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This paper quantifies the blast movement at three major porphyry-skarn and manto copper mines in South America.

It compared the pre-blast ore polygons positions to the post-blast polygons, using measured movement, to evaluate the effect of blast movement on ore loss, dilution and misclassification at each mine.

There is significant variation in each blast movement data, which is normal (at least ±50% of the mean). This variation occurs within all blasts, due to changes in blast design, firing, rock mass, voids and edge effects (every blast is unique).
The variability has implications to the ability to apply a template or model to predict movement. The accuracy of any movement template or model is defined by this variation and if it is used to move ore blocks, there will be a cost penalty compared with accurately monitoring every ore block, which can be quantified.

The magnitudes of horizontal movement in all blasts presented were significant. It is important to note that the effects of blast movement on ore recovery are not localized only to narrow-vein, structurally controlled deposits.

Values of ore loss can be 20%, or much more. Even low values of ore loss (5%), seen in Blast A at Mine A, can have a significant financial cost associated with it ($130,000 USD in a single blast).

Whether a mine’s priority is to minimize ore loss, dilution, contamination, or adhering to strict blending requirements, the aim is to efficiently separate different materials from the pit. For this reason, blast movement is a problem for every mine if it is not accounted for, even those situated in massive, gradational deposits.

Jeff Loeb, Principal Consultant
Marcell Silveira, Consultant
Blast Movement Technologies
Presented at Perumin 33, 2017