School of Engineering and Science - Jacobs University

Nd isotopes in 2.9 Ga Archean surface seawater 387
of the Mozaan IF samples (Fig. 4). The presence of positive
Eu anomalies is clear evidence that REY from high-T
hydrothermal inputs influenced the continental shelf environment
that hosted the Mozaan IFs.
For constraints on ancient hydrothermal fluxes, modern
black smoker fluids offer the best analogs for the trace
element compositions of high-T fluids which contributed
to the REY distribution in Archean iron formations.
For the Mozaan IFs, the magnitude of the positive Eu
anomalies generally compare well with data for other
IFs (Fig. 5). However, the general REY distributions of
the Mozaan IFs are significantly different when compared
to well studied examples such as the 3.7 Ga Isua IF of
Greenland (Bolhar et al., 2004) and the 2.5 Ga Kuruman
IF from South Africa (Bau and Dulski, 1996), though
regardless of age, these iron formations display the seawater
characteristics of marine chemical sediments (Fig. 5).
Conservative mixing calculations indicate that a high-T
hydrothermal fluid contribution of less than 0.1% is adequate
for producing the Eu/Sm ratios observed within
the Pongola and Kuruman IFs, and reasonably accounts
for most of the Eu/Sm ratios observed in the Isua IFs
REY/WMS
10 1
10 0
high-T hydrothermal fluid (x10 5 )
10 -1
10 -2
10 -3
Isua IF (x2)
Kuruman IF
top/bottom IFs
middle IFs