NOTES ON THE GEOLOGY OF THE SWEDISH 



MAGNETITES 



BY D. H. NEWLAND 



The general features of the Precambric geology of Sweden are 

 outlined in the paper by Prof. J. F. Kemp which should be con- 

 sulted in connection with the following notes on some of the Swe- 

 dish districts notable for their magnetite deposits. Inasmuch as 

 these ores have likewise an important place in the mining activity 

 of our own State and much uncertainty surrounds the relation- 

 ships and origin of the local deposits, it is thought that a brief 

 discussion comparing the two series of occurrences, though so far 

 removed from each other, may well be presented here. The notes 

 are based on observations of the writer while a participant in the 

 excursions of the International Geological Congress during the 

 months of August and September 1910. The excellent guides to 

 the different mines, prepared by the Swedish geologists for the use 

 of the visiting members, have been freely consulted for details, as 

 have also some of the reports and monographs from other sources. 



The iron industry of Sweden, as is well known, derives its raw 

 material from magnetite deposits in the Precambric rocks. In this 

 respect the country stands practically by itself among the more 

 important iron producers of Europe; for elsewhere the ores chiefly 

 represented are hematite and limonite, or occasionally carbonate, 

 associated with rocks of much later age. The magnetites are con- 

 tained in crystalline schists and certain igneous rocks of acid com- 

 position that are all assigned to the Precambric, though they jnay 

 belong to widely variant horizons of the series. It is upon these 

 ores and their features of occurrence, suggestive in some instances 

 of the magnetites found within the -Adirondack and Hudson River 

 gneisses, that attention will be fixed. 



Sweden also possesses deposits of titaniferous magnetites, quite 

 analogous to those occurring in the Adirondack gabbro-anorthosite 

 areas. One occurrence at Taberg, in southern Sweden, is of large 

 size and has been mined to some extent in the past, but it is low 

 grade, resembling in composition rather the magnetite-silicate mix- 

 tures of the smaller gabbro intrusions than the larger Adirondack 

 deposits like those of Lake Sanford. There are many occurrences 



107 



