bows333,

My understanding is that geophysics is used in mineral explorartion to identify anomalies that can be used to help target drillholes.

ZTEM seems to be the "latest & greatest" geophysical technique that many companies are using and GeoTech seems to be an industry leader in using this technology.. Not sure how successful this has been for Excellon at Platossa.

Came across this info on ZTEM (from another mineral exploration company that used GeoTech) that you might find useful:

http://finance.yahoo.com/news/Canasil-Completes-ZTEM-iw-2079151809.html

"The ZTEM (Z-Axis Tipper Electromagnetic System) helicopter borne survey is designed to provide unparalleled depth of investigation in precision electromagnetic measurements, and provides data on geologic structures at depth over large areas to assist in identifying the potential for large mineralized systems. "