Podrobnosti záznamu

Název
    Tin-polymetallic sulfide deposits in the eastern part of the Dachang tin field (South China) and the role of black shales in their origin
Údaj o odpovědnosti
    Jan Pašava, Bohdan Kříbek, Petr Dobeš, Ivan Vavřín, Karel Žák, Fan Delian, Zhang Tao, Marie-Christine Boiron
Autor
    Boiron, Marie-Christine
    Delian, Fan
    Dobeš, Petr
    Kříbek, Bohdan, 1946-
    Pašava, Jan
    Tao, Zhang
    Vavřín, Ivan
    Žák, Karel, 1957-
Jazyk
    anglicky
Zdrojový dokument - seriál
    Mineralium Deposita
Svazek/č.
    Vol. 38, no. 1
Strany
    p. 39-66
Rok
    2003
Poznámky
    16 obr., 4 fot., 9 tab., 2 s. bibl.
    il.
    Zkr. název ser.: Mineralium Depos. (Berlin).
Předmětová skupina
    břidlice černá
    devon
    geneze ložiska
    grafitizace
    inkluze fluidní
    izotopy C
    izotopy O
    izotopy S
    izotopy stabilní
    karbonáty
    kasiterit
    ložisko typu stratabound
    organická substance
    podmínky P-T
    rudy barevných kovů
    rudy Sn
    sulfidy
    žíla rudní
Geografické jméno
    Čína jižní
    Dachang (Čína jižní)
Klíčové slovo
    Black
    China
    Dachang
    Deposits
    Eastern
    Field
    Origin
    Role
    Shales
    South
    Sulfide
    Tin
    Tin-polymetallic
Abstrakt (anglicky)
   The Dafulou and Huile vein and stratabound cassiterite-sulfide deposits and sheeted ore veins at the Kangma cassiterite-sulfide deposit are located in the eastern part of the Dachang tin field. These deposits are hosted in a sedimentary sequence containing significant concentrations of organic matter in the form of Lower Devonian calcareous black shales and hornfels. These rocks together with the younger intrusion of Longxianggai granite (91+-2 Ma) actively participated in the formation of Sn-polymetallic deposits. The following three major stages have been distinguished in stratiform and vein-type orebodies at Dafulou, Huile and Kangma: stage I (cassiterite, pyrrhotite, arsenopyrite, tourmaline, carbonate), stage II - main sulfide stage (quartz, cassiterite, arsenopyrite, pyrrhotite, sphalerite, stannite, pyrite, carbonates) and stage III (native Bi, galena, electrum, sulfosalts). Stage IV (post-ore), recognized at Huile is represented by barren carbonates and zeolites.
   Whole rock geochemistry has revealed that at Dafulou, Bi and Cu correlate strongly with S, whereas V and Pb correlate well with Corg (organic carbon). The similar distribution patterns of selected elements in average slightly mineralized low-Ca black shales indicate a fluid composition similar for all deposits studied. Studies of graphitization of the organic matter in black shales adjacent to orebodies indicate that d(002) and FWHM (full width in half maximum)/peak height values gradually decrease in the following sequence: Dafulou deposit ŕ Kangma deposit ŕ Huile deposit. The pyrolysate of wall rocks at the Dafulou deposit is relatively enriched in asphaltenes and maltenes (55.6-72.0 per cent of the pyrolysate) comparable with pyrolysate obtained from more distal black shales (19.2-28.5 per cent). Typical GC-MS spectra of pyrolysate from distal black shales are dominated by alkanes in the n-C15 to n-C25 range, aromatic molecules being represented mostly by alkyl-naphthalenes.
   In contrast, only traces of aliphatic hydrocarbons in the n-C14 to n-C18 range and elemental sulfur were identified in pyrolysates from pyrrhotitized wall rocks. The earliest fluid inclusions of the studied system occur in the quartz-tourmaline-cassiterite assemblage of stage I at Dafulou. These inclusions are H2O-CO2-CH4-rich, with 10 to 20 vol per cent of aqueous phase. P-T conditions of the trapping of inclusions are estimated to be up to 400 °C and 1.3 to 2.0 kbar (between 5.0 and 7.5 km under lithostatic pressure). In contrast, the presence of a low density gaseous CO2-CH4 phase indicates relatively low pressures during the formation of the breccia-type quartz-calcite-cassiterite-sulfide mineralization (stage II), when P-T conditions probably reached approx. 380 to 400 °C and 0.6 kbar (up to 6 km under hydrostatic pressure).
   Fluid inclusion data and oxygen isotope thermometry indicate that cassiterite-sulfide ores of the main sulfide stage (stage II) formed from aqueouscarbonic fluid
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    31. 8. 2007
Datum importu
    8. 8. 2012