In geophysics, which geological target could be investigated using magnetic methods?

In geophysics, which geological target could be investigated using magnetic methods?

• A. A basalt flow
• B. A sandstone bed
• C. A skarn
• D. A granite dike

Answer: (C)

Magnetic methods pick up rocks that contain magnetic minerals, especially magnetite. These minerals create anomalies in the measured magnetic field that stand out from surrounding rocks, allowing us to map where those magnetized rocks occur underground. Skarns form where hot intrusive rocks alter surrounding carbonate rocks, often concentrating iron-bearing minerals like magnetite within the altered zones. That yields a clear, localized magnetic high that researchers can trace to delineate the extent and shape of the skarn, and to assess potential mineralization within it. In other contexts, rocks like basalt or granite can be magnetic too, but the strong, well-defined magnetic contrast associated with magnetite-rich skarns makes them particularly good targets for magnetic exploration.

Magnetic methods pick up rocks that contain magnetic minerals, especially magnetite. These minerals create anomalies in the measured magnetic field that stand out from surrounding rocks, allowing us to map where those magnetized rocks occur underground.

Skarns form where hot intrusive rocks alter surrounding carbonate rocks, often concentrating iron-bearing minerals like magnetite within the altered zones. That yields a clear, localized magnetic high that researchers can trace to delineate the extent and shape of the skarn, and to assess potential mineralization within it. In other contexts, rocks like basalt or granite can be magnetic too, but the strong, well-defined magnetic contrast associated with magnetite-rich skarns makes them particularly good targets for magnetic exploration.