Brucite Quantification with SWIR and Chemometric Modeling

Brucite quantification has become increasingly important in recent years due to its use in CO2 sequestration to combat climate change. CO2 can be turned into stable carbonate minerals through a natural process called carbon mineralization or mineral carbonation. This traps CO2 from the atmosphere in geologic time. By bringing CO2 in contact with specific minerals that are highly reactive to it, (brucite, serpentine) CO2 can be permanently locked away in a solid, stable form. Ultramafic rocks, which are primarily composed of minerals such as olivine, pyroxene, and serpentine, have shown significant potential for CO2 mineralization. These minerals contain a high concentration of magnesium, which can react with CO2 to form stable magnesium carbonates.

Brucite is a naturally occurring mineral that is widely distributed throughout the earth’s crust in ultramafic deposits. Brucite has a high surface area and is highly reactive, which makes it effective at absorbing and reacting with CO2. The reaction of brucite with CO2 produces various types of magnesium carbonate (such as MgCO2), which is a stable and long-term storage solution for CO2.

With the ultra-high spectral resolution of the oreXpert™, geologists can now accurately differentiate brucite from serpentine over the full spectral range of 350 to 2500nm. The 1400nm region (Figure 1) shows important distinguishing features to discriminate between brucite and serpentine. CO2 Lock (Vancouver, BC) has developed a new way to use mineral extraction technology to store CO2 for geological time. By combining spectral data from the oreXpert and PLSR (Partial Least Square Regression) methods, geologists can quantify the brucite and serpentine content within their deposits.

A quantification model was built for both brucite and serpentine using SOLO+Model Exporter from Eigenvector™. The steps to building a quantitative model using Spectral Evolution data are as follows:

· Known concentrations of calibration samples must be used to build the model (0-12% brucite, validated by TSG; 70-91% serpentine, validated by XRD)
· Obtain spectral data measurements of calibration samples with the oreXpert
· Pre-Processing methods: outlier removal, smoothing, first derivative etc.
· Plug in Spectral Evolution data (X input) and known concentration metadata (Y input) into SOLO by Eigenvector
· Optimize model
· Validate the model with known test samples to ensure accuracy

The brucite and serpentine models built using SOLO+Model Exporter were exported as a .xml file and loaded into the DARWin™ acquisition software for real time quantification. The brucite results are seen in Figure 2; serpentine results seen in Figure 3.

Figure 2

Figure 3

By combining spectral data from the oreXpert with chemometric modeling, geologists can identify and quantify important minerals such as brucite and serpentine for carbon mineralization. This method cuts down on time and cost of sending samples to a lab. You can now have the results in just a few seconds using a contact or benchtop probe accessory with the oreXpert. This technology could prove to be critical in the development of carbon sequestration methods.

With Spectral Evolution field portable UV-Vis-NIR spectrometers and EZ-ID mineral identification software, geologists can measure and identify minerals within seconds and cover more ground than by using traditional methods. They can identify different mineral phases, create mineral alteration maps and more accurately identify mineral pathfinders for vectoring to ore deposits. Spectral Evolution’s field portable, battery-operated oreXpress™, oreXplorer™ and oreXpert™ ultra-high resolution UV-Vis-NIR spectrometers provide quick payback with faster, more accurate mineral identification in exploration for gold, silver, diamonds, iron, nickel, copper, uranium, aluminum – in the field, core shack, or in the lab.