The Dango zone corresponds to a zone with significant, massive and whitish silicification (Figure 2(a), Figure 2(b)) (SIM: silicification, intense and massive). The development of this SIM is synchronous with the deformation, on the basis that the tectonic fabric is permeated in the silicification.

The silica impregnation is recognized, which generates textures in flames or lenses. The red-orange hues are largely related to iron carbonates and fill the compatible working thickness with a shear play indicative of tectonic movement during the silicification and iron carbonate impregnation (Figure 2(c)). The quartz veins which intersect the silicification suggest a genetic link with the main mineralization zone (Figure 2(d), Figure 2(e)). The mineralization takes the form of total silicification, whitish with cubic pyrites (Figure 2(f), Figure 2(g)). It overlaps with an episode of SIM breccia expressed by fine cement hematitization (Figure 2(h)).

The Dondo-Mobi deposit has been known for its mineralization associated with hydrothermal alteration by the biotite and quartz veins. The metamorphosed volcano-sedimentary host is relatively homogeneous with a microgranular texture with andesitic compositions (Figure 3(a), Figure 3(c)). Here, the deformation is well defined and expressed by an alignment of metamorphic biotite. Locally, the silicification of the host is accentuated in the vicinity of the tourmaline-pyrite zones (Figure 3(b)) ant the hydrothermal alteration is manifested by the random distribution of biotites in the foliation, indicating low foreshortening deformation under high fluid pressure (Figure 3(d)).

The Ovala deposit has been characterized for its dominant clastic sedimentary rocks, highly developed muscovite schists, extensive silicification, and kyanite porphyroblasts. Here, Muscovite schist is the most dominant feature, but represents an epiphenomenon to mineralization. The muscovite is nested within each other, revealing no deformation (Figure 4(a)) and clearly intersecting pyrites (Figure 4(b)). The presence of kyanite porphyroblast indicates a superimposed metamorphism on bleached rocks. This is a typical feature of metamorphosed volcanogenic deposits into amphibolite facies (Figure 4(c)).

The studied cores in the Massima district expose a volcano-sedimentary sequence (Figure 5(a)) injected into mafic sills. These rocks are weakly deformed, except in the graphitic shales zones they present a very strong deformation (Figure 5(b)). These boreholes contain several gold zones closely related to disseminated pyrite in the silicified volcano-sedimentary zones (Figure 5(c)).

In this study area, the treated boreholes display gabbroic sequences with particle size varying from microgranular to granular. The invasion of the structural fabric seems to have a link with the grain size: the less grainy parts are the least affected by the deformation. Probably, it could be due to the metamorphic recrystallization.

It is a very thin facies composed of micaceous and sandy levels. These levels are composed of very fine crystals of quartz, intensely recrystallized and flattened according to the regional schistosity (Figure 6(a)). Some white micas also appear

in these levels.

The micaceous levels are dominated by sericite and muscovite. These micas are generally oriented according to the regional schistosity (Figure 6(b)). In the vicinity, the white micas are strongly folded and attest the presence of a late deformation phase. Also, there is a strong chloritization of the rock which is manifested by a development of chlorite instead of the white micas. Opaque minerals are very abundant in this facies, giving it a reddish appearance.

From a metallogenic point, this facies contains chalcopyrite in ranges (50 to 100 μm), disseminated (Figure 6(c)), some very fine grains of arsenopyrite (<50 μm) and very fine droplets (<5 μm) of silver (Figure 6(d)). We also note the presence of grains and granules of iron oxides (20 - 200 μm) strongly disseminated in the rock.

This facies have gathered mainly intense recrystallized quartz. The mineralogy observed indicates that the fragments of the studied rock would correspond to a quartzite. Nevertheless, some fragments with the same mineralogy but their particle size is coarser would correspond to quartz veins or faults that have been deformed in the same way as quartzite (Figure 7(a)). The rock cement is siliceous, more or less reddened (Figure 7(b), Figure 7(c)).

Indeed, it is strongly impregnated with iron oxides which has been invaded in

the fragments by the fractures and cracks that affect them. This facies are characterized by a strong impregnation of iron oxides in the form of micrometric to millimeter ranges covering the entire rock (Figure 7(d)).

This rock shows a microlithic porphyry texture (Figure 8(a), Figure 8(b)) whose mineralogy is formed by:

· Quartz in the form of crystals, recrystallized and forms the cryptocrystalline matrix of the rock.

· The Feldspar, which is more or less abundant in these facies, is corroded at the edge. Its peripheries are frequently confused with the quartzo-feldspar matrix. Its size varies from 200 to 500 μm. It is usually very altered with a characteristic dirty appearance (Figure 8(c)).

· The weathering minerals observed are quartz, chlorite and white micas.

· The Plagioclase is relatively abundant in these facies. It is in the form of crystals of variable size (a few microns to 1 mm). They often have polysynthetic twin, and sometimes are strongly altered in chlorite, calcite, and epidote.

· The amphibole, dark green to light in color, is either in the form of ranges, micrometric to millimeter dimension, with cross-sections and longitudinals of greater dimension, or in the form of clusters with several combined ranges (Figure 8(a), Figure 8(c)).

The cryptocrystalline matrix of the rock is represented by very chloritized quartz-feldspar nature. This chloritization, giving the rock a characteristic

greenish appearance, is interpreted by a massive development of chlorite, in isolated or massive flakes developing on biotites, amphibole and on the matrix. In addition, we still note the presence of the epidote in finely disseminated granules, sometimes grouped. Carbonates completely invade the matrix, attesting to a late carbonation (Figure 8(d)).

From a Metallography view, the pyrite is very abundant in this facies, in the form of isolated crystals (50 to 500 μm) automorphic to xenomorphs finely disseminated in the rock; or grouped into several individuals, sometimes forming masses exceeding 1 mm (Figure 8(e)). These pyrite masses, in combination with quartz and carbonates, fill the fractures affecting the rock. Chalcopyrite has also been observed in this facies. It is in the form of ranges of dimensions from 50 to 200 μm, associated with pyrite and quartz at fractures, affecting the rock. Locally, it appears either in the form of scattered beaches; or in very fine inclusions within pyrite (Figure 8(f)).

It is a deformed, recrystallized facies slightly oriented according to the direction of foliation. It is recognized by the following mineralogy: amphibole, biotite, chlorite, calcite and quartz. The Amphiboles are very common (Figure 9(a)), they are in the form of elongated crystals according to the direction of foliation. Some crystals have a Poikilitic texture. Chlorites exhibit a radio-fibrous form (Figure 9(b)) and biotites present in a fibrous aspect are also visible in the rock (Figure 9(b)).

In these facies, the Quartz, slightly present, are recrystallized forming triple points with rolling extinction and corroded by the matrix of the rock. However, Calcite is abundant and permeates the entire rock (Figure 9(c)). Under a metallographic microscope, this structure shows the presence of very fine iron hydroxide boundaries in the late cracks and fractures and very fine grains (<5 μm) of Gold and/or Silver have been also observed in quartz (Figure 9(d)).

The composition of the analyzed samples follows that of mafic rocks characterized by relatively low SiO₂ contents (43.35 wt% to 55.5 wt%). MgO content varies

from 3.82 wt% to 22.42 wt% and the Al₂O₃ content varies from 6.39 to 18.85 wt.%. The results also highlighted a high content of FeOt (7.17 wt% - 12.54 wt%) and CaO (3.64 wt% - 13.41 wt%), while the contents of MnO (0.13 wt% - 0.18 wt%), P₂O₅ (0.04 wt% - 0.11 wt%) and TiO₂ (0.41 wt% - 0.76 wt%) are considerably lower. The studied rocks show high contents of Sr (35 - 310.8 ppm), Zr (15.9 - 84.9 ppm), Ni (16.9 - 688.6 ppm), and Cr (29.9 - 1550 ppm). Based on the diagram of [29], the rock samples have predominantly basaltic and basaltic-andesite rock compositions (Figure 10).

On the Zr-MgO diagram, all the samples are discriminated to be ortho-amphibolite (Figure 11(a)). The studied rocks have a calc-alkaline affinity (Figure 11(b)) and they exhibited arc-basalt setting (Figure 11(c)). Trace element contents of the studied samples were also used to determine the possible tectonic setting of the rocks. The distribution of our samples on the triangular diagram of [30], shows that our amphibolites are predominantly grouped in the volcanic-arc basalts setting of the orogenic domain (Figure 11(d)).

The studied granitoid samples consist of SiO₂ (57.66 wt% - 69.51 wt%), 0.59 wt% - 4.08 wt% of K₂O, and significant concentrations of Al₂O₃ (15.77-19.18 wt.%), Na₂O (0.39 wt% - 5.29 wt%), FeOt (2.76 wt% - 7.8 wt%) and MgO (0.81 wt% - 2.82 wt%). As for the trace metal content, these rocks showed high levels of Sr (14 to 341.1 ppm), Rb (28.3 to 341.9 ppm) and Y (up to 26.6 ppm), leading to a low to moderate Sr/Y ratio (2.09 to 51.68 ppm). According to the geochemical classification diagram of (Middlemost, 1994), our granitoid classifies as diorite

and granodiorite when using the classification of Middlemost (Figure 12).

The granitoids samples, characterized by a diorite to granodiorite geochemical composition, are predominantly calc-alkaline and moderately to highly potassic rocks (Figure 13(a)). The nature of these rocks is also found to be metalliferous to peraluminous (Figure 13(b)). Furthermore, the projection of these rocks in the diagram of (Pearce et al., 1984) indicates that all the studied granitoid samples are classified in the volcanic arc granitoid (VAG) domain (Figure 13(c), Figure 13(d)). These geochemical characteristics indicate that the Etéké granitoids could be derived from the partial melting of hydrated basaltic crust in subduction zones and from garnet and/or amphibole residues [34] [35] [36] [37].