Which statement best describes why Landsat remote sensing is useful for investigating gossan-bearing ore bodies?

• A. It can detect surface alteration minerals over large areas
• B. It provides high-resolution three-dimensional subsurface images
• C. It directly measures ore grade at depth
• D. It replaces the need for any ground surveys

Answer: (A)

Landsat helps with regional exploration because it can map surface alteration minerals over large areas, and those alterations often trace the footprint of gossan-bearing ore systems. When sulfide ore oxidizes at the surface, it forms iron oxides and hydroxides, and alteration minerals like clays and silicates. These materials have distinctive spectral signatures in Landsat’s visible to infrared bands, so band combinations and ratios can highlight altered zones across wide landscapes. Mapping these alteration halos lets geologists target ground surveys and drilling where buried ore bodies are more likely to occur.

This approach doesn’t provide high-resolution 3D subsurface images, nor does it measure ore grade at depth, and it doesn’t replace field surveys. It’s a powerful first step to identify broad areas of interest for more detailed investigation.