Rigorous geological input in gold mineralisation models

Despite the intention to include geological controls during the wireframing phase of the mineral resource estimation process, modelling methodology is sometimes reduced to connecting grade data along trends judged to be geologically valid. This is specifically the case for precious metal vein deposits where the grade distribution is controlled by complex vein systems. This case study exemplifies how such models can be enhanced by incorporating structural geology analysis into the modelling process.

Eastmain Resources Inc. commissioned SRK to construct a mineral resource model for its Eau Claire gold deposit located in James Bay (Quebec). Gold mineralisation at Eau Claire occurs primarily in metre-scale quartz-tourmaline veins associated with massive actinolite-tourmaline-biotite alteration of their host rock. A wireframe model for the gold mineralisation was previously constructed by a third party but was discarded as it failed to honour factual geological observations.

SRK conducted rigorous structural analysis using surface mapping, drill core analysis, and 3D litho-structural modelling to define and understand the geometry of the auriferous vein system. Three sets of mineralised structures were identified including east-trending and west-northwest-trending sets, as well as a series of older northwest-trending massive replacement zones. Individual veins were modelled independent of grade by diligently reconciling logged vein intervals with vein intervals mapped at surface.

The final modelling stage involved constructing gold mineralisation wireframes that incorporate assay data located within both the veins and their altered selvages. This methodology ensured that the resulting wireframes honoured the vein system geometry, adding considerable confidence to the mineral resource modelling process. This increased confidence will prove invaluable as the project advances to conceptual mining studies.

Jean-Francois Ravenelle: jfravenelle@srk.com

Rigorous geological input in gold mineralisation models

Comparison between third party gold mineralisation model (top) and SRK model (bottom)

 


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