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Chemical Oceanography, 4th Edition
both ways; that is, reverse weathering or igneous rocks are formed during seafloor spreading. The earlier models gave a reasonable balance between the rocks and the sediments for
most elements (see Table 3.12). For the elements B, S, Cl, As, Se, Br, and I, an excess was found,
presumably of a volcanic origin. With the recent discovery of the flux of materials coming
from hydrothermal vents, these values will need some modification for some elements.
Mn (µg kg
–1 )
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Depth (m)
0
500
1000
1500
2000
2500
3000
Figure 3.22
Profile of manganese (Mn) in the Pacific Ocean showing hydrothermal input from Mid- Pacific Ridge.
δ
3 He (%)
Depth (m)
0
1000
2000
3000
0
10
20
30
40
50
Figure 3.23
Profile of helium (He) in the Pacific Ocean showing hydrothermal input from Mid- Pacific Ridge.