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  • 1
    Electronic Resource
    Electronic Resource
    Diagenetic processes and the mineralization in the triassic of Central England (1983)
    Springer
    Mineralium deposita 18 (1983), S. 365-377 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Continental red beds are the host rocks of a characteristic style of mineralization which suggests a genetic link between red bed formation and ore formation. Samples of unmineralized and mineralized Triassic sediments from Central England have been studied sedimentologically, petrographically and geochemically with the aim of clarifying this link which may provide valuable guides for exploration. On the basis of sedimentological and petrographic observations it is suggested that these red beds were formed as a result of diagenetic alteration whereby detrital silicates and oxides are progressively dissolved and the iron released is deposited as hematite. A model for mineralization is proposed involving the release of trace metals from detrital minerals during diagenesis, their retention in saline interstitial solutions, migration to suitable sites of precipitation and deposition by reaction with trapped hydrocarbons or reduced sulphur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206485
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  • 2
    Electronic Resource
    Electronic Resource
    Book reviews (1996)
    Springer
    Mineralium deposita 31 (1996), S. 250-252 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204035
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  • 3
    Electronic Resource
    Electronic Resource
    The zircon-thorite mineral group in metasomatized granite, Ririwai, Nigeria 2. zoning, alteration and exsolution in Zircon (1988)
    Springer
    Mineralogy and petrology 39 (1988), S. 21-37 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Zirkon aus dem Ririwai-Biotit-Granit und aus seinen albitisierten und vergreisten Varietäten wurde mit Auflicht-Mikroskopie, Backscatter Mikroskopie (BSE) und Mikrosonde untersucht. Die drei Gesteinstypen zeigen unterschiedliche Zirkonarten. Im Biotit-Granit sind manche Zirkonkörner korrodiert. Fleckige Alteration tritt sowohl bei Zirkonen aus dem Biotit-Granit wie auch in vergreisten Gesteinen auf. Dunkle (niedrig reflektierende) Flecken sind an Spurenelementen angereichert (bis zu 7,9 Gew.% ThO2, 4,0% UO2 und 4,8% Y2O3). Aus den analytischen Daten (niedrige Totale) und ihrem dunklen Erscheinen im BSE-Bild kann vermutet werden, daß sie metamikt sind. Dies deutet weiters auf das Vorhandensein von submikroskopischen Leerstellen hin. Die dunklen Flecken führen vermutlich auch Hydroxyl-Anionen. Die albitisierten Gesteine führen Zirkone mit U-angereicherten Kernen (bis 6,1 Gew.-% UO2), Hf-reichen Rändern (bis 14,0 Gew.-%1 HfO2) und mit einer feinen Wachstumszonierung des Hf-Gehaltes. Es handelt sich hierbei um unveränderte Körner, welche aus metasomatischen Fluida entstanden sind. Mineralogische Daten weisen darauf hin, daß die Fluida fluorführend waren. Fluorid-Komplexe haben wahrscheinlich eine große Bedeutung für den Transport der Elemente. Zahlreiche kleine Thorit-Einschlüsse in bestimmten Teilen der Zirkonkörner werden hier als Entmischungen (gefolgt von metastabilem Wachstum von Th, U-reichem Zirkon) interpretiert.
    Notes: Summary Zircon in the Ririwai biotite granite, and its albitized and greisenized varieties, is described by reflected-light and backscattered-electron (BSE) microscopy, and electron-microprobe analysis. The three rock-types show different features in their zircons. In biotite granite, some grains are corroded, and a patchy alteration is found which also affects zircons in greisenized rocks. Dark (low-reflectance) patches are enriched in minor elements (up to 7.9 wt% ThO2, 4.0 UO2 and 4.8 Y2O3). They are inferred to be metamict, from a combination of analytical evidence (low totals) and dark appearance in BSE images. The latter effect indicates the presence of submicroscopic voids. The dark patches are also inferred to contain hydroxyl anions. Albitized rocks have distinctive zircons with U-enriched cores (up to 6.1 wt% UO2), and Hf-enriched margins (up to 14.0wt% HfO2) with fine-scale growth-zoning of their Hf content. These grains are unaltered and are thought to have grown from the metasomatizing fluids, which the mineralogy indicates were fluorine-bearing. Fluoride complexing was probably important in the transport of the elements. A new interpretation proposed here, for numerous small inclusions of thorite in some parts of grains, is exsolution (following metastable growth of Th, U-rich zircon).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01226260
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  • 4
    Electronic Resource
    Electronic Resource
    The zircon-thorite mineral group in metasomatized granite, Ririwai, Nigeria 1. Geochemistry and metastable solid solution of thorite and coffinite (1988)
    Springer
    Mineralogy and petrology 38 (1988), S. 245-262 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung In Ririwai, Nigeria, wurde ein Biotit-Granit durch extensive Metasomatose in albitisierte, mikroklinisierte und vergreisete Gesteine umgewandelt. In Mikroklin-Gesteinen und Greisen sitzt eine Zinn-Zink-Gangvererzung! Sämtliche Gesteinstypen führen Thorit als akzessorischen Gemengteil, stellenweise mit Spuren von spätgebildetem Coffinit und Xenotim. Petrographische und Mikrosonden-Daten dieser Minerale werden präsentiert. Im Biotit-Granit erreichten die Zr-Gehalte im Thorit und Coffinit Werte, wie sie bisher noch nicht bekannt waren (25.1 Gew.-% ZrO2 im Thorit und 11.7 Gew.-% im Coffmit). In den Nebengesteinen reichen die Yttrium-Gehalte im Thorit bis 13.9 Gew.-% Y2O3, und im Coffinit bis 15.9 Gew.-%. Aus stöchiometrischen Überlegungen kann vermutet werden, daß beide Minerale OH enthalten. Petrographisch sind die Thorite aus den Nebengesteinen eindeutig definiert, und sie dürften aus metasomatischen Fluida entstanden sein. Die albitisierten Gesteine und auch einige Nebengesteine führen Thorite mit den höchsten U-Gehalten, darunter ein Beispiel mit einem kontinuierlichen Zonarbau bis zum Coffinit. Die ungewöhnlichen Mineralzusammensetzungen werden als metastabile feste Lösungen interpretiert, die aus Fluiden gebildet worden sind, welche U, Th, Y und über kurze Distanzen auch Zr transportiert haben.
    Notes: Summary At Ririwai, Nigeria, a biotite granite has suffered extensive post-magmatic metasomatism to produce albitized, microclinized, and greisenized rocks; the latter two lithologies form the wallrocks adjacent to tin-zinc vein-style mineralization. All the rock-types carry accessory amounts of thorite, locally accompanied by trace amounts of paragenetically late coffinite and xenotime. Petrographical and electron-microprobe data are presented for these minerals. In the biotite granite, thorite and coffinite range to high Zr contents (25.1 wt% ZrO2 in thorite and 11.7 wt% in coffinite), exceeding the highest values previously reported in both minerals. In the lode wallrocks, yttrium contents range up to 13.9 wt% Y2O3 in thorite and 15.9 wt% in coffinite. From stoichiometric considerations, both minerals are inferred to contain OH. Petrographically, the thorites of the lode wallrocks are distinctive, and they are interpreted as having grown from the metasomatizing fluids. The albitized rocks and some of the lode wallrocks contain the thorites with the highest U contents, including one example of continuous zoning to coffinite. The unusual mineral compositions are interpreted as metastable solid-solution ranges formed from fluids that transported U, Th, Y and, over short distances, Zr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167091
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  • 5
    Electronic Resource
    Electronic Resource
    The genesis of Cu-bearing quartz veins by metamorphic remobilization from stratiform red bed deposits, SW County Cork, Ireland (1996)
    Springer
    Mineralogy and petrology 57 (1996), S. 73-89 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Polymetallische Erzgänge (“major veins“) des westlichen Carbery Distriktes (County Cork) werden mit kleineren Gängchen (“minor veins”), die in den benachbarten, eine disseminierte stratiforme Cu-Vererzung führenden, Metasedimenten liegen, verglichen. Diese stratiformen Lagerstätten sind an nichtmarine devonische Sedimente (Old Red Sandstone), die während der hercynischen Orogenese metamorphisiert wurden, gebunden. Die Zusammensetzung der Schwefelisotope (δ34S) der Sulfide in der disseminierten Vererzung und in den kleineren Gängen variiert von −21.00 bis −5.14%0. Diese Zusammensetzung ist mit der Interpretation, daß der Schwefel in den Gängchen aus den stratiformen disseminierten Sulfiden remobilisiert wurde, die ihrerseits diagenetischbakteriogene Signatur zeigen, konsistent: Die δ345-Werte der Sulfate (Baryt) in den Gängchen variieren von + 12.3 bis + 15.7%0, was mit einer Herkunft aus Grundwässern übereinstimmt. Die Homogenisierungs-Temperaturen der FlüsBigkeitseinschlüsse in Quarz der Gängchen sind mit einem Einschluß der Fluide während des Höhepunktes der Metamorphose (300–400°C, l-3 kbar) konsistent. In den polymetallischen Erzgängen weisen die δ34S-Werte (−15.8 bis −4.2%0) auf die Remobilisation diagenetischen Schwefels, die Sauerstoff und Wasserstoffisotope auf Ausfällung aus metamorphen Wässern hin. Die berechneten δ18O-Werte liegen zwischen ca. +8 bis +13%0 die gemessenen δH-Werte zwischen −52.2 bis −27.3%0. Nicht mischbare C02-führende Fluide wurden im Temperaturbereich von 280–350°C bei Fluid-Drucken 〈 ca. 600 bar eingeschlossen. Der abgeleitete P-T Pfad wird mit spätmetamorpher Hebung, während der der Fluiddruck unter den lithostatischen Druck fiel, erklärt. Die Sulfid-führenden Gänge werden als kleinmaßstäbliche Beispiele für Wiederverteilung von Minerallagerstätten durch metamorphe Fluide gedeutet.
    Notes: Summary Polymetallicmajor veins of the West Carbery district (County Cork) are compared with the nearby stratiform-disseminated copper mineralization in metasedimentary rocks, containingminor veins (metamorphic quartz veins and veinlets). These stratiform deposits are hosted by non-marine Devonian sediments (Old Red Sandstone), metamorphosed in the Hercynian orogeny. In sulphides from the stratiform deposits and minor veins, isotopic compositions of sulphur (δ34S) range from − 21.00 to + 5.14%0, consistent with the vein sulphide being remobilized stratiform-disseminated sulphide, and the latter being of diagenetic bacteriogenic origin. Sulphate (barite), found in veins separate from the sulphides, has δ34S + 12.3 to + 15.7%0. consistent with groundwater origin. In minor-vein quartz, fluid inclusions have homogenization temperatures consistent with trapping under the estimated peak-metamorphic conditions (300–400°C, 1–3 kbar). In the major veins, sulphide δ34S (−15.8 to −4.2 0) suggest remobilization of diagenetic sulphide. Oxygen and hydrogen isotopes suggest deposition from metamorphic fluids (calculated δ18OH2O approximately + 8 to + l3%0, measured range of δD −52.2 to −27.3%0). Immiscible C02-bearing fluids were trapped in the temperature range 280–350°C with fluid pressure 〈 ca. 600 bar. The inferred pressure-temperature history is attributed to late-metamorphic uplift, with fluid pressures falling below lithostatic. The sulphide-bearing veins are interpreted as a small-scale example of redistribution of mineral deposits by metamorphic fluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161622
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  • 6
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    Bismuth-bearing assemblages from the Northern Pennine Orefield (1996)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 1996-04-01
    Description: Bismuthinite-bearing quartz veins from the Alston Block of the North Pennine Orefield are all close to, or above, the Rookhope and Tynehead cupolas of the buried Weardale Granite. They are uniform in composition and paragenesis and are earlier than the main fluorite-baryte-galena-sphalerite mineralization of the orefield. Rhythmical crystallization of quartz, chalcopyrite and minor pyrite is followed by fluorite-quartz-chalcopyrite-minor sphalerite-altered pyrrhotite mineralization. Early tin-bearing (up to 0.29 wt.% Sn) chalcopyrite encloses trace amounts of bismuthinite (Bi2S3), synchysite (CaREE(CO3)F2), argentopentlandite (Ag(FeNi)8S8) (close to being stoichiometric), pyrrhotite, cubanite and cosalite (Pb2Bi2S5), while early pyrite carries monoclinic pyrrhotite (close to Fe7S8) and tungsten-bearing cassiterite (up to 1.03 wt.% WO3). Bismuthinite is macroscopically visible and is associated with native bismuth and small, fine-grained, spherical aggregates that qualitative analysis suggests may be cosalite crystals. Synchysite and more rarely monazite, xenotime and adularia are intergrown with bismuthinite. These mineralogical data form part of the basis for an increasing awareness of the contribution of the Weardale Granite to the early phases of mineralization in the Alston Block.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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  • 7
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    Cobalt-, nickel-, and iron-bearing sulpharsenides from the north of England (1979)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 1979-09-01
    Description: SummaryWithin the Alston Orefield of the North Pennines, glaucodot and gersdorffite have been found in samples from Tynebottom Mine, Garrigill, and zoned gersdorffite has been found from Nenthead and the Great Sulphur Vein. At Scar Crag in the English Lake District, glaucodot and alloclase (the first reported occurrence in the United Kingdom) occur associated with arsenopyrite and minor cobaltite and skutterudite. The mineralogy and parageneses of these associations have been studied by ore microscopy, X-ray powder photography, and electron probe microanalysis.Electron probe microanalysis shows a considerable range in nickel content in the sulpharsenides from the Alston Orefield with a relatively constant Co:Fe ratio. Samples from Scar Crag contain no nickel but exhibit almost a complete range of Co:Fe ratios from FeAsS to CoAsS. The compositions of the Alston Orefield sulpharsenides, in particular, show them to be metastable phases when compared with data from synthetic studies. At Tynebottom Mine, glaucodot and gersdorffite overgrow arsenical marcasite, and at Nenthead and the Great Sulphur Vein, early pyrite framboids or euhedra act as cores to zoned gersdorffite crystals. The Scar Crag sulpharsenides occur in a quartz chlorite apatite vein with the glaucodot and alloclase as overgrowths on arsenopyrite.In the case of the Scar Crag association, consideration of the compositions of coexisting phases, together with precise determinations of the arsenic content of the arsenopyrites, has permitted speculation regarding temperatures and sulphur activities during ore formation. Estimated ranges are Tc. 400 °C–300 °C and aS2 ≈ 10−9–10−11 11 bar. The occurrence of the sulpharsenides in the Alston Orefield correlates with further geochemical differences compared to other Pennine ores, differences that have been linked to higher temperatures of formation and a magmatic contribution to the ore-forming fluid. The Scar Crag mineralization may be related to a postulated stock intrusion beneath Causey Pike and the geographical proximity of the Alston and Scar Crag occurrences does suggest the possibility of a genetic link.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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  • 8
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    Siegenite-bearing assemblages found at the Great Orme Mine, Llandudno, North Wales (1996)
    Mineralogical Society of Great Britain and Ireland
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    Publication Date: 1996-12-01
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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  • 9
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    Silver mineralization at Sark's Hope mine, Sark, Channel Islands (1983)
    Mineralogical Society of Great Britain and Ireland
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    Publication Date: 1983-12-01
    Description: Sark's Hope silver-lead lode, which was mined during the 1830s and 1840s cuts a Late Precambrian granite at the southernmost point of the island of Sark. The primary ore assemblage is pyrite, galena, chalcopyrite, tennantite, tetrahedrite, sphalerite, marcasite, arsenopyrite, pyrrhotine, bravoite, enargite, and the silver minerals pyrargyrite, pearceite, polybasite, and acanthite. Gangue minerals are hematitic quartz, calcite, and illite. Alteration products include chalcosine, covelline, blaubleibender covelline, limonite, malachite, azurite, cerussite, and anglesite. The generalized paragenesis is of early Fe, Co, Ni, As, and S species and later minerals of Pb, Cu, Ag, Zn, Fe, As, Sb, and S. The earliest alteration products are copper sulphides; these are followed by lead and copper carbonates and sulphates, and hydrated iron and manganese oxides. Growth zoning is a common feature of many of the ore minerals, and electron microprobe analysis shows that this is sometimes related to compositional differences. Tetrahedrite and tennantite, particularly, exhibit a wide range of compositions.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
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  • 10
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    The primary ore mineralogy of the Alderley Edge deposit, Cheshire (1982)
    Mineralogical Society of Great Britain and Ireland
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    Publication Date: 1982-12-01
    Description: The Alderley Edge deposit, Cheshire, England has been mined principally for Cu and Pb. Here, veins and disseminations occur in coarse-grained clastic sediments of Triassic age and are classified as belonging to the red-bed type of mineralization.Examination of material in polished and thin section has shown the mineralization to be multiphase. The earliest opaque phases are associated with the diagenesis of the sandstones and include authigenic anatase, plus bravoite, pyrite, and chalcopyrite within authigenic quartz overgrowths. This stage of mineralization was followed by the formation of intergrown bravoite, pyrite, chalcopyrite, sphalerite, and galena accompanied by minor amounts of Ni-Co-Fe sulpharsenides, marcasite, and tetrahedrite cementing the clastic grains. This primary assemblage has undergone extensive alteration resulting in the formation of djurleite, covelline, and blaubleibender covelline accompanied by Pb and Zn carbonates and sulphates. Later, extensive shattering of the cemented clastic grains has been infilled by supergene Cu, Pb, and Zn carbonates and sulphates, limonite, and other secondary minerals.Electron probe microanalysis of the sulphides shows the pyrite to contain significant Ni and Cu but lesser amounts of Co; the sphalerite to be an Fe-poor variety but to contain Cd, and the chalcopyrite to contain Sb. Ag is present in appreciable amounts in tetrahedrite and occurs in trace amounts in both sphalerite and chalcopyrite but not in galena. The concentration of Ag increases with the alteration of the primary sulphides to secondary sulphides. This is most clearly demonstrated by the alteration of chalcopyrite to an idaite-like phase and finally to djurleite when the Ag content increases from 0.10 to 2.35 wt. %.
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    Electronic ISSN: 1471-8022
    Topics: Geosciences
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