Friday, 16 September 2011

QEMSCAN® clay mineral identification

QEMSCAN®  compositional maps of selected Source and Special Clays and other reference material providing examples for the kaolin, smectite, illite and chlorite mineral groups.

Clay minerals are the product of chemical weathering, diagenesis and hydrothermal alteration of rocks. They are ubiquitous on earth and comprise a wide range of very fine-grained, layered, and often plastic aluminium silicates. The primary residual alteration products are easily eroded and moved by wind and water. As a result, extensive sedimentary accumulations of clays form in low-energy depositional environments such as lake beds and on the ocean floor. These deposits undergo diagenesis and the resulting materials are referred to as mudstone and shale.

Clays are among the most important minerals used in numerous applications by manufacturing and environmental industries. Some of their unique physical and chemical properties include the high surface-area-to-volume ratio, and high cation-exchange and swelling capacities. These properties are expressed in the characteristically high plasticity and adsorption qualities of some clay minerals.

Clay minerals have important applications and implications in the natural-resource industries, particularly in petroleum exploration and production, and in mining and mineral processing.

Clay minerals occur in all rock formations of siliciclastic petroleum systems, including source, reservoir and seal rocks. While playing a fundamental role in acting as impermeable barriers "trapping" the buoyant hydrocarbons in subsurface reservoirs, clay minerals can also pose significant challenges to exploration efforts and reservoir management.

The presence of clays in ore is a significant mining challenge. Ore bodies are typically marked by a close spatial relationship between fresh and weathered clay-rich zones, with different processing requirements. Small particle sizes and large surface areas result in high chemical reactivity that makes clays very responsive to changes in the mineral processing environment. As a result, mining, throughput, and recovery rates, can be significantly impacted by clays and require changes in the design of the process circuits.

At FEI Natural Resources, we have developed a clay mineral identification protocol using the new QEMSCAN® Spectral Analysis Engine at 20keV to discriminate important clay minerals in natural-resource applications. The protocol has been successfully applied to reference material from the Clay Minerals Society including the Source and Special Clays shown in the figure above. The work has been presented at EUROCLAY in an oral presentation earlier this year.

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