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  • 51. Schlatter, Denis
    et al.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jonsson, Rolf
    Barrett, T.
    Volcanic and chemical stratigraphy of the Petiknäs South Zn-Cu-Au-Ag-Pb VMS deposit, Skellefte district, Sweden2004Ingår i: The 26th Nordic Geological Winter Meeting: abstract volume / [ed] Joakim Mansfeld, Uppsala: Geological Society of Sweden , 2004, s. 151-Konferensbidrag (Refereegranskat)
  • 52. Schlatter, Denis
    et al.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jonsson, Rolf
    Boliden Mineral AB.
    Barrett, T. J.
    Stratigraphy of the Petiknäs South volcanic-hosted massive sulphide deposit, Skellefte district, Sweden2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Petiknäs South VMS deposit in the eastern part of the early Proterozoic Skellefte mining district contained 6 Mt of Zn-Cu-Pb-Au-Ag ore prior to mining. The deposit occurs on the southern limb of a major anticline, dips subvertically, and youngs southwards. The main alteration minerals are sericite, chlorite, quartz, carbonate, talc and carbonate. Two cross sections and one plan section have been constructed on the basis of detailed logging of 35 drill cores, 400 whole-rock analyses and 100 thin sections. Chemostratigraphic units were identified using lithogeochemical techniques. Excluding post-ore andesite sills, the north to south sequence is: feldspar-porphyritic rhyolitic sill; C and B ore lenses hosted by rhyolitic tuffaceous sandstone; andesitic pumiceous mass flows; felsic and intermediate tuffaceous sandstones and siltstones hosting the D and A ore lenses; and a fault followed by rhyodacitic feldspar-quartz porphyry. Prior to andesite sill injection, the C and B ores formed a single massive sulphide lens within a thin interval of rhyolitic volcaniclastic rocks. The D and A ores formed at a stratigraphically higher level, in an interval of alternating rhyolitic and andesitic gravity flow deposits. Weakly altered feldspar-porphyritic rhyolite sills with peperitic margins were then intruded into the felsic volcaniclastic rocks directly below the C+B ore lens. In summary, the two main horizons of ore formation at Petiknäs South are associated with felsic volcaniclastic intervals; coherent felsic rocks occur only as slightly post-ore intrusions. Similar volcanic successions have been recognized elsewhere in the Skellefte district, e.g. at the Renström mine 3 kilometers to the east.

  • 53. Schlatter, Denis
    et al.
    Barrett, T.J.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mass changes in alteration zones of the Petiknäs South volcanic-hosted massive sulfide deposit, Skellefte district, Sweden2006Ingår i: The 27th Nordic Geological Winter Meeting, January 9-12, 2006, Oulu, Finland: abstract volume / [ed] Petri Peltonen ; Antti Pasanen, Helsinki: Geological Society of Finland , 2006, s. 142-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Petiknäs South is a producing underground mine in the eastern part of the Skellefte district and contained 6 Mt of pyritic massive sulfide ore grading 5 % Zn, 1 % Cu, 1 % Pb, 2.5 g/t Au and 105 g/t Ag prior to mining. The deposit is hosted within volcanic rocks of the Paleoproterozoic Skellefte Group and consists of several stacked ore lenses (from oldest to youngest: C, B, D and A). The mine sequence comprises coherent and volcaniclastic units of rhyolitic to basaltic andesitic composition, and post-ore andesite sills and mafic dykes. The mine stratigraphy dips subvertically and youngs consistently southwards and the volcanic rocks have been metamorphosed to greenschist facies. Application of immobile-element lithogeochemical methods to 469 samples has allowed classification of the mine sequence into a series of chemostratigraphic units, while the degree of hydrothermal alteration of these units has been quantified using mass change methods. The main alteration minerals are sericite, chlorite, garnet, quartz and locally carbonate. Intense chlorite-garnet alteration occurs immediately below the A and D ore lenses, and in the distal footwall of the C and B ore lenses. A synvolcanic felsic sill was emplaced in the proximal footwall slightly after formation of the massive sulfide lenses. Consequently, a major part of the proximal footwall is only weakly altered and zones of strong alteration are truncated by the sill. The alteration zones are interpreted as hydrothermal upflow or feeder zones. Haloes of serizitization occur around the ore lenses and are wider than the zones of chlorite-garnet alteration and alteration zones with Na2O and CaO depletions occur on a semi-regional scale, but are most intense close to the ores. Alteration zones below and around the ore lenses are characterized by large mass gains of FeO, MnO, MgO and K2O together with large mass gains or losses in silica. The latter alteration zones are approximately three times larger than the actual ore lenses, and consequently could provide a good exploration guide to ore.

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  • 54.
    Skyttä, Pietari
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Tavakoli, Saman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Dehghannejad, Mahdieh
    Juanatey, Maria Garcia
    Hübert, Juliane
    4-dimensional geological modelling of mineral belts2011Konferensbidrag (Övrigt vetenskapligt)
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  • 55.
    Spry, Paul
    et al.
    Department of Geological and Atmospheric Sciences, Iowa State University.
    O'Brien, Joshua J
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Frank, Katherine S
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Teale, GS
    Teale & Associates.
    Koenig, A
    U.S. Geological Survey, Denver Federal Center.
    Jansson, Nils
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Raat, Hein
    Boliden Mines, Exploration Department, Boliden Mines.
    Trace element compositions of silicates and oxides as exploration guides to metamorphosed massive sulphide deposits:examples from Broken Hill, Australia, and Stollberg, Sweden2015Konferensbidrag (Övrigt vetenskapligt)
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  • 56.
    Tornos, Fernando
    et al.
    Centro de Astrobiología - Consejo Superior de Investigaciones Científicas, Ctra Ajalvir km.4.5. 28850 Torrejón de Ardoz.
    Peter, Jan M.
    Geological Survey of Canada.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Conde, Carmen
    c/Vilar Formoso 66. 37008 Salamanca.
    Controls on the siting and style of volcanogenic massive sulphide deposits2015Ingår i: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 68, s. 142-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Volcanogenic massive sulphide (VMS) deposits form in subaqueous environments from circulating hydrothermal fluids heated by volcanic activity. These deposits form as sulphide mounds, stratiform exhalative and/or replacive bodies and commonly have stockwork/vein mineralization in their immediate footwall. These various “styles” are essentially facies of mineralization, each one being the product of a particular set of conditions that control the ore-forming processes and the consequent geometry and architecture (style) of the deposits. These controls include the physical and/or chemical nature of the host rocks, the temperature and composition of the hydrothermal fluids and the redox state of the depositional environment.The style of exhalative deposits is controlled by the salinity of the vented fluids and the redox state at the seafloor. Hydrothermal fluids with salinities less than twice that of seawater that vented into open, oxic oceanic environments, typically formed small mound and chimney complexes, unless they were rapidly covered by sediments or volcanic rocks. The massive sulphides were rapidly oxidized and partly dissolved by seawater. In contrast, stratiform sheet-like deposits are typically formed in anoxic bottom waters. Anoxic marine conditions were periodically of global extent, – particularly prior to 2.4 Ga – or of a regional nature. Local anoxic conditions can also be self-induced by the exhalation of saline and reducing hydrothermal fluids that ponded in bathymetric depressions such as second- or third-order basins to form a brine pool. These exhalative systems may have been initiated as chimney vent complexes and subsequently overlain by stratiform sulphides formed under the self-induced anoxic conditions. Deposits formed in anoxic environments can be significantly larger than those in oxic settings, and this is attributed to several factors that include longer-lived hydrothermal circulation, more efficient sulphide precipitation and reduced or inhibited oxidation thereof.Replacement of volcanic and sedimentary strata by sulphide typically occurs within the feeder zones beneath the exhalative mineralization. However, successions with abundant porous, permeable and/or reactive rocks such as glassy and/or pumiceous volcaniclastic rocks, and in some cases limestone, favoured the development of large replacive deposits, that may have had little surficial expression on the sea floor.VMS deposits at spreading centres within oceanic crust formed almost exclusively as mounds. Most of them have not been preserved, likely due to oxidation of the sulphides in the prevailing oxic environment and/or destruction of oceanic crust during subsequent subduction. Intra-continental rifts, arc rifts and back-arc rifts commonly have more complexity in their structure, and facies architecture and environments and can host all styles of VMS mineralization. In these settings, early extension favoured the formation of restricted basins with ideal conditions for the onset of hydrothermal activity and development of anoxic bottom waters, whereas in mature rifts the conditions were less conducive for the formation of regionally extensive anoxic environments. Formation of replacive deposits was permissible in all settings with porous or reactive subsea-floor strata. Replacive mineralization is the most likely to be preserved in the geological record due to the sulphides being physically shielded from oxidative weathering and mechanical erosion at the seafloor.The various styles of VMS mineralization can rarely be distinguished using a single criterion; in most cases multiple criteria are required.Mound style mineralization is distinguished by: (a) mound- or lens-shaped morphology; (b) presence of chimney fragments; (c) presence of abundant sedimented sulphide breccias; (d) location on a stratigraphic boundary (ore horizon); and, (e) association with a thin horizon or thicker stratigraphic interval of fine-grained clastic rocks (e.g., shale, mudstone) that accumulated at slow sedimentation rates.Stratiform exhalative mineralization is distinguished by: (a) sheet-like morphology prior to deformation; (b) presence of fine-grained clastic host rocks that accumulated at relatively slow rates (e.g., mudstone); (c) presence of local or extensive planar stratification.Replacive mineralization is characterized by: (a) irregular geometry and distribution of sulphide bodies; (b) gradation from massive sulphides to semi-massive sulphides and disseminated mineralization with relict textures of the host rock; and, (c) originally pumiceous, glassy or reactive host rocks emplaced at high depositional rates (mass flow deposits, lavas, carbonate-altered mass flow deposits) or limestone.One deposit or district may comprise two or more of these main styles of mineralization. In many cases the main styles of VMS mineralization present in a particular region can be predicted from examination of the facies architecture and depositional environments of the host succession. Recognition of the style(s) of mineralization that occur in a particular basin or mineral belt enables exploration models to be improved and should influence the strategy of exploration for VMS deposits.

  • 57.
    Weihed, Pär
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Overview of Porphyry-Style Cu-Au and Mesothermal Gold Deposits in the Skellefte District2004Ingår i: Svecofennian Ore-Forming Environments Field Trip Volcanic-associated Zn-Cu-Au-Ag and magnetite-apatite, sediment-hosted Pb-Zn, and intrusion-associated Cu-Au deposits in northern Sweden, Littleton, Colorado: Society of Economic Geologists, 2004, s. 51-55Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 58.
    Weihed, Pär
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Allen, Rodney
    Svenson, S. A.
    Metallogeny and tectonic evolution of the c. 1.9 Ga Skellefte marine, volcanic arc, northern Sweden2000Ingår i: Volcanic environments and massive sulfide deposits / [ed] J. Bruce Gemmell; June Pongratz, Hobart: Colonialism and its Aftermath, University of Tasmania, 2000, s. 225-226Konferensbidrag (Övrigt vetenskapligt)
12 51 - 58 av 58
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