Investors slashed a quarter off the value of junior gold explorer Helix Resources NL yesterday after the release of drilling results that suggested the company's Tunkillia gold discovery in South Australia may be only half the size estimated by analysts.

Helix shares nosedived $1.26-a-share to $3.73 yesterday, wiping $65 million off its market capitalisation. A host of other explorers with nearby permits, including Equinox Resources, Pima Mining and Grenfell Resources , all fell sharply.