L3 - Ti-V Oxide Magmatic Ore Deposits

What criteria must a mineral meet to be considered a critical mineral in Canada?

1. The supply chain is threatened

2. There is a reasonable chance of the mineral being produced by Canada

And one of the following:

1. Be essential to Canada’s economic or national security

2. Be required for the national transition to a sustainable low-carbon and digital economy

3. Position Canada as a sustainable and strategic partner within global supply chains

Define a Magmatic Ore Deposit

Masses of igneous rock enriched in useful chemical elements to such an extent that it is feasible to mine them at a profit.

What is the source of most magmatic ore deposits?

Most of these types of ore-forming magmas originate from the melting of mantle peridotite during regional extension

What minerals does peridotite contain?

Ol + Opx + Cpx ± pl/sp/gt

pl = plagioclase

sp = spinel

gt = garnet

Provide 2 examples of regional extension processes

• Rifting

• Mantle plumes

Where are metals extracted from in most magmatic ore deposits?

Metals are extracted from the source during the partial melting of mantle peridotite

How do most magmatic ore deposits form? What processes concentrate that element of interest?

Ore deposits form when Magma is transported through the crust to a new site and undergoes phase separation and mechanical sorting into small volumes that concentrate the element of interest.

What collects the element of interest?

• A mineral (oxide)

• An immiscible melt (sulphide liquid) with high enough concentration to separate from the melt

What is the transport system of Magmatic deposits?

Magma

• can transport minerals/elements of interest through crust to a new site

What is the trap of a Magmatic Ore Deposit?

• Layer

• Irregularity in the magma chamber floor/conduit (settling crystals)

What are the main Ti - bearing Ore minerals? (2)

1. Ilmenite (FeTiO₃)

2. Rutile (TiO₂)

What are the main V - bearing Ore mineral? (1)

Magnetite (Fe₃O₄)

What are some uses for Titanium?

TiO2 White pigment

• Paint

• Plastics

• Paper

• Food (white candies and coffee mate)

• cosmetics (cream, UV protection)

Ti Metal

• Aerospace industry

• automobile industry

• medicine

• sports equipment

• jewellery

What are some uses for Vanadium?

V metal

• steel additive (80%)

• bonding agents

• ceramics

• magnet

What are some variables that may affect metal prices?

• Supply-and-demand

• societal demands

• new technologies

• political instability

What is the general relationship between price and crustal abundance?

Inverse relationship between Price and Crustal abundance

What are the two main Ti-V oxide ore deposit types?

1. Layered intrusion-hosted magnetite (V) deposits

2. Proterozoic anorthosite-hosted ilmenite (Ti) deposits

What are two examples of a layered intrusion-hosted magnetite (V) deposits? Where is the magnetite located in both of these intrusions?

2.05 Ga Bushveld Complex, South Africa

• Magnetite layers at the top of the intrusion

260 Ma Panzhihua intrusion China

• Magnetite layers near base of intrusion (unusual)

What are some characteristics of a layered intrusion-hosted magnetite (V) deposit?

• Stratiform sequence of cumulate rocks

• V-rich layers deposited on floor of magma chamber during fractional crystallization (FC) following the saturation of titanomagnetite (~1000’C) in evolved basaltic magma (Low MgO, High FeO)

What does FC stand for?

Fractional Crystallization

At what temperature is there saturation of titanomagnetite?

~ 1000 degrees Celsius

How can we tell if basaltic magma is evolved using it’s content?

Low MgO - leaves during the crystallization of Olivine since it’s incorporated in forsterite (Mg₂SiO₄)

High FeO - a reducing (low-oxygen) environment does not allow oxides to form right away

What are two examples of Proterozoic anorthosite-hosted ilmenite (Ti) deposits?

1.03 Ga Lac Tio deposit, Lac Allard anorthosite, Quebec

0.93 Ga Tellnes deposit, Rogaland anorthosite, Norway

What are the earliest and latest ages of Proterozoic anorthosite-hosted ilmenite (Ti) deposits?

Earliest = Neoproterozoic

Latest = Mesoproterozoic

How thick is the Bushveld Complex deposit in South Africa?

6-8 km thick

Was the Bushveld Complex made from one or more magmatic inputs?

100s of magmatic inputs over several million years

Why is there an increasing abundance of tabular plagioclase upsection? Name the process that creates this.

Phase separation and density segregation

• Magnetite has a large density compared to basaltic magma

• Plagioclase has a similar density to basaltic magma

While both minerals are crystallizing, the density differences of these crystals will cause both crystal phases to separate from the basaltic melt

What mineral does Vanadium (V) prefer to be incorporated into?

Magnetite

How does the V content of the remaining magma change during progressive fractional crystallization?

• The first magnetite layers to crystallize have the highest V content

• The remaining magma become progressively depleted in V during fractional crystallization of upper zone magma

What is the percent of plagioclase present in anorthosite?

>90% plagioclase

Why do the magnetite layers repeat (not one big magnetite layer) in the Bushveld Complex?

May be due to small pressure fluctuations in the magma chamber, which change the relative stability during crystallization

How much of the world’s vanadium production comes from the bushveld complex?

50% of the world vanadium production

How much ilmenite is present to name a rock Ilmenitite?

>50 modal%

What minerals are in Nelsonite?

ilmenite and apatite

What is this ore called and what are its mineral components?

Hemo-ilmenite with lamellae (exsolution) texture

• Pinkish-grey ilmentite (FeTiO₃)

• Light grey hematite (Fe₂O₃)

Note: the exsolution is caused by the two different Fe states (3+ and 2+)

What is Mangerite?

Opx-bearing monzonite

What is Charnockite?

Opx-bearing granite

What does AMCG stand for?

AMCG = anorthosite-mangerite-charnockite-granite plutonic suite

What ages do most Anorthosites range? answer should contain both in Ga and time period

1.43-0.93 Ga Mesoproterozoic

What structures are in the Lac Tio Deposit in Quebec?

Composite (granite-rich) plutons with many intrusions crystallized over several million years

How much of the world’s ilmenite production is from the Lac Tio “supergiant“ deposit?

12-17% of world ilmenite production

What were the average grades of hemo-ilmenite pre-mining?

Grades of 66% hemo-ilmenite

What do these geochemistry graphs provide evidence for?

Evidence for multiple mixing (replenishment/magma injections) after periods of fractional crystallization (FC)

• FC = decreasing Cr-in-ilmenite

• Mixing = increasing Cr-in-ilmenite

How did scientists interpret the Lac Tio deposit?

Interpreted as the “keel“ of a dike where dense ilmenite accumulated

• Source of Ti is mantle-derived melt

• crystallization of plagioclase/anorthosites leaves Fe + Ti rich residual magma

• Fe-Ti-rich residual magma is transported and injected into syn-magmatic intrusions/dikes

• ilmenite begins to crystallize at ~1000’c as the Fe-Ti enriched residual melt cools and segregates (by density) to the bottom/keel of the dikes where it is trapped

What is the source, transport, and trap of the Lac Tio (Ti) Deposit?

• Source = Ti mantle-derived melt

• Transport = Fe-Ti-enriched residual magma intrusions/dikes

• Trap = keel/bottom of residual magma dike

What is the source, transport, and trap of the Bushveld (V) Deposit?

• Source = mantle source to a V-rich basaltic magma

• Transport = Metals are dissolved in magma until saturation/crystallization at ~1000’c

• Trap = phase separation and density segregation - accumulation by gravity on the floor of a large magma chamber