School of Engineering and Science - Jacobs University

10 -2 360 °C hydrothermal fluid
10 -3
10 -4
sample/PAAS
10 -5
10 -6
10 -7
10 -8
10 -9
average world seawater
La Ce Pr Nd PmSm Eu Gd Tb Dy Y Ho Er Tm Yb Lu
Figure 4. REY distributions in average world seawater and high-T hydrothermal fluid from the mid-
Atlantic ridge normalized to continental crust as represented by PAAS (McLennan, 1989). Seawater
data are the average of 172 worldwide analyses of all depths (average depth 1560 m) for which
complete REY datasets are available (Zhang and Nozaki, 1996; Alibo and Nozaki, 1999; Bau et al.,
1997b; Nozaki et al., 1999; Nozaki and Alibo, 2003). Hydrothermal fluid data for sample BS-07-3/3 of
Bau and Dulski (1999). Note strong negative Ce anomaly in seawater and strong positive Eu anomaly in
high-T hydrothermal fluid.
temperature (T= 360 °C) hydrothermal fluids emanating from the mid-Atlantic oceanic
ridge (MAR).
1.5.2. Rare earth elements in seawater
The abundances of the REY in seawater are extremely low relative to their crustal
averages, with world seawater concentrations ~10 -7
of the levels found in upper
continental crust (see Figure 4). Higher REY abundances are typically found in river
waters and pore waters of marine sediments, though not as high as the concentrations
observed for high-T hydrothermal fluids (Figure 5). It is reasonable that these fluids
(river water, pore water, and hydrothermal fluid) represent the primary dissolved REY
sources for the oceans of the world, and assuming this is true, it is notable that each of
these REY sources contains several times the total REY concentration that exists in
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