Geoscience Reference
In-Depth Information
Mo (PPM)
Mo (PPM)
024
6
8
0
0
030
050
0
100
200
120
400
140
600
800
160
1000
180
1200
1400
200
South Africa
2.5 to 2.6 billion
years old
Western Australia
2.5 billion
years old
Figure 7.3. molybdenum concentrations from rocks in south Africa and western Australia.
Values in excess of the gray box (average for the continental crust and river particles)
represent enrichments and evidence for “whiffs” of oxygen during the Archean eon.
Again, way back in 1962, Dick Holland may have had the right idea.
In
chapter 5
we introduced the idea that various oxygen-reactive gases
spew out of volcanoes and react quickly with oxygen in the atmosphere.
If the rate of introduction of these gases is fast enough, they will over-
whelm the liberation rates of oxygen to the atmosphere, which as we
saw in
chapter 5,
is controlled by the burial rates of organic carbon and
pyrite sulfur. If this is the case, oxygen liberation to the atmosphere can
