Mapping of glacial erratic boulders for mineral exploration: A review with LiDAR-based examples from modern and ancient glaciated terrains

Abstract

Mineral exploration in glaciated terrains is dependent on a thorough understanding of the history and mode of flow of Pleistocene mid-latitude ice sheets to successfully identify potential mineralized targets in bedrock partially or completely covered by glacial sediments. Mapping of glaciated terrains and exploration using boulder trains and mineralized dispersal trains on the glaciated crystalline shields of Canada and Fennoscandia is challenged by vegetative covers and remote sensing data of inadequate resolution. Two methodological approaches for processing and visualizing drone mapped high-resolution LiDAR data, are described herein and used to identify and map erratic boulders at 1) a modern glacier foreland (Saskatchewan Glacier) in Alberta, where an extensive boulder-strewn and partially drumlinized till surface free of vegetative cover, is being exposed by ice retreat since 1854; and 2) at an area of known lithium and tin mineralisation obscured by thick forest cover in Nova Scotia, which has been affected by several Pleistocene glaciations, most recently by the Appalachian Glacier Complex some 20,000 years ago. The first methodological approach (Strip Alignment) is used to correct offsets formed between adjacent drone flight paths to enhance data coverage and resolution. The second (Semi-Automated Tree Point Classification) is used to eliminate vegetative covers from LiDAR point clouds. In combination with statistical analysis (Point Density), these methods permit successful mapping of erratic boulders and their spatial density. This approach can now be scaled up for regional mineral exploration projects and for geomorphic mapping of modern and ancient glaciated terrains to determine former ice flow trajectories and landform evolution.