Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence

Figure 7

Isocon diagram comparing the chemical composition of the least altered granite and the Panasqueira greisen. Granite composition is an average of 5 analyses. Oxide analyses are in wt% and trace elements in ppm; values are scaled with the factors indicated for each element. The best fit isocon (blue line) defined from P₂O₅, Al₂O₃, MnO, and Fe₂O₃ is compatible with an immobile alumina during the greisen alteration. This best fit is characterized by a slope of 1.12 corresponding to a volume decrease of about 12.4%. For comparison, an isocon based on hypotheses of constant mass (black line) and constant volume (dashed line) is also plotted.