Estimates of Direction and Intensity of the Palaeomagnetic Field from the Mugga Mugga Porphyry, Australia

摘要: Summary The mean direction of NRM in Mugga Porphyry (late Silurian or early Devonian intrusion near Canberra) is calculated to have declination 16° E and inclination -40° with Fisher precision estimate (k) equal 43. This corresponds a palaeomagnetic pole at 158° W, 71° N. Alternating field thermal demagnetization, as well divergence the from present direction, indicate stability that primary thermoremanence. The intensity (M) which destroyed by heating zero through particular temperature range compared (M′) TRM acquired cooling Earth's same range. By studying different intervals, several estimates M/M′ were obtained each specimen. If arbitrary correction made for effects alteration above 550°C, was found be constant within factor about 2 over all intervals four samples. suggests serious decay has not occurred, M may close original intensity. Assuming proportional applied field, it estimated time when intruded approximately quarter its A large number required before any ancient can made; this likely apply future studies palaeointensity.