Abstract
Dendrochemistry is the study of chemical constituents in tree rings. Dendrochemistry in mineral exploration can provide the fourth dimension of time not afforded by other sampling media, thereby potentially decoupling anthropogenic input from ore-derived and background signals. In this study, black spruce trees were cored on their south and west facings along a transect line intersecting volcanic hosted massive mineralization buried beneath 50 m of glacial till at Cross Lake near Timmins, Ontario in Canada. This area is NE and downwind from the Falconbridge Cu-Ni smelter which began operation in 1972. Tree rings were counted and 5-year segments representing pre- and syn-smelter conditions were analysed using a high-resolution inductively coupled plasma mass spectrometer. Results show that Cu, Zn, S, As and Mg are highly anomalous in both pre- and syn-smelter samples from trees over the mineralization, whereas other metals, such as Pb, Mn, and Ni, do not show the same response to mineralization, and are more influenced by bedrock lithologies and overlying sediments. Metal concentration trends are similar between the south and west facings of the trees, although the south samples are typically better for delineating the mineralization. A tree selected to represent non-mineralized background values shows increases in most of the metals in post-1960 tree rings, indicating that the Falconbridge smelter and mining activities have increased some metal contents of the surrounding soil. The results demonstrate that black spruce tree cores are useful for detecting metal anomalies from buried VMS mineralization under glacial till.
