近日，喀麦隆巴门达大学Samndong Cyril Tufoin团队研究了喀麦隆西部梅奥-宾卡新元古代花岗岩型石英-磁铁矿巨脉的野外分布和岩石化学特征。相关论文于2025年8月21日发表在《地球化学学报》杂志上。

在喀麦隆西部梅奥宾卡（Mayo Binka）中部非洲褶皱带（CAFB）的新元古代花岗岩体中，研究组分析了与剪切带相关的神秘巨型石英磁铁矿脉，利用新领域、矿石显微镜、体岩地球化学和磁铁矿微化学数据，阐明了它们的成因和矿床类型。在梅奥宾卡远景区，磁铁矿共生为最早的铁氧化物相。其部分被机械孪晶赤铁矿和马铁矿取代，并伴有钛铁矿的析出结构，表明热液作用。该磁铁矿矿石Fe₂O₃含量高（~81 wt%）， SiO₂含量低（~15.7 wt%）， Al₂O₃含量低（~0.48 wt%）， TiO₂含量低（~0.01 wt%）， P₂O₅含量低（~0.03 wt%）。

稀土元素（REE）特征为ΣREE含量低（~12.62 ppm），轻稀土（La/YbCN~4.16）富集于重稀土（Gd/YbCN~1.48）， Eu负异常轻微（~0.97），La负异常强烈（~0.52），表明磁铁矿矿床成因为高温、火成岩而非沉积成因。磁铁矿的显微化学特征显示出高浓度的Ti （~16 wt%）、V （~3881 ppm）、Al （~ 12031 ppm）、Mn （~3058 ppm）和Ga (~39 ppm)，表明在低氧逸度（fO₂）条件下岩浆结晶，这与岩石学观测显示的热液特征相反。

微量元素判别图将梅奥宾卡远景区划分为铁-钛-钒岩浆磁铁矿矿床。结合岩石学、矿物学和地球化学资料，结合花岗岩体、断裂岩和偏牛油果沉积岩（片岩、角闪岩、片麻岩和石英岩）的野外结合，表明梅奥滨卡块状铁脉可能形成于复杂的地球动力学大陆弧后环境，岩浆沉积和构造作用控制了成矿的定位和演化。

附：英文原文

Title: Neoproterozoic granitoid-hosted quartz-magnetite mega veins at Mayo Binka, western Cameroon: Field disposition and petrochemical characteristics

Author: Tufoin, Samndong Cyril, Ngiamte, George Lemewihbwen, Suh, Cheo Emmanuel, Mbouni, Sirri Sarah, Vishiti, Akumbom

Issue&Volume: 2025-08-21

Abstract: Enigmatic shear zone-related mega quartz-magnetite veins, hosted by Neoproterozoic granitoids of the Central African Fold Belt (CAFB) in Mayo Binka, western Cameroon, are investigated using new field, ore microscopy, bulk-rock geochemistry, and magnetite microchemical datasets to elucidate their origin and deposit type. Magnetite is paragenetically the earliest Fe-oxide phase in the Mayo Binka prospect. Its partial replacement by mechanically twinned specular hematite and martite, along with ilmenite exsolution textures, indicates hydrothermal processes. The magnetite ores are characterized by high Fe2O3 (~81 wt%) and low SiO2 (~15.7 wt%), Al2O3 (~0.48 wt%), TiO2 (~0.01 wt%), and P2O5 (~0.03 wt%) contents. The rare earth element (REE) signature, marked by low ΣREE content (~12.62 ppm), enrichment in LREE (La/YbCN~4.16) over HREE (Gd/YbCN~1.48), a slight negative Eu anomaly (~0.97), and a strong negative La anomaly (~0.52), suggests elevated-temperature, igneous origin for the magnetite deposits rather than sedimentary. Magnetite microchemistry reveals high concentrations of Ti (~16 wt%), V (~3881 ppm), Al (~12,031 ppm), Mn (~3058 ppm), and Ga (~39 ppm), indicating magmatic crystallization under low oxygen fugacity (fO2) in contrast to the hydrothermal signatures shown by petrographic observations. Trace element-based discrimination diagrams classify the Mayo Binka prospect as an Fe–Ti–V magmatic magnetite deposit. Field association with granitoids, fault rocks, and metavocanosedimentary rocks (schist, amphibolite, gneiss, and quartzite), coupled with petrographic, mineralogical, and geochemical datasets, suggests that the Mayo Binka massive ferriferous veins likely formed in a complex geodynamic continental back-arc setting, where magmatic sedimentary and tectonic processes controlled the localization and evolution of the mineralization.

DOI: 10.1007/s11631-025-00808-4

Source: https://link.springer.com/article/10.1007/s11631-025-00808-4