The Geometry of a Gabbro Unit Intruded in a Granitic Body, Billdal, Sweden
Abstract
The Billdal area is a part of the Kungsbacka bimodal suite characterized by alternating felsic and
mafic intrusions in a N-S trending band stretching from Kungsbacka in the south to Trollhättan
in the north. The aim of this study is to better understand the large-scale geometries of one of
these gabbro intrusions in a 25 km2 area around Billdal and Hällesås, south-western Sweden. To
do this, a gravimetric survey is conducted in order to interpolate the gravity anomalies over a
wider area. A profile of this interpolation is compared with a simulated gravity profile in
ModelVision. A bedrock profile based on mapped outcrops is also created to verify the result
and to attempt to calculate the shape of the intrusion. The gravity simulation shows all the signs
of being a deep magma conduit and an almost horizontal sill, but the density of the theorized
magma conduit needs to be higher than previously assumed. No gravitational signs of a massive
gabbro structure can be found over the area presumed to house the sill, and no other magma
conduits have been identified in the study area. The bedrock profile indicates the same
structure as the simulated gravity profile.
Collections
View/ Open
Date
2023-08-18Author
Birgerheim, Helge V.
Series/Report no.
B1243
Language
eng