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81.
82.
Our knowledge of the lithosphere beneath the Carpathian–Pannonian Region (CPR) has been greatly improved through petrologic, geochemical and isotopic studies of upper mantle xenoliths hosted by Neogene–Quaternary alkali basalts. These basalts occur at the edge of the Intra-Carpathian Basin System (Styrian Basin, Nógrád-Gömör and Eastern Transylvanian Basin) and its central portion (Little Hungarian Plain, Bakony-Balaton Highland).The xenoliths are mostly spinel lherzolites, accompanied by subordinate pyroxenites, websterites, wehrlites, harzburgites and dunites. The peridotites represent residual mantle material showing textural and geochemical evidence for a complex history of melting and recrystallization, irrespective of location within the region. The lithospheric mantle is more deformed in the center of the studied area than towards the edges. The deformation may be attributed to a combination of extension and asthenospheric upwelling in the late Tertiary, which strongly affected the central part of CPR subcontinental lithosphere.The peridotite xenoliths studied show bulk compositions in the following range: 35–48 wt.% MgO, 0.5–4.0 wt.% CaO and 0.2–4.5 wt.% Al2O3 with no significant differences in regard to their geographical location. On the other hand, mineral compositions, particularly of clinopyroxene, vary according to xenolith texture. Clinopyroxenes from less deformed xenoliths show higher contents of ‘basaltic’ major elements compared to the more deformed xenoliths. However, clinopyroxenes in more deformed xenoliths are relatively enriched in strongly incompatible trace elements such as light rare earth elements (LREE).Modal metasomatic products occur as both hydrous phases, including pargasitic and kearsutitic amphiboles and minor phlogopitic micas, and anhydrous phases — mostly clinopyroxene and orthopyroxene. Vein material is dominated by the two latter phases but may also include amphibole. Amphibole mostly occurs as interstitial phases, however, and is more common than phlogopite. Most metasomatized peridotites show chemical and (sometimes) textural evidence for re-equilibration between metasomatic and non-metasomatic phases. However, amphiboles in pyroxenites are sometimes enriched in K, Fe and LREE. The presence of partially crystallized melt pockets (related to amphiboles and clinopyroxenes) in both peridotites and pyroxenites is an indication of decompression melting and, rarely, incipient partial melting triggered by migrating hydrous melts or fluids. Metasomatic contaminants may be ascribed to contemporaneous subduction beneath the Carpathian–Pannonian Region between the Eocene and Miocene.Sulfide inclusions are more abundant in protogranular and porphyroclastic xenoliths relative to equigranular types. In mantle lithologies, sulfide bleb compositions vary between pentlandite and pyrrhotite correlating with the chemistry and texture of the host xenoliths. While sulfides in peridotites are relatively rich in Ni, those in clinopyroxene-rich xenoliths are notably Fe-rich. 相似文献
83.
Mineralogical and chemical characterization of wastes from the sulfuric acid industry in Falun, Sweden 总被引:2,自引:0,他引:2
Z. Lin 《Environmental Geology》1997,30(3-4):152-162
Wastes from the sulfuric acid industry are an environmental concern, because of the emission of acids, heavy metals, and
sulfate to the environment. The wastes in Falun consist of 70–80% iron oxides, 10–20% silicates, less than 10% residual sulfides,
and small amounts of secondary precipitates (iron hydroxides and Fe-, Zn- and Cu-sulfates). Due to the different behavior
of sulfides during the roasting process, pyrrhotite and sphalerite are the major sulfide residues associated with lesser amounts
of pyrite, chalcopyrite, and galena. The leachates are low-pH and enriched in Zn, Fe, and SO4. The acid ferric Fe-rich solution promotes the dissolution of sphalerite and favors the formation of Pb-sulfate coatings
on galena, providing an armoring effect which slows down the further oxidation of the galena. The residual sulfides are the
potential source for acid generation and metal release. During the roasting process, iron oxides retain small amounts of sulfur
and sphalerite forms alteration rims containing Zn-oxides. The iron oxides and Zn-oxides are important contributors to SO4 and Zn in the leachates. The conditions in the waste deposit are favorable for the precipitation of Zn-, Cu-Fe-sulfates (e.g.
gunningite, chalcanthite, Zn-copiapite). The highly soluble sulfates play important roles in controlling the concentrations
of Cd, Cu, Fe, Zn, and SO4 in the leachates. The mineralogical and geochemical data help to develop the reclamation strategies of this type of industrial
wastes.
Received: 26 April 1996 · Accepted: 27 July 1996 相似文献
84.
Victor Kress Lori E. Greene Matthew D. Ortiz Luke Mioduszewski 《Contributions to Mineralogy and Petrology》2008,156(6):785-797
We present the results of a series of density experiments in the system O–S–Fe–Ni–Cu. These experiments were designed to extend
our understanding of the physical properties of sulfide liquids, and to extend one-bar thermochemical models for sulfide liquids
to apply to low to moderate pressures. Density measurements indicate both positive and negative deviations from linear mixing
of partial molar volumes across this five-dimensional composition space. In terms of the homogeneous speciation model of Kress
(in Contrib Mineral Petrol 154:191–204, 2007), the best fit to experimental data can be achieved by starting with a model
where the volume of formation reaction for associated species initially is set to zero. Further refinement of this first-order
fit yields a volume mixing model which reproduces experimental data to within nearly the estimated experimental uncertainty.
Experimental ultrasonic and X-ray absorption data from the literature, along with the bulk modulus–volume relation of Anderson
and Nafe (J Geophys Res 16:3951–3963, 1965), allow the estimation of the pressure dependence of partial molar volumes for
sulfide liquid species. The resulting combined thermochemical model should be valid to about 2,000 K and 3 GPa. Application
of this thermochemical model in a simple adiabatic magma ascent scenario confirms earlier work suggesting that the pressure
dependence of sulfur solubility in sulfide-saturated magma will decrease with increasing pressure along geologically reasonable
paths in P–T–– space. 相似文献
85.
Nickel enrichment in mantle olivine beneath a volcanic front 总被引:4,自引:1,他引:3
We found abnormally Ni-rich olivine (Fo = 93) with up to 5.3 wt% of NiO, ten times higher than the ordinary mantle value (0.4 wt%),
in a highly metasomatized mantle peridotite xenolith from Avacha volcano, the Kamchatka arc, Russia. The Ni enrichment displays
outward diffuse circular domains (<1 mm across) in fine-grained (mostly <100 μm) olivine-rich parts. Associated metasomatic
orthopyroxene also shows high NiO (<1.1 wt%). Such high Ni concentrations in olivine cannot be attained in ordinary residual
or cumulus peridotites, but are achievable via diffusion from Ni-rich sulfide melt. Sulfur-bearing silicic melt, the main
metasomatic agent for the Avacha peridotites, separated sulfide melt, which was fractionated to be Ni-rich at relatively low
temperatures. This is a new way of mobility and redistribution of Ni in the mantle, which is active in the mantle wedge, especially
beneath a volcanic front. 相似文献
86.
A. KamyshnyJr. M. Zilberbrand I. Ekeltchik T. Voitsekovski J. Gun O. Lev 《Aquatic Geochemistry》2008,14(2):171-192
Zerovalent sulfur and inorganic polysulfides were determined in nine sulfide-rich water wells in central and southern Israel.
Although the two locations belong to the same aquifer, they are characterized by different pH and hydrogen sulfide levels.
Hydrogen sulfide in the central Israel wells ranged between 19 and 32 μM, and the pH was 7.26 ± 0.07. The southern basin is
characterized by lower water circulation, lower pH (around 6.8), and higher hydrogen sulfide levels (>470 μM). Polysulfides
were determined by a rapid single-phase methylation using methyl trifluoromethanesulfonate (methyl triflate) reagent. The
summary polysulfide concentration for S42−–S72− species was found to be around 0.14–0.75 μM in the central region of Israel and substantially higher, 2.3–4.6 μM in the southern
region. The sum of polysulfide zerovalent sulfur and colloidal sulfur was quantitatively detected by cyanide derivatization
and compared to polysulfide sulfur determined by methyl triflate derivatization and to the chloroform extraction of zerovalent
sulfur. A method for the determination of sulfur undersaturation level—the ratio between dissolved elemental sulfur and its
equilibrium concentration in the presence of solid sulfur—based on the observed levels of the major polysulfide species is
described. The observed polysulfide speciation was compared with the predicted speciation under sulfur saturation conditions
taking into account the water temperature, its ionic strength, and pH. Criteria for sulfur saturation versus unsaturated conditions
were established based on (1) the chain length dependence of the ratio between the observed polysulfide concentrations and
their predicted value under sulfur saturated conditions, and (2) the difference between the concentration of zerovalent sulfur,
as determined by cyanolysis, and the total polysulfide sulfur. According to this dual criterion five of the water wells were
classified as being undersaturated with respect to sulfur, though for all the examined water wells the majority of the zerovalent
sulfur was in the form of polysulfide sulfur. 相似文献
87.
含铜镍岩浆起源及硫饱和机制:以新疆黄山南岩浆铜镍硫化物矿床Sr-Nd-Pb-S同位素和元素地球化学研究为例 总被引:2,自引:1,他引:1
新疆黄山-镜儿泉一带是天山东段重要岩浆铜镍硫化物成矿带,但对其中含铜镍岩浆起源和硫饱和机制尚存较大争议。黄山南岩体是近年来在该成矿带中发现的另一个含矿性较好的重要岩体。岩体可分为超镁铁质岩相和镁铁质岩相,超镁铁质岩相为主要含铜镍矿岩相,而镁铁质岩相并未发生明显的矿化。超镁铁质岩相岩石类型包括二辉橄榄岩、斜辉橄榄岩、橄榄二辉岩、二辉岩、角闪二辉岩及少量粗粒辉长岩,其中二辉橄榄岩和二辉岩是主要含矿岩石类型。镁铁质岩相由苏长岩、辉长岩、角闪辉长岩、闪长岩及石英闪长岩组成。黄山南岩体的(~(87)Sr/~(86)Sr)i(0.7036~0.7057)、ε_(Nd)(t)(-1.2~+7.4)、(~(206)Pb/~(204)Pb)i(17.152~18.088)、(~(207)Pb/~(204)Pb)i(15.385~15.571)和(~(208)Pb/~(204)Pb)i(37.127~38.252)变化范围均较大,显示了母岩浆遭受了较明显的壳源物质混染。岩浆源区在板片俯冲过程中壳源物质加入明显,而原始岩浆上升过程中壳源物质的混染有限。Sr-Nd-Pb同位素组成指示黄山南含矿岩体的形成与塔里木大火成岩省并无直接联系。虽然黄山南岩浆铜镍硫化物矿石δ~(34)S值介于-1.54‰~2.03‰之间,落在幔源硫的范围内,但是Se(×10~6)/S比值表明壳源硫的加入对成矿母岩浆硫饱和起到重要作用。 相似文献
88.
Dirk Schulze-Makuch Philip Goodell Thomas Kretzschmar John F. Kennedy 《Hydrogeology Journal》2003,11(3):401-412
Groundwater of the southern Jornada del Muerto Basin, an intermontane basin structure associated with the Rio Grande rift
located in south-central New Mexico, USA, was analyzed chemically and microbially. A microbial phospholipid fatty acids (PLFA)
analysis revealed a sparse microbial population consisting of relatively simple microorganisms with no major population changes
along the flow system. A nucleic acid (DNA) analysis of the groundwater resulted in the identification of ten eubacterial
and one archeal species. Chemical analyses revealed that sulfate along with calcium, magnesium, iron, and manganese is removed
by about an order of magnitude in concentration from the recharge area to the discharge area. The removal of iron, manganese,
magnesium, and to some extent calcium can be explained by oxidation reactions and the precipitation of dolomite. Sulfate and
additional calcium are most likely removed by the precipitation of gypsum. Thiobacillus spp. are oxidizing metal sulfides that occur as subsurface sulfide mineral deposits to sulfuric acid, which subsequently
reacts with calcium carbonate and water to precipitate gypsum. The presence of these sulfide deposits exposed to oxygenated
water in the deep groundwater flow system significantly alters its chemical and bacteriological composition.
Electronic Publication 相似文献
89.
A unique occurrence of strontian barite droplets associated with oriented planes of primary sulfide blebs in several clinopyroxene megacrysts was found in the Plio-Pleistocene basaltic tuff of Szentbékkálla (Bakony–Balaton Highland, western Hungary). The barite droplets contain 3.22–14.7 wt.% SrO, variable amount of FeO (up to 3.25 wt.%), minor CaO, CuO and NiO. Textural arrangements of oriented sulfide planes show that they were trapped as immiscible sulfide melt during crystallization of the clinopyroxene. Temperature and pressure estimation (978–1094 °C and 1.0–1.1 GPa) of the host clinopyroxenes indicate that formation of clinopyroxene megacrysts and entrapment of sulfide blebs happened under upper mantle conditions.
A genetic relationship between the sulfate and sulfide blebs is doubtful. Textural features suggest that the barite droplets might have been trapped together with the sulfide blebs from immiscible sulfide melts. However, it cannot be excluded that the barite formed during metasomatic event following the sulfide formation. 相似文献
90.
The physico-chemical characteristics of habitats have been considered to be one of the prime determinants of animal distribution within hydrothermal vent sites. However, the relative importance of abiotic to biotic influences is still debated. The primary aim of this study is twofold. The first is to determine and compare the ranges of physico-chemical conditions that characterize mussel-dominated and tubeworm-dominated communities at different sites within the vent field of the 9°50′N segment on the East Pacific Rise. The second is to better understand the processes that determine the variability of physico-chemical conditions in these habitats. In situ chemical and temperature measurements confirmed the high variability on small spatial and temporal scales within single aggregations of animals. The correlation of temperature and sulfide or pH revealed substantial differences between similar habitat-types at different sites, which cannot be attributed to changes in the extent of fluid dilution in the subseafloor. Further investigation of habitat variability within individual sites highlighted specific chemical features for the four sites studied, emphasizing the importance of an extensive in situ chemical analyses survey before using temperature as a proxy for chemical conditions. At Tica and Biovent, the fluid source characteristics were shown to vary only slightly within the sites, among aggregations discretely distributed over several meters distance. The variability of the total sulfide concentration and chemical speciation with temperature in the various habitats at each of these sites, can be reasonably simulated from the conservative mixing model of a single source fluid with seawater. The small variation of the empirical trends between different types of faunal assemblages at Tica suggests that changes in the fluid chemistry are not a prime determinant of the temporal succession of mussels and tubeworms. The findings of very similar sulfide–temperature relationships in two sites of different age and faunal compositions, Biovent and Tica, further support this idea. The two other sites, Mussel Bed and Riftia Field, differ both in the animal communities present and their chemistries show significant discrepancies from the predictions of the conservative mixing model. At Riftia Field, elevated iron concentrations and relatively low sulfide levels were correlated to unusually low pH, which could not be fully explained by conservative mixing of a typical diffuse vent fluid with seawater. The increased acidity results in a dramatic reduction in the anionic form, HS−. This is the form preferentially assimilated by the tubeworms and could explain the decline of the tubeworms at this site. At Mussel Bed the relationship between the sulfide concentration and temperature varied substantially among the aggregations surveyed and may reflect the influence of associated free-living microbial communities on the chemistry of mussel habitats. This study emphasizes the complex interplay of diffuse fluid formation in subsurface, chemical reactivity in the mixing zone, and biological activity in controlling of characteristics of vent habitats. 相似文献