Abstract
Gossans are surficial deposits that form in host bedrock by the alteration of sulphides by acidic and oxidizing fluids. These deposits are typically a few meters to kilometers in size and they constitute important vectors to buried ore deposits. Hundreds of gossans have been mapped by field geologists in sparsely vegetated areas of the Canadian Arctic. However, due to Canada’s vast northern landmass, it is highly probable that many existing occurrences have been missed. In contrast, a variety of remote sensing data has been acquired in recent years, allowing for a broader survey of gossans from orbit. These include band ratioing or methods based on principal component analysis. Spectrally, the 809 gossans used in this study show no significant difference from randomly placed points on the Landsat 8 imageries. To overcome this major issue, we propose a deep learning method based on convolutional neural networks and relying on geo big data (Landsat-8, Arctic digital elevation model lithological maps) that can be used for the detection of gossans. Its application in different regions in the Canadian Arctic shows great promise, with precisions reaching 77%. This first order approach could provide a useful precursor tool to identify gossans prior to more detailed surveys using hyperspectral imaging.
Highlights
Supergene weathering and oxidation of massive sulphide deposits often leads to the formation of iron caps between the surface and the water table (Figure 1)
Depending on the relative abundance of these minerals, gossans are characterized by red to yellow hues [2,3].Gossans are of interest to geologists because they constitute vectors to economic mineral deposits (e.g., [4,5])
The results demonstrate that geo big data [33] could be used to identify gossans in poorly-vegetated
Summary
Supergene weathering and oxidation of massive sulphide deposits often leads to the formation of iron caps between the surface and the water table (Figure 1). These gossans are dominated by the presence of silica, goethite, hematite and jarosite [1]. The oxidation of oxide-sulphide gossans in permafrost constitutes an analogue for natural acid mine drainage [6,7]. Gossans located in the permafrost regions are used to characterize comparable deposits on Mars and their potential to harbour life [15]
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