Assignment 3 - How Diamonds Form Flashcards
What is a diamond made of?
Diamond (an graphite) are made of carbon.
What are the different layers within the earth
- Crust
- Mantle
- Core
Why is plate tectonics important to diamond formation?
Subduction of plates is an essential part of diamond formation. Most diamond deposits are found on cratons or in the areas surrounding them.
A natural, inorganic substance with characteristic chemical composition and usually characteristic structure
Mineral
A natural material composed of one or more kinds of mineral
Rock
The surface and outermost layer of the earth.
Crust
The layer between the earth’s curst and core
Mantle
The earth’s innermost layer
Core
The layer that contains the crust and the uppermost part of the mantle
Lithosphere (100km)
The layer between the upper and lower mantles
Transition Zone
(410km to 660k)
The theory of the formation, structure and movement of earth’s landmasses.
Plate tectonics.
Any molten rock within the earth
Magma
Where in the earth’s structure are the best conditions for diamond formation?
Diamonds form under cratons, which are located only under continental land mass.
Ancient, large, and stable parts of the eartht’s continental crust
Cratons
A large, downward-protruding portion of the lithosphere under a craton
Mantle keel
How do pressure and temperature make diamond the hardest substance on earth?
Pressure from 40 - 80 kBar.
Temperature from 900°C - 1’400°C
The rate of temperature increase with depth in earth
Geothermal gradient
What are the current models of diamond formation?
litospheric (in mantle keels below cratons)
superdeep (in transition zone and lower mantle)
What types of rocks produce diamonds?
Periodite (Ignenous Rock) & Eclogite (Metamorphic Rock)
Why do some diamonds (0.1%) have blue color?
Blue color mostly comes from boron trace, which originates from oceanic plates.
A category of rocks from a molten state
Igneous Rock (Magmatisches Gestein)
A category of rocks that have been altered by heat and pressure.
Metamorphic Rock (Metamorphes Gestein)
A class of chemical compounds that contain carbon and oxygen
Carbonate
Subduction
Process in which two crustal plates collide, forcing one under the other
Which rocks deliver diamonds to the surface?
Kimberlite and lamproite transport diamonds to the surface, but diamonds are not formed in them.
Rare diamond that forms in the continental crust at or near the earth’s surface due to meteorite impact or tectonic plate collision
Crustal diamond
An aggregate of many randomly oriented interlocking tiny diamond crystals that is the toughest form of diamond
Carbonado
How do diamonds reach the surface?
Through emplacement of rocks from the cratons to the surface.
When were diamonds delivered to the surface?
Diamonds exist today were delivered to the surface between 2.5bn and 20 million years ago.
Kimberlite
An ingeous rock, that transports diamonds to the surface. It forms in the middle of the cratons.
Lamproite
An ingeous rock, rarer than kimberlite, that transports diamonds to the surface.
Emplacement
A geologic process that delivers materials to the surface.
Pipe
A deep vertical formation at the earth’s surface that results from a kimberlite or lamporite emplacement.
How does metasomatism affect lithospheric diamond formation?
It removes oxygen
What layer of the earth includes continental and oceanic components?
Transition zone
What is characteristic of superdeep CLIPPIR diamonds?
- Cullinan-like
- Large
- Inclusion-poor
- Pure
- Irregular
- Resorbed
How many carats must bulk sampling produce for accurate evaluation of a primary deposit?
2’000 Carats
(in a sample of 5’000-10’000 tons)
What are three most well-known examples for superdeep diamonds?
- CLIPPR
- Juìna (Brazil)
- Blue Diamonds
