Forty one whole rock samples from the Gold
Cross low-sulfidation epithermal Au-Ag deposit have 18O values that
range from 4.4 to 9.3 per mil, with an average value of 7.0 per mil. Unaltered
and weakly altered rocks have 18O values greater than eight per mil,
and the orebody is surrounded by samples that are depleted in 18O. A
strongly silicified sample adjacent to the Empire Vein System has a
18O value of 9.0 per mil, similar to previously reported analyses of
vein quartz (7.0 to 11.7, average 9.4). This suggests that, in detail, Golden
Cross may have a zone of 18O-enriched wall rocks in the core of the
deposit, adjacent to the main underground veins. Although some workers have
suggested that stable isotope geochemistry may provide useful information for
epithermal mineral deposit exploration, at Golden Cross this is not the case.
Alteration minerals, major elements and trace elements all define larger, less
ambiguous halos than the zone of 18O-depleted wall
rocks.