Production of a residual gravity field map for Tasmania and some implications

Abstract

The substantial gravity data base in Tasmania has been used to formulate a regional crustal model. This was derived by array modelling techniques for geological sources of crustal scale. A simultaneous solution for mantle, basement and granite forms was created by this means within a framework of realistic and internally consistent assumptions. The regional field derived from this geological model (including the ocean basins) is not dependent on any filtering or smoothing procedure and thus the magnitude and sign of any residuals is absolute. The residual map was produced by removing the effect of the crustal model at individual data points. The resultant map enables detailed and reliable modelling of upper crustal features as well as revealing crustal character hitherto concealed beneath post Carboniferous cover. An important example of the value of the residual separation is shown by the structural relationships exposed in NE Tasmania which involve gold mineralisation.