Open AccessReflection seismic investigations in the Dannemora area, central Sweden: Insights into the geometry of polyphase deformation zones and magnetite‐skarn deposits
Author(s) -
Malehmir Alireza,
Dahlin Peter,
Lundberg Emil,
Juhlin Christopher,
Sjöström Håkan,
Högdahl Karin
Publication year - 2011
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jb008643
Subject(s) - geology , seismology , fault (geology) , reflection (computer programming) , tectonics , deformation (meteorology) , overburden , polyphase system , skarn , mining engineering , hydrothermal circulation , oceanography , electronic engineering , computer science , engineering , programming language , fluid inclusions
The Bergslagen region is one of the most ore prospective districts in Sweden. Presented here are results from two nearly 25 km long reflection seismic profiles crossing this region in the Dannemora mining area. The interpretations are constrained by seismic wave velocity measurements on a series of rock samples, cross‐dip analysis, prestack time migration, and swath 3‐D imaging, as well as by other available geophysical and geological observations. A series of major fault zones is imaged by the seismic data, as is a large mafic intrusion. However, the most prominent feature is a package of east‐dipping reflectors found east of the Dannemora area that extend down to at least 3 km depth. This package is associated with a polyphase, ductile‐brittle deformation zone with the latest ductile movement showing east‐side‐up or reverse kinematics. Its total vertical displacement is estimated to be in the order of 2.5 km. Also clearly imaged in the seismic data is a steeply dipping reflector near the Dannemora mine that extends down to a depth of at least 2.2 km. The geological nature of this reflector is not known, but it could represent either a fluid‐bearing fault zone or a deep‐seated iron deposit, making it an important target for further detailed geophysical and geological investigations.