MINING GEOLOGY, 32 (3), 273•`280,1982

講 演

The Metallogeny of *

Mauris BESSON*

Sweden but they occur, on the other side 1. Introduction and comparisons of the Atlantic, from the Ungava Bay to Two main geodynamic phenomena account Manitoba. for the present geology of Western Europe: France also does not show any of the huge (a) The NS and SN collision of the Gondwana anorthosite complexes with associated titanium and Laurasia protocontinenets responsible for oxyde mineralizations typical of the Middle the Cadomian orogenesis, and (b) The EW and Upper Proterozoic which occur in the opening of the Atlantic Ocean beginning in Grenville and the southern part of Norway. the Upper Proterozoic with the opening of the However, pre-Caledonian geodynamic recon- lapetus. structions suggest a more spatial proximity of In connection with the above major tectonic the Bou-Azzer (Morocco) arsenic deposit with events, the following orogeneses may be the deposits of the Cobalt (Ontario) district recognized in Europe: showing sililar parageneses. Cadomian 700-550 Ma The NNE-SSW trending Caledonian oro- Caledonian 540-420 Ma genic belt has been cut from Southern Ireland Hercynian 350-300 Ma and Germany by successive tectonic phases. Alpine 100-0 Ma Remnants, although . displaced, of the Caledo- As each of these orogeneses left its marks, nian orogenesis occur in France i.e., the Europe and France in particular is a continent where the Lower Paleozoic terrains of heterogeneous frameworks resulting from are correlated with those of the Hispanic and the mentionned successive tectonic events. Moroccan blocks. Local Caledonian rocks However the above marks appear to be ir- there do not show as important massive sulfide regular: France is characterized by a lack of deposits as those of the Caledonides of Norway. (1) large Proterozoic masses typical of NE Lastly, the Alpine orogenesis, are attributed Europe and bordering the Archean terrains of the emplacements of ultrabasic rocks of the the Kola peninsula, and (2) associated nickel Pyrenees and . But the important chromite sulphide mineralizations occurring in thick deposits typical of the Eastern Mediterranean, sills within ultrabasic rocks. These mineraliza- Albania, Yugoslavia, Greece and Turkey are tions in Europe are only found in Finland and unknown in the Western Mediterranean area.

Received on December 7, 1981. 2. The main structural subdivisions * Presented at the 30th Anniversary of the Society of Four main structural provinces are recog- Mining Geologists of Japan held in Tokyo on January 30, 1981 (This extended abstract is based on the nized in France: (a) a platform wholly built

publications of the 26th CGI and mainly based on in the Hercynian (the Gallic rigid block) the work by A. AUTRAN, J. BouLDON, P. LAFFITTE, cropping out over 400,000 km2 out of the A. ZISERMAN in colloque C7, Evolutions Geologiques 550,000 km2 of France. It includes both the de la France: "A-Les Bites Mineraux", memoire de old massives and the epicontinental sedimen- BRGM, n•K 107). ** Ecole Nationale des Mines tary basins, (b) the border land of the above , 60 Boulevard Saint- Michel, 75272 Paris, Cedex 06, France. block deformed by the Alpine orogenesis, (c)

273 274 Mauris BESSON MINING GEOLOGY: the Alpine s.s. structural zone, and (d) the alizations are known within the Upper Alpine structural zone of the Pyrenees. Georgian limestones (La Loubatiere) or the black shales from the uppermost Georgian 3. The Icartian basement (2000 Ma old) (Brusque and St Salvy). At Saint Salvy this This has few outcrops and is devoid of stratabound sphalerite mineralizations is cut known mineralizations. by the Saint Salvy vein of Upper Carboniferous age. Reserves of Zn, Pb and Ag are evaluated 4. The Brioverian (Upper Proterozoic) at 300,000 metric tons of metal. This is mostly present in the Armorican . Lower Brioverian (600 to 700 Ma) 6. Ore deposits of Ordovician, Silurian includes basic volcanics, pillowed spilites and and Lower Devonian age tuffs and keratophyric tuffs with some strata- In the Ordovician and with the important bound sulfide mineralizations (e.g. Tremuson Arenig (Armorican sandstone) transgression, in black cherts and euxinic shales). Upper a new geological cycle starts. Littoral con- Brioverian (640 to 540 Ma) shows some centrations of rutile and zircon occur in the volcanic sequences. The Rouez massive sulfide uppermost Arenig sandstones. These rocks may deposit, recently (1976) discovered by air- contain 8 to 15% of rutile+zircon over 2 to transported geophysics, is evaluated at 100 3m of thickness. Upper Ordovician and million metric tons of pyrite with low Zn , Cu, Lower Devonian are characterized by a Pb, and Ag values. tholeiitic or talc-alkaline volcanism related to Caledonian deformations and locally to massive 5. The Cambrian sulfide mineralizations. In the Armorican This occurs in neritic facies in the , a more developed Lower Devonian Massif and Montagne Noire. Between these volcanism produced the Porte-aux-Moines mas- areas metamorphism of basic and acidic volcan- sive sulfide (2.5 million metric tons at 10%Pb+ ics gave the "leptyno-amphibolic group" . In Zn+Cu) deposit underlying acidic tuffs fol- the northern neritic area, Sn and W minerali- lowing spilites. The Bodennec deposit in black zations with fluorite gangue (Montbelleux) or shales and tuffites contains 300kt metal and Cu, Mo, Pb and Zn mineralizations (Beauvain) 300t Ag; rick ore shows 20 to 30% of Pb+ are related to Lower Cambrian leucogranites Zn+Cu and 200g Ag/t. In the Pyrenees, and granitic porphyries. In the neritic area of locally strata-bound massive sulfide mineraliza- the Montagne Noire, stratabound Zn miner- tion appear in the Upper Ordovician (Pierrefi- tte, Sentein, Pale de Rose, Arrens) and in the Lower Devonian (Hospice de France, Carboire) the associated lavas are spilites and keratopyres but tuffs are more important and Sentein is in a peri-reefal setting. At Pierrefitte, 200 kt of ore belong to the vein mineralization while the strata-bound shows 2 million metric tons at 10%Zn+Pb. The Carboire deposit has 2 million tons of ore at 6%Zn and 1% Pb . Oolithic iron ore occurs along with the Arenig transgression in Anjou and Normandy . In the Manche the iron formation is Lower Devonian. Oolithic ore from Normandy is of siderite enriched to 45% after roasting. Three mines are presently working and the most

Fig.1 Les grandes regions structurales de la France . important, Soumont produces 1 million tons Structuctural divisions in France. per year. 32 (3), 1982 The Metallogeny of France 275

Fig. 2 Devonien et carbonifere. Devonian and caboniferous

conformably during Dinantian time, are 7. Ore deposits of Upper Devonian and associated with tholeiitic and calc-alkaline Lower Visean age spilites and keratophyres. In the "arverno- To the west of the , the orogenic phase vosgienne zone" the Brevenne series contains of Middle Devonian age (360 to 340Ma) con- the massive sulfide Sain Bel (20 million metric stitutes the main early phase of the Hercynian tons of pyrite) and Chessy deposits. The orogenesis. In the Upper Devonian, the Chizeuil deposit occurs within the albite sediments of the zone "arverno-vosgienne" porphyrites of Morvan. In the "arverno- laying unconformably on older rocks but vosgeenne" and the Central Armorican zones 276 Mauris BESSON MINING GEOLOGY: and during Lower. Visean (350Ma) granites granite and granodiorite emplacements, the were emplaced. Local mineralizations (Saint latter locally associated with an important Renan) appear to be related with Upper volcanism. These two granite families clearly Carboniferous leucogranites; the same age are geochemically discriminated. would possibly apply to uraniferous granites Aluminousleucogranites of Bois Noir and Morvan. The most important groups of these leu- cogranites were emplaced in Brittany and in 8. The Variscan metallogeny of granite the northern Massif Cental between 345 and from the Upper Visean to Stephanian 320Ma. In the Armorican Massif, they occur The period from Upper Visean to Step- with a cassiterite-beryl mineralization (Le hanian is characterized by a strong magmatic Villeder, Abbaretz). In the activity resulting in leucogranite or monsonitic they are present in the Millevache and Marche

Fig.3 Metallogenie associee aux granites Westphaliens. Metallogeny related to Westphalian granitoids. 32 (3), 1982 The Metallogeny of France 277

Fig.4 Gites diuranium francais lies aux granites. Uranium deposits in granites. 278 Mauris BESSON MINING GEOLOGY:

area associated with uranium and locally 4 lead and zinc mines are active, each one tungsten and tin mineralizations. The uranium mining a deposit of different genesis. The deposits of Limousin (Margnac, La Crouzille) Saint Salvy veins were emplaced during the and Vendee (L'Escarpiere), in which the last phase of formation of the neighbour- primary disseminated uraninite mineralization ing granitic stock of Sidobre, during the has been concentrated in vein fractures during Stephanian. But, these Carboniferous veins cut the Permian, should also be mentionned. Cambrian stratabound horinzons. The proved A sencond group of leucogranites (approx. reserves of the deposit are 300 Mt of metals 300Ma) sparsely crops out over the whole Zn, Pb and Ag. Hercynian belt and again is associated with The gold field of Salsigne already yielded 70 U, Sn or W mineralizations: Uranium at tons of gold. The reserves are nearly of the same Cellier and Pierres Plantees in the Grandrieu importance. In this district, the mineralizations Leucogranite; Montmins, Montebras, En- are of the high-temperature hydrothermal guiales and Leucamp tungsten deposits. type. Gold is found with arsenic, copper, Monzoniticgranites tungsten and bismuth in veins, wallrocks They also, may be classified in two groups: impregnations and stratabound offsets in (a) In the Central Massif and the Vosges, Paleozoic terrains, dating from Cambrian to subvolcanic plutons are associated with mon- Devonian. Several hundreds of meters of zonitic granites of the Upper Visean (330Ma) biotite halos spread themselves along the and are at the origin of high temperature fractures and cut the nappes forming the mineralizations with molybdenite and chal- general structure. copyrite. (b) The group of granodiorites Several roughly stratabound orebodies, often emplaced during the Westphalian (300 Ma) is genetically related with metasomatic processes, known all over the Hercynian chain. are approximately of the same age: Scheelite-bearing skarns lie at the contact fluorite and siderite at Escaro of some of the monzonitic granite and grano- magnesite at Montner diorites (Costabonne, Salau, Montrebon, Coat talc near Luzenac. an Noz). The Salau deposit is mined presently At the hanging wall of the talc deposit of and bears 1,000 metric tons WO3, in the ore Trimouns are Ordovician shales and dolomites: grading 1.5%WO3. at the footwall are migmatites and pegmatites. The deposit yields around 300 kt of talc a year. 9. Variscian and late Variscian hydro- thermal mineralizations 10. Stephanian and Permian deposits In this group are the late Vriscian veins, Small grabens were produced by distension's whose genetic relation with magmatism is not tectonic phenomena after the main phases of the certain. Many of them, originated in a rather Hercynian orogeny. Stephanian and Permian cool basement before the Stephanian, in the sediments were laid down in these grabens. Armorican massif and the Central Massif . For Stratabound uranium deposits occur in Step- example, the group of veins, La Lucette , hanian sediments in the Aveyron (Brousse- antimony-bearing yielded 42,000 t of antimony Broquies) and in the Vosges. Also during the and 8 tons of gold, between 1905 and 1939 . Permian epoch, reconcentrations of pitchblende In this group of veins emplaced in cool rocks , in many intragranitic veins occured along the the lead zinc deposits of the Armorican massif topographical surface existing at that time. may be classified. Pontpean, for example , Altogether, the output of uranium in France is yielded 220 kt of lead and 20 kt of zinc. One about 2,400 tons of uranium metal a year may mention that there are about 2000 and the reserves may be some 100,000 metric noticeable lead and zinc showings in France , tons of uranium metal, for a cost of 130 $ per and among these, about one hundred deposits kg of uranium or 50 $ per pound of U3O8. of variable size, have been mined. Nowadays, 32 (3), 1982 The Metallogeny of France 279

Fig.5 Filons et stratiformes a Pb, Zn, F, Ba. Veins and stratabound Pb, Zn, F, Ba deposits.

in Triassic and Liassic sediments. For instance, 11. Trias and Dogger deposits La Plagne orebody, hosted by Triassic quartz- Triassic sediments, essentially grits and ites at the border of the Belledone massif yielded sandstones but locally also lagoon dolomites, 60kt of metals, lead and a bit of silver. The are host rocks for many lead deposits in most important of those districts is the "Sous- France, but also all around the Western Cevenol" one. There, mineralizations were Mediterranean area. Argentiferous lead with emplaced a short time after sedimentation, the zinc, barite and fluorite occur in the first ore-bearing horizons lying at the proximity of transgressive horizons on the border of the old an area where lagoon type sedimentation oc- basement; such concentrations are found both curred with gypsum, dolomites and cargneules. 280 Mauris BESSON MINING GEOLOGY

They were close to the sea shores at the time The huge oolithic iron deposit of Lorraine of transgression. lies at the top of the Toarcien sediments. For the whole district, past production plus several seams, a few meters in thickness, have reserves amount to: been mined for many years by underground 800,000 tons of lead workings. The mines are highly mechanized 1,250,000 tons of zinc with excellent output per man, per shaft. The 1,600 tons of silver ore is not very rich but, due to its lime content, One may distinguish: (a) the principal is self melting in the blast furnace. Therefore, lead-bearing deposits in the Lower Triassic the iron and steel industry in Lorraine is of sandstones and arkoses: Saint Sebastien great inportance, the output for the whole area D'Aigrefeuille and mainly Largentiere with being about 30 million tons a year. 10 million tons of ore grading,3 .8%Pb, 0.75%Zn and 80 g/ton Ag. (b) the principal 12. Deposits in the Cretaceous and zinc-bearing deposits in calcareous sediments, Cenozoic horizons for example La Croix de Pailleres and mainly During Cretaceous time, one episode of Les Malines. Les Malines: sphalerite, galena emersion involved a large area termed the "isthmus of Durance" and barytite mineralizations occur from Trias- . The continental altera- sic conglomerates until Bothonian horizons . tion formed bauxite deposis, as the result of The deposit yielded until the present day resedimentation of aluminous alterites. The 700kt of metal, and daily output of the mine deposits spread over 400 km, from the south of is 1000 tons of ore grading 6%Zn and 1%Pb . Toulouse to the Esterel massif. They from part Around the Morvan, seven suboutcropping of a large bauxite bearing province, extending fluorite deposits were recently discovered: for from Spain to Turkey. The footwall is mainly instance Pierre-Perthuis and Pontaubert . They a lower Cretaceous limestone, for example in occu along the border line between basins the areas of Bedarieux, Les Baux and Brignoles . and continent in the Trias, Hettangian and The resources of the district were 100 millions Sinemurian formations. The proved reserves of tons, 80 millions of tons being mined are 16 million tons of fluorite grading 32-40% already. During Oligocene time, evaporites CaF2. In the same manner, barytite occurs in occured in the subsident rift zone of Alsace as the lowermost horizons of the Hettangian at a result of tectonic faulting. The output of Chaillac and Pessens, and occurs as veins at potash deposits in Alsace is about 1.9 millions Les Farges. of tons a year of K2O.