Porphyry Copper or VMS: Which Do Companies Prefer?

When it comes to sourcing copper and other base metals, Porphyry copper and Volcanogenic Massive Sulfide (VMS) deposits stand out as two of the most significant geological formations. Both types have similarities in their geological settings and mineral content, yet they differ greatly in formation processes, size, and economic potential. But what other types of copper deposits exist, and why might companies favor one over another?

Copper Deposits Based on Geological Setting

• Porphyry Copper Deposits:
  • The largest and most economically significant type.
  • Formed from large-scale magmatic intrusions.
  • Characterized by low-grade but high-tonnage mineralization.
• Massive Sulfide Deposits (VMS):
  • Occur in submarine volcanic environments.
  • Contain high concentrations of copper, zinc, and lead.
• Sedimentary Copper Deposits:
  • Formed by the accumulation of copper-rich sediments.
  • Examples include sandstone-hosted copper deposits and shale-hosted copper deposits.
• Skarn Deposits:
  • Formed by the interaction of hot fluids with carbonate rocks.
  • Often associated with porphyry copper deposits.
• Epithermal Copper Deposits:
  • Formed near the Earth's surface from hot water solutions.
  • Primarily associated with gold and silver, but can contain copper.
• Orogenic Copper Deposits:
  • Associated with large-scale tectonic processes.
  • Often found in deformed and metamorphosed rocks.

While these are general categories, there can be significant variations within each type. The specific geology, mineralogy, and economic viability of a copper deposit will depend on multiple other factors.

Preferred Copper Deposit Types Based on Geological Setting

The "preferred" type of copper deposit often depends on factors like:

• Economic viability: This includes factors like ore grade, tonnage, and extraction costs.
• Environmental impact: Considerations like the deposit's location, potential for pollution, and reclamation plans.
• Technological advancements: New technologies can make previously uneconomic deposits viable.

That said, based on historical production and economic success, here are some general trends:

Favorable Geological Settings

• Volcanic Arc Environments:
  • Porphyry copper deposits: These are often associated with large-scale magmatic intrusions found in volcanic arc settings. They tend to be large, with relatively low-grade but high-tonnage mineralization.
  • Volcanogenic Massive Sulfide (VMS) deposits: These form in submarine volcanic environments and can be high-grade but typically smaller in size.
• Sedimentary Basins:
  • Sedimentary copper deposits: These can be significant, especially in large, stable sedimentary basins. Examples include sandstone-hosted copper deposits and shale-hosted copper deposits.

Less Common but Potentially Profitable

• Orogenic Belts:
  • Orogenic copper deposits: These are often associated with large-scale tectonic processes and can be high-grade but complex in terms of geology and mining.

Important Considerations

• Exploration Risk: Porphyry copper deposits may be more statistically likely to be found, but exploration carries high risk. Other types might have lower exploration costs but higher geological uncertainty.
• Market Demand: Fluctuating demand for copper can affect the desirability of different deposit types.
• Environmental Regulations: Environmental impacts vary greatly between deposit types and locations

Although porphyry copper deposits have been historically dominant, the "preferred" type can shift based on evolving economic, technological, and environmental factors. So why are some companies increasingly considering VMS over Porphyry?

Why VMS Deposits?

• High-grade mineralization: VMS deposits are typically rich in copper, zinc, lead, and precious metals.
• Multiple metal production: Extracting multiple metals from a single deposit enhances economic viability.
• Strategic metals: VMS deposits often contain critical minerals like cobalt, nickel, and gold.

While porphyry copper deposits have long been a staple of the mining industry, the growing interest in Volcanogenic Massive Sulfide (VMS) deposits is prompting a closer look at their unique advantages.

In our next post, we’ll delve into how to effectively search for VMS deposits by exploring the Quebec SIGEOM database. Discover the techniques and tools used to uncover these hidden resources and why they could be the key to future mining success. Stay tuned!