Fruta del Norte: Integrated Rock Mass Characterisation

SRK News | Issue 54: Rock Engineering and Slope Stability

   
    
A4   |   Letter

The Fruta del Norte project is an undeveloped, underground high-grade gold epithermal deposit in the southeast of Ecuador.

The deposit will be accessed via twin declines, and ore will be recovered using a combination of transverse open stoping with paste-fill, and drift and fill with cemented rock-fill, catering to the variable ground conditions and geometry of the orebody. SRK has been involved with the project in various capacities since 2009, and in 2015 assisted Lundin Gold with structural and alteration geology, rock mechanics, hydrogeology, and geochemistry aspects for their Feasibility Study. SRK was given the opportunity to review historic work, and guide the collection and quality control of parameters from drill core. One of the more critical aspects of the data collection from drill core logging was related to alteration geology: time dependent degradation of a dominant sedimentary package, and identification of damage zones related to structure and geomechanically adverse alteration.

During the 2015 field investigations, SRK completed an extensive alteration survey to characterise the nature and extent of the degradation. Basic but effective data collection practices, including graphic re-logging of historic core for the presence of hydrothermal alteration, degradation, and structure, and core photo reviews were complemented by TerraSpec visible/infrared spectrometer surveys.

Additional protocols were established to assist project geologists in recognising hydrothermal, breccia and vein-related alteration products. Leapfrog Geo 3D software was then used to model confidence envelopes illustrating the extents of the degradation zone, which formed one component of the final geotechnical model for the project.

Identifying the root cause of the degradation and its impact on geomechanical and geometallurgical properties had a significant bearing on rock mechanics, water quality, water management, and ultimately mine planning aspects of the project.

Bruce Murphy: bmurphy@srk.com

Planned underground mine design for the extraction of the Fruta del Norte deposit:

Underground mine design for high-grade gold deposit | SRK Consulting

 

SRK Africa