Gold Grade Distribution and Estimation in Narrow Vein Systems

摘要

Narrow vein systems represent an important source of gold, which have generally been exploited by small to medium sized companies. Their evaluation poses particular problems because of their grade nad geological complexities. The determination of grade is arguably the most important activity in resource estiamtion. as it is genrally grade and not tonnage that makes an orebody. This is particularly true of narrow vein-gold deposits whose resources are generally relatively small, though medium to high-grade (6-40+ g/t). They often display extreme grade anisotropy in all directions. Two grade populations are generally observed; 1) low, often subeconomic, background grades and 2) high-grades associated with discrete ore shoots. It is possible for gold to be distributed within the wallrocks as well as within the vein. Extremeely high-grade values typify this tyle of mineralisation and require special consideration during grade estiamtion to determine if top cutting is valid or not. Estimation of both width and accumaluation in 2D on vertical longitudinal projections or inclined planes have historically been used to cvaluate narrow veins.