Application of Crosta technique for porphyry copper alteration mapping, using ETM+ data: A case study of Meiduk and SAR Cheshmeh areas, Kerman, Iran  H. Ranjbar Department of Mining Engineering, Shahid Bahonar University of Kerman, Iran, Post box No. 76135-133, Tel and Fax: +98-341-2112764, E-mail: hranjbar64@yahoo.com M. Honarmand, Z. Moezifar Department of Geology, Shahid Bahonar University of Kerman, Iran G. S. Roonwal Department of Geology, Delhi University, Delhi-110007, India, E-mail: gsroonwal@hotmail.com Introduction The study area is located in the southern part of Central Iranian Volcanic belt (Figure 1). This belt has a great potential as far as porphyry copper mineralization is concerned. Meiduk and Sar Cheshmeh porphyry copper deposits are presently mined for Cu, and Mo in the area. The area has a semi-arid type of climate and has a mountainous topography. Vegetation cover is substantially poor in the area.  Figure 1: Sketch map showing the position of the Central Iranian Volcanic Belt and porphyry-type Cu deposits sub parallel to the Zagros Thrust Zone(Shahabpour, 1994) 1- Bahreasman, 2- Takht, 3- Kuhe Panj, 4- Darrehzar, 5- Sar Cheshmeh, 6- Meiduk, 7- Gowde kolvary, 8- Darre Zereshg, 9- South of Ardestan, 10- Sharif Abad, 11- Songun (inset). RGB color composite of bands 741. The vegetation is shown in green color. Most of the known porphyry deposits exhibit a well-developed zonal pattern of mineralization and wallrock alteration that can be defined by broad variations in major oxides and trace element concentrations. These elemental compositions in turn reflect variations in mineralogical composition of the altered zones. Most of the hydrothermal alteration processes produce clay and other silicate minerals (e.g. argillic and phyllic zones). Supergene alteration results in the formation of extensive iron oxide minerals, giving characteristic yellowish or reddish color to the altered rocks. These alteration minerals can be detected by remote sensing techniques (Abrams et al., 1977; Abrams et al., 1984; Buckingham and Sommer, 1983; Elvidge and Lyon, 1984; Amos and Greenbaum, 1989; Drury and Hunt, 1989). Landsat data has been used for number of years in arid and semi-arid environments to locate areas of iron oxides and/or hydrous minerals(Abrams et al., 1983; Kaufman, 1988; Tangestani and Moore, 2001) which might be associated with hydrothermal alteration zones. The host rocks that contain ore deposits of hydrothermal origin always show the result of interaction with the hydrothermal fluids that change the mineral and chemical composition of the rock and cause the deposition of the ore and related hydrothermal minerals(Rutz-Armenta and Prol-Ledesma, 1998).
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