OJGOpen Journal of Geology2161-7570Scientific Research Publishing10.4236/ojg.2023.1311051OJG-129178ArticlesEarth&Environmental Sciences Copper Mineralization in the Lower Cambrian Cover of Jbel N’Zourk (Central Anti Atlas, Morocco): Tectonic-Mineralizations Relationships AchrafAit Yazza1*IsmailBouskri2MohamedRaji1FaouziyaHaissen1NouraZoraa1LGAGE, Faculty of Sciences Ben M’Sik, Hassan II University, Casablanca, MoroccoSOMIFER, Managem Group/Al Mada, Casablanca, Morocco2211202313111195121924, August 202319, November 2023 22, November 2023© Copyright 2014 by authors and Scientific Research Publishing Inc. 2014This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/

The Moroccan Anti-Atlas is a vast geological region composed of a Precambrian basement covered by a late-Neoproterozoic to Paleozoic sedimentary sequences. More than 200 copper occurrences are listed in these sequences. The copper mineralization of the Jbel N’Zourk (Central Anti-Atlas) is observed into the lower Limestones of the lower Cambrian (Adoudou formation), just above the volcanic formations of the Jbel Boho between Bou Azzer El Graara and Zenaga inliers. The region is by an E-W shortening resulting in an overlapping structure with vergence associated with folds. Generally, the mineralization is hosted along the principal fault of Jbel N’Zourk and sometimes in the anticlines hinges. The petrographic study showed that the mineralization can be observed in several aspects, either in the fractures and veins, in small karsts or rarely disseminated in calcite and dolomite minerals. These observations host new arguments who contribute to a later reconcentration of the copper mineralization of Jbel N’Zourk, trapped on faulted and folded structures attributed to Variscan deformation.

Central Anti-Atlas Lower Cambrian Cover Copper Mineralization Structural1. Introduction

Many copper occurrences are present in the Neoproterozoic-Cambrian cover, also known as the Adoudounian cover [1] (Figure 1). These indices are poorly documented and have generally been considered to be the result of syngenetic processes [2] [3] [4] . The great interest of mining groups in copper resources guides the need for the best constraint of the geological history of such mineralizations. The origin of these ores, which are hosted at different stratigraphic levels of the Adoudounian cover, remains in most cases poorly known even if few of them are currently being mined. Few of these copper orebodies are currently mined. Active mines include the Jbel Laassel mine whose reserves are estimated to be 7,500,000 t with 1% Cu, [5] the Agoujgal mine whose reserves are estimated to be 5,200,000 t with 1.11% Cu and 21 g/t Ag, [6] and the Ouanssimi mine whose reserves are estimated to 1,300,000 t with 2.65% Cu [5] . Other ore bodies are in exploration phase (Jbel N’Zourk, Tarmmant, Tizi N’Mekraz, Assif N’Zaid, Oued Rthem, Tizert…) [2] [5] [6] . The Jbel N’Zourk copper body is the largest copper deposit in the Adoudounian cover in Central Anti-Atlas. It is located at the southern flank of the Central Anti-Atlas between the Bou Azzer El Graara and Zenaga inliers (Figure 1). Exploration studies performed by Managem group since 2016, are presently estimating the resources at 1,250,000 t with 1.12% Cu [7] . The aims of the present work are to characterize the copper mineralizations in Jbel N’Zourk, the nature and structural analysis of their host rocks, and the relationships between the mineralized rocks and tectonics structures, Which will contribute to highlight the role of the deformation of the Adoudounian cover in the emplacement of copper mineralizations, based on structural, microstructural, and petro-graphic observations.

2. Regional Geological Setting2.1. The Anti-Atlas Belt

Located along the northern border of the WAC (West African Craton) [10] , it is limited by the alpine chain of the High Atlas to the North, by the Tindouf basin to the South, by the Atlantic Ocean to the West and by the Tafilalet and Bechar basins in the East. It is a large Atlasic bulge oriented ENE-WSW, superposed on a Hercynian fold whose anticlinal core reveals the Proterozoic crystalline basement through “inliers” [Bas Dràa, Ifni, Kerdous, Tagragra of Akka, Igherm, Tata, Izazen, Iguerda, Ouzellarh, Sirwa, Zenaga, Bou Azzer el Grara, Saghro and Ougnat] (Figure 1), distributed along two major fault zones (South Atlas Fault, and Central Anti-Atlas Fault). This belt has recorded Eburnean, Pan-African and Hercynian orogenesis, which are related to the Paleoproterozoic, Neoproterozoic and Paleozoic respectively. The Precambrian basement is formed by diversified sedimentary and metamorphic complexes, often intruded by granitic complexes dated at 2050 ± 10 MA [11] , and more rarely, by basic and ultrabasic intrusive rocks while the Pan-African belt shows ophiolitic complexes are preserved along the Anti-Atlas Major Fault (AAMF) in the Bou Azzer and Siroua inliers [12] - [21] . All these formations are also associated with many acid and basic volcanic rock bodies of variable nature and size. The rest of the Anti-Atlas region is generally covered by Paleozoic terrain rarely deformed [15] [16] [22] [23]

[24] [25] [26] . The latter is largely developed on the southern flank of the Anti-Atlasic anticlinal [23] [27] .

2.2. The Adoudou Formation

Its name is related to the Adoudou Oued located to the west of the Anti-Atlas [24] . This for-mation crops out largely in the Anti-Atlas belt and southwest of the High Atlas with a 1000 m thick series and represents the oldest volcano-clastic complex unconformably covering the Neoproterozoic Ouarzazate group [28] [29] . The Adoudou Formation is associated with a major marine transgression from the West to the Est. It has been subdivided into two groups: the Taroudant Group, with Lower Dolostones and Lower Sandstones units, and the Tata Group, with Upper Dolostones and Upper Sandstones units [23] [30] [31] [32] [33] . The Adoudounian series shows significant variations in facies and thickness. Moving eastward (Saghro, Ougnat, etc.), these series become thinner and dominated by increasingly coarser terrigenous facies, as opposed to the carbonate facies deposited to the west (Tiznit region) [27] [23] . A calico-alkaline volcanism is initiated during the same period as the sedimentation of the Adoudou formation. Two volcanic complexes, Jbel Boho and El Gloa, are located in the Central Anti-Atlas [22] [34] [35] . Old lava flows belonging to the Jbel Boho volcanic system, interspersed in the Adoudou formation, have been dated at 534 ± 10 MA (U/Pb Shrimp on Zircon) [35] and at 531 ± 5 MA [35] .

3. Local Geological Setting

The Jbel N’Zourk deposit is hosted in the Lower Cambrian part of the late Ediacaran to Cambrian volcano-sedimentary formations at the southern flank of the Central Anti-Atlas between the Zenaga and Bou Azzer El Graara inliers, 50 km NW of the Bleida mine. Geological mapping, fieldwork and lithological description of drill cores have allowed us to construct the lithostratigraphic column of the Jbel N’Zourk region (Figure 2 & Figure 3), which consists of a thick succession (approximately 800 m) of the Adoudounian cover. We distinguish from bottom to top:

• The basal series: represented in the studied region by a breccia and conglomeratic unit with a thickness of 5 to 100 meters, composed of subangular elements which origin is the underlying volcano-sedimentary series. Horizontal rough bedding appears locally in these facies, indicating a high energy deposition process in a fan-delta system.

• The lower limestone: with a 150 - 250 m thickness series composed of a succession of dolomitic limestones levels separated by red and white clays siltstones showing some local breccia recurrences. The dolomitic levels, when they are not massive, are frequently characterized by the presence of horizontal laminates of microbial origin and more rarely by stromatolitic domed structures. Intense secondary silicifications affect the dolomites in Jbel N’Zourk.

• The Jbel Boho volcanic complex: with levels of pyroclastic tuffs, lava and volcanic breccias interspersing at the base of the lower limestones in Jbel N’Zourk. These volcanic manifestations are mainly found in the river area (Mechkerj River). This volcano-sedimentary series with a thickness varying from 100 to 200 m indicates a synsedimentary volcanic system, which was to constitute an emerging relief, with dismantling products transported in the form of debris flows interbedded within the platform deposits of the Adoudounian formation.

• The “Lie de Vin” Series: are lower sandstones that are part of the Tikirt Formation (150 to 200 m thick) which is composed essentially by a red claystones of sand-stones frequently interlayered by centimetric clayed siltstones and purple argillites representing a significant sea level regression.

The vertical change in facies from the lower limestone to the “Lie de Vin” series is rapid and progressive; on the other hand, this series is brutally surmounted, without any visible discordance, by the upper limestones, which initiates a new negative sedimentary sequence.

4. Sampling and Analytical Methods

In order to establish a detailed survey of the Jbel N’Zourk copper mineralized veins and to understand their distribution and tectonic control, a structural and microstructural study has been performed in the prospect area. Samples were collected from outcrops and drill cores were used for petrographical, mineralogical, and geochemical studies. Polished thin sections were prepared from these samples and have been first studied using a petrographic microscope with transmitted and reflected light modes. Complementary observations and mineral’s analyses were carried out using JSM IT100 (JEOL) Scanning Electron Microscope (SEM) with 0.5 to 30 kV accelerating voltage. The SEM system is coupled to Energy-Dispersive X-ray fluorescence (XRF) spectrometer (EDS) to make qualitative compositions of sulphide minerals from ten polished sections. Whole-rock geochemical data of samples collected at different prospect area were determined at the Reminex Research Center (MANAGEM Group). For the major elements analysis (SiO2, Al2O3, Fe2O3, CaO, MgO, MnO, K2O, TiO2, P2O5), 0.5 g of the sample is crushed at less than 100 μm and it is dissolved by fusion at 500˚C during 40 min with 2.5 g of sodium peroxide in a zirconium crucible. The melt mixing is then dissolved with 100 mL of hydrochloric acid (28% HCl) and the solution is analyzed using an ICP-AES ULTIMA 2C using the Jobin Yvon-HORIBA device. For the other elements (Cu, CuOx, As, B, Ba, Be, Bi, Cd, Co, Cr, Ge, Li, Mo, Nb, Ni, Pb, Sb, Se, Sn, Sr, W, Y, Zn, Ag), 0.25 g of the sample is dissolved by microwave-assisted acid attack (50% HCl and 50% HNO3) during 40 min at 220˚C. The solution is then analyzed by ICP-MS Thermo X’Serie 2.

5. Results5.1. Structural Study

The Jbel N’Zourk area is located in a large anticlinal structure. This structure only affects the higher terms compared to the basic silty sandstone and ferruginous micro-conglomerates. The whole sequence in Jbel N’Zourk undergoes at least two deformation stages. Two types of folds are present. The first family corresponds to very tight folds characterized by axial planes poured eastward or kneeling folds, with an N-S orientation. Fracture schistosity, absorbed essentially by the levels of siltstones between dolomitic limestones, is associated with these folds. The second fold family characterized by very open is opaque folds oriented NE-SW; of pluri-metric to plurikilometric amplitude spatially associated with overlaps of the same direction, and are distributed mainly in the western flank of Jbel N’Zourk. Sometimes we can observe in the same folding axis the passage from tight folds to kneeling folds. This disharmony is due to the effect of discontinuity and variability in the power of the siltite levels between the limestones. These silty horizons played a soapy role when the limestone bars were folded. Some of these folds are therefore interpreted as fault propagation folds that have formed at the tip of blind thrust and back thrust that terminate upward from a flat decollement localized along the upper boundary of the Jbel Boho formation.

One decametric extension thrust fault can be observed at the top of the Jbel N’Zourk relief, where the unit of the lower dolomitic limestones in underlying the unit of siltstones and sandstones of the series of “Lie de Vin”, along a NNW-SSE trending thrust dipping 80˚ to the east (Figure 4 and Figure 5).

The western flank of Jbel N’Zourk is the most deformed part; the survey of the fracturing made it possible to distinguish two families of faults, a NNW-SSE orientation family that generally ranges from N150˚ and N180˚, parallel to the major Jbel N’Zourk fault, and a second E-W family characterized by an orientation between 45˚ and N 70˚ (Figure 6).

In addition to the large structures of Jbel N’Zourk, microstructures have been identified within the mineralization, which essentially corresponds to veins, veinlets, microfails, tension slots and veins (Figure 7).

These microstructures sometimes show indications that provide information on the movement and cinematic properties of the tectonic deformations that have affected the region. Jbel N’Zourk is a region characterized by intense fracturing that sometimes makes the entire structure difficult to identify due to large scree overlaps (Figure 7).

5.2. Copper Mineralization5.2.1. Geometries and Orientation

In the Jbel N’Zourk copper deposit, the economic mineralized zone is present in the western part of the Jbel N’Zourk fault in a thick series of carbonates of the Adoudou formation. The sulphides are mainly hosted in the base of the lower carbonate formation in veins and sometimes in the base siltstones of the series. The lateral and vertical extent of ore bodies was delimited by cartography and drilling studies. The thickness of the mineralized zone reaches 40 m. Locally,

later copper sulphide minerals are distributed in both families of the faults NNW-SSE and E-W in the Adoudou formation. In this formation, sulphides occurrence are essentially observed in fractures, in quartz veins and in quartz and calcite geodes. The eastern boundary of ore bodies present the Jbel N’Zourk fault zone, the southern and western boundaries of the deposit are not explored and are not yet fully defined, but ongoing drilling exploration activities aim to define the boundaries of the economic mineralized zones in this deposit.

5.2.2. Associated Mineralogy and Paragenetic Succession

Without distinction between primary and secondary origin, the copper mineralization in Jbel N’Zourk deposit is composed of bornite, calcocite, chalcopyrite, covellite, pyrite, digenite, malachite, azurite, cuprite, tenorite and chrysocolla, associated with quartz, dolomite and calcite as gangue mineral. This mineral gangue in the veinlets or voids systematically has a banding texture. When these three phases are present, it forms ribbons within the veins with quartz on the epontes, then dolomite and finally calcite in the center. This gangue chronology is a great reference point for determining the succession of copper minerals in this deposit. Bornite is the most abundant and developed copper sulphide in the deposit as evidenced by petrographic observations (Figures 8(A)-(C) ), being partially or totally replaced by chalcocite. Chalcopyrite often appears as a corona around the bornite and rarely included in the bornite (Figure 8(A), Figure 8(C)). This association can be explained by exsolution between the two phases or by the replacement of the bornite by chalcopyrite. Chalcopyrite and bornite are transformed into dark blue colored covellite, digenite and chalcocite (Figure 8(A), Figure 8(B)). These secondary alteration minerals are observed mainly in the rims of the bornite and chalcopyrite minerals. However some Cristals can be totally replaced by late chalcocite, digenite and covellite. The mineral phases of copper carbonates are generally associated with the supergenic alteration of primary sulphides and are composed of malachite, azurite and chrysocolla (Figures 8(D)-(F)). These copper carbonates are present as secant veinlets on all structures replacing sulphides and dolomites. All these relationships between minerals allow the distinction of a primary paragesesis represented by: quartz, bornite, chalcopyrite, dolomite and calcite, and a secondary one represented by: covellite, chalcocite, digenite, malachite, azurite, chrysocolla, tenorite and cuprite. Based on the intersection relationships between the different mineral phases, several episodes of fracturing have been observed (Figure 8; Table 1).

5.2.3. Multiscale Observations of the Ore Texture

In the field and at macroscopic scale, two types of textural mineralization have been identified; the most frequent texture of mineralization in ore deposit is a stockwork with veins, fractures and veinlets are oblique to the stratification. The veins of this stockwork have locally combed quartz textures. The second type of texture corresponds to disseminations within the rock groundmass in the basic siltstones. Locally it is spatially related with the stockwork texture. At the microscopic scale by observation of polished thin sections, both types of mineralization appear composed by the same ore and gangue minerals. Textural, chronological relationships and paragenetic sequence has being also similar (Figure 8).

Paragenetic succession of the Jbel N’Zourk deposit
MineralsPrimary assemblageSecondary assemblage
Quartz (SiO2)
Dolomite (CaMg(CO3)2)
Calcite (CaCo3)
Chaclopyrite (CuFeS2)
Bornite (Cu5FeS4)
Chalcocite (Cu2S)
Digenite (Cu9S5)
Covellite (CuS)
Malachite ((Cu2)2CO3(OH)2)
Azurite (Cu3(CO3)2(OH)2)
Natif copper (Cu)
Chrysocolla (Cu,Al)2H2SiO5(OH)4
Fissuring
5.2.4. Principal Component Analysis (PCA) of Chemical Data

The database of the JBEL N’ZOURK prospect is composed of 97 samples that correspond to the sampling by lithology of the copper mineralized zone (Table 2 and Table 3). This database contains analyses of Total copper (Cu) (Figure 9). The results of the PCA show that two factors F1 and F2 explain 60.07% of the total variability (Figure 10(A)). Three groups of elements discriminated in the F1 - F2 plane (Figure 10(C)) corresponding in the observation plan to siltstones, dolostones and potentially to tectonic breccias for the group represented by the rare elements (Figure 10(D)). The copper variable, not well represented in the F1 - F2 plane, would be considered to have an affinity for the siltstone group (Figure 10(D)). This representation of the variables suggests that copper is not related to any of the three types of lithology. Indeed, copper is independent of sedimentary siltstones and dolostones, and it is anticorrelated with the lavas formation. The factors F2 and F5 are the most correlated with the copper variable (Figures 10(D)-(F) ). Moreover, an examination of the F2 - F5 plane, suggests that copper could be associated with titanium, with correlation coefficient between total copper and titanium is 0.62 (Figure 10(E), Figure 10(F)). In a binary representation, the coefficient of determination, between these two elements, is 0.4 which shows that the correlation between these two elements is limited (Figure 9). Therefore, the PCA highlights the independence of copper (total and oxidized) relative to the others variables present in the available database, especially that corresponding to lithology (Figure 10).

Whole rock major element chemical data of the studied samples from the Jbel N’Zourk deposit
SampleRock typeSiO2Al2O3Fe2O3CaOMgOK2OMnOTiO2P2O5Na2O
JNZ 01Siltstone51.9212.862.439.153.854.550.160.550.130.43
JNZ 02Dolostone13.284.092.3424.614.921.930.560.140.050.32
JNZ 03Dolostone64.849.432.656.342.544.140.160.450.150.36
JNZ 04Siltstone57.9312.523.256.343.064.940.140.540.150.37
JNZ 05Dolostone16.944.432.5824.2513.531.850.470.160.080.22
JNZ 06Dolostone65.3510.062.555.752.464.180.130.460.170.34
JNZ 07Siltstone63.0510.983.163.694.774.460.150.470.140.47
JNZ 08Dolostone11.133.062.7625.9315.741.450.520.150.050.22
JNZ 09Siltstone41.938.422.8514.447.222.860.240.340.120.53
JNZ 10Dolostone12.932.732.3426.6315.280.570.450.150.040.54
JNZ 11Dolostone77.446.841.064.420.942.640.160.150.060.14
JNZ 12Breccia36.348.241.5525.431.431.930.170.340.110.48
JNZ 13Dolostone8.951.451.4828.0317.040.080.330.060.030.56
JNZ 14Dolostone15.953.161.5524.4415.030.540.240.150.040.62
JNZ 15Dolostone30.436.961.4618.0310.042.850.140.680.070.16
JNZ 16Siltstone13.831.483.2335.447.730.660.230.090.130.14
JNZ 17Dolostone7.680.921.8427.3418.050.360.240.060.030.15
JNZ 18Dolostone29.663.931.6427.3812.961.560.240.170.030.13
JNZ 19Dolostone15.931.342.3527.7413.540.460.350.070.050.18
JNZ 20Siltstone19.245.241.9331.256.761.860.260.270.130.24
JNZ 21Siltstone53.8512.271.729.363.534.060.180.740.180.16
JNZ 22Dolostone14.844.142.5325.4713.631.690.470.180.080.14
JNZ 23Breccia23.344.052.3427.658.661.380.370.240.120.15
JNZ 24Dolostone25.324.761.7522.9616.561.930.480.220.120.17
JNZ 25Dolostone6.731.811.8623.2213.780.630.630.080.050.17
JNZ 26Dolostone11.043.171.9627.3414.431.070.460.150.070.19
JNZ 27Dolostone64.937.711.4610.151.343.120.150.270.160.18
JNZ 28Siltstone13.242.22.4625.6615.960.830.430.070.080.17
JNZ 29Dolostone7.861.483.0527.3516.550.640.630.080.070.17
JNZ 30Dolostone19.185.072.5522.1613.771.760.440.260.120.13
JNZ 31Siltstone31.645.951.6527.853.521.650.230.270.130.22
JNZ 32Dolostone15.942.962.0626.513.631.350.430.160.070.13
JNZ 33Siltstone52.1212.251.978.85.444.850.120.630.180.16
JNZ 34Dolostone24.530.551.9821.7614.870.260.330.040.020.43
JNZ 35Siltstone53.1416.141.584.52.756.940.060.850.140.75
JNZ 36Dolostone1.660.282.9730.0618.120.170.450.030.030.37
JNZ 37Siltstone50.6618.941.573.32.98.660.561.460.180.94
JNZ 38Dolostone17.962.931.6823.415.530.840.260.230.090.28
JNZ 39Dolostone9.261.141.9925.4618.450.550.350.060.030.52
JNZ 40Siltstone39.0511.442.0812.137.334.360.160.650.080.52
JNZ 41Dolostone8.251.041.5926.2418.840.560.650.040.040.32
JNZ 42Breccia34.349.954.4622.061.844.670.120.480.120.32
JNZ 43Siltstone79.237.241.032.840.844.130.040.140.120.44
JNZ 44Siltstone65.448.412.688.041.253.730.150.460.130.42
JNZ 45Siltstone30.267.661.2429.951.431.650.140.350.130.68
JNZ 46Breccia11.443.341.0744.151.070.560.140.140.070.65
JNZ 47Dolostone14.250.861.7327.2315.160.070.250.030.040.56
JNZ 48Dolostone12.341.431.5827.3316.140.280.250.070.030.54
JNZ 49Dolostone14.241.811.5825.0416.050.380.170.070.050.64
JNZ 50Dolostone10.361.281.7727.2317.160.160.160.060.030.43
JNZ 51Dolostone21.130.321.4426.0413.570.050.140.030.040.42
JNZ 52Siltstone78.747.331.063.950.882.140.130.140.070.17
JNZ 53Siltstone46.656.971.3322.340.651.370.160.240.070.24
JNZ 54Siltstone54.0711.561.387.333.761.960.240.470.060.34
JNZ 55Dolostone10.250.791.4526.3417.280.020.440.020.030.49
JNZ 56Breccia28.156.771.5528.43.791.220.160.260.060.56
JNZ 57Dolostone13.922.791.8425.7513.760.220.270.130.020.36
JNZ 58Dolostone3.840.482.732418.570.110.350.030.020.65
JNZ 59Dolostone4.340.271.3528.9519.640.010.250.030.020.48
JNZ 60Dolostone131.621.8825.3617.760.820.170.120.020.66
JNZ 61Dolostone10.731.351.6725.8617.660.730.170.080.030.38
JNZ 62Dolostone14.144.042.4925.1713.761.930.370.180.020.46
JNZ 63Dolostone18.332.221.4125.7715.880.470.180.120.090.69
JNZ 64Dolostone9.511.242.7726.8816.780.540.40.080.060.23
JNZ 65Siltstone23.266.481.7529.676.132.050.140.420.140.17
JNZ 66Dolostone16.532.711.8727.5516.341.060.130.120.060.21
JNZ 67Dolostone14.132.562.2224.4216.050.850.140.130.061.42
JNZ 68Dolostone17.123.662.3527.4611.161.660.250.220.130.42
JNZ 69Dolostone21.464.242.6527.528.862.070.260.250.120.365
JNZ 70Dolostone35.188.742.1417.357.473.830.240.620.140.13
JNZ 71Dolostone11.621.551.5526.5116.760.650.250.080.060.12
JNZ 72Siltstone39.5311.372.3514.166.544.250.170.750.180.23
JNZ 73Dolostone13.932.241.7626.3515.350.840.250.120.060.27
JNZ 74Siltstone55.748.451.0612.113.053.750.080.420.150.04
JNZ 75Siltstone51.6515.531.556.122.186.060.081.550.30.03
JNZ 76Dolostone11.6221.6427.3215.760.770.170.130.060.16
JNZ 77Siltstone36.059.361.7219.725.052.850.270.510.170.14
JNZ 78Siltstone28.568.051.6528.782.763.260.080.480.170.07
JNZ 79Siltstone48.713.92.048.984.545.450.080.850.180.02
JNZ 80Dolostone29.138.942.9525.573.043.380.160.560.191.24
JNZ 81Siltstone12.442.162.4327.9513.450.950.250.130.080.74
JNZ 82Siltstone39.5810.331.1714.248.344.450.151.070.120.22
JNZ 83Dolostone11.132.823.0726.5514.971.350.370.150.020.44
JNZ 84Dolostone10.631.552.2527.0616.080.840.30.060.020.33
JNZ 85Dolostone66.157.472.157.671.424.040.120.260.050.12
JNZ 86Siltstone16.235.032.6523.0813.832.330.380.230.060.47
JNZ 87Dolostone9.142.262.262716.421.340.80.070.050.18
JNZ 88Dolostone12.061.772.2525.515.831.030.370.060.050.52
JNZ 89Siltstone58.0817.751.972.262.265.870.070.780.040.15
JNZ 90Siltstone13.953.561.7624.7315.131.840.260.150.030.66
JNZ 91Dolostone14.362.871.9724.1315.641.940.60.130.040.55
JNZ 92Dolostone7.460.972.8328.5116.440.740.370.050.050.13
JNZ 93Dolostone17.934.580.8438.121.631.930.080.250.060.44
JNZ 94Dolostone7.450.982.1526.8118.040.730.320.050.040.55
JNZ 95Dolostone33.458.481.9322.593.843.140.080.370.070.33
JNZ 96Siltstone15.461.781.8424.1315.530.650.140.080.050.45
JNZ 97Dolostone11.320.271.8525.3317.530.340.280.030.040.34
 Whole rock trace element chemical data of the studied samples from the Jbel N’Zourk deposit
SampleRock typeBaCrCuPbSrZnGeZrYLaCePr
JNZ 01Siltstone2272897963556119012613.330.6336.125
JNZ 02Dolostone1588122425966357611.8510.9624.572.56
JNZ 03Dolostone2072226247441483868.839.8325.142.55
JNZ 04Siltstone22425583434611211412410.3413.7230.363.36
JNZ 05Dolostone1367498437712405512.549.0619.792.16
JNZ 06Dolostone25321944148139611310.4311.0925.592.96
JNZ 07Siltstone202231812306312721028.128.9521.552.48
JNZ 08Dolostone9689831915345721.9515.2334.123.64
JNZ 09Siltstone1671668660641336526214.8815.5738.033.76
JNZ 10Dolostone2172178561322716720812.9410.7425.832.68
JNZ 11Dolostone54838177725391602127.838.1217.152.28
JNZ 12Breccia58641934692081012337314.3317.1633.363.74
JNZ 13Dolostone7921810323420510748310.646.84103.41.78
JNZ 14Dolostone1212210,61766137137819310.527.9317.682.13
JNZ 15Dolostone216374351441983312410.048.9218.872.27
JNZ 16Siltstone3752717533716678151669.049.4727.332.44
JNZ 17Dolostone74242966359745871225.566.6514.641.62
JNZ 18Dolostone1743133410544561856.947.7616.451.98
JNZ 19Dolostone4942527723112533671967.235.5812.641.56
JNZ 20Siltstone436351565371753533638.249.2332.362.24
JNZ 21Siltstone3815533185365418610.5412.1426.383.14
JNZ 22Dolostone3873225842713428346711.1510.6522.392.56
JNZ 23Breccia4453211862720325321549.748.3616.971.98
JNZ 24Dolostone2943219635131243716814.7611.4225.562.74
JNZ 25Dolostone14224853011738792239.847.5316.281.74
JNZ 26Dolostone17428963111331375520.0417.1241.764.48
JNZ 27Dolostone287377243544857866.336.5415.751.93
JNZ 28Siltstone10427643510338407811.359.2321.562.28
JNZ 29Dolostone1232582281144642679.986.6314.691.63
JNZ 30Dolostone363311024213534438613.8510.1328.542.56
JNZ 31Siltstone13233646281212635879.1710.1520.562.33
JNZ 32Dolostone394261937351074422647.446.2814.551.73
JNZ 33Siltstone3235452682335716712.8412.0326.743.25
JNZ 34Dolostone7412326427841450574.353.739.291.09
JNZ 35Siltstone3174445,385511432511717810.6316.3529.143.64
JNZ 36Dolostone145614732596239296.843.348.491.13
JNZ 37Siltstone3734736,282419623922563.374.1411.051.34
JNZ 38Dolostone360213229272239445811.288.4427.662.16
JNZ 39Dolostone1246132525911443629.947.4817.182.08
JNZ 40Siltstone2143234,75334131188911312.6516.7433.653.82
JNZ 41Dolostone14469432710612333313.267.4519.962.38
JNZ 42Breccia24417524654127817225.3821.2446.565.57
JNZ 43Siltstone265266327325219844.143.367.761.08
JNZ 44Siltstone342265173851131209513.6512.3531.853.76
JNZ 45Siltstone33138172748123127615912.3616.4231.983.73
JNZ 46Breccia23023162430113111023397.379.0619.032.14
JNZ 47Dolostone132156864410612852126.754.9711.531.45
JNZ 48Dolostone53161273312413731266.245.8413.131.56
JNZ 49Dolostone5613103301451251374.244.429.531.25
JNZ 50Dolostone711164341231656396.756.4314.421.68
JNZ 51Dolostone57135825722578495.664.9313.651.47
JNZ 52Siltstone7783112447781798833.974.6511.941.68
JNZ 53Siltstone94434625631641536677.8411.4623.862.57
JNZ 54Siltstone11636048,4589026443288811.1612.6834.273.82
JNZ 55Dolostone560112220237263142236.454.4710.011.26
JNZ 56Breccia47733721656262153810514.521527.053.25
JNZ 57Dolostone423239401311332526469.046.0413.621.74
JNZ 58Dolostone628613825144127336.173.468.981.17
JNZ 59Dolostone426932341651135586.274.0711.71.25
JNZ 60Dolostone76835633942118515.965.0813.471.47
JNZ 61Dolostone763765438771219626.463.999.721.18
JNZ 62Dolostone1933445265012419421468.878.6918.492.06
JNZ 63Dolostone7698440981930575.025.1211.251.37
JNZ 64Dolostone1163541532127491.261.233.180.36
JNZ 65Siltstone1962451511962338581.242.144.460.55
JNZ 66Dolostone541133431221634722.022.245.160.54
JNZ 67Dolostone52722401231525324.424.3244.151.13
JNZ 68Dolostone27314946471452337938.478.0816.782.15
JNZ 69Dolostone30515118245138265467.848.6618.362.24
JNZ 70Dolostone3233211,05567141303510713.6614.3328.453.43
JNZ 71Dolostone5772052291011721596.87.3816.631.96
JNZ 72Siltstone5974116,39561138354313413.5115.5932.484.04
JNZ 73Dolostone2068774834144232415.557.0614.881.83
JNZ 74Siltstone19285185621852412758.7310.1820.232.55
JNZ 75Siltstone27494244,70867176374516314.5413.5326.523.34
JNZ 76Dolostone4738419637108312643.76.0412.431.55
JNZ 77Siltstone3433213,5685619322407713.3415.7539.863.98
JNZ 78Siltstone2743123155618913127810.5513.0926.333.17
JNZ 79Siltstone3185520,9414310725138214.0514.7631.353.99
JNZ 80Dolostone277312197871472728612.613.4327.423.28
JNZ 81Siltstone1888131445177162537.767.6416.492.05
JNZ 82Siltstone268457531241875620314.0512.1125.283.02
JNZ 83Dolostone148173195471151830679.147.6648.951.73
JNZ 84Dolostone2241798461231618829.235.6513.641.41
JNZ 85Dolostone48767967740832317765.946.5813.251.52
JNZ 86Siltstone324568934042192142578.859.821.862.41
JNZ 87Dolostone462965145944172123626710.647.6916.981.84
JNZ 88Dolostone15817486873014517562447.945.9813.531.62
JNZ 89Siltstone3415657,888276636572061.250.742.670.32
JNZ 90Siltstone1862252233513812481026.768.3519.092.04
JNZ 91Dolostone15611373333213513492137.046.4713.331.63
JNZ 92Dolostone78252320714113414301558.335.2411.661.38
JNZ 93Dolostone293100783271231024945.837.1336.851.66
JNZ 94Dolostone561823153914514161056.034.069.341.16
JNZ 95Dolostone2774610,904491522411979.3311.8723.632.86
JNZ 96Siltstone74302842511210542676.244.7410.931.37
JNZ 97Dolostone3330914311141113425.343.498.921.17
SampleRock typeNdSmEuGdTbDyHoErTmYbLuTh
JNZ 01Siltstone15.763.120.683.060.422.450.481.520.231.530.234.78
JNZ 02Dolostone10.442.2830.622.720.372.0080.350.950.110.720.11.08
JNZ 03Dolostone10.152.050.492.070.281.640.320.980.130.930.132.87
JNZ 04Siltstone13.262.5820.582.470.331.920.381.190.161.170.173.85
JNZ 05Dolostone8.842.130.582.540.372.130.381.040.140.810.121.23
JNZ 06Dolostone11.942.440.592.390.3320.431.230.171.180.173.46
JNZ 07Siltstone10.042.080.4940.261.670.351.040.150.910.162.44
JNZ 08Dolostone14.833.480.994.20.633.580.631.650.191.1820.161.34
JNZ 09Siltstone14.772.980.6650.442.520.481.470.221.330.233.77
JNZ 10Dolostone10.522.380.642.630.432.320.451.170.160.940.141.54
JNZ 11Dolostone8.881.810.521.680.211.340.290.880.120.940.152.34
JNZ 12Breccia13.942.730.722.830.412.540.531.670.231.630.234.37
JNZ 13Dolostone7.331.950.662.650.361.950.350.980.140.760.121.16
JNZ 14Dolostone8.512.120.532.260.361.960.361.030.130.880.111.73
JNZ 15Dolostone9.321.920.562.130.341.860.371.330.171.070.161.76
JNZ 16Siltstone9.652.120.562.180.331.750.320.860.130.870.141.54
JNZ 17Dolostone6.421.330.351.280.120.940.160.480.080.470.080.73
JNZ 18Dolostone7.921.640.441.730.251.310.240.680.080.660.081.74
JNZ 19Dolostone6.431.580.531.760.261.420.250.670.080.580.080.73
JNZ 20Siltstone8.731.850.512.120.291.540.290.840.130.820.121.95
JNZ 21Siltstone12.322.460.622.50.352.080.431.340.231.470.224.15
JNZ 22Dolostone10.382.350.6312.770.382.090.350.980.120.890.121.82
JNZ 23Breccia7.961.8760.562.240.311.810.310.930.120.860.111.78
JNZ 24Dolostone11.182.570.62.780.422.510.471.320.161.140.151.77
JNZ 25Dolostone7.191.660.451.890.281.730.310.870.130.760.120.88
JNZ 26Dolostone18.423.9231.044.230.453.350.611.730.221.440.22.71
JNZ 27Dolostone7.821.550.331.470.211.160.220.690.090.680.091.68
JNZ 28Siltstone9.382.1330.542.40.262.0030.340.920.110.70.090.53
JNZ 29Dolostone6.841.750.442.050.311.830.330.840.120.710.090.56
JNZ 30Dolostone10.542.430.652.840.42.340.441.230.151.020.131.74
JNZ 31Siltstone9.271.950.762.130.211.650.320.860.130.820.121.85
JNZ 32Dolostone7.051.660.551.860.261.460.250.70.090.630.081.07
JNZ 33Siltstone13.042.640.532.470.362.220.471.520.241.620.243.72
JNZ 34Dolostone4.481.040.331.220.170.720.160.380.070.310.040.44
JNZ 35Siltstone13.792.460.552.430.341.980.441.460.231.580.255.93
JNZ 36Dolostone5.911.440.41.740.271.430.250.580.080.460.070.17
JNZ 37Siltstone5.061.040.330.980.150.910.230.750.130.920.151.95
JNZ 38Dolostone8.972.231.562.850.372.070.361.060.150.910.161.47
JNZ 39Dolostone8.822.250.612.490.361.980.360.960.130.780.120.66
JNZ 40Siltstone14.732.870.612.880.382.290.461.450.221.440.225.12
JNZ 41Dolostone10.352.680.793.140.462.420.431.140.140.840.130.71
JNZ 42Breccia22.534.551.0574.690.684.20.872.770.392.690.394.43
JNZ 43Siltstone4.030.870.290.920.140.930.20.560.090.570.071.21
JNZ 44Siltstone14.853.050.733.060.42.570.531.570.251.530.254.22
JNZ 45Siltstone13.792.620.522.570.362.090.441.370.221.330.214.81
JNZ 46Breccia8.111.630.441.670.251.360.290.870.110.850.121.77
JNZ 47Dolostone5.831.380.351.460.231.190.230.640.040.530.090.74
JNZ 48Dolostone6.141.370.361.420.211.090.230.570.060.450.041.02
JNZ 49Dolostone4.931.130.221.140.170.780.130.380.040.310.060.46
JNZ 50Dolostone6.711.550.421.760.271.260.240.580.080.410.070.74
JNZ 51Dolostone5.941.320.351.440.160.950.160.480.070.320.050.28
JNZ 52Siltstone6.661.440.441.230.140.940.180.630.080.630.11.21
JNZ 53Siltstone9.681.590.561.890.251.420.290.870.120.850.162.83
JNZ 54Siltstone13.872.710.782.680.392.040.441.240.161.170.154.52
JNZ 55Dolostone5.241.331.791.820.241.180.230.530.070.430.070.52
JNZ 56Breccia12.572.581.933.170.462.570.551.570.231.470.263.27
JNZ 57Dolostone6.971.550.492.020.341.630.340.820.110.660.081.33
JNZ 58Dolostone5.031.330.351.460.21.120.220.530.070.360.060.33
JNZ 59Dolostone5.351.350.361.520.211.140.230.530.060.360.060.36
JNZ 60Dolostone6.621.480.341.580.211.060.150.540.080.460.050.86
JNZ 61Dolostone5.531.370.331.480.181.070.170.530.070.440.070.66
JNZ 62Dolostone8.851.970.452.170.291.570.270.830.120.720.131.62
JNZ 63Dolostone5.261.060.241.050.150.730.130.380.060.370.050.63
JNZ 64Dolostone1.440.260.090.290.030.240.050.130.030.120.030.18
JNZ 65Siltstone1.950.330.130.30.030.230.050.130.030.150.040.44
JNZ 66Dolostone2.130.420.120.430.050.340.060.220.040.220.030.25
JNZ 67Dolostone4.270.890.221.150.140.680.140.360.060.340.040.43
JNZ 68Dolostone8.471.880.521.960.281.680.320.880.140.860.141.45
JNZ 69Dolostone8.951.990.542.060.321.680.320.880.130.850.131.53
JNZ 70Dolostone13.252.720.652.850.422.410.471.540.231.530.243.88
JNZ 71Dolostone7.821.640.4181.710.231.290.230.640.080.560.080.87
JNZ 72Siltstone15.553.430.843.250.452.620.521.620.241.620.253.85
JNZ 73Dolostone7.121.460.421.580.221.070.180.520.060.410.050.94
JNZ 74Siltstone9.721.930.942.080.261.650.331.020.161.040.152.86
JNZ 75Siltstone12.792.5970.952.620.382.570.571.920.292.070.34.66
JNZ 76Dolostone5.921.170.371.180.140.750.130.370.040.320.040.33
JNZ 77Siltstone15.473.1040.753.150.432.480.471.440.21.370.193.65
JNZ 78Siltstone12.122.350.562.360.341.910.381.220.171.220.173.02
JNZ 79Siltstone15.533.140.743.070.432.620.531.720.251.760.254.24
JNZ 80Dolostone12.762.550.552.540.352.150.441.330.231.370.223.36
JNZ 81Siltstone8.151.820.4830.271.540.260.710.090.580.080.86
JNZ 82Siltstone12.132.520.582.560.392.450.531.520.241.620.243
JNZ 83Dolostone8.131.870.452.360.271.580.250.780.10.670.081.17
JNZ 84Dolostone7.021.840.472.130.271.650.260.770.080.590.060.58
JNZ 85Dolostone7.041.450.371.520.191.070.250.630.090.620.071.92
JNZ 86Siltstone9.952.160.522.340.281.650.240.830.120.760.131.82
JNZ 87Dolostone8.261.940.532.240.321.850.330.980.140.890.110.82
JNZ 88Dolostone7.341.780.4441.910.251.470.260.720.090.610.090.77
JNZ 89Siltstone1.270.320.140.340.060.380.050.290.050.350.060.87
JNZ 90Siltstone8.651.820.431.870.261.260.260.630.10.570.091.37
JNZ 91Dolostone7.241.640.481.770.241.240.240.630.080.560.080.96
JNZ 92Dolostone6.461.720.552.030.291.560.270.720.090.630.090.46
JNZ 93Dolostone7.131.450.341.650.181.070.220.670.10.680.111.86
JNZ 94Dolostone5.451.3760.351.540.191.150.180.550.070.480.080.48
JNZ 95Dolostone12.192.290.482.330.241.530.320.960.130.960.133.09
JNZ 96Siltstone6.231.470.311.540.191.120.230.560.070.480.070.98
JNZ 97Dolostone5.451.450.321.540.191.040.160.460.040.330.060.29
6. Discussion

In the Jbel N’Zourk copper deposit, the mineralization is present at a macroscopic scale as a stockwork, disseminations and in karst pockets. The stockwork is composed by veins and veinlets filled with two successive mineralization phases:

1) A primary paragenesis composed by: bornite, chalcopyrite, associated with dolomite, quartz and calcite;

2) A secondary paragenesis composed by: covellite, chalcocite, digenite, malachite, azurite, chrysocolla, tenorite and cuprite associated with a gangue composed mainly of quartz-dolomite.

The veins and veinlets of this stockwork are oblique to the stratification plane. The majority of fractures families always present the same paragenetic evolution, mineralogy and textural. In consequence these different observations suggest that, with respect to the primary paragenesis of sulphides, all stockwork veins and veinlets are co-genetic (formed during in the same mineralization event). Microscopic studies reveal that the disseminations mineralizations correspond to microcracks and micro-fractures filled with the same mineralogical content, and texture characteristics as stockwork veins. In addition, disseminated copper containing mineral grains are directly connected to the stockwork veins. Consequently, all primary mineralization, from macroscopic to microscopic scale, is connected to the stockwork and deposited during a same hydrothermal fluid-assisted fracturing event of the host sedimentary rocks. Currently, according to the All these observations favor an epigenetic origin of the Jbel N’Zourk copper mineralization. In addition, the principal component analysis (PCA) of chemical data shows that copper does not have affinities with any of the lithological groups (siltstone, dolostone and breccias) present in the area. This result is also consistent with an epigenetic origin of the mineralization.

In comparison with most of the copper occurrences hosted in the Adoudounian cover of the Central Anti-Atlas, the Jbel N’Zourk deposit shows a particularity that is reflected in the association of mineralization with tectonic structures, this is confirmed by structural, microstructural and metallographic study. Both families of fractures NNW-SSE and E-W, also the folds associated with the main fault of Jbel N’Zourk, served as a main drain that controlled the placement of the mineralization. Many authors evoke a Variscan remobilization of a primary syngenetic mineralization within the Adoudou formation to explain the stockwork textures intersecting sedimentary structures [1] [4] [9] .

[1] describes kink bands and a rough cleavage developed in the vicinity of the previous fractures along the borders of the Bou Azzer El Graara inlier in the late Palaeozoic compressional event, generating in meter to decameter detachment folds scale which are common in the Adoudou formation, having a dominant NW-SE trending axes with subordinate NE-SW structures [1] [17] . These authors interpret these folds in terms of reactivation of Panafrican structures of the basement during the variscan orogenesis. In the Jbel N’Zourk the folds are associated locally with kilometre-scale sinistral strike-slip faults and SW-verging transpressional reverse faults, where the Adoudou formation coming, via an inverse play, on the unit of siltstones and sandstones of the series of “Lie de Vin”. This fault probably served as principal drain for the hydrothermal fluids that formed the mineralization of the Jbel N’Zourk deposit. Under such conditions, the age of the copper mineralization event at the Jbel N’Zourk deposit could probably be contemporary to the deformation of the cover during late Paleozoic compression. Currently, we propose that the copper mineralization presented in the Adoudou formation of the late Ediacaran to lower Cambrian cover is related to the variscan reactivation of the basement structures and addition to the variscan faults that drained the hydrothermal fluids which precipitated its copper content as a stockwork in the deformed terrains of the Jbel N’Zourk.

7. Conclusions

The copper mineralization in the Jbel N’Zourk deposit is epigenetic and is controlled by variscan tectonic structures that are associated with folding in the Adoudou formation. As a consequence, the copper mineralizing event occurred during this period. Most of the copper mineralization is present as stockwork, in fractures, faults and karst fill pockets. The location of the better-mineralized zone near faults and fractures indicates that it was epigenetic mineralization; it is possible that it occurred during the late variscan shortening. The position of the Jbel Boho volcanic series just below the mineralization can explain the origin of hydrothermal fluids.

The benefits of such an approach have a dual interest; 1) Scientific, contributes to a better understanding of the mechanism of vein formation process and understanding of the relationship between copper deformation-mineralization in the Adoudounian cover of the Central Anti Atlas, and 2) economics, contributes to a better knowledge of specific ore body geometry and distribution, thus the deformation affected the terrain and hence highly recommended in exploration program, but can also provide solutions to the exploitation problems.

Acknowledgements

The authors would like to thank all those who have contributed, directly or indirectly, to its elaboration, to who have been teaching, guiding and encouraging. The thanks are also addressed to the MANAGEM group (SOMIFER) for their collaboration and help during the field survey, as well as the reviewers for their helpful comments and suggestions.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

Cite this paper

Ait Yazza, A., Bouskri, I., Raji, M., Haissen, F. and Zoraa, N. (2023) Copper Mineralization in the Lower Cambrian Cover of Jbel N’Zourk (Central Anti Atlas, Morocco): Tectonic-Mineralizations Relationships. Open Journal of Geology, 13, 1195-1219. https://doi.org/10.4236/ojg.2023.1311051

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