DEVELOPING A USEFUL SET OF PROXY ELEMENTS FOR TARGETING GOLD DEPOSITS IN THE BLACK HILLS, SOUTH DAKOTA

X-Ray Fluorescence (XRF), petrography, and Energy-Dispersive X-ray Spectrometry (EDAX) have been used to determine the element concentration in samples and the distribution within minerals for 222 metamorphic rocks from the Black Hills, S.D. The spatial distribution of proxy element concentrations in the whole rock are compared to sample location and known gold deposit in the Black Hills. XRF data of 222 rock chips from whole rock samples was collected using a portable XRF unit to determine major, minor and trace element abundances. Statistical analyses of the XRF data indicates a moderate to strong correlation between gold and the elements (proxy) Mn (19 to 16116 ppm), S (1283 to 79452 ppm), As (n.d. to 132ppm), Pb (n.d. to 318 ppm), Cl (625 to 31277ppm), Ba (n.d. to 1101 ppm) in. Samples containing visible gold have higher concentrations of the proxy elements. The integration of this data with Arc GIS is being used to test for the spatial relationship of the chosen proxy elements to known gold deposits in the Precambrian core of the Black Hills. Samples (22) were chosen for detailed petrographic analyses based on higher (greater than 18 ppm) gold concentrations previously determined through XRF analysis. EDAX raster scans are being completed on these samples in order to determine concentration variations of the chosen proxy elements within the individual mineral grains. Preliminary analyses indicates that sample proximity to known gold deposits in the Black Hills can be correlate with increases in minor and trace proxy element concentrations in the mineral phases. High concentrations of the proxy elements Mn (200 to 1500 ppm), S (3400 to 14800 ppm), As (15 to 132 ppm), Ba (180 to780 ppm), Pb ( 14 to 170 ppm), Cl (4800 to 29200) at rims and along fractures in the silicate and sulfide minerals are believed to be related to the associated gold bearing fluids which passed through the rocks.