Exploration & Mining Geology, Vol. 6, No. 3, 1997
To evaluate geochemical aspects of sheared zones, 35 samples of granitoid
rocks from an area of shearing >5 km2 at Derehamzeh, Iran were studied
geochemically. Relatively unaltered samples within the shear-zone area average
38 ppm Cu, 1.45 ppm Mo, 4.6 ppb Au, 0.21 ppm Ag, <1 ppm Re, 46 ppm Zn, 28.5
ppm Pb, and 0.34% S. Bleached, hydrothermally-altered samples are anomalous in
Cu (>896 ppm), Au(>59.5 ppb), Ag(>24.4 ppm), Re(>1.28 ppm), Zn
(>164 ppm), Pb (>218 ppm), and S(>0.9%). Some samples from bleached
sheared zones that are highly anomalous in Cu (5000 ppm), Mo(23 ppm), Ag(74
ppm), and Au(200 ppb) are characterized by a typical sericitic alteration
assemblage consisting of sericite, pyrite, chalcopyrite, and granular quartz.
The main anomalous zone extends over about 0.4 km2 in the southern part of the
area. The strong Cu-Mo-Au-Ag association in the sericitic shear zones suggests a
possible relationship to porphyry copper mineralization, similar to that found
in northern Chile. Further studies on drill-core samples in the southern
sericitized shear zones are required to determine if more extensive
porphyry-type sulfide mineralization is present.
