Pushbacks pictorially explainedIt's important to understand exactly what a pit wall pushback is and how it is done .
I have found an excellent link which makes easy understanding (
https://www.linkedin.com/pulse/what-pushbacks-why-do-we-really-need-them-open-pit-mines-maepa ).
As can be read, pushbacks start at the top bench of the pit wall, removing the waste ore ( overburden ) after which the first bench of the new pit can be configured and mining of newly exposed ore can begin.
As I have posted earlier, the strip ratio ( amount of waste material to be removed relative to gold ore exposed ) is just 1 for pushback #1..
That is a very modest strip ratio which means the the higher grade ore can be mined early in pushback cycle #1.
Mining of newly exposed ore can then begin once enough of the top of the pit wall has been pushed back.
Bench width is about 40 meters and bench height is 12 meters.
Lets say say 200 linear meters of pit wall must be pushed back before mining begins.
So, we have 40x12x200 which is 96,000 cu m .
SG is 2.84 tons per cu m .
So, Approx 96, 000 X 2.84 = 375,000 tons of waste to remove.
The mining rate per quarter is about 500,000 tons of ore , with a strip ratio of 1. ( ie 500,000 tons of waste ore ).
From these calculations, it is clear that the top mining bench , 200 m along the top of the wall , can be ready for mining in about quarter.
Of course, there will be staging area logistics that will initially be completed before the pushback begins.
So let's make it two full quarters to be sure.
We know pushback #1 started in Q2.
Which indicates that at some point in early Q4 of 2022, mining of the newly exposed high grade ore could have begun.
Further, 50% of the low grade legacy ore amounting to 2400 tons in total would have been mined and produced in Q2 to early Q4 of 2022.
Which means there will be just two quarters of low grade ore remaining .
This will probably mixed in with the newly exposed high grade ore in 2023, for an average grade of about 0.9 gms per ton which is 50% higher than our 40,000 ounces produced in 2022.
Of course, they could begin mining the new ore exclusively, while using the rest of the legacy low grade ore to rebuild inventory which is also very important .
In summary, we are well placed to have a superb priduction year in 2023