The palaeomagnetism and magnetic properties of Scottish Permo-Carboniferous quartz dolerite dykes at 22 sites were investigated. The measurements were performed using apparatus constructed and tested for this project. Alternating field (AF) demagnetization and thermal cleaning reveal, in all of the samples studied, the presence of a stable reversed NRM. The mean AF cleaned direction is 181.5 N,-13.3 which corresponds to a north pole position of 41 N, 174 E while the mean direction after thermal cleaning is 179.8 N,-15.5 which gives a north pole position of 42 N, 176 E. Baked country rocks were collected, from 45% of the sites and there is general agreement between the cleaned (AF and thermal) directions of baked and baking rocks at each site. This suggests that in both cases the remanence is the primary thermo-remanent magnetization (TRM) acquired during the dyke formation. Microscopic observations and Gurie point measurements indicate that titanomagnetite is the remanence carrier (dyke sample). A stable normal component of remanence almost antiparallel to that of the primary component (reversed) was isolated in 90% specimens from one of the sites (site 5) during AF treatment. The physical properties of dyke specimens collected from this site (with possible exceptions of Gurie temperature and direction of NRM) show no significant difference to those of dyke specimens at the other sites. Possible origins of the normal component were discussed. It is suggested that the normal component arises as a consequence of remagnetization (possibly by chemical process) over a time period during which the earth's magnetic field had changed its polarity. An anomalous magnetic profile (i.e. negative trough on the north) across an unexposed dyke was also investigated by drilling samples 3 metres below the soil surface and the results suggest that its primary stable remanence (reversed direction) is small compared with the component of magnetization induced by the present earth's magnetic field.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:593390 |
| Date | January 1981 |
| Creators | Samsudin, Abdul Rahim |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU320380 |
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