B. Fractionation Mechanisms of Selected Elements
I. Hydrogen
Until 1931 it was assumed that hydrogen consisted of only one isotope. UREY et al. (1932a, b) established the presence of a second, heavy,
stable isotope, which was called deuterium. WAY et al. (1950) gave the
following average abundances of the stable hydrogen isotopes:
IH:99.9844% ,
2D: 0.0156%.
(In addition to these two stable isotopes there is a third naturally
occurring but radioactive isotope, 3T, tritium, with a half-life of approximately 12.5 years.)
The isotope geochemistry of the stable hydrogen isotopes is one of
the most interesting, for several reasons.
1) Hydrogen shows by far the largest relative mass difference between its two stable isotopes. This results in hydrogen showing the largest fractionations for stable isotopes on Earth up to 70% and even more
in lunar material (see Fig. 7).
Escape of "light" H
from the atmosphere
/(
~M~teoriF,yt\l~~Ls~
~ Ocean water
///
~
/
\ ~ Sedimentary rocks
\, _
Igneous and metamorphic rocks
,
/
'~ Juvenile water?
~ OH-minerals from deep-seated origin?
~~~?,ElS~W1~~1i1~~i,qI ,rT)?W,i?,IZi, .!.c?~bo~9reauT, cHoM~'ifeT,.t~f)?~,ing!,,{i,qlt'i~c;L
I
I
I i !
I
!
!
I
I
!
I
200
150
100
50
0
-50 -100 -150 -200 -250 -300 -350
b 0 in ·1 ••
Fig. 7. D/H ratios of some important terrestrial compounds (<'i-variations in %0
relative to SMOW
I. Hydrogen
Until 1931 it was assumed that hydrogen consisted of only one isotope. UREY et al. (1932a, b) established the presence of a second, heavy,
stable isotope, which was called deuterium. WAY et al. (1950) gave the
following average abundances of the stable hydrogen isotopes:
IH:99.9844% ,
2D: 0.0156%.
(In addition to these two stable isotopes there is a third naturally
occurring but radioactive isotope, 3T, tritium, with a half-life of approximately 12.5 years.)
The isotope geochemistry of the stable hydrogen isotopes is one of
the most interesting, for several reasons.
1) Hydrogen shows by far the largest relative mass difference between its two stable isotopes. This results in hydrogen showing the largest fractionations for stable isotopes on Earth up to 70% and even more
in lunar material (see Fig. 7).
Escape of "light" H
from the atmosphere
/(
~M~teoriF,yt\l~~Ls~
~ Ocean water
///
~
/
\ ~ Sedimentary rocks
\, _
Igneous and metamorphic rocks
,
/
'~ Juvenile water?
~ OH-minerals from deep-seated origin?
~~~?,ElS~W1~~1i1~~i,qI ,rT)?W,i?,IZi, .!.c?~bo~9reauT, cHoM~'ifeT,.t~f)?~,ing!,,{i,qlt'i~c;L
I
I
I i !
I
!
!
I
I
!
I
200
150
100
50
0
-50 -100 -150 -200 -250 -300 -350
b 0 in ·1 ••
Fig. 7. D/H ratios of some important terrestrial compounds (<'i-variations in %0
relative to SMOW