Naslov
Mineral deposits related to geotectonic units of the Dinarides

Autori
Palinkaš, Ladislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Geološke vijesti / Tomljenović, Bruno ; Balen, Dražen ; Saftić, Bruno - Zagreb : Hrvatsko geološko društvo, 2000, 145-147

Skup
PANCARDI

Mjesto i datum
Dubrovnik, Hrvatska, 01.10.2000. - 03.10.2000

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Mineral deposits; Dinarides; global tectonics

Sažetak
Geological evolution Numerous mineral deposits of various metallic and nonmetallic mineral raw materials are known in the Dinarides and mined from prehistoric, Illirian, Greek, Roman and medieval time (Slaves and Saxonians) to the present days. Different genetic and paragenetic types spread along Dinaridic orogenic belt within all geotectonic units. The genesis of the majority of deposits is comfortably attributed to geological events of Alpine Wilson cycle primarily. Hercynian ore deposits, however, are overprinted by alpine deformational events, and there is still enough ambiguity in distinguishing those two metallogenic cycles. The earliest Alpine phases of the evolution of the Dinarides probably started in Late Permian with a rifting episode of app. 40 Ma duration (PAMIĆ and JURKOVIĆ, 1997). The rifting processes took place within the Variscan basement and they were accompanied by bimodal magmatism, which ended in Late Triassic by establishment of the carbonate platform. Afterwards started processes of the opening of the Dinaridic part of the Tethys and formation of an oceanic crust. Carbonate sedimentation proceeded in continuum till Upper Cretaceous, building up a huge carbonate platform. This passive continental margin, accommodates turbidites seaward, gradually passing into shales, mudstones, radiolarites and micrites of an open ocean environment. The pelagic sedimentation was accompanied by basic volcanic activity. The active, destructive continental margin, placed opposite to the former one, is made of graywackes and shales with olistostrome mélange, accompanied with concurrent basic volcanism. Subduction processes started by the end of Late Jurassic, as indicated by ophiolite emplacement, and their exposure to aerial weathering. It caused closure of the Dinaridic part of Tethys and initiation of a magmatic arc along the active continental margin. The trench, in front of the magmatic arc that produced granite plutonism and basalt-rhyolite volcanism, was filled with flysch sediments. Tectonic paroxysm at the end of Late Eocene, is marked by termination of the subduction, implacement of ophiolites, tectonization of the olistostrome mélange, Alpine metamorphism and granite implacement. Southwesterly vergence of the Dinaride folds and thrusts point out to a NE-dipping subduction. Separation of Tethys into Mediterranean and Paratethys (Pannonian basin) is a result of the main Alpine deformational event and rise of the Dinarides in Late Eocen time. The foregoing sequence of events shaped the present day geology and morphology of the Dinarides. In general, there are distinctive geotectonic units, adjacent to one another from SW to NE, which accommodate appropriate mineral deposits: 1. Carbonate platform formations (External Dinarides) 2.Passive continental margin (Jurassic-Cretaceous flysch sequences) 3.Allochtonous Paleozoic and Triassic complexes (Internal Dinarides, probably deeply eroded basement of the passive continental margin) 4.Ophiolite zone (radiolarites, volcanics, ophiolite olistostrome mélange, ophiolites) 5.Active continental margin (Upper Cretaceous-Paleogene flysch, tectonized olistostrome mélange, Alpine medium-pressure metamorphic rocks, Alpine granitoid rocks) 6.Post-orogenic Oligocene and Neogene cover. Mineral deposits Low level of erosion in the Dinarides and the widespread Phanerozoic cover, not older than Lower Paleozoic (at present knowledge) do not allow better insight into pre-Variscan and Variscan metallogeny, characterized by granite intrusion elsewhere in Central Europe. Their best exposure is within the geotectonic unit 3.Allochtonous Paleozoic and Triassic nappes (Internal Dinarides). The most typical are SEDEX hematite-magnetite deposits of Lower Paleozoic age in Eastern and Central Bosnia, and hematite-magnetite banded mineralization within para- and orto-metamorphic rocks of Medvednica Mts. Post-Variscan metallogeny, Carboniferous/Early Permian subduction related, rhyolitic magmatism, already recognized in the adjacent region of the Southern Alps, Eastern Alps and W Carpathians brought about great variety of Ba-F-Pb-Zn-Cu-Fe-As-Sb-W-Ag-Au vein mineralizations. Their representatives in the Dinarides are within Mid-Bosnian Ore Mts. (Hg-tetrahedrite, barite, fluorite, Au-pyrite veins) and deposits along the Sava fault zone in Slovenia (Pb-Zn-Cu-barite veins). Alpine metallogeny, Permo-Scythian intracontinental rifting related deposits. Through the Dinarides Late Permian-Scythian intracontinental rifting, caused by thermal doming and Pangea break off, induced intensive, deep hydrothermal circulation cells. Engagement of brine-derived, heated fluids and leaching of iron from the thick shale sedimentary sequences led to formation of epigenetic, metasomatic siderite deposits. They demarcate opening of the Tethys from Eastern, Central and NW Bosnia (Ljubija), in Central Croatia (Trgovska and Petrova gora Mts.), Rude-Samobor, Bistra and may be followed to Hungary (Rudabanya ), and as siderita and magnesite deposits in Slovakia (Gemerides) and Eastern Alps (Erzberg), (PALINKAŠ, 1988; PROCHASKA, 1997, EBNER ET AL., 2000). Their position is closely linked with the Internal Dinarides. Transition Permian-Triassic marks regional transgression, accompanied with extensive evaporite deposition, primarily at sulfate stage. Lokve barite deposit on the P/T boundary,at the base of the oncoming carbonate platform formation is an early diagenetic, Sabkha type, barite-pyrite deposit. Middle Triassic, advanced rifting related deposits Advanced rifting phase, prior to the opening of the Tethys, is the time of formation of extensive Fe-Mn SEDEX deposits within the space of the Internal Dinarides. The biggest are hematite-siderite deposit Vareš, Veovača, Rupice, Borovica (Pb-Zn), Čevljanovići (Mn), situated in Central Bosnia, and Bužim (Mn) in NW Bosnia. Idrija (Slovenia), Čabar (NW Croatia) and Draževići (Central Bosnia) epigenetic-syngenetic Hg-deposits are a product of Triassic rifting as well. Idrija is a typical Hg-SEDEX deposit with welldeveloped feeder zone that bears large reserves of epigenetic mineralization within Carboniferous, Permian and Lower Triassic strata (DROVENIK ET AL., 1980). Acid, explosive, submarine volcanism produced Kuroko type Pb-Zn deposit Šuplja Stijena in the Internal Dinarides of NW Monte Negro (JANKOVIĆ, 1987). Deeply seated, low temperature, connate brines within the carbonate platform, driven by pressure of the overlying sediment burden, and expelled into favorable sites, precipitated carbonate hosted Pb-Zn mineralizations. A good example are Olovo (Central Bosnia), Svinica, Srb, St.Jacob (Central Croatia), equivalents of Mežica, Bleiberg, Reibl and other carbonate hosted Pb-Zn deposits within Southern and Northern Calcareous Alps. Larger Triassic plutonic bodies incorporate endometamorphic hematite-magnetite skarns and high temperature hydrothermal veins, Radovan, Central Bosnia and the exometamorphic hornfels-garnet skarn and epidot-garnet skarn at Tovarnica, near Jablanica (JURKOVIĆ AND PALINKAŠ, 1996). The carbonate platform includes numerous bauxite deposits, formed during hiatuses by aerial weathering of the carbonate substratum, arranged from Middle Triassic to Miocene time (ŠINKOVEC AND SAKAČ, 1989). Deposits related to Jurassic oceanization and formation of ophiolites are scare. In the ophiolite zone low-quality chromite deposits are found in lherzolites associated with pyroxenites, Duboštica ore deposit (Central Bosnia). Weathering of ophiolites, exposed during collision to subaerial conditions gave rise to commercially valuable Ni-bearing laterites in Cretaceous time, Glavica, Kosovo. Washing out of Ni-bearing lateritic crust into shallow marine depressions in Lower Cretaceous, enabled formation of Ni-bearing, oolitic, low-iron deposit, underlain by ultramafics and overlain by Upper Cretaceous sediments. Large chrysotile-asbestos and talc depsits, formed by granitoid hydrothermal activity, are found in serpentinized lherzolite in N parts of Ophiolite zone, Bosansko Petrovo Selo, and vein magnesite deposit is situated in nearby Konjuh Mt.. Subduction related magmatism in the NW Dinarides (Prosara-Motajica-Cer-Bukulja Zone) of Cretaceous-Paleogene time, with remnants of magmatic arc formations (basalts, rhyolites and minor granite bodies) is almost sterile. Paleogene, syncollisional plutonism (granodiorites, monzogranites, tonalites) and migmatization brought beryl-containing pegmatite-aplites and W-Mo-Sn-sulfide pneumatolitic greisen in N Bosnia and W Serbia. Post-collisional Oligocene-Neogene volcanism, however, is the major source of hydrothermal lead and zinc (+ Sb) deposits in the Dinarides. The Pb-Zn deposits are aligned from Kosovo (Trepča) over western Serbia (Rudnik, Zajača, Stolica) to easternmost Bosnia (Srebrenica). The numbered deposits are just typical representatives of the Dinaridic Pb-Zn metallogenic zone.

Izvorni jezik
Engleski

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Geologija

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