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The Dachang mining district is the second largest producer of Sn in China and an important source of other metals. The known mineralizations can be divided into four groups: (1) cassiterite + Cu-Fe-Pb-Zn sulfides and sulfosalts, (2) Zn-Cu skarn, (3) Sb-W veins and (4) residual and placer concentrations of Sn and Fe oxides. Most orebodies are hosted by Upper Devonian calcareous, marly and quartzitic formations in spatial association with Cretaceous Yanshanian magmatites. A characteristic feature is the occurrence of stratiform, lens-shaped orebodies which appear to represent the root zone of overlying stockwork mineralizations. The metallogeny of the district may be interpreted in terms of an Upper Devonian Sn and polymetallic concentration with subsequent remobilization and, possibly, the introduction of additional elements during the late stages of the Yanshanian magmatism. 相似文献
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Mine waste dumps and heavy metal pollution in abandoned mining district of Boccheggiano (Southern Tuscany, Italy) 总被引：12，自引：1，他引：11
M. Benvenuti I. Mascaro F. Corsini P. Lattanzi P. Parrini G. Tanelli 《Environmental Geology》1997,30(3-4):238-243
Mining activity in the Boccheggiano-Fontalcinaldo area (Southern Tuscany) dates back at least to the 16th century AD and
lasted up to very recent times. Copper-rich hydrothermal veins, massive pyrite deposits, and their gossans were exploited.
Two mine waste dumps (Fontalcinaldo, Fontebona), one flotation tailings impoundment (Gabellino), and one roasting/smelting
waste dump (Merse-Ribudelli) in the study area were selected to ascertain the environmental effects of such protracted mining
activity. Primary waste mineralogy is mainly characterized by pyrite, gypsum, quartz, carbonates, chlorites, and micas. Secondary
oxidation mineralogy includes Fe and Cu sulfates and hydroxy sulfates, Cu carbonates, Fe and Al oxyhydroxides, and other phases
[neogenic cassiterite at Fontalcinaldo; probable calkinsite, (Ce,La)2(CO3)3· 4H2O, at Fontebona]. Mine waste samples show extremely variable contents of toxic elements (Cu, Pb, Zn, Bi, Cd, As), with average
values in the order of hundreds to thousands of parts per million (except for Bi and Cd). In some samples, the abundance of
proper minerals of these metals cannot account for the entire metal load. Conceivably, either solid solution substitutions
or adsorption processes contribute to the intake of released metals into newly formed minerals. Release and transport of pollutants
was affected to variable degrees by acid-neutralization processes. The highest metal and acid concentrations occur close to
the investigated wastes and rapidly decrease moving downstream some hundreds of meters or less, with the partial exception
for Mn and Fe. Other than dilution effects, this phenomenon may be ascribed to metal adsorption and precipitation of solid
phases.
Received: 16 April 1995 · Accepted: 14 December 1995 相似文献
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The dual-frequency Airborne Precipitation Radar-2 (APR-2) was deployed during the Wakasa Bay Experiment in 2003, for validation of the Advanced Microwave Scanning Radiometer-EOS. Besides providing extensive observations of diverse precipitating systems, this Ku-(13.4 GHz) and Ka-band (35.6 GHz) cross-track scanning radar measured sea surface backscatter simultaneously. While the characteristics of the normalized sea surface cross section /spl sigma//sup 0/ at Ku-band are well understood and widely published, the existing experimental data concerning /spl sigma//sup 0/ at Ka-band are scarce and results are inconsistent. In this letter, the Ku/Ka-band /spl sigma//sup 0/ measurements collected by APR-2, together with the estimated uncertainties, are discussed. In general, the measured /spl sigma//sup 0/ at Ka-band at around 10/spl deg/ incidence angle appears to be close to that at Ku-band /spl sigma//sup 0/, and Ka-band exhibits a nonnegligible difference in wind dependence with respect to Ku-band for moderate to high winds. 相似文献
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Several important mineral deposits of Sn, Zn, Cu, Pb, and other metals associated with Devonian sediments and Yanshanian (Cretaceous) granitic rocks are known in the Dachang district (Guangxi). Early genetic hypotheses related the origin of the deposits entirely to the Yanshanian granites. Recently, it was suggested that in Devonian times an earlier syngenetic metal concentration may have occurred, later overprinted by the Yanshanian metallogeny. This contribution is aimed at placing constraints on the physicochemical conditions during the Yanshanian ore formation-remobilization by studying the sulfide chemistry (arsenopyrite, sphalerite, stannite) and fluid inclusion data on the two major deposits in the area, i.e., the polymetallic cassiterite deposit of Changpo and the Zn-Cu skarn deposit of Lamo. Sphalerite and arsenopyrite are quite abundant in both deposits; stannite is minor, but fairly widespread at Changpo, and quite rare at Lamo. They are accompanied by pyrite, pyrrhotite, galena, chalcopyrite, cassiterite, fluorite, and a large variety of other sulfides and sulfosalts. The main compositional data for sphalerite and arsenopyrite are summarized as follows:Changpo: arsenopyrite associated with pyrrhotite 31.4–36.1 at% As; Associated with pyrite 31.9–33.1 at% As; sphalerite associated with pyrrhotite 18.3–22.2 mol% FeS; associated with pyrite 10.6–18.6 mol% FeS.Lamo: arsenopyrite associated with pyrrhotite 32.9–35.3 at% As; associated with pyrite 30.3–31.7 at% As; sphalerite associated with pyrrhotite, 17.2–24.4 mol% FeS; associated with pyrite 4.2–19.6 mol% FeS.Partitioning of Fe and Zn between coexisting sphalerite and stannite from Changpo indicates temperatures of 300°–350°C. For Lamo, the following fluid inclusion data are available: fluorite, salinities of 0–9.5 equiv. wt% NaCl, and homogenization temperatures between 160°C and 250°C; quartz, moderate salinities (0–4.6 equiv. wt% NaCl), and homogenization temperatures of 208°–260°C. Combining the mineralogical evidence with the compositional and fluid inclusion data, it is suggested that the evolution of the environment during the Yanshanian event was characterized by the following parameters: pressure was relatively low (on the order of 1–1.5 kb); temperature may have been as high as 500°C during deposition of the As-richest arsenopyrites, but eventually dropped below 200°–250°C in the latest stages; with an increase in sulfur activity and/or the decrease in temperature pyrrhotite was no longer stable in the latest stages of mineralization. 相似文献
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Summary The barite-pyrite-(Pb-Zn-Ag) deposit of Pollone is located in the southernmost tip of the Apuane Alps metamorphic core complex, and is hosted by a siliciclastic formation of pre-Norian age. The southern sector of the deposit mainly consists of stratiform, supposedly syngenetic, barite-pyrite orebodies, whereas the northern area is characterized by a barite-pyrite-(Pb-Zn-Ag) vein system. Vein geometry in the northern area is controlled by a shear zone, developed during the greenschist facies metamorphism which affected the Apuane Alps core complex between 27 and 8 Ma, that was responsible for fluid focusing and vein emplacement. At Pollone, arsenopyrite and chlorite geothermometers show broadly comparable results, and suggest local metamorphic peak temperatures between 320 and 350°C. Phengite geobarometry indicates minimum pressures of about 3.5 kbar. Fluid inclusion data and mineral equilibria suggest that the mineralizing fluids were initially hotter than the country rocks (about 450°C at 3.5–4.0 kbar). Rocks in direct contact with the orebodies are depleted in Rb and enriched in Sr in comparison to similar rocks elsewhere in the area. This is attributed to the presence of Rb-poor muscovite and Sr-rich barite. Rb-depleted muscovites suggest mineral-fluid interaction in a rock reservoir characterized by a different (modal) mineralogical composition than the Pollone host rocks. The progressive decrease of Sr in barite with increasing distance from the orebodies may be explained with a temperature decrease along the infiltration paths of mineralizing fluids (i.e., from the vein into the wall rocks). The similar O-isotope composition of quartz from veins and host rocks is explained with the overall homogeneous O-isotope composition of the Alpi Apuane basement rocks. This indicates a limited interaction between mineralizing fluids and the rocks exposed at Pollone. Remobilization of syngenetic orebodies was conceivably of minor importance in the production of metamorphogenec veins. Fluid cooling along a major tectonic lineament is thought to be responsible for barite deposition.
Die metamorphogenen Baryt-Pyrit (Pb-Zn-Ag) Gänge von Pollone, Apuanische Alpen, Toskana: Geometrie der Gänge, Geothermobarometrie, Flüssigkeitseinschlüsse und Geochemie
Zusammenfassung Die Baryt-Pyrit (Pb-Zn-Ag) Lagerstätte von Pollone liegt im südlichsten Ende des metamorphen Kern-Komplexes der Apuanischen Alpen, und sitzt in einer siliziklastischen Formation prä-Norischen Alters auf. Der südliche Sektor der Lagerstätte besteht hauptsächlich aus stratiformen, wahrscheinlich syngenetischen Baryt-Pyrit-Erzkörpern, während der nördliche Teil des Gebietes durch ein Baryt-Pyrit (Pb-Zn-Ag) Gangsystem charakterisiert wird. Die Geometrie der Gänge im Nordteil wird durch eine Scherzone kontrolliert, die während einer grünschieferfaziellen Metamorphose entstanden ist, die den Kernkomplex der Apuanischen Alpen zwischen 27 und 8 Ma betroffen hat. Diese Scherzone war auch für die Zufuhr der Fluide und die Platznahme der Gänge verantwortlich. In Pollone zeigen Arsenopyrit- und Chlorit-Geothermometrie weithin vergleichbare Ergebnisse und weisen auf lokale Maximaltemperaturen der Metamorphose zwischen 320 und 350°C hin. Phengit-Geobarometrie läßt Minimal-Drucke von ungefähr 3,5 kbar erkennen. Fluidflüssigkeitseinschluß-Daten und Mineral-Gleichgewichte zeigen, daß die erzbringenden Fluide ursprünglich heißer als die Wirtsgesteine waren (ca. 450 °C für P von 3,5 bis 4 kbar). Gesteine, die im direkten Kontakt mit den Erzkörpern sind, zeigen eine Anreicherung an Rb und eine Anreicherung an Sr, im Vergleich mit ähnlichen Gesteinen, die im Gebiet anzutreffen sind. Dies wird auf das Vorkommen von Rb-armen Muscovit und Sr-reichen Baryt zurückgeführt. An Rbabgereicherte Muscovite legen Mineral-Fluid-Reaktionen nahe, die in einem Gesteinsreservoir abliefen, das durch eine andere mineralogische Zusammensetzung als die Wirtsgesteine von Pollone charakterisiert war. Der zunehmende Verlust von Sr im Baryt mit zunehmender Entfernung von den Erzkörpern, kann durch einen Temperaturabfall entlang der Infitrations-Pfade der erzführenden Lösungen erklärt werden (d.h. von Gang in die Nebengeseine). Die ähnliche Sauerstoff-Isotopen-Zusammensetzung für Quarz aus den Gängen und den Nebengesteinen läßt sich auf die allgemein homogene Sauerstoffisotopen-Signatur des Basements der Apuanischen Alpen zurückführen. Dies weist auf beschränkte Wechselwirkung zwischen erzführenden Lösungen und den in Pollone anstehenden Gesteinen hin. Die Remobilisation von syngenetischen Erzkörpern in Pollone war nur von geringer Bedeutung für die Entstehung der metamorphogenen Gänge. Abkühlung der Fluide an einem wichtigen tektonischen Lineament gilt als Ursache für den Absatz von Baryt.相似文献
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G. Tanelli 《Mineralium Deposita》1982,17(2):279-294
The city of Dayu is the center of the most important tungsten district of PRC. Valuable quantities of Sn, Mo, Bi, Nb, Ta, REE, Cu, Pb, Zn, Ag, Be and Li are also recovered. At the Xihuashan and Dangping mines, hundreds of the typical Jiangxi wolframite-quarz veins, located at the top and marginal parts of a Jurassic biotite granite intrusion, are mined. At Piaotang the mined ore bodies consist of a stockwork-type of mineralization which cuts the roof-rocks (Cambrian metasediments: phyllite, quartz sandstone, hornfels) of the biotite granite. Around the mineralizations, the country rocks display extensive alteration: namely K-feldspar alteration and greisenization in granite; tourmalinization, muscovitization, silicification, pyrophillitization in the metasediments. The main mineralogy and parageneses of the veins and veinlets can be summarized as follows: I stage — oxide — (wolframite, cassiterite, molybdenite, quartz, K-feldspar, beryl, fluorite, topaz), the best represented; II stage — sulphide — (chalcopyrite, galena, sphalerite, pyrite, pyrrhotite, bismuthinite, cassiterite, wolframite, quartz) well represented at Piaotang; III stage — carbonate — (pyrite, scheelite, chlorite, sericite, fluorite, quartz, calcite). The fracture-controlled mineralizations of Dayu appear to be the product of a continous multistage process related to the late phases of the jurassic Yenshanian magmatism.
Nel Distretto di Dayu, in cui operano tre miniere principale e sei centri estrattivi minori, viene prodotto poco meno di un quarto (2300 ton/anno) del l'intera produzione in tungsteno della RPC. Oltre al W vengono prodotte apprezzabili quantità di una ventina di altri elementi, fra i quali: Sn, Mo, Bi, Nb, Ta, Terre Rare, Cu, Pb, Zn, Ag, Be, Li, etc.. I corpi minerari sono costituiti, sia da alcune centinaia di vene a quarzo-wolframite, che con una potenza media di 40 cm, tagliano le parti marginali di una intrusione di granito biotitico del Giura, sia da mineralizzazioni tipo stockworks che si espandono nelle metamorfiti (filladi, arenarie quarzose parzialmente cornubianitiche) cambriane poste a tetto della cupola granitica. Il granito biotitico, all' intorno delle vene, presenta zone simmetriche di alterazione, a K-feldspato e greisen; nei metasedimenti i principali minerali di alterazione sono: tormalina, muscovite, quarzo, pirofillite e topazio. Le principali caratteristiche mineralogiche e paragenetiche dei corpi minerari possono essere come di seguito schematizzate: I stadio — a prevalenti ossidi (wolframite, cassiterite, molibdenite, quarzo, K-feldspato, berillo, fluorite, topazio), il meglio rappresentato; II stadio — a prevalenti solfuri (calcopirite, galena, sfalerite, pirite, pirrotina, bismutinite, cassiterite, wolframite, quarzo), particolarmente ben rappresentato nella miniera di Piaotang; III stadio — a prevalenti carbonati (pirite, scheelite, clorite, sericite, fluorite, quarzo, calcite). La metallogenesi di Dayu, sviluppatasi in un sistema tettonicamente attivo é geneticamente associabile alle fasi tardive del magmatismo Yenshanide giurassico.相似文献
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Many episodes of magmatic activity during the Miocene and Quaternary in Central Italy produced intrusive and effusive sub-alkaline and alkaline-potassic rocks. Their emplacement generated hydrothermal circulation that in places resulted in important minerogenetic events (Hg, Sb). Moreover the presence of moderate gold epithermal mineralizations has been recently pointed out. The results of geochemical research carried out to determine the gold content of some magmatites from the Tuscany-Latium district, using an Hg-Sn extraction technique and determination by GFAAS (Graphite Furnace Atomic Absorption Spectroscopy) are presented here. The results clearly indicate that the magmatites sampled contain quantities of gold greater than the average concentrations given in the literature. These anomalies are attributable to enrichment of the original melts, and may be one of the primary sources of gold for epithermal minerogenetic processes. 相似文献
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The S-isotope composition (δ34SCDT) of 213 samples of sulfides, sulfates and native sulfur from the pyrite mineralizations of southern Tuscany and associated country rocks were determined. The sulfur isotopic composition of pyrite is quite homogeneous and similar for all studied ore bodies, with an average δ34S value near +9,5‰. Pyrite disseminated within the Filladi di Boccheggiano formation, and thought to be authigenic, shows a much larger range of δ34S values (-13.1 to +14.5‰). The isotopic compositions of other sulfides associated with pyrite in the deposits show that isotopic equilibrium among sulfides was approached on a regional scale, but seldom fully attained. Isotopic data suggest that sedimentary marine sulfate was the ultimate source of sulfur in ores. Sulfates (mostly anhydrite) from the sulfate-carbonate lenses associated with both the Filladi di Boccheggiano and the Calcare Cavernoso formations also have similar and homogeneous compositions (average δ34S=+15–16‰). Coexisting sulfates and sulfides are not in isotopic equilibrium. In the light of the isotopic data, among the many proposed genetic models for the largest stratabound pyrite bodies the two following alternatives appear the most likely: 1) in agreement with recently suggested hypotheses, the ore bodies are older than the emplacement of the Mio-Pliocenic granitoids in the area, and are probably hydrothermal-sedimentary in origin, coeval with associated country rocks; 2) the ore bodies were formed as a consequence of bacterial reduction of anhydrite in low-temperature convection systems related to the early stages of the Mio-Pliocenic thermal anomaly. In both cases, the emplacement of the Mio-Pliocenic granitoids caused metamorphism and remobilization of the pre-existing ores, producing smaller discordant mineralized bodies. 相似文献
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