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1.
Abdolkarim Rezaeian Iraj Rasa Ali Amiri Mohammad Reza Jafari 《Arabian Journal of Geosciences》2014,7(6):2329-2338
The study of oxygen and carbon isotopic ratios has gained importance to determine the origin of ore-bearing fluids, carbon origin, and also to determine the formation temperature of non-sulfide Pb and Zn minerals. In order to determine the origin of fluids and carbon existing in Zn carbonate minerals in Chah-Talkh deposit, initially the amounts of δ18OSMOW and δ13CPDB changes in various zinc minerals in important deposits in Iran and the world were studied, and then by comparing these values in Chah-Talkh deposit with those of other deposits, the origin of fluids responsible for ore forming, carbon, and formation temperature of Chah-Talkh deposit was determined. The range of δ18OSMOW changes in smithsonite mineral in non-sulfide lead and zinc deposits varies from 18.3 to 31.6 ‰, and δ18OSMOW in hydrozincite mineral varies from 7.8 to 27 ‰. Due to the impossibility of smithsonite sampling from Chah-Talkh deposit (due to it being fine-grained and dispersed), hydrozincite minerals which have high isotopic similarities with smithsonite are used for the isotopic analysis of carbon and oxygen. The range of δ18OSMOW changes in hydrozincite mineral of Chah-Talkh deposit varies from 7.8 to 15.15 ‰, which places in the domain of metamorphic water. The extensiveness of δ18OSMOW changes in Chah-Talkh indicates the role of at least two fluids in the formation of non-sulfide minerals. The obtained formation temperature of non-sulfide minerals (hydrozincite) in Chah-Talkh deposit is 70 to 100 °C, which indicates the role of metamorphic fluids in the formation of deposit. Complete weathering of sulfide minerals to a depth of 134 m confirms the role of rising metamorphic fluids in the formation of non-sulfide minerals. The δ13CPDB values of Chah-Talkh deposit are set in the range of atmospheric CO2 and carbonate rocks, in which the existence of atmospheric CO2 indicates the role of atmospheric fluids, and the existence of carbonate carbon rock indicates of the role of metamorphic fluids in the precipitation of non-sulfide Zn minerals. 相似文献
2.
Hemimorphite, Zn4Si2O7(OH)2·H2O, one of the most common minerals in non-sulfide Zn deposits, together with smithsonite and hydrozincite, is one of the most abundant minerals in the “calamine” deposits in SW Sardinia. In spite of their importance for the development of ore genesis models, the stability properties of hemimorphite are poorly known. This paper presents solubility experiments on two different types of hemimorphite: a “geological” hemimorphite from a supergene non-sulfide Zn deposit, of supposed abiotic origin, and a hemimorphite precipitated by bacterial activity. Both specimens were characterized, before and after the experiment, by Synchrotron Radiation X-ray powder diffraction, Scanning Electron Microscopy, and X-ray Absorption Spectroscopy. The calculated solubility product constants (logKs) are similar for both “geological” and biogenic hemimorphite (30.3 ± 0.4 and 30.5 ± 0.1, respectively). During the solubility experiment, biological hemimorphite undergoes an amorphous to crystalline phase transition, and the distinctive features (mineralized bacterial sheaths and organic filaments), that allowed us to demonstrate its biological origin, are no longer recognizable by Scanning Electron Microscopy.The results of this study may be useful for developing ore genesis models, including evolution in a supergene environment, and in general for performing geochemical speciation and equilibrium calculations. Moreover, our findings open the way for a new interpretation of hemimorphite-forming processes, and suggest the possibility that bacteria may have played a role in the formation of this mineral in ore deposits. 相似文献
3.
The Lavrion carbonate-hosted Pb-Ag-Zn deposit in southeast Attica, Greece, consisted of significant non-sulfide ore bodies. The polymetallic sulfide mineralization was subjected to supergene oxidation, giving rise to gossan. The principal non-sulfide minerals of past economic importance were smithsonite, goethite and hematite. The supergene mineral assemblages occupy secondary open spaces and occur as replacement pods within marble. Calamine and iron ore mainly filled open fractures. X-ray diffraction and scanning electron microscopy of samples of oxidized ore indicate complex gossan mineralogy depending on the hypogene mineralogy, the degree of oxidation and leaching of elements, and the local hydrologic conditions. Bulk chemical analysis of the samples indicated high ore-grade variability of the supergene mineralization. On multivariate cluster analysis of geochemical data the elements were classified into groups providing evidence for their differential mobilization during dissolution, transport and re-precipitation. The mode of occurrence, textures, mineralogy and geochemistry of the non-sulfide mineralization confirm that it is undoubtedly of supergene origin: the product of influx into open fractures in the country rock of highly acidic, metal-rich water resulting from the oxidation of pyrite-rich sulfide protore. Dissolution of carbonates led to opening of the fractures. Mineral deposition in the supergene ore took place under near-neutral to mildly acidic conditions. The supergene dissolution and re-precipitation of Fe and Zn in the host marble increased metal grades and separated iron and zinc from lead, thereby producing economically attractive deposits; it further contributed to minimization of pollution impact on both soil and ground water. 相似文献
4.
The present paper reports the first detailed petrological and geochemical study of non-sulfide Zn–(FePb) deposits in the Riópar area (Prebetic Zone of the Mesozoic Betic Basin, SE Spain), constraining the origin and evolution of ore-forming fluids. In Riópar both sulfide and non-sulfide Zn–(FePb) (“calamine”) ores are hosted in hydrothermally dolomitized Lower Cretaceous limestones. The hypogene sulfides comprise sphalerite, marcasite and minor galena. Calamine ores consist of Zn-carbonates (smithsonite and scarce hydrozincite), associated with abundant Fe-(hydr)oxides (goethite and hematite) and minor Pb-carbonates (cerussite). Three smithsonite types have been recognized: i) Sm-I consists of brown anhedral microcrystalline aggregates as encrustations replacing sphalerite; ii) Sm-II refers to brownish subhedral aggregates of rugged appearance related with Fe oxi-hydroxides in the surface crystals, which replace extensively sphalerite; and iii) Sm-III smithsonite appears as coarse grayish botryoidal aggregates in microkarstic cavities and porosity. Hydrozincite is scarce and appears as milky white botryoidal encrustations in cavities replacing smithsonite. Also, two types of cerussite have been identified: i) Cer-I cerussite consists of fine crystals replacing galena along cleavage planes and crystal surfaces; and ii) Cer-II conforms fine botryoidal crystals found infill porosity. Calcite and thin gypsum encrustations were also recognized. The field and petrographic observations of the Riópar non-sulfide Zn–(FePb) revealed two successive stages of supergene ore formation under meteoric fluid processes: i) “gossan” and “red calamine” formation in the uppermost parts of the ore with deposition of Fe-(hydr)oxides and Zn- and Pb-carbonates (Sm-I, Sm-II and Cer-I), occurring as direct replacements of ZnPb sulfides; and ii) “gray calamine” ore formation with deposition of Sm-III, Cer-II and hydrozincite infilling microkarst cavities and porosity. The stable isotope variation of Riópar smithsonite is very similar to those obtained in other calamine-ore deposits around the world. Their CO isotope data (δ18O: + 27.8 to + 29.6‰ V-SMOW; δ13C: − 6.3 to + 0.4‰ V-PDB), puts constrains on: i) the oxidizing fluid type, which was of meteoric origin with temperatures of 12 to 19 °C, suggesting a supergene weathering process for the calamine-ore formation under a temperate climate; and ii) the carbon source, that resulted from mixing between two CO2 components derived from: the dissolution of host-dolomite (13C-enriched source) and vegetation decomposition (13C-depleted component). 相似文献
5.
粤东麻坑非硫化物型锌矿锌的赋存状态及成因讨论 总被引：1，自引：0，他引：1
麻坑锌矿位于粤东晚古生代梅州拗陷东北部、近南北向蕉岭向斜的西翼,含矿岩石为强风化浅绿色粘土岩、黑色锰土及黑土角砾岩,未见原生金属硫化物,因此,有关锌的赋存状态及矿床成因一直不明。本文通过系统的岩矿石样品光薄片、砂光片显微镜下鉴定、X射线粉晶衍射物相分析和电子探针成分分析,查明了锌矿物主要以异极矿形式存在,仅含极少量菱锌矿;本矿床氧化作用较为彻底,矿床成因属浅成非硫化物型锌矿的直接交代亚类。上述锌的赋存状态及矿床成因探讨对类似矿床的认识与勘查具重要意义。 相似文献
6.
The Hakkari nonsulfide zinc deposit is situated close to the southeastern border of Turkey. Here both sulfide and nonsulfide Zn ≫ Pb ores are hosted in carbonate rocks of the Jurassic Cudi Group with features typical of carbonate-hosted supergene nonsulfide zinc mineralization. The regional strike extent of the mineralized district is at least 60 km. The age of the supergene deposit has not been determined, but it is probable that the main weathering happened during Upper Tertiary, possibly between Upper Miocene and Lower Pliocene. The Hakkari mineralization can be compared to other carbonate-hosted Zn–Pb deposits in Turkey, and an interpretation made of its geological setting. The zinc mineral association at Hakkari typically comprises smithsonite and hemimorphite, which apparently replace both sulfide minerals and carbonate host rock. Two generations of smithsonite are present: the first is relatively massive, the second occurs as concretions in cavities as a final filling of remnant porosity. Some zinc is also hosted within Fe–Mn-(hydr)oxides. Lead is present in cerussite, but also as partially oxidized galena. Lead can also occur in Mn-(hydr)oxides (max 30% PbO). The features of the supergene mineralization suggest that the Hakkari deposit belongs both to the “direct replacement” and the “wall-rock replacement” types of nonsulfide ores. Mineralization varies in style from tabular bodies of variable thickness (< 0.5 to 13 m) to cross-cutting breccia zones and disseminated ore minerals in pore spaces and fracture planes. At Hakkari a As–Sb–Tl(≫ Hg) geochemical association has been detected, which may point to primary sulfide mineralization, quite different from typical MVT. 相似文献
7.
The Jabali Zn–Pb–Ag deposit is located about 110 km east of Sana'a, the capital of Yemen, along the western border of the Marib-Al-Jawf/Sab'atayn basin. The economic mineralization at Jabali is a nonsulfide deposit, consisting of 8.7 million tons at an average grade of 9.2% zinc, derived from the oxidation of primary sulfides. The rock hosting both primary and secondary ores is a strongly dolomitized carbonate platform limestone of the Jurassic Shuqra Formation (Amran Group). The primary sulfides consist of sphalerite, galena and pyrite/marcasite. Smithsonite is the most abundant economic mineral in the secondary deposit, and is associated with minor hydrozincite, hemimorphite, acanthite and greenockite. Smithsonite occurs as two main generations: smithsonite 1, which replaces both host dolomite and sphalerite, and smithsonite 2, occurring as concretions and vein fillings in the host rock. At the boundary between smithsonite 1 and host dolomite, the latter is widely replaced by broad, irregular bands of Zn-bearing dolomite, where Zn has substituted for Mg. The secondary mineralization evolved through different stages: 1) alteration of original sulfides (sphalerite, pyrite and galena), and release of metals in acid solutions; 2) alteration of dolomite host rock and formation of Zn-bearing dolomite; 3) partial dissolution of dolomite by metal-carrying acid fluids and replacement of dolomite and Zn-bearing dolomite by a first smithsonite phase (smithsonite 1). To this stage also belong the direct replacement of sphalerite and galena by secondary minerals (smithsonite and cerussite); 4) precipitation of a later smithsonite phase (smithsonite 2) in veins and cavities, together with Ag- and Cd-sulfides.The δ18O composition of Jabali smithsonite is generally lower than in other known supergene smithsonites, whereas the carbon isotope composition is in the same range of the negative δ13C values recorded in most supergene nonsulfide ores. Considering that the groundwaters and paleo-groundwaters in this area of Yemen have negative δ18O values, it can be assumed that the Jabali smithsonite precipitated in different stages from a combination of fluids, possibly consisting of local groundwaters variably mixed with low-temperature hydrothermal waters. The carbon isotope composition is interpreted as a result of mixing between carbon from host rock carbonates and soil/atmospheric CO2.The most favorable setting for the development of the Jabali secondary deposit could be placed in the early Miocene (~ 17 Ma), when supergene weathering was favored by major uplift and exhumation resulting from the main phase of Red Sea extension. Low-temperature hydrothermal fluids may have also circulated at the same time, through the magmatically-induced geothermal activity in the area. 相似文献
8.
Ian R. Jonasson Lionel E. Jackson Donald F. Sangster 《Journal of Geochemical Exploration》1983,18(3):189-194
An extensive deposit of secondary zinc minerals has been formed at Howard's Pass, Yukon by replacement of mosses and as a cement within talus. The deposits are of Holocene age (younger than 9610 yr. B.P.) and occur in blanket peat bogs percolated by zinc-rich springwaters. Buried moss strata undergo cell by cell replacement forming zincian clacite, smithsonite and hemimorphite. The last is the most important secondary mineral in both mosses and talus. 相似文献
9.
Oxidation of the relatively iron sulfide-poor Dugald River zinc-lead lode in northwest Queensland and reaction of the acid solutions with carbonate has resulted in an undifferentiated gossan profile. The gossan is composed predominantly of quartz, goethite, hematite, barite, adularia, plumbian jarosite, plumbogummite and minor mica, chlorite, kaolinite and montmorillonite. Barite and adularia are formed by the breakdown of the barium feldspar hyalophane (K, Na, Ba)[(Al, Si)4O8] which occurs in the lode.Lead in the gossan is contained within the secondary minerals plumbogummite and plumbian jarosite, and in traces of anglesite and cerussite, whereas Zn occurs in the barite, secondary lead minerals and coronadite structures, and is adsorbed by iron oxides, phyllosilicates and carbonaceous matter. Only traces of zinc minerals smithsonite, goslarite and hemimorphite were detected.Use of Gresens' general metasomatic equation has enabled quantitative determination of compositional changes resulting from the oxidation of the ore. Silicon, Al, Ti and Ba are essentially immobile under the mildly acidic oxidizing conditions. In decreasing order of mobility Cd, Ca, S, Na, K, Mn, Mg, Zn, Ni and Cu, together with CO2 and Tl, have been leached from the gossan profile, while Ag, Sb, Se, As, Fe and Pb appear to have been added to the gossan, notably in a zone of solution-deposited secondary minerals where they have been concentrated, possibly as a result of leaching from the surface gossan. 相似文献
10.
“Nonsulfides” is a term, which comprises a series of oxidized Zn(Pb)-ore minerals. It has also been used to define a special deposit type, mainly considered as derived from the weathering of Zn(Pb) sulfide concentrations. However, nonsulfide zinc deposits have been distinguished between supergene and hypogene, according to their mineralogy, geological characteristics and genetic setting. The supergene deposits formed by weathering and oxidation at ambient temperatures, whereas the hypogene ones are considered hydrothermal, or associated with metamorphic processes on primary sulfide ores.In this review paper, a comparison between a number of several nonsulfide deposits has been carried out: typical “Calamines”, peculiar “Calamines” and “Others”. The whole group comprises deposits of typical supergene origin, mixed supergene–hypogene mineralizations, and oxidized concentrations characterized by different metals only locally associated with zinc. The Zn–Pb nonsulfide concentrations hosted in carbonate rocks, which are mainly attributed to “wall-rock replacement” and “direct-replacement” supergene processes, are the typical “Calamines” (Liège district, Belgium; Iglesias district, Italy; Silesia–Cracow district, Poland). Peculiar “Calamine” deposits are those mineralizations that have been generally considered as supergene, but which are instead genetically related, at least partly, to hypogene processes (e.g. Angouran, Iran; Jabali, Yemen), though mineralogically and texturally similar to supergene nonsulfide deposits. The “Others” are prevailingly supergene nonsulfide zinc deposits not hosted in carbonate rocks (Skorpion, Namibia; Yanque, Peru), or characterized by other metals as main commodities, like lead (Magellan, Australia), silver (Sierra Mojada, Mexico; Wonawinta, Australia) or vanadium (Otavi Mountainland, Namibia).Minerals of current economic importance in most “Calamine” deposits are smithsonite, hydrozincite, and cerussite. This mineralogical association is generally simple but, when the “Calamines” are dolomite-hosted, one of the consequences of the “wall-rock replacement” process is the generation of a series of economically useless Zn- and Mg-bearing mixed carbonate phases. Secondary deposits hosted in silicatic (sedimentary or volcanic) rocks mainly contain hemimorphite and/or sauconite. Lead-, Ag- and V-rich nonsulfide ores are characterized by a more complex mineralogical association: mixed Pb-carbonates, Pb-sulfates, Pb-phosphates, Pb-arsenates, various Ag-sulfosalts, and Zn–Pb–Cu-vanadates.Carbon and oxygen stable isotope studies allow distinguishing between supergene and hypogene nonsulfide deposits, evaluating the effects of oxidative heating and even gaining indirect paleoclimatic information. The oxygen-isotope variation of the individual carbonate minerals within a deposit is relatively small, indicating constant formation temperatures and a single, meteoric fluid source. Carbon-isotope values are highly variable, thus suggesting several isotopically distinct carbon sources.Periods of paleoclimatic switch-overs from seasonally humid/arid to hyperarid have been considered as the most favorable conditions for the formation and preservation of supergene nonsulfide deposits. However, while several recent nonsulfide deposits throughout the world are positioned between 15° and 45° N latitude, thus pointing to a warm and humid weathering climate, others have been deposited in sub-Arctic regions.The economic value of the nonsulfide Zn(Pb–Ag–V) ores is highly variable, because more than in the case of metallic sulfide deposits, it resides not only on the geological setting, but also on their mineralogy that can directly influence processing and metallurgy. 相似文献
11.
《矿物学报》2013,(Z1)
Using variety of modern testing methods, the processing mineralogical characteristics for a lead and zinc oxide ore in Sichuan were studied systematically. The chemical analysis result shows that the lead and zinc oxide content exceeding the minimum industrial grade and iron ore, total iron content reaches a minimum industrial grade and associated with gold and silver; The mineralogical analysis result shows that lead and zinc mineral composition and configuration are very complexity. The zinc minerals and zinciferous minerals are sphalerite, hemimorphite, Smithsonite, Hydrozincite, zinc chlorite, limonite, zinc dolomite and zincocalcite; lead minerals and plumbiferous minerals are mainly galena, cerussite, anglesite, limonite and Coronadite; The minerals disseminated grain size are very fine and mineral dissemination characteristics are very complex ; expected theoretical recoveries for lead and zinc were 72% and 67% respectively. The results of this study provide basic data and theoretical basis for ore dressing. 相似文献
12.
The distribution characteristics and existing state of cadmium in the Jinding Pb-Zn deposit were studied. It was discovered that Cd was mainly distributed in sphalerite as an isomorphic impurity. There was a good correla-tion between Cd and Zn in the primary ore. With the oxidation and resolution of pyrite, sphalerite, sulfide, and etc., many secondary minerals, such as colloform sphalerite and smithsonite, were formed. The distribution of Cd is not symmetrical, and enrichment and dilution were observed in partial area of the oxidation zone in the deposit. Cd, except in external pore space or cracks of secondary minerals as independent minerals, such as greenockite, was mainly distributed in sphalerite as an isomorphic impurity in the secondary sphalerate and smithsonite in the oxida-tion zone. The research showed that Cd showed a very strong active transfer ability in the oxidation process, not only indicating that supergene leaching might be the main reason for Cd enrichment in some Pb-Zn deposits, but also reflecting that Cd was easily mobilizeed and transferred to pollute ore areas in the oxidation process. Furthermore, Cd in oxidation ore was more easily mobilized and transferred to induce bad hazards for ore areas with the effect from AMD which was produced from oxidation of sulfides. 相似文献
13.
Ying Wang Shu Zhang Zhiguo Cheng He Huang Jinchao Ye 《International Geology Review》2017,59(16):2065-2077
The strata-bound Pb–Zn deposits in western China share many similarities and are controversial in genesis. The large Uragen Pb–Zn deposit is located in the northwestern part of the Kashgar sag, southwest of Tarim Basin, Xinjiang, NW China. With the 980.9 Mt tons of Pb–Zn ores at 0.45%Pb and 2.61%Zn, it is the third largest known Pb–Zn deposits in China. The orebodies are stratiform and stratabound and are predominantly controlled by the Uragen syncline that has an E–W axial trend. Mineralization mostly occurs in sandstones and conglomerates of the Lower Cretaceous Kezilesu Group (K1kz), with a small amount in the Palaeocene limestone. The main ore types consist predominantly of disseminated ore with minor massive ore, veined ore, and breccia ore. The primary metal minerals are composed of sphalerite, galena, pyrite, and minor arsenopyrite and chalcopyrite, and the supergene metal minerals include smithsonite, cegamite, beudantite, jarosite, limonite, and minor hemimorphite. The gangue minerals are composed of dolomite, calcite, quartz, celestite, and gypsium. Our new Rb–Sr isotopic analyses on the separated sphalerite, galena yielded an isochron age of 55.1 ± 1.6 Ma, coeval to an isochron age of 55.4 ± 2.2 Ma by Sm–Nd isotopic data. This age is much younger than the youngest ore-bearing strata (E11, 65.5–61.7 Ma), arguing for an epigenetic origin. The calculated initial 87Sr/86Sr ratio of sulphides is 0.710322, which is much lower than those of basement formation, regional bituminous sandstone, and even the ore-bearing strata, but higher than the regional mantle-derived, alkaline volcanic rocks and marine carbonate. The calculated initial 143Nd/144Nd ratio of calcite and galena is 0.512081. These data suggest that the metals may be chiefly derived from crust, possibly from the minor contribution of mantle materials. Our new-age data, in combination with the previous data, suggest that there probably is a huge medium-low-temperature epigenetic stratabound Pb–Zn belt, which is possibly correlated to the India–Asia collision event. 相似文献
14.
云南乐红铅锌矿床氧化带中异极矿的矿物学特征及其意义 总被引：7，自引：0，他引：7
云南乐红铅锌矿床氧化带十分发育,呈细脉或葡萄状产于氧化矿石中的白色矿物曾被认为是菱锌矿,笔者对该矿物作了物理、光学性质,化学发,Ｘ射线衍射,红外光谱及失重和差热分析研究,确定其为异极矿。其晶体化学式为Ｚｎ３．９８（Ｓｉ２．０１Ａｌ０．０１）２．０２Ｏ７（ＯＨ）２．０３．０．８８Ｈ２Ｏ晶胞参数ａ＝０．８３８０（４）ｎｍ,ｂ＝１．０７１８（７）ｎｍ,ｃ＝０．５１２５（６）ｎｍ。对异极矿矿物学特征的全面 相似文献
15.
Vito Coppola Maria Boni H. Albert Gilg Bozena Strzelska-Smakowska 《Mineralium Deposita》2009,44(5):559-580
The Silesia–Cracow district in Poland has been one of the world’s principal sources of zinc from nonsulfide zinc ore (Polish:
galman). The still remaining nonsulfide ore resources can be estimated at 57 Mt at 5.6% Zn and 1.4% Pb. Nonsulfide mineralization
is mainly hosted by Lower Muschelkalk (Triassic) limestone and is associated with different generations of the hydrothermal
ore-bearing dolomite (OBD I, II, III). A fundamental ore control is believed to have been exerted by the basement faults,
which were repeatedly reactivated during the Alpine tectonic cycle, leading to the formation of horst-and-graben structures: these dislocations may have caused short periods of emersion and the circulation of meteoric waters during the
Cenozoic. Nonsulfide ores show a wide range of morphological characteristics and textures. They occur as earthy masses, crystalline
aggregates, and concretions in cavities. Breccia and replacement textures are also very common. The most important mineral
phases are: smithsonite, Fe–smithsonite, Zn–dolomite, goethite, and Fe–Mn(hydr)oxides. Minor hemimorphite and hydrozincite
have also been detected. Two distinct nonsulfide ore types occur: the predominant red galman and the rare white galman. In the white galman, Fe–smithsonite and Zn–dolomite are particularly abundant. This ore type is commonly considered as a peripheral hydrothermal
alteration product related to the same fluids that precipitated both the OBD II–III and the sulfides. In contrast, a supergene
origin is commonly assumed for the red galman. Evidence of the petrographic and mineralogical difference between white and red galman is also found in stable isotope data. Smithsonite from red galman shows a limited range of δ
13CVPDB values (−10.1 to −11.4‰), and δ
18OVSMOW values (25.3‰ to 28.5‰, mean 26.8 ± 0.3‰). The uniform and low carbon isotope values of red galman smithsonite are unusual for supergene carbonate-hosted deposits and indicate the predominance of a single organic carbon
source. Smithsonite from white galman has a more variable, slightly more positive carbon isotope (−2.9‰ to −7.4‰), but broadly similar oxygen isotope composition
(26.8‰ to 28.9‰). The relationship of the white galman ore with the hydrothermal system responsible for OBD II and sulfide generation is still uncertain. The most important paleoweathering
events took place in both Lower and Upper Silesia during Late Cretaceous up to Paleogene and early Neogene time. During this
period, several short-lasting emersions and intense weathering episodes facilitated the formation of sinkholes in the Triassic
carbonate rocks and the oxidation of sulfide orebodies through percolating meteoric waters. These phenomena may have lasted
until the Middle Miocene. 相似文献
16.
17.
Hypogene Zn carbonate ores in the Angouran deposit,NW Iran 总被引：1，自引：0，他引：1
Maria Boni H. Albert Gilg Giuseppina Balassone Jens Schneider Cameron R. Allen Farid Moore 《Mineralium Deposita》2007,42(8):799-820
The world-class Angouran nonsulfide Zn–Pb deposit is one of the major Zn producers in Iran, with resources estimated at about
18 Mt at 28% Zn, mainly in the form of the Zn carbonate smithsonite. This study aims to characterize these carbonate ores
by means of their mineralogy and geochemistry, which has also been extended to the host rocks of mineralization and other
local carbonate rock types, including the prominent travertines in the Angouran district, as well as to the local spring waters.
Petrographical, chemical, and stable isotope (O, H, C, Sr) data indicate that the genesis of the Zn carbonate ores at Angouran
is fairly distinct from that of other “classical” nonsulfide Zn deposits that formed entirely by supergene processes. Mineralization
occurred during two successive stages, with the zinc being derived from a preexisting sulfide ore body. A first, main stage
of Zn carbonates (stage I carbonate ore) is associated with both preexisting and subordinate newly formed sulfides, whereas
a second stage is characterized by supergene carbonates (Zn and minor Pb) coexisting with oxides and hydroxides (stage II
carbonate ore). The coprecipitation of smithsonite with galena, pyrite and arsenopyrite, as well as the absence of Fe- and
Mn-oxides/hydroxides and of any discernible oxidation or dissolution of the sphalerite-rich primary sulfide ore, shows that
the fluids responsible for the main, stage I carbonate ores were relatively reduced and close to neutral to slightly basic
pH with high fCO2. Smithsonite δ18OVSMOW values from stage I carbonate ore range from 18.3 to 23.6‰, while those of stage II carbonate ore show a much smaller range
between 24.3 and 24.9‰. The δ13C values are fairly constant in smithsonite of stage I carbonate ore (3.2–6.0‰) but show a considerable spread towards lower
δ13CVPDB values (4.6 to −11.2‰) in stage II carbonate ore. This suggests a hypogene formation of stage I carbonate ore at Angouran
from low-temperature hydrothermal fluids, probably mobilized during the waning stages of Tertiary–Quaternary volcanic activity
in an environment characterized by abundant travertine systems throughout the whole region. Conversely, stage II carbonate
ore is unambiguously related to supergene weathering, as evidenced by the absence of sulfides, the presence of Fe-Mn-oxides
and arsenates, and by high δ18O values found in smithsonite II. The variable, but still relatively heavy carbon isotope values of supergene smithsonite
II, suggests only a very minor contribution by organic soil carbon, as is generally the case in supergene nonsulfide deposits. 相似文献
18.
《Chemie der Erde / Geochemistry》2014,74(3):393-406
Oxidation zones of ore deposits offer valuable insights into the long-term fate of many metals and metalloids. In this work, we have studied a paleo-acid rock drainage (ARD) system – the oxidation zone of Mississippi-valley type Zn–Pb deposits near Olkusz in southern Poland. The ARD systems exhausted their acid-generating capacity and have come almost to the conclusion of the mineral and geochemical transformations. Primary pyrite, marcasite, galena and sphalerite have been decomposed but the acidity was neutralized by the abundant carbonate host rocks. Zinc is stored in smithsonite, hemimorphite, and Zn-rich sheet aluminosilicates. Some of these minerals formed simultaneously with the oxidation zone but some precipitated in the soils in situ, thus documenting the mobility of Zn, Al, and Si in the soils. Iron oxides are represented mostly by goethite, either well-crystalline or nanocrystalline, as determined by a combination of powder X-ray diffraction, micro-X-ray diffraction, and Mössbauer spectroscopy. Iron oxides bind a substantial amount of arsenic, to a lesser extent also zinc, lead, and cadmium, as shown by electron microprobe analyses and sequential extractions. The X-ray absorption spectroscopy data of the local environment of arsenic in goethite suggest the existence of bidentate mononuclear complex, in addition to the more common bidentate binuclear complex. These results suggest that arsenic is incorporated in the crystal structure of goethite, in addition to adsorbed to the surface of the particles or occluded in the voids and pores. Zinc is bound in goethite as a mixture of tetrahedrally and octahedrally coordinated cations. This study shows that the mature system binds the metals from the primary sulfides relatively strongly. Yet, some release of the metals was observed in this study, either in the laboratory (by sequential extractions) and in nature (e.g., neoformed Zn phyllosilicates). The physical conditions in the oxidation zone and on the surface are largely similar but the metals, to a certain extent, are still mobile in the soils. We may speculate that their mobility near the surface, in the mining waste, may be enhanced by a higher water/rock ratio than in the oxidation zone. This result implies that although the studied material is relatively benign, it still has a potential to cause local environmental problems. 相似文献
19.
银多金属矿床中黝铜矿族银硫盐矿物的特征及其意义 总被引：10，自引：0，他引：10
在国内外几个不同成因类型的银多金属矿床内产出的黝铜矿族银硫盐矿物中,除朗达矿床见有砷黝铜矿和含银砷黝铜矿外,较普遍共同发育有黝铜矿、含银黝铜矿和银黝铜矿、而后两者是最主要或主要的工业银矿物之一。按国际矿物学协会新矿物及矿物命名委员会的矿物命名原则,黝铜矿族矿物所含的Ｆｅ、Ｚｎ、Ｈｇ、Ｃｄ、Ｍｎ等不可作为矿物种的命名元素。蔡家营矿床的含银黝铜矿和银黝铜矿以Ｆｅ、Ｚｎ含量近似而有别于其余矿床的富Ｆｅ贫 相似文献
20.
四川石棉金矿床中的黝铜矿族矿物 总被引：3，自引：0，他引：3
四川石棉西部碳酸盐岩系中的金矿床产于泥盆系中统,受层间蚀变破碎带控制。其中分布有为数较多的黟同矿族矿物,与黄铁矿、黄铜矿、方铅矿、闪锌矿和Ａｕ－Ａｇ系列矿物共同组成矿石的矿物组合和Ａｕ－Ｃｕ－Ａｇ－Ｐｂ－Ａｓ－Ｓｂ－Ｂｉ的元素组合。电子探针分析表明黝铜矿族矿物有同铜矿、黝铜矿、砷黝铜矿和锌砷黝铜帮等,其中,Ｆｅ－Ｚｎ、ＡｓＳｂ之间分别呈完全类质同象。在垂向上,黝铜矿的成分自上而下由富锌锑向富铁砷演 相似文献