Volcanic Massive Sulphide Mineral Deposits - VMS

Summary

This video explains volcanic massive sulfide (VMS) deposits, formed by underwater volcanic eruptions at rifts caused by extension faulting in the Earth's crust. Magma rises through faults, creating eruptions that deposit metals like copper, gold, zinc, and silver. These metals settle in volcanic piles near the eruptions, forming VMS deposits over thousands of years. Periods of volcanic activity alternate with sedimentation, forming layers of deposits. Uplifting and erosion expose these deposits, which are essential for mining operations, as seen in the Flin Flon VMS belt in Canada.

Takeaways

• 🌋 Volcanic massive sulfide (VMS) deposits form from underwater volcanic eruptions along rift or spreading centers caused by extension faulting.
• 🌊 Extension faulting is driven by magmatic vortices in Earth's liquid outer core, which stress the crust, leading to separation.
• 🌋 Magma from the Earth's interior exploits these faults, oozing out onto the seafloor and creating volcanic eruptions.
• 🏔️ These eruptions form volcanic piles made of ash and rock, which settle at the seafloor and can extend tens of kilometers from the volcanic center.
• 💦 Seawater is drawn through muds and rocks around the volcano, dissolving minerals and forming hydrothermal fluids rich in copper, gold, lead, zinc, and sulfur.
• 🔥 Hydrothermal fluids, heated by magma, rise through cracks in the volcanic pile, depositing metals like copper, gold, lead, zinc, and silver as they cool.
• ⚒️ The deposition of metals forms zonation: copper and gold settle near the vent, while lead, zinc, and silver are found higher up and farther away.
• ⏳ These processes occur over tens to hundreds of thousands of years, with layers of volcanic and sedimentary material building up over time.
• 🏞️ Continental uplift and collision bring these deposits closer to the surface, where they can be exposed by erosion and eventually recycled back into the ocean.
• 📍 A real-world example of VMS deposits is the Flin Flon VMS belt in Saskatchewan, which has been mined for nearly a century by the Hudson Bay Mining and Smelting Company.

Q & A

What are Volcanic Massive Sulfide (VMS) deposits?

VMS deposits are mineral deposits formed as a result of underwater volcanic eruptions. They occur primarily along rift zones or spreading centers where the seafloor is extended and faulted, allowing magma to ooze out and form deposits of metals such as copper, gold, lead, zinc, and silver.

What geological process leads to the formation of VMS deposits?

VMS deposits form due to underwater volcanic eruptions that occur along rift zones or spreading centers caused by extension faulting of the seafloor. Magma from Earth’s interior reaches the surface, and the resulting eruptions create volcanic piles that are rich in minerals.

How does extension faulting contribute to VMS formation?

Extension faulting, caused by magmatic vortices in Earth’s liquid outer core, exerts stress on the rocks making up the seafloor, causing them to separate. This allows magma to rise to the surface, where it plays a key role in the formation of VMS deposits through underwater volcanic eruptions.

What happens when magma erupts onto the seafloor?

When magma erupts onto the seafloor, it creates violent volcanic eruptions that form a volcanic pile of ash and rock. This pile can extend for kilometers and becomes the foundation for the deposition of metals through hydrothermal processes.

What role do hydrothermal fluids play in the formation of VMS deposits?

Hydrothermal fluids, formed when seawater is drawn through rocks and volcanic materials, dissolve minerals like copper, gold, lead, zinc, and sulfur. These fluids are heated by magma and deposit the dissolved metals as they cool, creating layers of mineral deposits in the volcanic pile.

How do metals like copper and gold get deposited within a VMS deposit?

As hydrothermal fluids rise and cool within the volcanic pile, metals like copper and gold are deposited first because they precipitate out at higher temperatures. These metals are often found deeper in the pile or closer to the volcanic vent.

What is the zonation of metals in a VMS deposit?

Zonation in VMS deposits refers to the arrangement of metals based on their temperature of deposition. Copper and gold are deposited closer to the vent and deeper in the pile, while metals like lead, zinc, and silver are deposited higher up and further away from the vent as the fluids continue to cool.

How do volcanic piles grow and change over time?

Volcanic piles grow through repeated eruptions. Coarser materials settle closer to the volcanic center, while finer materials drift further away. Over time, these piles are buried by sediments, and new volcanic piles may form on top during subsequent eruptions, creating a vertical and lateral accumulation of deposits.

What is the role of black smokers in VMS formation?

Black smokers are hydrothermal vents where some of the more energetic mineral-rich fluids escape from the volcanic pile and are expelled into the surrounding ocean. These vents contribute to the formation of metal deposits in the surrounding area.

What happens to VMS deposits over geological time periods?

Over time, VMS deposits may be uplifted due to continental collision, exposing them to erosion. The eroded material may then be transported back to the ocean and contribute to the cycle of sediment deposition and mineral formation.

What is an example of a region with prolific VMS deposits?

An example of a prolific area for VMS deposits is the Flin Flon VMS belt located in eastern Saskatchewan, Canada. This region has supplied metals for mining companies such as the Hudson Bay Mining and Smelting Company for nearly a century.