A geomagnetic induction study in the north east of Tasmania.

During the period in between February 1978 until October 1979, a geomagnetic variation study by means of eleven temporary field stations has been conducted covering the area of Launceston quadrangle, Tasmania Geological Atlas Series, sheet SK 55-4, scale 1 : 250 000. The study area is situated between latitude 41 °00 and 41 °45 south and between longitude 146 ° 15 and 148 °00 east, with a total area of about 12 700 sq. km. The aim of this study is to record and analyse the behavior of geomagnetic variations which are related to lateral changes of electrical conductivity structure. The coast effect similar to the one that was established in Hobart ( Parkinson, 1962 ) is found in this area for longer periods greater than 64 minutes. And an anomalous local high conductivity zone is indicated by the directions of induction vectors at periods less than or equal to 48 minutes. This anomalous conductive zone is interpreted as caused by deep lateral variation of conductivity of sedimentary rocks ( o- = 0.54 x 10-1 S.m-1 ) with ages between Cambrian and younger and Devonian granodiorite (o- = 0.54, x 10-3 S.m-1), both being covered by surface high conductive layer ( o- = 0.11 S.m-1) that extends from east of Deloraine to west of Scottsdale. The occurence of a mineralized zone between Nabowla, Scottsdale and Tayene agrees with the direction of induction vectors at those stations.