Ann: Alpaca Hill Drilling Update and Frontier Reconnaissance, page-13

• The Voisey’s Bay nickel-copper-cobalt deposit in Labrador, Canada, was discovered in 1993 by Diamond Fields Resources. The company used an airborne magnetic survey to identify a large magnetic anomaly caused by a massive sulfide body. The anomaly was confirmed by ground gravity and electromagnetic surveys, followed by drilling¹.
• The Olympic Dam copper-uranium-gold deposit in South Australia was discovered in 1975 by Western Mining Corporation. The company used an airborne magnetic survey to detect a large magnetic anomaly associated with a hematite-rich breccia complex. The anomaly was further delineated by ground gravity and electrical surveys, followed by drilling².
• The Kibali gold deposit in the Democratic Republic of Congo was discovered in 2009 by Randgold Resources and AngloGold Ashanti. The companies used an airborne gravity gradiometry survey to map the regional structure and identify potential gold-bearing zones. The survey revealed a high-gravity anomaly coinciding with a magnetic low, indicating a large alteration zone. The anomaly was tested by drilling and confirmed to be a world-class gold deposit³.

Above the examples of Gravity and Magnetic surveys leading to discovery.
The Kibali shows that even High Gravity and Low magnetic also generated discovery therefore the failed attempt was justified.