2009
The Rozna uranium deposit (Bohemian Massif, Czech Republic): shear zone-hosted, late Variscan and post-Variscan hydrothermal mineralization
KŘIBEK, Bohdan, Karel ŽÁK, Petr DOBEŠ, Jaromír LEICHMANN, Marta PUDILOVÁ et. al.Základní údaje
Originální název
The Rozna uranium deposit (Bohemian Massif, Czech Republic): shear zone-hosted, late Variscan and post-Variscan hydrothermal mineralization
Název česky
Uranové ložisko Rožná (český masiv, Česká republika) pozdně variská a povariská hydrotermální mineralizace
Autoři
KŘIBEK, Bohdan (203 Česká republika), Karel ŽÁK (203 Česká republika), Petr DOBEŠ (203 Česká republika), Jaromír LEICHMANN (203 Česká republika, garant), Marta PUDILOVÁ (203 Česká republika) a Miloš RENÉ (203 Česká republika)
Vydání
Mineralium Deposita, SPRINGER, 233 SPRING ST, NEW YORK, NY 10, SPRINGER, 233 SPRING ST, NEW YORK, NY 10, 2009, 0026-4598
Další údaje
Jazyk
angličtina
Typ výsledku
Článek v odborném periodiku
Obor
10500 1.5. Earth and related environmental sciences
Stát vydavatele
Spojené státy
Utajení
není předmětem státního či obchodního tajemství
Impakt faktor
Impact factor: 1.520
Kód RIV
RIV/00216224:14310/09:00035962
Organizační jednotka
Přírodovědecká fakulta
UT WoS
000261692000007
Klíčová slova anglicky
Uranium; Bohemian Massif; Rozna; Czech Republic
Štítky
Příznaky
Mezinárodní význam, Recenzováno
Změněno: 24. 6. 2009 11:56, prof. RNDr. Jaromír Leichmann, Dr. rer. nat.
V originále
Three major mineralization events are recorded at the Ro angstrom 3/4na uranium deposit (total mine production of 23,000 t U, average grade of 0.24% U): (1) pre-uranium quartz-sulfide and carbonate-sulfide mineralization, (2) uranium, and (3) post-uranium quartz-carbonate-sulfide mineralization. (1) K-Ar ages for white mica from wall rock alteration of the pre-uranium mineralization style range from 304.5 +/- 5.8 to 307.6 +/- 6.0 Ma coinciding with the post-orogenic exhumation of the Moldanubian orogenic root and retrograde-metamorphic equilibration of the high-grade metamorphic host rocks. The fluid inclusion record consists of low-salinity aqueous inclusions, together with H2O-CO2-CH4, CO2-CH4, and pure CH4 inclusions. The fluid inclusion, paragenetic, and isotope data suggest that the pre-uranium mineralization formed from a reduced low-salinity aqueous fluid at temperatures close to 300A degrees C. (2) The uraniferous hydrothermal event is subdivided into the pre-ore, ore, and post-ore substages. K-Ar ages of pre-ore authigenic K-feldspar range from 296.3 A +/- 7.5 to 281.0 A +/- 5.4 Ma and coincide with the transcurrent reorganization of crustal blocks of the Bohemian Massif and with Late Stephanian to Early Permian rifting. Massive hematitization, albitization, and desilicification of the pre-ore altered rocks indicate an influx of oxidized basinal fluids to the crystalline rocks of the Moldanubian domain. The wide range of salinities of fluid inclusions is interpreted as a result of the large-scale mixing of basinal brines with meteoric water. The cationic composition of these fluids indicates extensive interaction with crystalline rocks. Chlorite thermometry yielded temperatures of 260A degrees C to 310A degrees C. During this substage, uranium was probably leached from the Moldanubian crystalline rocks. The hydrothermal alteration of the ore substage followed, or partly overlapped in time, the pre-ore substage alteration. K-Ar ages of illite from ore substage alteration range from 277.2 A +/- 5.5 to 264.0 A +/- 4.3 Ma and roughly correspond with the results of chemical U-Pb dating of authigenic monazite (268 A +/- 50 Ma). The uranium ore deposition was accompanied by large-scale decomposition of biotite and pre-ore chlorite to Fe-rich illite and iron hydrooxides. Therefore, it is proposed that the deposition of uranium ore was mostly in response to the reduction of the ore-bearing fluid by interaction with ferrous iron-bearing silicates (biotite and pre-ore chlorite). The Th data on primary, mostly aqueous, inclusions trapped in carbonates of the ore substage range between 152A degrees C and 174A degrees C and total salinity ranges over a relatively wide interval of 3.1 to 23.1 wt% NaCl eq. Gradual reduction of the fluid system during the post-ore substage is manifested by the appearance of a new generation of authigenic chlorite and pyrite. Chlorite thermometry yielded temperatures of 150A degrees C to 170A degrees C. Solid bitumens that post-date uranium mineralization indicate radiolytic polymerization of gaseous and liquid hydrocarbons and their derivatives. The origin of the organic compounds can be related to the diagenetic and catagenetic transformation of organic matter in Upper Stephanian and Permian sediments. (3) K-Ar ages on illite from post-uranium quartz-carbonate-sulfide mineralization range from 233.7 A +/- 4.7 to 227.5 A +/- 4.
Česky
Three major mineralization events are recorded at the Ro angstrom 3/4na uranium deposit (total mine production of 23,000 t U, average grade of 0.24% U): (1) pre-uranium quartz-sulfide and carbonate-sulfide mineralization, (2) uranium, and (3) post-uranium quartz-carbonate-sulfide mineralization. (1) K-Ar ages for white mica from wall rock alteration of the pre-uranium mineralization style range from 304.5 +/- 5.8 to 307.6 +/- 6.0 Ma coinciding with the post-orogenic exhumation of the Moldanubian orogenic root and retrograde-metamorphic equilibration of the high-grade metamorphic host rocks. The fluid inclusion record consists of low-salinity aqueous inclusions, together with H2O-CO2-CH4, CO2-CH4, and pure CH4 inclusions. The fluid inclusion, paragenetic, and isotope data suggest that the pre-uranium mineralization formed from a reduced low-salinity aqueous fluid at temperatures close to 300A degrees C. (2) The uraniferous hydrothermal event is subdivided into the pre-ore, ore, and post-ore substages. K-Ar ages of pre-ore authigenic K-feldspar range from 296.3 A +/- 7.5 to 281.0 A +/- 5.4 Ma and coincide with the transcurrent reorganization of crustal blocks of the Bohemian Massif and with Late Stephanian to Early Permian rifting. Massive hematitization, albitization, and desilicification of the pre-ore altered rocks indicate an influx of oxidized basinal fluids to the crystalline rocks of the Moldanubian domain. The wide range of salinities of fluid inclusions is interpreted as a result of the large-scale mixing of basinal brines with meteoric water. The cationic composition of these fluids indicates extensive interaction with crystalline rocks. Chlorite thermometry yielded temperatures of 260A degrees C to 310A degrees C. During this substage, uranium was probably leached from the Moldanubian crystalline rocks. The hydrothermal alteration of the ore substage followed, or partly overlapped in time, the pre-ore substage alteration. K-Ar ages of illite from ore substage alteration range from 277.2 A +/- 5.5 to 264.0 A +/- 4.3 Ma and roughly correspond with the results of chemical U-Pb dating of authigenic monazite (268 A +/- 50 Ma). The uranium ore deposition was accompanied by large-scale decomposition of biotite and pre-ore chlorite to Fe-rich illite and iron hydrooxides. Therefore, it is proposed that the deposition of uranium ore was mostly in response to the reduction of the ore-bearing fluid by interaction with ferrous iron-bearing silicates (biotite and pre-ore chlorite). The Th data on primary, mostly aqueous, inclusions trapped in carbonates of the ore substage range between 152A degrees C and 174A degrees C and total salinity ranges over a relatively wide interval of 3.1 to 23.1 wt% NaCl eq. Gradual reduction of the fluid system during the post-ore substage is manifested by the appearance of a new generation of authigenic chlorite and pyrite. Chlorite thermometry yielded temperatures of 150A degrees C to 170A degrees C. Solid bitumens that post-date uranium mineralization indicate radiolytic polymerization of gaseous and liquid hydrocarbons and their derivatives. The origin of the organic compounds can be related to the diagenetic and catagenetic transformation of organic matter in Upper Stephanian and Permian sediments. (3) K-Ar ages on illite from post-uranium quartz-carbonate-sulfide mineralization range from 233.7 A +/- 4.7 to 227.5 A +/- 4.
Návaznosti
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