Eastern Anti-Atlas Research Articles

WITHDRAWN: Improving Lithological Mapping of Tazoult n'Ouzina Massif, Eastern Anti-Atlas, Morocco: Evidences from remote sensing and field Investigations

WITHDRAWN: Improving Lithological Mapping of Tazoult n'Ouzina Massif, Eastern Anti-Atlas, Morocco: Evidences from remote sensing and field Investigations

Integrating geochemical insights and remote sensing for enhanced identification of hydrothermal alterations in the Igoudrane region, Anti-Atlas, Morocco

The Moroccan Anti-Atlas is distinguished for its significant mining potential. The Igoudrane region, which is the focus of this study, is located within the Imiter inlier, one of the notable inliers of the eastern Anti-Atlas. The current study aims to evaluate the mineralogical and geochemical composition of the rocks in the Igoudrane area using the ICP-MS with 4 acids, besides identifying the hydrothermal alteration indexes using major elements provided by the geochemical data, and remote sensing techniques. The study was accomplished using the thin sections for mineralogical description, as well as the ICP-MS with 4 acids, which provides data on major, trace, and rare earth elements. The alteration indexes employed were the Ishikawa alteration index (AI), the Chlorite Saturation Index (CSI), the Sericite Saturation Index (SSI) and the Alteration Intensity coefficient (AIC). These indexes were complemented by a chloritization and sericitization mapping using the SWIR-VNIR data of ASTER. We employed the band ratios of chlorite [(B6 + B9)/(B7 + B8)] and sericite [(B5 + B7)/B6], achieving an accuracy of 80.95% for sericite and approximately 85.71% for chlorite. The mineralogical and geochemical study revealed the presence of granodiorites, granites, monzonites, monzo-diorites, diorites, gabbro, and gabbro-diorites, andesites, rhyolites, and trachydacites. These rocks belong to a highly potassic calc-alkaline and peraluminous series, which are fairly typical of granitoids of mixed origin. The plutonic rocks of Igoudrane were formed across diverse geodynamic contexts, ranging from pre-plate to post-collisional settings, and the volcanic rocks were emplaced in geodynamic settings, which are island arcs or active continental margins. The quasi-positive correlation observed in the Al vs. CSI and SSI diagrams reveals that higher aluminum content is linked to increased chloritization and sericitization intensities. Furthermore, The AIC values of the Igoudrane rocks were ranging between 52.25% and 67.53%, indicating that they have undergone moderate to high chemical alteration. The remote sensing techniques employed improve the distribution of these alteration minerals.

Lineaments Extraction and Analysis Using Sentinel 2B, Sentinel 1A Data and ALOS PALSAR DEM: A Case Study of the Igoudrane Region, Jbel Saghro, Eastern Anti-Atlas, Morocco

The remote sensing techniques have been used several years ago in many geological studies, and have proved their utility especially in lineament extraction. During this research, we extracted the lineaments automatically as well as manually in the Igoudrane region, Imiter inlier, eastern Anti-Atlas. The purpose of this research is to extract and map lineaments in the study area, and then compare the results provided, where the VNIR bands of Sentinel-2B, Sentinel-1A and the ALOS PALSAR DEM (12.5 m) were used. The directional filters were applied to the VNIR bands of Sentinel-2B into six directions, in the interest of attaining a significant lineament contrast. The VH and VV radar data provided the greatest number of lineaments (7243) by LINE module algorithm, while the shaded relief and slope were applied to the ALOS PALSAR DEM, which gave a higher number of lineaments than the VNIR bands of Sentinel-2B (4699, 4647 respectively). The manual extraction on the VV and VH polarizations yielded 441 lineaments, while the VNIR bands of Sentinel-2B provided 453 lineaments. Furthermore, the main orientations of the lineaments are NE-SW, ENE-WSW and NNE-SSW. The lineaments extracted from the VNIR bands (Sentinel-2B) and ALOS PALSAR’s DEM exhibited an optimal match along with the fractures digitized manually and from the geological maps of the research area. The results revealed that Sentinel-1 data is less efficient than ALOS PALSAR DEM data, especially in arid regions where the capacity of DEM radar waves to penetrate rises for thinner sedimentary layers, offering deeper information.

Contourite-drift archive links Late Devonian bioevents with periodic anoxic shelf water cascading

Analysis of a Devonian contourite depositional system in the eastern Anti-Atlas of Morocco reveals the formation of widespread erosional hiatuses and organic-rich bioclastic contourites (ORCs) coinciding with the expansion of an anoxic water mass during Frasnian bioevents, ultimately culminating in the Kellwasser crisis (Frasnian-Famennian extinction event). The identified contourite terrace formed on the uppermost slope of the northern passive margin of Gondwana. Its inner part was bounded by an along-slope contourite channel and a small mounded drift at its downslope margin. Facies- and drift-scale contourite features evidence northwest-directed bottom currents driven by repeated overflows of dense, highly saline, anoxic water originating from the northern Gondwana Epicontinental Sea. These periodic overflows were channeled through the Ougarta trough, then deflected westward over the Tafilalt contourite terrace by the Coriolis force and cascaded downslope until reaching a density equilibrium level, probably forming an intermediate water mass. The cascading of dense, anoxic shelf water supports the photic-zone eutrophication (top-down) model proposed for the Kellwasser crisis and related Devonian anoxic events. We propose a direct link between the anoxic overflows and the Devonian evolutionary events.

The euphyllophytes of a new Givetian plant assemblage from the eastern Anti-Atlas, Morocco

The Middle Devonian is a transitional period for the first vascular plants, which acquire modern vegetative and reproductive structures, diversify considerably and, within the euphyllophytes, evolve the first representatives of modern plant groups, the monilophytes and lignophytes. However, the dynamics of this diversification across the different paleocontinents remains obscure, particularly within Gondwana. The upper Givetian locality of Oum el Jerane, in southeastern Morocco, has yielded a new assemblage of anatomically preserved plant remains whose description contributes to a better understanding of the floras of the northern margin of Gondwana during the Middle Devonian. The euphyllophytes include one iridopterid, Arachnoxylon minor, two cladoxylopsids, one of which represents the new genus Jerana, and two aneurophytales affiliated with the genus Triloboxylon. The cladoxylopsid remains from Oum el Jerane correspond to relatively small plants compared to the well-known coeval cladoxylopsids of Laurussia. Compared to the taxonomic composition of the four phytochoria recently defined for the Middle Devonian, the Oum el Jerane plant assemblage corresponds to the ‘subtropical’ phytochorion, which is close to the ‘Laurussia’ phytochorion, but which would correspond to drier environmental conditions.

Mineralogical characterization and structural control of the Tadaout-Tizi n’Rsas vein field (eastern Anti-Atlas Morocco)

The Tadaout-Tizi n’Rsas (TTR) polymetallic (Pb, Cu, Zn) vein field, located at the southeastern of the Moroccan eastern Anti-Atlas, is hosted in sedimentary sandstone formations of the Ktaoua Group of the upper Ordovician. These deposits are reported to be late Variscan to Post-variscan in age, and are related to the emplacement of late Permian doleritic magma event outcropping in the Tafilalet region. Structural and paragenetic studies of the TTR mineralization deposit were conducted in order to establish a general model of the mineralization. A two-stage model of the formation of the mineralized veins of the TTR vein field is proposed herein. The first episode is attributed to the late Variscan phase. It is a trantensive regime characterized by the presence of lenticular structures related to the normal dextral movement of the major faults. This episode is coeval with the emplacement and brecciation of the polymetallic mineralization of the TTR vein field (galena, chalcopyrite, sphalerite, and pyrite). The second episode is associated with normal faults, during the extensional phase corresponding to the tectonic relaxation of shortening (Upper Permian) and more probably during the Atlantic rifting. It is characterized by the formation of a banded texture of mineralization.

Mafic microgranular enclaves and magmatic fabrics in the Ediacaran granitoids of Saghro, Eastern Anti-Atlas: Insights into magma emplacement and tectonic evolution

The Saghro inlier in the Anti-Atlas belt of Morocco comprises several granitoids dating from 600 to 550 million years ago (Ma), which are overlain by a volcano-sedimentary series. In particular, the granodioritic plutons exhibit widespread enclaves, which is a tool for emplacements mode and magma interaction processus during the Ediacaran evolution of the Anti-Atlas belt. This paper presents a detailed field mapping, petrographic analysis, and deformation quantification of the mafic microgranular enclaves (MMEs) and their host granitoids to characterize the emplacement mode of the plutons and the origin of MMEs.Macroscopically, the MMEs are rounded to ellipsoidal shapes and characterized by sharp, crenulated contacts, fine-grained textures, and some of them include fragments of host rock and feldspar xenocrysts. Petrographically, the MMEs exhibit a range of compositions from gabbroic to quartz diorite, and they are characterized by the presence of acicular apatite, quartz-feldspar ocelli, poikilitic and zoned plagioclases, which are the result of mixing/mingling of mafic and felsic magmas during the genesis of MMEs. The magmatic structures and enclave's organization in Saghro granitoids indicate two styles of emplacement. The c. 600 Ma Iknioun granodiorite exhibits an S-sigmoidal structure, representative of a syntectonic emplacement model within a transpressive dextral movement along E-W shear zones. While, in the 580-560 Ma Oussilkane, Tagmout, Igoudrane, and Bou Teglimt plutons, the organization of magmatic flow and orientations of enclaves suggest that the magma was emplaced as a post-tectonic dome. The variation in emplacement mode and the decrease in deformation intensity from the c. a. 600 Ma in the Iknioun pluton to the 580-560 Ma for the others plutons indicate a progressive shift in deformation regime from transpressive during the middle Ediacaran to a transtensive regime in the late Ediacaran, highlighting the progressive transition from Pan-African/Cadomian orogeny to Cambrian rifting.

Stratigraphy, geochronology, geochemistry and Nd isotopes of the Ouarzazate Group, Anti-Atlas, Morocco: Evidence of a Late Neoproterozoic LIP in the northwestern part of the West African Craton

In the eastern and central Anti-Atlas of Morocco, the Late Neoproterozoic Ouarzazate Group (OG) forms a ∼ 2 km-thick section of volcano-sedimentary rocks deposited during intermittent magmatic activity, spanning a time period between 590 and 540 Ma. In the eastern Anti-Atlas, the stratigraphy of the OG, termed IMS (Imiter Mine succession), includes four units that reflect a gradual change from fluvial to lacustrine depositional sedimentary environments. In the central Anti-Atlas, the deposition of the OG occurs within a caldera environment, consisting of five units referred to as BMS (Bou Azzer Mine succession). UPb dating on zircon from the rhyolite lava flow at the top of the IMS constrains the latest lava flow of the IMS to 570.7 ± 2.1 Ma. In the Bou Azzer inlier, the stratigraphically correlated basal andesite and top dacite lava flows were emplaced at 590.6 ± 4.2 Ma and 555.9 ± 20.4 Ma, respectively, suggesting that the OG was constructed through successive pulses within a long-lived magmatic episode. The magmatic rocks display geochemical signatures typical of continental arc magmas, including high-K calc-alkaline to shoshonite composition, enrichment in LILE, and negative Nb, Sr, Ti and P anomalies. Nd isotopes indicate that magmas supplying the plumbing systems of the IMS and BMS constitute transitional products resulting from a combination of orogenic and intraplate volcanism, involving deep crustal recycling. The compositions of these magmas evolved through processes of crustal contamination, bulk assimilation, and minor fractional crystallization of the parent melt. High εNd values of the BMS rocks argue for a juvenile origin, whereas lower εNdt recorded in the IMS likely reflect old crustal protoliths and an overall less contribution of juvenile material in their source. The magmatic rocks of the OG are interpreted as products of a large igneous province (LIP) developed by a post-collisional delamination model that initiated tens of millions of years after the subduction-collision process stage of the Pan-African orogeny in the northwestern part of the West African Craton (WAC).

Metallogeny and Genesis of Fault-Filling Barite-Sulfide Veins (Ougnat, Morocco): Petrography, Fluid Inclusion, and Sr-S Isotopic Constraints

The Ougnat Massif of the eastern Anti-Atlas (Morocco) hosts barite and sulfide vein-type deposits of vital economic importance. With over 150 mineralized structures reported in the Ougnat Massif, the ore-bearing ones are predominantly composed of barite, quartz, calcite, and minor portions of sulfides. The mineralized veins are driven by NW-SE and NE-SW to E-W oblique-slip opening faults that cross both the Precambrian basement and its Paleozoic cover. The mineralized structures occur as lenses and sigmoidal veins that follow stepped tension fracture sets oblique to the fault planes. These geometries and kinematic indicators of these structures point to a predominantly normal-sinistral opening in a brittle-ductile tectonic setting. The S isotopic compositions of barite from the Ougnat Massif (+10.8 to +19.5‰) fall mostly within the range of δ34S values of Late Triassic to Jurassic seawater, thus suggesting that some of the SO2− in barite comes from seawater sulfate. This range of δ34S values also corresponds approximately to the hydrothermal barite context. The 87Sr/86Sr ratios of barite, which range from 0.710772 to 0.710816, lie between the radiogenic strontium isotopic compositions of deposition by hydrothermal solutions, and also coincide with the non-radiogenic isotopic signature of Triassic to Jurassic seawater. Based on a fluid inclusions study, the ore-forming fluids were a mixture of two or more fluids. A deep hot fluid with an average temperature of 368 °C leached the granodiorites and volcanic-sedimentary complex of the Ouarzazate Group. This fluid provided the hydrothermal system with most of the Ba, radiogenic Sr, and some of the dissolved S. A second, shallow fluid with an average temperature of 242 °C was derived from Late Triassic to Jurassic seawater. The barite mineralization of the Ougnat Massif constitutes a typical example of vein-type mineralization that occurred along the northern margin of the West African Craton and regionally tied to the central Atlantic opening.

Contribution of Remote Sensing to the Mapping of Lineaments and Ore-Mineral Occurrences in the Taghbalt Region, Moroccan Eastern Anti-Atlas

The Taghbalet region is a part of the Paleozoic cover of the Moroccan Anti-Atlas, known by a rich mineral potential of vein type. This paper presents the results of a field investigation and processing of Landsat 8oli and Aster satellite images. The pre-processing allows for improving the image quality by applying a radiometric calibration, atmosphere correction and a pan-sharpening correction. Landsat-8 oli data is used to map structural lineaments including fracture and/or vein. C compositions ( RGB: 2, 5 and 7) and band ratios (5/7, 3/1, 4/3 and 5/7, 5/4, 3/1) were applied, both of which showed the lithological contrast between formations. Then directional filters (N-S, NE-SW, E-W and NW-SE) were applied on the spectral bands and principal component analysis to map the different lineaments. Validation and correction of lineaments obtained by automatic extraction are based on visual interpretation and field verification. The mining prospecting is performed using ASTER multispectral images. Therefore the results obtained show that we have two main directions; one E-W and the other NE-SW. The majority of these lineaments are concentrated in the south of the area. The results of mapping the hydrothermal alteration zones show us that these zones have a clear relationship with the fault.

Solutan echinoderms from the Fezouata Shale Lagerstätte (Lower Ordovician, Morocco): diversity, exceptional preservation, and palaeoecological implications

In the Lower Ordovician of Morocco, solutan echinoderms are relatively common, locally abundant, geographically widespread (Central and Eastern Anti-Atlas), and biostratigraphically long-ranging (late Tremadocian–mid Floian) components of the Fezouata Biota. The lower part of the Fezouata Shale (late Tremadocian) yielded one specimen, here tentatively identified as a Castericystis-like syringocrinid, with exceptionally preserved internal soft parts presumably corresponding to the distal region of the gut. Most solutan remains from the Fezouata Shale are assigned to Plasiacystis mobilis, which was already known from the late Tremadocian of France and the Darriwilian of the Czech Republic and United Kingdom. Several isolated dististeles provisionally identified as Plasiacystis sp. may belong to large individuals of P. mobilis or a new taxon. Several specimens of late Tremadocian solutans from the Fezouata Shale, morphologically intermediate between Minervaecystis vidali (late Tremadocian, France) and Plasiacystis mobilis, are assigned to Nimchacystis agterbosi gen. et sp. nov. The diagnosis of the syringocrinid family Minervaecystidae is modified to include the four genera Minervaecystis, Nimchacystis, Pahvanticystis, and Plasiacystis, all characterised by an ovoid theca, a laterally inserted feeding appendage, and a twisted, flattened dististele. Minervaecystids are interpreted as active epibenthic detritus feeders, using their dististele to crawl on soft substrates. The newly described solutan taxa highlight that the benthic communities of Fezouata Biota are more diverse than what was previously described.

Variscan structural evolution and metallogenic implications at the paleozoic maider basin, eastern anti-atlas, Morocco

In the Moroccan eastern Anti-Atlas, the Paleozoic Maider basin, hosts a range of economic mineral deposits, including Cu, Pb, Fe, and barite forming an important mineralized vein system. In this study, detailed mapping of fractures and veins, structural analysis, and measurements have been integrated to understand the structural control, the tectonic evolution, and fault kinematic history in the Paleozoic outcrops of the Southern margin of the Maider basin. The structural analysis shows two folding phases: (i) a first phase, which generates WNW-ESE-trending folds, in response to an NNE-SSW compression, likely, of Late Westphalian age. And (ii) a second phase which develops N–S metric folds, under a NE-SW to E-W compression, compatible with the Late Variscan shortening, known in the East Anti-Atlas and the Ougarta belt during the Stephano-Autunian period. Moreover, three main fault systems were distinguished: WNW-ESE to E-W, NE-SW and scarcely N–S. These fault systems record evidence of a previous extensional tectonic event that probably corresponds to the Devonian extensional event. During the late Variscan shortening, these faults were reactivated into a left-lateral strike-slip movement with a small reverse component for the WNW-ESE to E-W faults, and right lateral strike-slip motion for NE-SW ones. The mineralization primarily takes place within a vein-type system, which is predominantly found in a network of faults oriented between N30 and N60. These ore bodies present frequently lenticular and banded geometries, and do not show any evidence of deformation, suggesting probably a post Variscan emplacement age. Thus, we could link the mineralization emplacement to the Triasic Central Atlantic rifting.

Multiscale Structural Analysis of Ediacaran–Cambrian Rocks on the Northeastern Edge of the Saghro Inlier (Eastern Anti-Atlas): Relevance of Post-Cambrian Deformation

The Ediacaran–Cambrian rocks on the northeastern edge of the Saghro inlier experienced polycyclic tectono-thermal events, which are reported here based on a multiscale structural analysis, from field measurements to fluid inclusion planes. Three striking populations were identified, cutting across both the Ediacaran and Cambrian formations. These tectonic structures were generated during four tectonic events. (i) E-W-striking structures that host ore mineralized bodies (sulfide, oxide, quartz, and barite). They display a polyphase tectonic history, caused by a dextral movement in response to a NW–SE-oriented shortening, leading to the formation of quartz gashes and veins. This tectonic event took place during the Neovariscan. These E–W-striking structures were subsequently reactivated during the Mesozoic time under a sinistral strike-slip regime as a result of NE–SW shortening syn-kinematic with barite mineralization. (ii) NE–SW-striking strike-slip structures (dextral or sinistral) crosscut the E–W-striking veins. These faults are related to the NW–SE-oriented shortening that occurred during the Neogene. (iii) The last tectonic episode, related to the N–S shortening, took place during the late Neogene to the Quaternary period. It resulted in NW–SE to N–S-striking structures that were related to dextral and sinistral strike-slip movements, which crosscut the preexisting E–W structures.

Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco)

Viséan coiled nautiloids from North Africa are only poorly known. From the Mougoui Ayoun, Zrigat and Hamou-Rhanem formations of the eastern Anti-Atlas, we describe coiled nautiloids, which belong to the genera Rineceras, Stroboceras, Temnocheilus, Vestinautilus, Maccoyoceras, Endolobus, Epidomatoceras, Liroceras, Ephippioceras, and Solenochilus. The new species Temnocheilus imazighenorum sp. nov., Temnocheilus aubrechtovae sp. nov., Vestinautilus kesslerae sp. nov., Endolobus rota sp. nov., Epidomatoceras ebbighausenorum sp. nov., Liroceras vermis sp. nov., Liroceras karaouii sp. nov., Ephippioceras pygops sp. nov., Solenochilus lucynae sp. nov. and Solenochilus pohlei sp. nov. are described; six taxa are kept in open nomenclature. The assemblage is composed of the three superfamilies Trigonoceratoidea, Clydonautiloidea and Aipoceratoidea and shows a wide spectrum of conch morphologies, ranging from widely umbilicate compressed forms to involute compact forms, reflecting a broad ecological variation.

Microbially induced sedimentary structures from the Ediacaran of Anti-Atlas, Morocco

The Eastern Anti-Atlas of Morocco hosts an early Ediacaran turbiditic series (Saghro Group) (630–600 Ma) unconformably overlain by thick late Ediacaran (580–550 Ma) terrestrial volcano-clastic formations (Ouarzazate Supergroup), with thin and geographically limited paralic shallow marine sedimentary rocks.This paper presents the first description of structures related to the former presence of extensive microbial mats developed in marine, fluvial, and lacustrine environments during the Ediacaran in the Eastern Anti-Atlas. These microbially induced sedimentary structures (MISS) are largely found in well-laminated fine- to coarse-grained sandstone and sandy-carbonate. They also cover vast bedding planes and occur in almost all sedimentary successions. MISS types include: gas domes, wrinkle structures, reticulate patterns, overflips and roll-ups, multidirectional linear ridges, sand cracks and biolaminated deposits. Based on morphology and petrographic macro and microfabrics, these microbially induced structures are very similar to those of modern photosynthetic cyanobacteria mats. Together with previously reported stromatolites, these newly reported microbial mat structures could have played an important ecological role in stabilizing siliciclastic sediments, as well as sustaining localized zones of high oxygen production in the Ediacaran marine and terrestrial paleoenvironments of the Anti-Atlas. The widespread geographic distribution and consistent occurrence of microbially induced sedimentary structures (MISS) in fluvial and lacustrine sediments present compelling paleontological evidence supporting the extensive greening of the land surface during the late Precambrian period.

A unique pericyclid from the Viséan of the eastern Anti-Atlas (Morocco) and other Helicocyclinae n. subfam. (Goniatitida)

The Jebel Begaa region of the eastern Anti-Atlas in SE Morocco yielded a single, very well-preserved goniatite that is closely related to Helicocyclus divergens Riley, 1996 from the lower Viséan (Chadian) of northern England. Both are placed in a new genus, Tectocyclus n. gen., with the Moroccan T. herbigi n. sp. as the type species. Characteristic are its subtriangular suture elements, which distinguish it strongly from Helicocyclus gracillimus Schindewolf, 1951, which is revised based on the re-examination of its types. The type-species of Helicocyclus is characterized by wide, bell-shaped lateral lobes, unlike as in described helicocyclids from the upper Tournaisian and Viséan of North Africa, Russia, and Central Asia. These are assigned, partly with reservation, to Serpenticyclus n. gen., with the oldest species, Helicocyclus fuscus Korn, Bockwinkel, Ebbighausen, and Klug, 2003, as the type-species. All three genera form the Helicocyclinae n. subfam., which first appeared in North Africa, migrated at the end of the Tournaisian across the Variscan Sea to the southern shelf of Laurussia, to Central Asia, and to the Urals seaway, where it survived into Arundian levels of the Viséan.

Metallogenesis of the Cu-Ni sulfide type mineralization in the Bounhas vein deposit (Eastern Anti-Atlas, Morocco): Insights from ore mineral paragenesis and fluid phases

The Moroccan Anti-Atlas hosts numerous precious metal (Au, Ag, Co, PGE...) and base metal (Cu, Pb, Zn...) mineralizations that are developed in various geological and geodynamic contexts. Some of these mineralizations, such as copper and nickel, are known in the form of deposits at the scale of the Anti-Atlas and are the subject of mining development and exploitation. This is the case of the Bounhas deposit, which is located in the southern part of the Eastern Anti-Atlas, 50 km SE of the city of Alnif. It is characterized by Cu, Ni, Pb and Zn mineralizations, which are essentially hosted in sedimentary terrains of a sandstone-pelitic nature of the upper formation of the second Bani group (Upper Ordovician). These terrains are affected by brittle deformations that have developed faults that host the lenticular vein mineralization in an E-W direction. The arrangement and textural relationships between the mineral phases of the Bounhas deposit have allowed to distinguish two distinct mineralizing events: (i) a primary hydrothermal event subdivided into 3 metalliferous episodes the first, with Fe, characterized essentially by pyrite mineralization in a carbonate gangue (ankerite and siderite); the second with Cu, Ni, As ± Zn ± Pb, precipitates most of the arsenopyrite, sphalerite I, galena I, gersdorffite and chalcopyrite mineralization in a quartz gangue; and the third, with Pb, Zn, and Ba, places galena II and sphalerite II in a barytic gangue. A late supergene alteration event, characterized by the appearance of minerals typical of cementation, sulfation, carbonation and oxidation zones (covellite, native copper, anglesite, malachite, azurite and iron oxides). Moreover, the study of the fluid inclusions associated with the Cu, Ni, As ± Pb ± Zn mineralization from the Bounhas deposit reveals the presence of two types of fluids: (i) a hypersaline fluid, characterized by a salinity varying between 25 and 30 wt% NaCl eq and a homogenization temperature: Th = 200 to 240 °C. This fluid would be responsible for the development of the copper-nickel-arsenic mineralization of this deposit and (ii) a late medium saline fluid (12 to 15 wt% NaCl eq) and a homogenization temperature Th = 80 °C to 120 °C, to which would be attributed the development of the Pb and Zn mineralization of this deposit.

Fault-controlled barite veins of the eastern Anti-Atlas (Ougnat, Morocco), a far-field effect of the Central Atlantic opening? Structural analysis and metallogenic implications

Tectonic and micro-tectonic studies at different scales are of primary importance in a modern metallogenic investigation. In the Ougnat massif of the eastern Anti-Atlas belt (Morocco), the barite ore deposit is hosted within mafic to felsic rocks of the Ediacaran Saghro and Ouarzazate groups together with their folded Paleozoic cover. Here, we provide for the first time new field-based data on the tectonic control of barite mineralization, and their relation with regional tectonic events. The mineralization occurs in brittle-ductile structures as a vein-type system, mainly hosted within NE-SW to E-W and NW-SE strike-slip-normal faults. Economic orebodies spread frequently along the Precambrian-Cambrian contact zone thus acting as open conduits for mineralized fluid flow. The geometry of hosted barite sigmoidal lenses corresponds to “pull-apart” or “tension gashes” openings, commonly arranged en echelon arrays along the bearing transcrustal faults. The occurrence of predominant massive and breccia internal texture implies a tectonic-mineralizing collapse process in an extensional tectonic context. Kinematic pattern, directional distribution and host-rock age relationship point to a syntectonic barite control probably occurred during the NW-SE Atlantic rifting, as already attributed to similar deposits in the neighboring Ougarta and Atlas-Meseta domains.The barite ore is quantitatively and qualitatively more preserved in competent host rocks than those with ductile behavior, thus offering a useful hint for further barite exploration in this part of the Anti-Atlas fold and thrust belt.

Litho-structural and hydrothermal alteration mapping for mineral prospection in the Maider basin of Morocco based on remote sensing and field investigations

Landsat 8 OLI images were processed using band ratio (RB), principal component analysis (PCA), composite ratios (CR) 4/2–6/7-6/5 were used to map lithology, geological structures, and hydrothermal alteration zones. The studied area, Jbel Boulachrhal, is characterized by copper, barite, and amethyst mineralization and is in the Maider basin at the level of Morocco's eastern Anti-Atlas, which is formed by Paleozoic landfills. This vein-type mineralization, which oriented NE-SW, NNE-SSW, to E-W corresponds to the main orientations of mapped faults using remote sensing and confirmed by the field study, and is revealed by the lineaments extracted from the processing of Landsat 8 Oli. The mineralization is polymetallic, with copper oxide and sulfide dominating, as well as quartz, amethyst, lead, and barite. Remote sensing techniques combined with field research have showed that high lineament density areas that frequently correlate with areas of hydrothermal alteration are highly related to the occurrences of these mineralizations. These findings indicate that satellite image processing techniques (lineament density and hydrothermal alteration zones) will most likely be used in mining exploration.

The Oumjrane-Boukerzia Mining District (Eastern Anti-Atlas, Morocco): Constraints of its geological and tectono-magmatic setting

Purpose. The purpose of the present research is to provide a new lithological, structural and magmatic features of the Oumjrane-Boukerzia Mining District. The results obtained are used to guide exploration works for identifying the new Cu, Ni, Pb, Zn depositions and Ba-bearing mineralization within the whole Oumjrane-Boukerzia domain. Methods. This research is based on detailed mapping, structural surveys and geochemical studies performed on the magmatic rocks in the studied area. Findings. Structural and microstructural analyses of the studied area have revealed three complex polyphase tectonic events related to the Variscan orogeny: (i) an extensive phase during the Devonian period; (ii) a NW-SE compressional phase of Namuro-Westphalian age; (iii) a NE-SW compressional phase of Stephanian-Autunian age, and (iv) an extensive late phase probably related to the opening of the Central Atlantic ocean during the Late Trias-Jurassic periods. The sedimentary rocks of the district are locally intruded by small undated gabbroic intrusions. Geochemically, these gabbroic bodies are described as olivine-rich gabbros with a continental tholeiitic affinity and suggested to be related to the Central Atlantic magmatic province (CAMP) during the Pangea break-up. Originality. The present study describes the host-rocks and structural events responsible for Cu, Ni, Zn, Pb deposition and Ba-bearing mineralization in the Oumjrane-Boukerzia Mining District (Eastern Anti-Atlas, Morocco). Practical implications. The geological studies, especially lithostratigraphic, tectonic and magmatism are essential in the mineral exploration. They help exploration geologists identify and define metallotects to discover new minerals.