Borehole activation analysis by delayed and capture gamma rays using a 252Cf neutron source

Theoretical analysis and experimental comparison of the radiative capture and delayed gamma-ray activation techniques indicate the latter to be more efficient for the detection of copper, whereas the radiative capture method is preferable for nickel. A conservative lower detection limit for both copper and nickel is '-0.5%. Borehole spectra by both techniques were made in a copper- and nickel-bearing gabbro, utilizing a Ge(Li) propane-cooled detector. Al, Mn, Na, Mg, Cu, and V were readily activated and detected by the delayed method. H, Fe, Si, and Ni were not usually present in the delayed spectra but they responded well in the capture mode. It is shown that the borehole sonde can be configured to permit simultaneous delayed and capture spectra, permitting detection of all of these elements. Simulated borehole experiments indicate that, in the delayed gamma-ray mode, an infinite sample is achieved when the ore layer has a vertical thickness of ∼20 cm and a horizontal distance of '10 cm into the wallrock. The depth resolution is thus relatively good but horizontal penetration through the wallrock is limited. © 1972 Society of Economic Geologists, Inc.