Banded Iron Formations in Congo: A Review

• 영문명: Banded Iron Formations in Congo: A Review
• 발행기관: 대한자원환경지질학회
• 저자명: Yarsé Brodivier Mavoungou Anthony Temidayo Bolarinwa Noël Watha-Ndoudy Georges Muhindo Kasay
• 간행물 정보: 『자원환경지질』56권 6호, 745~764쪽, 전체 20쪽
• 주제분류: 자연과학 > 지질학
• 파일형태: PDF
• 발행일자: 2023.12.31

영문 초록

In the Republic of Congo, Banded iron formations (BIFs) occur in two areas: the Chaillu Massif and the Ivindo Basement Complex, which are segments of the Archean Congo craton outcropping in the northwestern and southwestern parts of the country. They show interesting potential with significant mineral resources reaching 2 Bt and grades up to 60% Fe. BIFs consist mostly of oxide-rich facies (hematite/magnetite), but carbonate-rich facies are also highlighted. They are found across the country within the similar geological sequences composed of amphibolites, gneisses and greenschists. The Post-Archean Australian Shale (PAAS)-normalized patterns of BIFs show enrichment in elements such as SiO2, Fe2O3, CaO, P2O5, Cr, Cu, Zn, Nb, Hf, U and depletion in TiO2, Al2O3, MgO, Na2O, K2O, Sc, Th, Ba, Zr, Rb, Ni, V. REE diagrams show slight light REEs (rare earth elements; LREEs) compared to heavy REEs (HREEs), and positive La and Eu anomalies. The lithological associations, as well as the very high (Eu/Eu*)SN ratios> 1.8 shown by the BIFs, suggest that they are related to Algoma-type BIFs. The positive correlations between Zr and TiO2, Al2O3, Hf suggest that the contamination comes mainly from felsic rocks, while the absence of correlations between MgO and Cr, Ni argues for negligeable contributions from mafic sources. Pr/Pr* vs. Ce/Ce* diagram indicates that the Congolese BIFs were formed in basins with redox heterogeneity, which varies from suboxic to anoxic and from oxic to anoxic conditions. They were formed through hydrothermal vents in the seawater, with relatively low proportions of detrital inputs derived from igneous sources through continental weathering. Some Congolese BIFs show high contents in Cr, Ni and Cu, which suggest that iron (Fe) and silicon (Si) have been leached through hydrothermal processes associated with submarine volcanism. We discussed their tectonic setting and depositional environment and proposed that they were deposited in extensional back-arc basins, which also recorded hydrothermal vent fluids.

목차

1. Introduction

2. Overview on Band Iron Formations in West-Central Africa

3. Geological Setting

4. Banded Iron Formations in Congo

5. Geochemistry

6. Discussion

7. Conclusion

Conflicts of Interest

Acknowledgement

Funding

References

키워드

Banded iron formations Republic of Congo Chaillu Massif Ivindo Basement Complex Tectonic setting