Lycksele structure in northern Sweden: Result of an impact?

• The Lycksele structure in northern Sweden is a large circular structure with a diameter of approximately 130 km. The structure has been defined from a combined analysis of topography, gravity, and magnetic data and is characterized by a circular system of faults, arc-shaped contacts between rocks, a quasi-circular system of downfaulted lowdensity granitic rocks, and an uplift of high-density rocks in the center. On the basis of ages of granite intrusions and a thrust zone that is cut by faults of the ring, together with paleomagnetic data, the age of the structure is between 1.80 and 1.26 Ga. The Bouguer gravity anomaly is similar to that associated with other known large impact structures on Earth. The rim of the structure, defined from the gravity gradients, magnetic data, and topography, is not restricted to specific rock types but cuts regional geologic structures as well as smaller intrusions, which may be expected for an impact structure in Precambrian deformed target rocks. Therefore, an impact origin seems most plausible for this structure, but to confirm this idea we need identifications of shock metamorphic features in the rocks.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geofysik (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geophysics (hsv//eng)

Nyckelord

Applied Geophysics

Tillämpad geofysik

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