Research in geochemical prospecting methods for native silver deposits, Cobalt area, Ontario, 1966
Authors: Boyle R W , Dass A S , Church D , Mihailov G , Durham C , Lynch J , Dyck W 
Published: March 2016

Research in geochemical prospecting methods, including analyses of wall-rocks in the vicinity of the native silver veins , analyses of soils, tills, and glacial ciay on traverses across the veins, analyses of stream, spring, and underground waters and their
precipitates, and gamma-ray scintillometer surveys on traverses across the veins both underground and on the surface was carried out in the Cobalt area of Ontario during June, July, and August, 1966. Most of the analytical work was done in the field utilizing field colorimetric and spectrographic
laboratories. Some 2, 461 samples of rocks, soils, tills, glacial clays , and precipitates from springs and underground waters were analy:z:ed for Cu, Pb, Zn, Ag , Ni, Co, Mo, Hg, As, Sb, Bi, W, and Mn, and some 360 samples of stream, spring, well, and drill-hole waters were analyzed for total heavy
metals (mainly %:inc), nickel, and cobalt in the field. The Eh, pH, and temperature of the spring, ground, and stream waters were also determined at each sample point. In the laboratories in Ottawa some 80 samples of water were analyzed for Pb, Zn , Cd, Cu, As, Sb, Ag, Ni, Co, Mn, and Fe by
atomic absorption, In addition some 40 samples of water were analyzed in Ottawa for their major constituents. The following conclusions on the various surveys seem war - ranted. 1. Trace element analyses of clay and derived soils are not effec - tive for prospecting for silver veins in the Cobalt
area.· 2. Trace element analyses of till and derived soils should be effective for prospecting for silver veins in the Cobalt area. The A horizon gives the best r esponse, but in some places the B horizon also responds favourably, especially where the till is relatively shallow. The C horizon
is generally not suitable except where samples are taken close to bedrock. The best indicator elements in the till and derived soils are Ag, As, Sb, and Mn. Nickel and cobalt are also effective in some areas, and mercury may be useful in a few places . 3. Trace element analyses of both drill core
samples and rock chips indicate the presence of veins and vein clusters. In the Cobalt sediments the dispersion of Ag, As, Sb, Ni, Co, Mn, and Hg outward from the veins is broad, and veins may be indicated as far as 100 feet away by these elements. A somewhat similar pattern is present for silver
veins in the Keewatin greenstones , but the dispersion is generally more restricted, In the Nipissing diabase the dispersion is narrow and veins are indicated only a few feet away by a rise in Ag, As, Ni, and Co. 4, Gamma-ray scintillometer surveys proved negative for locating veins, suggesting that
this method is not applicable for soils, till, glacial clay, or rocks in the Cobalt area. 5. The water analyses are difficult to interpret in terms of geochemical prospecting for silver veins. The groundwaters have pH1s ranging from 3. 0 to 9. 6 and contain variable amounts of dissolved HC03 and
S04. In general the spring and drill-hole waters in the vicinity of silver veins are enriched in Zn, Cu, Ag, Co, Ni, As, and Sb. The content of these elements increases with increase in the acidity of the water. Cobalt is much more mobile in the waters than nickel. The general conclusion that water
analyses may be useful in locating areas in which silver deposits occur seems valid, but they cannot be expected to pinpoint individual deposits. 6. The natural iron and manganese precipitates at the orifices of springs and drill-holes are greatly enriched in Cu, Pb, Zn, Ag, Co, Ni, As , and Sb in
the vicinity of known silver deposits. Similar precipitates well removed from known silver deposits have normal contents of these elements. 7. Great care must be taken in the Cobalt area in using geochemical prospecting methods because of the large amount of contamination present from old mine
dumps, trenches, and domestic refuse. From an academic viewpoint consideration should be given to the possibility that the sedimentary interflow bands and certain volcanic flows in the Keewatin assemblage are the source of the Ag , Cu, Pb, Zn, Ni , Co, Bi , As, and Sb in the silver deposits. These
sedimentary and volcanic rocks are greatly enriched in the ore elements compared with the Nipissing diabase, Cobalt sediments, and granites.