Femtosecond laser processing for blast-hole analysis: laser removal of slurry and effect on rocks

TL;DR

This paper explores using femtosecond laser pulses to remove slurry from blast holes, enabling better analysis of underlying rocks while minimizing damage and preserving chemical properties.

Contribution

It demonstrates the feasibility of femtosecond laser ablation for cleaning blast-hole surfaces and characterizes its effects on various Australian mineral rocks.

Findings

Ablation depth and efficiency of slurry removal were quantified.

Ablation thresholds and rates for different rocks were established.

Laser-induced damage was minimal and well-characterized.

Abstract

This study investigates the possibility of using a femtosecond pulse laser to remove iron ore slurry used to stabilise blast-hole structures by mining industries, intending to preserve the wall's stability and the chemical and compositional properties of the underlying rock. In situ minerals are often coated in other material deposits, such as dust or slurry in blast holes. To analyse the rock materials beneath, its surface must be exposed by removal of the surface layer. The ablation depth per pulse and ablation efficiency of the slurry were determined using femtosecond laser pulses. Then, the ablation of rocks of economic interest in Australia, including banded iron, limonite, goethite, shale, and hematite, was studied to establish their ablation thresholds and rates. Any damage induced by the laser was investigated by optical microscopy, optical profilometry, colourimetry, VIS/NIR spectroscopy and Fourier Transform Infrared spectroscopy (FTIR).