Regolith electrical structures associated with kimberlite dykes - an example from the Archaean Yilgarn Craton, Western Australia.

The regolith - electrical structures associated with a kimberlite located in the Yilgarn<br>Craton, Western Australia are examined. The kimberlite is hosted by a deeply<br>weathered granitic host. The saprolite associated with the granite and the kimberlites<br>are conductive as defined from downhole geophysical logging. The kimberlite shows<br>as a conductor in ground EM (SIROTEM and GEM-2 systems) surrounded by a<br>resistive host. It also shows a small conductive response in 56Khz DIGHEM data but<br>is not apparent in lower frequency data or in SALTMAP. The geometry of the latter<br>suggests that any response of the kimberlite is likely to be lost in a coupling of<br>transmitter with conductive wedges of granitic saprolite to the north and south of the<br>blow. Stitched sections of 1D LEI’s for SIROTEM, DIGHEM and SALTMAP show<br>similar trends and suggest that the regolith electrical structure is effectively modelled<br>as a layered earth, with some exceptions. An AEM “response map” in this area is<br>essentially a map of the variation of regolith/thickness and conductivity.