Mineral Evolution, Exercises of Geology

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Mineral Evolution

THEMES

• The origins and evolution of minerals
• The origins and evolution of life
• The rise of oxygen
• The co-evolution of life and rocks

What Is Mineral Evolution?

A change over time in:

• The diversity of mineral species
• The relative abundances of minerals
• The compositional ranges of minerals
• The grain sizes and shapes of minerals

A Comment on “Evolution”

• The word “evolution” has several meanings
• Change over time, as in Bowen’s “ Evolution of the Igneous Rocks .”
• Implication of complexification
• Congruency
• But NOT Darwinian evolution!

Mineral Evolution

New minerals form through a combination of chemical, physical, and biological processes.

It came from… Supernovas

It came from… Supernovas Elements that form in supernovas

Diamond & Graphite Graphite Diamond

“Ur”-Mineralogy

Pre-solar grains contain about a dozen micro- and nano-mineral phases:

• Diamond/Lonsdaleite
• Graphite (C)
• Moissanite (SiC)
• Osbornite (TiN)
• Nierite (Si 3 N 4 )
• Rutile (TiO 2 )
• Corundum (Al 2 O 3 )
• Spinel (MgAl 2 O 4 )
• Hibbonite (CaAl 12 O 19 )
• Forsterite (Mg 2 SiO 4 )
• Nano-particles of TiC, ZrC, MoC, FeC, Fe-Ni metal within graphite.
• GEMS (silicate glass with embedded metal and sulfide).

Mineral Evolution:

How did we get from a dozen

minerals (with 10 essential

elements) to >5000 minerals

(with 72 essential elements)

on Earth today?

The Birth of Stars and Planets The Nebular Hypothesis

Stage 2: Aqueous alteration, metamorphism and differentiation of planetesimals

• Water began exsolving from melt and reacted with solids
• When planetismals were large enough, dense material sunk and light material floated
• Higher pressure caused low grade metamorphism

Stage 2: Alteration of planetesimals by

heat, water, and impacts

~250 mineral species

• Feldspars
• Quartz
• Micas
• Clays
• Zircon
• Calcite (4.56-4.55 billion years)

Stages 1 and 2: Meteorites ~250 mineral species In these early stages all of Earth’s near- surface compositional complexity was present, but it was not manifest in a diversity of unusual mineral species. In other words, minor and trace elements substituted for more common elements in the major rock forming minerals, instead of forming their own minerals.

Stage 3: Planet Formation

The formation of planets enabled new combinations of pressure and temperature