Fluid inclusion and stable isotope studies on some Caledonian sulfide-bearing veins in Sweden

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doi: 10.2113/gsecongeo.79.7.1736
Authors:Johansson, ©<U+0085>ke
Author Affiliations:Primary:
Stockholm Univ., Ore Res. Group, Stockholm, Sweden
Other:
Univ. Trondheim, Norway
Volume Title:special issue devoted to massive sulfide deposits of the Appalachian-Caledonian Orogen
Volume Authors:Gair, Jacob E., editor; Vokes, Frank M.
Source:Economic Geology and the Bulletin of the Society of Economic Geologists, 79(7), p.1736-1748; Symposium on Correlation of Caledonian stratabound sulfides, Ottawa, ON, Canada, Sept. 1983, edited by Jacob E. Gair and Frank M. Vokes. Publisher: Economic Geology Publishing Company, Lancaster, PA, United States. ISSN: 0361-0128
Publication Date:1984
Note:In English. 34 refs.; illus. incl. 3 tables, geol. sketch map
Summary:Sulfur isotope measurements have been made on sulfides from Caledonian sulfide-bearing calcite veins in the Precambrian basement of the Swedish Caledonides and from sulfide-bearing quartz veins within the Caledonides in Sweden. The calcite veins show a narrow range in U+00ceþ34S of the sulfides, between -7 and +1 per mil vs. CDT, whereas the quartz veins show a much wider range, from -12 to +14 per mil. A more detailed study of sulfide sulfur in one quartz vein deposit, Nasafjl̃l, however, shows little variation within that deposit, with most U+00ceþ34S values in a narrow range between 7 and 10 per mil. No vein deposits with sulfur as heavy as that of the sandstone-hosted impregnation ores of Vassbo and Laisvall (U+00ceþ34S = 17-28) have been found in this study.Fluid inclusion data from the ©U+0085kerlandet calcite vein suggest that it formed at temperatures between 75℗ʻ and 165℗ʻC (not corrected for pressure) during mixing between two hot saline brines. Carbon isotope values, with U+00ceþ13C of the calcite close to -15 per mil vs. PDB, point to a significant contribution of reduced carbon to the ore-forming fluid. These data are used to reconstruct the chemical environment in terms of pH and oxygen fugacity for the formation of the ©U+0085kerlandet deposit. A similar tentative reconstruction is also made for the Nasafjl̃l quartz vein deposit.The sulfur in the calcite veins is probably derived from leaching of sulfides in the granitic basement, in contrast to the organic reduction of seawater sulfate which has been proposed for the sandstone-hosted impregnation ores. Sulfide sulfur in the quartz veins may be a mixture of sulfide and sulfate sulfur leached both from the granitic basement and the overlying metasediments and metavolcanics of the Caledonian nappes, the sulfate being inorganically reduced through reactions with wall rocks prior to sulfide precipitation. The sulfur isotope data thus suggest different processes to have been involved in the formation of the different types of deposits. Together with lead isotope data, the sulfur data show that the Caledonian quartz and calcite veins in Sweden are not directly related to the Caledonian strata-bound ores but form distinct ore types of their own. [G.J.N.]
Subjects:C-13/C-12; Caledonian Orogeny; Carbon; Economic geology; Fluid inclusions; IGCP; Inclusions; Interpretation; Isotopes; Lead-zinc deposits; Massive deposits; Metal ores; Mineral deposits, genesis; O-18/O-16; Ore-forming fluids; Orogenic belts; Orogeny; Oxygen; P-T conditions; Paleosalinity; Paleozoic; S-34/S-32; Stable isotopes; Sulfides; Sulfur; Veins; Volcanism; Caledonides; Europe; Scandinavia; Sweden; Western Europe; Appalachian-Caledonian Orogen; Central Sweden
Abstract Numbers:85M/2521
Record ID:1985005678
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists
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