| Popis: |
Fluid inclusions from the epigenetic Zn-Cu deposit of Kipushi, central African copper belt, Katanga, Democratic Republic of Congo, have been subjected to an integrated microthermometric, bulk crush-leach and laser ablation inductively coupled plasma mass spectrometric (LA-ICP-MS) study to elucidate the physicochemical conditions of ore formation and the origin of the mineralizing fluids. The Kipushi deposit is hosted in carbonates and partly in siliciclastic rocks that have undergone regional, low-grade greenschist facies metamorphism and which were strongly deformed during the Lufilian orogeny (main deformation phase ~550 Ma). Investigation of host-rock, gangue, and ore samples enabled reconstruction of the paragenesis of ore deposition. The main Zn-Cu (+Ge, Pb) sulfide mineralization was accompanied by three generations of hydrothermal dolomite and a generation of coarse-grained quartz. Primary and pseudosecondary fluid inclusions in these minerals contain predominantly halite-saturated, aqueous brines (~30–43 wt % NaCl equiv), with locally unidentified trapped solids. These inclusions mostly decrepitate upon heating before total homogenization, which could suggest that they also trapped excess carbonic vapor. They show petrographic and microthermometric evidence for postentrapment reequilibration, prohibiting their use as accurate geothermometers and geobarometers. Previous studies on chlorite and sphalerite geothermometry framed the formation temperature of the Kipushi Cu-Zn deposit between ~290° to 380°C. Younger fluids are present as secondary inclusions in the gangue minerals and as primary fluid inclusions in sphalerite from a minor secondary mineralization phase. These two-phase aqueous inclusions have a slightly lower salinity (~23–31 wt % NaCl equiv) and have homogenization temperatures ranging from ~170° to |
