is currently considered unlikely, due to the paucity of refractory ores in the district. Assimilation of Cu-rich
country rocks during ascent of the Koperberg magmas proved difficult to test with the available data, but this provides no
explanation for the common high-grade metamorphic setting of similar ores elsewhere. A restitic origin of the pyroxenites
appears to explain many of the observed ore features and is presently favoured here. Desulphidization of a primary magmatic
sulphide ore could not have yielded the observed metal patterns and is therefore considered to be of relatively minor importance
in ore genesis.
Received: 12 April 1999 / Accepted: 27 November 1999 相似文献