A palaeomagnetic study of a Caledonian ophiolite

Abstract

A total of 89 sites have been sampled for palaeomagnetic studies from the Caledonian ophiolite complex of northeast Shetland (60.7d°N 359.2°E) and a post-ophiolite emplacement suite of lamprophyre dykes. Of these only 35 sites from the ultramafite facies of the complex yielded statistically significant results. These sites define three distinct populations of magnetization directions which correspond to south palaeomagnetic poles at 47.2°S 244.2°E (A), 18.0°S 323.4°E (B), and 35.0°S 351.1°E (C). Of these only the C remanence can be assigned an unambiguous age of mid-Carboniferous; the ages of the other two poles remain ambiguous due to the uncertainty in the APW path and the complexity of the ophiolite history. Nevertheless palaeomagnetism is shown to be successful in detecting low temperature, low pressure, alteration events that have affected the complex and which hitherto have gone undetected.