Model Answer
0 min readIntroduction
Ore deposits, crucial for economic development, are rarely found as uniform bodies. Their geometry is described using terms like ‘pitch’ and ‘plunge’, which are essential for resource estimation and mine planning. Understanding these parameters allows geologists to accurately model the ore body and optimize extraction strategies. The grade of an ore body, representing the concentration of the valuable mineral, is another critical parameter. This answer will define pitch and plunge, and then calculate the average grade of a lead (Pb) ore body using provided data, demonstrating a practical application of these concepts in economic geology.
Understanding Pitch and Plunge
Pitch refers to the angle between the horizontal plane and the line representing the steepest descent on an inclined plane or surface. In the context of an ore body, it describes the angle of dip of the ore body’s surface from the horizontal. It is measured perpendicular to the strike.
Plunge, also known as dip angle, is the angle between the horizontal plane and the direction of the maximum slope of a planar feature, such as a vein or the overall shape of an ore body. It indicates the direction of the ore body’s inclination. It is measured downwards into the earth.
These two parameters, when combined with the strike (the direction of the line formed by the intersection of an inclined plane with a horizontal plane), completely define the orientation of an ore body in three-dimensional space. Accurate determination of pitch and plunge is vital for geological modeling, resource estimation, and mine design.
Calculating Average Grade of a Pb-Ore Body
To calculate the average grade of the Pb-ore body, we need the data representing the concentration of lead in different samples. Let's assume the following data is provided (this data is hypothetical as none was given in the question):
| Sample ID | Weight (kg) | Pb Concentration (%) |
|---|---|---|
| S1 | 100 | 2.5 |
| S2 | 150 | 3.0 |
| S3 | 80 | 2.0 |
| S4 | 120 | 3.5 |
The average grade is calculated using the following formula:
Average Grade = (∑ (Weighti * Concentrationi)) / ∑ Weighti
Applying this formula to the data:
Average Grade = ((100 * 2.5) + (150 * 3.0) + (80 * 2.0) + (120 * 3.5)) / (100 + 150 + 80 + 120)
Average Grade = (250 + 450 + 160 + 420) / 450
Average Grade = 1280 / 450
Average Grade = 2.84%
Therefore, the average grade of the Pb-ore body, based on the provided (hypothetical) data, is 2.84%.
Importance of Grade Calculation
The grade of an ore body is a crucial economic factor. It directly influences the profitability of mining operations. A higher grade generally means a higher concentration of the valuable mineral, leading to lower extraction costs and increased revenue. Grade calculations are also essential for resource classification according to standards like JORC (Joint Ore Reserves Committee) or NI 43-101.
Conclusion
In conclusion, pitch and plunge are fundamental parameters for describing the orientation of ore bodies, while grade represents the economic viability of extracting those resources. Accurate determination of these parameters is crucial for geological modeling, resource estimation, and ultimately, successful mining operations. The calculated average grade of 2.84% (based on the hypothetical data) provides a preliminary assessment of the Pb-ore body’s economic potential, though further detailed analysis would be required for a comprehensive evaluation.
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.