STREAM SUSPENSATES FOR AU AND BASE-METAL EXPLORATION IN METAVOLCANIC FELSIC ROCKS, EASTERN PIEDMONT, GEORGIA, USA

Suspended sediment geochemistry in the drainage near the Magruder mine s, in the easternmost Piedmont, Georgia, targeted Au and base metal mi neralization. The mineralization is in a metadacite sequence and is co mprised of quartz-vein hosted Au plus the primary minerals chalcopyrit e, sphalerite, galena and pyrite. In addition to quartz, the gangue mi nerals include sericite and chlorite but gahnite and barite are common . The suspended sediments were analysed for 24 elements by instrumenta l neutron activation analysis and for Cu and Pb by atomic absorption s pectrometry. Of the elements analysed, Au, Cu, Zn and Ba are strong in dicators of the mineralization but Pb and the rare earth elements (REE ) also contribute to the multielement anomalies. The order of downstre am dispersion of the elements from the Magruder mineralization is Au < Pb = Ba < Cu = Eu, Yb, Lu < Zn. The strongest Au value in the suspend ed sediment ( 1 290 ppb) is located at the first sample site downstrea m ( 1 50-200 m) from the mineralized area. The maximum downstream disp ersion of strong concentrations of an indicator element (Zn, 2300 ppm) extends to about 800 m from the mine area. Suspended sediment should be included as a sampling medium in geochemical exploration for quartz -vein hosted fine-grained (micron) Au and polymetallic sulfide deposit s in felsic metavolcanic rocks in geomorphological and climatological regimes similar to that at the Magruder mines. Suspended sediments may be useful in delimiting areas with saprolite (eluvial) Au deposits an d stream reaches with potential for the accumulation of very fine-grai ned (micron) Au in placer deposits.