using one metal grade low CoG results in invalid value of other metal when reporting MRE

ChaoxianZhou1

In the mineralization domain, there are Au, and Cu.

Here I use eq(Cu+Au) to act as cut-off grade (CoG) to do Mineral Resource Estimation.

eqCuAu means Cu +equvalent to Cu from Au

when using CoG=0%, there are invalid in Cu grade and contained Cu;

when using CoG=0.2%, there are still some invalid in Cu grade and contained Cu;

when using CoG=0.3%, the invalid value disappears.

However,

when I use Cu as CoG, all data (including eqCuAu, Cu and Au) are valid.

what wrong?

How should I get rid of the invalid value if I have to use eqCuAu CoG =0.2%?

Thank you！

Ian