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61.
The Tres Marias carbonate-hosted Zn–Ge deposit in Chihuahua, Mexico contains sphalerite with the highest average Ge (960 ppm)
and willemite with the highest reported Ge contents of Mississippi-Valley-type (MVT) deposits worldwide. This has prompted
current exploration efforts to focus on the deposit as a high-grade source of germanium. The sulfide-rich ore type (>125,000 t
at 20% Zn and 250 g/t Ge) contains Fe-rich botryoidal sphalerite (type I) associated with solid hydrocarbons. This type exhibits
distinctive intimately intergrown lamellar texture of high-Fe sphalerite (average 9.9 wt.% Fe and 800 ppm Ge) and a somewhat
less Fe-rich sphalerite phase (average 5.5 wt.% Fe and 470 ppm Ge). Reddish-brown banded sphalerite (type II, average 5.7 wt.%
Fe and 1,320 ppm Ge) is subordinately followed by galena and pyrite. The sulfide-poor “oxidized” zinc ore (up to 50 wt.% Zn;
250 to 300 ppm Ge) is a fine-grained, often friable, alteration product of the sulfide ore and associated limestone and breccia
host. While some areas are dominated by carbonates and sulfates, others are enriched in silicates such as hemimorphite and
willemite. The gangue assemblage includes goethite, hematite, and amorphous silica or quartz. Minor wulfenite, greenockite,
cinnabar, and descloizite also occur. Willemite occurs as interstitial replacement of sphalerite and fracture fillings in
the oxidized ore and can be unusually rich in Pb (up to 2.0 wt.%) and Ge (up to 4,000 ppm). Oscillatory zonation reflects
trace element incorporation into willemite from the oxidation of primary Ge-bearing sphalerite and galena by siliceous aqueous
fluids. The Tres Marias deposit has hybrid characteristics consisting of a primary low-temperature MVT Ge-rich Zn–Pb sulfide
ore body, overprinted by Ge-rich hemimorphite, willemite, and Fe oxide mineralization. 相似文献
62.
Marcin Frankowski Anetta Zioła-Frankowska Artur Kowalski Jerzy Siepak 《Environmental Earth Sciences》2010,60(6):1165-1178
The study presents the results of Cu, Pb, Zn, Mn and Fe determination in the samples of bottom sediments collected from the
Oder and Warta rivers. The sequential extraction of metals in the samples of bottom sediments was performed after introducing
the modification of the extraction scheme suggested by Tessier et al. (Anal Chem 51(7):844–851, 1979). The extraction times
of particular stages were optimised. The fifth stage was altered by introducing the new methods of performing extraction.
The samples of bottom sediments submitted the following granulometric analyses: dry, wet and wet with (HMP) dispersing reagent.
Seven granulometric fractions with the following grain sizes were isolated: >2.0, 2.0–1.0, 1.0–0.5, 0.5–0.25, 0.25–0.1, 0.1–0.063
and <0.063 mm. The sequential extraction of particular granulometric fractions was performed. The concentration of metals
variability was analysed depending on the method of sample preparation for the chemical analysis, granulometric fraction of
sediments subjected to the analysis, extraction conditions and the site of samples collection. The lack of linearity between
the metal concentration and the size of granulometric fraction was observed. The highest concentrations of metals were observed
in fractions >2.0, 2.0–1.0 and 0.1–0.063 and <0.063 mm while the lowest concentrations occurred in fractions 1.0–0.5, 0.5–0.25,
and 0.25–0.1 mm. The atomic absorption spectrometry with flame atomisation (F-AAS) was used for the determination of the investigated
elements. 相似文献
63.
Saline seepage zone development and hence dryland salinity is a major environmental problem which many arid to semiarid landscapes in Australia are experiencing. Due to the geological complexity of the regional aquifer system and the heterogeneous nature of the local groundwater system, each groundwater seepage zone in the Spicers Creek catchment, central west, New South Wales, Australia possesses different mechanisms which control its development. Saline seepage zones have formed adjacent to a fault zone, and two experimental sites were established through these groundwater discharge zones to understand geochemical processes which have led to the development of soil sodicity, gully erosion and the flushing of salts into the surface water systems. Seepage zone groundwaters contain a distinctive geochemical signature with elevated concentrations of Na, Cl, HCO3, Ca, Sr, B, As and Li. The mixing of deep saline groundwaters together with ion exchange processes lead to a distinctive seepage zone groundwater chemistry being developed. Altering the landscape features within this rural groundwater system has developed water toxicity for crops, soil sodicity leading to land degradation, and waterlogging problems. 相似文献
64.
Jerzy Ladysz 《GeoJournal》2006,67(1):1-7
The shift to market forces in Poland, East Germany and Czech Republic has fundamentally reconfigured its economic geography. In particular, spatial inequalities between neighboring Polish, Czech and German border regions have re-emerged forcefully in response to new values, expectations and preferences. In this paper the example of coal mines illustrates the potency of spatial planning. The abundance of coal mines in the Polish, Czech and German borderland at or near abandonment and their proximity to ecological corridors make them candidates for renewed uses in industry or conservation. Attention will also be given to the main environmental problems caused by wrongly conducted spatial policy on this borderland. Transforming a landscape requires continuation of guidance and financial assistance of the European Union. 相似文献
65.
Martin Rosner Lary Ball Bernhard Peucker-Ehrenbrink Jerzy Blusztajn Wolfgang Bach Jörg Erzinger 《Geostandards and Geoanalytical Research》2007,31(2):77-88
We report a new approach to conduct fast and accurate lithium isotope ratio measurements by MC-ICP mass spectrometry after wet chemical sample preparation. In contrast to most previously published methods our MC-ICP-MS set-up did not use a desolvating system to achieve appropriate ion beam intensities and, therefore, was less affected by matrix-induced shifts of the instrumental mass bias. As the total lithium background and build-up in the sample introduction system was low, previous sample residues could be washed out by an extended uptake of the new sample. Elimination of a nitric acid rinse step increased the sample throughput by a factor of two and allowed the instrumental mass bias drift to be tracked more precisely. δ7 Li values of powdered silicate rock reference materials and seawater obtained in this study revealed good accuracy and an overall analytical uncertainty of typically 0.5‰ (2s). On the basis of a comparison between our lithium isotope data and compiled literature data, we recommend preliminary average δ7 Li values for seawater (+30.8‰) and several silicate rock reference materials (BHVO-1: +5.0‰; JA-1: +5.6‰; JB-2: +4.8‰). The compilation of published δ7 Li values for seawater suggests that the observed large lithium isotope differences are due to inter-method and/or interlaboratory bias. Most recently published δ7 Li values for seawater show little variation and confirm a constant lithium isotope composition (at the sub ‰ level) of seawater in well mixed ocean basins. 相似文献
66.
A large groundwater system in the Amadeus Basin, central Australia, discharges to a chain of playa lakes 500 km long. The playas contain highly concentrated brines; these are sodium-chloride rich waters with appreciable magnesium and sulphate and very low concentrations of calcium and bicarbonate. Gypsum, glauberite, and other evaporite minerals are precipitating in the playas. The groundwaters evolve to brine by concurrent processes of dissolution, evaporative concentration, mineral precipitation, and mineralogical change. Chemical evolution is considered with reference to a concentration factor based on chloride. Ion transfer calculations demonstrate losses of magnesium and bicarbonate throughout, as a result of precipitation. Sodium, potassium, calcium, and sulphate are gained initially as a result of dissolution but lost subsequently as a result of precipitation. Larger playas in the chain, exemplified by Lake Amadeus, have dual shallow and deep groundwater flow paths whereas the smaller playas, exemplified by Spring Lake, have only shallow flow paths. Brines in the larger playas are diluted by deep groundwaters and this is reflected in the degree of saturation attained with respect to particular minerals. Thus, saturation with respect to gypsum and glauberite is attained earlier in Spring Lake than in Lake Amadeus. Saturation with respect to halite is attained in Spring Lake but not in Lake Amadeus. Both playas are undersaturated with respect to hexahydrite and sylvite although these minerals occur in efflorescent crusts in Spring Lake. 相似文献
67.
68.
David Gubbins Peter Molnar J. G. Olliver Petr Vanīček Kenji Satake Allan M. Rubin Waclaw M. Zuberek Janusz Niewiadomski Leszek Czechowski David J. Steveson Jacek Leliwa-Kopystyński Yu. N. Korenkov Fred Lipschultz Marek Jerczyński Krzysztof E. Haman Jerzy Radziwill Maciej Sadowski Maciej Sadowski 《Pure and Applied Geophysics》1990,132(3):599-637
69.
Jerzy Jankowski Antoni Szymański Karel Pěč Václav Červ Václav Petr Jana Pěčová Oldřich Praus Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1977,21(1):35-57
nuam mam uu auauaum n aumua ¶rt; a 9 n mau ¶rt; nu No V, na anam. ma uam a aa u¶rt;uu aau ¶rt; uu u mau anamau. m m u¶rt;uu u aauuaa amma aamumua aa ma. ¶rt;a a m¶rt; mau ¶rt; aumua u mm a¶rt;u n a m u mau. uamua aau ¶rt;m u mu ma, m m ¶rt;u u umu m n. maum aamumuu n nma mmuuu aauu aumau ¶rt; m ¶rt;- ¶rt;¶rt;muu mm ¶rt; nu u m¶rt; am.
A substantial part of this paper was presented at the IAGA symposium Relations between External and Internal Magnetic Variations, XVI. IUGG General Assembly, August–September 1975, Grenoble. 相似文献
A substantial part of this paper was presented at the IAGA symposium Relations between External and Internal Magnetic Variations, XVI. IUGG General Assembly, August–September 1975, Grenoble. 相似文献
70.