Operated by Agnico Eagle Ltd., the Goldex mine uses a sub-level caving method employing three large stopes and long blast holes to extract gold particles contained within quartz-tourmaline veins.  The site is located near Val-d’Or in the Abitibi region of Northwestern Quebec, Canada and has been in commercial production since mid-2008.

Background

Cave mining is typically performed at sites where a large ore deposit is located so far beneath the ground surface, that open-pit extraction is not economically or environmentally feasible.  Sub-level caving is an underground mining method used for sites with steeply dipping deposits.  The method approaches the deposit from various intermediate levels underground, and like other caving methods, harnesses gravity to aid in ore removal. 

At each intermediate level, longhole drilling is performed upwards and selective blasting is used to collapse the rock.  Mining then retreats toward the footwall as ore and waste rock are removed.  This method of extraction can be performed on multiple levels simultaneously, beginning with the lowest level and will continuing on each level until the desired ore is depleted.

ESG Solution

An ESG Paladin microseismic system was implemented at the Goldex mine in early 2009.  The microseismic array consists of a mixture of uniaxial and triaxial sensors monitoring a volume of 450m x 400m x 400m. The purpose of this system is to ensure mine safety and to track caving front propagation.

The microseismic array enables accurate location of cave induced seismicity and offers high sensitivity to small magnitude events. 

Advanced analysis of the microseismic data using a collapsing method performed on the event locations provided enhanced high-resolution images of the caving front and verified the existence of geological structures within the orebody.

Analysis of the seismic deformation associated with the collapsed caving front reveals the amount of damage caused by blasting in the seismogenic zone.  Seismic deformation uses temporal and spatial statistics along with event moment magnitude values to estimate the deformation caused by seismicity. 

Fig. 2: Seismic deformation of uncollapsed microseismic events

Fig. 3: Seismic deformation of collapsed microseismic events