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contribution, they record that the lunar soil has an abundance of this element
between 100 and 1000 ppm. The nitrogen concentration decreases with depth from
several thousands to 100 ppm at
150 nm depth in the grains.
Sano et al. (1998, also see Itihara and Honma 1979) determined the global
*
ux
of nitrogen from the earth. They found that nitrogen
flux from island arcs is
10
8
mol/year. This is related to large
6.4
×
flux of subducted sedimentary nitrogen,
10
8
mol/year) have a relatively
smaller but measurable subducted component. They observed that volcanic gas and
hydrothermal samples show a concentration of mantle-derived nitrogen of 9
whereas nitrogen
flux from back-arc basins (5.6
×
30 %,
which is in agreement with those of phenocrysts in subareal volcanic rocks and
-
fluid inclusions in hydrothermal minerals (Sano et al. 1998, also see Itihara and
Tainosho 1989). They considered that in general nitrogen content in island arc
samples is dominated by atmospheric and/or sedimentary components (also see
Williams et al. 1989). They thought that sedimentary nitrogen in the sample may be
attributed to subducted marine sediments. Their concentration in volcanic gas and
fluids in island arc region can be indeed very high: 40
-
52 % (Papandayan),
47
57 % (Galeras crator), 47 % (Purace) and 65 % (Colima).
Figure
15.1
of Sano et al. (1998, also see Itihara and Honma 1983) showed the
schematic diagram of global in
-
ux of nitrogen into the mantle of the earth. It may
be noted that back-arc basin and island arc indicate signi
flux of
nitrogen from the earth. This figure also demonstrates that in the island arcs regions,
there is a large
cant mantle
flux of subducted sedimentary nitrogen, whereas back-arc basin has
a relatively smaller concentration, this is because the total length of subduction zone
(continental island arc) is 4
10
4
km, whereas about 40 % of the subduction is not
accompanied by back-arc basin volcanism, such as South and Middle America
(Uyeda and Kanamori 1979).
×
6
Nitrogen flux (x10 mol/a)
Fig. 15.1 A schematic diagram of nitrogen flux from the solid Earth. Note that both back-arc
basin and island arc indicate significant mantle flux of nitrogen. Contribution of hot spot region is
significantly smaller (after Sano et al. 2001)
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