Why you should not use net tectonic rotation to restore paleomagnetic data from dikes

Sarah Titus, Carleton College
Joshua R. Davis, Carleton College

Abstract

Dikes do not record indications of paleohorizontal, which makes them challenging to use in paleomagnetic applications. Allerton and Vine (1987) devised a method called net tectonic rotation that restores the paleomagnetic data from dikes to a reference direction by assuming that dikes were intruded vertically. The approach usually yields two possible estimates of the initial strike of dikes, which are then often used in tectonic reconstructions that rely on ophiolites.

Using numerical experiments, we show that the net tectonic rotation method can introduce geometric artifacts into the interpretation of initial dike strikes. The severity of the artifact depends on the initial dike attitude, but is worst in cases where dikes are approximately perpendicular to the paleomagnetic reference direction. Further, the results become more distorted with increasing values for the reference inclination. We show examples from several natural systems, where there may be alternative approaches to extract information from dike paleomagnetic data without relying on net tectonic rotation.

Session

Deformation of mafic or ultramafic rocks