The Bälinge conglomerate in northern Sweden reinterpreted as a magmatic, hydraulic breccia

• Published in: Terra Nova
• Main Authors: Wikström, Anders, Mellqvist, Claes, Barbarid, Bernard
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Bälinge; Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1365-3121.1996.tb00740.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-3121.1996.tb00740.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3121.1996.tb00740.x

ABSTRACT The Bälinge conglomerate has played a key role in the lithostratigraphy of northern Sweden. The conglomerate, with pebbles dominated by granodiorites and tonalites in a generally biotite‐rich matrix, borders volcanic rocks with unclear relative age relationships. In nearby areas these volcanites have been intruded by plutonic rocks (c. 1.9 Ga) which are similar to the pebble material. On these grounds, the conglomerate has been regarded as younger than the volcanic rocks and an important marker in the geological evolution of the region. In this preliminary study, it is suggested that the features displayed by the Balinge conglomerate are not compatible with an epiclastic origin. On the contrary, they indicate that this rock represents a hydraulic breccia where the roundness of the granitoid ‘pebbles’ has resulted from erosion in a fluidised, heterogeneous and magmatic environment. In the actual area the ‘conglomerate’ must thus be dismissed as a stratigraphic marker horizon. It belongs to the early Svecofennian evolution.