Zur Geologie des neuentdeckten Jakobsit—Braunit— Hämatit—Mangansilikat‐Lagers Slöjdartorp im Nybergetfelde in Zentralschweden

Publisher Website
Google Scholar
Abstract
Herrn Professor Dr. O. H. Ödman zum 65. Geburtstage gewidmet. Koark, H. J.: Zur Geologie des neuentdeckten Jakobsit—Braunit—Hämatit— Mangansilikat‐Lagers Slöjdartorp im Nybergetfelde in Zentralschweden. Geologiska Föreningens i Stockholm Förhandlingar. Vol. 92, pp. 388–401. Stockholm, September 30, 1970. The newly stricken Slöjdartorp ore of the Nyberget field in Central Sweden is described briefly. Two types of ore are identified: 1) bedded jacobsite— braunite—hematite ore with urbanite, rhodonite, spessartine, dannerite, rich‐terite, manganophyllite, piemontite, baryte, Mn‐calcite, felspars, quartz, and 2) bedlike to lens‐shaped hematite—spessartine—rhodonite skarn. These manganese ores are associated with manganese‐poor jaspilitic iron ores, partly with lateral transitions. In the manganese ores the ratio Mn:Fe is 1:1. Geochemical key elements are Mn, Fe, Ba, Sb. The wall rocks from the foot wall are: cordierite and sillimanite gneisses — soda leptites with hematite jaspilites — manganese iron ores and skarns with intercalations of alkali‐rich metatuffites — manganese leptite — potassium leptites. Various metamorphic intermediate to basic dikes as well as pegmatites transversed the series. The ores and the wall rocks are polymetamorphic. The latest progressive facies is the amhibolite‐cordierite facies (sillimanite—cordierite—muscovite—almandine subfacies). Tectonite facies is rare identified, only in areas with cleavages and/or shear axes. Locally the ores and rocks have undergone chemical rearrangements during diagenesis and regional metamorphism (Svionian (I) and Late Svionian (II) reaction skarns). Segregation veins contain rhodonite, spessartine, urbanite, braunite, hematite, jacobsite, baryte, richterite, rhodochrosite, sphene, felspars, St—Mn—Fe‐silicates, quartz. There are only slight signs of mechanical rearrangements. A metasomatic sulfide formation (?diagenetic or metamorphic) in the manganese ores contains pyrite, some chalcopyrite and traces of sphalerite. The bedded character of the deposit, the sedimentary‐volcanic environment, the situation of the ores in the zone of change from sodic to potassic leptites as well as the presence of alkali‐rich metatuffites indicate a hydrothermal‐sedimentary genesis of the ores.

This publication has 1 reference indexed in Scilit: