Optimizing Drilling Spacing for Mineral Exploration: Best Practices and JORC Compliance

Optimizing Drilling Spacing for Mineral Exploration: Best Practices and JORC Compliance

Core drilling for dipping mineral deposits

Introduction 

In the field of mineral exploration, one of the critical steps towards accurately defining a mineral deposit and resource is the implementation of an efficient drilling program. The success of this program hinges on meticulous planning and adherence to industry standards such as the JORC Code (Joint Ore Reserves Committee Code). The JORC Code itself does not prescribe specific drilling spacings for different types of minerals. Instead, it provides principles and guidelines for reporting exploration results, mineral resources, and ore reserves, emphasizing transparency, materiality, and competence. However, industry practices have established typical drilling spacings for different types of minerals based on experience and geological considerations. This article highlights into best practices for drilling spacing across various minerals.

Important Considerations

  1. Geological Complexity: More complex geology of a mineral deposit may require closer drill spacing to achieve the same level of confidence.
  2. Deposit Type: The nature of the deposit (e.g., vein, disseminated, massive, bedded, lens) affects the required spacing.
  3. Confidence Levels: Closer spacings are needed for higher confidence levels (Measured vs. Indicated vs. Inferred).
  4. Economic Factors: The value and economic significance of the mineral can influence the extent of drilling required.
  5. Drill Hole Orientation: Angle of drilling should be chosen based on the dip and strike of the mineralization. Vertical holes are common in flat-lying deposits, while angled holes are used in steeply dipping deposits.

While these spacings are generally accepted practices, it's essential to tailor them to the specific project needs, based on geological settings of mineral deposits, and ensure compliance with the principles of the JORC Code, which emphasizes adequate sampling, appropriate methods, and thorough documentation.

Understanding Drilling Spacing in Mineral Exploration

Drilling spacing refers to the distance between individual drill holes in a grid pattern. The optimal spacing is influenced by the geological complexity of the deposit, the type of mineral, and the desired confidence level in the resource estimate. Here's a breakdown of typical drilling spacings for different minerals:

Gold Exploration Drilling Spacing

  • Exploration Phase: Initial drill holes are often spaced at 100m x 100m or wider to cover a broad area and identify potential mineralization.
  • Resource Definition:

Inferred Resources: 50m x 50m to 100m x 100m.

Indicated Resources: 25m x 25m to 50m x 50m.

Measured Resources: 10m x 10m to 25m x 25m.

Copper, Zinc, Lead, Cobalt Drilling Spacing

  • Exploration Phase: Wide spacing such as 100m x 100m to broadly explore the area.
  • Resource Definition:

Inferred Resources: 50m x 50m to 100m x 100m.

Indicated Resources: 25m x 25m to 50m x 50m.

Measured Resources: 10m x 10m to 25m x 25m.

Iron Ore Drilling Spacing

  • Exploration Phase: Typically starts with 200m x 200m spacing.
  • Resource Definition:

Inferred Resources: 100m x 100m to 200m x 200m.

Indicated Resources: 50m x 50m to 100m x 100m.

Measured Resources: 25m x 25m to 50m x 50m.

Coal Exploration Drilling Spacing

  • Exploration Phase: Often utilizes a wide spacing of 500m x 500m or more.
  • Resource Definition:

Inferred Resources: 200m x 200m to 500m x 500m.

Indicated Resources: 100m x 100m to 200m x 200m.

Measured Resources: 50m x 50m to 100m x 100m.

Drilling Spacing for Platinum Group Metals (PGMs)

  • Exploration Phase: Initial wide spacing of 100m x 100m.
  • Resource Definition:

Inferred Resources: 50m x 50m to 100m x 100m.

Indicated Resources: 25m x 25m to 50m x 50m.

Measured Resources: 10m x 10m to 25m x 25m.

Uranium Drilling Spacing

  • Exploration Phase: Wide spacing of 200m x 200m or more.
  • Resource Definition:

Inferred Resources: 100m x 100m to 200m x 200m.

Indicated Resources: 50m x 50m to 100m x 100m.

Measured Resources: 25m x 25m to 50m x 50m.

Nickel Drilling Spacing

  • Exploration Phase: Wide spacing such as 200m x 200m.
  • Resource Definition:

Inferred Resources: 100m x 100m to 200m x 200m.

Indicated Resources: 50m x 50m to 100m x 100m.

Measured Resources: 25m x 25m to 50m x 50m.

Potash and Phosphate Drilling Spacing

  • Exploration Phase: Very wide spacing, often 1,000m x 1,000m.
  • Resource Definition:

Inferred Resources: 500m x 500m to 1,000m x 1,000m.

Indicated Resources: 200m x 200m to 500m x 500m.

Measured Resources: 100m x 100m to 200m x 200m.

Limestone Drilling Spacing

Inferred to Measured Resources: 300m to 50m depending on geochemical characteristics.

Adhering to JORC Code Principles

The JORC Code emphasizes transparency, materiality, and competence in reporting exploration results, mineral resources, and ore reserves. While it doesn't prescribe specific drilling spacings, it requires that the chosen spacings are justified and documented based on geological and economic considerations.

Key JORC Code Guidelines for Drilling Programs

  1. Objectives: Clearly define the drilling program's objectives, whether for resource definition, grade control, or geological information.
  2. Techniques: Specify the drilling techniques and justify their selection.
  3. Sampling and Assaying: Implement rigorous sampling and assaying methods, including QA/QC procedures.
  4. Data Management: Ensure accurate data collection, storage, and validation.
  5. Health, Safety, and Environment: Prioritize the health and safety of personnel and minimize environmental impact.

Conclusions

Optimizing drilling spacing is a fundamental aspect of successful mineral exploration. By adhering to industry best practices and the JORC Code's principles, exploration companies can ensure reliable data collection and robust resource estimates. Whether exploring for gold, base metals, iron ore, or other minerals, understanding and implementing the appropriate drilling spacing is crucial for advancing from exploration to resource definition and ultimately to mining.

For more detailed guidelines and specific recommendations, consulting with experienced geologists and adhering to the latest industry standards is essential. By doing so, companies can achieve accurate resource estimates and ensure compliance with regulatory requirements, paving the way for successful mineral development projects.

Reference

The Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (The JORC Code), 2012 Edition, prepared by the Joint Ore Reserves Committee (JORC) of The Australasian Institute of Mining and Metallurgy, Australian Institute of Geoscientists, and Minerals Council of Australia.

 

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