b'What lies beneath revisitedFeatureFigure 7.H-4 (Tanjeel) deposit: TEM channel 15 + drilling-top image; geological section with supergene zone-bottom image (Schloderer 2003).Figure 8.TEM line over Las Cruzes (Spain) deposit-supergene zone (McIntosh etal. 1999). The \x1fgure show Zonge Engineering 1D STEMINV inversion results.of a porphyry-copper system tend to encourage descent of the water table, causing leaching of previously formed enrichment zones and reprecipitation of supergene copper sulphides at progressively lower levels and augmenting copper grades and enrichment blanket thickness.It is considered likely that the Casino and Silver Bell examples formed as the consequence of one-event; a supergene zone is formed, but the enrichment process does not reach the copper grade, and hence the conductivity, that might be expected from multiple events. Multiple events seem to be associated with deposits that formed in very dry climates.SummaryWhile there was a surge of examples in the 1990s showing exploration applications of EM to chalcocite mapping, the last 20 years have not generated many new examples, suggesting many explorers may never have heard of the relationship and may miss making the connection, even if they are presented with data that shows the supergene e\x1eect is in play.Having \x1deld data on which to base judgments is always a good starting point, but for all the work in the 1990s thereFigure 9.Weight percent sulphides vs. resistivity (Nelson and Voorhis 1983).DECEMBER 2023 PREVIEW 48'