température de formation

CONT: II est [...] impossible [...] d'avoir de l'information sur la température de formation de ces veines minéralisées. Les températures calculées nous démontrent que l'intrusion porphyrique à été métamorphisée au faciès préhnite-pumpellyite supérieur à schiste vert inférieur.

CONT: In his PhD thesis, J.W.G. Gilbey (1968) cited a maximum formational temperature for the gold-lodes of 535°C at a pressure of 2.4 kbar. These figures were based on the upper stability limit for co-existing pyrite and arsenopyrite (temperature) and a burial depth approaching 10 km (pressure). ... More recently, three new temperature estimates for the gold-lodes have been produced, based on fluid inclusions, sulphur isotope exchange and mineral stability data ... These data all point to formational temperatures for the lodes of around 300°C, with an estimated pressure of 1.8 kbar. These figures would seem to be much more reasonable.