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  

作　　者：Samndong Cyril Tufoin Cheo Emmanuel Suh Tabod Charles Tabod George Lemewihbwen Ngiamte 

机构地区：[1]Department of Geology,Mining and Environmental Science,The University of Bamenda,B.P.39,Bambili,North West Region,Cameroon [2]Economic Geology Unit,Department of Geology,University of Buea,P.O.63,Buea,South West Region,Cameroon [3]Department of Physics,Faculty of Science,The University of Bamenda,B.P.39,Bambili,North West Region,Cameroon [4]Department of Geology,Pan-African University Life and Earth Sciences Institute(PAULESI),University of Ibadan,Ibadan,Nigeria

出　　处：《Acta Geochimica》2024年第4期677-706,共30页地球化学学报（英文）

摘　　要：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 northwestern 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.TheƐ_(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.

关 键 词：Bulk geochemistry RB-SR SM-ND Mitzimevin High-grade iron ore 

分 类 号：P618.31[天文地球—矿床学]