The geological interpretation of the Slidre positive gravity anomaly.

Abstract

A positive gravity anomaly that occurs in Slidre has an amplitude of 53 mgal and can be separated into two parts. The top of the disturbing body causing the anomaly cannot be deeper than 4 km. Gabbros and mafic gneisses are exposed in windows of Precambrian rocks which are overlain by about 1000 m of Cambro-Ordovician sedimentary rocks. The cause of the anomaly is probably a body of mafic rocks lying at the upper surface of the Precambrian basement. The model calculated to satisfy the observed anomaly consists of a 2.5-km-thick slab underlain by a 10.5 km deep column. This model is interpreted to represent a sheet- or saucer-like mafic intrusion, a lopolith, that has a thick, deep feeder.