Sericite Schist Research Articles

×Gymnigritella suaveolens (Orchidaceae), a New Natural Hybrid to the Flora of Serbia

×Gymnigritella suaveolens (Orchidaceae), a natural hybrid between Gymnadenia conopsea and Nigritella rhellicani, was found at Mt Kopaonik for the first time in Serbia, representing its single known locality in the Central Balkans. Morphological characteristics, distribution data, habitat and ecological preferences are indicated. The hybrid was found at 1552 m a.s.l., on sericite schists, as a member of the Festuco-Deschampsietum flexuosae grassland community. Two hybrid specimens were recorded at the site where the two parental species grow in sympatry, and where the population size of G. conopsea was larger than the population size of N. rhellicani.

Generation of isotopically enriched giant Lincang Batholith by disequilibrium melting of the heterogeneous lower crust

Deciphering the origin of granitoids with enriched isotopic compositions is essential to understanding the mechanism of continental growth and reworking. Establishing their origin is also an effective solution to the decoupled interpretations between geochemical and isotopic observations in competing petrogenetic models. This paper reports on the whole-rock major and trace elements, Sr-Nd-Pb-Hf isotopes, and zircon UPb age and Hf isotope data of samples from the Late Triassic Lincang Batholith in SW China. The hornblende-bearing granodiorites are weakly peraluminous, whereas the coeval biotite monzogranites are generally strongly peraluminous. These two types of granitoids show identical and extremely enriched isotopic compositions with (87Sr/86Sr)i ratios of 0.71991 to 0.74302, whole-rock εNd(t) values of −13.5 to −10.1, and εHf(t) values of −13.4 to −10.3, as well as a large variation of zircon εHf(t) values of −17.6 to +0.6. The inherited zircons from both suites of samples show similar age peaks (ca. 950 Ma and ca. 1150 Ma), trace element concentrations, and εHf(t) variations to those of the detrital zircons from the Lancang Group. These similarities indicate that these rocks are most likely derived from the anatexis of the Lancang Group that is mainly composed of quartz schist, sericite schist, greenschist, chlorite albite schist, and minor eclogite. On the other hand, the Lancang Group is characterized by more enriched isotopic compositions than the granitic batholith with whole-rock εNd(225 Ma) value of −13.3 and εHf(225 Ma) value of −19.1, but identical to those of the average εHf(225 Ma) values of inherited and detrital zircons (−18.1 and − 16.3). This isotopic fractionation between the granitoids and the Lancang Group may result from disequilibrium melting of the Lancang Group with different dissolution behavior of accessory minerals (i.e., zircon, monazite, apatite, titanite, etc.). The Lincang Batholith is on average more silicic and richer in incompatible elements than the upper continental crust, suggesting that the isotopically enriched giant granitic batholith is a mature magmatic response to continental reactivation and reworking.

Chronolgy and Geochemistry of the Sijiaying Iron Deposit in Eastern Hebei Province, North China Craton: Implications for the Genesis of High-Grade Iron Ores

The Sijiaying iron deposit is located in the Eastern Hebei area of the southern section of the northern margin of the North China Craton (NCC) and is the largest single iron deposit in China. The deposit contains many banded iron formations (BIFs) and was proven to have more than 3 million tons of high-grade iron ore resources. This study carried out geochemistry and zircon U–Pb analysis of normal-grade iron ore, high-grade iron ore, and wall rock (biotite–leptynite, chlorite–sericite schist) in the Sijiaying deposit and discussed the genesis and metallogenic age of high-grade iron ore. BIFs have low concentrations of Al2O3 and TiO2 and high field strength element (HFSE) depletion, indicating almost no contamination via terrestrial debris. The standardized post-Archean Australian shale (PAAS) rare earth element (REE) distribution pattern indicates that the iron formation exhibits positive Eu, Y, and heavy rare earth element (HREE) anomalies and lacks negative Ce anomalies, indicating that the Sijiaying BIF was enriched with iron sources via high-temperature hydrothermal fluids from the seabed and deposited in an anoxic ancient marine environment. In addition, geological field work identified two types of high-grade iron ore in the mining area: primitive sedimentary and hydrothermally altered high-grade iron ore. Further ore geochemical research showed that the primitive sedimentary-type iron ore is similar in geochemistry to the BIF. In addition to low Eu/Eu* values, the hydrothermally altered high-grade iron ore shows geochemical characteristics similar to those of the BIF, suggesting that they share the same iron source but did not form at the same time. The total large ion lithophile element (LILE) (Sr, Ba, Pb) contents in primitive sedimentary-type high-grade iron ore are higher than those in hydrothermally altered high-grade iron ore, indicating that LILEs are carried away via fluids during the hydrothermal alteration process in normal-grade iron ore. The geochemical characteristics of biotite–leptynite and chlorite–sericite schist include high contents of SiO2 and Al2O3, light rare earth elements (LREEs), LILE enrichment (Rb, Ba, Sr, Zr), and HFSE depletion (Nb, Ta, P, Ti), characteristics that are similar to island arc volcanic rocks. The reconstruction of the original rock indicates that the wall rock is a product of volcanic sedimentary cycles in an island arc setting. Zircon cathodoluminescence images and LA–ICP–MS zircon U–Pb dating can be divided into four age groups (3283 Ma, 2547 Ma, 2500 Ma, and 2407 Ma), which correspond to the earliest volcanic activity in eastern Hebei, the main mineralization age of the Sijiaying BIF (the mineralization age of primitive sedimentary high-grade iron ore), a regional tectonic–metamorphic event, and the occurrence of migmatization (the mineralization age of hydrothermally altered high-grade iron ore), respectively. Therefore, the Sijiaying BIF and primitive sedimentary high-grade iron ores were deposited and mineralized at 2547 Ma, and the iron orebody was later altered via the hydrothermal solution at 2407 Ma, forming large-scale high-grade iron ores.

Zircon U-Pb, whole-rock Rb-Sr and K-Ar ages of metamorphosed and metasomatized paleosol at the base of the Paleoproterozoic Aravalli Supergroup, NW India: A two-billion-year record of tectono-thermal events

The Precambrian paleosols are good proxies for deciphering paleoredox conditions. They are also good indicators of thermal events that affect the metamorphic terrane. The Rb-Sr isochron ages of the Precambrian paleosols are good indicators of the timing of alkali metasomatism. This work presents zircon U-Pb, whole-rock Rb-Sr isochron, and K-Ar ages of a metamorphosed and metasomatized paleosol occurring at the base of the Paleoproterozoic Aravalli Supergroup, Northwestern India, to constrain the time of major thermal events. The Aravalli paleosols (sericite schists) have witnessed a complex history of metamorphism and metasomatism. The LA-ICP-MS U-Pb ages of zircons from the two paleosol samples are 2586 ± 45 Ma and 2793 ± 21 Ma, similar to the zircon ages for the parent Ahar River Granite. Five paleosol samples define an Rb-Sr isochron age of 1394 ± 22 Ma with (87Sr/86Sr)i of 0.7493 ± 0.0034 (2σ) and an MSWD of 3.9, pointing to the timing of the latest alkali metasomatism affecting the paleosols. The whole-rock K-Ar ages of sericite-rich paleosol samples range from 940 ± 30 to 873 ± 25 Ma, corresponding with the emplacement of Erinpura Granite. Thus, the Aravalli paleosol recorded more than two billion years of thermal events in its multi-geochronometers. The correlation between Rb-Sr isotope compositions and REE contents in paleosol samples suggests the REE mobility during K-metasomatism.

Geochemical and geological characteristics indicate the wolframite mineralization for seeking the type of wolframite mine in Vau village and ajacent area (Dong Giang district, Quang Nam province)

Wolfram mineralization in the area of Vau village (Dong Giang district, Quang Nam province) is distributed along the small stream together with other sulfide mineralizations in the form of small to large boulders. Ore minerals are mainly sheelite, pyrhotite, arsenopyrite a little of chalcopyrite and pyrite. The ore is distributed in stockwork type in the gray, light gray metamorphic sedimentary rocks with quartz - mica composition alternated with quartz feldspar mica schist, sericite schist and sericitized schist of the A Vuong formation (Sequene 3). Sheelite exists in the area manifested by hornflization and bezeritization. Ajacent area have weak skarnation. They have manifestations of the wolframite deposit of skarn type. Geochemical characteristics: W in the ore reaches 2,323 ppm (0.023%), As - 110,366 ppm (1.10%), Co - 212.3 ppm, related granite (Ba Na block’s granite) reaching 1,517 ppm wofram situated at the edge of the magma block (fine-grained alaskite, similar to the composition of boulders in the ore strip). There is small-grained granite with a content of 794 ppm at the center of mass. Thus, the two granite types have high level of metallogical specialization of wolframite (Ktt = 397 is fine-grained granite and Ktt = 758.7 is alaskite Granite). Besides, this rock has metallogical specialization of As (277.4 ppm in fine-grained granite, 29.9 ppm in alaskite).

In Situ Needle Penetration Test and Its Application in a Sericite Schist Railway Tunnel, Southwest of China

AbstractThe sericite schist is a typical metamorphic soft rock. Large deformation of surrounding rock often occurs in the construction of a tunnel in this stratum. Due to the broken rock mass structure and poor mechanical strength in Baishitou tunnel project of Dalin line of Southwest railway, it is impossible to prepare standard samples for a traditional rock mechanical test. Therefore, we chose penetrometer (SH-70) for an in situ test. Firstly, we monitored the deformation of typical sections and analyzed the characteristics of large deformation of soft rock in the tunnel. Secondly, we tested the needle penetration index of fresh excavation face and side wall. Then, we estimated some mechanical parameters of sericite schist by a needle penetrometer and Hoek-brown criterion and discussed the acquisition of mechanical parameters of soft rock. The results show the following: (1) the characteristics of extrusion rock tunnel are summarized as large deformation, fast deformation rate, and obvious construction disturbance. (2) The reference value of penetration index of sericite schist (the vertical joint direction) is 3.90~7.77 N/mm, and the parallel joint direction is 1.27~2.99 N/mm. (3) The uniaxial compressive strength estimated by a penetrometer is 0.78~8.53 MPa, and the strength of the surrounding rock is negatively correlated with the amount of deformation. Therefore, it can be considered that the insufficient strength of surrounding rock is the fundamental reason for large deformation. (4) The reference value of cohesion of sericite schist estimated by a penetrometer is 0.203 MPa, and the reference value of internal friction angle is 18.224°. Compared with the common estimation methods, the penetrometer is more convenient and economical, which can provide a new idea for obtaining the mechanical parameters of sericite schist soft rock tunnel.

Comparative assessment of slope stability in weathered schists using Q-slope and LEM

The slope stability in weathered schists formations has always been of great importance for studies in rock mechanics. The majority of the methods used in the geotechnical practise for estimating the slope stability are based on the traditional limit equilibrium methods, analysing the possibilities of circular and non-circular failures. On the other side, very few empirical methods exist for assessment of the slope stability. Q-slope is a relatively new methodology for the assessment of slope stability in terrains built from rock masses. This method was developed over the last decade by Barton and Bar (2015, 2017), with modification of the original Q-system and it is based on the results of more than 500 case studies all over the world in reinforcement-free slopes. This paper presents results of the slope stability assessment with the limit equilibrium and Q-slope method at four characteristic cut sections with unusual general heights (ranging from 30 m to 92 m), along the route of the A2 motorway, section Kicevo-Ohrid in the Republic of N. Macedonia, which is under construction. The subject cuts presented in this paper were excavated in the period 2014 – 2018 without the application of special measures for protection. The research area is built mainly from phyllite, sericite schists, quartz-sericite schists and graphitic schists, which are folded, tectonically disturbed and affected by the process of degradation. According to the results of the analyses, it can be emphasised that both limit equilibrium method and Q-slope are applicable at terrains built from weathered and tectonically disturbed schists because the stability conditions on site were confirmed with these two methodologically different approaches. As a general conclusion, we can summarize that the best way to assess the slope stability condition is when we combine different tools and methodologies, especially when we face highly variable rock mass conditions.

Stability evaluation of cut slopes in highly weathered schists using limit equilibrium, kinematical and empirical methods

1. Extended abstractThe traditional limit equilibrium method and the kinematic analyses are the first choices in the geotechnical practice for the assessment of the slope stability of a particular rock slope. The reason is that very few empirical methods exist for this purpose.This paper presents results of the slope stability assessment with limit equilibrium, kinematical and empirical methods for over 50 deep cut slopes in highly weathered schists along the A2 motorway section Kicevo-Ohrid in RN Macedonia. The research area is mainly composed of phyllite, sericite schists, quartz-sericite schists and graphitic schists. These rocks are highly weathered, tectonically disturbed and often folded, which means they are prone to local deformations, especially in aspects of the long-term impact of atmospheric influences and the existence of unfavourable joint sets. Although most of the failures that occurred had local character, on several cut slopes global failure occurred. The slope stability assessment of the subject rock formations is a difficult challenge because the highly weathered phyllite and schists are difficult to be characterised, considering the uncertainties associated with the material anisotropy and the network of discontinuities.This study employs different failure mechanisms of cut slope stability in complex geological media. The rock masses were modelled according to the generalized Hoek-Brown criterion while the joints behaviour was modelled using the Barton-Bandis shear strength criterion. Rocscience software package was used for executing the limit equilibrium analyses and the stability analyses along discontinuities. The relatively new and intuitive empirical method Q-slope was applied for the stability assessment of the excavated rock slopes.According to the results and the findings, it can be emphasized that although the limit equilibrium analyses showed relatively stable slopes, significant failures on several cut slopes occurred on site. The stability conditions on site were confirmed with the kinematical analyses and the Q-slope method.The final decision of the slope geometry should be made after the inspection of the excavated surfaces because it is very difficult to register the discontinuity conditions before the construction phase starts. The best way to assess the stability condition is with a combination of different tools and methodologies, especially when we face highly weathered rock formations.The next step of this research will be to propose a methodology, where the long-term rock slope stability and the associated level of risk will be evaluated using graphical diagrams.

Study on creep characteristics of residual soil in Central Yunnan Water Diversion Project

Sericite schist is an extremely soft rock. Most of the sericite schist residual soil in nature is in an unsaturated state, The matrix suction of the residual soil has a great influence on its strength. In this paper, an unsaturated quadruple consolidation tester and an unsaturated triaxial creep tester are used to carry out one-dimensional and three-axis creep tests on sericite schist residual soil. The test results show that the creep characteristics of the soil sample are obvious. Both the one-dimensional and triaxial tests show obvious three-stage characteristics. At the same time, the influence of the matrix suction and the net vertical stress on the creep characteristics of the soil is comparatively analyzed.

Experimental analysis on dynamic characteristics of unsaturated sericite schist residual soil controlled by different factors

Taking sericite schist residual soil widely distributed along Dalin Railway as the research object, the resonance column test of sericite schist residual soil in unsaturated state was carried out, and the dynamic shear modulus Gd under different water content, dry density and consolidation confining pressure in small strain range (10−6 < γ d < 10−4) was studied. The test results show that water content has a great influence on dynamic shear modulus, followed by dry density and consolidation confining pressure. Gd increases non-linearly with the increase of water cut, and there is a certain critical water cut that makes Gd reach the maximum, and then Gd gradually declines with the increase of water cut; D ∼ γ d curves tend to overlap under high confining pressure and high water content. Under the same dynamic shear strain amplitude, Gd increases with the increase of dry density. Under different consolidation confining pressures, the increasing of Gd follow-up shear strain γd tends to decrease.

Research Progress of Unsaturated Strongly Weathered Sericite Schist Residual Soil

The settlement and deformation of soft rock are the main problems hindering the construction of tunnel engineering. The use of soft rock and its residual soil has become the focus of engineering development at home and abroad. Sericite schist is an extremely soft rock, and most of the sericite schist residual soil in nature is in an unsaturated state. The Baishitou Tunnel of Dali-Lincang Railway is located in Yun County, Lincang City, Yunnan Province. The surrounding rock in the tunnel is mainly soft rock, such as sericite schist and carbonaceous schist. Due to the action of the earthquake, the rock mass is easily broken and its strength is low, making construction extremely difficult. Strongly weathered sericite schist has the characteristics of soft rock, easy to weather, and the rock mass is relatively easy to break. Its residual soil has similar properties to its parent rock and is often encountered in actual engineering. The research on unsaturated strongly weathered sericite schist and its residual soil has become the focus of research by scholars at home and abroad. The engineering properties of unsaturated soils have become one of the main research directions of soil mechanics.

Study on Dynamic Characteristics of Unsaturated Strongly Weathered Sericite Schist Residual Soil

Sericite schist residual soils are widely distributed on the shallow surface of western Yunnan, and most of them are in an unsaturated state. In order to study its dynamic characteristics, a resonance column tester was used to target the strongly weathered unsaturated sericite schist residuals in the Dali Railway. The soil carries out dynamic characteristic test to study. The results show that the confining pressure has a great influence on the dynamic characteristics of the specimen, the dynamic shear modulus increases with the increase of the confining pressure, the phenomenon that the damping ratio decreases with the increase of shear strain is more obvious. Using the Hardin-Drnevich model can better fit the dynamic shear modulus with shear strain. The application of the improved linear equation can better describe the relationship and analyse its mechanism.

Geochemistry of the Neoproterozoic Mbondo-Ngazi Tina Metasediments, Adamawa Area, Central Cameroon: Source Provenance and Tectonic Setting

The Mbondo-Ngazi Tina area belongs to the Adamawa-Yade domain within the Pan-African Central Africa Fold Belt in Cameroon (CAFB). The basement of this area is dominated by metasedimentary rocks composed of sericite schist, chlorite schist and muscovite schist. Whole-rock geochemical compositions of these rocks were investigated in order to determine their provenance and tectonic setting. The studied metasedimentary rocks have SiO2 and Al2O3 contents comparable to the average composition of the Neoproterozoic upper continental crust (UCC). These rocks are strongly depleted in CaO, MgO, and enriched in K2O, Ba and Rb with respect to UCC, reflecting K addition during diagenesis. The CIA, CIW, PIA and the SiO2/Al2O3 and Th/U ratios indicated that these rocks had suffered varying degrees of weathering as the source rocks underwent mild to moderate chemical weathering. The PAAS-normalized REE patterns are almost flat with slightly LREE depletion with respect to HREE and null to weakly positive Eu anomalies. Their chondrite-normalized REE patterns are parallel to sub-parallel, LREE-enriched, and display distinct negative Eu anomalies and weakly fractionated HREE segments. Overall, they are geochemically mature and have suffered sedimentary recycling. They derived mainy from felsic to intermediate rocks with minor contamination of mafic rocks. The Mbondo-Ngazi Tina metasedimentary rocks show REE and trace element compositions similar to those of Archean sediments, suggesting that the continental crust of the study area during the early Proterozoic had chemical compositions similar to those of the Archean crust and were probably deposited in active to passive continental margin settings.

Study on creep characteristics of unsaturated sericite schist residual soils

Sericite schist is an extremely soft rock, which is characterized by obvious rheological properties and large creep deformation. The residual soil of Sericite schist is in unsaturated state for most of the time. When encountering water, it interacts with water, which has a great influence on its strength. In this paper, one dimension and three axis creep tests of Sericite schist residual soil are carried out by using unsaturated quadruple consolidation apparatus and unsaturated triaxial creep apparatus. The results show that the creep process of the residual soil can be divided into three stages: rapid growth stage, slow growth stage and stable stage. The creep deformation of triaxial test is larger than that of one dimension.

Study on soil-water characteristics of unsaturated sericite schist residual soils

The residual soil of Sericite schist softens and becomes loose when encountering water, which is easy to be damaged by wetting. Its engineering properties are obviously affected by water, so it is necessary to study its soil water characteristics. In this paper, the matric suction of Sericite schist residual soil under different dry density is measured by filter paper method. It is found that the change of soil water characteristic curve of Sericite climbing residual soil is not typical “s”, and there is no obvious unsaturated residual section. The main reason is that the residual soil of Sericite schist has sheet structure, easy drainage channel and fast water loss speed, the change of matrix suction is large. Because of its lamellar structure, its water holding capacity is poor, so the unsaturated residual section of its soil water characteristic curve has no obvious change.

Fitocenološke i edafske karakteristike acidofilne šume bukve sa mahovinama (Musco - Fagetum moesiacae B. Jov. 1976) na Jelovoj gori

The aim of this research to show floristic and ecological characteristics of acidophilus beach forest with mosses (Musco - Fagetum moesiacae B. Jov. 1976) in the area of Jelova gora. The studied type of soil in this forest community was dystric cambisol, which finds on sericite schist. Only ten plant species was recorded in this plant community (eight vascular plants and two species of mosses - Polytrichum commune and Leucobryum glaucum), so we can conclude that this plant community is very floristic poor. On bases floristic structure, spectrum of life forms and ekological spectrum are done. The phanerophytes have the highest share in community. The results of the study showed that investigated forest community was mesophilic, acidophilic to neutrofilic, mesotrophic, sciophilic to sub-sciophilic and mesothermophilic.

Structural control of mass movements on slopes formed of magmatic and metamorphic rocks: the case study of Wielisławka Mt. (SW Poland, Sudetes Mts.)

We indicate the structural controls on, and provide an evolutionary model of, mass movements which developed on the slopes of a rhyolitic lava dome built of massive, sub-intrusive Permian rhyolites and its low-grade metamorphic cover, comprising Ordovician and Silurian sericite schists and metacherts (greenschist facies). The phenomena studied occur on the low-altitude, dome-like Wielislawka Mt. (370 m a.s.l.) in the Western Sudetes, SW Poland. A multidisciplinary approach involving geological and geomorphological fieldwork, LiDAR-based geomorphometric analyses, as well as analyses based on data obtained from terrestrial laser scanning (TLS), performed within old adits and shafts in the landslide area, have allowed determination of the origin and recent extent of the landslide phenomena. The geometry and development of the slip surface are closely linked with measured, existing discontinuities within the massif. As they enable observation of the initial stages of mass movement in the excavations within the cover rocks of the rhyolitic massif, the old adits and shafts are unique objects for the observation and reconstruction of landslide processes.

Rare Elements—Markers of the Formation Setting of Manganese and Iron Ore Deposits in the Kalahari and Postmasburg Fields (South Africa): Communication 1. Kalahari Manganese Field

Manganese ores of the Lower Proterozoic Hotazel Formation (Transvaal Supergroup) associated with the banded Fe-silicites are marked by high concentrations of several rare elements (B, Ge, W, Mo, Cr, Ni, Zn, Cd, Pb, Ag, Bi, As, Sb, Te, Se). High boron contents in the oxide‒carbonate ores (Mn-lutites) are attributed to the chemosorptional concentration of this element on Mn-carbonates. Owing to hydrothermal transformations, a wide range of the ore-forming (mainly Fe and Mn) and rare elements (REE included) was removed from the underlying hyaloclastic basaltic andesites of the Ongeluk Formation. Manganese ores and Fe-silicites are characterized by the typical values of the cerium (Ce/Ce* 0.28–1.72) and europium (Eu/Eu* 0.57–16.31) anomalies that can suggest that primary sediments were deposited in a marginal shallow-marine basin with a prominent oxic surficial water layer and subanoxic conditions near the floor. At different stages of lithogenesis, metalliferous (Mn, Fe) sediments of the shallow-water basin were enriched in Eu (positive Eu/Eu*) and subjected to metasomatism (with the redistribution of Mn and the formation of manganese carbonates) and the consequent regional metamorphism (up to the stage of green sericite schists).

Metasediments in the Alahina Sector and Associated Mineralization (North-Eastern Guinea)

The Alahina sector is located in the North-East of Guinea, precisely in the Siguiri volcano-sedimentary basin. It consists mainly of meta-sediments traversed by Paleoproterozoic pyroclastite, granite, monzogranite and granodiorite veins as well as Mesozoic dolerite and gabbros veins. This article presents new data, on the one hand, on the geochemical petrographic features and the origin of the metasediments of this zone, and on the other hand, on the genetic model of the gold mineralization that they contain. Field observations, as well as petrographic and geochemical studies reveal that the meta-sediments consist of sericite and chlorite schists. They belong to the groups of shales and grauwackes. Their protholites are moderately altered (60 N/YbN = 6.31 - 13.24) and a flat heavy rare earth patterns (HREE). This spectrum is almost identical to those of the “Post-Archean average Australian Shale” and Early Proterozoic Greywackes. Two types of polyphase gold mineralization occur in the Alahina sector: disseminated and veined. They consist of particular of grains and nanoparticles pyrite associated with gold, magnetite, hematite, ilmenite. The hydrothermal alteration accompanying this mineralization consists of silica, microcline, chlorite-epidote-sericite-carbonates.

Tectono-magmatic events and genesis of Fe-Pb-Zn resources in Nefza area, NW Tunisia

Fe-ore and Pb-Zn (Ag) resources of Nefza region occur within hydrothermally altered sericite-schists and breccias, with Neogene molasse and lacustrine sediments and with a sequence of tertiary granodiorite-rhyodacite and basalts. Intrusions of intermediate igneous rocks, whose correlate with the successive Alpine tectonic events, started at 15 Ma and continued to near 5 Ma. Four main stages of mineralization are identified: (1) the first stage started during or soon after the maximum alpine compression (Langhian-Lower Serravallian) and magmatism. Silicification and carbonatization prevailed and sericite-bearing sediments formed by K-sericite alteration. (2) During the second stage, a mixture of marine and meteoric ore-forming fluids (H2O, H2CO3, F and Cl; temperature range, 315–500 °C) has deposited mineralizations. The sericite schist assemblages and breccias were extremely altered and four types of minerals were formed: (i) silica, feldspar, Mg-micas, chlorite-vermiculite, Mg-clays, and kaolinite-halloysite; (ii) fluorite and sorbed U; (iii) Fe-(Mn) oxyhydroxides; (iv) Zn, Pb, Mn, and Fe, deposited in the carbonates, in coronadite and in minor sulfides. (3) The third stage was related to the extensional tectonic phase (Upper Serravallian-Lower Tortonian) and leads to the subsidence of Miocene grabens and deposition of molasse with interbeded pyroclastites. The strata-bound iron ores were reworked from pre-existing Fe-mineralization hosted in folded structures. (4) During the fourth stage (8 to 5 Ma), magmatic activity changed from calc-alkaline granitoid to alkaline basalt. This correlates with a moderate Atlasic compression, thrust faulting, and Miocene graben folding. During this stage, Pb (Ag)-Zn sulfides were deposited in veins that cut across the predating iron deposits, with neoformed Mg-rich clays and carbonates (calcite, siderite, ankerite) with noticeable Zn and Mn enrichments.