TITLE:
Contrasting Depositional Environment of Iron Formation at Endengue Area, NW Congo Craton, Southern Cameroon: New Insights from Trace and Rare Earth Elements Geochemistry
AUTHORS:
Robinson Tchatchueng, Timoléon Ngnotué, Evine Laure Tanko Njiosseu, Sylvestre Ganno, Hervé Wabo, Jean Paul Nzenti
KEYWORDS:
Endengue BIFs, Suboxic or Anoxic, Oxic, Depositional Environment, Ntem Complex
JOURNAL NAME:
International Journal of Geosciences,
Vol.12 No.3,
March
25,
2021
ABSTRACT: The
Endengue Banded Iron Formation (BIF) is located in the northwestern edge of the
Congo craton in Cameroon. Here, we
report geochemical data of trace and rare earth elements (REE) of the Endengue
BIF samples from the Archean Ntem complex and investigate their environmental
setting. Two types of BIF occur at Endengue area, both containing minimal
contamination from terrestrial material. Total REE (ΣREE) contents in the Type 1 BIF are extremely low,
ranging from 0.34 to 1.83 ppm, similarly to pure chemical sediments while Type
2 BIF displays ΣREE contents ranging from 2.98 to 24.26 ppm. The
PAAS-normalized REE + Y patterns of the two BIF
types display LREE enrichment relative to HREE and weak positive Eu anomaly,
most likely suggesting that the source of iron and siliceous of the Endengue
BIFs is mainly from the contribution of low-temperature hydrothermal alteration
of the crust. Type 1 BIF shows very low Nd content (* and positive Ce anomalies which suggests suboxic or anoxic seawater
similar to the depositional environment of Elom BIF in Archean Ntem complex. In
contrast, Type 2 BIF displays low to moderate Nd contents (1 and 100 ppm with
the exception of sample LBR65) with negative correlation between Nd and Ce/Ce* and negative Ce anomalies.
These features indicate precipatation of Type 2 BIF from oxic iron-rich solution
that changed to oxidized surface by rapid precipitation of the hydrothermal Fe.
The Endengue BIFs were deposited in the continental margin ocean in presence of
low-temperature hydrothermal fluids mixed with seawater, similar to
Paleoproterozoic Kpwa-Atog Boga
BIFs within the Nyong group and other Paleoproterozoic Superior-type BIFs worldwide.