Petrology and temperature determination of skarn formation in Dezg area, southwestern of Hajiabad, north of Birjand

چکیده مقاله

The study area is located in north of Dezq village in southwestern of Hagiabad. Mineralogical and geochemical investigations is showing two main stage of prograde and retrograde metamorphism in formation of skarn in study area. In prograde stage, has formed skarn with anhydrous silicate- calcium mineral assemblage (andradite – grossular and diopside-hedenbergite) in temperature range of 328° to 599° which has similar composition with garnets from Cu- Fe and Au skarns. . In retrograde stage,a part of these anhydrous silicates are affected by retrograde metamorphism and changed to hydrous and anhydrous silicate minerals with less calcium(epidote, tremolite-actinolite) and finally hydrous and anhydrous calcium assemblage has altered to fine grain minerals including chlorite, calcite, quartz and clay minerals in temperature range of less than 300°. The presence of intergrowth texture and absence of replacement texture in andradite and pyroxene, is showing that these minerals are formed as contemporaneous. This mineral assmbelage has crystallized in high partial water pressure which is between 0.8 to 0.9 whole pressure. High partial water pressure has been certainly result of water fluid seepage from granitic body to country rock.