NJG73-4-02
1993
Conditions of metamorphism estimated from alteration lithologies and ore at the Bleikvassli Zn-Pb-(Cu) deposit,Nordland, Norway
73
4
pp. 226-233

Electron probe microanalyses of silicate and sulphide phases within ores, of microcline gneiss, garnet-biotite schist and other characteristic alteration assemblages associated with the Bleikvassli Zn-Pb-(Cu) massive sulphide orebody were carried out. Using established geothermobarometric methods, peak metamorphic conditions for the portion of the Rødingsfjell Nappe Complex hosting the orebody are estimated. Most methods employed indicate peak conditions in the range 540-570°C and 7.5-8.5 kbar. Only a single metamorphic episode is recorded in the rocks studied here. Geothermometric calibrations based on compositions of garnet-chlorite pairs give temperature conditions of approx. 510-520 C, suggesting temperatures on the retrograde cooling path. Estimates of peak and retrograde metamorphism are consistent with observed mineralogical and textural evidence recorded in the rocks.

N. J. Cook, Mineralogisches lnstitut der Universität Wiirzburg, Am Hubland, 97074 Wiirzburg, Germany.

0029-196X