Visualisation of Plate Reconstructions for the Archaean: an example from the Superior Craton

English Abstract:

Investigation of deep time plate tectonic reconstructions and of the blocks they represent is possible, using modern software tools and a number of simple approximations for the spatial context of the various blocks. Although not spatially accurate in a true global geographic setting, relative spatial and time constraints can be honoured. This has the advantage that one can investigate various reconstruction settings and scenarios so as to develop a better understanding of the geological evolution. Reconstructions reflect palaeolatitude derived from palaeomagnetic data, where available, together with structural vergence directions as a way to move apart crustal blocks. GPlates or Paleogis software platforms may be used for representation, so permitting one to illustrate changing location of igneous and metamorphic activity (as points for individual geochronology samples and as polylines for dyke swarms); changes in geochemical signature relative to location and time; location of different styles of ore deposit and mineralisation and any other features that can be captured in GIS with time attribute information. In cases where lithostratigraphic attribute information are available from digital geological maps, it is also possible to use these in continuously varying time or as a succession of integrated time-slice maps. Background raster images reflecting regional gravity, aeromagnetics or radiometrics move with the associated domain blocks so facilitating the matching of features across blocks in cases where alternative reconstructions may need to be considered. In the case of the Superior Craton, utilisation of these techniques helps emphasise the unique isotopic character of the Abitibi domain relative to other blocks, requiring a protracted depleted source in its lithosphere for millions of years prior to the development of volcanic-hosted massive sulphide mineralisation at about 2700 Ma, quite unlike the situation in the other terrains of the craton.