Naslov
Geochronology and geothermometry in the Ljubija siderite deposit, NW Bosnia, a precursor of the early intra-continental rifting of the Tethys

Autori
Palinkaš, Ladislav ; Balogh, Kadosa ; Šiftar, Dubravko ; Prochaska, Walter ; Strmić, Sabina

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

Izvornik
Anuarul Institutului Geologic al Romaniei / Udubasa, S. - Bukurešt : Geological Institute of Romania, 2000

Skup
The 4th Symposium Baia Mare Branch of the Geological Society of Romania

Mjesto i datum
Baia Mare, Rumunjska, 16.11.2000. - 18.11.2000

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Dinarides; Ljubija; siderite-barite-polysulfide deposits

Sažetak
There is a long lasting dispute on time and way of formation of siderite-barite-polysulfide (ąCu, Pb, Zn, F) deposits of Internal Dinarides, placed within upper Paleozoic sedimentary sequences: Foča, Central Bosnia, Ljubija, Trgovska gora, Petrova gora, Rude-Samoborska gora and Bistra. In principle, there have been two possible alternatives, Hercynian or Alpine metallogeny, ranging from middle Carboniferous to middle Triassic time. There has also been a wide spectrum of genetical models applied in their genesis as well, from pure sedimentary, volcano-exhalative, metasomatic, vein-hydrothermal, remobilized or combination of these. Recent geochemical, isotopic and microthermometric measurements on Ljubija parageneses brought some new data, which confirm hydrothermal origin, and Permo-triassic time of mineralization. Short review of recent investigation results Microthermometry on quartz from ore deposits of different morphology constrained genetical model. The deposit was formed during intracontinental rifting, which generated thermal disturbance, and gave rise to deep open fractures and initiation of hydrothermal cells. Chemical character of the fluids was NaCl, CaCl2 primarily, with wide range of salinity from a few % NaCl wt.equ. to more than 30 %. Influence of terrestrial waters is recognized by presence of sulfate and carbonate ions and free CO2 (clathrates). Th varies from 100 to 250 oC. Ore body Žune, originates from the two phase region of the hydrothermal convective cell and Ljubija from its lower margin. The depth of formation determined on a basis of PTX parameters of boiling fluids is between 200 to 500 m, depending on whether lithostatic or hydrostatic pressure has been applied. Lead isotopes in galenas, using Doe-Stacey, and Stacey-Kramer models of lead growth curves, gave ages of 239 and 232 Ma. On the other hand the value of 206Pb/204Pb and 207Pb/204Pb fall far bellow μ values of the typical Hercinian granite related ore deposits within Pannonian realm. Sulfur isotope data from barite are also indicative. The values δ34S from 8.5-14.5 point out to influence of the Permian sea sulphate, or Permian evaporates. Ionic chromatograpy maybe solves the dilemma, since Cl/Br and Na/Br ratios show trend appropriating to the composition of lagoon brines. K/Ar dating of illite-smectatite from the Carboniferous slates, host rocks of siderite veins and metasomatic bodies, was based on presumption that their crystal structure suffered badly during Cretaceous and Tertiary metamorphic events, loosing Ar in uncontrolled amount. The slate, incorporated within siderite veins as an xenolite, and protected from strain and stress, however, preserved Ar developed after cooling of siderite veins. The closure-temperature of illite-smectite minerals is close to 250 oC. It means that cooling age can be accepted as the time of mineralization. The values from Carboniferous slate vary widely between 130 to 290 Ma, but the xenolithic slate gave very close values of 236 and 238 Ma. Conclusion.The age of mineralization is still not confirmed definitely, as well as the age of many Permo-Triassic formations in the Dinarides, usually lacking fossils. The Permo-Triassic siderite-barite deposits along the margin of the Mesozoic carbonate platform demarcate opening of the Tethys. Demarcation line may be followed to Rudabanya (NW Hungary), or Erzberg in Northern Calcareous Alps.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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