عنوان مقاله [English]
نویسنده [English]چکیده [English]
The Anarg Polymetallic skarn deposit ( Cu, Zn, Fe, Ag, Au) is located on the15 km west of the Posht-e- Badam village in the northeastern part of the Yazd province in central part of Iran. This area is situated in geological domain of the central Iran within the Anarak - Sarcheshmeh - Kharestan copper belt]. The Anarg's granitoid intruded within the center of north - south trending zone . The K/Ar radioisotope age of this granitoid body is middle Eocene, respectively. Lithologically of this granitoid body is composed of I- type granite, granodiorite, quartzmonzonite and less of tonalite and quartzdiorite. There is one calcic type skarn around this intrusion. The most
تاریخ دریافت مقاله: 6/12/1380 تاریخ پذیرش مقاله: 2/5/1381 email:email@example.com *
important country rock is calcic marble, related to the Posht -e- Badam complex. The exoskarn mainly consists of garnet ( andradite- grossularite), clino - pyroxen (diopside - hedenbergite ), amphibole ( tremolite - actinolite), epidote, chlorite, calcite, quartz, magnetite, chalcopyrite, galena and sphalerite, where its high grade metamorphic facies is attained to the primer pyroxen - hornfels facies. The endoskarn minerals assemblage is composed of grassularite, andradite, epidote, chlorite, calcite, tremolite, actinolite, which its thickness is varied between 1-3 meters. The ore minerals occurred in three different localities (anomalies) namely A,B and C. The major part of economic ores are located within the exoskarn zone. This paragenesis not only is related to the composition of hosting, but also reflects the evolutionary processes of intrusion emplacement. The magmatic derived solutions resulted from fractional - crystalization of igneous melt, as well as their interaction with surrounding rock units participates to from the aforesaid polymetallic skarn - type deposit, by metasomatic processes. Skarnification in the Anarg ore field has been occurred in three stages namely:I) , Prograde, II). Retrograde - Metasomatic and III) Hydrothermal stages. The major ore mineralization has occurred during 2 nd stage. This deposit is a lenticular form body, accompanied by irregular massives and less amount of vein and veinlets. Their ores show massive, inclusion, disseminated and less amount replacement type textures. By considering the mineralogical peculiarities and their correlation with phase diagrams, it is concluded that the temprature of the mineral zone formations are as follows:
- Pyroxen zone , 450 -600 0C
- Garnet zone , 380 -480 0C
This skarn was formed by contact- infiltration of magmatic derived fluids. This processe has been intensified by fracturing systems of both magmatic and surrounding bodies. Mineralogical investigation ( X.R.D and ore microscopy) show that the major ore minerals are chalcophyrite, magnetite, galena and sphalerite. The Cu-content is varied between 0.35 to 12% , which indicates a remarkable deposit for mining consideration. It has to be mentioned that this deposit is classified as polymetallic - skarn type deposit, by considering the ( Cu, Zn, Fe, Ag, Au,) metals in ore fomation, which is related to the continental margin - type low angle subducted zone .