How does geological remote sensing make mineral exploration and mining more effective?

Mineral exploration and mining require precisely defined target areas to avoid unnecessary environmental damage and wasting money and resources. Here, geological remote sensing plays a vital role.

If this topic interests you, the Geoversity beginners' course in Geological Remote Sensing for Mining & Exploration is not to be missed.

So what does geological remote sensing do?

Geological remote sensing relies on the interaction of light with matter. In exploration and mining, sensors capture light reflected by rocks and minerals.

The reflectance percentage - the amount of light reflected after interaction with the surface - indicates certain material characteristics.

Remote sensing allows researchers to chart reflectance percentages across different electromagnetic spectrum wavelengths. This process enables mineral identification.

What's the most interesting part of the electromagnetic spectrum?

Within the electromagnetic spectrum, different wavelength ranges provide geological insights.

For iron-bearing minerals, the visible and near-infrared ranges are a good option.

The 2100 - 2400 nanometres wavelength range is much more interesting for effective identification of hydrothermal alteration mineralogy. In this range, certain minerals generate diagnostic responses, which ultimately allow for deposit mapping and characterisation.

What does hyperspectral imaging do that multispectral cannot?

Satellite sensors have been acquiring geological data for well over five decades. Early multispectral sensors captured broad wavelength bands, identifying basic surface features such as vegetation, water, rock surfaces, and urban areas.

Later, hyperspectral sensors revolutionised mineral analysis by capturing light in many narrow, contiguous channels. Where multispectral sensors could only identify groups of minerals, hyperspectral sensors opened up a highly detailed world where individual mineral species could be pinpointed.

Which satellites shaped the early years of geological remote sensing?

Throughout the years, several satellite programs have been breaking ground for geological remote sensing. Here's a short review of the two most influential ones.

• Landsat (1972-now)

The Landsat programme was initiated by NASA and USGS (United States Geological Survey). It was the first of its kind dedicated to collecting satellite imagery of Earth.

Early Landsat satellites (1–3) primarily identified iron oxides due to their limited spectral channels. Later versions, from Landsat 4 to Landsat 9 (2021), boosted the number of channels up to eleven, expanding Landsat's mineral detection potential.

Many countries still work with Landsat data because it's free and has many uses.

• ASTER (1999)

The launch of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) in 1999 was a giant leap forward. ASTER obtained high-resolution images in 14 different wavelengths. Its shortwave infrared channels greatly enhanced mineral exploration by detecting hydrothermal deposits containing valuable minerals such as copper, gold, and silver.

However, as ASTER no longer provides shortwave infrared information today; its usefulness for exploration and mining has been greatly reduced if temporal analyses are of importance

How did hyperspectral remote sensing contribute?

Since the introduction of hyperspectral sensors, Landsat and ASTER multispectral data have been supplemented with hyperspectral datasets collected by aircraft and drones—this significantly improved mineral mapping.

Unfortunately, airborne data is costly to obtain, and its coverage is very limited compared to the areas that satellite sensors can cover.

What the world needed was affordable hyperspectral satellite sensing. As of 2019, several options have been available, offering high-resolution data for free.

• PRISMA (2019)

Developed by the ASI (Agenzia Spaziale Italiana), PRISMA provides hyperspectral imaging across 237 channels. Its data is freely available and easy to access, but there are some limitations in specific wavelength ranges.

• EnMAP (2022)

EnMAP is a German hyperspectral satellite designed to monitor Earth's environment. It provides geochemical, biochemical, and biophysical data.

Access to its data no longer requires researchers to submit project proposals, and the current results are very promising. Lately, it has been the most used spaceborne hyperspectral sensor for geological remote sensing.

• EMIT (2022)

EMIT was developed by NASA. This hyperspectral instrument observes Earth from outside the International Space Station. As it primarily studies mineral dust sources, it focuses on non-vegetated areas, which means it has huge potential for geological remote sensing.

On the downside, processing EMIT data into usable formats has been challenging.

What's the biggest challenge in working with hyperspectral data?

While hyperspectral satellites improve the characterisation of target areas for exploration and mining, processing their vast datasets requires much more computing power than the average user has available on their laptop.

This also goes for the possible integration of hyperspectral data with AI and machine learning. A less computationally challenging solution may be found in cleverly combining hyperspectral and multispectral imagery.

Why should the Geoversity course be of interest to you?

The Geoversity beginners' course in Geological Remote Sensing for Mining & Exploration is primarily aimed at mineral exploration and mining professionals at MSc level. You will learn how to use remote sensing technology to obtain mineralogical information from rocks, rock faces, outcrops and land surfaces.

Through a series of presentations and hands-on exercises, you will be introduced to the basics of reflectance spectroscopy and the use of geological remote sensing data. In addition, we will discuss the latest sensors and processing software.

Upon completion of the course, you will understand how reflectance spectroscopy for rocks and minerals works, know how to use remote sensing data for identifying mineralogical information, and be able to evaluate the potential of geological remote sensing for mineral exploration and mining in your particular situation. Click here to enrol now!