Biogeochemical gold signatures in common juniper and Norway spruce at Suurikuusikko shear zone, Finnish Lapland

Exploration in glaciated terrains, such as the northern part of the Fennoscandian Shield, is commonly hampered by dispersed sediments. Biogeochemistry, i.e. chemical analysis of soil organic matter and plant species, is a potential tool for detecting buried mineralizations. We studied common juniper (Juniperus communis L.) and Norway spruce (Picea abies (L.) Karst) as biogeochemical gold exploration materials at gold prospective Suurikuusikko shear zone in western Finnish Lapland. The shear zone had been subjected to a high magnitude earthquake, due to postglacial rebound, 10,000 years ago. We found concentrations of gold in Norway spruce to be as low as 0.53 ± 0.79 μg kg− 1, whereas common juniper accumulated gold up to 54 μg kg− 1. We found that the Suasselkä postglacial fault generated, through fracturing of the mafic volcanic rock, a large number of springs with anomalous concentrations of arsenic (up to 50 μg l− 1). Our sampling design, two transects across the postglacial fault and following the course of the springs, suggests that the observed juniper gold-arsenic anomalies were generated by groundwater flow through fractured bedrock and then by uptake of root system. The postglacial fault had no effect on the geochemistry of glacially dispersed parent soil, and there was no correlation between the gold concentrations in soil and twigs. Our results suggest the chemical analysis of common juniper as a biogeochemical exploration method for gold.

► We evaluated gold signatures in common juniper and Norway spruce in Finland.
► Groundwater flow in post-glacial fault generated juniper gold-arsenic anomaly.
► Common juniper twigs accumulated gold up to 54 μg kg− 1.
► Gold concentration in Norway spruce twigs was low.
► The results promote a chemical analysis of gold and arsenic in common juniper.