Exploration for zinc and lead in western Newfoundland based on geochemical surveys

Abstract

Exploration for zinc and lead in the Paleozoic carbonates of western Newfoundland has relied heavily on geochemical techniques. In the Goose Arm—Raft Pond area north of Corner Brook, stream silt and lake sediment geochemistry defined coincident anomalous areas which were then covered by reconnaissance soil sampling grids. This reconnaissance survey confirmed and detailed some anomalies around Raft Pond while allowing other areas to be rejected. A study of the surficial deposits in the Raft Pond area revealed that the anomalous soils were derived from either slopewash or from local glacial fans, information useful in later prospecting. In 1974, exploration was concentrated on the Raft Pond area and on the Goose Arm Peninsula where Zn-Pb showings had been located earlier. Detailed soil grids were sampled in the two areas and cumulative frequency curves were plotted on probability paper for the Fe, Zn, and Pb analyses to identify background and anomalous populations. When geological mapping was completed, soils overlying limestone were separated from those overlying dolostone and the calculations were repeated. In most cases, this allowed a clearer interpretation of the data and a more accurate definition of anomalies. In addition, the analysis indicated that lead mineralization probably did not occur in particular lithologies in the area. Low-grade zinc occurrences in dolostone of the St. George Group were found associated with many geochemically anomalous areas. There did not appear to be a relationship between the intensity of the anomaly and the grade of mineralization in bedrock. Also the amount of accuracy provided by the detailed soil survey was superfluous once the type of sphalerite occurrence was recognized. In this terrain, a soil grid with sample centres 500 ft (150 m) apart might be the optimum aid to exploration.