Model Answer
0 min readIntroduction
Ore reserve estimation is a critical aspect of mining geology, providing the quantitative basis for economic feasibility studies and mine planning. Vein-type ore deposits, characterized by their tabular or irregular shapes, require careful assessment of their geometry and grade distribution. Accurate tonnage and grade calculations are essential for determining the economic viability of extracting the ore. This question tests the ability to apply fundamental principles of ore reserve estimation to a given geological scenario, utilizing trench data and specific gravity to determine the ore body’s potential.
Understanding the Problem
We are given a vein-type copper ore body with a known strike length, dip, and depth. Four trenches are established across the ore body at regular intervals, providing thickness and assay value data. The goal is to calculate the total tonnage, grade, and copper content of the ore body.
Assumptions and Data Organization
We assume the ore body maintains a consistent geometry between the trenches. Let's organize the given data (which is missing in the question, so we will assume some values for demonstration purposes. A real answer would use the provided table). For the sake of calculation, let's assume the following data:
| Trench Location | Thickness (m) | Assay Value (% Cu) |
|---|---|---|
| West End (0m) | 2.0 | 3.5 |
| 37.5m | 2.5 | 4.0 |
| 75m | 3.0 | 3.8 |
| East End (150m) | 2.2 | 3.2 |
Calculating Volume
The ore body can be approximated as a prism with a length of 150m, a width equal to the average thickness, and a height of 50m. First, calculate the average thickness:
Average Thickness = (2.0 + 2.5 + 3.0 + 2.2) / 4 = 2.425 m
Volume = Length x Width x Height = 150 m x 2.425 m x 50 m = 18187.5 m3
Calculating Tonnage
Tonnage is calculated by multiplying the volume by the specific gravity and the density of water (1000 kg/m3).
Tonnage = Volume x Specific Gravity x Density of Water = 18187.5 m3 x 2.8 x 1000 kg/m3 = 50925000 kg = 50925 tonnes
Calculating Total Copper Content
To calculate the total copper content, we need to determine the average grade of the ore body. We can calculate this by averaging the assay values from each trench:
Average Grade = (3.5 + 4.0 + 3.8 + 3.2) / 4 = 3.625 %
Total Copper Content = Tonnage x Average Grade = 50925 tonnes x 0.03625 = 1848.56 tonnes of Copper
Grade Calculation
The grade of the ore body is the average assay value, which we have already calculated as 3.625% Cu.
Considerations and Limitations
This calculation is based on several assumptions. The actual ore body may not have a uniform thickness or grade. Geological structures like faults or folds could significantly affect the ore body's geometry and grade distribution. More detailed sampling and geological modeling would be required for a more accurate estimate.
Conclusion
Based on the assumed data and the applied methodology, the estimated tonnage of the copper ore body is 50925 tonnes, with an average grade of 3.625% Cu, containing a total of 1848.56 tonnes of copper. This estimation provides a preliminary assessment of the ore body’s potential. Further exploration and detailed geological modeling are crucial for refining these estimates and making informed decisions regarding mine development.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.