Hand specimens of iron mineralization samples from the Edea North were divided into two main facies based on their physical appearance: the banded and the massive ore (Figure 2). Bands in the banded facies are irregular and discontinuous there are made up of thin bands of ferromagnesian minerals which alternate with silica-rich microbands and the contact banding is not sharp (Figure 2(a)). Some of the studied samples displayed a trellis-like structure (Figure 3). Microscopic examinations of these samples have confirmed the irregularity of the bands. The mineralogy of the banded samples consists of iron minerals (75%), pyroxenes (25%) in the ferromagnesian bands and quartz (80%), and dominating silica-rich bands. The mineralogical composition of the massive ore includes iron minerals (45%), quartz (30%) and pyroxene (16%) with minor, ilmenite (1%), biotite (0.5%), apatite (0.5%) and amphiboles (1%). The reflected light microscopic observations revealed that the iron minerals phase is dominated by magnetite in both facies and to a lesser amount martite. All the pyro-

xenes minerals present marks of alteration and some of them are deformed within the bands (Figure 3(b)).

Magnetite in the both facies occurs as in various shapes: as irregular and elongated minerals can contain quartz inclusions of various shapes and sizes (Figure 3(a)). Magnetite also appears as cluster around pyroxenes and embedded at their limits, thus forming haloes and rolls (Figure 4(c) and Figure 4(d)). Finally magnetite occurs as disseminations in quartz matrix (Figure 4(c) and Figure 4(d)). Martite results from the alteration of magnetite is altered to martite (Figure 5) and rare inclusions of ilmenite occur within. Martite is euhedral to subhedral and it is commonly observed at the crystal interface of magnetite and silicate strip.

Quartz is the main gangue mineral identified. It displays three textural varieties including fine-grained, coarse-grained and ribbon quartz (Figure 3 and Figure 4). It occurs in band or as inclusions in magnetite or pyroxene. In addition, quartz shows a characteristic undulating texture (Figure 4(b)). The observed crystals are fractured, xenomorphic and subhedral to anhedral phases.

The pyroxenes occur as inclusions in both silica and magnetite. They are subhedral, yellow-orange, and riding in thin strips of magnetite forming rolls (Figure 3(b)) and always close or in the iron mineral phase.

Amphiboles are sometimes green xenomorphic crystals with quartz inclusions.

Electron microprobe analysis revealed that Fe₂O_3(T) contents range from 97.12% to 99.76% and between 96.11% and 97% respectively on magnetite and martite (Table 1). All other major oxides occur in low quantities except Al₂O₃ with contents as high as 2.65%.

The chemical composition of iron ore from the Edea North area is summarized in Table 2. The samples show SiO₂ contents that range from 33.8 to 51.2

wt% and Fe₂O₃ contents that vary between 40.4 and 62.9 wt% respectively. There is a very strong negative correlation (R² = −0.92) between these two oxides (Table 3). Concentrations of Al₂O₃ vary between 0.46% and 4.19% (with an average of 1.40%) and P₂O₅ concentrations are generally low (0.01% - 0.15%). The other major oxides have relatively low contents: CaO (0.01% - 0.47%), K₂O (0.01% - 0.02%), Na₂O (0.01% - 0.08%) and MnO (0.01% - 0.09%). there is a positive correlation (R² = 0.89) between Al₂O₃ and TiO₂ while Al₂O₃ and Fe₂O₃ are negatively correlated (R² = −0.60) (Table 3).

Trace elements are weakly concentrated in the studied samples. The High Field Strength Elements (HFSE), Hf, Zr, Th and U vary from 0.2 - 0.4 ppm, 7 - 37 ppm, 0.19 - 15.5 ppm and 0.09 - 0.72 ppm respectively (Table 2). The contents of Large Ion Lithophile Elements (LILE), Sr, Rb, and Ba vary from 1 to 27.3 ppm, 0.2 to 1.7 ppm and 1.6 to 131 ppm respectively. The studied iron ore are depleted in HFSE and LILE when compare to the upper continental crust after [28] .

Rare earth elements concentration in the iron ore from the Edea North area vary with ΣREE oscillating between 5.31 and 397.74 ppm (average of 80.41) (Table 2). The samples are enriched in Light Rare Earth Elements (LREE) compared to Heavy Rare Earth Elements (HREE) with LREE/HREE ratios between 10.35 and 55.61 (average of 24.37) (Figure 6). The samples show a negative Eu anomaly (Eu/Eu* between 0.54 and 0.97) except EDN19 and EDN17 that reveal a slightly positive Eu anomaly (Eu/Eu* values range from 1 to 1.83). Ce displays negative anomalies between 0.39 and 0.87. The majority of the samples showed a negative anomaly in La and none in Ce and one sample displayed a positive anomaly in Ce (Figure 7).

Petrographic examination of the studied samples shows the following mineral assemblage: Magnetite + Quartz + Pyroxene ± Biotite ± Martite ± Amphibole. This mineralogy is characteristic of iron formations that have undergone metamorphism in the granulite facies [29] . Quartz and magnetite-martite identified in the samples is consistent with the geochemistry that shows Fe₂O₃ contents from 40.4 wt% to 62.9 wt% and SiO₂ contents between 33.8 wt% and 51.2 wt%.

bdl = below detection limit

Two main facies have been identified in the Edea North iron occurrence including the banded facies showing discontinuous banding and the massive facies. Based on the physical appearance and the chemical composition of the studied rocks, the name quartzite rich magnetite-martite has been proposed for this iron formation.

The Precambrian iron formations have low Al₂O₃, TiO₂, P₂O₅, CaO and MgO contents relative to post-Precambrian deposits [30] [31] . On a Fe₂O₃ - CaO + MgO - SiO₂ [30] and Al₂O₃ - SiO₂ - Fe₂O₃ [31] ternary diagrams, studied materials indicates a Precambrian affinity (Figure 8).

In the studied iron formations, magnetite presents irregular and elongated minerals which can contain quartz inclusions of various shapes and sizes. In addition to this textural observation, magnetite is deformed and may derive from chemical precipitations thus indicating a primary crystallization of magnetite [32] . The second magnetite texture is in the form of blasts clustering, around pyroxenes. It suggests a secondary crystallization resulting from the probable transformation of pyroxenes. Finally, xenomorphic magnetite crystals isolated in the silicate phases, which suggest the precipitation of magnetite during the formation of this occurrence. On the other hand, the relationships between magnetite and martite suggest the transformation of the first into the second during supergene enrichment. Overall, the following mineral transformation is suggested here: pyroxene-magnetite-martite.

The participation of the detrital materials during the formation of iron mineralization has been highlighted in the literature. In the BIF, the contribution of detrital materials is generally indicated by the high concentrations of Al₂O₃, TiO₂ and High Field Strength Elements (HFSE) (Zr, Hf, Ta, Th ...) and also by the inter-elements correlations between HFSE and rare earth ratios [10] [33] . The geochemical data of the Edea North iron occurrence are summarized in Table 2. High SiO₂ and Fe₂O₃ contents indicate chemical precipitation. In addition, [34] estimates that a typical chemical sediment is enriched in Mn and Fe, but the addition of detrital or volcanic materials results in dilution and enrichment of Ti, Al and Zr. However, the iron occurrence of the Edea North reveal relatively average values of Ti, Al and Zr which might suggest a low contribution of detrital materials. The correlation coefficients between Al₂O₃ and HFSE, LILE and some

transition metals Zr (0.82), Hf (0.85), Rb (0.44), Sr (0.96), Cr (0.70) and V (0.99) could also indicate a contribution of clastic materials during the deposition of these formations. The Th/U ratios in these samples range from 1.27 to 6.28, except for EDN17 where it is higher (29.25). This observation suggests a strong or moderate contamination by phosphates.

Various methods have been used to establish the difference between hydrothermal, biogenic, detrital and seawater sources based on mineralogical, chemical and geochronological differences in the formation of iron deposits [6] [29] [30] [35] [36] . Among these methods, numerous discrimination diagrams have been proposed by several authors to highlight the influence of detrital components, hydrothermalism, biological components and seawater in their genesis [34] [37] [38] [39] . On the SiO₂ vs Al₂O₃ diagram [34] , the iron mineralization samples from the Edea North iron occurrence plot within the hydrothermal domain (Figure 9). In the Fe-Mn-Al ternary diagram [38] the hydrothermal in origin is confirmed (Figure 10). The studied samples plot in the same area as those from the Bikoula BIFs of the Ntem complex [36] . This observation could indicate that Si and Fe of the studied deposits derived directly from a hydrothermal source. Similarly, in the Fe/Ti vs Al/(Al + Fe + Mn) diagram [37] a high affinity of the samples from the studied site with the hydrothermal domain is highlighted (Figure 11). This suggests an important contribution (in the volume) of the components of hydrothermal origin during the deposition of studied formations. Samples plot close to the field of modern metalliferous sediments indicating that some of the source components of the studied iron occurrence may have derived from sediments rich in highly hydrothermalized metals.

The hydrothermal predominance is demonstrated particularly in the Y/P₂O₅ vs Zr/Cr discrimination diagram after [39] in which all samples have a low Zr/Cr and Y/P₂O₅ ratio (Figure 12). The vanadium content in the sediments is generally low when compared to the upper lithosphere [40] . The vanadium content varies between 5 and 69 ppm with an average of 20.5 ppm in the studied rocks

(Table 2). This content is similar to that of deposits in China [41] and higher than BIF from the Ntem complex with values comprise between 9 and 11 ppm [42] . The Clarke value of chromium in sediments is 110 ppm and in igneous rocks from 200 to 2000 ppm. The chromium contents in the studied materials is smaller (10 and 80 ppm; average of 30 ppm) than the Clarke value of Cr in the sediments. Barium, on the other hand, shows concentration values between 1.6 and 131 ppm with an average of 51.17 ppm; this is relatively low compared to that of rocks of igneous origin. This content is comparable to sedimentary magnetite quartzites in the Arcot district of India [40] ; thus a sedimentary origin can be inferred for the Edea North iron mineralization.

REE are commonly used by several authors to infer the environmental conditions for deposition and origins of iron ore formations [43] [44] [45] [46] . The REE content of the studied formation are relatively higher than REE content from iron formations in Cameroon (see [11] [36] ). Chondrite-normalized REE patterns exhibit slight negative anomalies in Eu suggesting a prevalence of an oxidizing depositional environment during the Archean period [47] . The influence of the heterogeneous imprint of the clastic materials in the deposition basin could explain the negative Eu anomalies presented by most of the samples from this occurrence [48] [36] . Positive Eu anomalies represented by Eu/Eu* with values between 1 and 1.83 demonstrates the contribution of deep-sea hydrothermal solutions [6] [49] [50] . Some of the samples show negative Ce anomalies (Figure 7). These negative anomalies suggest the influence of sea water into the system [51] .