Download Oxygen

Oxygen, noble gases
Oxygen (O)
• Universe: 10000 ppm (by weight)
• Sun: 9000 ppm (by weight)
• Carbonaceous meteorite: 4.1 x 105 ppm
• Atmosphere: 2.095 x 105 ppm
• Earth's Crust: 4.74 x 105 ppm
Oxygen is magmatic processes
It is principally as a lithophile element, occurring
preferentially in the crust and mantle. It is the second most
abundant element (30 wt%) in the bulk Earth and the most
abundant element in the crust and mantle ( 62.55 and
approximately 60 atom%, respectively). Thus, oxygen is a
major constituent of nearly all minerals. It is the basis of the
tetrahedral [SiO4 ]4- ion that polymerizes to form all
silicates, as well as the anionic building blocks (e.g. CO3,
SO4, PO4, or OH ions) of the most common non-silicate
minerals.
Oxygen
Oxygen is extremely reactive, and forms compounds with
every element except He, Ne, and Ar. The most abundant
compounds of oxygen are oxides: binary compounds
with oxygen in the -2 oxidation state. Transition metals
generally combine with oxygen to form basic oxides
such as Fe2O3.
Although elemental oxygen occurs principally in the rocky
solid Earth, its considerable abundance in the atmosphere
also places it among the atmophile elements in the
classification of Goldschmidt.
Oxygen
Dioxygen comprises 20.946 vol% of the bulk atmosphere at
sea level. It is formed principally as a product of
photosynthesis, which began with the evolutionary
appearance on Earth of prokaryotic cyanobacteria (bluegreen algae) in the early Archean eon, about 3.5-3.8 Ga
ago, drastically changing what would previously have been
a virtually anoxic atmosphere formed of volcanic emissions.
Oxygen is an important species in controlling redox
conditions in natural waters: biologically mediated
reduction of O2 to H2O is the predominant oxidizing
reaction in the aqueous environment.
Helium
Universe: 2.3 x 105 ppm (by
weight)
Sun: 2.3 x 105 ppm (by weight)
Atmosphere: 5.2 ppm
Earth's Crust: 0.008 ppm
Seawater: 7 x 10-6 ppm
Helium
After hydrogen, helium is the most abundant element in the
universe (~6.5%). The  particles emitted from uranium,
thorium radium and polonium are doubled ionized 4He
nuclei. Due to its extremely low abundance. 4He is formed
by the radioactive decay of U and Th.
On Earth we can roughly distinguish four different
reservoirs of helium, each with different isotopic signatures:
air, continental crust, upper mantle and lower mantle.
Using these different isotopic signatures, helium can be a
valuable tracer to determine the origin of erupted rocks and
various terrestrial fluids, in particular due to its low
atmospheric abundance and the small risk of air
contamination.
Argon
Universe: 200 ppm (by weight)
Sun: 70 ppm (by weight)
Atmosphere: 9300 ppm
Earth's Crust: 1.2 ppm
Seawater: 0.45 ppm
Argon
Argon is the most abundant noble gas in the Earth's
atmosphere. It is generally accepted that the terrestrial
atmosphere was degassed from the Earth's mantle. Recent
observations on basalt glasses show that the lower mantle
(below 670 km depth) is less outgassed than the upper
mantle. In the lithosphere it forms from radioactive decay of
40K isotope. This processes is the basic of potassiumargon radiometric age method.
Neon
Universe: 1300 ppm (by weight)
Sun: 1000 ppm (by weight)
Atmosphere: 14 ppm
Earth's Crust: 3 x 10-3 ppm
Seawater: 1.2 x 10-4 ppm
Krypton
Universe: 0.04 ppm (by weight)
Atmosphere: 1.14 ppm
Earth's Crust: 1 x 10-5 ppm
Seawater: 2.1 x 10-4 ppm
Noble gases in magmatic rocks (g/t):
He – 0,003
Ne – 0,00007
Ar – 0,04
Nobel gases in troposphere (vol.%):
He – 5,24 . 10-4
Ne – 1,8 . 10-3
Ar – 0,93
Kr – 1 . 10-4
Xe – 8 . 10-6
Radon (Rn)
Universe: xxx (by weight)
Atmosphere: xxx ppm
Earth's Crust: xxxx 10-5 ppm
Seawater: xxx 10-4 ppm
Radon
Rn occur in nature, one each in the 238U, 235U and 232Th
decay series. In closed systems such as the interior of well
crystallized minerals, radon usually comes to radioactive
equilibrium withits parents so that its abundance varies with
uranium or radium. In poorly crystalline or fine-grained
materials such as soils and recent sediments, newly
formed Rn atoms recoiling from alpha emission can travel a
few tens of nanometers through the host solid and emanate
into pore space or cracks. The concentrations of Rn in soil
gas depends on the abundance of U and Ra in the soil.
The reason of high Rn concentration can be some
monazite or xenotime clasts in the soil.
Actinides
Actinium: terrestrial occurrence arises from the decay of
235U. This metal is found in trace quantities in uranium
minerals (ng/g of pitchblende – the mixture of U-oxides).
Radium: it occurs in the 238U, 235U and 232Th decay
series. However, it may substitute for K+ in minerals
because of its large radius. Radium may become at least
partly separated from its parents in young igneous rocks,
weathered and altered minerals, recent sediments, the
biosphere and natural water. In weathering and soil
formation, Ra is slightly to moderately enriched in plants
and in soil organic matter relative to its parents U and Th,
which tend to be more concentrated in the Fe oxides of the
soil.