Remote Sensing Studies of Alteration Zones in Dahaneh Qaleh Exploration Prospect, Northwestern Bardeskan

Dahaneh Qaleh exploration prospect is located about 300 km southwest of Mashhad and 50 km northwest of Bardeskan. The exploration prospect is also a part of Taknar massive sulfide mineralization zone and lithology of the area consists of chlorite sericite schist, biotite sericite schist and sericite schist with metamorphosed basic and intermediate igneous rocks in the type range meta-gabbro diorite to meta-diorite that they belong to Taknar Formation.Taknar Formation was intrusived by low grade metamorphosed intermediate subvolcanic intrusive rocks with porphyry texture in the type range of meta-hornblende-quartz monzonite porphyry, meta-hornblende-quartz monzodiorite porphyry, meta-hornblende monzodiorite porphyry, meta-quartz monzonite porphyry and meta-hornblende-quartz monzosyenite porphyry. All of the geological unites are affected by moderate to severe alteration and sulfide minerals including pyrite, were transformed to secondary iron oxides due to oxidation. Before the field investigation, ETM and ASTER sensors data were processed with "color composition of band ratios", "standard and ive principal component analysis" methods and finally "spectral angle mapping" as a successful method for more accurate separation of altered minerals that introduced Hematitic, Chloritic, Epidotic, Sericitic and Silicification alteration zones in the study area. Accuracy of the processes were proved by the following field, petrography and mineralography studies.