Bulk geochemistry, Rb–Sr, Sm–Nd, and stable O–H isotope systematics of the Metzimevin high-grade iron ore deposit, Mbalam iron ore district, southern Cameroon

• Published in: Acta geochimica Vol. 43; no. 4; pp. 677 - 706
• Main Authors: Tufoin, Samndong Cyril, Suh, Cheo Emmanuel, Tabod, Tabod Charles, Ngiamte, George Lemewihbwen
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.08.2024; Springer Nature B.V
• Subjects: Aluminum oxide; Cratons; Earth and Environmental Science; Earth Sciences; Ferric oxide; Fluids; Geochemistry; Haematite; Hematite; High temperature; Iron; Iron compounds; Iron constituents; Iron ores; Leaching; Low concentrations; Magnetite; Mass balance; Mineral deposits; Mineralization; Original Article; Plumes; Seawater; Silica; Silicates; Silicon dioxide; Strontium 87; Strontium isotopes; Systematics; Titanium dioxide; Cameroon; Mitzimevin; Bulk geochemistry; Rb–Sr; Sm–Nd; High-grade iron ore
• ISSN: 2096-0956; 2365-7499
• DOI: 10.1007/s11631-023-00667-x

Bulk geochemistry, Sr, Nd, and O–H isotope systematics are reported for the first time on banded iron formation (BIF)-hosted high-grade iron ore at the north-western segment of Congo Craton (CC). Located in Mbalam iron ore district, Southern Cameroon, Metzimevin iron ore deposit is a hematite-magnetite BIF system, dominated by SiO 2  + Fe 2 O 3 (97.1 to 99.84 wt%), with low concentrations of clastic elements e.g., Al 2 O 3 , TiO 2 , and HFSE, depicting a nearly pure chemical precipitate. The REE + Y signature of the iron deposit displays strong positive Eu anomaly, strong negative Ce anomaly, and chondritic to superchondritic Y/Ho ratios, suggestive of formation by mixed seawater-high temperature hydrothermal fluids in oxidising environment. The 87 Sr/ 86 Sr ratios of the BIF are higher than the maximum 87 Sr/ 86 Sr evolution curves for all Archean reservoirs (bulk silicate earth, Archean crust and Archean seawater), indicating involvement of continentally-derived components during BIF formation and alteration. The Ɛ Nd (t) (+ 2.26 to + 3.77) and Nd model age indicate that chemical constituents for the BIF were derived from undifferentiated crustal source, between 3.002 and 2.88 Ga. The variable and diverse O and H isotope data (− 1.9‰ to 17.3‰ and − 57‰ to 136‰ respectively) indicate that the Metzimevin iron ore formed initially from magmatic plumes and later enriched by magmatic-metamorphic-modified meteoric fluids. Mass balance calculations indicate mineralisation by combined leaching and precipitation, with an average iron enrichment factor of > 2.67 and SiO 2 depletion factor of > 0.99. This is associated with an overall volume reduction of 28.27%, reflecting net leaching and volume collapse of the BIF protholith.